Fermilab, Batavia
Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-76CH03000
Steady growth of luminosity has been demonstrated during the entire Tevatron Run II culminating in a record Tevatron performance. During last two years the major contributions came from improvements in antiproton stacking and cooling as well as from numerous improvements in the Tevatron. The talk will describe these improvements as well as other unexpected problems which were encountered and resolved on the road to this success.
SLAC, Menlo Park, California
Funding: Work supported by US DOE contract DE-AC03-76SF00515.
Second-generation B-Factory proposals are being considered both by KEK in Japan (Super KEKB) and by an INFN Frascati/SLAC/CalTech collaboration in Italy (Super-B). Novel collision schemes like crab waist with crab-sextupoles and also crab cavities are being proposed to mitigate the beam-beam effects of a large crossing angle. The talk will present concepts from both proposals in the context of the experience with the present PEP-II and KEKB B-Factories, which have been successful far beyond the initial performance goals.
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
CERN, Geneva
BINP SB RAS, Novosibirsk
KEK, Ibaraki
University of Pisa and INFN, Pisa
The SuperB project aims at the construction of an asymmetric (4x7 GeV), very high luminosity, B-Factory on the Roma II (Italy) University campus. The luminosity goal of 1036 cm-2 s-1 can be reached with a new collision scheme with large Piwinski angle and the use of “crab” sextupoles. A crab-waist IR has been successfully tested at the DAPHNE Phi-Factory at LNF-Frascati (Italy) in 2008. The crab waist together with very low beta* will allow for operation with relatively low beam currents and reasonable bunch length, comparable to those of PEP-II and KEKB. In the High Energy Ring, two spin rotators permit bringing longitudinally polarized beams into collision at the IP. The lattice has been designed with a very low intrinsic emittance and is quite compact, less than 2 km long. The tight focusing requires a sophisticated Interaction Region with quadrupoles very close to the IP. A Conceptual Design Report was published in March 2007, and beam dynamics and collective effects R&D studies are in progress in order to publish a Technical Design Report by the end of 2010. A status of the design and simulations is presented in this paper.
KEK, Ibaraki
SLAC, Menlo Park, California
It is well known that the beam-beam interaction has a focusing effect and therefore causes a dynamical beating of beta function around the rings. This effect becomes greatly enhanced when a collider, such as KEKB, is operated near half integer. The beating makes it difficult to interpret the measurement of horizontal beam size. We derived two coupled nonlinear equations and solved them analytically to obtain the beam sizes at the interaction points, taking into account of dynamical beta and emittance. It has been demonstrated its effectiveness using actual measured data at the synchrotron light monitors. It is expected that it will be implemented in the control room.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) is a third-generation storage-ring-based x-ray source that has been operating for more than 11 years and is enjoying a long period of stable, reliable operation. While APS is presently providing state-of-the-art performance to its large user community, we must clearly plan for improvements and upgrades to stay at the forefront scientifically. Significant improvements should be possible through upgrades of beamline optics, detectors, and end-station equipment, along with local, evolutionary changes to the storage ring itself. However, major accelerator upgrades are also being investigated. One very promising option that has been the subject of considerable research is the use of an energy recovery linac. In this option, APS would transition from a source based on a stored electron beam to one based on a continuously generated high-brightness electron beam from a linac. Such a source promises dramatically improved brightness and transverse coherence compared to third-generation storage rings, as well as distinctly different temporal properties.
BNL, Upton, Long Island, New York
Funding: This work was supported by Department of Energy contract DE-AC02-98CH10886.
The NSLS-II is an ultra-bright synchrotron light source based upon a storage ring with a 30-cell double-bend-achromat lattice with damping wigglers used to lower the emittance below 1 nm. In this talk we discuss the accelerator physics challenges for the design including: optimization of dynamic aperture; estimation of Touschek lifetime; achievement of required orbit stability; and analysis of ring impedance and collective effects.
RIKEN Nishina Center, Wako
The RIKEN RI Beam Factory (RIBF) is pushing the limits of energy for heavy ion cyclotrons. The first experiment of the RIBF has successfully finished with the discovery of new isotopes 125Pd and 126Pd* in June 2007 with a 345-MeV/nucleon uranium beam. However, the total transmission efficiency was limited to be less than 1%. In addition, a carry-over of oil was found in the refrigerator of the Superconducting Ring Cyclotron (SRC), which was the main accelerator of the RIBF. To solve these problems, we have improved beam monitors, upgraded the oil remover system of the compressor of the liquid helium cryogenic plant at SRC and made a series of acceleration tests. As a result, 0.3 pnA of a 345-MeV/nucleon uranium beam was stably delivered to RIBF users in November 2008 and a 345-MeV/nucleon 48Ca beam with the intensity of 170 pnA was obtained in December 2008. In the PAC09 presentation, we will summarize our operating experience with the SRC and developments of RIBF accelerators in addition to most up-to-date performance of the RIBF accelerator complex.
*T. Ohnishi et al., J. Phys. Soc. Jpn. 77 (2008) 083201
BNL, Upton, Long Island, New York
CERN, Geneva
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and the US LHC Accelerator Research Program (LARP).
In the Relativistic Heavy Ion Collider (RHIC) beams collide in the two interaction points IP6 and IP8. An increase of the bunch intensity above 2·1011 in polarized proton operation appears difficult due to the large beam-beam tune spread generated by the two collisions. A low energy electron beam or electron lens has been proposed to mitigate the head on beam-beam effect. In RHIC such a device could be located near IP10. We summarize multi-particle weak-strong beam-beam simulations of head-on beam-beam compensation with an electron lens. The proton beam's lifetime and emittance are calculated and compared for situations with and without an electron lens. Parameters such as the proton bunch intensity, the electron beam intensity and the betatron phase advances between IP8 and IP10 are scanned in the simulations.
JAEA/ERL, Ibaraki
Energy Recovery Linacs (ERL) have been successfully operated in three high-power FEL facilities, Jefferson Laboratory (JLAB) IR FEL Upgrade, Japan Atomic Energy Agency (JAEA) FEL and Budker Institute of Nuclear Physics (BINP) THz FEL. The ERLs are now considered a promising candidate for uses as high-power FELs, synchrotron radiation sources, electron cooling devices, electron-ion colliders and Compton X/gamma-ray sources. All these applications are based on the excellent feature of the ERL that is simultaneous attainment of multiple beam parameters: small emittance, short bunch duration and high-average current. In order to overcome technological challenges and realize the above future ERL applications, several R&D efforts have been launched in the world. In this paper, we overview the current status of these R&D programs and envision the future of ERLs.
CLASSE, Ithaca, New York
Fermilab, Batavia
Cornell University is planning to build an Energy-Recovery Linac (ERL) X-ray facility. In this ERL design, a 5 GeV superconducting linear accelerator extends the CESR ring which is currently used for the Cornell High Energy Synchrotron Source (CHESS). Here we describe some of the recent developments for this ERL, including linear and nonlinear optics, tracking studies, vacuum system design, gas and intra beam scattering computations, and collimator and radiation shielding calculations based on this optics, undulator developments, optimization of X-ray beams by electron beam manipulation, technical design of ERL cavities and cryomodules, and preparation of the accelerator site.
BNL, Upton, Long Island, New York
Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886
The NSLS-II light source is a proposed 3 GeV storage ring, with the potential for ultra-low emittance*. Despite the reduced emittance goal for the bare lattice, the closed orbit amplification factors are on average >50 in both planes, for random quadrupole alignment errors. The high chromaticity will also require strong sextupoles and the low 3 GeV energy will require large dynamic and momentum aperture to insure adequate lifetime. This will require tight alignment tolerances (~30microns) on the multipole magnets during installation. By specifying tight alignment tolerances of the magnets on the support girders, the random alignment tolerances of the girders in the tunnel can be significantly relaxed. Using beam based alignment to find the golden orbit through the quadrupole centers, the closed orbit offsets in the multipole magnets will then be reduced to essentially the alignment errors of the magnets, restoring much of the DA and lifetime of the bare lattice. Our R&D program to achieve these tight alignment tolerances of the magnets on the girders using a vibrating wire technique**, will be discussed and initial results presented.
*Work presented on behalf of the NSLS-II Design Team, CDR(2006) and CD2(2007).
**A. Jain, et al, International Workshop on Accelerator Alignment, Tsukuba, Japan, Feb.11-15, 2008.
University of Pisa and INFN, Pisa
CERN, Geneva
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
We present an improved design of the focusing elements close to the interaction point of the SuperB accelerator. These magnets have to provide pure quadrupolar fields on each of the two beams to decrease the background rate in the detector which would be produced by the over-bend of the off-energy particles if a dipolar component were present. Very good field quality is also required to preserve the dynamic aperture of the rings. Because of the small separation of the two beams (only few centimeters) and the high gradient required by the SuperB final focus, neither a permanent magnet design nor a multi-layer configuration are viable solutions. A novel design, based on 'helical-type' windings, has therefore been investigated. In this paper we will present the improved magnetic design and its performances evaluated with a three dimensional finite element analysis.
CERN, Geneva
The LHC Early Separation Scheme consists in a four 5-10 Tm dipole scheme (D0s) installed close to the two LHC high luminosity experiments. Its aim, in the framework of LHC Phase II Upgrade, is to improve the luminosity by reducing the crossing angle between the two colliding beams, mitigating and controlling at the same time their parasitic interactions. We investigate a less invasive implementation in the detectors (D0 at 14 from the IP) with respect to those already presented (D0 at 7 m from the IP). The luminosity performances are discussed and a tentative analysis on beam-beam effect impact is given. For the new D0 position, preliminary dipole design and power deposition results are shown.
Fermilab, Batavia
Muons, Inc, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-07ER84825
This paper presents the results of design studies of a high field section of a helical cooling channel proposed for the 6D muon beam cooling. The results include the magnet aperture limitations, the tunability of field components, the field correction, the superconductor choice and the magnet operation margin.
CERN, Geneva
Electron cloud build-up is a major limitation for the operation of the SPS with LHC beam above nominal intensity. These beams are envisaged in the frame of the LHC luminosity upgrade and will be available from the new injectors LPSPL and PS2. A series of studies have been conducted in order to identify possible means to suppress electron multipacting by coating the existing SPS vacuum chambers with thin films of amorphous carbon. After a description of the experimental apparatus installed in the SPS, the results of the tests performed with beam in 2008 will be presented.
BNL, Upton, Long Island, New York
The low energy (35 keV) and medium energy (750 keV) transport lines for (un)polarized H- have been reconfigured to reduce beam losses and the beam emittance out of the 200 MeV Linac. The medium energy line in the original layout was 7 m long, and had ten quadrupoles, two beam choppers, and three bunchers. The bunchers were necessary to keep the beam bunched at the entrance of the Linac. About 35% beam loss occurred, and the emittance growth was several fold. In the new layout, the 750 keV line is only 0.7 m long, with three quads and one buncher. To preserve beam polarization in the 35 keV line, the solenoid in front of the RFQ (35 keV to 750 keV) was replaced with an Einzel lens. To reduce the spin-precession in the LEBT, which may cause the depolarization, a 47.4 degree bend was removed and focusing solenoid in front of RFQ was replaced with an Einzel lens. We will present the experimental result of the upgrade.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An energy recovery linac (ERL) is a potential candidate for an Advanced Photon Source (APS) upgrade at Argonne National Laboratory. A high-DC-voltage photocathode-gun-based electron injector* was previously investigated to meet the ultra-low emittance requirement. Recently the modeling was extended to include a merger using the fully three-dimensional tracking simulation code IMPACT-T. A multiobjective numerical optimization was performed with the goal of delivering a 10-MeV, 19-pC bunch with a normalized transverse emittance less than 0.1 μm at the entrance of the linac. In this paper we show the optimum performance obtained.
*Y.-E. Sun et al., ”Optimization of a DC Injector for an Energy Recovery Linac Upgrade to the Advanced Photon Source”, Proc. of LINAC 2008, TUP100, to be published on http://www.jacow.org.
ANL, Argonne
Illinois Institute of Technology, Chicago, Illinois
Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Future x-ray light sources such as FELs and ERLs impose requirements on emittance and bunch repetition rate that are very demanding on the electron source. Even if perfect compensation of space-charge effects could be attained, the fundamental cathode emission properties determine a lower bound on achievable source emittance. Development of ultra-low-emittance sources is a rapidly evolving area of R&D with exciting new results measured for low bunch charge, but it is very difficult to compare different results and quantify what works. The study of photocathodes, with the goal of optimizing for low emittance, is limited in scope. In this paper, we describe an R&D effort to systematically measure and design the fundamental properties of photocathodes suitable for an FEL or ERL. We plan to apply surface analysis lab techniques to characterize photoemission, and then correlate material properties with emittance. On the theory side, we plan to calculate electron band structure for crystal surfaces, correlate with lattice parameters and work function, and then estimate the transverse momentum using the three-step model. The status and results to date of this effort will be reported.
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The concept of an ultra-low transverse emittance injector operating in CW mode for an XFELO* was discussed at LINAC-08**. Here we will report the design optimization of the injector, which includes a 100 MHz RF-gun with thermionic cathode, an energy filter to produce short bunches (~0.5 nsec), a velocity bunching section, higher harmonic cavities to minimize longitudinal emittance, two bunch compressors and accelerating sections operating at 400 MHz and 1300 MHz to obtain 540 MeV electrons. The proposed design is capable of producing 40 pC bunches with 0.5 psec rms time width and 0.7 MeV rms energy spread. Most significantly, the transverse rms emittance is kept below 0.11 π μm. The longitudinal emittance and bunch time width can be substantially reduced for low-charge bunches of several pC.
*K.-J. Kim, Y. Shvyd’ko, and S. Reiche, Phys. Rev. Lett., 100 244802 (2008).
**P.N. Ostroumov, K.-J. Kim, Ph. Piot, Proceedings of the Linac-2008.
ANL, Argonne
Funding: This work was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Low-frequency normal-conducting photoinjectors have the potential to generate CW beam due to low frequency and relatively low field. They can provide a much higher accelerating field at the cathode than envisioned DC injectors but without the complexity involved in superconducting rf injectors. Low frequency allows a relatively long bunch near the cathode to reduce space-charge effects, which is detrimental for generating demandingly high-brightness beams. However, low frequency means higher bunch charge for a given average current, counteracting the potential benefits of low-frequency rf injectors. Furthermore, significant bunch length reduction in the injectors is often needed, which may degrade transverse brightness. To explore the potential of a normal-conducting injector for the envisioned ERL upgrade of the Advanced Photon Source, we made a preliminary design and searched for a suitable solution using genetic optimization. Simulation results are presented.
BNL, Upton, Long Island, New York
TUB, Beijing
There is a growing interest in optimizing the electron beam for an X-ray Free Electron Laser (FEL) in the low charge (10 to 200 pC) and femto-seconds regimes. We have experimentally demonstrated sub-picosecond high-brightness electron beam for a 40 pC charge with ballistic bunch compression and a reduced laser spot size*. Simulation studies showed the feasibility of generating 10 femto-seconds kilo-ampere electron beam with a 20 pC charge**. This paper reports the progress of experimental demonstration of a femto-seconds kilo-ampere electron beam at the NSLS Source Development Lab (SDL). The femto-seconds kilo-ampere electron beam will be used to drive a self-amplified spontaneous emission (SASE) FEL, and SASE FEL spectra and pulse length will be used to measure the electron beam bunch length. The transverse properties of the electron beam will also be experimentally characterized.
*X.J. Wang, et al, Phys. Rev. E , 54, No.4, R3121 -3124 (1996).
**X.J. Wang and X.Y. Chang, Nuclear Instruments and Methods in Physics Research A 507, 310–313 (2003)
DESY Zeuthen, Zeuthen
DESY, Hamburg
MBI, Berlin
BESSY GmbH, Berlin
The Photo Injector Test facility at DESY, Zeuthen site, (PITZ*) aims to develop and optimize electron sources for frontiers linac based FELs such as FLASH and the European XFEL. A new laser system has been commissioned at PITZ in autumn 2008. It is capable to deliver laser pulses with challenging temporal shape: a flat-top profile with ~20 ps FWHM and rise and fall times of ≤2 ps. This laser system, being a significant step towards the European XFEL photo injector specifications, has been used in a 1.6-cell L-band rf gun with ~60MV/m electric field at the cathode to produce high brightness electron beams. A major part of the PITZ measurement program is the optimizing of the transverse phase space. Recent electron beam measurements at PITZ will be presented.
*for the PITZ team
Diamond, Oxfordshire
For the successful operation of an X-ray free electron laser the injector must be robust and able to provide a high quality beam. In this paper we present the design of a normal conducting L-band photoinjector which is based on the successful DESY/PITZ gun, but with improved cavity geometry. The result of beam dynamics simulations predicts that a beam with a normalized transverse emittance of less than 0.7 mm mrad at 1 nC can be produced. With an expected repetition rate of at least 1 kHz this gun meets the requirements of the first stage injector for the UK's New Light Source project.
CERN, Geneva
LAL, Orsay
INFN/LNF, Frascati (Roma)
Installation of the new photo-injector for the CTF3 drive beam (PHIN) has been completed on a stand-alone test bench. The photo-injector operates with a 2.5 cell RF gun at 3 GHz, using a Cs2Te photocathode illuminated by a UV laser beam. The test bench is equipped with different beam monitoring devices as well as a 90-degree spectrometer. A grid of 200 micrometer wide slits can be inserted for emittance measurements. The laser used to trigger the photo-emission process is a Nd:YLF system consisting of an oscillator and a preamplifier operating at 1.5 GHz and two powerful amplifier stages. The infrared radiation produced is frequency quadrupled in two stages to obtain the UV. A Pockels cell allows adjusting the length of the pulse train between 50 nanoseconds and 50 microseconds. The nominal train length for CTF3 is 1.272 microseconds (1908 bunches). The first electron beam in PHIN was produced in November 2008. In this paper, results concerning the operation of the laser system and measurements performed to characterize the electron beam are presented.
CERN, Geneva
National Technical University of Athens, Zografou
IN2P3 IPNL, Villeurbanne
HU/AdSM, Higashi-Hiroshima
KEK, Ibaraki
LAL, Orsay
BNL, Upton, Long Island, New York
The Compton positron source of a future linear collider must obtain the target bunch population by accumulating a large number of positron packets, arriving either in a number of bursts from a “Compton ring”, with intermediate damping of the scattering electron beam, or quasi-continually from a “Compton energy recovery linac”. We present simulation results for the longitudinal stacking of Compton positrons in the ILC damping ring and the CLIC pre-damping ring, reporting parameter optimization, stacking efficiency, possible further improvements, and outstanding questions.
Sokendai, Ibaraki
KEK, Ibaraki
RISE, Tokyo
Kyoto University, Kyoto
At Accelerator Test Facility (ATF), we have developed and successfully used RF Photocathode gun as the source of electrons. We have also used a similar gun in the Laser Undulator Compact X-ray source facility (LUCX), KEK (High Energy Accelerator Research Organization) for performing experiments to generate X-rays by inverse Compton scattering. Both the existing guns have mode separation of 4 MHz. We designed a new RF Gun with high mode separation of around 9 MHz and high Q value to achieve a low emittance beam of good quality. We are also modifying the power delivery scheme to the accelerator at LUCX to achieve the acceleration of 200 nC in 100 bunches with low emittance. This will help to increase the intensity of X-rays by the inverse Compton scattering.
KEK, Ibaraki
JAEA/ERL, Ibaraki
The compact ERL, cERL, is a project to test an energy recovery linac (ERL) with 60 MeV and 100 mA electron beam to generate synchrotron radiation with smaller emittance and shorter pulse length. The design work of the cERL injector has been carried out using a space charge simulation code. The injector consists of 500 kV photo cathode DC gun, two solenoid magnets, buncher cavity, three super conducting RF cavities and merger section to return pass. It generates an electron beam with -77 pC bunch charge and 1.3 GHz repetition rate. Our target value of emittance is less than 1 mm mrad with the bunch length of 1 mm at the exit of the injector. The parameter optimization of the injector using the multi objected method has been carried out to obtain the minimum emittance. The simulation results will be presented in detail.
INFN/LNF, Frascati (Roma)
UCLA, Los Angeles, California
Istituto Nazionale di Fisica Nucleare, Milano
INFN-Roma II, Roma
ENEA C.R. Frascati, Frascati (Roma)
University of Tehran, Tehran
INFN-Roma, Roma
One of the main goals of the SPARC high brightness photoinjector is the experimental demonstration of the emittance compensation process while compressing the beam with the velocity bunching technique, also named RF compressor. For this reason, the first two S-band travelling wave accelerating structures downstream of the RF gun are embedded in a long solenoid, in order to control the space charge induced emittace oscillations during the compression process. An RF deflecting cavity placed at the exit of the third accelerating structure allows bunch length measurements with a resolution of 50 μm. During the current SPARC run a parametric experimental study of the velocity bunching technique has been performed. The beam bunch length and projected emittance have been measured at 120 MeV as a function of the injection phase in the first linac, and for different solenoid field values. In this paper we describe the experimental layout and the results obtained thus far. Comparisons with simulations are also reported.
JAEA/ERL, Ibaraki
KEK, Ibaraki
A 250-kV, 50-mA electron gun has been developed at JAEA for establishing fundamental technologies to generate and evaluate a ultra-small emittance beam, which is required for future ERLs such as a coherent X-ray source and a high-flux gamma-ray source. The gun has been assembled and the first photo-current was obtained from a cathode of NEA-GaAs. Apparatuses for beam measurements has been installed. We plan to measure the transverse emittance by a double-slit configuration and the temporal profile with a deflecting cavity.
LBNL, Berkeley, California
Funding: This work was supported by the Office of Science, U. S. Department of Energy, under Contract No. DE-AC02-05CH11231.
The Advanced Photoinjector Experiment (APEX) seeks to validate the design of a proposed high-brightness, normal conducting RF photoinjector gun and bunching cavity feeding a superconducting RF linac to produce nC-scale electron bunches with sub-micron normalized emittances at MHz-scale repetition rates. The beamline design seeks to optimize the slice-averaged 6D brightness of the beam prior to injection into a high gradient linac for further manipulation and delivery to an FEL undulator. Details of the proposed beamline layout and electron beam dynamics studies are presented.
LBNL, Berkeley, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
A high-brightness high-repetition rate photo-injector based on a normal conducting 187 MHz RF cavity design capable of CW operation is under construction at the Lawrence Berkeley National Laboratory. A cathode field of ~20 MV/m accelerates electron bunches to 750 keV with peak current, energy spread and transverse emittance suitable for FEL and ERL applications. A vacuum load-lock mechanism is included and a 10 picoTorr range vacuum capability allows most types of photocathodes to operate at a MHz repetition rate with present laser technology. The status of the project is presented.
NSRRC, Hsinchu
NTHU, Hsinchu
A high brightness photo-injector for light source research applications is being built at NSRRC. This injector consists of a laser driven RF gun with an emittance compensation solenoid and linac sections that booster the beam energy up to 150 MeV. A 266 nm pico-second UV laser system which generates a 300 uJ laser pulse with pulse which can be varied by a UV stretcher from1 to15 ps have been installed and laser shaping techniques will be developed to reduce the emittance growth. The RF gun is a 1.6 cell cavity operating at pi mode and the solenoid used to compensate the emittance growth due to the space charge effect will be set up in the spring of 2009. Beam dynamics study is performed by PARMELA and simulation results show that a normalized rms transverse emittance of 0.7 mm-mrad with a 10 ps flattop pulse at 1 nC charge can be achieved. Measurements of characteristics of the RF gun and the solenoid will be presented.
NRL, Washington, DC
UMD, College Park, Maryland
LANL, Los Alamos, New Mexico
SAIC, Burlington, Massachusetts
Funding: We gratefully acknowledge funding provided by the Joint Technology Office and the Office of Naval Research
Laser switched photocathodes are now the electron source of choice for short wavelength Free Electron Lasers. The photocathode requirements are profound: ideally, capabilities such as high peak and average current, high quantum efficiency (QE) in the visible, long lifetime in an rf injector and the ability to be repaired in situ are desired. We are pursuing cathodes with self-rejuvenating surfaces based on cesium dispenser cathode technology*,**, in which the physics of recesiation, evaporation, diffusion, and evolution of the surface coating and the QE are the metrics of performance. Here, we present predictive theoretical models of surface evolution and QE in a manner appropriate for inclusion in beam simulation codes, wherein emission non-uniformity and dark current affect emittance, beam halo, and dynamic evolution of bunched electron beams***. The emission models focus on bulk transport issues (including scattering processes) and surface conditions (including diffusion in the presence of random, non-uniform sub-monolayer coverage), and relate these factors to recent experimental characterizations of the surface evolution.
*Jensen, et al., JAP{10}2, 074902 ; Moody, et al., APL90, 114108.
**E. Montgomery, et al., (this conference)
***Petillo, et al., Proc IEEE PAC (2007); Jensen, et al., PRST-AB 11, 081001.
PKU/IHIP, Beijing
High quality electron beam with low transverse emittance in 3.5‐cell DC‐SC photo‐injector is crucial significance for PKU‐ERL‐FEL facility. In this paper, we analyse the emittance evolution in the 3.5‐cell DC‐SC photo‐injector by simply model with consideration of DC acceleration, RF acceleration and space charge effect. The results are compared with Astra simulation. The matching condition of DC‐gun and Superconducting cavity, which is critical for the final emittance at the exit of the injector, is also presented.
BINP SB RAS, Novosibirsk
The projected electron RF gun of Novosibirsk Microtron-Recuperator injector employs an industrial thermionic cathode grid assembly with 0.08 mm gap that usually used in metal-ceramic RF tubes. Three-dimensional (3D)computer simulations have been performed that use the mesh refinement capability of the both Microwave Studio and 2D SAM codes to examine the full region of the real cathode grid assembly in static fields in order to illustrate the beam quality that can result from such a gridded structure. These simulations have been found to reproduce the beam current behaviors versus of applied potentials that are observed experimentally. Based on it ASTRA RF beam simulations also predict a complicated time-dependent response to the waveform applied to the grid during the current turn-on, calculation of the dissipated power by electrons at the grid, and particle tracking downstream of the grid into RF gun cavity and farther on. These simulations may be representative in other sources, such as some L-band RF injectors for industrial applications.
