KEK, Ibaraki
BINP SB RAS, Novosibirsk
Work presented on behalf of the KEKB Accelerator Group.
SLAC, Menlo Park, California
For the PEP-II Operation Staff: PEP-II is an asymmetric e+e- collider operating at the Upsilon 4S and has recently set several performance records. The luminosity has reached 1.2x1034/cm2/s and has delivered an integrated luminosity of 910/pb in one day. PEP-II operates in continuous injection mode for both beams boosting the integrated luminosity. The peak positron current has reached 3.0 A of positrons and 1.9 A of electrons in 1732 bunches. The total integrated luminosity since turn on in 1999 has reached over 410/fb. This paper reviews the present performance issues of PEP-II and also the planned increase of luminosity in the near future to over 2 x 1034/cm2/s.
CLASSE, Ithaca
University of Minnesota, Minneapolis, Minnesota
CESR-LEPP, Ithaca, New York
Cornell University, Department of Physics, Ithaca, New York
Technion, Haifa
In April 2008, we propose to begin operation of the Cornell Electron Storage Ring (CESR) as a test accelerator, CesrTA, for International Linear Collider (ILC) damping ring research. Utilizing 12 damping wigglers, the baseline CesrTA lattice at 2.0 GeV will offer a natural geometric emittance of 2.25 nm. An experimental program has been laid out which focuses on several key areas of damping rings R&D. First we will test vacuum chamber designs to suppress electron cloud growth in the wiggler magnets. Secondly, we will develop correction, tuning and emittance monitoring strategies to achieve vertical emittances of a few picometers. As part of this effort we will validate alignment and survey techniques being developed by the Linear Collider Alignment and Survey group (LiCAS) for curved tunnel applications. After achieving ultra-low emittance, we intend to explore the impact of the electron cloud, the fast ion instability and other beam dynamics effects on ultra-low emittance beams. Finally, we plan to test various technical systems required for the ILC damping rings. This paper provides an update on conceptual design issues for CesrTA and describes the experimental program in detail.
Jefferson Lab, Newport News, Virginia
CEBAF is a 5-pass, recirculating cw electron linac operating at ~6 GeV. The 12-GeV Upgrade is a $300M project anticipated to receive Critical Decision 2 approval in late summer of 2007 and begin construction activities in 2008; funding for the project is provided by the DOE Office of Nuclear Physics which will double the beam energy. The new energy reach will permit significant extensions in research into non-perturbative aspects of QCD. Areas of interest are Generalized Parton Distributions (GPDs), measurements at high-xBjorken, and the use of hybrid mesons to explore the nature of quark confinement. The upgrade includes: doubling the accelerating voltages of the linacs by adding 10 new high-performance cryomodules plus the requisite expansion of the 2K cryogenics plant and rf power systems, upgrading the beam transport system from 6 GeV to 12 GeV capability through extensive re-use of existing hardware, adding one recirculation arc, adding a new experimental area and the beamline to it, building new experimental equipment for the GPD, high-xBjorken, and hybrid mesons programs. The presentation will touch on the science and give some details of the accelerator plans.
MAX-lab, Lund
SESAME, Amman
BNL, Upton, Long Island, New York
INFN/LNF, Frascati (Roma)
INFN-Milano, Milano
INFN-Roma II, Roma
UCLA, Los Angeles, California
ENEA C. R. Frascati, Frascati (Roma)
INFN-Roma, Roma
NSRRC, Hsinchu
IUCF, Bloomington, Indiana
DESY, Hamburg
CLASSE, Ithaca
CHESS, Ithaca, New York
Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
Cornell University, Department of Physics, Ithaca, New York
The status of plans for an Energy-Recovery Linac (ERL) X-ray facility at Cornell University is described. Currently, Cornell operates the Cornell High Energy Synchrotron Source (CHESS) at the CESR ring and the ERL is planned to be an extension to the CESR ring with the addition of a 5-GeV superconducting c.w. linac. Topics covered in this paper include the full layout on the Cornell campus, the different operation modes of the accelerator, methods to limit emittance growth, control of beam-ion effects and ways to limit transverse instabilities. As an upgrade of the CESR ring, special attention is given to reuse of many of the existing components. The very small electron-beam emittances would produce an x-ray source that is highly superior than any existing storage-ring light source. The ERL includes 18 X-ray beamlines optimized for specific areas of research that are currently being defined by an international group of scientists. This planned upgrade illustrates how other existing storage rings could be upgraded to work as ERL light sources with vastly improved beam qualities and with limited dark time for x-ray users.
SOLEIL, Gif-sur-Yvette
JASRI/SPring-8, Hyogo-ken
TEMF, Darmstadt
The Wien filter is well known as a common energy analyzer and is also used more and more as a compact variant of a spin rotator at low energy for electrons. The Wien filter based on a homogenous magnetic and electric field that are perpendicular to each other and transverse to the direction of the electrons. The rotation of the spin vector is caused by the magnetic field. If the force equilibrium condition is fulfilled the beam should not be deflected at the Wien filter. Simulations show that in the fringe fields the electrons get a kick. Therefore full 3D simulations of the electromagnetic fields and beam dynamics simulations are studied in detail at the example of the Wien filter at the new polarized 100 keV electron injector at the S-DALINAC. The results of the simulations with CST Design Environment(TM), MAFIA and V-Code are presented.
University of Karlsruhe, Karlsruhe
CERN, Geneva
FZK, Karlsruhe
University of Erlangen-Nurnberg, Physikalisches Institut II, Erlangen
Visual Information Center, Inc., Ibaraki-ken
KEK, Ibaraki
JAEA, Ibaraki-ken
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
JAEA/LINAC, Ibaraki-ken
The XAL application development environment has been installed as a part of the control system for the Japan Proton Accelerator Research Center (J-PARC). XAL was initially developed at SNS and has been described at length in previous conference proceedings (e.g., Chu et. al. APAC07, Galambos et. al. PAC05, etc.). The fundamental tenet of XAL is to provide a consistent, high-level programming interface, along with a set of high-level application tools, all of which are independent of the underlying machine hardware. Control applications can be built that run at any accelerator site where XAL is installed. Of course each site typically has specific needs not supported by XAL and the framework was designed with this in mind: each institution can upgrade XAL which then is accessible to all users. We outline the upgrades and enhancements to the XAL online model necessary for accurate simulation of the J-PARC linac. For example, we have added permanent magnet quadrupoles and additional space charge capabilities such as off-centered and rotated beams and bending magnets with space charge. We present the physics models for the upgrades as well as the software architecture supporting them.
KEK, Ibaraki
ISSP/SRL, Chiba
Advanced Manufacturing Research Institute, Tsukuba
KEK, Ibaraki
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
USTC/NSRL, Hefei, Anhui
In this paper, HLS (Hefei light Source) bunch-by-bunch measurement and feedback system will be introduced. This system is integrated with longitudinal oscillation measurement system, fast vector control, fiber notch filter and bunch current detection system. The detail of the two fronts will be shown. Some experimental results by this system are also present in this paper, as phase-space tracing, mode dumping rate, and feedback experiments.
Muons, Inc, Batavia
Fermilab, Batavia, Illinois
A helical cooling channel consisting of a pressurized gas absorber imbedded in a magnetic channel that provides superimposed solenoidal, helical dipole and helical quadrupole fields has shown considerable promise in providing six-dimensional cooling of muon beams. The analysis of this muon cooling technique with both analytic and simulation studies has shown significant reduction of muon phase space. A particular channel that has been simulated is divided into four segments each with progressively stronger fields and smaller apertures to reduce the equilibrium emittance so that more cooling can occur. The fields in the helical channel are sufficiently large that the conductor for segments 1 and 2 can be Nb3Sn and the conductor for segments 3 and 4 may need to be high temperature superconductor. This paper will describe the magnetic specifications for the channel and two conceptual designs on how to implement the magnetic channel.
Muons, Inc, Batavia
BNL, Upton, Long Island, New York
UMiss, University, Mississippi
The ability of high temperature superconducting (HTS) conductor to carry high currents at low temperatures makes feasible the development of very high field magnets for uses in accelerators and beam-lines. A specific application of a very high field solenoid is to provide a very small beta region for the final cooling stages for a muon collider. This paper will describe a conceptual design of a 50 Tesla solenoid based on Bi-2223 HTS tape, where the magnet will be operated at 4.2 K to take advantage of the high current carrying capacity at that temperature. A 25 Tesla solenoid has been run using a 5 Tesla Bi-2212 insert. The current carrying capacity of the BSCCO wire has been measured to be 266 Amps/mm2 at 4.2 K at the NHFML. This paper will describe the technical issues associated with building this 50 Tesla magnet. In particular it will address how to mitigate the large Lorentz stresses associated with the high field magnet and how to design the magnet to reduce the compressive end forces.
Muons, Inc, Batavia
Fermilab, Batavia, Illinois
MANX is a 6-dimensional muon ionization-cooling experiment that has been proposed to Fermilab to demonstrate the use of a Helical Cooling Channel (HCC) for future muon colliders and neutrino factories. The HCC for MANX has solenoidal, helical dipole, and helical quadrupole magnetic components which diminish as the beam loses energy as it slows down in a liquid helium absorber inside the magnets. Two superconducting magnet system designs are described which use quite different approaches to providing the needed fields. Additional magnets that provide emittance matching between the HCC and upstream and downstream spectrometers are also described as are the results of G4Beamline simulations of the beam cooling behaviour of the complete magnet and absorber system.
LBNL, Berkeley, California
The Muon Ionization Cooling Experiment (MICE) will demonstrate ionization cooling in a short section of a realistic cooling channel using a muon beam at Rutherford Appleton Laboratory (RAL) in the UK. A five-coil, superconducting spectrometer solenoid magnet at each end of the cooling channel will provide a 4 T uniform field region for the scintillating fiber tracker within the magnet bore tubes. The tracker modules are used to measure the muon beam emittance as it enters and exits the cooling channel. The cold mass for the 400 mm warm bore magnet consists of two sections: a three-coil spectrometer magnet and a two-coil matching section that matches the uniform field of the solenoid into the MICE cooling channel. The detailed design and analysis of the two spectrometer solenoids has been completed, and the fabrication of the magnets is in its final stages. The primary features of the spectrometer solenoid magnetic and mechanical designs are presented along with a summary of key fabrication issues and photos of the fabrication process.
BNL, Upton, Long Island, New York
In this paper we describe unique features of magnets for R&D ERL, which is under construction in Collider-Accelerator Department, BNL. The R&D ERL serves as a test-bed future BNL ERLs, such as electron-cooler-ERL for RHIC and 20 GeV ERL for future electron-hadron, eRHIC. We present selected designs of various dipole and quadrupole magnets, which are used in Z-bend merging systems and the returning loop, 3-D simulations of the fields in these magnets, particle tracking and analysis of magnet's influence on the beam parameters. We discuss an uncommon method of setting requirements on the quality of magnetic field and transferring them into measurable parameters as well as into manufacturing tolerances. We compare selected simulation with results magnetic measurements.
ORNL, Oak Ridge, Tennessee
The SNS ring and associated transport lines, commissioned in January 2006, are designed to accumulate and deliver up to 1.5·1014, 1 GeV protons at 60 Hz to a liquid mercury target for neutron production. In order to control activation and to allow for routine hands-on maintenance of accelerator components, beam loss in most of the ring must remain below 1 W/m . For the full 1.4 MW beam, this translates to a fractional beam loss limit of 0.01%. Accomplishing this loss limit at full beam power will require successful utilization of the ring's two-stage betatron collimation system. In this paper we present the results of initial collimation experiments. We characterize the collimation-induced beam-loss pattern and compare our results with simulations. In addition, we discuss other existing beam-loss-related challenges in the ring.
Jefferson Lab, Newport News, Virginia
Advances in ionization cooling, phase space manipulations, and technologies to achieve high brightness muon beams are stimulating designs of high-luminosity energy-frontier muon colliders. Simulations of Helical Cooling Channels (HCC) show impressive emittance reductions, new ideas on reverse emittance exchange and muon bunch coalescing are being developed, and high-field superconductors show great promise to improve the effectiveness of ionization cooling. Experiments to study RF cavities pressurized with hydrogen gas in strong magnetic fields have had encouraging results. A 6-dimensional HCC demonstration experiment is being designed and a 1.5 TeV muon collider is being studied at Fermilab. Two new synergies are that very cool muon beams can be accelerated in ILC RF structures and that this capability can be used both for muon colliders and for neutrino factories. These advances are discussed in the context of muon colliders with small transverse emittances and with fewer muons to ease requirements on site boundary radiation, detector backgrounds, and muon production.