Università di Roma II Tor Vergata, Roma
INFN/LNF, Frascati (Roma)
Rome University La Sapienza, Roma
INFN-Roma II, Roma
ENEA C.R. Frascati, Frascati (Roma)
The SPARC photoinjector drives a SASE FEL to perform several experiments both for the production of high brightness electron beam and for testing new scheme of SASE radiation generation. The control of the beam properties, in particular at the level of the slice dimension, is crucial in order to optimize the FEL process. We report the different measurements performed in order to characterize the slice properties of the electron beam.
UCLA, Los Angeles, California
We report on the use of a ultrashort high brigthness relativistic beam from the UCLA Pegasus laboratory RF photoinjector source for probing matter transformation at the atomic scale with sub-100 fs time resolution. The high accelerating gradient and the relativistic electron energy allow to pack more than 107 electrons in less than 100 fs bunch length, enabling the study of irreversible ultrafast phenomena by single-shot diffraction patterns. The experimental setup, and the initial results from the first ever relativistic electron diffraction time-resolved study will be discussed.
KIT, Karlsruhe
PPT, Dortmund
FZK, Karlsruhe
DELTA, Dortmund
ACCEL, Bergisch Gladbach
Max-Planck Institute for Metal Research, Stuttgart
Funding: This work has been supported by the Initiative and Networking Fund of the Helmholtz Association under contract number VH-NG-320.
The microtron of the ANKA injector is presently equipped with a diode- type electron gun, which produces long pulses. A new thermionic DC triode-type electron gun has been ordered and foreseen for installation in the ANKA injector. The new gun allows single bunch as well as long pulse operation, thus offering the possibility to study beam properties in single bunch operation. This is particularly of interest for the investigation of the short bunch dynamics in the generation of coherent THz radiation. Furthermore, the new gun will make time resolved measurement possible. Simulations of the gun-to-microtron transport with special emphasis on the emittance evolution e.g. due to space charge have been done. Measurements of the gun performance are presently underway and are summarised in this paper.
USTC/NSRL, Hefei, Anhui
A photocathode injector system is developing at NSRL. A BNL type S-band photocathode RF gun has been built. The emittance will be compensated by a Solenoid. The driving laser is a high-Q product. It will be reformed into uniform distribution in the transverse distribution, but will not in the longitudinal direction. The whole system will be tested soon.
Fermilab, Batavia
Extensive work has been done to create an accurate model of beam dynamics at the Fermilab Tevatron. This talk will present validation and results from the development of a simulation of the machine including multiple beam dynamics effects. The essential features of the simulation include a fully 3D strong-strong beam-beam particle-in-cell Poisson solver, interactions among multiple bunches and both head-on and long-range beam-beam collisions, coupled linear optics and helical trajectory consistent with beam orbit measurements, chromaticity and resistive wall impedance. The individual physical processes are validated against measured data where possible, and analytic calculations elsewhere. The simulation result discussion will focus on the effects of increasing beam intensity with single and multiple bunches on the impedance of the beams.
Cockcroft Institute, Warrington, Cheshire
The University of Liverpool, Liverpool
UNM, Albuquerque, New Mexico
SLAC, Menlo Park, California
Microbunching can cause an instability which degrades beam quality. This is a major concern for free electron lasers where very bright electron beams are required. A basic theoretical framework for understanding this instability is the 3D Vlasov-Maxwell system. However, the numerical integration of this system is computationally intensive. Investigations to date have used simplified analytical models or numerical solvers based on simple 1D models. We have developed an accurate and reliable 2D Vlasov-Maxwell solver which we believe improves existing codes. This solver has been successfully tested against the Zeuthen benchmark bunch compressors. Here we apply our self-consistent, parallel solver to study the microbunching instability in the first bunch compressor system of FERMI@Elettra.
BNL, Upton, Long Island, New York
In the past few years, there have been a number of advances in the design and supporting R&D for a machine to cool, accelerate and collide TeV muon beams. This talk will review progress and discuss how such a machine might evolve from programs to build high intensity proton sources and neutrino factories.
CEA, Gif-sur-Yvette
With the aim of producing an intense flux of 14 MeV neutrons, the International Fusion Materials Irradiation Facility (IFMIF) relies on two high power CW accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV to a common lithium target. The Engineering Validation and Engineering Design Activities (EVEDA) phase of IFMIF, which has been launched in the middle of 2007, has two major objectives: to produce the detailed design of the entire IFMIF facility and to build and test the key systems, in particular the prototype of a high-intensity CW deuteron accelerator (125 mA @ 9 MeV). The design of the IFMIF accelerator, as well as the design of the prototype to be installed in Rokkasho (Japan) are presented.
Fermilab, Batavia
Funding: Work supported by US DOE under Contract No. DE-AC02-07CH11359
CHEF is body of software dedicated to accelerator beam dynamics and optics computations. It consists in a hierarchical set of libraries and a standalone application based on the latter. The code makes extensive use of templates and modern idioms such as smart pointers and generalized function objects. CHEF has been described in contributions at past conferences. In this paper, we document and discuss the implementation of recent improvements including:
- use of embedded SQL database technology to store, organize and retrieve lattice function data,
- a general approach to "knobs" based on generalized function objects,
- an improved architecture to support runtime plug-in propagation physics,
- a basic space-charge kick element,
- a facility to record particle loss on aperture boundaries and
- support for the MADX input format.
CLASSE, Ithaca, New York
Cornell University, Ithaca, New York
JLAB, Newport News, Virginia
Cornell University has built a high average current electron injector for use with an Energy Recovery Linac. The injector is capable of up to 100 mA average current at 5 MeV (33 mA at 15 MeV) and is expected to produce the ultra low emittances needed for an ERL. This talk will give an overview of the initial performance of this injector and summarize a spectrum of beam physics experiments undertaken to demonstrate low emittance, high average current operation.
ISIR, Osaka
KEK, Ibaraki
Ultrafast time-resolved electron diffraction based on a photocathode rf electron gun is being developed in Osaka University to reveal the hidden dynamics of intricate molecular and atomic processes in materials. The photocathode rf gun generates a femtosecond-bunch electron beam by femtosecond laser driving. The transverse emittance, bunch length and energy spread were measured. The growths of the emittance, bunch length and energy spread due to the rf and the space charge effects in the rf gun were investigated by changing the laser injection phase, the laser pulse width and the bunch charge. The demonstration of the electron diffraction measurement will be reported.
J-PARC, KEK & JAEA, Ibaraki-ken
For operation of the JPARC Main Ring, low loss of the high-intensity bunches during the injection and acceleration processes is crucial to avoid radiation damage of the machine. This requires identification and correction the most dangerous resonances, which should be done in combination with the collective effects, in particular, the low energy space charge effects. In frame of this talk we review the status of the Main Ring commissioning process and compare it with the simulation results for the low intensity beam. For the future operation of the Main Ring with the moderate beam power we review the status of the simulation work and discuss the budget of the beam losses.
GSI, Darmstadt
ORNL, Oak Ridge, Tennessee
IAP, Frankfurt am Main
CEA, Gif-sur-Yvette
Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 ‘‘Structuring the European Research Area’’ program (CARE, Contract No. RII3-CT-2003-506395).
Beam dynamics experiments with high intensity beams have been conducted at the GSI UNILAC in 2006-2008 with the goal of benchmarking four major simulation codes, i.e. DYNAMION, PARMILA, TraceWin/PARTRAN and LORASR with respect to transverse emittance growth along a DTL. The experiments comprised measurements of transverse phase space distributions in front of as well as behind the DTL. Additional longitudinal bunch length measurements at the DTL entrance allowed for estimate and control of mismatch in all three planes. Measured effects of mismatch and of theoretically predicted space charge resonances (equipartitioning and others) are compared with simulations for a wide range of transverse phase advance along the DTL. This contribution is the first report on the successful measurement of a space charge driven fourth order resonance in a linear accelerator.
Fermilab, Batavia
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Ionization cooling is essential for realization of Muon Collider, muons beam based neutrino factories and other experiments involving muons. The simplest structure - absorber(s) immersed in alternating solenoidal magnetic field - provides only transverse cooling since the longitudinal motion in the most suitable momentum range (2-300MeV/c) is naturally antidamped. To overcome this difficulty it is proposed to periodically tilt solenoids so that a rotating transverse magnetic field was created. By choosing the phase advance per period above a multiple of 2pi it is possible to ensure that muons with higher momentum make a longer path in the absorber (whether distributed or localized) thus providing longitudinal damping. Basic theory of such channel and results of tracking simulations are presented.
UMD, College Park, Maryland
Funding: Work sponsored by the Department of Defense Office of Naval Research and the Joint Technology Office
Recent theoretical and experimental results advancing the state of the art in OTR diagnostics are presented. In particular, new facilities are beginning to operate in regimes where coherent effects are being seen in OTR diagnostics. The state of the art in theory and beam diagnostic data are reviewed and implications for next-generation diagnostic opportunities are presented.
Fermilab, Batavia
Rutgers University, The State University of New Jersey, Piscataway, New Jersey
Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. Experiments as the A0 photoinjector exchange a large longitudinal emittance with a small trasverse emittance. AWA expects to exchange a large transvserse emittance with a small logitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.
Fermilab, Batavia
Different couplers are described that allow the reduction of both transverse wake potential and RF kick in the SC acceleration structure of ILC. A simple rotation of the couplers reducing the RF kick and transverse wake kick is discussed for both the main linac and bunch compressors, along with possible limitations of this method. Designs of a coupler unit are presented which preserve axial symmetry of the structure, and provide reduced both the RF kick and transverse wake field.
ANL, Argonne
Funding: This work was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source is filled for five weeks per year in a special bunch (hybrid) pattern of one large 16-mA (74-nC) bunch in a gap of 3 microseconds, and the remaining 86 mA in 8 trains of 7 consecutive bunches, forming a 500-microsecond-long bunch train. We are developing variations of this bunch pattern, which might have 3 large bunches equally spaced in the 3-microsecond gap in a 4-mA, 16-mA, and 8-mA distribution. The 500-microsecond-long bunch train could be changed to 2 or 3 bunch trains of 7 bunches. We report on the difficulties in bringing these into future operations: impedance-driven injection losses, sextupoles in injection section, lifetime and topup injection limit, and beam diagnostics responses to the patterns.
BNL, Upton, Long Island, New York
Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886
The NSLS-II light source is a proposed 3 GeV storage ring, with the potential for ultra-low emittance*. The lattice design uses a 30 cell DBA structure with a periodicity of 15, for alternating long and short straight sections. All cells are tuned achromatic to maximize the emittance reduction achieved as damping wigglers are added to the ring. Recent optimization of the lattice consisted of increasing the number of possible hard X-ray beam ports using three pole wigglers, reducing the number of magnets (quadrupoles and sextupoles) and shifting the magnets to allow easier extraction of the photon beams. The impact of the reduction of magnets on the lattice flexibility will be presented in terms of the tuning range possible for the lattice parameters: tune, emittance, and chromaticity, beta function matching to user insertion devices (IDs) and for compensating for ID induced distortions to these parameters. This flexibility is important for optimizing the lattice linear and nonlinear properties, the dynamic aperture, and its impact on beam lifetime, as well as matching the user source requirements and for value engineering of magnets and power supplies.
*Work presented on behalf of the NSLS-II Design Team, CDR(2006), CD2(2007) and CD3(2008).
IHEP Beijing, Beijing
Funding: Work supported by National Natural Science Foundation of China contract 10725525
The upgraded project of the Beijing Electron-Positron Collider (BEPCII) can be operated not only for high energy physics experiments as a charm factory, but for synchrotron radiation users as a first generation light source. The design of the synchrotron radiation (SR) mode of the BEPCII storage ring keeps all the original beam lines of the BEPC. The lattice based on the layout of the collider can meet all the requirements of the SR users, and the emittance is minimized. Optimization of the SR mode focuses on reducing the effects from wigglers around the ring. Some results from the operations of the SR mode are also given.
JASRI/SPring-8, Hyogo-ken
An ultra-low emittance storage ring with an energy of 6 GeV was proposed as a next generation synchrotron radiation source*. The storage ring has the same circumference as that of SPring-8 storage ring so as to be able to replace the existing storage ring, but has not four long straight sections. Accordingly, the storage ring beam line is slightly different from that of SPring-8 and the positions of photon beam lines are also different from the existing one. To avoid this, a storage ring with four long straight sections has been designed. The beam line position of the new storage ring is the same as the existing one. The storage ring consists of twenty ten-bend achromat cells, four five-bend achromat cells and four long straight sections. The long straight section length is 34.0 m and the short one is 6.6 m. The natural emittance is less than 100 pm-rad. In the paper, the dynamic aperture problem is discussed and the other ring characteristics are presented.
*K. Tsumaki and N. Kumagai, EPAC’06, 3362.
LBNL, Berkeley, California
Funding: This work was supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
The upgrade of the Advanced Light Source to enable top-off operation has been ongoing for the last four years. Activities over the last year have centered around radiation safety aspects, culminating in a systematic proof that top-off operation is equally safe as decaying beam operation, followed by commissioning and full user operations. Top-off operation at the ALS provides a very large increase in time-averaged brightness to ALS users (by about a factor of 10) as well as improvements in beam stability. The presentation will provide an overview of the radiation safety rationale, commissioning results, as well as experience in user operations.
LLNL, Livermore, California
SLAC, Menlo Park, California
Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
We present a compact, X-band, high-brightness accelerator design suitable for driving a precision gamma-ray source. Future applications of gamma-rays generated by Compton-scattering of laser and relativistic electron beams place stringent demands on the brightness and stability of the incident electron beam. This design identifies the beam parameters required for gamma-ray production, including position, and pointing stability. The design uses an emittance compensated, 11.4 GHz photo-gun and linac to generate 400 pC, 1-2 mm-mrad electron bunches at up to 250 MeV and 120 Hz repetition rate. The effects of jitter in the photo-cathode laser and RF power system are analyzed as well as structure and optic misalignments and wakefields. Finally, strategies for the mitigation of on-axis bremsstrahlung noise are discussed.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The X-ray Free Electron Laser Oscillator* (XFEL-O) is a concept for a high-brightness fourth-generation x-ray source with full spatial and temporal coherence. It is based on a CW electron source and superconducting linac. In order to reduce cost and increase versatility, a recirculating linac configuration is being entertained. In this paper, we present an optics design for the four-pass linac and the three recirculation systems. The design goals are preservation of the beam emittance and energy spread, as well as minimal cost and complexity. We also present the results of tracking studies that show the expected performance.
*K.J. Kim et al., Phys. Rev. Letters, to be published.
BNL, Upton, Long Island, New York
Icarus Research, Inc., Bethesda, Maryland
NRL, Washington, DC
The NSLS Source Development Laboratory (SDL) has been a world leader in the development of laser seeded free electron lasers (FEL). Recently we initiated an experimental program to investigate a Self-Amplified Spontaneous Emission (SASE) FEL in both the exponential gain and the saturation regimes. We have experimentally demonstrated the saturation of a SASE FEL in the visible to near IR. The experimental characterization of the transverse and spectral properties of the SASE FEL along the undulator for a uniformed and tapered undulator will be presented. In addition, an efficiency enhancement concept for a SASE FEL, which involves a step wiggler taper in the exponential gain regime prior to trapping, will be presented. Simulations of the SASE FEL processes will employ the GENESIS FEL code.
CANDLE, Yerevan
PSI, Villigen
The study of radiation saturation length and saturation power sensitivity to beam main parameters (emittance, energy spread and peak current) at the entrance of the undulator section of PSI-XFEL project is presented. The comparative analysis of the SASE FEL performance with external and natural focusing in undulator section is given.
HUST, Wuhan
A primary design of a compact THz FEL oscillator is presented, which is consisted of an independently tunable cell thermionic rf gun (ITC-RF Gun), a rf linac, a planar undulator and an near concentric optical cavity composed of symmetrical spherical mirrors with an on-axis outcouple hole. Without α-magnet and other bunch compressor, the size of this machine is decreased sharply. The effect of the electron beam parameters on THz radiation is discussed. It is found that the influence of energy spread is pronounced and the influence of emittance is neglectable. Large current is required to got saturation in several us. Then the optimized beam parameters and basic design parameters are summarized.
ANL, Argonne
Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
ERL staging is a novel concept that provides a practical path to upgrading an existing synchrotron light source while minimizing disruption to the users and managing the technical risk. In the very first stage, the accelerator operating parameters are comparable to CEBAF without recirculation. Therefore, initially, energy recovery is not required and the injector is more modest. Consequently, the technical risk is significantly reduced relative to the full ERL. Using the APS as an example, the first stage is based on a full-energy, 7-GeV superconducting radiofrequency (srf) linac and an electron source that is almost off-the-shelf. The linac would initially deliver a low average current beam (<200 uA), but with a geometric emittance that is much smaller than the storage ring, the x-ray brightness can exceed the APS. Furthermore, the spatial coherence fraction would be about 100 times higher and the pulse length up to 100 times smaller than the APS. Valuable srf operating experience is attained at an early stage while allowing critical energy recovery issues to be studied. Energy recovery is commissioned in stage 2. The optics design and performance at each stage will be presented.
ANL, Argonne
Funding: This work was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The envisioned next-generation ERL-based x-ray light sources demand costly CW superconducting linacs and high-brightness high-current photoinjectors that are beyond the state of the art. To overcome the fiscal challenge of a multi-GeV CW superconducting ERL and the physical challenge of high-brightness high-current CW photoinjectors, we explore a new scheme using multi-beam injection into a quasi-CW ERL. Multi-beam injection lowers the burden on individual rf injectors at subharmonics of the linac frequency. Lower injector frequency allows higher bunch charge, which permits lower duty factor of the linac with significant reduction in construction and operation costs. Preliminary studies foresee many benefits and no obvious physical showstoppers, despite potential technical challenges. Here we provide a simulation study of a preliminary design.
ISSP/SRL, Chiba
JAEA/ERL, Ibaraki
KEK, Ibaraki
A compact ERL (energy recovery linac) is planned in Japan in order to demonstrate excellent ERL performances and to test key components such as low-emittance photocathode gun and superconducting RF cavity. We studied and optimized the compact ERL optics (except the injector part) to generate a subpico-second bunch in bunch compression mode and to preserve the beam emittance in normal and low-emittance mode. As a result, we could obtain a very short bunch of about 50 fs with a charge of 77 pC in bunch compression mode and almost keep the normalized emittance of 0.1 mm mrad with a charge of 7.7 pC in low-emittance mode. We also designed it to achieve efficient energy recovery at the superconducting RF cavities and to transport the beam to the dump section without serious loss. The design study of the compact ERL optics was carried out with the simulation code Elegant, including CSR(coherent synchrotron radiation) effects. In this paper, we will present the results of the beam optics study for the compact ERL.
CNAO Foundation, Milan
INFN/LNF, Frascati (Roma)
The Centro Nazionale di Adroterapia Oncologica (National Center for Oncological Hadrontherapy, CNAO) is the Italian center for deep hadrontherapy. It will deliver treatments with active scanning both with proton and carbon ion beams. The accelerator complex is based on a 25 m diameter synchrotron capable to accelerate carbon ions up to 400 MeV/u and protons up to 250 MeV. Four treatment lines, in three treatment rooms, are foreseen in a first stage. In one of the three rooms a vertical and a horizontal fixed beam lines are provided, while in the other two rooms the treatment will be administered with horizontal beams only. The injection chain is positioned inside the synchrotron ring itself, to save space and to better exploit the two non-dispersive regions in the synchrotron. The injection chain is made by a 8 keV/u Low Energy Beam Transfer line (LEBT), a RFQ accelerating the beam to 400 keV/u, a LINAC to reach the injection energy of 7 MeV/u and a Medium Energy Beam Transfer line (MEBT) to transport the beam to the synchrotron. This report describes the design and the performances of the CNAO complex, and reports about the status of the commissioning of the machine.
Siemens Med, Erlangen
Siemens DK, Jyllinge
Siemens has earned two contracts to deliver Particle Therapy* systems to be operated in Marburg and Kiel, both in Germany. The accelerator consists of an injector (7 MeV/u protons and light ions) and a compact synchrotron able to accelerate proton beams up to 250 MeV and carbon ions up to 430 MeV/u. These beams can be slowly extracted and delivered to a choice of fixed-angle horizontal, semi-vertical and vertical beam-ports. An overview of the design will be given. At the time of PAC09 installation of the first system will be nearing completion and commissioning will have started. Performance of some of the components and the status of the projects will be presented.
*Particle Therapy is a work in progress and requires country-specific regulatory approval prior to clinical use.
BNL, Upton, Long Island, New York
Ultrafast electron diffraction (UED) is a promising technique that allows us to observe a molecular structure transition on a time scale on the order of femtoseconds. The UED has several advantages over the competing technology, X-Ray Free Electron Laser (XFEL) in terms of its compactness, 6 orders of magnitude larger cross section, and less damaging ability to the samples being probed. Present state-of-the-art UED systems utilize subrelativistic electron bunches as the probing beam. With such low energy, however, the number of electrons in the bunch must be significantly decreased for a short bunch length (~100 fs) due to space charge effects. This limits the detection capability of such keV UED devices. To overcome this issue, a UED system using an MeV electron beam has been proposed, and designed at Source Development Laboratory (SDL) in National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). A detailed performance analysis of this system using the particle tracking code, GPT, from the photoinjector cathode to the detector, will be presented, as well as the status of the commissioning of our UED system.
LPSC, Grenoble
SCK-CEN, Mol
IPHC, Strasbourg Cedex 2
LPC, Caen
CEA Cadarache, Saint Paul Lez Durance
IPN, Orsay
GUINEVERE, Generator-of-Uninterrupted-Intense-NEutrons-at-the-lead-VEnus-REactor, is devoted to ADS feasibility studies and to investigate on-line reactivity monitoring, sub-criticality determination and operational procedures. It will couple a versatile neutron source to the VENUS-F lead core at the SCK·CEN site in Mol (Belgium). It is based on an electrostatic accelerator generating 14 MeV neutrons by bombarding a deuteron beam on a tritium target located in the reactor core. A new accelerator has been developed. It will produce alternatively 1 μs 250 keV deuteron pulses with adjustable repetition rate (40 mA peak), as well as continuous beam (1 mA) with programmable interruptions. Beam will be inserted vertically into the reactor core. The accelerator is designed to enable the vertical section of the beam line to be easily lifted out the reactor bunker for maintenance operations, target changes and core loading procedures. This paper will describe the design of the accelerator and its commissioning in Grenoble (France), before its transfer to the Belgian site. This work is performed within the 6th Framework Program EC project EUROTRANS.
LAL, Orsay
CNAO Foundation, Milan
SOLEIL, Gif-sur-Yvette
NSC/KIPT, Kharkov
The goal of X-ray sources based on Compton back scattering processes is to develop a compact device, which could produce an intense flux of monochromatic X-rays. Compton back-scattering resuls from collisions between laser pulses and relativistic electron bunches. Due to the relative low value of the Compton cross section, a high charge electron beam, a low emittance and a high focusing at the interaction point are required for the electron beam. In addition, the X-ray flux is related to the characteristics of the electron beam, which are themselves dynamically affected by the Compton interaction. One possible configuration is to inject frequently into a storage ring with a low emittance linear accelerator without waiting for the synchrotron equilibrium. As a consequence, the optics should be designed taking into account the characteristics of the electron beam from the linear accelerator. The accelerator ring design for a 50 MeV electron beam, aiming at producing a flux higher than 1013 ph/s, will be presented.
CERN, Geneva
The PS2 is proposed as a replacement for the ageing PS and will provide proton beams with kinetic energies up to 50 GeV. It must also deliver Pb54+ ions, for which the revolution frequency swing will be more than a factor of two. The favoured rf scenario considers a 40 MHz accelerating system and is motivated by the possibility of chopping at up to 40 MHz in the SPL, the proposed proton injector. Using the same principal rf system for ions implies pushing for an unprecedented tuning range and the introduction of a new rf system in LEIR, the existing ion source. We present a solution to the disparate requirements of protons and ions based on a 40 MHz rf system with switchable tuning ranges to cover the large frequency swing required.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
J-PARC, KEK & JAEA, Ibaraki-ken
In J-PARC, Materials and Life Science Facility (MLF) is aimed at promoting experiments using the world highest intensity pulsed neutron and muon beams which are produced at a thick mercury target and a thin carbon graphite target, respectively, by 3-GeV proton beams. The first beam was achieved at the target without significant beam loss. To obtain the beam profile at the target, we applied an activation technique by using thin aluminum foil. In order to obtain reliable profile, it is required that a small number of shots for the beam adjustment and the beam stability. Since beam monitors works very well located at the beam transport line even in the first beam, the beam centralization can be finished by very small number of shots. The stability of beam for each pulse is recognized to be smaller than 1 mm. After many shots of irradiation, the 2-D beam profile can be obtained. It is found that the observed profile shows good agreement with the prediction calculation including the beam scattering at the proton beam window. The beam emittance is measured by the MWPM. It is found that the rms-beam emittance agree with the calculation by the SIMPSONS.
KAERI, Daejon
BNL, Upton, Long Island, New York
Funding: This work is supported by Ministry of Education, Science and Technology of the Korean government.
The proton engineering frontier project (PEFP) is designing the rapid cycling synchrotron (RCS) whose main purpose is the spallation neutron source. The PEFP 100-MeV linac will be the injector to the RCS. The output energy and beam power are 1 GeV and 60 kW at the initial stage. We studied the H- charge exchange injection with transverse and momentum painting schemes. In order to enhance the machine versatility, we studied the slow extraction options for the nuclear physics and medical research in addition to the single turn extraction for the spallation neutron source. This paper summarizes the present status of the physics design of the RCS.
NSCL, East Lansing, Michigan
An 8 GeV proton linac is being considered for the Fermilab accelerator complex. A design calls for five superconducting cavity types: three types of half-wave and two types of multi-cell elliptical structures. The elliptical cavity types have a frequency of 1.3 GHz with a beta = 0.81 and a beta = 1 and provide acceleration from 420 MeV to 8 GeV. An alternative concept would be to use an additional 1.3 GHz elliptical cavity type starting at 150 MeV. The alternative design may reduce project cost and risk. It would increase the technology overlap between Project X and the International Linear Collider. Preliminary simulations show the alternative linac layout has adequate longitudinal acceptance. This paper will discuss the beam dynamics studies for the alternative linac layout in comparison with the baseline layout.
CERN, Geneva
The CERN PS Booster (PSB) produces a variety of beam flavours for the LHC. While the nominal LHC physics beams require 6 Booster bunches with intensities up to 1.6·1012 protons per bunch, during the LHC commissioning single bunch beams with variable intensities as low as 5·109 protons have to be provided reproducibly. The final transverse and in many cases also the final longitudinal beam characteristics have to be achieved already in the PSB and can be very demanding in terms of beam brightness and stability. The optimized production schemes for the different LHC beam flavours in the PSB and the achieved machine performance are presented. Experience with the first beams sent to the LHC in September 2008 is discussed. An overview of the first measured results with a new production scheme of the nominal LHC beam using single instead of double-batch beam transfer from the PSB to the PS is also given.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
J-PARC, KEK & JAEA, Ibaraki-ken
The painting injection of the 3-GeV RCS in J-PARC has been tested since May in 2008. The shift bump-magnets, which give a constant bump field in a horizontal plane during injection, comprise four magnets connected in series. However, the total integrated magnetic field over the four magnets is not zero because of the magnetic field interferences with the neighboring quadrupole magnets. So the gap of each magnet was adjusted by inserting thin insulators into the splitting plane of the side yoke so that the field integration becomes zero. The thickness was determined experimentally. The closed orbit distortion due to the field imbalances was then confirmed to be less than 1 mm. Another four paint bump-magnets are also necessary to give time-dependent fields. They are connected to their own power supplies, separately. The excitation of each magnet is calibrated by using the beam so that the created bump orbit satisfies the position and inclination at the injection point, and there are no orbit distortions outside the injection area. As for a vertical plane, a vertical paint magnet is located pi-radian upstream of the injection point to control the vertical angle of the beam.
CERN, Geneva
For the LINAC4 project the PS Booster (PSB) injection system will be upgraded. The 160 MeV H- beam will be distributed to the 4 superimposed PSB synchrotron rings and horizontally injected by means of an H- charge-exchange system. Operational considerations for the injection system are presented, including expected beam losses from field stripping of H- and excited H0 and foil scattering, possible injection failure cases and expected stripping foil lifetimes. Loading assumptions for the internal beam dumps are discussed together with estimates of doses on various components.
CERN, Geneva
ORNL, Oak Ridge, Tennessee
Fermilab, Batavia
Laser stripping for an H- injection system into the proposed PS2 accelerator could provide an attractive alternative to the use of a conventional stripping foil. In this paper possible concepts for a 4 GeV laser stripping system are outlined and compared, using either laser or magnetic initial stripping steps and a resonant excitation of the intermediate H0 atom, followed by a final magnetic stripping. Issues of laser power, overall efficiency and emittance growth are discussed.
LLNL, Livermore, California
Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Recently, a drive laser for an 2.86 GHz rf photoinjector, designed to provide a pulse that has a flat temporal and spatial profile, has been built, commissioned, and put into service as part of the LLNL Compton-scattering source program. This laser is based on an all-fiber oscillator and front-end amplification system, and provides both the laser light to generate the electrons as well as the rf signal that is amplified to accelerate them. Now, a new 11.424 GHz photoinjector is being developed, which has required a revised design of for the laser system. The higher frequency has placed more stringent requirements on the synchronization stability, delivered pulse length, and pulse rise times to maintain the desired emittance. Presented here are the overall design and measured performance of the current system and a discussion of what changes are being made to address observed shortcomings and more demanding requirements to make the system ready for the next-generation Compton-scattering source.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
We have designed and commissioned a system which blows up the transverse emittance of the anti-proton beam without affecting the proton beam. It consists of a bandwidth limited noise source centered around the betatron tune, a power amplifier and a directional stripline kicker. The amount of blow up is controlled by the amount of energy delivered to the anti-protons betatron bands.
INFN-Napoli, Napoli
UCR, Riverside, California
Funding: World Wide Collaboration of a large fraction of the international agencies.
Muon ionization cooling provides the only practical solution to prepare high brilliance beams necessary for a neutrino factory or muon colliders. The muon ionization cooling experiment (MICE) is under development at the Rutherford Appleton Laboratory (UK). It comprises a dedicated beam line to generate a range of input emittance and momentum, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. A first measurement of emittance is performed in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in liquid hydrogen and RF acceleration. A second spectrometer identical to the first one and a particle identification system provide a measurement of the outgoing emittance. By April 2009 it is expected that the beam and first set of detectors will have been commissioned, and a first measurement of input beam emittance may be reported. Along with the plan of measurements of emittance and cooling that will follow in the second half of 2009 and in 2010.
TUB, Beijing
Funding: This work is supported by National Natural Science Foundation of China(Project 10735050) and National Basic Research Program of China (973 Program)(Grant No. 2007CB815102).
The X-band photocathode RF gun can be utilized to generate electron beams with ultra-low emittance. In this paper, we present the design of a coaxial coupler for the X-band RF gun to avoid the emittance growth caused by field asymmetries. A detailed 3D simulation of the coupler is performed. The microwave circuit analysis is accomplished, and the relationship between the coupling factor and the coaxial coupler size is obtained. This paper likewise presents the beam dynamics parameters of the X-band RF gun with a coaxial coupler.
UMiss, University, Mississippi
The international Muon Ionization Cooling Experiment (MICE) is being built at the Rutherford Appleton Laboratory (RAL), to demonstrate the feasibility of ionization cooling of muon beams. This is one of the major technological steps needed towards the development of a muon collider and a "neutrino factory" based on muon decays in a storage ring. MICE will use particle detectors to measure the cooling effect with high precision, planning to achieve an absolute accuracy on the measurement of emittance of 0.1% or better. The particle i.d. detectors and tracker must work under harsh environmental conditions due to high magnetic fringe fields and RF noise. We will describe the MICE particle i.d. detector systems, and show some current performance measurements of these detectors.
Fermilab, Batavia
Head-tail modes are described when the space charge tune shift significantly exceeds the synchrotron tune. Spatial shape of the modes, their frequencies, coherent growth rates and Landau damping rates are found.
USTC/NSRL, Hefei, Anhui
FEL/Duke University, Durham, North Carolina
Funding: Work supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086 (YKWu), also supported by National Natural Science Foundation of China (No.10175062 and 10575100).
Many modern light source storage rings use a basic magnetic lattice structure consisting of a number of repetitive periodic lattice block, the super periods. The study of one super-period can reveal the dynamical proprieties of the storage ring. Unlike the traditional approach of studying the one-turn map of the storage ring, the work focuses on the study of a super-period lattice, which allows us to gain new insight into the storage ring dynamics using a simpler magnetic structure. In this paper, both analytical and numerical techniques, including Lie Algebra and Normal Form, and particle tracking and frequency analysis, are used to study the nonlinear dynamics of one super-period of a standard double-bend achromat (DBA) and triple-bend achromat (TBA) with two or more nonlinear elements (e.g. sextupoles). The relationship between the super-period dynamics and storage ring dynamics is explored in terms of the global lattice tuning and local lattice selection for straight sections.
H. Hao is currently working as a visiting scholar at Duke University Free Electron Laser Laboratory.
BNL, Upton, Long Island, New York
UMD, College Park, Maryland
JLAB, Newport News, Virginia
Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office
In this paper we report on a proof of principle experiment for demonstrating the possibility of reconstructing the time resolved-phase-space distribution of a space-charge dominated beam by a tomographic technique which provides us with far more information than a time-sliced emittance. We emphasize that this work describes and demonstrates a new methodology which can be applicable to any beam pulse using imaging methods with the appropriate time resolution for the pulse duration. The combination of a high precision tomographic diagnostic with fast imaging screens and a gated camera are used to produce phase space maps of two beams: one with a parabolic current profile and another with a short perturbation atop a rectangular pulse. The correlations between longitudinal and transverse phase spaces are apparent and their impact on the dynamics is discussed.
LBNL, Berkeley, California
JLAB, Newport News, Virginia
UMiss, University, Mississippi
The international muon ionization cooling experiment (MICE) requires low frequency and normal conducting RF cavities to compensate for muon beams’ longitudinal energy lost in the MICE cooling channel. Eight 201-MHz normal conducting RF cavities with conventional beam irises terminate by large and thin beryllium windows are needed. The cavity design is based on a successful prototype cavity for the US MUCOOL program. The MICE RF cavity will be operated at 8-MV/m in a few Tesla magnetic fields with 1-ms pulse length and 1-Hz repetition rate. The cavity design, fabrication, post process plans and as well as integration to the MICE cooling channel will be discussed and presented in details.
PSI, Villigen
INFN/LNF, Frascati (Roma)
RF deflectors are crucial diagnostic tools for bunch length and slice emittance measurements with sub-picosecond resolution. Their use is essential in commissioning and operation of VUV and X-ray FELs. The 250MeV FEL injector, under construction at PSI, will use two of them. The first one will be installed after the gun at low energy (~7MeV), the second one at the end of the Linac at high energy (250MeV). The first RF deflector consists of a single cell standing wave cavity working on the TM110 deflecting mode, and tuned at 2997.912 MHz (frequency of the linac structures). In this note we report the motivation of this measurement, beam dynamics and beam diagnostics considerations and the RF design and simulations of this cavity.
SLAC, Menlo Park, California
Funding: Work supported by the U.S. Department of Energy under contract # DE-AC02-76SF00515 and the US-LARP program
A non-linear time-domain simulation has been developed that can determine technical limitations, effects of non-linearities and imperfections, and impact of additive noise on the interaction of the beam with the Impedance Control Radio Frequency (RF) systems [1]. We present a formalism for the extraction of parameters from the time-domain simulation to determine the sensitivity of the beam longitudinal emittance and dilution on the RF system characteristics. Previous studies [2], [3] have estimated the effect of a noise source on the beam characteristics assuming an independent perturbation source of the RF voltage and a simplified beam model with no coupling. We present the methodology for the time-domain simulation study of the dependence of the accelerating voltage noise spectrum on the various RF parameters and the technical properties (such as non-linearities, thermal noise, frequency response etc.) of the Low Level RF (LLRF) system components. Future plans to expand this formalism to coupled bunch studies of longitudinal emittance growth in the LHC at nominal and upgraded beam currents are briefly summarized.
NSRRC, Hsinchu
The design work of the concentric booster for Taiwan Photon Source (TPS) has been well in progress. The circumference is 496.8 m. It consists of modified FODO cells with defocusing quadrupole and sextupole fields built in bending magnets, and combined function focusing quadrupoles with imbedded focusing sextupole. The emittance is about 10 nm-rad at 3 GeV. Several modifications on the structure were made to improve the beam dynamics behaviors. Good dynamic aperture and nonlinear behavior as well as good tunability are shown. The efficient closed orbit correction scheme is presented. The repetition rate is 3 Hz, and the eddy current effect is also discussed.
NSRRC, Hsinchu
Quadruple Bend Achromat (QBA) low emittance lattice of 3GeV Taiwan Photon Source (TPS) allows us to consider three configurations for location of a pair of superconducting transverse RF deflecting cavities for generation ultra short X-ray pulses. The available arrangements for location of cavities in a super-period of TPS are investigated. We find that use of such deflecting cavities in the middle of two QBA lattices in a super-period of TPS provides better conditions for emittance of electron beam.
NSRRC, Hsinchu
Deflecting cavity generates a correlation between longitudinal position and vertical momentum of electrons in the synchrotron light sources for production short X-ray pulses. Use of such structures leads to growth in vertical amplitude and slope of stored electrons. Since errors are characteristic of real machine, any errors associated with the photon compression system must be considered and the tolerance of them must be evaluated. In this paper we present simulation of main errors due to deflecting structures, QBA lattice and injection system and find tolerances of them.
PSI, Villigen
MAX-lab, Lund
Utilizing a large number of non-dispersive (24) and dispersive (6) skew quadrupoles the betatron coupling and the vertical spurious dispersion can be simultaneously reduced to extremely small values. As a result the achieved vertical emittance begins to approach its ultimate limit, set by the fundamental quantum nature of synchrotron radiation, which in the SLS case is ~0.55 pm.rad. At the same time emittance measurements based on the fitting of a diffraction limited vertical photon beam from a dipole have been pushed to the limit in order to verify this ultra-low vertical emittance.
PSI, Villigen
Recently the energy acceptance and Touschek lifetime of the storage ring of the Swiss Light Source (SLS) could be successfully set to values in agreement with simulations for an ideal lattice. This was finally achieved through control of linear coupling and symmetrization of the sextupole pattern. 36 small corrector magnets were installed for this purpose as additional windings on the ring sextupoles: 30 skew quadrupoles (24 at zero and 6 at maximum dispersion) and 6 auxiliary sextupoles. Base for the success of these measures were previous corrections of dipolar and quadrupolar errors, which we will summarize briefly.
SLAC, Menlo Park, California
Stanford University, Stanford, California
UCLA, Los Angeles, California
Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
SSRL and SLAC groups are developing a long-range plan to transfer its evolving scientific programs from the SPEAR3 light source to a much higher performing photon source that would be housed in the 2.2-km PEP-II tunnel. While various concepts for the PEP-X light source are under consideration, including ultimate storage ring and ERL configurations, the present baseline design is a very low-emittance storage ring. A hybrid lattice has DBA or QBA cells in two of the six arcs that provide a total ~30 straight sections for ID beam lines extending into two new experimental halls. The remaining arcs contain TME cells. Using ~100 m of damping wigglers the horizontal emittance at 4.5 GeV would be ~0.1 nm-rad with >1 A stored beam. PEP-X will produce photon beams having brightnesses near 1022 at 10 keV. Studies indicate that a ~100-m undulator could have FEL gain and brightness enhancement at soft x-ray wavelengths with the stored beam. Crab cavities or other beam manipulation systems could be used to reduce bunch length or otherwise enhance photon emission properties. The present status of the PEP-X lattice and beam line designs are presented and other implementation options are discussed.
SLAC, Menlo Park, California
Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515
SLAC National Accelerator Laboratory is studying an option of building a high brightness synchrotron light source machine, PEP-X, in the existing PEP-II tunnel*,**. By replacing 6 arcs of FODO cells of PEPII High Energy Ring (HER) with two arcs of DBA and four arcs of TME and installation of 89.3 m long damping wiggler an ultra low beam emittance of 0.14 nm-rad (including intra-beam scattering) at 4.5 GeV is achieved. In this paper we study the possibility to further reduce the beam emittance by releasing the constraint of the dispersion free in the DBA straight. The QBA (Quadruple Bend Achromat) cell is used to replace the DBA. The ratio of outer and inner bending angle is optimized. The dispersion function in the non-dispersion straight is controlled to compromise with lower emittance and beam size at the dispersion straight. An undulator of period length 23 mm, maximum magnetic field of 1.053 T, and total periods of 150 is used to put in the 30 straights to simulate the effects of these IDs on the beam emittance and energy spread. The brightness including all the ID effects is calculated and compared to the original PEP-X design.
*R. Hettel et al., “Ideas for a Future PEP-X Light Source”, EPAC08, p.2031(2008).
**M-H Wang et al., “Lattice Design of PEP-X as a Light Source Machine at SLAC”, EPAC08, p.2127(2008).
USTC/NSRL, Hefei, Anhui
Hefei Light Source is a second generation VUV light source, whose performance cannot meet the requirements of synchrotron radiation users at the present time. One year ago, the concept of the Hefei Advanced Light Source, whose main features are ultra low beam emittance and high brilliance in VUV and soft X-ray range, was brought forward. In the preliminary design study, a medium scale storage ring and multi bend achromat focusing structure were adopted to achieve beam emittance lower than 0.2 nm.rad. Linear and nonlinear parameter optimizations were performed to obtain large on-momentum and off-momentum dynamic aperture. The design status will be introduced briefly in the presentation.
USTC/NSRL, Hefei, Anhui
Funding: supported by National Natural Science Foundation of China (10705027)
Hefei Advanced Light Source(HALS) is a super low emittance storage ring and has a very poor beam life time. In order to run the ring stablely, Top-up injection will be necessary. Injection system will greatly affect the quality of beam. This article first give a physics design of injecting system. Then the injecting system is tracked under different errors. The responses of storage beam and injecting beam is given in the article.
SLAC, Menlo Park, California
BINP SB RAS, Novosibirsk
Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
For proper operation of the LCLS x-ray free-electron laser, measurement and control of the electron bunch longitudinal phase space is critical. The LCLS accelerator includes two bunch compressor chicanes to magnify the peak current. These magnetic chicanes can generate significant coherent synchrotron radiation (CSR), which can distort the phase space distribution. We propose a diagnostic scheme by exciting a weak skew quadrupole at an energy-chirped, high dispersion point in the first bunch compressor (BC1) to reconstruct longitudinal phase space on an OTR screen after BC1, allowing a detailed characterization of the CSR effects.
SLAC, Menlo Park, California
Funding: Work supported by Department of Energy contract DE-AC03-76SF00515.
The electron beam for the Linac Coherent Light Source (LCLS) at SLAC is accelerated by disk-loaded RF structures over a length of 1 km. The mainly longitudinal field can sometimes exhibit transverse components, which kick the beam in x and/or y. This is normally a stable situation, but when a klystron, which powers some of these structures, has to be switched off and another one switched on, different kicks can lead to quite a different orbit. Some klystrons, configured in an energy and bunch length feedback, caused orbit changes of up to 1 mm, which is about 20 times the σ beam size. The origins and measurements of these kicks and some efforts (orbit bumps) to reduce them will be discussed.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
The Linac Coherent Light Source (LCLS) is an x-ray Free-electron Laser (FEL) being commissioned at SLAC. Recent beam measurements have shown that, using the LCLS injector-linac-compressors, the beam emittance is very small at 20 pC*. A similar low charge operation mode was also suggested and studied**. In this paper we perform start-to-end simulations of the entire accelerator including the FEL undulator and study the FEL performance versus the bunch charge. At 20 pC charge, these calculations associated with the measured beam parameters suggest the possibility of generating a longitudinally coherent single x-ray spike with 2-femtosecond duration at a wavelength of 1.5 nm. At ~100 pC charge level, our simulations show an x-ray pulse with 20 femtosecond duration and up to 1012 photons at a wavelength of 1.5 Å. These results open exciting possibilities for ultrafast science and single shot molecular imaging.
*A. Brachmann et. al., to be published.
**J. Rosenzweig et al., Nuclear Instr. and Meth. A 593, 39-44 (2008); S. Reiche et al., Nucl. Instr. And Meth. A 593, 45-48 (2008).
SLAC, Menlo Park, California
Funding: This work is supported by the Department of Energy contract DE-AC02-76SF00515.
LCLS capabilities can be significantly extended with a second undulator aiming at the soft x-ray spectrum (1- 5 nm). To allow for simultaneous hard and soft x-ray operations, 14 GeV beams at the end of the LCLS accelerator can be intermittently switched into the SLAC A-line (the beam transport line to End Station A) where the second undulator may be located. In this paper, we discuss the A-line optics design for transporting the high-brightness LCLS beams using the existing tunnel. To preserve the high brightness of the LCLS beams, special attentions are paid to effects of incoherent and coherent synchrotron radiation. Start-to-end simulations using realistic LCLS beam distributions are carried out.
SLAC, Menlo Park, California
Microbunching instability is one of the most challenging threats to FEL performances. The most effective way to suppress microbunching instability is to increase the relative slice energy spread of the beam. In this paper we show that the velocity bunching inherently mitigates the microbunching instability. PARMELA simulation indicates that the initial current modulations are suppressed in velocity bunching process, which may be attributed to the strong Landau damping from the relatively large relative slice energy spread.
Universita' degli Studi di Milano, Milano
Istituto Nazionale di Fisica Nucleare, Milano
INFN/LNF, Frascati (Roma)
ENEA C.R. Frascati, Frascati (Roma)
INFN-Roma, Roma
In this paper a possible experiment with the existing SPARC photoinjector is described to generate sub-picosecond high brightness electron bunches able to produce single spike radiation pulses at 500 nm with the SPARC self-amplified spontaneous emission free-electron laser (SASE-FEL). The main purpose of the experiment will be the production of short electron bunches as long as few SASE cooperation lengths, the determination of the shape of the radiation pulse and the validation of the single spike scaling law, in order to foresee operation at shorter wavelength in the future operation with SPARX. We present in this paper start to end simulations regarding the beam production and FEL performance, and discuss the layout of the machine. The experience, gained from this experiment, will help in the configuration of the VUV and X-ray FEL SPARX to obtain FEL pulses below 10 fs.
BNL, Upton, Long Island, New York
Funding: Work performed under Contract Number DE-AC02-98CH10886 under the auspices of the US Department of Energy.
Using the Vernier Scan (or Van der Meer Scan technique), where one beam is swept stepwise across the other while measuring the collision rate as a function of beam displacement, the transverse beam profiles, the luminosity and the effective cross section of the collision monitoring processes can be measured. Data and results from the 2005, 2006 and 2008 polarizded proton runs using different collision detectors are presented and compared.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Recently, an upgrade of RHIC storage RF system with a superconducting 56 MHz cavity was proposed. This upgrade will provide significant increase in the acceptance of storage RF bucket. Presently, the short bunch length for collisions is obtained via RF gymnastics with bunch rotation (called “re-bucketing”), because the length of 197MHz bucket of 5 nsec is too short to accommodate long bunches otherwise. However, some increase in the longitudinal emittance occurs during re-bucketing. The 56MHz cavity will produce sufficiently short bunches which would allow one to operate without re-bucketing procedure. This paper summarizes simulation of beam evolution due to Intra-beam scattering (IBS) for beam parameters expected with the 56 MHz SRF cavity upgrade. Expected luminosity improvement is shown both for Au ions at 100 GeV/nucleon and for protons at 250 GeV.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
There is a strong interest in low-energy RHIC collisions in the energy range below present RHIC transition energy. These collisions will help to answer one of the key questions in the field of QCD about the existence and location of a critical point on the QCD phase diagram. For low-energy RHIC operation, particle losses from the RF bucket are of particular concern since the longitudinal beam size is comparable to the existing RF bucket at low energies. However, operation below transition energy allows us to exploit an Intra-beam Scattering (IBS) feature that drives the transverse and longitudinal beam temperatures towards equilibrium by minimizing the longitudinal diffusion rate using a high RF voltage. Simulation studies were performed with the goal to understand whether one can use this feature of IBS to improve luminosity of RHIC collider at low-energies. This paper presents results of simulations which show that additional luminosity improvement for low-energy RHIC project may be possible with high RF voltage from a 56 MHz superconducting RF cavity that is presently under development for RHIC.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In preparation for the RHIC polarized proton run 2009, simulations were carried out to evaluate the million turn dynamic apertures for different beta*s at the proposed beam energies of 100 GeV and 250 GeV. One goal of this study is to find out the best beta* for this run. We also evaluated the effects of the second order chromaticity correction. The second order chromaticties can be corrected with the MAD8 Harmon module or by correcting the horizontal and vertical half-integer resonance driving terms.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
There is significant interest in RHIC heavy ion collisions at center of mass energies of 5-50 GeV/u, motivated by a search for the QCD phase transition critical point. The low end of this energy range is nearly a factor of four below the nominal RHIC injection center of mass energy of 19.6 GeV/u. There are several operational challenges in the low-energy regime, including harmonic number changes, longitudinal acceptance, magnet field quality, lattice control, and luminosity monitoring. We report on the results of beam tests with protons and gold in 2007–9, including first RHIC operations at √{(sNN)=9.2} GeV and low-energy nonlinear field corrections at √{(sNN)=5} GeV.
Fermilab, Batavia
CERN, Geneva
ETH, Zurich
Funding: Work partly supported by Fermilab, operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
In the Large Hadron Collider –LHC, particles not captured by the RF system at injection or leaking out of the RF bucket may quench the superconducting magnets during beam abort. The problem, common to other superconducting machines, is particularly serious for the LHC due to the very large stored energy in the beam. For the LHC a way of removing the unbunched beam has been studied and it uses the existing damper kickers to excite resonantly the particles travelling along the abort gap. In this paper we describe the results of simulations performed with MAD-X for various LHC optics configurations, including the estimated multipolar errors.
CERN, Geneva
The LHC beams will cross each other and experience perturbations as a result of the beam-beam effect at the interaction points, which can result in emittance growth and halo creation. The beam-beam force is approximately linear for small offsets and highly non-linear for larger offsets with peaks in growth close to 0.3 and 1.5 σ separation. We present a study of the process of going into collisions in the LHC and use simulations to investigate on possible emittance blow-up. We analyze how the crossing scheme can be optimized to minimize the collapsing time of the separation bumps for given hardware constraints.
CERN, Geneva
BNL, Upton, Long Island, New York
KEK, Ibaraki
Funding: This work was supported by the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395).
Modern colliders bring into collision a large number of bunches per pulse or per turn to achieve a high luminosity. The long-range beam-beam effects arising from parasitic encounters at such colliders are mitigated by introducing a crossing angle. Under these conditions, crab cavities (CC) can be used to restore effective head-on collisions and thereby to increase the geometric luminosity. In this paper, we discuss the beam dynamics issues of a single global crab cavity (GCC) for both nominal LHC optics and one upgrade LHC optics.