BNL, Upton, Long Island, New York
ALBA, Bellaterra (Cerdanyola del Valles)
Since 2001 RHIC has experienced electron cloud effects, which have limited the beam intensity. These include dynamic pressure rises – including pressure instabilities, a reduction of the stability threshold for bunches crossing the transition energy, and possibly slow emittance growth. We report on the main observations in operation and dedicated experiments, as well as the effect of various countermeasures including baking, NEG coated warm pipes, pre-pumped cold pipes, bunch patterns, scrubbing, and anti-grazing rings.
PSI, Villigen
LBNL, Berkeley, California
IUCF, Bloomington, Indiana
Fermilab, Batavia, Illinois
We systematically measured the emittance evolution of a fast cycling proton accelerator on a turn-by-turn basis under various beam intensities via an ionization profile monitor (IPM). The vertical emittance growth rate was derived and phenomenologically analyzed. The transverse and longitudinal components in the horizontal beam size were separated by making use of their different evolution behaviors. The quadrupole mode beam size oscillation after transition crossing is also studied and explained. We found a considerable space-charge-induced emittance growth rate component in the vertical plane but not as much for the horizontal plane. We carried out multiparticle simulations to understand the mechanism of space-charge-induced emittance growth. The major sources of emittance growth were found to be the random skew-quadrupole and dipole field errors in the presence of large space-charge tune spread.
PRSTAB 9, 014202 (2006)
SLAC, Menlo Park, California
DESY, Hamburg
LBNL, Berkeley, California
The Linac Coherent Light Source (LCLS) is a SASE x-ray free-electron laser project presently under construction at SLAC. The injector section from RF photocathode gun through the first bunch compressor chicane was installed during the Fall of 2006. The first bunch compressor chicane is located at 250 MeV and nominally compresses a 1-nC electron bunch from an rms length of about 1 mm to 0.2 mm. The degree of compression is highly adjustable using RF phasing and also chicane magnetic field variations. Transverse phase space and bunch length diagnostics are located immediately after the chicane. We present measurements and simulations of the longitudinal and transverse phase space after the chicane in various beam conditions, including extreme compression where coherent radiation effects are expected to be striking.
PPPL, Princeton, New Jersey
The Paul Trap Simulator Experiment is a compact laboratory Paul trap that simulates a long, thin charged-particle bunch coasting through a kilometers-long magnetic alternating-gradient (AG) transport system by putting the physicist in the beam's frame-of-reference. The transverse dynamics of particles in both systems are described by the same sets of equations, including all nonlinear space-charge effects. The time-dependent quadrupolar electric fields created by the confinement electrodes of a linear Paul trap correspond to the axially-dependent magnetic fields applied in the AG system. Results are presented from experiments in which the lattice period and strength are changed over the course of the experiment to transversely compress a beam with an initial depressed-tune of 0.9. Instantaneous and smooth changes are considered. Emphasis is placed on determining the conditions that minimize the emittance growth and the number of halo particles produced after the beam compression. The results of PIC simulations performed with the WARP code agree well with the experimental data. Initial results from a newly installed laser-induced fluorescence diagnostic will also be discussed.
UMD, College Park, Maryland
Circular accelerators and storage rings have traditionally been designed with limited intensity in order to avoid resonances and instabilities. The possibility of operating a ring beyond the Laslett tune shift limit has been suggested but little tested, apart from a pioneering experiment by Maschke at the BNL AGS in the early 1980s. We have recently circulated the highest-space-charge beam in a ring to date in the University of Maryland Electron Ring (UMER), achieving a breakthrough both in the number of turns and in the amount of current propagated. At undepressed tunes of up to 7.6, the space charge in UMER is sufficient to depress the tune by nearly a factor of 2, resulting in tune shifts up to 3.6. This makes the UMER beam the most intense beam that has been propagated to date in a circular lattice. This is an exciting and promising result for future circular accelerators, and the UMER beam can now be used as a platform to study intense space charge dynamics in rings.
NRL, Washington, DC
SAIC, Burlington, Massachusetts
Low emittance, high current density sources are required to achieve the small beam size needed for high frequency vacuum electronic devices and for high power free electron lasers (FELs). Emission models are of particular importance in the emittance-dominated regime, where emission non-uniformity and surface structure of the cathode can have an impact on beam characteristics. We have been developing comprehensive time-dependent photoemission models for the simulation codes that account for laser and cathode material and surface characteristics. MICHELLE* is NRL's finite-element self-consistent electrostatic time-domain code: it has the ability to import an RF field, and has unique capabilities for modeling the emission and the self fields, near the cathode. In particular, some instances of surface irregularities and emission non-uniformity (due to work function variation) leading to such effects as beam emittance and high frequency oscillations are possible to model due to the code's conformal meshing capabilities. We will present results of the implementation of the 'next generation' photoemission models in the MICHELLE code for modeling surface roughness and non-uniformity.
* John Petillo, et al., "The MICHELLE Three-Dimensional Electron and Collector Modeling Tool: Theory and Design", IEEE Trans. Plasma Sci., vol. 30, no. 3, June 2002, pp. 1238-1264.
SLAC, Menlo Park, California
Over the past years, SLAC's Advanced Computations Department (ACD) has developed the parallel finite element particle-in-cell code Pic3P (Pic2P) for simulations of beam-cavity interactions dominated by space-charge effects. As opposed to standard space-charge dominated beam transport codes, which are based on the electrostatic approximation, Pic3P (Pic2P) includes space-charge, retardation and boundary effects as it self-consistently solves the complete set of Maxwell-Lorentz equations using higher-order finite element methods on conformal meshes. Use of efficient, large-scale parallel processing allows for the modeling of photoinjectors with unprecedented accuracy, aiding the design and operation of the next-generation of accelerator facilities. Applications to the Linac Coherent Light Source (LCLS) RF gun are presented.
CLS, Saskatoon, Saskatchewan
BESSY GmbH, Berlin
PTB, Berlin
In 2003, the Metrology Light Source (MLS) was approved, a dedicated low energy electron storage ring of the Physikalisch-Technische-Bundesanstalt (PTB), the German national metrology institute. Design, construction and operation of the MLS are realized by BESSY, based on the PTB requirements for a permanent accessible radiometry source, optimized for the spectral range between UV up to VUV. The MLS is tunable in energy between 200 MeV and 600 MeV. Based on the experiences at BESSY, a highly stable and reliable Race Track Microtron for injection was realized by Danfysik. The commissioning of the 100 MeV microtron at the MLS started in December 2006. The concept and construction as well as the main parameters of the microtron are introduced.
DESY, Hamburg
INFN/LNF, Frascati (Roma)
DESY, Hamburg
Jefferson Lab, Newport News, Virginia
SLAC, Menlo Park, California
SBUNSL, Stony Brook, New York
BNL, Upton, Long Island, New York
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
ELETTRA, Basovizza, Trieste
UCLA, Los Angeles, California
INFN-Milano, Milano
INFN/LNF, Frascati (Roma)
INFN-Roma II, Roma
ENEA C. R. Frascati, Frascati (Roma)
Universita di Roma I La Sapienza, Roma
INFN-Milano, Milano
Universita degli Studi di Milano, Milano
INFN/LNF, Frascati (Roma)
INFN/LNF, Frascati (Roma)
The SPARC project consists in a 150 MeV B-band, high-brilliance linac followed by 6 undulators for FEL radiation production at 530 nm. The linac assembly has been recently completed. During year 2006 a first experimental phase aimed at characterizing the beam emittance in the first 2m drift downstream the RF gun has been carried out. The low level RF control electronics to monitor and synchronize the RF phase in the gun and the laser shot on the photocathode has been commissioned and extensively tested during the emittance measurement campaign. The laser synchronization has been monitored by measuring the phase of the free oscillation of an RF cavity impulsively excited by the signal of a fast photodiode illuminated by the laser shot. Phase stability measurements are reported, both with and without feedback correction of the slow drifts. A fast intra-pulse phase feedback system to reduce the phase noise produced by the RF power station has been also positively tested.
INFN/LNF, Frascati (Roma)
INFN-Milano, Milano
CEA, Gif-sur-Yvette
INFN-Roma II, Roma
ENEA C. R. Frascati, Frascati (Roma)
SOLEIL, Gif-sur-Yvette
SLAC, Menlo Park, California
Universita di Roma I La Sapienza, Roma
INFN-Roma, Roma
UCLA, Los Angeles, California
INFN-Lecce, Lecce
INFN/LNF, Frascati (Roma)
INFN-Milano, Milano
INFN-Roma, Roma
INFN-Milano, Milano
Universita degli Studi di Milano, Milano
RIKEN Spring-8 Harima, Hyogo
TUB, Beijing
This work was supported by the Chinese National Foundation of Natural Sciences under Contract no. 10645002.
TUB, Beijing
PAL, Pohang, Kyungbuk
There are growing interests in generation, preservation and applications of high brightness electron beam. With the rapid development in the techniques for emittance compensation and laser shaping, we are approaching the limit-the uncorrelated thermal emittance. In this paper, we report the measurements of thermal emittance for Cu and Mg. The measurement is conducted in a field-free region. The energy spectrum and angular distribution of the electrons are measured immediately after its emission and further used to reconstruct the initial phase space and the corresponding thermal emittance. We also show how cathode surface roughness* and laser incidence angle as well as its polarization state** affect the quantum efficiency and thermal emittance.
*X. Z. He, High energy physics and nuclear physics,28(2004)1007.**Dao Xiang,et al, NIM A,562(2006)48.
TUB, Beijing
The ultrashort ultraviolet (UV) laser system and the optical transport line for driving the photocathode RF gun at Accelerator Laboratory of Tsinghua University are introduced in the article. Temporal profile of the UV pulse was measured by non-colinear difference frequency generation (DFG) between the UV pulse itself and the jitter-free residual IR laser pulse after third harmonic generation (THG) process. Experiments to measure the dependence of quantum efficiency (QE) on laser polarization state are also performed. Results show that in our case the ratio of QE between p- and s- polarization is more than 2.6.
USTC/NSRL, Hefei, Anhui
USTC, Hefei, Anhui
USTC/NSRL, Hefei, Anhui
USTC, Hefei, Anhui
PAL, Pohang, Kyungbuk
TUB, Beijing
A high-brightness electron beam is emitted from a photo-cathode (PC) RF gun for use in the FIR (Far Infrared) facility being built at the Pohang Accelerator Laboratory (PAL). The beam dynamics study for the PAL XFEL injector is essencial to generate low emittance electron beam from the PC RF gun. The XFEL injector requires 1 nC beam with short bunch length and low emittance. This conditions are simulated with PARMELA code and then are realized on experimental conditions. The experimental conditions for the XFEL injector are measured with beam diagnostic devices such as ICT and Faraday cup for charge measurement, a spectrometer for beam energy measurement. In this article, we present the experimental approaches of the beam dynamics study for the XFEL injector.
wpjho@postech.ac.kr (Jangho Park)
NSRRC, Hsinchu
NSRRC, Hsinchu
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
ISP, Novosibirsk
ANL, Argonne, Illinois
The Advanced Photon Source (APS) is a 7-GeV storage ring light source that has been in operation for over a decade. In order to make revolutionary improvements in the performance of the existing APS ring, we are exploring the addition of a 7-GeV energy recovery linac (ERL) to the APS complex. In this paper, we show the possible configuration of such a system, taking into account details of the APS site and the requirement that stored beam capability be preserved. We exhibit a possible configuration for the single-pass, 7-GeV linac. We discuss optical solutions for transport from 10 MeV to 7 GeV and back, including a large turn-around arc that would support 48 additional user beamlines. Tracking results are shown that include incoherent and coherent synchrotron radiation, resulting in predictions of the beamline performance.
ANL, Argonne, Illinois
The Advanced Photon Source (APS) is a 7-GeV storage ring light source that has been in operation for over a decade. Over time, the performance of the APS has been increased by reduction of the emittance from 8 nm to 3.1 nm and by the use of top-up mode. We continue to explore options for improving the performance further. This paper discusses the possible improvements in emittance that could result from the use of damping wigglers. We also discuss rf and space requirements.
ANL, Argonne, Illinois
Two full-length 2.4-m-long undulators, with period lengths 2.3 cm and 2.7 cm, were recently installed in tandem in the 5.6-m-long straight on the storage ring in sector 14. One part of the user research program requires that both undulators be tuned to 12.0 keV and the x-ray intensity maximized. The total intensity is sensitive to the phasing between the undulators, so the distance between the devices must be optimized and the ends tuned appropriately. Because of the different period lengths, the gaps and K values of the undulators will be different: 10.6-mm gap and a K value of 1.17 for the shorter-period device and 15.7-mm gap and a K value of 0.93 for the longer-period device. A special shield was designed and installed between the devices to eliminate interference. Results of magnetic measurements, tuning, and computer simulations of the spectral performance are presented.
ANL, Argonne, Illinois
APS has recently held a round of discussions on upgrade options for the APS storage ring. Several options were discussed that included both storage ring and energy-recovery linac options. Here we present a storage ring lattice that fits into the APS tunnel and has a number of significant improvements over the existing storage ring. The present APS lattice has 40-fold symmetry with each sector having one 5-m-long straight section for insertion device (ID) placement. Each sector also provides one beamline for radiation from the bending magnet. The upgrade lattice preserves locations of the existing insertion devices but provides for increased ID straight section length to accommodate 8-m-long insertion devices. This lattice also decreases emittance by a factor of two down to 1.6 nm rad. And last but not least, it provides two additional 2.1-m-long ID straight sections per sector with one of these straight sections being parallel to the existing bending magnet beamline. We also present dynamic aperture optimization, lifetime calculations, and other nonlinear-dynamics-related simulations.
ANL, Argonne, Illinois
In the recent past, the Advanced Photon Source (APS) was asked by the U. S. Department of Energy to explore a revolutionary upgrade based on emerging energy recovery linac (ERL) technology. In an ERL, the energy of the 7-GeV, 100-mA beam is recovered after the beam passes through user beamlines by decelerating the beam back through the same superconducting linac cavities that accelerated it. The main constraint on this upgrade is that the existing APS beamlines not be disturbed. This requires that the APS storage ring be used as a single-pass transport line in the overall ERL beamline layout. A natural place to locate the ERL is inside the existing APS storage ring ‘‘infield'' area, which has unoccupied space south of the existing APS injector complex. Other important constraints include minimal disturbance of existing building structures and injector beamlines. The existing injector complex would be preserved so that existing operation can be continued through and even possibly beyond ERL commissioning. In this paper, we describe a layout that satisfies these constraints. We also estimate the amount of emittance increase the beam will experience before ring injection.
LBNL, Berkeley, California
The FEL process increases radiation flux by several orders of magnitude above existing incoherent sources, and offers the additional enhancements attainable by optical manipulations of the electron beam: control of the temporal duration and bandwidth of the coherent output, and wavelength; utilization of harmonics to attain shorter wavelengths; and precise synchronization of the x-ray pulse with laser systems. We describe an FEL facility concept based on a high repetition rate RF photocathode gun, that would allow simultaneous operation of multiple independent FELs, each producing high average brightness, tunable over the soft x-ray-VUV range, and each with individual performance characteristics determined by the configuration of the FEL SASE, enhanced-SASE (ESASE), seeded, self-seeded, harmonic generation, and other configurations making use of optical manipulations of the electron beam may be employed, providing a wide range of photon beam properties to meet varied user demands. FELs would be tailored to specific experimental needs, including production of ultrafast pulses even into the attosecond domain, and high temporal coherence (i.e. high resolving power) beams.
LBNL, Berkeley, California
The possibility exists of achieving significantly lower emittances in an electron storage ring by increasing its horizontal betatron tune. However, existing magnet locations and strengths in a given ring may be inadequate to implement such an operational mode. For example, the ALS storage ring could lower its emittance to one third of the current value by increasing the horizontal tune from 14.25 to 16.25. However, this would come with the cost of large chromaticities that could not be corrected with our existing sextupole magnets. We discuss such operational issues and possible options in this paper.
LBNL, Berkeley, California
By "conditioning" an electron beam, through establishing a correlation between transverse action and energy within the beam, the performance of free electron lasers (FELs) can be dramatically improved. Under certain conditions, the FEL can perform as if the transverse emittances of the beam were substantially lower than the actual values. After a brief review of the benefits of beam conditioning, we present a method to generate this correlation through the use of a plasma channel. The strong transverse focusing produced by a dense plasma (near standard gas density) allows the optimal correlation to be achieved in a reasonable length channel, of order 1 m. This appears to be a convenient and practical method for achieving conditioned beams, especially in comparison with other methods which require either a long beamline or multiple passes through some type of ring.
PSI, Villigen
LBNL, Berkeley, California
Nano-tips with high acceleration gradient around the emission surface have been proposed to generate high brightness beams. However, due to the small size of the tip, the charge density near the tip is very high even for a small number of electrons. The Coulomb scattering near the tip can significantly degrade the beam quality and cause extra emittance growth and energy spread. In the paper, we present a numerical study of these effects using a direct relativistic N-body model. We found that emittance growth and energy spread, due to Coulomb scattering, can be significantly enhanced with respect to mean-field space-charge calculations in different parameter regimes.
LBNL, Berkeley, California
The triple bend achromat cell of the ALS has been shown to be very flexible and compact. It has been operated in a low emittance mode and a low momentum compaction mode. In fact the lattice can be operated in a large range of different stable modes. Until recently most of these recently discovered modes had not been explored or even known about. Many of these modes have potentially attractive features as compared with the present operational mode. In this paper we take a step back and look at the general stability limits of the lattice. We employ a technique we call GLASS that allows us to rapidly scan and find all possible stable modes and then characterize their associated properties. In this paper we illustrate how the GLASS technique gives a global and comprehensive vision of the capabilities of the lattice.
CLASSE, Ithaca
In an energy recovery linac (ERL) where beam-loss has to be minimal, and where beam positions and emittances have to be very stable in time, optic errors and beam instabilities due to ion effects have to be avoided. Here we explain why ion clearing electrodes are the least unattractive way of eliminating ions in an ERL and we present calculations of the remnant ion density and its effect on the beam. We also show a design of the clearing electrodes that should be distributed around the accelerator and illustrate their wake-field properties.
Cornell University, Department of Physics, Ithaca, New York
Cockcroft Institute, Lancaster University, Lancaster
KEK, Ibaraki
Recent computational optimizations have demonstrated that it should be possible to construct electron injectors based on photoemission cathodes in very high voltage DC electron guns in which the beam emittance is dominated by the thermal emittance from the cathode. Negative electron affinity photocathodes have been shown to have a naturally low thermal emittance. However, the thermal emittance depends on the illuminating wavelength; the degree of negative affinity; and the band structure of the photocathode material. As part of the development of a high brightness, high average current photoemission electron gun for the injector of an ERL light source, we have measured the thermal emittance from negative affinity GaAs and GaAsP photocathodes. The measurements were made by measuring the electron beam spot size downstream of a counter-wound solenoid lens as a function of the lens strength. Electron beam spot sizes were measured by two techniques - a 20 micron wire scanner, and a CVD diamond screen. Both Gaussian and 'tophat' spatial profiles were used, and measurements were made at several wavelengths. Results will be presented for both cathode types.
Cornell University, Department of Physics, Ithaca, New York
CLASSE, Ithaca
We have constructed a very high voltage photoemission electron gun as the electron source of a high brightness, high average current injector for an energy recovery linac (ERL) synchrotron radiation light source. The source is designed to deliver 100 mA average current in a CW 1300 MHz pulse train (77 pC/bunch). The cathode voltage may be as high as 750 kV. Negative electron affinity photocathodes are employed to obtain small thermal emittances. The electrode structure is assembled without touching any electrode surface. A load-lock system allows cleaning and activation of cathode samples prior to installation in the electron gun. Cathodes are cleaned by heating and exposure to atomic hydrogen, and activated with cesium and nitrogen trifluoride. Two cathode electrode sets, of 316LN stainless steel and Ti4V6Al alloy, have been used. The anode is beryllium. The internal surface of the ceramic insulator of the gun has a high resistivity fired coating, providing a path to drain away charge from field emission. Non-evaporable getters provide a very high pumping speed for hydrogen. Operating experience with this gun will be presented.
UCLA, Los Angeles, California
LLNL, Livermore, California
Compton scattering of intense laser pulses with ultra-relativistic electron beams has proven to be an attractive source of high-brightness x-rays with keV to MeV energies. This type of x-ray source requires the electron beam brightness to be comparable with that used in x-ray free-electron lasers and laser and plasma based advanced accelerators. We describe the development and commissioning of a 1.6 cell RF photoinjector for use in Compton scattering experiments at LLNL. Injector development issues such as RF cavity design, beam dynamics simulations, emittance diagnostic development, results of sputtered magnesium photo-cathode experiments, and UV laser pulse shaping are discussed. Initial operation of the photoinjector is described and transverse phase space measurements are presented.
LLNL, Livermore, California
Thomson-Scattering based systems offer a path to high-brightness high-energy (> 1 MeV) x-ray & gamma-ray sources due to their favorable scaling with electron energy. LLNL is currently engaged in an effort to optimize such a device, dubbed the "Thomson-Radiated Extreme X-Ray" (T-REX) source, targeting up to 680 keV photon energy. Such a system requires precise design of the interaction between a high-intensity laser pulse and a high-brightness electron beam. Presented here are the optimal design parameters for such an interaction, including factors such as the collision angle, focal spot size, optimal bunch charge and laser intensity, pulse duration, and laser beam path. These parameters were chosen based on extensive modelling using PARMELA and in-house, well-benchmarked scattering simulation codes. Also discussed are early experimental results from the newly commissioned system.
LLNL, Livermore, California
UCLA, Los Angeles, California
A 2.1 GeV electron storage ring can serve as a third-generation light source for photon energies of 1-2000 eV. We design a ring with emittance of 1.5 nm-rad, circumference of 215 m, and twelve 5.5 m long straight sections. With a 100 MHz radiofrequency (rf) system, the computed Touschek current-lifetime product is 2800 mA-hr. Two passive fifth-harmonic cavities may be used to suppress parasitic coupled-bunch instabilities while increasing the bunchlength and lifetime by a factor of four. For stable operation with ring currents up to 600 mA, microwave-instability simulations indicate that the reduced longitudinal impedance should not exceed 1.5Ω.
SLAC, Menlo Park, California
DESY, Hamburg
The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presently under construction at SLAC. The injector section, from drive-laser and RF photocathode gun through the first bunch compressor chicane, was installed during the Fall of 2006. Initial system commissioning with an electron beam takes place in the Spring and Summer of 2007. The second phase of construction, including the second bunch compressor and the FEL undulator, will begin later, in the Fall of 2007. We report here on experience gained during the first phase of machine commissioning, including RF photocathode gun, linac booster section, energy spectrometers, S-band and X-band RF systems, the first bunch compressor stage, and the various beam diagnostics.
Jefferson Lab, Newport News, Virginia
Jefferson Lab, Newport News, Virginia
DESY Zeuthen, Zeuthen
Injector gun design is an iterative process where the designer optimizes a few nonlinearly interdependent beam parameters to achieve the required beam quality for a particle accelerator. Few tools exist to automate the optimization process and thoroughly explore the parameter space. The challenging beam requirements of new accelerator applications such as light sources and electron cooling devices drive the development of RF and SRF photo injectors. RF and SRF gun design is further complicated because the bunches are space charge dominated and require additional emittance compensation. A genetic algorithm has been successfully used to optimize DC photo injector designs for Cornell* and Jefferson Lab**, and we propose studying how the genetic algorithm techniques can be applied to the design of RF and SRF gun injectors. In this paper, we report on the initial phase of the study where we model and optimize gun designs that have been benchmarked with beam measurements and simulation.
* I. Bazarov, et al., "Multivariate Optimization of a High Brightness DC Gun Photoinjector", PRST-AB 2005.** F. Hannon, et al., "Simulation and Optimisation of a 100 mA DC Photoinjector", EPAC 2006.