CERN, Geneva
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
IHEP Beijing, Beijing
LAL, Orsay
KEK, Ibaraki
UMAN, Manchester
SLAC, Menlo Park, California
The CLIC Final Focus System has considerably larger chromaticity than those of ILC and its scaled test machine ATF2. We propose to reduce the IP betas of ATF2 to reach a CLIC-like chromaticity. This would also allow to study the FFS tuning difficulty as function of the IP beam spot size. Both the ILC and CLIC projects will largely benefit from the ATF2 experience at these ultra-low IP betas.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The recent record-setting performance of the Fermilab Tevatron is the culmination of a long series of efforts to optimize the many parameters that go into generating integrated luminosity for the colliding beams experiments. While several complex numerical computer models exist that are used to help optimize the performance of the Tevatron collider program, here we take an analytical approach in an attempt to illustrate the most fundamental aspects of integrating luminosity in the Tevatron. The essential features, such as weekly integrated luminosity and store length optimization, can be understood in a transparent way from basic operational parameters such as antiproton stacking rate and observed beam emittance growth rates in the Tevatron. Comparisons of the analytical model with operational data are provided.
Fermilab, Batavia
Funding: Work supported by the United States Department of Energy under Contract No. DE-AC02-07CH11359
Head-on beam-beam effect may become a major performance limitation for the LHC in one of the upgrade scenarios. Given the vast experience gained from the operation of Tevatron electron lenses, a similar device provides significant potential for mitigation of beam-beam effects at the LHC. In this report we present the results of simulation studies of beam-beam compensation and analyze potential application of electron lense at LHC and RHIC.
LBNL, Berkeley, California
Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
In this paper, we report on studying wire compensation of long-range beam-beam effects using a fully 3D strong-strong beam-beam model. The simulations include two head-on collisions with 0.3 mrad crossing angle and 64 long-range beam-beam collisions near IP 1 and IP5. We found that using conducting wires with appropriate current level will compensate the tail emittance growth due to long-range beam-beam effects. The random fluctuation of current level should be controlled below 0.1% level for a good compensation. Lowering the long-range beam-beam separations by 20% together with wire compensation will improve the luminosity by a few percentage. Further reducing the beam-beam separations causes significant beam blow-up and decrease of luminosity.
LBNL, Berkeley, California
Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Crab cavity is proposed to compensate the geometric luminosity loss of crossing angle collision at LHC upgrade. In this paper, we report on strong-strong beam-beam simulation of crab cavity compensation at LHC using the BeamBeam3D code. Simulation results showed that using a pair of local compensation for each beam could significantly improve the beam luminosity at collision. However, this improvement could be lost with random offset errors from the RF deflection cavities.
PSI, Villigen
CERN, Geneva
LBNL, Berkeley, California
Under nominal operational conditions, the LHC bunches experience small unavoidable offset at the collision points caused by long range beam-beam interactions. Although the geometrical loss of luminosity is small, one may have to consider an increase of the beam transverse emittance, leading to a deterioration of the experimental conditions. In this work we evaluate and understand the dynamics of beam-beam interactions with static offsets at the collision point. A study of the emittance growth as a function of the offset amplitude in collisions is presented. Moreover, we address the effects coming from the beam parameters such as the initial transverse beam size, bunch intensity and tune.
BNL, Upton, Long Island, New York
Funding: Work performed under the auspices of the US DOE.
In the recent years the peak luminosity of the RHIC polarized proton run has been improved. However, as a consequence, the luminosity lifetime is reduced. The beam emittance growth during the beam storage is a main contributor to the luminosity lifetime reduction, and it seems to be caused mainly by the beam-beam effect during collision. It is, therefore, important to better understand the beam-beam collision effects in RHIC with the aid of particle tracking codes. A simulation study of the emittance growth is performed with RHIC machine parameters using the LIFETRAC code*. The initial results of this study were reported in an earlier paper**. In order to achieve a better understanding and to provide guidance for future RHIC operations, we present an in depth investigation of the emittance growth for a range of RHIC operation tunes, bunch lengths and initial emittance. The simulation results are also compared to the available data from experimental measurements.
*D.Shatilov, et al.,"Lifetrac Code for the Weak-Strong Simulation of the Beam-Beam Effects in Tevatron",PAC05 proc.
**J.Beebe-Wang,“Emittance Growth due to Beam-Beam Effect in RHIC”,PAC07 Proc.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Medium Energy eRHIC (MeRHIC), the first stage design of eRHIC, includes a multi-pass ERL that provides 4GeV high quality electron beam to collide with the ion beam of RHIC. It delivers a minimum luminosity of 1032 cm-2s-1. Beam-beam effects present one of major factors limiting the luminosity of colliders. In this paper, both beam-beam effects on the electron beam and the proton beam in MeRHIC are investigated. The beam-beam interaction can induce a head-tail type instability of the proton beam referred to as the kink instability. Thus, beam stability conditions should be established to avoid proton beam loss. Also, the electron beam transverse disruption by collisions has to be evaluated to ensure that the beam quality is good enough for the energy recovery pass. The relation of proton beam stability, electron disruption and consequential luminosity are carried out after thorough discussion.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Beam-beam effects present one of major factors limiting the luminosity of colliders. In the linac-ring option of the eRHIC design, an electron beam accelerated in a superconducting energy recovery linac collides with a proton beam circulating in the RHIC ring. Some specific features of beam-beam interactions should be carefully evaluated for the linac-ring configuration. One of the most important effects on ion beam stability originates from a strongly focused electron beam because of the beam-beam force. This electron pinch effect makes the beam-beam parameter of the ion beam several times larger than the design value, and leads to the fast emittance growth of the ion beam. The electron pinch effect can be controlled by adjustments of electron lattice and the incident emittance. We present results of simulations optimizing ion beam quality in the presence of this pinch effect.
BNL, Upton, Long Island, New York
The luminosity of the eRHIC ring-ring design is limited by the beam-beam effect exerted on the electron beam. Recent simulation studies have shown that the beam-beam limit can be increased by means of an electron lens that compensates the beam-beam effect experienced by the electron beam. This scheme requires proper design of the electron ring, providing the correct betatron phase advance between interaction point and electron lens. We review the performance of the eRHIC ring-ring version and discuss various parameter sets, based on different cooling schemes for the proton/ion beam.
JLAB, Newport News, Virginia
Muons, Inc, Batavia
Designers of high-luminosity energy-frontier muon colliders must provide strong beam focusing in the interaction regions. However, the construction of a strong, aberration-free beam focus is difficult and space consuming, and long straight sections generate an off-site radiation problem due to muon decay neutrinos that interact as they leave the surface of the earth. Without some way to mitigate the neutrino radiation problem, the maximum c.m. energy of a muon collider will be limited to about 3.5 TeV. A new concept for achromatic low beta design is being developed, in which the interaction region telescope and optical correction elements, are installed in the bending arcs. The concept, formulated analytically, combines space economy, a preventative approach to compensation for aberrations, and a reduction of neutrino flux concentration. An analytical theory for the aberration-free, low beta, spatially compact insertion is being developed.
ANL, Argonne
SLAC, Menlo Park, California
Funding: This work was supported by the US Department of Energy Office of Science under Contract No. DE-AC02-06CH11357.
The effect of ILC positron source’s helical undulator to the drive electron beam is of great interest. People have been looking into the effect of wakefield, quad misalignment and also the effect of radiation. In this paper we’ll report an emittance damping effect of the ILC positron source undulator to the drive electron beam and our QUAD-BPM error simulation results. For 100m RDR undulator, the emittance of drive electron beam will be damped down by about 1% instead of growing as the damping is stronger than quantum excitation for this RDR undulator with the RDR drive electron beam. Quad-BPM misalignment simulations show that a 20um rms misalignment error in a 250m long undulator beamline can cause about 5% emittance growth in drive electron beam. Taking into consider the damping effect of undulator, the net emittance growth will be smaller.
LAL, Orsay
IFIC, Valencia
KEK, Ibaraki
SLAC, Menlo Park, California
Since several years, the vertical beam emittance measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, has been significantly larger than that measured in the damping ring (DR) itself. The EXT line that transports the beam to the ATF2 Final Focus beam line has been rebuilt, but the extraction itself remains in most part unchanged, with the extracted beam transported off-axis horizontally in two of the quadrupoles, beyond the linear region for one of them. A few other nearby magnets have also modelled or measured non-linearity. In case of a residual vertical beam displacement, this can result in increased vertical emittance through coupling between the two transverse planes. Tracking studies as well as measurements have been carried out to study this effect and the induced sensitivity of beam optical parameters to the trajectory at injection, in view of deriving tolerances for reproducible and stable operation.
INFN/LNF, Frascati (Roma)
CERN, Geneva
The CLIC drive beam current, produced by the 1 GHZ fully loaded Linac, will be multiplied by a factor of 24 by the frequency multiplication system, to generate the high power beam representing the CLIC power source. The frequency multiplication system is composed by one delay loop plus two combiner rings. All rings will be isochronous, will contain trajectory tuning wigglers, and all magnets will be normal conducting. The design of the rings, with special emphasis on the rf deflectors characteristics, is presented.
Muons, Inc, Batavia
Fermilab, Batavia
Funding: Supported in part by DOE STTR grant DE-FG02-05ER86252
Earlier studies on the front end of a neutrino factory or muon collider have relied on a single simulation tool, ICOOL. We present here a cross-check against another simulation tool, G4beamline. We also perform a study in economizing the number of RF cavity frequencies and gradients. We conclude with a discussion of future studies.
Fermilab, Batavia
Muons, Inc, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-05ER86252 and FRA DOE contract number DE-AC02-07CH11359
Gas-filled RF cavities can provide high-gradient accelerating fields for muons, and can be used for simultaneous acceleration and cooling of muons. In this paper we explore using these cavities in the front-end of the capture and cooling systems for neutrino factories and muon colliders. We consider using gas-filled RF cavities for the initial front end cooling systems. We also consider using them for simultaneous phase-energy rotation and cooling in a front-end system. We also consider using lower-density RF cavities, where the gas density is primarily for RF breakdown suppression, with less cooling effect. Pressurized RF cavities enable higher gradient rf within magnetic fields than is possible with evacuated cavities, enabling more options in the front-end. The status of designs of the capture, phase rotation, and precooling systems of muon beams in pressurized cavities is described.
Fermilab, Batavia
Muons, Inc, Batavia
Northern Illinois University, DeKalb, Illinois
Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282 and by FRA under DOE Contract DE-AC02-07CH11359
MANX is a six-dimensional muon ionization cooling demonstration experiment based on the concept of a helical cooling channel in which a beam of muons loses energy in a continuous helium or hydrogen absorber while passing through a special superconducting magnet called a helical solenoid. The goals of the experiment include tests of the theory of the helical cooling channel and the helical solenoid implementation of it, verification of the simulation programs, and a demonstration of effective six-dimensional cooling of a muon beam. We report the status of the experiment and in particular, the proposal to have MANX follow MICE at the Rutherford-Appleton Laboratory (RAL) as an extension of the MICE experimental program. We describe the economies of such an approach which allow the MICE beam line and much of the MICE apparatus and expertise to be reused.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
Funding: Supported in part by USDOE STTR Grant DE-FG02-05ER86253
Muon collider luminosity depends on the number of muons in the storage ring and on the transverse size of the beams in collision. Six-dimensional cooling schemes now being developed will reduce the longitudinal emittance of a muon beam so that smaller high frequency RF cavities can be used for later stages of cooling and for acceleration. However, the bunch length at collision energy is then shorter than needed to match the interaction region beta function. New ideas to shrink transverse beam dimensions by lengthening each bunch (reverse emittance exchange and bunch coalescing) will help achieve high luminosity in muon colliders with fewer muons. Analytic expressions for the reverse emittance exchange mechanism are derived, including a new resonant method of beam focusing. Correction schemes for the aberrations were explored, and a lattice to implement them was proposed. To mitigate space charge detuning and wake field effects, a scheme was invented to coalesce smaller intensity bunches after they are cooled and accelerated to high energy into intense bunches suitable for a muon collider.
Muons, Inc, Batavia
Fermilab, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282
The MANX experiment is to demonstrate the reduction of 6D muon phase space emittance using a continuous liquid absorber to provide ionization cooling in a helical solenoid magnetic channel. The experiment involves the construction of a short two-period long helical cooling channel (HCC) to reduce the muon invariant emittance by a factor of two. The HCC would replace the current cooling section of the MICE experiment now being setup at the Rutherford Appleton Laboratory. The MANX experiment would use the existing MICE spectrometers and muon beam line. This paper shall consider the various approaches to integrate MANX into the RAL hall using the MICE spectrometers. This study shall discuss the matching schemes used to minimize losses and prevent emittance growth between the MICE spectrometers and the MANX HCC. Also the placement of additional detection planes in the matching region and the HCC to improve the resolution will be examined.
Muons, Inc, Batavia
Illinois Institute of Technology, Chicago, Illinois
Funding: Work supported in part by USDOE STTR Grant DE FG02 08ER86281.
We describe an approach that can extend the utility of frictional cooling, originally developed for muon beams, to other particles and ions, producing beams of exceptionally low normalized emittance. Moreover, via this approach the small momentum acceptance typical of frictional cooling channels can be increased by two to three orders of magnitude, making it possible to handle much larger intensities with much higher transmission, while preserving the exceptionally low normalized emittance of the output. Simulation studies have been used to optimize the design and performance for a variety of ions and particles, and an inexpensive experiment has been designed to test and verify the concept and simulations, using alpha particles from a radioactive source.
UCLA, Los Angeles, California
We describe the Li Lens concept for a cooler for the transverse emittance for a μ+μ- collider. Different configurations are discussed such as Linear Cooler, Ring Coolers all with Li Lens inserts. We then describe a program to study the construction of Liquid Li Lens and a possible experiment at FNAL.
CLASSE, Ithaca, New York
Funding: Work supported by the National Science Foundation and the US Department of Energy
The Cornell Electron Storage Ring has been reconfigured as a test accelerator (CesrTA) for the investigation of the beam physics of a linear collider damping ring. The low beta interaction region optics have been replaced with simple FOFO lattice structures. Superconducting damping wigglers are located in straights where horizontal dispersion can be constrained to be zero to minimize horizontal emittance. The flexibility of the CESR optics allows for an energy reach of 1.5 GeV /beam→ 6.0GeV/beam and a wide range of emittances and radiation damping times. We exploit that flexibility for measurements of the dependencies of various phenomena, on energy, emittance, and damping rate. At 2GeV beam energy, with no damping wigglers, the minimum horizontal emittance is 10nm. With 16 meters of wiggler magnets operating at 1.9 T, the horizontal emittance is reduced by a factor of four to 2.5 nm and the radiation damping time to 56ms. With tuning and alignment we expect to reach a vertical emittance approaching that of the International Linear Collider (ILC) damping rings. We report on the details of the CesrTA optics and the measurements of optical parameters.
CLASSE, Ithaca, New York
Funding: Support provided by the US National Science Foundation and the US Department of Energy.
The Cornell Electron Storage Ring has been reconfigured as a test accelerator (CesrTA) for low emittance damping ring R&D for the International Linear Collider (ILC). We are developing low emittance tuning techniques with a goal of 1) achieving a vertical emittance approaching that of the ILC damping rings and 2) Gaining an understanding of the effectiveness of those techniques. We will use gain mapping to characterize beam position monitor (BPM) electrode gains, orbit response analysis to determine BPM button misalignments, betatron phase and coupling measurements to characterize optical errors, and orbit and dispersion measurements to locate sources of vertical dispersion. We are investigating a nondestructive dispersion measurement that depends on exciting a synchrotron oscillation and monitoring the phase and amplitude at each BPM. We have developed the analysis tools necessary to correct magnet and alignment errors. An x-ray beam size monitor is being deployed that will allow us to monitor vertical emittance in real time, allowing for empirical tuning of beam size. We will describe the measurement and correction techniques and show data demonstrating their efficacy.
CERN, Geneva
BINP SB RAS, Novosibirsk
INFN/LNF, Frascati (Roma)
Optics design optimisation studies have been undertaken for the CLIC damping ring lattice. Main parameters such as the ring energy and output longitudinal emittance were reconsidered in order to reduce the detrimental effect of collective instabilities. In this respect, the low emittance arc cell length was rationalized taking into account space and magnet design requirements. The straight section cell filled with super-conducting wigglers was modified to accommodate a robust absorption scheme. Several low emittance rings were considered and compared with respect to their dynamic aperture and the IBS-dominated output emittances.
National Technical University of Athens, Zografou
CERN, Geneva
The CLIC pre-damping rings have to accommodate a large emittance beam, coming in particular from the positron target and reduce its size to low enough values for injection into the main damping rings. In particular, polarized positron stacking imposes stringent requirements with respect to longitudinal acceptance and damping times. Linear lattice design options based on low-emittance cells, multiple bend cells and the inclusion of damping wigglers are compared with respect to linear optics functions, tunability, chromatic properties and acceptance. The optics of special regions for the placement of injection, extraction and RF elements are also presented. Non-linear dynamics simulations are finally undertaken for evaluating and maximizing the rings dynamic aperture, especially for large momentum spreads.
Sheffield University, Sheffield
The MICE experiment requires a beam of low energy muons to test muon cooling. This beam is derived parasitically from the ISIS accelerator at the Rutherford Appleton Laboratory. A novel target mechanism has been developed which allows the insertion of a small titanium target into the proton beam on demand, for the final couple of milliseconds before extraction. The first operational linear drive was installed onto ISIS in January of 2008. Since then, it has operated for over 100,000 actuations. Studies have been performed of particle production and collection by the MICE beam-line, as well as verification of the reliability of the target drive itself. The target data acquisition system records not only the position of the target throughout the ISIS acceleration cycle, but also the outputs from beam loss monitors placed around the synchrotron. Data will be presented showing the stability of the target’s motion and the correlation of beam loss and particle production with the timing and depth of the target’s intersection with the circulating beam.
ELETTRA, Basovizza
Funding: The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2.
The FERMI@elettra electron beam dump is designed for a 1nC, 1.8 GeV, 50Hz repetition rate beam. Using GEANT simulations, materials are chosen to absorb 99% of the beam energy and to limit the radio-isotope production. In addition, from the energy deposition distribution inside the dump, the thermal load is estimated. The necessary requirements, the design and the expected performance are presented and discussed.
LBNL, Berkeley, California
Funding: US Department of Energy contract No. DE-AC02-05CH11231, and NSF Grant 0614001
We discuss the design and current status of experiments to couple the THUNDER undulator to the Lawrence Berkeley National Laboratory (LBNL) laser wakefield accelerator (LWFA). Currently the LWFA has achieved quasi-monoenergetic electron beams with energies up to 1 GeV*. These ultra-short, high-peak-current, electron beams are ideal for driving a compact XUV free electron laser (FEL)**. Understanding the electron beam properties such as the energy spread and emittance is critical for achieving high quality light sources with high brightness. By using an insertion device such as an undulator and observing changes in the spontaneous emission spectrum, the electron beam energy spread and emittance can be measured with high precision. The initial experiments will use spontaneous emission from 1.5 m of undulator. Later experiments will use up to 5 m of undulator with a goal of a high gain, XUV FEL.
*W.P. Leemans et al., Nature Physics, Volume 2, Issue 10, pp. 696-699 (2006).
**C.B. Schroeder et al., Proceedings AAC08 Conference (2008).
SLAC, Menlo Park, California
PSI, Villigen
Stanford University, Stanford, California
MPQ, Garching, Munich
Funding: DOE Grants DE-AC02-76SF00515, DE-FG06-97ER41276
An experimental effort is currently underway at the SLAC National Accelerator Laboratory to focus a 50pC, 60 MeV electron beam into the hollow core of a commercial photonic bandgap fiber. The wakefield radiation produced in the fiber will be spectrally analyzed using a spectrograph in order to detect the frequency signatures of fiber modes that could be used as accelerating modes in a laser-driven fiber-based accelerator scheme. We discuss the current status of the experiment, including efforts to successfully focus the electron beam through the fiber aperture and to collect the produced wakefield radiation.
Tech-X, Boulder, Colorado
CIPS, Boulder, Colorado
LBNL, Berkeley, California
University of Nevada, Reno, Reno, Nevada
Funding: Supported by the US DOE Office of Science, Office of High Energy Physics under grant No. DE-FC02-07ER41499; used NERSC resources under grant DE-AC02-05CH11231.
Laser wakefield accelerators (LWFA) have accelerated ~100 pC electron bunches to GeV energies over cm scale distances, via self-trapping from the plasma. Self-trapping cannot be tolerated in staged LWFA modules for high-energy physics applications. The ~1% energy spread of self-trapped electron bunches is too large for light source applications. Both difficulties could be resolved via external injection of a low-emittance electron bunch into a quasilinear LWFA, for which the dimensionless laser amplitude is less than two. However, significant beam charge will result in nonlinear beam loading effects, which will make it challenging to preserve the low emittance. The cold, relativistic fluid model of the parallel VORPAL framework* will be used to simulate the laser-driven electron wake, in the presence of an idealized electron beam. Profiles of the electron beam density, laser pulse envelope and plasma channel will be varied to find a nonlinear beam loading configuration that approximately flattens the electric fields across the beam. Hybrid fluid-PIC simulations will be used to measure the self-consistent emittance growth of the beam.
* C. Nieter and J.R Cary, J. Comp. Phys. 196 (2004), p. 448.
UCLA, Los Angeles, California
SLAC, Menlo Park, California
Funding: Work supported by DOE grant numbers: DE-FG03-92ER40727, DE-FG52-06NA26195, DE-FC02-07ER41500, DE-FG02-03ER54721
The fourth generation of light sources (such as LCLS and the XFEL) require high energy electron drivers (16-20GeV) of very high quality. We are exploring the possibility of using a high transformer ratio PWFA to meet these challenging requirements. This may have the potential to reduce the size of the electron drivers by a factor of 5 or more, therefore making these light source much smaller and more affordable. In our design, a high charge (5-10nC) low energy driver (1-3GeV) with an elongated current profile is used to drive a plasma wake in the blowout regime with a high transformer ratio (5 or more). A second ultra-short beam that has high quality and low charge beam (1nC) can be loaded into the wake at a proper phase and be accelerated to high energy (5-15GeV) in very short distances (10s of cms). The parameters can be optimized, such that high quality (0.1% energy spread and 1mm mrad normalized emittance) and high efficiency (60-80%) can be simultaneously achieved. The major obstacle for achieving the above goals is the electron hosing instabilities in the blowout regime. In this poster, we will use both theoretical analysis and PIC simulations to study this concept.
USC, Los Angeles, California
Funding: Work supported by US Department of Energy
Preservation of the incoming beam emittance is a key characteristic needed for any accelerating system, including the beam-driven, plasma-based accelerator or plasma wakefield accelerator (PWFA). Electron beams with a density larger than the plasma density propagate in a pure and uniform plasma ion column that acts as a focusing element free of geometric aberrations, and the beam emittance is preserved. On the contrary, positron beams attract plasma electrons that flow through the beam and create a non-uniform charge density inside the beam that can exceed the beam density. The resulting plasma focusing force is non-uniform and non-linear. Experimentally, we observe the formation of a beam halo on a screen placed downstream from the plasma. Analysis of the beam images as a function of the plasma density show that the transverse beam size at the screen is strongly reduced in the high emittance plane, and that in the low emittance plane charge is transferred from the beam core to the halo. Numerical simulations of the experiments show the same behavior and indicate that there is emittance growth is both planes. Experimental and simulations will be presented.
KURRI, Osaka
University of Fukui, Faculty of Engineering, Fukui
Accelerator based neutron source with an internal target (ERIT-emittance recovery internal target) placed into the proton storage ring has been developed. In this scheme, the beam and energy degradation caused by the target are cured by ionization cooling and the thermal and epi-thermal neutron flux of more than 1x109 n/cm2/sec can be obtained. The experimental results will be given in the conference.
LNLS, Campinas
We present an overview of a new synchrotron radiation source currently being designed at the Brazilian Synchrotron Light Laboratory (LNLS) in Campinas. The LNLS-1 light source, based on a 1.37 GeV storage ring, has been in routine operation since 1997. The LNLS-2 light source will consist of an injector system and a low emittance 2.5 GeV electron storage ring capable of delivering undulator radiation with average brightness in excess of 1020 photons/sec/0.1%/mm2/mrad2 in the few hundred eV to several tens of keV photon energy range. High flux radiation up to 100 keV will also be available with the use of superconduting wigglers. In this work, we present the basic design considerations and parameters for a proposed magnetic lattice for LNLS-2, with special attention to providing solutions for the realization of low emittance which are cost effective regarding both the construction investment as well as the operation of the facility. In particular, the possibility of the large scale use of permanent magnet technology for the storage ring lattice magnets is discussed.
NSRRC, Hsinchu
Since use of such deflecting structures leads to growth in vertical amplitude and slope of electrons, non-zero momentum compaction factor, nonlinearities and coupling of the elements between the deflectors affect the tilted electrons even in perfect machine and change their amplitude and slope at second deflecting cavity. It causes the second deflector cannot cancel the first kick perfectly and leads to increase of transverse emittance. We have studied simulation and detail analyses of effects of non-zero momentum compaction factor and sextupoles between the deflecting structures, as sources of emittance degradation in TPS and evaluate how much emittance growths due to the effects. We also contrast the statuses of interior sextupoles and elucidate them.