Jefferson Lab, Newport News, Virginia
Notional designs for ERL-driven high average power free electron lasers often invoke amplifier-based architectures. To date, however, amplifier FELs have been limited in average power output to values several orders of magnitude lower than those demonstrated in optical-resonator based systems; this is due at least in part to the limited electron beam powers available from their driver accelerators. In order to directly contrast the performance available from amplifiers to that provided by high-power cavity-based resonators, we have developed a scheme to test an amplifier FEL in the JLab SRF ERL driver. We describe an accelerator system design that can seamlessly and non-invasively integrate a 10 m wiggler into the existing system and which provides, at least in principle, performance that would support high-efficiency lasing in an amplifier configuration. Details of the design and an accelerator performance analysis will be presented.
BNL, Upton, Long Island, New York
A notable feature of the proposed National Synchrotron Light Source II is that the vertical emittance is close to the diffraction limit of 1 Angstrom. With such a small emittance, the brightness is strongly affected by the longitudinal parameters, such as the momentum spread. Various effects are discussed and tolerances on the longitudinal parameters will be given. The lower level RF feedback system will be designed based on these tolerances.
BNL, Upton, Long Island, New York
BNL, Upton, Long Island, New York
MIT, Middleton, Massachusetts
A new high-brightness synchrotron light source (NSLS-II) is under design at BNL. The 3-GeV NSLS-II storage ring has a double-bend achromatic lattice with damping wigglers installed in zero-dispersion straights to reduce the emittance below 1nm. In this note, we present an overview of the impact of collective effects upon the performance of the storage ring. Subjects discussed include Touschek lifetime, intra-beam scattering, instability thresholds due to ring impedance, and use of a third-harmonic Landau cavity.
BNL, Upton, Long Island, New York
IUCF, Bloomington, Indiana
BNL, Upton, Long Island, New York
BNL, Upton, Long Island, New York
We present conceptual design of the NSLS-II injection system. The injection system consists of low-energy linac, booster and transport lines. We review the requirements on the injection system imposed by the storage ring design and means of meeting these requirements. We discuss main parameters and layout of the injection system components.
BNL, Upton, Long Island, New York
BNL, Upton, Long Island, New York
UMD, College Park, Maryland
LANL, Los Alamos, New Mexico
SAIC, Burlington, Massachusetts
A recently developed model* of the emittance and brightness of a photocathode based on the evaluation of the moments of the electron emission distribution function admits an analytical solution for the zero-field and zero-temperature asymptotic model. Here, the model has been extended to account for the critical modifications of temperature and field dependence, which are tied to material issues with the cathode. Temperature impacts the nature of scattering within the photoemitter material and therefore affects quantum efficiency significantly. Field changes the emission probability at the surface barrier, and is particularly important for low work function coatings, as occur for the cesiated surfaces characteristic of our controlled porosity dispenser photocathodes. Extensions of the theoretical models shall be given, followed by an analysis of their comparison with numerical simulations of the intrinsic emittance and brightness of a photocathode. The methodology is designed to facilitate the development of photoemission models into comprehensive particle-in-cell (PIC) codes to address issues otherwise not readily treated, e.g., variation in surface coverage and topology.
* K. L. Jensen, P. G. O'Shea, D. W. Feldman, and N. A. Moody, Applied Physics Letters 89, 224103 (2006).
UMAN, Manchester
* C. Beard and R. M. Jones, EUROTeV-Report-2006-103** C. Beard and J. Smith, EPAC06 Proc. MOPLS070
TRIUMF, Vancouver
ACCEL, Bergisch Gladbach
GSI, Darmstadt
ORNL, Oak Ridge, Tennessee
The GSI UNILAC, a heavy ion linac originally dedicated for low current beam operation, together with the synchrotron SIS 18 will serve as an high current injector for FAIR (International Facility for Antiproton and Ion Research). The UNILAC post stripper accelerator consists of five Alvarez tanks with a final energy of 11.4 MeV/u. In order to meet the requirements of FAIR (15emA 238U28+, transverse normalised emittances of 0.8mm mrad and 2.5mm mrad) an UNILAC upgrade program is foreseen to increase the primary beam intensity as well as the beam brilliance. A detailed understanding of the beam dynamics during acceleration and transport of space charge dominated beams is necessary. For this purpose the study of the beam brilliance dependency on the phase advances in the Alvarez DTL is suited. Machine investigations were performed with various beam diagnostics devices established in the UNILAC. Measurements done in 2006 using an high intensity heavy ion beam coincide with the beam dynamics work package of the European JRA "High Intensity Pulsed Proton Injector" (HIPPI). Results of these measurements are presented as well as corresponding beam dynamics simulations.
IAP, Frankfurt am Main
IAP, Frankfurt am Main
GSI, Darmstadt
BNL, Upton, Long Island, New York
IAP, Frankfurt am Main
FZJ, Julich
INFN-Ferrara, Ferrara
* Conceptual Design Report for an International Facility for Antiprotonand Ion Research, www.gsi.de/GSI-future/cdr.** PAX Technical Proposal, www.fz-juelich.de/ikp/pax.
INFN/LNF, Frascati (Roma)
BINP SB RAS, Novosibirsk
KEK, Ibaraki
BINP SB RAS, Novosibirsk
For the KEKB Accelerator Group.
INFN/LNF, Frascati (Roma)
KEK, Ibaraki
BNL, Upton, Long Island, New York
CERN, Geneva
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
Liverpool University, Science Faculty, Liverpool
* P. Raimondi, "New Developments for SuperB Factories", Invited talk, this Conference
Utsunomiya University, Utsunomiya
KEK, Ibaraki
* E. Nakamura, et al., "A Modification Plan of the KEK 500MeV Booster to an All-ion Accelerators (An Injector-free Synchrotron)", PAC07.
JINR, Dubna, Moscow Region
IBA, Louvain-la-Neuve
CERN, Geneva
BNL, Upton, Long Island, New York
Fermilab, Batavia, Illinois
CERN, Geneva
CERN, Geneva
ORNL, Oak Ridge, Tennessee
CERN, Geneva
Fundacion Tekniker, Elbr (Guipuzkoa)
University of Warwick, Coventry
Bilbao, Faculty of Science and Technology, Bilbao
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Elytt Energy, Madrid
STFC/RAL/ISIS, Chilton, Didcot, Oxon
CERN, Geneva
CERN and RAL are working in parallel to develop Front Ends for future particle accelerators. At CERN the Front End will be part of LINAC4, a potential replacement for the Linac2 accelerator, whilst at RAL the Front End is intended to demonstrate that a high current, high quality chopped beam is achievable and that the design could be used as part of a Proton Driver for a future Neutrino Factory. The two Front End designs have many similarities and basically consist of four main components: an H- ion source, a Low Energy Beam Transport (LEBT) matching into a Radio-Frequency Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT) line with a fast beam chopper. The beam choppers are different in the two designs and it is important to compare the effectiveness of the two methods of operation. This paper describes a simulation study of high intensity beam dynamics and beam transport when the RAL and CERN MEBT designs are each fed into the same CERN structure for LINAC4.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
ANL, Argonne, Illinois
Northern Illinois University, DeKalb, Illinois
A multi-charge-state injector for high-intensity heavy-ion LINAC is being developed at ANL. The injector consists of an all-permanent magnet ECR ion source, a 100 kV platform and a Low Energy Beam Transport (LEBT). The latter comprises two 60-degree bending magnets, electrostatic triplets and beam diagnostics stations. The first results of beam measurements in the LEBT will be presented.
ANL, Argonne, Illinois
The Advanced Exotic Beam Laboratory (AEBL) being developed at ANL consists of an 833 MV heavy-ion driver linac capable of producing uranium ions up to 200 MeV/u and protons to 580 MeV with 400 kW beam power. We have designed all accelerator components including a two charge state LEBT, an RFQ, a MEBT, a superconducting linac, a stripper section and beam switchyard. We present the results of an optimized linac design and end-to-end simulations which include possible machine errors.
Fermilab, Batavia, Illinois
Fermilab, Batavia, Illinois
A 0.1 A, 4.3 MeV DC electron beam is routinely used to cool 8 GeV antiprotons in Fermilab's Recycler storage ring. While the primary function of the electron cooler is to increase the longitudinal phase-space density of the antiprotons, significant transverse cooling rates have been observed as well. Numerical characterization of electron cooling is done by two types of measurements: friction force measurements by the voltage jump method and diffusion/cooling rates measurements. The paper will present the recent measurement results and will compare them to a non-magnetized model.
CERN, Geneva
Fermilab, Batavia, Illinois
Upon the termination of the Fermilab Collider program, the current Recycler anti-proton storage ring will be converted to a proton pre-injector for the Main Injector synchrotron. This is scheduled to increase the beam power for the 120 GeV Neutrino program to upwards of 700KW. A transport line that can provide direct injection from the Booster to the Recycler while preserving direct injection from the Booster into the Main Injector and the 8 GeV Booster Neutrino program will be discussed,and its concept design will be presented.
Fermilab, Batavia, Illinois
Fermilab, Batavia, Illinois
LBNL, Berkeley, California
An over-dense microwave driven ion source capable of producing deuterium (or hydrogen) beams at 100-200 mA/cm2 with an atomic fraction > 90% was designed as a part of an Accelerator Driven Neutron Source (ADNS). The ion source was tested with an electrostatic low energy beam transport section (LEBT) and measured emittance data was compared to PBGUNS simulations. In our design a 40 mA D+ beam is produced from a 6 mm diameter aperture using a 60 kV extraction voltage. The LEBT section consists of 5 electrodes arranged to form 2 Einzel lenses that focus the beam into the RFQ entrance. To create the ECR condition, 2 induction coils are used to generate a ~875 Gauss magnetic field on axis inside the source chamber. To prevent HV breakdown in the LEBT, a magnetic field clamp is necessary to minimize the field in this region. The microwave power is matched to the plasma by an autotuner. A significant improvement in the atomic fracion of the beam was achieved by installing a boron nitride liner inside the ion source
NSCL, East Lansing, Michigan
Rare Isotope Beams (RIBs) are created at the National Superconducting Cyclotron Laboratory (NSCL) by the in-flight particle fragmentation method. A novel system is proposed to stop the RIBS in a helium filled gas system followed by reacceleration that will provide opportunities for an experimental program ranging from low-energy Coulomb excitation to transfer reaction studies of astrophysical reactions. The beam from the gas stopper will first be brought into a Electron Beam Ion Trap (EBIT) charge breeder on a high voltage platform to increase its charge state and then accelerated initially up to about 3 MeV/u by a system consisting of an external multi-harmonic buncher and a radio frequency quadrupole (RFQ) followed a superconducting linac. The superconducting linac will use quarter-wave resonators with bopt of 0.047 and 0.085 for acceleration and superconducting solenoid magnets for transverse focusing. The paper will discuss the accelerator system design and present the end-to-end beam dynamics simulations.
NSCL, East Lansing, Michigan
NSCL, East Lansing, Michigan
Far-Tech, Inc., San Diego, California
Electron cyclotron resonance ion sources (ECRIS) that generate multiply charged ions reduce the cost to produce radioactive ion beams by reducing the accelerating voltage needed to achieve the desired beam energy. FAR-TECH, Inc. is developing an integrated suite of numerical codes to simulate ECRIS ion capture, charge breeding, and ion extraction. Ion extraction is modeled with a particle in cell (PIC) code. Since the ion dynamics are strongly dependent on the behavior of the plasma sheath at the boundary between the ECRIS plasma and the ion optics, the PIC code uses an adaptive Poisson solver to accurately resolve the potential drop in the sheath. Results of the integrated ECRIS model will be presented, including calculations of extraction efficiency with multiple ion species.
BNL, Upton, Long Island, New York
A part of a new EBIS-based heavy ion preinjector, the low energy beam transport (LEBT) section between the high current EBIS and the RFQ is a challenging design, because it must serve many functions. In addition to the requirement to provide an efficient matching between the EBIS and the RFQ, this line must serve as a fast switchyard, allowing singly charged ions from external sources to be transported into the EBIS trap region, and extracted, highly charged ions to be deflected to off-axis diagnostics (time-of-flight, or emittance). The space charge of the 5-10 mA extracted heavy ion beam is a major consideration in the design, and the space charge force varies for different ion beams having Q/m from 1-0.16. The line includes electrostatic lenses, spherical and parallel-plate deflectors, magnetic solenoid, and diagnostics for measuring current, charge state distributions, emittance, and profile. A prototype of this beamline has been built, and results of tests will be presented.