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
CEA, Gif-sur-Yvette
INFN-Roma II, Roma
ENEA C.R. Frascati, Frascati (Roma)
SOLEIL, Gif-sur-Yvette
INFN-Roma, Roma
University of Tehran, Tehran
UCLA, Los Angeles, California
The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive 500 nm FEL experiments in SASE, Seeding and Single Spike configurations. The SPARC photoinjector is also the test facility for the recently approved VUV FEL project named SPARX. The second stage of the commissioning, that is currently underway, foresees a detailed analysis of the beam matching with the linac in order to confirm the theoretically prediction of emittance compensation based on the “invariant envelope” matching , the demonstration of the “velocity bunching” technique in the linac and the characterisation of the spontaneous and stimulated radiation in the SPARC undulators. In this paper we report the experimental results obtained so far. The possible future energy upgrade of the SPARC facility to produce UV radiation and its possible applications will also be discussed.
ANL, Argonne
Fermilab, Batavia
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The latest version of PTRACK*, the parallel version of the beam dynamics code TRACK, is capable of simulating a very large number of particles (a billion or more). In the case of the Fermilab 8-GeV H-minus linac, it is possible to simulate the actual number of particles in the bunch. Taking advantage of this capability we are revisiting our original beam loss studies**, but this time with larger statistics and including a new process of beam loss which is the stripping of H- ions. TRACK has recently been updated*** with the possibility of stripping H- by three different processes, namely black body radiation, Lorentz force stripping and residual gas interactions. Results of ideal end-to-end simulations (no errors) with the actual number of particles in a beam bunch (860M) as well as error simulations for different sets of errors with 10M and eventually 100M particles per seed will be presented and discussed. These simulations are being performed on Argonne's new petascale computing facility "BG/P".
* J. Xu et al, Proceedings of HB-2008.
** P. Ostroumov, B. Mustapha and V.A. Aseev, Proceedings of Linac-06.
*** J.-P. Carneiro, B. Mustapha and P. Ostroumov, submitted to PRST-AB.
CEA, Gif-sur-Yvette
INFN/LNL, Legnaro (PD)
CIEMAT, Madrid
The two IFMIF (International Fusion Materials Irradiation Facility) accelerators will each have to deliver 5 MW of deuteron beam at 40 MeV. To validate the conceptual design, a prototype, consisting of one 9 MeV accelerator called EVEDA (Engineering Validation and Engineering Design Activity), is being constructed. Beam dynamics studies are entering the final phase for the whole EVEDA and for the accelerating part of IFMIF. The challenging point is to be able to reconcile the very strong beam power and the hands-on maintenance constraint. At energies up to 5 MeV, difficulties are to reach the requested intensity under a very strong space charge / compensation regime. Over 5 MeV, difficulties are to make sure that beam losses can be maintained below 10-6 of the beam intensity. This paper will report the strategies and choices adopted in the optics design and the beam measurement proposal.
Enrico Fermi Institute, University of Chicago, Chicago, Illinois
Fermilab, Batavia
Understanding beam loss in an accelerator is crucial to accelerator design and operation. Losses contribute to a shorter lifetime of a circulating beam, higher radiation doses to accelerator components, and backgrounds in experiments which use the beam. One source of beam loss is diffusion caused by effects such as beam scattering with residual gas in vacuum chamber, noise in the radio frequency acceleration system and power supplies, and beam-beam collisions. We measure the diffusion rate in the Fermilab Tevatron using the flying wire beam profile monitor. We have developed a new technique for interpreting the flying wire data. Using this technique, we measure the proton horizontal diffusion rate for ten stores in the Tevatron during colliding beam operation.
GSI, Darmstadt
The prediction of beam loss for long term storage of a high intensity beam is a challenging task essential for the SIS100 design. On this ground an experimental campaign using a high intensity beam has been performed at GSI on the SIS18 synchrotron with the purpose of extending a previous benchmarking experiment made at the CERN-PS in the years 2002-2003. We report here the results of this experimental campaign and the benchmarking with the simulation predictions.
GSI, Darmstadt
MEPhI, Moscow
Beam loss control in SIS100 is relevant for the design of collimators and for maintaining vacuum quality. We present the status of the studies of beam degradation, due to space charge and magnet imperfections during the accumulation at injection energy. The impact of magnet misalignment on resonances and beam trapping/scattering effects is discussed.
GSI, Darmstadt
IHEP Beijing, Beijing
In the conventional design of rf linacs, the space-charges are not in three-dimension thermal equilibrium. The space-charge couples the longitudinal and transverse will cause equipartitioning process which causes the emittance growth and the halo formation. In the design of the Chinese Spallation Neutron Source (CSNS) linac], three cases are investigated using the Hofmann stability charts to analysis and optimize the layout. In this paper, we present the equipartitioning beam study of the CSNS Alvarez DTL linac.
KEK, Ibaraki
Crossing different types of resonances is unavoidable for the high beam power operation of the JPARC Main Ring. The ‘lattice’ resonances are cause by the realistic machine imperfection including the field and alignment errors. In addition the ‘space charge’ resonances will lead to the emittance growth. The mechanism of the emittance dilution for the realistic machine imperfection in combination with the space charge effects should be studied in the self-consistent manner. In frame of this report we analyze different coherent modes of the space charge dominated beam at the injection energy for the JPARC Main Ring for some basic operation scenario of the machine. This analysis allows to identify the most dangerous resonances and to understand the effect of the emittance dilution remaining after the resonance correction. The study has been performed by using the PTC{}ORBIT code.
LBNL, Berkeley, California
Funding: This work was supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
The Touschek lifetime in low energy or small emittance lepton storage rings strongly depends on the particle density in bunches. In the usual parameter range, this dominates other effects and the lifetime gets shorter with higher the bunch density, i.e. with smaller beam emittance. However, once one gets to extremely small horizontal emittances, this is no longer the case. Since the Touschek scattering process is an energy transfer from the transverse plane to the longitudinal one, the Touschek lifetime actually increases, once the transverse temperature (i.e. emittance) gets small enough. In the usual Touschek lifetime formulas, this is accounted for with a complicated multiparameter function (form factor). This paper presents to our knowledge the first direct measurements of the Touschek lifetime in this region of reversed dependence on horizontal emittance, as well as comparison with theory. The measurements were carried out at the ALS at reduced beam energy and ultrasmall horizontal emittance.
LLNL, Livermore, California
UMD, College Park, Maryland
Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Mismatch oscillations resulting from the propagation of space charge waves in intense beams may lead to halo generation and possible beam loss, and modify longitudinal beam dynamics. These oscillations have amplitudes and frequencies different from that of the main beam and are particularly important in machines such as the University of Maryland Electron Ring (UMER), in which the beam dynamics scale to parameters associated with heavy ion fusion drivers. We use the particle-in-cell (PIC) code, LSP, to simulate space charge wave dynamics in an intense electron beam propagating in a smooth focusing channel with 2-D cylindrical symmetry. We examine the evolution of linear and nonlinear density perturbations in the UMER parameter range for both matched and mismatched beams. Comparisons between LSP simulations and numerical models are presented.
LANL, Los Alamos, New Mexico
At Los Alamos National Laboratory we are actively exploring the feasibility of constructing a 50-keV x-ray free-electron laser. For such a machine to be feasible, we need to limit the cost and size of the accelerator and, as this is intended as a user facility, we would prefer to use proven, conventional accelerator technology. Using recent developments in transverse-to-transverse and transverse-to-longitudinal emittance exchange optics *, **, we present a conceptual 20-GeV conventional electron accelerator design capable of producing an electron beam with a normalized transverse emittance as low as 0.2 mm-mrad, a root-mean-square (RMS) beam length of 74 fs, and an RMS energy spread of 0.01%. We also explore the possibility of introducing a crystallographic mask into the beam line. Combined with a transverse-to-longitudinal emittance exchange optic, we show that such a mask can be used to modulate the electron beam longitudinally to match the x-ray wavelength. This modulation, combined with the very low transverse beam emittance, allows us to not only generate 50-keV x-rays with a 20-GeV electron beam, but also drastically decrease the length of the required undulator.
*P. Emma, Z. Huang, K. -J. Kim, and P. Piot, Phys. Rev. ST Accel. Beams 9, 100702 (2006).
**B. E. Carlsten and K. A. Bishofberger, New J. Phys. 8, 286 (2006).
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A high-brightness electron beam used for linac-based fourth-generation light sources such as X-ray free-electron lasers (FELs) and energy recovery linacs (ERLs) is often non-Gaussian distributed especially in the longitudinal direction. In order to study the intra-beam scattering effect (IBS) in such a beam, we added a slice analysis method to elegant. This paper explains this method and an application result to a possible ERL upgrade of the Advanced Photon Source.
ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
Kinetic space plasma simulations are dominated by PIC (Particle-In-Cell) codes. Due to the inherent noise in PIC simulations, interest in directly solving the Vlasov equation is increasing. With the fast development of supercomputers, this is becoming more realistic. We present our preliminary work on solving the Vlasov equation for beam dynamics simulations*. A high order Spectral Element Method has been applied to achieve high accuracy, easy interpolation, and parallelization. Due to the inherent instability of the Vlasov equation, a spectral filter has been added and mass conservation has been satisfied. The proposed algorithms were validated on 1D1V simulations. A paraxial model of the Vlasov equation (2D2V) has also been studied and compared with PIC simulations at ANL using the BG/P supercomputer.
*J. Xu, P. Ostroumov and J. Nolen, “Highly Scalable Parallel Algorithm for 2D2V Vlasov Equation with High Order Spectral Element Method”, poster on SC08, Austin, Texas, Nov.15-20, 2008.
Cockcroft Institute, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
Cockcroft Institute, Lancaster University, Lancaster
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
This work reports on the developments of a computational infrastructure framework that aids achievement of computational research objectives. Examples from a broad range of accelerator problems will be presented, along with ways in which the workflow can be modified.
Far-Tech, Inc., San Diego, California
Funding: DOE
IonEx is a new hybrid, meshless, cross-platform, 2D code which can model the extraction of ions from a plasma device. The application includes a user-friendly Graphical User Interface (GUI), which contains a geometry editor for specifying the domain. The design of IonEx utilizes the object-oriented functionality of C++, which provides an efficient means of incorporating a magnetic field, an arbitrary geometry, and an unlimited number of ion species into a simulation. Visualization of the resulting trajectories and emittances is accomplished through the GUI; openGL is used to accelerate the graphics. In this paper we will briefly review the physics and computational methods used, highlight important aspects of the object-oriented design, discuss the primary features of the GUI, describe the current status of IonEx, and present some simulation results.
Fermilab, Batavia
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Existing codes for accelerator design (e.g. MAD) are not well suited for ionization cooling channels where particles exhibit strongly dissipative and nonlinear motion. A system of Mathematica programs was developed which allows to: 1) find periodic orbit and eigenvectors of the transfer matrix around it with account of (regular part of) ionization losses and feeddown effect from nonlinear fields; 2) compute emittance growth due to scattering and straggling, find equilibrium values (if exist); 3) analyze nonlinear effects such as dependence of tunes and damping rates on the amplitudes, resonance excitation; 4) perform tracking with account of stochastic processes. Underlying theory and application to helical cooling channel are presented.
IIT, Chicago, Illinois
Illinois Institute of Technology, Chicago, Illinois
Fermilab, Batavia
Muons, Inc, Batavia
Funding: Supported in part by USDOE Contract DE-FG02-6ER86281
The study of Muon beam optics is crucial for future Neutrino Factory and Muon Collider facilities. At present, the GEANT4-based simulation tools for Muon beam tracking such as G4beamline and G4MICE are based on single particle tracking without collective effects taken into account. However, it is known that collective effects such as space charge and wakefields for muons (in matters or vacuum) are not ignorable. As the first step, space charge computation has been implemented into muon tracking. The basic algorithm is particle to particle interactions through retarded electro-magnetic fields. The momentum impulse by collective effects is imposed on every particle at each collective step, and the G4beamline main code is used for tracking. Comparisons to LANL Parmela are illustrated and analyzed. Optimizations of the algorithm are also underway to gain less computing time and more accuracy. Moreover, the idea of enhancing ionization cooling efficiency by utilizing the collective effect due to polarized charges in matter appears to be possible, and the preliminary estimation has been done.
INFN/LNF, Frascati (Roma)
High gain free electron lasers require the production of a high brightness electron beam that is a low emittance, high current beam. To this aim the injector and linac design and theirs operation are the leading edge. The successful operation of the SCSS FEL driven by a C-band linac has demonstrated that C-band is a mature technology and it is very attractive in terms of gradient and compactness. In this paper it is described a beam dynamics study, made with the Homdyn code, for a C-band linac driven FEL with S-band photo-injector. The key point is to match the longitudinal phase space of the S-band photo-injector with the C-band linac using the velocity bunching technique. The result is a brightness up to 1015A/m2, obtained with a low emittance and a relaxed peak current.
JAI, Oxford
The alignment of the next generation of linear accelerators will be much more critical than that of currently existing machines. This is especially true for very long machines with ultra low emittance beams; such as the ILC and CLIC. The design and study of such machines will require a large number of simulations. However; full simulation of misalignment currently requires computer programs which are very resource intensive. A model which can be used to rapidly generate reference networks with the required statistical properties will be presented. The results for emittance growth in the ILC main linac using the model with Dispersion Matched Steering (DMS) applied are also shown.
LBNL, Berkeley, California
Funding: Work supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
Multiobjective optimization has been used in many fields including accelerator related projects. Here we use it as a powerful tool for lattice design and optimization, which includes betatron functions, brightness.
Muons, Inc, Batavia
Funding: Supported in part by USDOE Contract DE-FG02-6ER86281.
The G4beamline program is based on the well-established Geant4 toolkit used to simulate the interactions of particles and photons with matter. Until now, only a single particle at a time could be tracked and there are no interactions between particles. Recent designs for high pressure RF cavities and other novel devices achieving extreme muon cooling require that the effect of space charge be included in the simulations. A new tracking manager in G4beamline propagates a number of particles (typically 1,000-10,000) in parallel, stepping all particles in time. This allows all of the usual Geant4 physics interactions to be applied, plus collective computations. A simple macroparticle-based model is used to represent ~108 charges with an ellipsoidal charge density. At intervals the appropriate macroparticle size and shape are recalculated, the electric and magnetic fields are determined, and an impulse is applied to the simulated particles. Comparisons to standard space charge codes are presented.
Muons, Inc, Batavia
BNL, Upton, Long Island, New York
Funding: Work supported in part by USDOE STTR Grant DE-FG02-08ER86281 and DE AC02 98CH10886.
The U.S. muon collider community is mobilizing itself to produce a “Design Feasibility Study” (DFS) for a muon collider. This is happening on an aggressive schedule and must include the best possible simulations to support and validate the technical design. The DFS for a muon collider will require innovative new approaches to many aspects of accelerator design, and the simulations to support it will require tools with features and capabilities that are equally innovative and new. Two computer programs have emerged as the preferred and most commonly used simulation tools within the muon collider community: ICOOL (primary author: Dr. Fernow), and G4beamline (primary author: Dr. Roberts). We describe the ongoing development and testing of both tools for the DFS, including a common suite of tests to ensure that both tools give accurate and realistic results, as well as innovative user-friendly interfaces with emphasis on graphical user interfaces and windows.
UMAN, Manchester
A technique has been developed which enables the calculation of resistive particle wake effects. The technique can simply be calculated to any order, and is easy and quick to evaluate. No assumptions are made about the range of the interaction, but this is especially useful for short range effects. We show how the exact evaluation compares with various common approximations for some simple cases, and implement the technique in the Merlin and PLACET simulation programs. The extension from cylindrical to rectangular apertures is highlighted.
ANL, Argonne
Northern Illinois University, DeKalb, Illinois
Funding: The work is supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 with Argonne National Laboratory.
Phase space measurements of RF photoinjectors have usually been done with multislit masks or scanning slits. These systems implicitly ignore the correlations between the X and Y planes and thus yield measurements of the projected 2D phase space distributions. In contrast, a grid-patterned pepper-pot is capable of measuring the full 4D transverse phase space distribution, f(x,x',y,y'). 4D measurements allow precise tuning of electron beams with large canonical angular momentum, important for electron cooling and flat beam transformation, as well as zeroing the magnetic field on the photocathode is zero for ultra low emittance applications (e.g. SASE FEL, ERL FEL). In this talk, we report on a parametric set of measurements to characterize the 4D transverse phase space of the 1 nC electron beam from the Argonne Wakefield Accelerator (AWA) RF photoinjector. The diagnostic is simulated with TStep, including the passage of the electron beam trough the mask and tracking of the beamlets to the imaging screen. The phase space retrieval algorithm is then bench marked against simulations and measurements.
BNL, Upton, Long Island, New York
A gas fluorescence beam profile monitor has been realized at the relativistic heavy ion collider (RHIC) using the polarized atomic hydrogen gas jet. RHIC proton beam profiles in the vertical plane are obtained as well as measurements of the width of the gas jet in the beam direction. For gold ion beams, the fluorescence cross section is sufficiently large so that profiles can be obtained from the residual gas alone, albeit with long light integration times and lower number of Au ions than protons. We estimate the fluorescence cross-section of 100 GeV protons and Au ions on hydrogen gas to be 6.6x10-21 cm2 ~1.7x10-16 cm2, respectively*. We calculate the beam emittance to provide an independent measurement of the RHIC beam. This optical beam diagnostic technique, utilizing the beam induced fluorescence from injected or residual gas, represents a step towards the realization of a simple and truly noninvasive beam monitor for high-energy particle beams together with a wall-current-monitor system and/or a low light level optical temporal measurement system, a 3-dimensional particle beam profile system can be envisioned providing routine diagnosis of high-energy particle beams.
*T. Tsang, et. al., Rev. Sci. Instrum. 79, 105103 (2008).
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The proton polarization measurements in AGS and RHIC are based on proton-carbon and proton-proton elastic scattering in the Coulomb Nuclear Interference region. Polarimeter operation in the scanning mode gives polarization profiles and beam intensity profile measurements. This polarimeter is an ideal wire-scanner due to: extremely good signal/noise ratio and high counting rate, which allows accurate bunch by bunch emittance measurements during 100 ms time of the beam crossing. The measurements of the beam emittance in both vertical and horizontal planes will be possible after polarimeter upgrade for the 2009 polarized run. Two new vacuum chambers and two target motion mechanisms and detectors assembly will be installed in each ring. One polarimeter can be used for the vertical polarization and intensity profile measurements and the second can be used for the horizontal profile measurements. The absolute accuracy limitations and cross-calibration of different techniques will be also discussed.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
The ALBA Linac is a turn-key system able to produce 4 nC electron beams at 100 MeV beams with a normalized emittance below 30 mm*mrad. Beam position stability below 0.1 mm is measured using new BPM electronics. Thorough analysis are carried out to measure the beam emittance, energy and energy spread. This paper discusses the measurement techniques, analysis method, and results obtained during the Linac commissioning.
CLASSE, Ithaca, New York
KEK, Ibaraki
Funding: NSF
We report on the performance goals and design of the CESRTA x-ray beam size monitor (xBSM). The xBSM resolution must be sufficient to measure vertical beam sizes under 20um. The xBSM images 2–4keV synchrotron radiation photons onto one-dimensional photodiode array. Instrumentation in the dedicated x-ray beam line includes upstream interchangeable optics elements (slits, coded apertures, and Fresnel zone plates), a monochrometer and the InGaAs photodiode detector. To provide sufficient x-ray flux in 2 GeV operation, the beam line is evacuated, with only a thin diamond window isolating the detector vacuum from the damping ring. The readout is a beam-synchronized FADC that is sufficient to measure consecutive bunches independently in a 4ns bunch spacing configuration.
CLASSE, Ithaca, New York
KEK, Ibaraki
Funding: NSF
Engineering data sets were collected with the CESRTA x-ray beam size monitor (xBSM) during November 2008 and January 2009 runs. We report on the performance of the InGaAs photodiode array detector, including time response and signal-to-noise. We report on the observed measurement resolution for changes in the damping ring vertical beam size using the interchangeable optics elements: slits, coded apertures, and a Fresnel zone plates. Observed resolutions are compared to predictions based on characteristics of the optics elements.
Far-Tech, Inc., San Diego, California
The emittance exchange experiment planned at the Argonne Wakefiel Accelerator facility will rely on a set of cavity-based beam diagnostics in order to map the transport matrix through the beamline. These will include cavity BPM and time-of-flight diagnostics, as well as quadrupole cavity x-y coupling diagnostics. The measurement system will be designed to fit within compact space requirements, while also maintaining a sufficient clear aperture and sensitivity. The RF design of the system, as well as RF cold-test data for the BPM cavities, is presented.
KEK, Ibaraki
CLASSE, Ithaca, New York
UH, Honolulu, HI
Funding: Work supported in part by the US-Japan Cooperation Program
We are working on the development of a high-speed x-ray beam profile monitor for high-resolution and fast response for beam profile measurements to be used at CesrTA and SuperKEKB*. The optics for the monitor are based on a technique borrowed from x-ray astronomy, coded-aperture imaging, which should permit broad-spectrum, low-distortion measurements to maximize the observable photon flux per bunch. Coupled with a high-speed digitizer system, the goal is to make turn-by-turn, bunch-by-bunch beam profile measurements. Following initial tests with a low-resolution mask at large beam sizes (vertical size ~200 um), a high-resolution mask has been made for use with low-emittance beams (vertical size ~10 um) at CesrTA. The first performance results of the high-resolution mask on the low-emittance CesrTA beam are presented.
*J.W. Flanagan et al., Proc. EPAC08, Genoa, {10}29 (2008).
IUCF, Bloomington, Indiana
Fermilab, Batavia
The proton ion source for the High Intensity Neutrino Source (HINS) Linac front-end at Fermilab has been successfully commissioned. It produces a 50 keV, 3 msec beam pulse with a peak current greater than 20 mA at 2.5 Hz. The beam is transported to the radio-frequency quadrupole (RFQ) by a low energy beam transport (LEBT) that consists of two focusing solenoids, four steering dipole magnets and a beam current transformer. To understand beam transmission through the RFQ, it is important to characterize the 50 keV beam before connecting the LEBT to the RFQ. A wire scanner and a Faraday cup are temporarily installed at the exit of the LEBT to study the beam parameters. Beam profile measurements are made for different LEBT settings and results are compared to those from computer simulations. In lieu of direct emittance measurements, a solenoid variation method based on profile measurements is used to reconstruct the beam emittance.
JAI, Oxford
University of Oxford, Clarendon Laboratory, Oxford
University of Oxford, Oxford
INFN/LNF, Frascati (Roma)
OXFORDphysics, Oxford, Oxon
Diamond, Oxfordshire
Funding: John Adams Institute, University of Oxford John Fell Fund, University of Oxford
We describe a method that uses a modified pepper-pot design to measure in a single shot the emittance of electron beams with energies above 100 MeV. Our setup consists of several thin layers of tantalum with spacers in between to leave slits through which the electron beam can be sampled. We report on a measurement done using this method at the DAΦNE BTF with a 508 MeV electron beam.
CERN, Geneva
IN2P3-LAPP, Annecy-le-Vieux
The demanding nanometer transverse beam sizes and emittances in future linear accelerators results in stringent alignment and nanometer vibration stability requirements. For more than two decades, ground vibration measurements were made by different teams for feasibility studies of linear accelerators. Recent measurements were performed in the LHC tunnel and at different CERN sites on the surface. The devices to measure nanometer sized vibrations, the analysis techniques and the results are critically discussed and compared with former measurement campaigns. The implications of the measured integrated R.M.S. displacements and coherence length for the CLIC stabilization system are mentioned.
CERN, Geneva
The CLIC components will have to be pre-aligned within a tolerance of 10 microns over a sliding window of 200m all along the linacs, before injecting the first beam. Such tolerance is about 30 times more demanding than for the existing machines as the SPS and LHC; it is a technical challenge and a key issue for the CLIC feasibility. In order to define the CLIC alignment strategy from the survey and beam dynamics point of view, simulations have been undertaken concerning the propagation error due to the measurement uncertainties of the pre-alignment systems. The uncertainties of measurement, taken as hypotheses for the simulations, are based on the data obtained on several dedicated facilities. This paper introduces the facilities and the latest results obtained, as well as the simulations performed.
ORNL, Oak Ridge, Tennessee
BINP SB RAS, Novosibirsk
Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
A transverse phase space emittance scanner is proposed and under development for the 1-GeV H- SNS linac, using a laser beam as a slit. For a 1 GeV H- beam, it is difficult to build a slit because the stopping distance is more than 50 cm in copper. We propose to use a laser beam as an effective slit by stripping off the outer electron of the H- (making it neutral) upstream of a bend magnet and measuring the stripped component downstream of the bend magnet. The design and modeling of the system will be discussed. We are expecting to make a preliminary measurement in 2009.
Ankara University, Faculty of Sciences, Tandogan/Ankara
The Turkish Accelerator Complex (TAC) is a project for accelerator based fundamental and applied researches supported by Turkish State Planning Organization (DPT). The proposed complex is consisted of 1 GeV electron linac and 3.56 GeV positron ring for a charm factory and a few GeV proton linac. Apart from the particle factory, it is also planned to produce synchrotron radiation from positron ring. In this study the lattice structure design of the positron storage ring is made to produce the third generation synchroton light. It has been studied with different lattice structures (DBA, TBA, DDBA etc.) for TAC. It has been compared lattice structures and tried to find the best structure for lowest emittance.