KEK, Ibaraki
CERN, Geneva
A small angle (< 1mrad) crab scheme is an attractive option for the LHC luminosity upgrade to recover the geometric luminosity loss from the finite crossing angle, which steeply increases to unacceptable levels as the IP beta function is reduced below its nominal value. The crab compensation in the LHC can be accomplished using only two sets of deflecting rf cavities, placed in collision-free straight sections of LHC to nullify the crossing angles at IP1 & IP5. We present IR optics configurations with low-angle crab crossing, study the beam-beam performance and proton-beam emittance growth in the presence of crab compensation, lattice errors, crab RF noise sources. We also explore a 400MHz superconducting cavity design and discuss the pertinent RF challenges.
BNL, Upton, Long Island, New York
CERN, Geneva
SLAC, Menlo Park, California
Fermilab, Batavia, Illinois
LBNL, Berkeley, California
A DC wire has been installed in RHIC to explore the long-range beam-beam effect, and test its compensation. We report on experiments that measure the effect of the wire's electro-magnetic field on the beam's lifetime and tune distribution, and accompanying simulations.
BNL, Upton, Long Island, New York
Gold ions for the 2007 run of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) are accelerated in the Tandem, Booster and AGS prior to injection into RHIC. The setup and performance of this chain of accelerators will be reviewed with a focus on improvements in the quality of beam delivered to RHIC. In particular, more uniform stripping foils between Booster and AGS, and a new bunch merging scheme in AGS promise to provide beam bunches with reduced longitudinal emittance for RHIC.
BNL, Upton, Long Island, New York
Beam-beam effects present one of major factors limiting the luminosity of colliders. In the linac-ring option of eRHIC design, an electron beam accelerated in a superconducting energy recovery linac collides with a proton beam circulating in the RHIC ring. There are some features of beam-beam effects which require careful examination in linac-ring configuration. First, the beam-beam interaction can induce specific head-tail type instability of the proton beam referred to as 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 beam quality is good enough for the energy recovery pass. In addition, fluctuations of electron beam current and/or electron beam size, as well as transverse offset, can cause proton beam emittance growth. The tolerances for those factors should be determined and possible countermeasures should be developed to mitigate the emittance growth. In this paper, a soft Gaussian strong-strong simulation is used to study all of mentioned beam-beam interaction features and possible techniques to reduce the emittance growth.
BNL, Upton, Long Island, New York
IAP, Frankfurt am Main
The EBIS (Electron Beam Ion Source) Project at Brookhaven National Laboratory is in the second year of a four-year project. It will replace the Tandem Van de Graaff accelerators with an EBIS, an RFQ, and one IH Linac cavity as the heavy ion preinjector for the Relativistic Heavy Ion Collider (RHIC), and for the NASA Space Radiation Laboratory (NSRL). The preinjector will provide all ions species, He to U, (Q/m>0.16) at 2 MeV/amu at a repetition rate of 5 Hz, pulse length of 10–40 μs, and intensities of ~2.0 mA. End-to-end simulations (from EBIS to the Booster injection) as well as error sensitivity studies will be presented and physics issues will be discussed.
#Raparia@bnl.gov
BNL, Upton, Long Island, New York
We explore the possibility of using two non-scaling FFAG with a smaller number of distributed RF cavities for a high power heavy ion driver. The pulsed heavy ion source would consist of an Electron Beam Ion Source (EBIS), fed continuously from a high charge state Electron Cyclotron Resonance (ECR) source. The Radio Frequency Quadrupole (RFQ) and a short 10 MeV/u linac would follow the ion source. Microseconds long heavy ion beam bunches from the EBIS would be injected in a single turn into a multi-pass small aperture non-scaling Fixed Field Alternating Gradient (FFAG) accelerator. The heavy ion maximum kinetic energy is assumed to be 400 MeV/u with a total of 400 kW power for uranium ion beams. Partially stripped heavy ions would be accelerated from 10 MeV/u to 67 MeV/u with a first non-scaling FFAG, while, after further stripping, a second non-scaling FFAG would accelerate from 67 to 400 MeV/u.
BNL, Upton, Long Island, New York
The beam emittance growth in RHIC polarized proton runs has a dependence on the dynamic pressure rise, which is caused by the electron cloud and peaked at the end of the beam injection and the early energy acceleration. This emittance growth is usually presented without beam instability, and it is slower than the ones above the instability threshold. The effect on the machine luminosity, nevertheless, is significant, and it is currently a limiting factor in machine performance. The electron cloud is substantially reduced at the store, the emittance growth there has no dependence on the bunch spacing and instead it has a clear dependence on the beam-beam parameter. The results of the machine operation and beam studies will be reported.
UCLA, Los Angeles, California
Fermilab, Batavia, Illinois
Rochester University, Rochester, New York
Northern Illinois University, DeKalb, Illinois
Focusing of a 15 MeV, 19 nC electron bunch by an underdense plasma lens operated just beyond the threshold of the underdense condition has been demonstrated in experiments at the Fermilab NICADD Photoinjector Laboratory (FNPL). The strong 1.9 cm focal-length plasma-lens focused both transverse directions simultaneously and reduced the minimum area of the beam spot by a factor of 23. Analysis of the beam-envelope evolution observed near the beam waist shows that the spherical aberrations of this underdense lens are lower than those of an overdense plasma lens, as predicted by theory. Correlations between the beam charge and the properties of the beam focus corroborate this conclusion. Time resolved measurements of the focused electron bunch are also reported and all results are compared to simulations.
Jefferson Lab, Newport News, Virginia
IUCF, Bloomington, Indiana
BTG, New York
BNL, Upton, Long Island, New York
ANL, Argonne, Illinois
Experiments on the study of fundamental quark-gluon structure of nucleons require an electron-light ion collider of a center of mass energy from 20 to 65 GeV at luminosity level of 1035 cm-2s-1 with both beams polarized. A CEBAF accelerator based ring-ring collider of 7 GeV electrons/positrons and 150 GeV light ions is envisioned as a possible next step after the 12 GeV CEBAF Upgrade. The developed ring-ring scheme takes advantage of the existing polarized continuous electron beam and SRF linac, the green-field design of the collider rings and the ion accelerator complex with electron cooling. We report results of our design studies of the ring-ring version of an electron-light ion collider of the required luminosity.
Tech-X, Boulder, Colorado
BNL, Upton, Long Island, New York
ORNL, Oak Ridge, Tennessee
AES, Princeton, New Jersey
Fermilab, Batavia, Illinois
Jefferson Lab, Newport News, Virginia
BINP SB RAS, Novosibirsk
JINR, Dubna, Moscow Region
The physics interest in a luminosity upgrade of RHIC requires the development of a cooling-frontier facility. Detailed cooling calculations have been made to determine the efficacy of electron cooling of the stored RHIC beams. This has been followed by beam dynamics simulations to establish the feasibility of creating the necessary electron beam. Electron cooling of RHIC at collisions requires electron beam energy up to about 54 MeV at an average current of between 50 to 100 mA and a particularly bright electron beam. The accelerator chosen to generate this electron beam is a superconducting Energy Recovery Linac (ERL) with a superconducting RF gun with a laser-photocathode. An intensive experimental R&D program engages the various elements of the accelerator: Photocathodes of novel design, superconducting RF electron gun of a particularly high current and low emittance, a very high-current ERL cavity and a demonstration ERL using these components.
Fermilab, Batavia, Illinois
The Recycler is the primary antiproton repository for the Tevatron collider at Fermilab. Stored antiproton beam intensity has been steadily increased to about 450·1010 over the last three years. We have used the technique of longitudinal momentum mining* in the Recycler to extract constant intensity and constant longitudinal emittance antiproton bunches for collider operation since early 2005. Since then, the Recycler has played a critical role in the luminosity performance of the Tevatron; the peak proton-antiproton luminosity has been raised by a factor of about three and a world record luminosity of 2.31·1032cm-2s-1 has been achieved. Recently, many improvements have been implemented in the antiproton mining and stacking schemes used in the Recycler to handle higher intensity beam. In this paper we discuss morphing during antiproton stacking, reducing longitudinal emittance dilution, and use of soft mining buckets to maintain low peak density and control the beam instability during mining. In addition we present past and current performance of mining and beam stacking RF manipulations.
* C. M. Bhat, Phys. Letts. A Vol. 330 (2004), p 481
Polarized positron and electron beams are ideal for searching for new physics at the International Linear Collider (ILC). In order to properly orient and preserve the polarization of both beams at the Interaction Point (IP) the beam polarization must be manipulated by a series of spin rotators along the beam line. Furthermore, the polarization for both beams should be known with a relative uncertainty of about 0.5% or better, therefore, all sources of depolarization along the ILC should be identified. We report on a spin rotator design for the ILC and polarization studies between Damping Ring extraction and the Interaction Point.
SLAC, Menlo Park, California
Fermilab, Batavia, Illinois
International Linear Collider (ILC) is a proposed electron-positron accelerator requiring very small spot-size at the interaction point, and thus necessitates very tight tolerances on beamline elements. For static tuning of the machine a few methods like dispersion-free steering (DFS) or kick minimization (KM) techniques was proposed. The further suppression of emittance growth can be achieved by using close orbit emittance bumps. Stability of ILC is determined by the stability of the site, additional noises of beamline component, energy and kicker jitter and performance of the train-to-train and intra-train feedback. We discuss the performances of the Adaptive Alignment technique, which keeps accelerator dynamically aligned in presence of ground motion an technical noises. This presentation is an overview of two posters THPMN107 and THPMN108, presented at PAC07.
BNL, Upton, Long Island, New York
Stochastic cooling of 100 GeV/nucleon bunched beams has been achieved in the Relativistic Heavy Ion Collider (RHIC). The physics and technology of the longitudinal cooling system are discussed, and plans for a transverse cooling system are outlined.
UMD, College Park, Maryland
A common challenge for accelerator systems is to maintain beam quality and brightness over the usually long distance from the source to the target. In order to do so, knowledge of the beam distribution in both configuration and velocity space along the beam line is needed. However, measurement of the velocity distribution can be difficult, especially for beams with strong space charge. Here we present a simple and portable tomographic method to map the beam phase space, which can be used in the majority of accelerators. The tomographic reconstruction process has first been compared with results from simulations using the particle-in-cell code WARP. Results show excellent agreement even for beams with extreme space charge and exotic distributions. Our diagnostic has also been successfully demonstrated experimentally on the University of Maryland Electron Ring, a compact ring designed to study the transverse dynamics of beams in both emittance and space charge dominated regimes. Special emphasis is given to intense beams where our phase space tomography diagnostic is used to shed light on the consequences of the space charge forces on the transport of these beams.
BNL, Upton, Long Island, New York
IUCF, Bloomington, Indiana
USTC/NSRL, Hefei, Anhui
We have developed the mathod to determine the permittivity and permeability of Kanthal alloy available. The alloy is coated on the inside walls of disk-loaded cavities,which is used for the collinear load. The collinear load absorbs the remaining rf-power over the last cells of the section while still accelerating the beam. Based on the experimental results of the permittivity and permeability,the computation study of the constant power-loss collinear load has been made by Microwave Studio. The design data about the S-band collinear load are present.
Texas A&M University, College Station, Texas
A polyhedral superconducting cavity is being developed for possible use in linac colliders. In side view it has the contour of a Tesla-type multi-cell string. The surfaces of the cavity are formed by bonding flat foils to solid copper wedge-shaped segments, so that the end view is a polyhedron of such segments. Several features of this structure make it interesting for linac colliders: the cavity segments are totally open for cleaning, polishing, and inspection until the final assembly step; narrow slot gaps at the boundaries between segments strongly suppress all deflecting modes without penalty to the accelerating mode; the solid copper substrate accommodates cooling channels and eliminates the need for an immersion cryostat; and the open geometry makes it possible to utilize advanced superconductors (e.g. multi-layer Nb/Nb3Sn, YBCO, MgB2) on the cavity surface, opening the possibility of higher gradients.
CLASSE, Ithaca
A 1300 MHz deflecting cavity will be used for beam slice emittance measurements, and to study the temporal response of negative electron affinity photocathodes in the ERL injector currently under construction at Cornell University. A single-cell TM110-mode cavity was designed to deflect the beam vertically. The paper describes the cavity shape optimization procedure, its mechanical design and performance at low RF power.