ASCo, Clayton, Victoria
Emittance coupling in the Australian Synchrotron storage ring is currently controlled using a total of 28 skew quadrupoles. The LOCO method was used to calculate the skew quadrupole settings, using measured vertical dispersion and transverse coupling. This information is used to create a calibrated model of the machine, which is then used to calculate the required skew quadrupole settings needed to minimise coupling. This method has thus far achieved encouraging results for achieving ultra low (<2pm) vertical emittance. In this study we seek to explore the validity of the LOCO model based on empirical measurements and possible improvements of this method.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Booster to AGS (BtA) transfer line was designed to match both ions and protons into the AGS lattice. For proton beam operation the only constraint on the optics is to define a match to the AGS lattice. For ions operation there are constraints introduced by a stripping foil in the upstream part of the transfer line. For polarized proton operation there is the complication that the lattice to match into in the AGS is distorted by the presence of two partial snake magnets. In the 2008 polarized proton run it was observed that there was an optical injection mismatch. Beam experiments were conducted that showed disagreement with the model. In addition, these studies revealed some minor problems with the instrumentation in the line. A new model and more reliable measurements of the transfer line magnet currents have been implemented. Another series of experiments were conducted to test these modifications and to collect a more complete set of data to allow better understanding of the beam dynamics during the transfer and better understanding of the instrumentation. In this paper we will present the results of these experiments and comparison to the new model of the BtA.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
As part of the efforts to increase polarization and luminosity in RHIC during polarized proton operations we have modified the injection optics and stripping foil geometry in the AGS Booster in order to reduce the emittance growth during H- injection. In this paper we describe the modifications, the injection process, and present results from beam experiments.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A new horizontal tune jump mechanism has been proposed to overcome the horizontal intrinsic resonances and preserve the polarization of the proton beam in the AGS during the energy ramp. An adiabatic change of the AGS lattice is needed to avoid the emittance growth in both horizontal and vertical motion, as the emittance growth can deteriorate the polarization of the proton beam. Two critical questions are necessary to be answered: how fast can the lattice be changed and how much emittance growth can be tolerated from both optics and polarization points of view? Preliminary simulations, using a realistic AGS lattice and acceleration rate, have been carried out to give a first glance of this mechanism. Several different conditions are presented in this paper.
Brunel University, Middlesex
STFC/RAL, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
JAI, Oxford
The PAMELA project to design an accelerator for hadron therapy using non-scaling Fixed Field Alternating Gradient (NS-FFAG) magnets requires a transport line and gantry to take the beam to the patient. The NS-FFAG principle offers the possibility of a gantry much smaller, lighter and cheaper than conventional designs, with the added ability to accept a wide range of fast changing energies. This paper will build on previous work to investigate a transport line which could be used for the PAMELA project. The design is presented along with a study and optimisation of its acceptance.
CAEP/IFP, Mainyang, Sichuan
The capability of the chromatic correction of Zumbro Lens lies on the angle-position correlation, which is obtained by passing the beam through an expander or quadruples. However even after a long distance drift downstream the expander, the angle-position correlation can not be perfect because of the existence of finite emittance. This paper discusses the influence of the emittance to the chromatic correction and the optimization of beam status in phase space at the entrance of the expander.
IHEP Beijing, Beijing
JAI, Egham, Surrey
KEK, Ibaraki
ICEPP, Tokyo
SLAC, Menlo Park, California
University of Tokyo, Tokyo
Funding: NSFC 10525525 and 10775154. CNRS-IN2P3 and ANR.
The ATF2 project is the final focus system prototype for ILC and CLIC linear collider projects, with a purpose to reach a 37nm vertical beam size at the interaction point. We report on techniques developed based on simulation studies to adjust the horizontal and vertical beam waists independently in the presence of errors, at two different IP locations where the beam size can be measured with different accuracies. During initial commissioning, we will start with larger than nominal β-functions at the IP, to reduce the effects from higher-order optical aberrations and thereby simplify the optical corrections needed. The first measurements in such intermediate β-configurations are reported.
IHEP Beijing, Beijing
CERN, Geneva
A new design of the 6.6GeV Booster linac for CLIC which is based on the FODO lattice is presented in this note. Particle tracking studies using PLACET [1] are performed in order to estimate the single-bunch and multi-bunch emittance growth. First, the studies of optics are introduced. Then, the sing-bunch effects and multi-bunch effects are studied in the last two part of this note.
CLASSE, Ithaca, New York
The production of ultra-short x-rays in Cornell's Energy Recovery Linac (ERL) requires electron bunch lengths of less than 100fs with minimal transverse emittance growth and energy spread. Because the linac consists of two sections separated by an arc, CSR forces limit the bunch length in the linac, and bunch compression has to be installed after acceleration. Creation of such short bunches requires a second order bunch compression scheme with correction of the third order dispersion. In this paper, we discuss possible bunch compression systems and explore the benefits of each using the tracking program TAO including CSR forces. Overall, we find that a FODO compressor utilizing dipole, quadrupole and sextupole magnets can achieve the design goals of the short pulse mode.
Diamond, Oxfordshire
JAI, Oxford
With the aim of generating short pulse radiation, a low momentum compaction lattice has recently been commissioned for the Diamond storage ring. By introducing both positive and negative dispersion in the bending magnets it has been possible to operate the storage ring in a quasi-isochronous state, resulting in a natural electron bunch length of less than 1 pico-second. A description of the techniques used to develop the lattice is given, along with first results obtained during recent machine trials. Operation with both positive and negative momentum compaction factor is also described
CERN, Geneva
The maximum intensity the CERN PS has to deliver is continuously increasing. In particular, during the next years, one of the most intense beam ever produced in the PS, with up to 3000·1010 proton per pulse, should be delivered on a regular basis for the CNGS physics program. It is now known that the existing radiation shielding of the PS in some places is too weak and constitutes a major limitation due to large beam losses in specific locations of the machine. This is the case for the injection region: losses appear on the injection septum when the beam is injected in the ring and during the first turn, due also to an optical mismatch between the injection line and the PS. This paper presents the experimental studies and the simulations which have been made to understand the loss pattern in the injection region. Possible solutions to reduce the beam losses will be described, including the computation of a new injection optics.
CERN, Geneva
At present, for most LHC type physics beams, six buckets of the PS operated with harmonic number h=7 are filled in two transfers, and each of the PS Booster rings provides only one bunch. The scheme presented aims at replacing the double batch transfer by a single batch transfer and is of interest (i) for the nominal 25 ns LHC beams once the Booster injection energy has been increased after completion of Linac4 and (ii) already now for 50 ns and 75 ns LHC beams less demanding for the Booster in terms of beam brightness. Two bunches with the correct spacing must be generated in the Booster rings by superposition of an h=2 RF system and a smaller h=1 component. Theoretical considerations and first experimental results will be presented.
CERN, Geneva
Control of beam losses is an important aspect of the H- injection system for the PS2, a proposed replacement of the CPS in the CERN injector complex. H- ions may pass the foil unstripped or be partially stripped to excited H0 states which may be stripped in the subsequent strong-field chicane magnet. Depending on the choice of the magnetic field, atoms in the ground and first excited states can be extracted and dumped. The conceptual design of the waste beam handling is presented, including local collimation and the dump line, both of which must take into account the divergence of the beam from stripping in fringe fields. Beam load estimates and activation related requirements of the local collimators and dump are briefly discussed.
CERN, Geneva
In the main linac of the compact linear collider (CLIC) the beam induced wakefield and dispersive effects will be strong. In the paper the reference beam-based alignment procedure for the new CLIC parameters is specified and the resulting tolerances for static imperfections are detailed.
CERN, Geneva
In the compact linear collider (CLIC) the tolerances on dynamic imperfections are tight in the main linac. In particular the limited beam delivery system bandwidth requires very good RF phase and amplitude stability. Transverse motion of the beam line components is also of concern. The resulting tolerances are detailed in the paper.
CERN, Geneva
Uppsala University, Uppsala
Fermilab, Batavia
Prior to acceleration in the main linac, the particle beams created in the centrally located injector have to be transported to the outer ends of the CLIC site. This transport should not only preserve the beam quality but also shape, characterize and tune the phase space distribution to match the requirements at the entrance of the main linac. Hence, the performance of the transport downstream of the damping rings up to the main linac, the so called RTML, is crucial for the overall performance of CLIC. The RTML consists of a variety of components like bunch compressors, accelerating cavities, spin rotators, collimators, diagnostics sections, feedback and feedforward systems, each serving a distinct function. We discuss the different parts of the RTML and the beam dynamics challenges connected to them. Their status is outlined and results of beam dynamics simulations are presented.
Imperial College of Science and Technology, Department of Physics, London
The Muon Ionisation Cooling Experiment (MICE) at RAL will be the first apparatus to study muon cooling at high precision. Muons are produced along a transport beamline in a super-conducting solenoid via pion decay. The final beam emittance is generated by tuning the quadrupoles for beam size matching. The beam angular divergence is matched in a variable-thickness diffuser, which is a re-entrant mechanism inside the first solenoid, automatically changeable in few minutes from 0 to 4X0. The initial normalized emittance of the beam (few mm rad) will be inflated up to 10 mm rad in order to cover the (eN,P) matrix required by the experiment. Details of beamline tuning are presented.
TU Darmstadt, Darmstadt
Funding: Supported by DFG via SFB 634
Operational Experience at the Darmstadt superconducting linac (S-DALINAC) showed unexpected effects on beam dynamics and beam quality. So operators could observe transverse beam deflections by changing phases of the SRF-Cavities. Furthermore there has been occurred a growth of normalized tranverse emittance by a factor of 2. The beam current in the S-DALINAC does not exceed 60 μA so space-charge effects could be eliminated to be the reason for the observations. In this work the effect of misalignment of the SRF-Cavities in the linac has been examined using beam-dynamic simulations with the tracking code GPT and measurements on the electron beam of the S-DALINAC. By measuring the transverse deflection of the beam by changes of the phases of the SRF-Cavities and comparing results with GPT-simulations a misalignment of the 5-cell capture cavity and first 20-cell cavity of several mm in both transverse directions could be found. This misalignment can explain transverse deflections as well as emittance growth. A correction of misalignment has been carried out using the described results. First measurements showed no more emittance growth and less beam-deflections by SRF-Cavities.
INFN/LNF, Frascati (Roma)
University of Pisa and INFN, Pisa
SLAC, Menlo Park, California
The novel crab waist collision scheme under test at the DAΦNE Frascati phi-factory finds its natural application to the SuperB project, the asymmetric e+e- flavour factory at very high luminosity with low beam currents and reduced background possibly located at Tor Vergata University. The SuperB accelerator design requires a careful choice of beam parameters to reach a good trade-off between different effects. We present here simulation results for the Touschek backgrounds and lifetime obtained for the latest machine design. Distributions of the Touschek particle losses at the at the interaction region have been tracked into the detectors for further investigations. A set of collimators is foreseen to stop Touschek particles. Their position along the rings has also been studied, together with their shape optimization.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Optimization of dynamic and momentum aperture is one of the most challenging problems in storage ring design. For storage-ring-based x-ray sources, large dynamic aperture is sought primarily to obtain high injection efficiency, which is important in efficient operation but also in protecting components from radiation damage. X-ray sources require large momentum aperture in order to achieve workable Touschek lifetimes with low emittance beams. The most widely applied method of optimizing these apertures is to minimize the driving terms of various resonances. This approach is highly successful, but since it is based on perturbation theory, it is not guaranteed to give the best result. In addition, the user must somewhat arbitrarily assign weights to the various terms. We have developed several more direct methods of optimizing dynamic and momentum aperture. These have been successfully applied to operational and design problems related to the Advanced Photon Source and possible upgrades.
CERN, Geneva
For several years, a large variety of beams have been prepared in the LHC injectors, such as single-bunch and multi-bunch beams, with 25 ns, 50 ns and 75 ns bunch spacings, nominal and intermediate intensities per bunch. As compared to the nominal LHC beam (i.e. with nominal bunch intensity and 25 ns spacing) the other beams can be produced with lower transverse emittances. Beams of low transverse emittances are of interest during the commissioning phase for aperture considerations and because of the reduced long-range beam-beam effects. On the other hand machine protection considerations might lead to prefer nominal transverse emittances for safe machine operations. The purpose of this paper is to present the results of controlled transverse emittance blow-ups using the transverse feedback and octupoles. The procedures tested in the SPS in 2008 allow to tune the transverse emittances up to nominal values at SPS extraction.
NSCL, East Lansing, Michigan
LBNL, Berkeley, California
Funding: U.S. Department of Energy
A driver linac has been designed for the proposed Facility for Rare Isotope Beam (FRIB) at Michigan State University. FRIB is a lower cost and reduced scope alternative to the Rare Isotope Accelerator (RIA) project. The superconducting driver linac will accelerate stable isotope beams to energies ≥200 MeV/u with a beam power up to 400 kW for the production of rare isotope beams. The driver linac consists of a front-end and two segments of superconducting linac connected by a charge stripping station. End-to-end beam simulation studies with high statistics have been performed using the RIAPMTQ and IMPACT codes on high performance parallel computers. These studies include misalignment of beam elements, rf amplitude and phase errors for cavities, and thickness variation of the stripping foil. Three-dimensional fields of the superconducting solenoids and cavities were used in the lattice evaluation. The simulation results demonstrate good driver linac performance. No uncontrolled beam losses were observed even for the challenging case of multiple charge state uranium beam acceleration. The beam dynamics issues will be discussed and the detail beam simulation results presented.
Northern Illinois University, DeKalb, Illinois
ANL, Argonne
Funding: M.R. and P.P. was supported by the US DOE under Contracts No. DE-FG02-08ER41532 with NIU. W.G. and J.P are supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 with ANL.
Transverse to longitudinal phase space manipulation hold great promises, e.g., as a potential technique for repartitioning the emittances of a beam. A proof-of-principle experiment to demonstrate the exchange of a low longitudinal emittance with a larger transverse emittance is in preparation at the Argonne Wakefield Accelerator using a 15 MeV electron beam. In this paper we explore the limiting effects of this phase space manipulation method associated to high order optics and collective effects. A realistic start-to-end simulation of the planned proof-of-principle experiment including jitter studies is also presented.
BINP SB RAS, Novosibirsk
The beam is injected into the CLIC damping ring with the relatively large emittance and energy spread and then is damped to the extremely low phase volume. During the damping process the betatron frequency of each particle changes due to the space charge tune shift and nonlinear detuning produced by the chromatic sextupoles, wiggler nonlinear field components and by the space charge force. During the damping, the particle cross resonances, which can trap some fraction of the beam, cause the loss of intensity, the beam blow up and degrade the beam quality. In this paper we study the evolution of the beam distribution in time during the damping.
TRIUMF, Vancouver
CERN, Geneva
The Lie-algebraic method is used to develop generalized Courant-Snyder invariant in the presence of an arbitrary number of beam-beam collisions, head-on or long-range, in a storage ring collider. The invariant is obtained by concatenating nonlinear beam-beam maps in the horizontal plane and to first order in the beam-beam parameter. Tracking evidence is presented to illustrate that with LHC parameters the invariant is indeed preserved and can be used to predict the smear of horizontal emittance observed in tracking simulations. We discuss the limits of applicability of this model for realistic LHC collision schemes.
ORNL, Oak Ridge, Tennessee
Funding: *SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
The new SNS Allison emittance scanner measures emittances of 65 kV ion beams over a range of ± 116 mrad. Its versatile control system allows for time-dependent emittance measurements synchronized by an external trigger, and therefore is suited for studying pulsed systems. After a programmable delay the system acquires a variable array of beam current measurements, each averaged over a changeable time span. The baseline of the current measurements are determined by averaging a fraction of 1 ms shortly before the start of the ion beam pulse. This paper presents the time evolution of emittance ellipses during the 1 ms H- beam pulses emerging from the SNS test LEBT, which is important for loss considerations. In addition it presents the time evolution of emittance ellipses during the 3 week active lifetime of an SNS H- source, which is an operational issue. Additional emittance data characterize the dependence on the electron-dump voltage, the extractor voltage, and the LEBT lens voltages, all of which were critical for reaching the 38 mA baseline H- beam current. Emittance data for the dependence on the beam current highlight the challenges for the SNS power upgrade.
SLAC, Menlo Park, California
KEK, Ibaraki
Life Imaging Technology, Palo Alto, California
Funding: Work sponsored by U.S. Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.
A two-slit interferometer has been installed in the SPEAR3 diagnostic beam line to measure vertical beam size at a dipole source point. The diagnostic beam line accepts unfocused, visible light in a 3.5 x 6.0 mrad aperture so that at the slit location 17 m from the source, the vertical extent of the beam is 100mm. For typical source sizes of sigy~15 um (0.1% emittance coupling) a slit separation of 80 mm produces fringe visibility of order V=0.5. Hence a significant plot of fringe visibility vs. slit separation can be generated to infer source size via Fourier transformation. In this paper we report on the interferometer construction, beam size measurement and potential deficiencies of the system, and compare with theoretical results.
USP/LAL, Sao Paulo
Funding: FAPESP, CNPq
In this work we describe a model to study the effect of charge saturation in phosphor screens in the determination of electron beam profiles. It is shown that the charge saturation introduces systematic errors in the beam diameter determination, since it tends to increase the observed beam diameter. The study is made supposing a Gaussian beam profile and a saturation model to the charge response of the phosphor material. The induced errors increase for higher currents and/or narrow beams. A possible correction algorithm that can be applied to some measurements is presented, together with a brief discussion about the consequences of these systematic errors in emittance measurements.
UCR, Riverside, California
The Muon Ionization Cooling Experiment (MICE) is being built at the Rutherford Appleton Laboratory (RAL) to test ionization cooling of a muon beam. Successful demonstration of cooling is a necessary step along the path toward creating future high intensity muon beams in either a neutrino factory or muon collider. MICE will reduce the transverse emittance of the beam by 10%, and spectrometers using particle physics techniques will measure the emittance reduction with an absolute precision of 0.1%. This measurement will be done with scintillating fiber tracking detectors nested inside solenoid magnets on either side of the cooling channel. Each fiber tracker contains five stations with 3 layers of fibers rotated 120 degrees with respect to each other, thereby allowing reconstruction of hit points along the path of the muons. Light is carried from the active fiber volume by clear waveguide fibers where it is detected using VLPCs (Visible Light Photon Counters). The details of the tracker commissioning using cosmic rays will be discussed in addition to the status and performance of the readout electronics*.
*Submitted on behalf of the MICE collaboration.
UMD, College Park, Maryland
ANL, Argonne
Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office.
Single foil OTR and two foil OTR interferometry have been successfully used to measure the size and divergence of electron beams with a wide range of energies. To measure rms emittance, two cameras are employed: one focused on the foil to obtain the spatial distribution of the beam, the other focused to infinity to obtain the angular distribution. The beam is first magnetically focused to a minimum size in directions which are orthogonal to the propagation axis, using a pair of quadrupoles. Then simultaneous measurements of the rms size (x,y) and divergence (x’,y’) of the beam are made. However, in the process of a quadrupole scan, the beam can go through a spot size minimum, a divergence minimum and a waist, i.e. the position where the cross-correlation term is zero. In general, the beam size, divergence and focusing strength for each of these conditions are different. We present new algorithms that relate the beam and magnetic parameters to the rms emittance for each of these three cases. We also compare the emittances, obtained using our algorithms and measurements made at the ANL AWA facility, with those produced by computer simulation.
USTC/NSRL, Hefei, Anhui
The strip-line beam position monitor can be used as a non-intercepting emittance measurement monitor. The most important part of emittance measurement is to pick up the quadrupole component. To improve the accuracy of measurement, the response of the strip-line BPM pickups will be mapped before it’s installed in the HLS LINAC. This paper introduce the calibration system of the BPM, which consists of a movable antenna and a RF signal source, simulating the beam , a BPM moving bench with its control system, and an electronics system. When the position calibration is done first, the offset between electronic center and mechanical one of the BPM and the position sensitivity are gotten. There are two methods for quadrupole component calibration: one is indirect evaluation method that estimates the sensitivity of quadrupole component by the factor of position second moment; the other is direct method by simulation of a Gaussian beam through together many Gaussian weighted grid points. The results of two methods are given and compared. The effect of antenna’s diameter upon the fitting size of simulate beam has also been analyzed.
USTC/NSRL, Hefei, Anhui
A high brightness injector has been developing in HLS (Hefei Light Source), and the design of beam parameter measurement system is presented in this paper. The whole system will measure beam position, beam current, emittance of beam, bunch length, beam energy and energy spread. For the beam position, we have designed three types of BPMs: stripline BPM, with the resolution of 20 μm; cavity BPM, with the resolution of 10 μm, and resonant stripline BPM*. The beam position processor Libera will be used. The beam current will measured using the ICT and FCT. When going out of the gun, the energy of the beam is about 4MeV – 5MeV, and the emittance of the beam is charge-dominated, so we use a set of slits with the width of 90 μm to split the beam to beamlets. The bunch length is measured using OTR and streak camera. Before entering the bending magnet, the beam will go pass a very narrow slit, with the width of 90 μm, and the resolution of energy spread will be improved.
*M.Dehler, “Resonant Strip line BPM for Ultra Low Current Measurements”, Proceedings of DIPAC 2005, Lyon, France, p.286-288
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source storage ring has several bunch fill patterns for user operation. In some fill patterns the single-bunch beam charge is as high as 16 mA. We installed a bunch-to-bunch feedback system that aims to overcome high-charge beam instability and reduce the required chromatic correction. Due to the drive strength limitation, we decided to first commission the feedback system in the vertical plane. We present our preliminary results, some of the issues that we have experienced and resolved, and our plan to expand the system to the horizontal plane.
INFN/LNF, Frascati (Roma)
The SuperB project consists of an asymmetric (4x7 GeV), very high luminosity, B-Factory to be built at Roma-II University campus in Italy, with the ambitious luminosity goal of 1036 cm-2 s-1. To achieve the very challenging performances, robust and powerful bunch-by-bunch feedback systems are necessary to cope with fast coupled bunch instabilities in rings with high beam currents and very low emittances. The SuperB bunch by bunch feedback should consider the rich legacy of previous systems, the longitudinal (DSP-based) feedback built in 1993-97 and the recent “iGp” feedback system designed in 2002-06. Both were designed by large collaborations between Research Institute (SLAC, DAΦNE@LNF/INFN, ALS@LBNL, KEK). The core of the new system will be the digital processing module, based on powerful FPGA components, to be used in longitudinal and transverse planes. Off-line analysis programs, as well real-time diagnostic tools, will be included. The feedback impact on very low emittance beams have to be carefully considered. A MATLAB simulator based on a beam/feedback model is also foreseen for performance checks and fast downloads of firmware/gateware code and parameters.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Excellent phase stability of the drive laser is a critical performance specification of photoinjectors such as Fermilab’s A0 photoinjector (A0PI). Previous efforts based on the measurement of the power spectrum of the signal of a fast photodiode illuminated by the mode locked infra-red laser pulse component indicated a phase jitter of less than 1.4 ps (technique limited). A recently procured dual-sweep plugin unit and existing Hamamatsu C5680 streak camera were used to study the phase stability of the UV laser pulse component. Initial measurements with the synchroscan vertical sweep unit locked to 81.25 MHz showed that the phase slew through the micropulse train and the phase jitter micropulse to micropulse were two key aspects that could be evaluated. The phase slew was much less than 100 fs per micropulse, and the total phase jitter (camera, trigger, and laser) was approximately 300 fs RMS for measurements of 20-micropulse trains. Data on the macropulse phase stability were also obtained. A possible upgrade to achieve better phase stability will be also discussed.
NSRRC, Hsinchu
The 266 nm UV drive laser for the NSRRC 2998 MHz photo-injector system is generated from a nonlinear optical crystal that is driven by a 798 nm, 3.5 mJ Ti:Sapphire laser amplifier system. Synchronization of the seed laser pulses with the master oscillator of the photo-injector high power microwave system is done by locking the laser to the rf clock signal with time jitter of less than a picosecond. A detector circuit is being built to measure this jitter at sub-picosecond time resolution. Preliminary results of this jitter measurement electronics that have been tested with artificial signals are presented.
CERN, Geneva
The CLIC study is exploring the scheme for an electron-positron collider with a centre-of-mass energy of 3 TeV in order to make the multi-TeV range accessible for physics. The current goal of the project is to demonstrate the feasibility of the technology by the year 2010. Recently, important progress has has been made concerning the high-gradient accelerating structure tests and the experiments with beam in the CLIC test facility, CTF3. On the organizational side, the CLIC international collaborations have significantly gained momentum considerably boosting the CLIC study.
CLASSE, Ithaca, New York
LBNL, Berkeley, California
KEK, Ibaraki
ANL, Argonne
Fermilab, Batavia
CalPoly, San Luis Obispo, CA
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
SLAC, Menlo Park, California
Cornell University, Ithaca, New York
Cockcroft Institute, Warrington, Cheshire
Funding: Support provided by the US National Science Foundation, the US Department of Energy, and the Japan/US Cooperation Program.
In March of 2008, the Cornell Electron Storage Ring (CESR) concluded twenty eight years of colliding beam operations for the CLEO high energy physics experiment. We have reconfigured CESR as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D. The primary goals of the CesrTA program are to achieve a beam emittance approaching that of the ILC Damping Rings with a positron beam, to investigate the interaction of the electron cloud with both low emittance positron and electron beams, to explore methods to suppress the electron cloud, and to develop suitable advanced instrumentation required for these experimental studies (in particular a fast x-ray beam size monitor capable of single pass measurements of individual bunches). We report on progress with the CESR conversion activities, the status and schedule for the experimental program, and the first experimental results that have been obtained.
KEK, Ibaraki
The University of Liverpool, Liverpool
SLAC, Menlo Park, California
One of the goals of the Accelerator Test Facility (ATF) at KEK is to demonstrate ultra-low vertical emittance for linear colliders. Highly precise correction of the vertical dispersion and betatron coupling will be needed to achieve the target of 2 pm (which will be required for ILC). Optics correction and tuning must be supported by an accurate model, which can be developed from a variety of beam measurements, including orbit response to dipole kicks, beta functions at the quadrupoles, etc. Here, we report experimental data and the status of the model and low-emittance tuning.