CLASSE, Ithaca
Six 1300 MHz superconducting niobium 2-cell cavities are manufactured for the prototype of Cornell ERL injector to boost the energy of a high current, low emittance beam produced by a DC gun. Designed for high current beam acceleration, these cavities have new characteristics as compared to previously developed low-current cavities such as those for TTF. Precision manufacture is emphasized for a better straightness of the cavity axis so as to avoid unwanted emittance dilution. We present the manufacturing, processing and vertical test performance of these cavities. We also present the impact of new cavity characteristics to the cavity performance as learnt from vertical tests. Solutions for improving cavity performance are discussed.
LANL, Los Alamos, New Mexico
NSTec, Los Alamos, New Mexico
SAIC, Los Alamos, New Mexico
INFN/LNF, Frascati (Roma)
UCLA, Los Angeles, California
Rome University La Sapienza, Roma
The hybrid photoinjector is a high current, low emittance photoinjector/accelerator and is under design and collaboration at Roma University La Sapienza, INFN - Laboratori Nazionali di Frascati and the UCLA Particle Beam Physics Lab. The hybrid standing wave-traveling wave photoinjector uses a coupling cell to divide power between a high-field 1.6 cell standing wave photoinjector, for electron emission and collection, and a low power traveling wave accelerator, for acceleration to desired energies at low emittances. Simulation results show promising beam properties of less than 4 mm-mrad emittance, energy spreads of 1.5%, and currents as high as 1.2 kA at energies of 21 MeV. We report on the progress of RF design and results of cold test RF measurements at the UCLA Pegasus Laboratory, including methods for measurements and difficulties arising in the transition from simulation to physical measurements.
BNL, Upton, Long Island, New York
CLASSE, Ithaca
Cornell University is developing and fabricating a SRF injector cryomodule for the acceleration of the high current (100 mA) beam in the Cornell ERL prototype and ERL light source. Major challenges include emittance preservation of the low energy, ultra low emittance beam, cw cavity operation, and strong HOM damping with efficient HOM power extraction. Prototypes have been completed for the 2-cell niobium cavity with helium vessel, coaxial blade tuner with piezo fine tuners, twin high power input couplers, and beam line HOM absorbers loaded with ferrites and ceramics. Axial symmetry of HOM absorbers, together with two symmetrically placed input couplers per cavity, avoids transverse on-axis fields, which would cause emittance growth. A one-cavity cryostat has been designed following concepts of the TTF cryostat, and is presently under fabrication and assembly. The cryostat design has been optimized for precise cavity alignment, good magnetic shielding, and high dynamic cryogenic loads from the RF cavities, input couplers, and HOM loads. In this paper we report on the status of the assembly and first test of the one-cavity test cryostat.
ORNL, Oak Ridge, Tennessee
RAS/INR, Moscow
SNS Linac utilizes several accelerating structures operating at two frequencies. CCL and SCL operate at 805 MHz while 402.5 MHz is used for RFQ and DTL. Beam transfer from the previous part of the accelerator to the subsequent one requires careful longitudinal matching to improve beam transmission and to minimize beam losses. Longitudinal beam parameters have been investigated with the help of three Bunch Shape Monitors installed in the intersegments of the first CCL Module. The results of bunch shape observations for different accelerator settings are presented. Longitudinal beam emittance has been measured and optimized. Longitudinal beam halo has been evaluated as well.
Accelerator of muon has to have very large acceptance and very quick acceleration. Recent study shows that FFAGs (in particular non-scaling) are one of the most promising candidates for muon accelerators as building block for a neutrino factory. There are, however, some unresolved problems which should be studied in more detail. We will talk about mostly beam dynamics issues of the muon accelerators, not only FFAG, but other candidates such as linac and RLA and compare their performance.
Jefferson Lab, Newport News, Virginia
UMD, College Park, Maryland
Optical Transition Radiation Interferometry (OTRI) has proven to be effective tool for measuring rms beam divergence. We present rms emittance measurement results of the 115 MeV energy recovery linac at the Thomas Jefferson National Laboratories Free electron Laser using OTRI. OTRI data from both near field beam images and far field angular distribution images give evidence of two spatial and angular distributions within the beam. Using the unique features of OTRI we segregate the two distributions of the beam and estimate separate rms emittance values for each component.
USP/LAL, Sao Paulo
The injector linac consists of a beam conforming stage, with chopper and buncher systems, and two acceleration structures, the first one with variable β, and the second one divided into two parts with different β. There are two 3-mm diameter collimators, the first at the entrance to the first chopper cavity and the second at the entrance to the first acceleration structure. The beam focalization is made by solenoids, and correcting coils are provided for steering. In this work we describe the commissioning of the optical lattice of the conforming beam stage. The first beam images are shown.
UCLA, Los Angeles, California
INFN/LASA, Segrate (MI)
Based on our experience on photocathode production, we present in this paper the results of the application of different optical diagnostic techniques on fresh and used photocathodes. These techniques allow to study effects like non uniformity, cathode aging, etc. In particular, photocathode optical parameters and QE characterization, both done at different wavelengths, give fundamentals information for the construction of a model of the photoemission process to be applied to Cs2Te photocathodes. These studies are useful for further improving key cathode features, such as its robustness and lifetime as well as to study and control the photocathodes thermal emittance.
ISIR, Osaka
* J. Yang, T. Kondoh, K. Kan, T. Kozawa, Y. Yoshida and S. Tagawa: Nucl. Instrum. Methods Phys. Res., Sect. A 556 (2006) 52-56
ISIR, Osaka
CERN, Geneva
CERN, Geneva
Dynamic imperfections in future linear colliders can lead to a significant luminosity loss. We discuss different orbit feedback strategies in the main linac that can mitigate the emittance dilution and compare their efficiency. We also address the impact of ground motion in the beam delivery system and the potential cures.
Uppsala University, Uppsala
CERN, Geneva
Misalignments in the main linac of future linear colliders can lead to significant emittance growth. Beam-based alignment algorithms, such as Dispersion Free Steering (DFS), are necessary to mitigate these effects. We study how to use the Bunch Compressor to create the off-energy beams necessary for DFS and discuss the effectiveness of this method.
CERN, Geneva
Complex beam-based alignment procedures are needed in future linear colliders to reduce the negative effects of static imperfections in the main linac on the beam emittance. The efficiency of these procedures could be affected by dynamic imperfections during their application. In this paper we study the resulting emittance growth.
Liverpool University, Science Faculty, Liverpool
Jefferson Lab, Newport News, Virginia
Muons, Inc, Batavia
Parametric-resonance ionization cooling (PIC) is a muon-cooling technique that is useful for low-emittance muon colliders. This method requires a well-tuned focusing channel that is free of chromatic and spherical aberrations. In order to be of practical use in a muon collider, it also necessary that the focusing channel be as short as possible to minimize muon loss due to decay. G4Beamline numerical simulations are presented of a compact PIC focusing channel in which spherical aberrations are minimized by using design symmetry.
Fermilab, Batavia, Illinois
Jefferson Lab, Newport News, Virginia
The idea of coalescing multiple muon bunches at high energy to enhance the luminosity of a muon collider provides many advantages. It circumvents space-charge, beam loading, and wakefield problems of intense low-energy bunches while restoring the synergy between muon colliders and neutrino factories based on muon storage rings. A sampling of initial conceptual design work for a coalescing ring is presented here.
Fermilab, Batavia, Illinois
Muons, Inc, Batavia
The study of rare processes using stopping muon beams provides access to new physics that cannot be addressed at energy frontier machines. The flux of muons into a small stopping target is limited by the kinematics of the production process and by stochastic processes in the material used to slow the particles. Innovative muon beam cooling techniques are being applied to the design of stopping muon beams in order to increase the event rates in such experiments. Such intense stopping beams will also aid the development of applications such as muon spin resonance and muon-catalyzed fusion.
Fermilab, Batavia, Illinois
Recently we have measured the transverse emittance using both multi-screen as well as muli-slit methods for a range of electron beam intensities from 1 nC to 4 nC at A0 Photoinjector facility at Fermilab. The data have been taken with un-stacked 2.5 ps laser pulse. In this paper we report on these measurements and compare the results with the predictions from beam dynamics calculations using ASTRA and General Particle Tracer including 3D space charge effects.
Fermilab, Batavia, Illinois
Within the framework of the Fermilab Muon Collider Task Force, the possibility of developing a dedicated muon test beam for cooling experiments has been investigated. Cooling experiments can be performed in a very low intensity muon beam by tracking single particles through the cooling device. With sufficient muon intensity and large enough cooling decrement, a cooling demonstration experiment may also be performed without resolving single particle trajectories, but rather by measuring the average size and position of the beam. This allows simpler, and thus cheaper, detectors and readout electronics to be used. This paper discusses muon production using 400MeV protons from the linac, decay channel and beamline design, as well as the instrumentation required for such an experiment, in particular as applied to testing the Helical Cooling Channel (HCC) proposed by Muons Inc.
Fermilab, Batavia, Illinois
Fermilab, Batavia, Illinois
This paper reports the studies of using global emittance tuning bumps to limit the emittance growth to very small values in the main linac of the proposed International Linear Collider (ILC) machine. Simulation studies indicate that closed-orbit emittance bumps, when used after local or quasi-local beam based alignment techniques, can be utilized to further suppress the emittance growth in the ILC main linac. A series of simulations are performed to find the optimal number of bumps and their locations. A more general method of optimizing the emittance bumps in the ILC main linac is also discussed.
Fermilab, Batavia, Illinois
The proposed International Linear Collider (ILC) machine requires extremely small transverse emittances of the beam to achieve desired luminosity. A very precise alignment of the beamline elements, both in main linac and in beam delivery system, is required to limit the emittance growth. However, ground motion (GM) and technical noise continuously misaligns the elements and hence spoils the effect of alignment. It is thus very important to understand and analyze the effect of GM on the performance of ILC. Also, it is imperative to find an effective dynamic alignment procedure to preserve the transverse emittances in the presence of GM. In this paper we study the effect of GM and technical noise on the proposed ILC main linac. Initial alignment of the Linac is performed through one-to-one and dispersion free steering (DFS). We then study "Adaptive Alignment" method to mitigate the effects of GM and technical noise.
Muons, Inc, Batavia
Fermilab, Batavia, Illinois
MANX is an experiment to prove that effective six-dimensional (6D) muon beam cooling can be achieved a Helical Cooling Channel (HCC) using ionization-cooling with helical and solenoidal magnets in a novel configuration. The aim is to demonstrate that 6D muon beam cooling is understood well enough to plan intense neutrino factories and high-luminosity muon colliders. The experiment consists of the HCC magnets that envelop a liquid helium energy absorber, upstream and downstream instrumentation to measure the particle or beam parameters before and after cooling, and emittance matching sections between the detectors and the HCC. We describe and compare the experimental configuration for both single particle and beam profile measurement techniques based on G4Beamline simulations.
LBNL, Berkeley, California
New generation accelerator-based X-ray light sources require high quality beams with high average brightness. Normal conducting L- and S-band photoinjectors are limited in repetition rate and D-C (photo)injectors are limited in field strength at the cathode. We propose a low frequency normal-conducting cavity, operating at 50 to 100 MHz CW, to provide beam bunches at a rate of one MegaHertz or more. The photoinjector uses a re-entrant cavity structure, requiring less than 100 kW CW, with a peak wall power density less than 10 W/cm2. The cavity will support a vacuum down to 10 picoTorr, with a load-lock mechanism for easy replacement of photocathodes. The photocathode can be embedded in a magnetic field to provide correlations useful for flat beam generation. Beam dynamics simulations indicate that normalized emittances on the order of 1 mm-mrad are possible with gap voltage of 750 kV, with fields up to 20 MV/m at the photocathode, for 1 nanocoulomb charge per bunch after acceleration and emittance compensation. Long-bunch operation (10's of picosecond) is made possible by the low cavity frequency, permitting low bunch current at the 750 kV gap voltage.
An international experiment to demonstrate muon ionization cooling is scheduled for beam at Rutherford Appleton Laboratory in 2007. The experiment comprises one cell of the Study II cooling channel*, along with upstream and downstream detectors to identify individual muons and measure their initial and final 6D phase-space parameters to a precision of 0.1%. Magnetic design of the beam line and cooling channel are complete and portions are under construction. The experiment will be described, including hardware designs, fabrication status, and running plans. Phase 1 of the experiment will prepare the beam line and provide detector systems, including time-of-flight, Cherenkov, scintillating-fiber trackers and the spectrometer solenoids, and an electromagnetic calorimeter. The Phase 2 system will add the cooling channel components, including liquid-hydrogen absorbers embedded in superconducting focus solenoids, 201-MHz normal-conducting RF cavities, and their surrounding coupling coil solenoids. The MICE Collaboration goal is to complete the experiment by 2010; progress toward this goal will be indicated. The supporting R&D program and its present results will also be described.
*S. Ozaki, R. Palmer, M. Zisman, and J. Gallardo (eds.), "Feasibility Study II of a Muon-based Neutrino Source," BNL-52623, 2001; http://www.cap.bnl.gov/mumu/studyii/final_draft/The-Report.pdf.
Uppsala University, Uppsala
KEK, Ibaraki
CERN, Geneva
Fermilab, Batavia, Illinois
DESY, Hamburg
SLAC, Menlo Park, California
In an effort to compare beam dynamics and create a ‘‘benchmark'' for Dispersion Free Steering (DFS) a comparison was made between different International Linear Collider (ILC) simulation programs while performing DFS. This study consisted of three parts. First, a simple betatron oscillation was tracked through each code. Secondly, a set of component misalignments and corrector settings generated from one program was read into the other to confirm similar emittance dilution. Thirdly, given the same set of component misalignments DFS was performed independently in each program and the resulting emittance dilution was compared. Performance was found to agree exceptionally well in all three studies.
LLNL, Livermore, California
A new cathode design has been proposed for the Flash X-Ray (FXR) induction linear accelerator with the goal of lowering the beam emittance. The present design uses a conventional Pierce geometry and applies a peak field of 134 kV/cm (no beam) to the velvet emission surface. Voltage/current measurements indicate that the velvet begins emitting near this peak field value and images of the cathode show a very non-uniform distribution of plasma light. The new design has a flat cathode/shroud profile that allows for a peak field stress of 230 kV/cm on the velvet. The emission area is reduced by about a factor of four to generate the same total current due to the greater field stress. The relatively fast acceleration of the beam, approximately 2.5 MeV in 10 cm, reduces space charge forces that tend to hollow the beam for a flat, non-Pierce geometry. The higher field stress achieved with the same rise time is expected to lead to an earlier and more uniform plasma formation over the velvet surface. Simulations of the proposed design are presented.
SLAC, Menlo Park, California
LBNL, Berkeley, California
INFN/LNF, Frascati (Roma)
INFN-Roma II, Roma
UCLA, Los Angeles, California
Jet Propulsion Laboratory, Pasadena, California
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
UCLA, Los Angeles, California
SLAC, Menlo Park, California
Euclid TechLabs, LLC, Solon, Ohio
USC, Los Angeles, California
LLNL, Livermore, California
Electron bunches with the unparalleled combination of high charge, low emittances, and short time duration, as first produced at the SLAC FFTB, are foreseen to be produced soon at the SABER facility. These types of bunches have enabled wakefield driven accelerating schemes of >10 GV/m. In the context of the Dielectric Wakefield Accelerators (DWA) such beams, having rms bunch length as short as 20 um, have been used to drive 100 μm and 200 μm ID hollow tubes above 20 GV/m surface fields. These FFTB tests enabled the measurement of a breakdown threshold in excess of 4 GV/m (2 GV/m accelerating field) in fused silica. With the construction and commissioning of the SABER facility at SLAC, new experiments are made possible to test further aspects of DWAs including materials, tube geometrical variations, direct measurements of the Cerenkov fields, and proof of acceleration in tubes >10 cm in length. The E169 collaboration will investigate breakdown thresholds and accelerating fields in new materials including CVD diamond. Here we describe the experimental plans, beam parameters, simulations, and progress to date as well as future prospects for machines based of DWA structures.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
USC, Los Angeles, California
In the recent plasma wakefield accelerator experiments at SLAC, the energy of the particles in the tail of the 42 GeV electron beam were doubled in less than one meter [1]. Simulations suggest that the acceleration length was limited by a new phenomenon – beam head erosion in self-ionized plasmas. In vacuum, a particle beam expands transversely in a distance given by beta*. In the blowout regime of a plasma wakefield [2], the majority of the beam is focused by the ion channel, while the beam head slowly spreads since it takes a finite time for the ion channel to form. It is observed that in self-ionized plasmas, the head spreading is exacerbated compared to that in pre-ionized plasmas, causing the ionization front to move backward (erode). A simple theoretical model is used to estimate the upper limit of the erosion rate for a bi-gaussian beam by assuming free expansion of the beam head before the ionization front. Comparison with simulations suggests that half this maximum value can serve as an estimate for the erosion rate. Critical parameters to the erosion rate are discussed.
[1] I. Blumenfeld et al., Nature 445, 741(2007)[2] J. B. Rosenzweig et al., Phys. Rev. A 44, R6189 (1991)
USC, Los Angeles, California
UCLA, Los Angeles, California
Simulation and analysis of the ion motion and multiple ionization in a plasma wakefield accelerator is presented for the parameters required of a future ILC afterburner. We show that although ion motion leads to substantial emittance growth for extreme parameters of future colliders in the sub-micron spot size regime, several factors that can mitigate the effect are explored. These include sunchrotron damping, plasma density gradient and hot plasma.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
USC, Los Angeles, California
Systematic measurements of energy gain as a function of plasma parameters in the SLAC electron beam-driven plasma wakefield acceleration (PWFA) experiments lead to very important understanding of the beam-plasma interaction. In particular, measurements as a function of the plasma length Lp show that the energy gain increases linearly with Lp in the 10 to 30 cm range. Based on this scaling, the plasma was subsequently lengthened to Lp=90cm, resulting in the first demonstration of the doubling of the energy of a fraction of the incoming 42GeV electrons*. The peak accelerating gradient is larger than 40GV/m and is sustained over meter-scale plasma lengths. These measurements also reveal that the optimum plasma density for acceleration is about 2.7·1017/cc, larger than the value predicted by the linear theory for the approximately 20 microns bunch length, confirming that the experiment is conducted in the non-linear regime of the PWFA. Detailed experimental results will be presented.
* "Energy doubling of 42 GeV electrons in a meter scale plasma wakefield accelerator", I. Blumenfeld et. al., Nature, 2006, accepted
BNL, Upton, Long Island, New York
USC, Los Angeles, California
STI, Washington
The presentation will cover experimental results on generation and measurement of the beams with theμbunches length from 1 to 50 microns at Brookhaven Accelerator Test Facility. Arbitrary number of microbunches is sliced out of 5 ps long beam using wire mesh and slits. The details of beam structure are characterized using CSR interferometer and 6 mm long plasma wakefield channel with the controllable plasma density.
SLAC, Menlo Park, California
The main linac of the International Linear Collider (ILC) accelerates short, high peak current bunches into the Beam Deliver System (BDS) on the way to the interaction point. In the BDS wakefields are excited by the resistance of the beam pipe walls and by beam pipe transitions that will tend to degrade the emittance of the beam bunches. In this report we calculate the effect on emittance of incoming jitter or drift, and of misalignments of the beam pipes with respect to the beam axis, both analytically and through multi-particle tracking. Finally, we discuss ways of ameliorating the wake effects in the BDS.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
USC, Los Angeles, California
Recent experiments at SLAC have shown that high gradient acceleration of electrons is achievable in meter scale plasmas. Results from these experiments show that the wakefield is sensitive to parameters in the electron beam which drives it. In the experiment the bunch length and beam waist location were varied systematically at constant charge. Here we investigate the correlation of peak beam current to the decelerating gradient. Limits on the transformer ratio will also be discussed. The results are compared to simulation.
SLAC, Menlo Park, California
Emittance growth is an important issue for plasma wakefield accelerators (PWFAs). Multiple Coulomb scattering (MCS) is one factor that contributes to this growth. Here, the MCS emittance growth of an electron beam traveling through a PWFA in the blow out regime is calculated. The calculation uses well established formulas for angular scatter in a neutral vapor and then extends the range of Coulomb interaction to include the effects of traveling through an ion column. Emittance growth is negligible for low Z materials; however, becomes important for high Z materials.
SLAC, Menlo Park, California
Photonic bandgap (PBG) fibers with hollow core defects have been suggested for use as laser driven accelerator structures. The modes of a periodic PBG fiber lie in a set of allowed bands. A fiber with a central vacuum defect can support so-called defect modes with frequencies in the bandgap and electromagnetic fields confined spatially near the central defect. A defect mode suitable for relativistic particle acceleration must have a longitudinal electric field in the central defect and a phase velocity near the speed of light (SOL). We explore the design of the defect geometry to support well-confined accelerating modes in such PBG fibers. The details of the surface boundary separating the defect from the surrounding matrix are found to be the critical ingredients for optimizing the accelerating mode properties. We give examples of improved accelerating modes in fiber geometries with modified defect surfaces.
SLAC, Menlo Park, California
Luminosity considerations for microscale accelerators intended for high-energy physics place a high premium on the bunch repetition rate and phase space density at the interaction point. The NLC Test Accelerator (NLCTA) at SLAC was built to address such beam dynamics issues for the Next Linear Collider and beyond. Because an S-Band RF gun has been installed together with a low-energy, high-resolving power spectrometer (LES), it is useful to explore alternatives to conventional scenarios with it. We consider possibilities that can be tested with minimal modification to this system e.g. cases that involve producing multiple bunches from the cathode in different formats such as a 2D planar matrix or 3D tensor beam made of smaller bunches or bunchlets that replace the usual, single higher charge bunches. Thus, we study configurations of interacting bunchlets nij or nijk coming from the cathode and passing through the emittance compensating solenoids that can be matched to the linac or focussed on the LES focal plane at 6 MeV. Parmela calculations have been done that show no significant space charge effects or emittance increases for pC bunchlet charges.
SLAC, Menlo Park, California
Stanford University, Stanford, Califormia
The NLC Test Accelerator (NLCTA) at SLAC was built to address various beam dynamics issues for the Next Linear Collider. An S-Band RF gun has been installed with diagnostics and a low energy spectrometer (LES) at 6 MeV together with a large-angle extraction line at 60 MeV. This is followed by a matching section, buncher and final focus for the laser acceleration experiment, E163. The laser-electron interaction area is followed by a broad range (2\%), high resolving power (104) spectrometer (HES) for electron bunch analysis. Emittance compensating solenoids and the LES are used to tune for best operating point and match to the linac. Optical symmetries in the design of the 25.5° extraction line provide 1:1 phase space transfer without use of sextupoles for a large, 6D phase space volume and range of input conditions. Spot sizes of a few microns at the IP (or HES object) allow tests of microscale structures as well as high resolving power at the image of the HES. Tolerances, tuning sensitivities and diagnostics are discussed together with the latest commissioning results and their comparison to design expectations.
KEK, Ibaraki
CERN, Geneva
CLASSE, Ithaca
The very small vertical beam emittance in the International Linear Collider (ILC) can be degraded by dispersion, xy coupling, transverse wakefields, and time-varying transverse fields introduced by elements with misalignments, strength errors, xy rotation errors, or yz rotation errors in the Ring to Main Linac (RTML) transfer line. We present a plan for emittance preservation in this beamline which uses local, quasi-local, and global correction schemes. Results of simulations of the emittance preservation algorithm are also presented and discussed.
High power RF testing has been performed on a novel axisymmetric radiofrequency electron gun at a frequency of 11.43 GHz using the magnicon facility at the Naval Research Laboratory. This gun utilizes coaxial coupling from the upstream end of unit and allows for axisymmetric tuning of both the cathode cell and the second cell. The features of the gun have been proven to operate at high gradients. The overall design of the gun will be discussed along with the results of the high power RF testing.