CERN, Geneva
An LHC high-luminosity upgrade has been studied by various European and international collaborations since about 2001. Ingredients of such an LHC upgrade include the optimization of the IR layout, new high-field or large-aperture triplet quadrupoles, chromatic correction, possibly detector-integrated slim magnets, crab cavities, beam-beam compensators, operation in a regime of large Piwinski angle, luminosity leveling for reduced detector pile up, heat-load, background, and radiation damage due to the collision debris, and a renovation of the injector complex. Scenarios, decision paths, and present R&D efforts will be presented.
CERN, Geneva
N.U, Nigde
Cockcroft Institute, Warrington, Cheshire
Ankara University, Faculty of Sciences, Tandogan/Ankara
The University of Liverpool, Liverpool
KEK, Ibaraki
TOBB ETU, Ankara
BNL, Upton, Long Island, New York
Sub-atomic physics at the energy frontier probes the structure of the fundamental quanta of the Universe. The Large Hadron Collider (LHC) at CERN opens for the first time the “terascale” (TeV energy scale) to experimental scrutiny, exposing the physics of the Universe at the sub-attometric (~10-19 m, 10-10 as) scale. The LHC will also take the science of nuclear matter to hitherto unparalleled energy densities (low-x physics). The hadron beams, protons or ions, in the LHC underpin this horizon, and also offer new experimental possibilities at this energy scale. A Large Hadron electron Collider, LHeC, in which an electron (positron) beam of energy (70 to 140 GeV) is in collision with one of the LHC hadron beams, makes possible terascale lepton-hadron physics. The LHeC is presently being evaluated in the form of two options, “ring-ring” and “linac-ring”, either of which operate simultaneously with pp or ion-ion collisions in other LHC interaction regions. Each option takes advantage of recent advances in radio-frequency, in linear acceleration, and in other associated technologies, to achieve ep luminosity as large as 1033 cm-2s-1.
BNL, Upton, Long Island, New York
ANL, Argonne
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
After installation of two partial snakes in the Brookhaven Alternating Gradient Synchrotron (AGS), a polarized proton beam with 1.5*1011 intensity and 65% polarization has been achieved. There are residual polarization losses due to horizontal resonances over the whole energy ramp and some polarization loss due to vertical intrinsic resonances. Many efforts have been put in to reduce the emittances coming into the AGS and to consequently reduce polarization loss. This paper presents the accelerator setup and preliminary results from run-9 operations.
CAEP/IFP, Mainyang, Sichuan
TUB, Beijing
CAEP/IAE, Mianyang, Sichuan
It has been three decades since the research and development of key technologies and components started at the Institute of Fluid Physics, CAEP, for the linear induction accelerator (LIA). The first LIA was built in 1989 with beam parameters of 1.5 MeV, 3 kA and pulse width of 90 ns. Later the SG-I LIA (3.3 MeV, 2 kA, 90 ns) was developed for FEL in 1991. The first Linear Induction Accelerator X-Ray Facility (LIAXF, 10 MeV, 2 kA, 90 ns, spot size about 6 mm in diameter) was built in 1993 and upgraded to 12 MeV with higher performance (LIAXFU, 12 MeV, 2.5 kA, 90 ns, spot size about 4 mm in diameter) in 1995. The Dragon-I LIA with the best quality (20 MeV, 2.5 kA, 80 ns, spot size about 1 mm in diameter) in the world was finished in 2003. The smallest LIA with double pulses separated by 300 ns (MiniLIA, 200 keV, 1 A, 80 ns) was developed in 2007 for beam physics studies.
KEK, Ibaraki
KURRI, Osaka
Harmonic number jump (HNJ) acceleration in scaling FFAG accelerator, especially for muon acceleration in neutrino factory, has been studied. Criterions for HNJ acceleration were clarified and beam tracking simulations have been carried out.
LAL, Orsay
IN2P3-LAPP, Annecy-le-Vieux
KEK, Ibaraki
UMAN, Manchester
SLAC, Menlo Park, California
Funding: CNRS/IN2P3 ANR (Programme Blanc, Project ATF2-IN2P3-KEK, contract ANR-06-BLAN-0027)
The orbit in the ATF2 extraction line has to be accurately controlled to allow orbit and optics corrections to work well downstream. The Final Focus section contains points with large beta function values which amplify incoming beam jitter, and few correctors since the steering is performed using quadrupole movers, and so good orbit stability is required. It is also essential because some magnets are non-linear and can introduce position-dependent coupling of the motion between the two transverse planes. First experience monitoring the orbit in the extraction line during the ATF2 commissioning is described, along with a simulation of the planned steering algorithm.
LAL, Orsay
KEK, Ibaraki
SLAC, Menlo Park, California
Funding: CNRS-IN2P3, ANR
The purpose of ATF2 is to deliver a beam with stable very small spotsizes as required for future linear colliders such as ILC or CLIC. To achieve that, precise controls of aberrations such as dispersion and coupling are necessary. Initially, coupling correction upstream of the final focus line of the ATF2 will be performed with only two skew quadrupoles (SQ) in the extraction line (EXT). We thus first examine the feasability of coupling correction in the EXT with those two SQ, considering several possible coupling error sources. The correction is first based on an algorithm of minimisation of vertical emittance with successive skew scans, implemented in the Flight Simulator code*. We will then investigate new methods to measure and extract the first order four coupling parameters of the beam matrix in order to perform a more direct and accurate coupling correction.
*G. White et al., "A flight simulator for ATF2…", TUPP016 EPAC08
NSCL, East Lansing, Michigan
SLAC, Menlo Park, California
Determination of exact values of beam emittance is important for future linear collider. Beam emittance measurements technique is based on measurement of beam sizes at several beam profile stations in a quadrupole channel shifted between each other by a specific value of phase advance of betatron oscillations. Four-dimensional beam emittance measuremenst requires determination of ten values of the beam σ-matrix, while two-dimensional beam emittance measurements scheme requires determination of six values of σ-matrix. Measurement procedure is sensitive to variation of beam sizes at the beam profile stations, which might result in unstable determination of beam emittance. Paper discusses errors of beam emittance measurements as a function of errors in beam size measurement. Regions of stable and unstable beam emittance measurements are determined.
NSCL, East Lansing, Michigan
Funding: This work was supported by Michigan State University and the National Science Foundation under grant PHY-0110253.
The NSCL at Michigan State University (MSU) is implementing a system called the ReA3 to reaccelerate rare isotope beams from projectile fragmentation to energies of about 3 MeV/u. The re-acceleration system uses an Electron Beam Ion Trap (EBIT) to provide a compact and cost efficient system. We discuss the design parameters for a m/q separator that is to be used to separate highly charged ions from an EBIT type charge breeder. The separator is designed to accept ions at 12 keV/u with mass to charge ratios in the range of m/q = 2.5 to 5 amu. The goal is to separate selected rare isotope species from any residual ions before injecting them into the ReA3 linear accelerator system. Using ray tracing simulations with SIMION*, as well as higher order map calculations with COSY INFINITY**, the performance of the separator has been evaluated in terms of the expected mass resolution and overall acceptance. The separator consists of a magnetic sector and a series of electrostatic devices to obtain a first order achromatic tune. For comparison, similar performance values will be derived as those for a similar separator constructed at REX-ISOLDE***.
*D.A. Dahl, Int. J. Mass Spectrom. Ion Processes 200, 3 (2000) .
**K. Makino and M. Berz, Nucl. Instr. and Meth. A 558, 346 (2005)
***R. Rao et. al., EPAC-98, Stockholm, Sweden, 2132-2134 (1998).
Rutgers University, The State University of New Jersey, Piscataway, New Jersey
Fermilab, Batavia
BNL, Upton, Long Island, New York
A transverse to longitudinal emittance exchange experiment is installed at the Fermilab A0 Photoinjector. We report on the completed measurement of emittance exchange transport matrix as well as the ongoing program to directly measure the emittance exchange. Both the transverse and longitudinal input beam parameters are being explored in order to achieve direct emittance exchange with minimal dilution effects
SLAC, Menlo Park, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
KEK, Ibaraki
LAL, Orsay
UMAN, Manchester
CERN, Geneva
Funding: Work supported in part by Department of Energy Contract DE-AC02-76SF00515
Using a new extraction line currently being commissioned, the ATF2 experiment plans to test a novel compact final focus optics design using a local chromaticity correction scheme, such as could be used in future linear colliders*. Using a 1.3 GeV beam of ~30nm normalised vertical emittance extracted from the ATF damping ring, the primary goal is to achieve a vertical IP waist of 35nm. We discuss our planned strategy, implementation details and early experimental results for tuning the ATF2 beam to meet the primary goal. These optics require uniquely tight tolerances on some magnet strengths and positions, we discuss efforts to re-match the optics to meet these requirements using high-precision measurements of key magnet elements. We simulated in detail the tuning procedure using several algorithms and different code implementations for comparison from initial orbit establishment to final IP spot-size tuning. Through a Monte Carlo study of 100's of simulation seeds we find we can achieve a spot-size within 10% of the design optics value in at least 90% of cases. We also ran a simulation to study the long-term performance with the use of beam-based feedbacks.
*"ATF2 Proposal", ATF2 Collaboration (Boris Ivanovich Grishanov et al.)., KEK-REPORT-2005-2, Aug 23, 2005.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
A scaling fixed field alternating gradient (FFAG) accelerator provides large momentum acceptance despite of constant field in time. Optical functions are nearly the same for large momentum range. We have designed a straight beam transport (BT) line using a scaling FFAG type magnet which has a field profile of x^k, where x is the horizontal coordinate and k is the field index. This BT line has very large momentum acceptance as well, for example ±50%, and optical functions do not practically depends on momentum. We also designed a dispersion suppressor at the end by the combination of a unit cell with different field index k so that the momentum dependence of orbits should be eliminated at the exit. An obvious application of this design is the BT line between FFAG accelerator and gantry of a particle therapy facility. However, we also consider it for the transport of muon beams, which have large emittance and momentum spread. This could be an alternative to the conventional BT line with solenoid or quadrupole because of the strong focusing nature of quarupole and the large momentum acceptance like solenoid.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Results of designing of the extended ALICE injector with the aim to include a special dedicated diagnostic line are presented. The purpose of the diagnostic line is to characterise the low energy beam, before it enters the booster, as much as possible. A key component of the ALICE is the high brightness injector. The ALICE injector consists of a DC photocathode gun generating ~ 80 pC electron bunches at 350 keV. These bunches are then matched into a booster cavity which accelerates them to an energy of 8.35 MeV. In order to do this, three solenoids and a single-cell buncher cavity are used, together with the off-crest of the first booster cavity where the beam is still far from being relativistic. The performance of the injector has been studied using the particle tracking code ASTRA.
SLRI, Nakhon Ratchasima
For the SIAM Photon Source, we propose to establish a storage ring model based on quadrupole fitting of the measured betatron functions. By fitting of quadrupole field strength parameters to measured values of the betatron function, a series of problems at the SIAM Photon Source could be determined. For example, the problem of turn-to turn electrical coil shorts was detected and solved by replacing the new quadrupole coils. Subsequently, we could identify a quadrupole calibration error due to conflicting information on the number of turns per coil. Other causes regarding the beam dynamics model such as high field saturation effects, power supply calibration error, and proximity to nearby magnets have been taken into account to establish accurate quadrupole calibration factors. The establishment of an accurate model is essential for beam dynamics predictions, closed orbit correction, response matrix determination for LOCO, low emittance operation, and optics correction for high filed insertion devices.
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
The specified vertical emittance for the ILC damping rings is 2 pm. A major objective for the Accelerator Test Facility (ATF) at KEK is to demonstrate reliable operation in this low emittance regime. LOCO is a tool for identifying optics errors in storage rings, based on fitting a lattice model to the measured closed orbit response matrix. This technique can be used to determine corrections to minimise vertical dispersion and betatron coupling, and hence reduce the vertical emittance. So far, efforts to apply LOCO to the ATF to achieve 2 pm vertical emittance have met with limited success. This paper presents the results of simulations aiming to identify possible limitations in the technique. We consider the effects of varying parameters controlling the fit of the lattice model to the measured data, and investigate possible degeneracies (e.g. between skew quadrupole strengths and tilts of the corrector magnets) that may limit the quality of the correction achievable using this technique.
TUB, Beijing
Funding: This work is supported by National Natural Science Foundation of China (Project 10735050) and National Basic Research Program of China (973 Program) (Grant No. 2007CB815102).
The feasibility study of optical stochastic cooling (OSC) utilizing a compact storage ring is presented in this paper. We present the general layout of the scheme, as well as the lattice design of the storage ring. The results of beam dynamics simulation are likewise presented.
UCR, Riverside, California
Funding: Work supported by the United States Department of Energy under Grant No. DE-FG02-07ER41487.
The RFOFO ring is considered to be one of the most promising six-dimensional cooling channels proposed for the future Muon Collider. It has a number of advantages over other cooling channels, but also certain drawbacks. The injection and extraction, the absorber overheating, and the bunch train length are among the main issues. A number of simulations of a possible solution to these problems, the RFOFO helix, commonly referred to as the Guggenheim channel, were carried out and their results are summarized. The issue of the RF breakdown in the magnetic field is addressed, and the preliminary results of the simulation of the lattice with magnetic coils in the irises of the RF cavities are presented.
MIT/PSFC, Cambridge, Massachusetts
Funding: This work was supported by the Department of Energy, Grant No. DE-FG02-95ER40919 and the Air Force Office of Scientific Research, Grant No. FA9550-06-1-0269.
An adiabatic warm-fluid equilibrium theory for a thermal charged-particle beam in an alternating gradient (AG) focusing field is presented. Warm-fluid equilibrium equations are solved in the paraxial approximation and the rms beam envelope equations and the self-consistent Poisson equation, governing the beam density and potential distributions, are derived. The theory predicts that the 4D rms thermal emittance of the beam is conserved, but the 2D rms thermal emittances are not constant. Although the presented rms beam envelope equations have the same form as the previously known rms beam envelope equations, the evolution of the rms emittances in the present theory is given by analytical expressions. The beam density is calculated numerically, and it does not have the simplest elliptical symmetry, but the constant density contours are ellipses whose aspect ratio decreases as the density decreases along the transverse displacement from the beam axis. For high-intensity beams, the beam density profile is flat in the center of the beam and falls off rapidly within a few Debye lengths, and the rate at which the density falls is approximately isotropic in the transverse directions.
Nagaoka University of Technology, Nagaoka, Niigata
TIT, Yokohama
Possible emittance growth due to a nonuniform particle distribution can be analyzed with a thermal equilibrium state in various space-charge potential beams. The possible emittance growth is given by a function of a space-charge tune depression and a nonlinear field energy factor. The nonlinear field energy factor, which is determined by nonuniformity of a charge distribution, is estimated in the thermal equilibrium distribution on a cross-section in a beam. The nonlinear field energy factor changes with space-charge potential for the thermal equilibrium distribution. It is expected that the possible emittance growth will be decreased effectively to consider in the thermal equilibrium condition.
Northern Illinois University, DeKalb, Illinois
ANL, Argonne
A transverse-to-longitudinal emittance exchange experiment is in preparation at the Argonne Wakefield Accelerator (AWA). The experiment aims at exchanging a low (< 5 mm-mrad) longitudinal emittance with a large (>15 mm-mrad) transverse horizontal emittance for a bunch charge of 100 pC. Achieving such emittance partitioning, though demonstrated via numerical simulations, is a challenging task and need to be experimentally verified. In this paper, we report emittance measurements of the beam in the transverse and longitudinal planes performed at 12 MeV. The measurements are compared with numerical simulations using Impact-T.
Pulsar Physics, Eindhoven
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
TUE, Eindhoven
The required strengths of quadrupoles in a phase-space tomography section are significantly affected by the total charge per bunch. Finding settings at a high charge is challenging because of the non-linear nature of Coulomb interactions. This is further hindered by the inability to use thin-lens approximations and dependence on numerical simulations. Finally, one faces the problem that at some charge there simply is no solution at all. In this contribution we describe a simple procedure, implemented in the General Particle Tracer (GPT) code, which can be used to find optimal beamline settings in the presence of space-charge forces. The recipe 'transports' the settings for a zero-charge solution to those of the desired charge and it gives an indication what the maximum tolerable charge is.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a 50 Hz proton synchrotron, which accelerates ~3·1013 ppp from 70 to 800 MeV, corresponding to beam powers of 0.2 MW. Beam loss imposes limits on operational intensity, and a main contributing mechanism is the action of half integer resonance under high space charge. The same loss mechanism is also a potential problem in ISIS upgrade scenarios involving either higher energy injection into the existing ring, or the addition of a new 3 GeV, high intensity RCS. Progress on particle in cell simulation studies investigating the effects of the driven coherent envelope motion, the associated parametric halo, along with implications of momentum spread, dispersion and longitudinal motion, is reported. Where possible, comparisons are made with relevant theoretical models. Closely related benchmarking work, experimental studies and plans are also summarised.
IF-UFRGS, Porto Alegre
Non-homogeneity is a characteristic naturally present in non-neutral beams. Recently, a set of works has been developed by us for the case of beams initially homogeneous, making possible that relevant macroscopic quantities such as the RMS radius and emittance could be determined at equilibrium as functions of characteristic parameters of beam phase-space and of initial conditions. The present work intends to investigate the influences of the initial inhomogeneity in the beam route to equilibrium. Through the same methodology introduced in the studies for the homogeneous beams, both emittance and beam envelope have been obtained as functions of the magnitude of the inhomogeneity and some additional parameters associated with geometry of beam phase-space. The results obtained with this investigation have proven to be useful not only to better understand the effects of inhomogeneity over beam dynamics but also to provide physical background to the investigations previously carried out for homogeneous beams.
IF-UFRGS, Porto Alegre
Experiments and numerical simulations show that high-intensity beams composed by charged particles usually reach their final stationary state with a progressive populating of a spatial region external to its original border. This populating process occurs in such terms that beam spatial limits at equilibrium increase by an amount of two or three times its initial nominal size. This is known as halo in Beam Physics. In this way, this work intends to better understand the time scale of halo formation. The carried out investigation has shown that the time scale of halo formation in fact can be segmented in two different quantities, each one associated to distinct physical mechanisms. One is related with the initial non-homogeneity naturally present in such systems, and the other is a result of the initial beam envelope mismatch. This investigation seems to be useful to design more efficient collimation systems and/or non-linear control systems for the next generation high-power accelerators.
IF-UFRGS, Porto Alegre
Funding: CNPq, Brazil; AFOSR FA9550-06-1-0345, USA
In this work we analyze the dynamics of mismatched inhomogeneous beams of charged particles. Initial inhomogeneities lead to propagating density waves across the beam core, and the presence of density waves eventually results in density build up and particle scattering. Particle scattering off waves in the beam core and the presence of resonances due to envelope mismatches ultimately generate a halo of particles with concomitant emittance growth. Emittance growth directly indicates when the beam relaxes to its final stationary state, and the purpose of the present paper is to describe halo and emittance in terms of test particles moving under the action of the mismatched inhomogeneous beam. To this end we develop an average Lagrangian approach for the beam where both density and envelope mismatches are incorporated. Test particle results compare well with full simulations.
IF-UFRGS, Porto Alegre
The question is whether an anisotropic system of collisionless particles coupled by long-range space-charge forces will equipartition and, if so, how. Results show that collective effects tend to cause an initial beam with strongly nonuniform density to relax, rapidly, to a state that is equlibrium-like. In order to understand the initial dynamical behavior of an anisotropic beams, in particular, to study possible mechanisms of equipartition connected with phase space we have to know how we can compute the variables (volume, area of surface, and area projected) that characterize the anisotropic beam in phase space. The purpose of this paper is to propose one definiton of the anisotropic equipartition. In the state of anisotropic equipartition, the temperature is stationary, the entropy grows in the cascade form, there is a coupling of transversal emittance, the beam develops an elliptical shape with a increase in its size along one direction and there is halo formation along one direction preferential.
UCLA, Los Angeles, California
The velocity bunching is a hot topic in normal conducting photoinjectors to generate high-brightness beams instead of magnetic chicanes in the low energy region. We apply this technique to the superconducting photoinjectors. The linac considered here consists of several 9-cell TESLA cavities, the standard 1.6-cell normal conducting RF gun is assumed, though. In the case of 1.1 nC injection, the peak current increases to 1 kA with 2.6 mm.mrad of the emittance. The peak current can be higher but the emittance becomes worse in that case, and vice versa. We discuss more details on the spot.
UMD, College Park, Maryland
Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office
The University of Maryland Electron Ring (UMER) can operate over a broader range of beam intensities than other circular machines. Naturally, transverse and longitudinal space charge effects limit the ability to store beams. In UMER, the resonance properties of the machine in the two regimes of operation, emittance- and space charge-dominated transport, differ significantly. We report on studies of linear betatron resonances in UMER from 0.6 mA to 80 mA beam current, corresponding to theoretical space charge incoherent tune shifts well over the Lasslet limit. The observations are related to existing theories as well as to computer simulations. We also describe the instrumentation and techniques used for tune measurements.
UMD, College Park, Maryland
Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office.
Understanding the dynamics of the acceleration of high-intensity space-charge-dominated electron and ion beam is very important. Accelerating by steps a space-charge-dominated beam can be fundamentally different from beams at lower intensities, because at sufficiently high beam intensities the beam response to acceleration can drive to some unknown instabilities leading to a significant beam losses. This work analyses the acceleration of the University of Maryland Electron Ring (UMER) beam, i.e., high current, low-energy and space-charge-dominated electron beam which is applicable, on a scale basis, to a large class of other beam systems. We use the WARP particle-in-cell code to perform simulations that are compared with theoretical predictions and preliminary experimental results.
UMD, College Park, Maryland
BNL, Upton, Long Island, New York
Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office
Beam matching is critical for avoiding envelope mismatch oscillations that can lead to emittance growth and halo formation, especially if the beam has significant space charge. The University of Maryland Electron Ring (UMER) is a research storage ring that is designed for scaled studies that are applicable to many larger machines. Using 10 keV electron beams at relatively high current (0.6 – 100 mA), space charge forces are relatively strong. Matching of the UMER beam is rendered difficult by the space charge, the crowdedness of the lattice, and especially the unique injection scheme where an offset oversized quadrupole is shared between the ring and the injector. In this paper we discuss several schemes for optimizing the matching at injection, both analytical and beam-based, which we test using particle-in-cell simulations with the code, WARP. Comparison to UMER experimental data is provided where available.
UMD, College Park, Maryland
Funding: *This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office
The University of Maryland Electron Ring (UMER) is designed for operation over a broad range of beam intensities, including those normally achieved only in linacs. This is possible thanks to a combination of low-energy (10 keV) electrons and a high density of magnetic quadrupoles (72 over an 11.5 m circumference) that allow operation from 0.5 mA to 100 mA; that is, from the emittance dominated to the highly space charge dominated regimes. We present results of basic centroid-motion characterization, including measurements of closed-orbit distortion, momentum compaction factor, and natural chromaticity and dispersion. These are compared with results from computer simulations employing the code ELEGANT. We discuss the techniques and challenges behind the measurements with fast beam-position and wall-current monitors, and also the special role of the background ambient magnetic field for beam steering.
YSU, Yerevan
CANDLE, Yerevan
PSI, Villigen
An online measurement of the beam energy spread is based on the analysis of the decoherence/recoherence signals obtained from the beam position monitors after a single turn beam excitation by a pinger magnet. Furthermore the analysis allows calibration of the model in terms of higher order chromaticities and amplitude dependant tune shifts. An analytical model including 1st and 2nd order chromaticities and amplitude dependant tune shift will be presented.
PSI, Villigen
LANL, Los Alamos, New Mexico
CIAE, Beijing
OPAL (Object Oriented Parallel Accelerator Library) is a tool for charged-particle optics in accelerator structures and beam lines including 3D space charge, short range wake-fields and a 1D coherent synchrotron radiation. Built from first principles as a parallel application, OPAL admits simulations of any scale, from the laptop to the largest HPC clusters available today. Simulations, in particular HPC (High Performance Computing) simulations, form the third pillar of science, complementing theory and experiment. In this paper we present numerical and HPC capabilities such as fast direct and iterative solvers together with timings up to several thousands of processors. The application of OPAL to our PSI-XFEL project as well as to the ongoing high power cyclotron upgrade will demonstrate OPAL's capabilities applied to ongoing projects at PSI. Plans for future developments will be discussed.
SLAC, Menlo Park, California
BNL, Upton, Long Island, New York
Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and used resources of NERSC supported by DOE Contract No. DE-AC02-05CH11231, and of NCCS supported by DOE Contract No. DE-AC05-00OR22725.
SLAC's Advanced Computations Department (ACD) has developed the parallel 3D Finite Element electromagnetic Particle-In-Cell code Pic3P. Designed for simulations of beam-cavity interactions dominated by space charge effects, Pic3P solves the complete set of Maxwell-Lorentz equations self-consistently and includes space-charge, retardation and boundary effects from first principles. Higher-order Finite Element methods with adaptive refinement on conformal unstructured meshes lead to highly efficient use of computational resources. Massively parallel processing with dynamic load balancing enables large-scale modeling of photoinjectors with unprecedented accuracy, aiding the design and operation of next-generation accelerator facilities. Applications include the LCLS RF gun and the BNL polarized SRF gun.
Tech-X, Boulder, Colorado
BNL, Upton, Long Island, New York
Funding: The work at Tech-X Corp. is supported by the U. S. Department of Energy under the DE-FG02-06ER84509 SBIR grant.
The Relativistic Heavy Ion Collider (RHIC) contributes fundamental advances to nuclear physics by colliding a wide range of ions. A novel electron cooling section, which is a key component of the proposed luminosity upgrade for RHIC, requires the acceleration of high-charge electron bunches with low emittance and energy spread. A promising candidate for the electron source is the recently developed concept of a high quantum efficiency photoinjector with a diamond amplifier. To assist in the development of such an electron source, we have implemented algorithms within the VORPAL particle-in-cell framework for modeling secondary electron and hole generation, and for charge transport in diamond. The algorithms include elastic, phonon, and impurity scattering processes over a wide range of charge carrier energies. Results from simulations using the implemented capabilities will be presented and discussed.
Tech-X, Boulder, Colorado
BNL, Upton, Long Island, New York
Funding: The work at Tech-X Corp. is supported by the US DoE under grant DE-FG02-06ER84509.
A promising new concept of a diamond amplified photocathode for generation of high-current, high-brightness, and low thermal emittance electron beams was recently proposed* and is currently under active development. To better understand the different effects involved in the generation of electron beams from diamond, we have been developing models (within the VORPAL computational framework) to simulate secondary electron generation and charge transport. The currently implemented models include inelastic scattering of electrons and holes for generation of electron-hole pairs, elastic, phonon, and charge impurity scattering. We will present results from 3D VORPAL simulations with these capabilities on charge gain as a function of primary electron energy and applied electric field. Moreover, we consider effects of electron and hole cloud expansion (initiated by primary electrons) and separation in a surface domain of diamond.
*I. Ben-Zvi et al., Secondary emission enhanced photoinjector, C-AD Accel. Phys. Rep. C-A/AP/149, BNL (2004).
Tech-X, Boulder, Colorado
Fermilab, Batavia
Funding: This work was supported by the US DOE Office of Science, Office of Nuclear Physics, under Grant No. DE-FG02-08ER85183
A new set of tools for BBSIM has recently been developed to analyze the nature of the diffusion in multi-particle simulations. The diffusion subroutines are currently used to accelerate beam lifetime calculations by estimating the diffusion coefficient at various actions and integrating the diffusion equation. However it is possible that there may be regimes where anomalous diffusion dominates and normal diffusion estimates are incorrect. The tools we have developed estimate the deviation from normal diffusion and can fit the coefficients of a jump diffusion model in the event that this type of diffusion dominates.
University of Delhi, Delhi
Fermilab, Batavia
It is well known that Insertion of a coupler into a RF cavity breaks the rotational symmetry of the cavity, resulting in an asymmetric field. This asymmetric field results in a transverse RF Kick*. This RF kick transversely offsets the bunch from the nominal axis & it depends on the longitudinal position of the particle in the bunch. Also, insertion of coupler generates short range transverse wake field** which is independent from the transverse offset of the particle. These effects cause emittance dilution and it is thus important to study their behavior & possible correction mechanisms. These coupler effects, i.e. coupler’s RF kick & coupler's wake field are implemented in a beam dynamics program, Lucretia. Calculations are done for Main Linac. For ILC like Lattices Results are compared with analytical results. and a good agreement has been found.
*N.Solyak et al, “RF Kick in the ILC Acceleration Structure. ” MOPP042.pdf (EPAC 08).
** N.Solyak et al, “Transverse Wake Field Simulation for the ILC Acceleration Structure”. MOPP043 pdf (EPAC 08).
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
Funding: Work supported by US Department of Energy.
At the BNL-ATF we have recently demonstrated the generation of trains of electron with sub-picosecond spacing*. These trains of equidistant bunches can be used to resonantly excite large amplitude wakefields in plasmas. The resonance is reached when the plasma wavelength is equal to the drive bunch train spacing. However, in order accelerate an electron bunch with a narrow energy spread, a trailing witness bunch must be generated. The witness bunch must be separated from the last drive bunch by one and a half time the distance between drive bunches. We show that such a drive/witness bunch train can be generated. The mask can also be designed to produce witness bunches trailing the drive bunch train by 2.5,3. 5, Â… times the drive bunch spacing in order to probe the coherence of the plasma wake in subsequent wave bucket. Resonantly driving plasma wakes with trains of bunches could lead to multiplication of the trailing bunch energy by up to the number of bunches in the drive train with high efficiency in a single stage. Experimental results will be presented.
* P. Muggli et al., Phys. Rev. Lett. {10}1, 054801, 2008
USC, Los Angeles, California
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
Funding: Work supported by US Department of Energy.
Plasma Wakefield Accelerator has been proven to be a promising technique to lower the cost of the future high energy colliders by offering orders of magnitude higher gradients than the conventional accelerators. However, it has been shown that ion motion is an important issue to account for in the extreme regime of ultra high intensities and ultra low emittances, characteristics of future high energy colliders. In this regime, the transverse electric field of the beam is so high that the plasma ions cannot be considered immobile at the time scale of electron plasma oscillations, thereby leading to a nonlinear focusing force. Therefore, the transverse emittance of a beam matched to the initial linear focusing will not be preserved under these circumstances. However, Vlasov equation predicts a matching profile even in the nonlinear regime. Furthermore, we extend the idea and introduce a plasma section that can match the entire beam to the mobile-ion regime of plasma. We also find the analytic solution for the optimal matching section. Simulation results will be presented.
USC, Los Angeles, California
UCLA, Los Angeles, California
Funding: Work supported by the US Department of Energy
Studies on propagation of electron beams in plasma have shown that in the blowout regime of the plasma wakefield accelerator (PWFA), the emittance of the incoming beam is preserved because of the linear focusing force exerted by a uniform ion column [1]. However, for positron beams the focusing force is nonlinear and they suffer emittance growth. We simulated the propagation of a positron beam in the uniform plasmas with different densities. We calculated the beam emittance from the simulation results and observed the beam size and emittance grow with increasing plasma density. Simulation results agree well with that of previous work.
CERN, Geneva
In the main linac of the compact linear collider (CLIC) , wakefield induced multi-bunch effects are important. They have a strong impact on the choice of accelerating structure design. The paper presents the limit for the wakefield that one bunch exerts on the next. It also gives estimates for the allowed level of persistent wake fields and on the resistive wall wakefield.
CERN, Geneva
First reference measurements of the longitudinal impedance were made with beam in the SPS machine in 1999 to quantify the results of the impedance reduction programme, completed in 2001. The 2001 data showed that the low-frequency inductive impedance had been reduced by a factor 2.5 and that bunch lengthening due to the microwave instability was absent up to the ultimate LHC bunch intensity. Measurements of the quadrupole frequency shift with intensity in the following years suggest a significant increase in impedance (which nevertheless remains below the 1999 level) due to the installation of eight extraction kickers for beam transfer to the LHC. Microwave instability is still not observed up to the maximum bunch intensities available from injector. The experimental results are compared with expectations based on the known longitudinal impedance of the different machine elements in the SPS.
Fermilab, Batavia
CERN, Geneva
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy and CARE-HHH
Motivated by the discussions on scenarios for LHC upgrades, beam studies on the stability of flat bunches in a double-harmonic RF system have been conducted in the CERN Proton Synchrotron (PS). Injecting nearly nominal LHC beam intensity per cycle, 18 bunches are accelerated on harmonic h=21 to 26 GeV with the 10 MHz RF system. On the flat-top, all bunches are then transformed to flat bunches by adiabatically adding RF voltage at h=42 from a 20 MHz cavity in anti-phase to the h=21 system. The voltage ratio V(h42)/V(h21) of about 0.5 was set according to simulations. For the next 140 ms, longitudinal profiles show stable bunches in the double harmonic RF bucket until extraction. Without the second harmonic component, coupled-bunch oscillations are observed. The flatness of the bunches along the batch is analyzed as a measure of the relative phase error between the RF systems due to beam loading. Measurements of electron cloud effects induced by the beam are also discussed. The results of beam dynamics simulations and their comparison with the measured data are presented.
Fermilab, Batavia
In the paper the results are presented for calculation of the transverse wake and RF kick from the power and HOM couplers of the acceleration structure. The beam emittance dilution caused by the couplers is calculated for the main linac and bunch compressor of ILC. It is shown that for the bunch compressor this effect may constitute a problem, and modification of the coupler unit may be necessary in order to preserve the cavity axial symmetry.
LBNL, Berkeley, California
Funding: Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Uneven beam fill patterns in storage rings, such as gaps in the fill patterns, leads to periodic, or transient loading of the modes of the RF cavities. We show that an analogous effect can occur in the loading of a dipole cavity mode when the beam passes off the electrical center of the cavity mode. Although this effect is small, it results in a variation of the transverse offset of the beam along the bunch train. For ultralow emittance beams, such as optimized third generation light sources and damping rings, this effect results in a larger projected emittance of the beam compared with the single bunch emittance. The effect is particularly strong for the case when a strong dipole mode has been purposely added to the ring, such as a deflecting, or ‘‘crab'' cavity. We derive an approximate analytic solution for the variation of the beam-induced deflecting voltage along the bunch train. We also show via a tracking simulation the combined effect of the periodic loading of the fundamental and dipole modes.
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
SLAC, Menlo Park, California
CERN, Geneva
Funding: Supported by the US-DOE under Contract DE-AC02-05CH11231 and the US-LHC LARP. Used resources of NERSC, supported by the US-DOE under Contract DE-AC02-05CH11231.
Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. Recently, it has been proposed to use feedback systems operating at high frequency (in the GHz range) to damp single-bunch transverse coherent oscillations that may otherwise be amplified during the interaction of the beam with ambient electron clouds. We have used the simulation package WARP-POSINST to study the growth rate and frequency patterns in space-time of the electron cloud driven beam breakup instability in the CERN SPS accelerator with, or without, an idealized feedback model for damping the instability. We will present our latest results and discuss their implications for the design of the actual feedback system.
LBNL, Berkeley, California
LLNL, Livermore, California
FZK, Karlsruhe
Funding: Supported by the US-DOE under Contract DE-AC02-05CH11231, the US-LHC LARP, and the US-DOE SciDAC program ComPASS. Used resources of NERSC, supported by the US-DOE under Contract DE-AC02-05CH11231.
At PAC05, we presented the package WARP-POSINST for the modeling of the effect of electron clouds on high-energy beams. We present here the latest developments in the package. Three new modes of operations were implemented: 1) “build-up mode” where, similarly to Posinst (LBNL) or Ecloud (CERN), the build-up of electron clouds is modeled in one region of an accelerator driven by a legislated bunch train; 2) “quasi-static mode” where, similarly to Headtail (CERN) or Quickpic (USC/UCLA), the “frozen beam” approximation is used to split the modeling of the beam and the electrons into two components evolving on their respective time scales; and 3) “Lorentz boosted mode” where the simulation is performed into a moving frame where the space and time scales related to the beam and electron dynamics fall in the same range. The implementation of modes (1) and (2) was primary motivated by the need for benchmarking with other codes, while the implementation of mode (3) fulfills the drive toward fully self-consistent simulations of e-cloud effect on the beam including the build-up phase. We also present benchmarking with other codes and selected results from its application to e-cloud effects.
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
Funding: work supported by the Department of Energy under contract number DE-AC03-76SF00515
We give an overview of wake fields and impedances in a proposed Super B project, which is based on extremely low emittance beams colliding at a large angle with a crab waist transformation. Understanding the effect wake fields have on the beam is critical for a successful machine operation. We use our combined experience from the operation of the SLAC B-factory and DAΦNE Phi-factory to eliminate strong HOM sources and minimize the chamber impedance in the Super B design. Based on a detailed study of the wake fields in this design we have developed a quasi-Green’s function for the entire ring that is used to study bunch lengthening and beam stability. In particular, we check the stability threshold using numerical solutions of the Fokker-Plank equation. We also make a comparison of numerical simulations with the bunch lengthening data in the B- factory.
SLAC, Menlo Park, California
A proposed high-brightness synchrotron light source (PEP-X) is under design at SLAC. The 4.5-GeV PEP-X storage ring has four theoretical minimum emittance (TME) cells to achieve the very low emittance and two double-bend achromat (DBA) cells to provide spaces for IDs. Damping wigglers will be installed in zero-dispersion straights to reduce the emittance below 0.1 nm. Ion induced beam instability is one critical issue due to its ultra small emittance. Third harmonic cavity can be used to lengthen the bunch in order to improve the beam life time. Bunch-train filling pattern is proposed to mitigate both the fast ion instability and beam loading effect. This paper investigates the fast ion instability and beam loading for different beam filling patterns.
Tech-X, Boulder, Colorado
Fermilab, Batavia
Funding: This work was supported by the US DOE Office of Science, Office of Nuclear Physics, under Grant No.DE-FG02-08ER85183
Recent improvements to BBSIM permit detailed simulations of collective effects due to resistive wall wake fields. We compare results of beam transfer measurements (BTF) in the Tevatron and RHIC with and without the effects of resistive wall wake fields. These are then compared to actual BTF measurements made in both machines and the impact of intensity on our measurements. We also investigate the impact of resistive wall wake fields on various chromaticity measurement approaches.
UCLA, Los Angeles, California
Rome University La Sapienza, Roma
We present the status of development of a 1.5+0.5 cell photoinjector run in the blowout regime. LANL Parmela simulation results indicate a near uniform beam of slice energy spread on the order of 500 eV when neglecting thermal effects. We examine the use of an extra half cell to control longitudinal beam growth and compare the system in development with previous 1.6 cell photoinjector designs.
USC, Los Angeles, California
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
BNL, Upton, Long Island, New York
Funding: Work supported by US Department of Energy.
Current Filamentation Instability, CFI, (or Weibel instability) is of central importance for relativistic beams in plasmas for the laboratory, ex. fast-igniter concept for inertial confinement fusion, and astrophysics, ex. cosmic jets. Simulations, with the particle-in-cell code QuickPic, with a beam produced by an RF accelerator show the appearance and effects of CFI. The instability is investigated as a function of electron beam parameters (including charge, transverse size and length) and plasma parameters (density and length) by evaluating the filament currents and magnetic fields. We present simulation results, discuss further simulation refinements, suggest criteria and threshold parameters for observing the presence of CFI and outline a potential future experiment.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Since the start of Fermilab Collider Run II in 2001, the maximum weekly antiproton accumulation rate has increased from 400·1010 Pbars/week to approximately 3,700·1010 Pbars/week. There are many factors contributing to this increase, one of which involves changes to operational procedures that have streamlined and automated antiproton source production. Automation has been added to our beam line orbit control, stochastic cooling power level management, and RF settings. In addition, daily tuning efforts have been streamlined by implementing sequencer driven aggregates.
BNL, Upton, Long Island, New York
Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka
IAP, Frankfurt am Main
Department of Energy Sciences, Tokyo Institute of Technology, Yokohama
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A new 4 rod RFQ fabricated by IAP, Frankfurt, is being commissioned at Brookhaven National Laboratory. The RFQ will accelerate intense heavy ion beams provided by an Electron Beam Ion Source (EBIS) up to 300 keV/u. The RFQ will accelerate a range of Q/M from 1 to 1/6, and the accelerated beam will be finally delivered to RHIC and NSRL. The first beam test is planned to use beams from the BNL Test EBIS. The detailed test results will be presented.
CERN, Geneva
KIP, Heidelberg
In this paper is analysed the influence of Higher Order Modes (HOM) on the operation of the superconducting linac section of the SPL, the Superconducting Proton Linac being designed at CERN. For this purpose, the characteristics of the HOMs in the 2 different beta families (0.65, 0.92 both at 704 MHz) of the SPL are calculated to estimate their effect on the cryogenic system and on the beam stability. For both criteria the maximum external Q of the HOMs is defined.
CERN, Geneva
Construction work for the new CERN linear accelerator, Linac4, started in October 2008. Linac4 will replace the existing Linac2 and provide an H- beam at 160 MeV (as opposed to the present 50 MeV proton beam) for injection into the CERN PS Booster (PSB). The charge-exchange H- injection combined with the higher beam energy will allow for an increase in beam brightness required for reaching the ultimate LHC luminosity. Commissioning of Linac4 and of the transfer line to the PSB is planned for the last quarter of 2012. Appropriate beam instrumentation is foreseen to provide transverse and longitudinal beam characterization at the exit of Linac4 and in two dedicated measurement lines located before injection into the PSB. A detailed description of the diagnostics set, especially of spectrometer and emittance meter, and the upgrade of the measurement lines for Linac4 commissioning and operation is presented.
IAP, Frankfurt am Main
The goal of the Frankfurt Funneling Experiment is to multiply beam currents by merging two low energy ion beams. In an ideal case this would be done without any emittance growth. Our setup consists of two ion sources, a Two-Beam-RFQ accelerator and a multi cell deflector which bends the beams to one common beam axis. Current work is the design of a new beam transport system between RFQ accelerator and deflector. With extended RFQ-electrodes the drift between the Two-Beam-RFQ and the rf-deflector will be minimized and therefor unwanted emittance growth prohibited. First rf measurements with a scaled experiment will be presented.
IAP, Frankfurt am Main
Funneling is a method to increase low energy beam currents in multiple stages. The Frankfurt Funneling Experiment is a model of such a stage. The experiment is built up of two ion sources with a electrostatic lens systems, a Two-Beam RFQ accelerator, a funneling deflector and a beam diagnostic system. The two beams are bunched and accelerated in a Two-Beam RFQ and the last parts of the RFQ electrodes achieve a 3d focus at the crossing point of the two beam axis. A funneling deflector combines the bunches to a common beam axis. The optimized ion sources are adapted to the front end bunching section. Recent funneling measurements with the one-gap and the multi-gap deflector will be presented.
IAP, Frankfurt am Main
GSI, Darmstadt
A new CW-RFQ will be built for the upgrade of the HLI (High Charge State Injector) of GSI for operating with a 28 GHz-ECR-Ion source and simultaneous increase of the beam duty cycle from 25% to 100 %. The new HLI 4-rod RFQ will accelerate charged ions from 4 keV/u to 300 keV/u for the injection into the IH-structure The design had been optimized to get a rather short structure with LRFQ=2m to match the available RF-power of max. 60 kW in cw. High beam transmission, a small energy spread and small transverse emittance growth and good input matching were design goals. Properties of this CW-RFQ and status of project will be presented.
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL, Chilton, Didcot, Oxon
A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed for the Front End Test Stand (FETS) at RAL in the UK. Previous beam dynamics simulations, based on field maps produced with a field approximation code, provide a baseline for the new design. A novel design method is presented that combines the CAD and electromagnetic modelling of both the RFQ tank and the vane modulations with more sophisticated beam dynamics simulations using the General Particle Tracer code (GPT). This approach allows the full integration of the optimisation of the RFQ, based on beam dynamics simulations using a 3D EM-field map of the CAD model, with the design and manufacture of the RFQ vane modulations and RFQ tank. The design process within the Autodesk Inventor CAD software is outlined and details of the EM modelling of the RFQ in CST EM Studio are given. Results of beam dynamics simulations in GPT are presented and compared to previous results with field approximation codes. Finally, possible methods of manufacture based on this design process are discussed.
ORNL, Oak Ridge, Tennessee
GSI, Darmstadt
The 4ν=1 resonance of a linac is demonstrated when the depressed tune is around 90 deg. It is observed that this fourth order resonance is dominating over the better known envelope instability and practically replacing it. Simulation study shows a clear emittance growth by this resonance and its stopband. One of the authors [DJ] made a proposal to GSI to measure the stopband of this resonance. The experiment was conducted successfully and the experiment data will be presented separately in the conference.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Future projects like a neutrino factory or an advanced spallation neutron source require high power proton accelerators capable of producing beams in the multi-MW range. The quality of the beam delivered to the target is very much dictated by the accelerator front end and by the lower energy linac. Prompted by the Front End Test Stand (FETS) under construction at Rutherford Appleton Laboratory (RAL), a new 800 MeV H- linac is being considered as part of a possible MW upgrade for ISIS. Preliminary simulations of high intensity beam dynamics and beam transport in the new linac suggest that a re-evaluation of the front end Medium Energy Beam Transport (MEBT) line is necessary. In this paper different optical designs for the 3 MeV MEBT line are presented and their impact on the subsequent Drift Tube Linac (DTL) section is being analysed.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Features of a linac and ring for potential ISIS upgrades are outlined. Maximum parameters are 0.8 GeV, 0.5 MW for the H(-)linac and 3.2 GeV, 2 MW for the ring, both at 30 or 50 Hz. The linac is based on a 324 MHz frequency at low energies, having an ion source, LEBT, 3 MeV RFQ and MEBT, with A 74.8 MeV drift tube linac (DTL) and intermediate energy beam transport (IEBT). The MEBT chopper stage uses solenoid and triplet focusing, and both MEBT and IEBT have long sections for beam collimation. There are three options for the higher energies, a 648 MHz superconducting linac(ScL1, ScL2 and ScL3), a 648 MHz (CCL, ScL2 and ScL3), and a 324 MHz (ScLa) with a two-stage 972 MHz (ScLb and ScLc). The ScL1, CCL and ScLa are designed to accelerate the H(-) beam from 74.8 to ~200 MeV. The proton synchrotron design is based on a five superperiod lattice of doublet and triplet cells, and has a circumference of ~ 370 m.
THALES, Colombes
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
EuroMev, Buc
A turn key 100 MeV linac was provided by THALES Communications in order to inject electrons into the booster synchrotron of ALBA*. The linac was commissioned in October 2008. This paper will remind the main features of the linac** and will give results obtained during the commissioning tests. The energy and emittance measurements have been done on the transfer line concieved and realized by CELLS. Specified and measured beam parameters will be compared to show the performance of the entire system.
* D. Einfeld "Progress of ALBA", EPAC08, Genoa, Italy, June 2008.
** A. Falone et Alt, "Status of the 100 MeV preinjector for the ALBA synchrotron", EPAC08, Genoa, Italy, June 2008.
CIAE, Beijing
TRIUMF, Vancouver
As a high intensity compact cyclotron, CYCIAE-100 is designed to provide proton beams in two directions simultaneously. At the extraction region, the fringe field of the main and the field of the combination magnet will influence the beam optics. The fringe field may become critical by comparison with the separated sector machine because of the compact structure. The dispersion during the beam extraction should not be ignored, which may make the beam envelop become evidently bigger. Then the beam loss and residual radiation increase. To study the beam optics at the extraction region of CYCIAE-100, the orbit tracking and transfer matrix calculation and symplectic by function extension of the code GOBLIN and modification of STRIPUBC have been implemented. The characteristics of the extracted beam have been investigated based on the main field from a FEM code and overlapping with the field generated from the combination magnet at each extraction port. The results are also compared with those from the CIAE’s code CYCTRS to confirm this precise prediction. The transfer matrix from this simulation is analyzed and used for the down stream beam line design.
CIAE, Beijing
FZJ, Jülich
The 10 mA, 40keV H- pulsed injection line for the CIAE 10 MeV CRM cyclotron has two main operation modes for bunched beams: delivering 5 mA CW beam or chopped pulse with more than 100uA. Chopped pulse is achieved by placing behind the 70.5 MHz bunching cavity a sinusoidal transverse deflecting cavity with frequency of 2.2 MHz, 1/32 of the bunching frequency. Particles outside the wanted ±3° phase width @ 2.2 MHz, corresponding to ±90° @ 70.5 MHz, are either absorbed in a 50cm drift after chopper or at round slit1, 1cm aperture. Time dependence of sinusoidal chopping field causes RMS emittance increase by a factor 3 and changes twiss parameter alpha by a factor 2 before the round slit1. Solenoid couples motion in transversal planes, but equalizes both RMS emittances. Particle tracking results are presented for the chopped pulse, showing longitudinal-transverse coupling in the deflector and equalization of RMS emittances in the solenoid. Optimised focusing strength leads to about 1 % transmission efficiency for the chopped pulse. The CRM inflector receives 2.4 ns long pulse at about 4.4 MHz repetition rate, 1/16 of the RF frequency.
JINR, Dubna, Moscow Region
In axial injection channels of FLNR JINR cyclotrons the axial symmetric ion beam is formed just after the analyzing bending magnet. This gives an opportunity to use for beam focusing at vertical part of the channel solenoidal magnetic lenses only. During the motion of intense axial symmetric beam in the longitudinal magnetic field of solenoids and cyclotron the transverse tunes Qx, Qy coincide. In this case the small disturbance of beam axial symmetry leads to excitation of coupling resonance Qx-Qy=0 due to beam self-fields. The influence of the resonance results in significant asymmetry of the transverse beam emittances. The magnitude of this asymmetry is evaluated within the framework of moments method and is in a good agreement with one obtained in the macro-particles simulation. The correction of resonance by means of the normal quadrupole lens is proposed.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
BNL, Upton, Long Island, New York
Fermilab, Batavia
TRIUMF, Vancouver
EMMA (Electron Machine with Many Applications) is a prototype non-scaling electron FFAG to be hosted at Daresbury Laboratory. NS-FFAGs related to EMMA have an unprecedented potential for medical accelerators for carbon and proton hadron therapy. It also represents a possible active element for an ADSR (Accelerator Driven Sub-critical Reactor). This paper summarises the commissioning plans for this machine together with the major steps and experiments involved along the way. A description of how the 10 to 20 MeV beam is achieved within ALICE is also given, as well as extraction from the EMMA ring to the diagnostics line and then dump.
University of Fukui, Faculty of Engineering, Fukui
KURRI, Osaka
FFAG DDS Research Organization, Tokyo
The accelerator–based neutron source using ERIT (Energy/emittance Recovery Internal Target) scheme has been constructed at KURRI (Kyoto University Research Reactor Institute). And the first beam test was successfully completed in March 2008. In this poster, recent status of beam studies will be presented.
NSCL, East Lansing, Michigan
The Facility for Rare Isotope Beams (FRIB) will provide intense beams of short-lived isotopes for fundamental research in nuclear structure and nuclear astrophysics. Operation of the facility requires intense uranium primary beams. At the present time acceleration of two simultaneous charge states of uranium from a single ion source is needed to achieve the required intensity. Three schemes are considered for funneling the beams from two sources as an alternate solution. One is the traveling wave RF kicker for merging of bunched beams extracted from ECR ion sources. Another one implements the idea of utilizing an RFQ for beam merging*, which can be used after preliminary acceleration of both beams. The third approach assumes usage of a conventional standing-wave RF kicker. Parameters of all three schemes are compared and analyzed.
*R.H.Stokes and G.N.Minerbo, AIP Conference Proceedings 139 (1985), p.79.