UMiss, University, Mississippi
BNL, Upton, Long Island, New York
Muon acceleration from 30 to 750 GeV in 72 orbits using two rings in the 1000m radius Tevatron tunnel is explored. The first ring ramps at 400 Hz and accelerates muons from 30 to 400 GeV in 28 orbits using 14 GV of 1.3 GHz superconducting RF. The ring duplicates the Fermilab 400 GeV main ring FODO lattice, which had a 61m cell length. Muon survival is 80%. The second ring accelerates muons from 400 to 750 GeV in 44 orbits using 8 GV of 1.3 GHz superconducting RF. The 30 T/m main ring quadrupoles are lengthened 87% to 3.3m. The four main ring dipoles in each half cell are replaced by three dipoles which ramp at 550 Hz from -1.8T to +1.8T interleaved with two 8T fixed superconducting dipoles. The ramping and superconducting dipoles oppose each other at 400 GeV and act in unison at 750 GeV. Muon survival is 92%. Two mm copper wire, 0.28mm grain oriented silicon steel laminations, and a low duty cycle mitigate eddy current losses. Low emittance muon bunches allow small aperatures and permit magnets to ramp with a few thousand volts. Little civil construction is required. The tunnel exists.
BNL, Upton, Long Island, New York
An electron cooler, based on an Energy Recovery Linac (ERL) is under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. This will be the first electron cooler operating at high energy with bunched beams. In order to achieve sufficient cooling of the ion beams the electron have to have a charge of 5 nC and a normalized emittance less than 4 mm mrad. This paper presents the progress in optimizing the injector and the emittance improvements from shaping the charge distribution in the bunch.
BNL, Upton, Long Island, New York
Emittance compensation is a well established technique* for minimizing the emittance of electron beam from a RF photo-cathode gun. Longitudinal slices of a bunch have a small emittance, but due to the longitudinal charge distribution of the bunch and time dependent RF fields they are not focused in the same way, so that the direction of their phase ellipses diverges in phase space and the projected emittance is much larger. Emittance compensation reverses the divergence. At the location where the slopes of the phase ellipses coincides the beam is accelerated, so that the space charge forces are reduced. A recipe for emittance compensation is given in reference**. For magnetized beams (where the angular momentum is non-zero) such emittance compensation is not sufficient because variations in the slice radius lead to variations in the angular speed and therefore to an increase of emittance in the rotating frame. We describe a method and tools for a compensation that includes the beam magnetization.
* L. Serafini, J. B. Rosenzweig, Phys. Rev E 55, 7565, (1997)
** X. Y. Chang, I. Ben-Zvi, J. Kewisch, Phys. Rev ST AB 9, 044201, (2006)
Fermilab, Batavia, Illinois
BNL, Upton, Long Island, New York
Muons, Inc, Batavia
UMiss, University, Mississippi
We propose a complete scheme for cooling a muon beam for a muon collider. We first outline the parameters required for a multi-TeV muon collider. The cooling scheme starts with the front end of the Study 2a proposed Neutrino Factory. This yields bunch trains of both muon signs. Emittance exchange cooling in upward climbing helical lattices then reduces the longitudinal emittance until it becomes possible to combine the trains into single bunches, one of each sign. Further cooling is now possible in emittance exchange cooling rings. Final cooling to the required parameters is achieved in 50 T solenoids that use high temperature superconductor. Preliminary simulations of each element will be presented.
IF-UFRGS, Porto Alegre
The goal of this work is to analyze the envelope dynamics of magnetically focused and high-intensity charged particle beams. As known, beams with mismatched envelopes decay into its equilibrium state with a simultaneous increasing of emittance. This emittance growth implies that, in the stationary regime, the transverse phase-space of the beam is characterized by a tenuous population of hot particles around a dense population of cold particles. To describe this emittance growth, it was used the test-particle approach for the development of a simplified self-consistent macroscopic model, whose self-consistency is a result of the inclusion of the emittance growth into the envelope equation. The model is then compared with full N-particle beam simulations and the agreement is shown to be quite reasonable. The model revealed to be useful to understand the physical aspects of the problem and is computationally faster when compared with full simulations.
TRIUMF, Vancouver
[1] D. Einfeld, "Status of the ALBA project", EPAC 06, Scotland, Edinburgh, June 2006.[2] D. Tronc and A. Setty, "Electrons RF auto-focusing and capture in bunchers", Linear Accelerator Conference 1988, Virginia.
GSI, Darmstadt
IAP, Frankfurt am Main
EUROTRANS (EUROpean Research Programme for the TRANSmutation of High Level Nuclear Waste in an Accelerator Driven System) is calling for an efficient high-current CW front-end accelerator system. A combination of RFQ, normal conducting CH- (Crossbar H-mode) and super-conducting CH-DTL which aims to work at 352MHz and accelerate a 30mA proton beam to 17MeV has been studied as a promising candidate. The preliminary conceptual study results are reported with respect to beam dynamics design.
DESY, Hamburg
The International Linear Collider (ILC) requires the preservation of an ultra-small vertical emittance from the Damping Ring to the Interaction Point (IP) where the nanometre-sized beams are made to collide. It is well-known that ground motion and component vibration will need to be compensated by fast intra-train feedback systems and slower semi-continuous trajectory corrections. This complex system can in general only be modelled using simulation. In this paper, we report the progress and status of a full-featured so-called start-to-end simulation based on the MERLIN package of the ILC Low Emittance Transport (LET): Bunch compression, acceleration in the superconducting Main Linac, Beam Delivery System and finally collision at the IP. Realistic modelling of the beam-beam is included by using the code GUINEAPIG. Results based on several ground motion and vibration models and configurations of trajectory control are presented.
DESY, Hamburg
The small energy-spread, weak wakefields and relatively weak focusing in the ILC superconducting Main Linac result in little or no filamentation beam mismatch errors: linear correlations such as dispersion or cross-plane coupling from transverse misalignment or rotation errors of the quadrupoles respectively do not decohere as the beam is transported (accelerated) along the linac. Using correction available in the Beam Delivery System, the increase in projected emittance due to this linear correlations can to a large degree be corrected. In this paper we present component tolerances based on the assumption of a global correction at the end of the Main Linac. Some discussion on the impact of ground motion is also discussed.
DESY, Hamburg
Uni HH, Hamburg
GSI, Darmstadt
Bologna University, Bologna
We present the upgrade of the MICROMAP beam dynamics simulation library to include a 2 1/2 D space charge modeling of a 3D bunch using local slices in z. We discuss the parallelization technique, the performances, several tests and comparison with existing well-established analytical/numerical results in order to validate the code. An application to the SIS100 synchrotron of the FAIR project at GSI is outlined.
Universita' degli Studi di Milano, Milano
INFN-Milano, Milano
INFN-Milano, Milano
Universita' degli Studi di Milano, Milano
KEK, Ibaraki
KEK, Ibaraki
KEK, Ibaraki
TIT, Yokohama
Utsunomiya University, Utsunomiya
For researches in high energy density physics and inertial confinement fusion by using heavy ion beams, high-current beam dynamics should be understood well. The heavy ion beam is longitudinally compressed by a head-to-tail velocity tilt applied from high-power induction voltage modules. In this study, emittance growth due to the longitudinal bunch compression is numerically investigated by using a particle-in-cell simulation. The code developed is dealt with three dimensional particle motions, and 2D transverse electric field is solved by Poisson equation coupled with 1D longitudinal electric field. We indicate the particle dynamics due to the non-linear longitudinal-transverse coupling effect around the stagnation point in the longitudinal compression.
JLAB, Newport News, Virginia
Jefferson Lab, Newport News, Virginia
PKU/IHIP, Beijing
We present work directed at examining the performance of various front end components of an ERL based light source. These include electron source, bunch compression, merger, and accelerating sections, with parameter space dictated by proposed facilities (at FSU and Beijing University). These facilities share enough common structural features to make the study applicable to both to a large extent. In this report we will discuss the 6D phase space evolution through the front end based on simulation, with reliable modeling of magnetic and superconducting RF fields. Discussion will be devoted to relative merits of alternative designs, robustness and operational scenarios.
USTC/NSRL, Hefei, Anhui
USTC, Hefei, Anhui
A method of injection analysis of small electron storage ring is introduced, and several medium emittance lattices are proposed. By analyzing the injection, working point of the lattice is selected at the vicinity of half integer resonance lines, and emittance is around 60nmrad, the linear and nonlinear properties can be satisfied for injection and store.
LIU Zu-Ping, Li Wei-Min. Progress of the NSRL Phase Two Project. In proceedings of the Second Asia Particle Accelerator Conference, Beijing, China, 2001, 235-238
CERN, Geneva
GSI, Darmstadt
Fermilab, Batavia, Illinois
CERN, Geneva
BNL, Upton, Long Island, New York
GSI, Darmstadt
KEK, Ibaraki
SLAC, Menlo Park, California
LBNL, Berkeley, California
LBNL, Berkeley, California
PSI, Villigen
UMAN, Manchester
Voss Scientific, Albuquerque, New Mexico
PPPL, Princeton, New Jersey
Voss Scientific, Albuquerque, New Mexico
The linear growth of the two-stream instability for a charged particle beam that is longitudinally compressing as it propagates through a background plasma (due to an applied velocity tilt) is examined. Detailed, 1D particle-in-cell simulations are carried out to examine the growth of a wave packet produced by a small amplitude density perturbation in the background plasma. Recent analytic and numerical work by Startsev and Davidson [1] predicted reduced linear growth rates, which are indeed observed in the simulations. Here, small-signal asymptotic gain factors are determined in a semi-analytic analysis and compared with the simulation results in the appropriate limits. Nonlinear effects in the PIC simulations, including wave breaking and particle-trapping, are found to limit the linear growth phase of the instability for both compressing and non-compressing beams.
[1] Phys. Plasmas 13, 62108 (2006)
LBNL, Berkeley, California
PPPL, Princeton, New Jersey
Voss Scientific, Albuquerque, New Mexico
Longitudinal bunching factors in excess of 70 of a 300-keV, 27-mA K+ ion beam have been demonstrated in the Neutralized Drift Compression Experiment in rough agreement with LSP particle-in-cell end-to-end simulations. These simulations include both the experimental diode voltage and induction bunching module voltage waveforms in order to specify the initial beam longitudinal phase space critical to longitudinal compression. To maximize simultaneous longitudinal and transverse compression, we designed a solenoidal focusing system that compensated for the impact of the applied velocity tilt on the transverse phase space of the beam. Here, pre-formed plasma provides beam neutralization in the last one meter drift region where the beam perveance becomes large. Integrated LSP simulations, that include detailed modeling of the diode, magnetic transport, induction bunching module, plasma neutralized transport, were critical to understanding the interplay between the various accelerator components. Here, we compare simulation results with the experiment and discuss the contributions to longitudinal and transverse emittance that limit compression.
ANL, Argonne, Illinois
The Advanced Photon Source (APS) has decided to implement a system using pulsed* crab cavities to produce short x-ray pulses using Zholents'** scheme. This paper describes beam dynamics issues related to implementation of this scheme in a single APS straight section. Modeling of the cavity is used to demonstrate that the deflection will be independent of transverse position in the cavity. Parameters and performance for a standard and lengthened APS straight section are shown. Finally, tolerances are discussed and obtained from tracking simulations.
* M. Borland et al., these proceedings.** A. Zholents et al., NIM A 425, 385 (1999).
ANL, Argonne, Illinois
In recent years, we have explored various upgrade options for the Advanced Photon Source (APS) storage ring that would provide the user community higher brightness. Increased brightness would be accomplished by reducing the emittance of the storage ring as well as increasing the stored beam current from 100 mA to 200 mA. Two upgrade lattices were developed that reduce the effective beam emittance to 1 nm from the present 2.7 nm. These lattices have reduced dynamic aperture compared to the present ring lattice, which may require a reduced emittance booster to minimize injection losses. This paper describes injection tracking simulations that explore how high the booster emittance can be and still have no losses at injection for the 1-nm ring upgrade lattices. An alternative booster lattice is presented with reduced emittance compared to the present booster lattice (65 nm). The proposed low-emittance booster lattice would add pole-face windings to the existing booster dipoles and hence would not require replacement of the existing booster magnets.
ANL, Argonne, Illinois
Northern Illinois University, DeKalb, Illinois
Transverse-to-longitudinal emittance exchange can be achieved through certain arrangements of dipole magnets and dipole mode rf cavity. Theory on such schemes has been developed in the past several years. In this paper we report our numerical simulations on the emittance exchange using particle tracking codes. Photoelectron beams with energy less than 20 MeV are used, as our purpose of simulations is to study the feasibility of performing such emittance exchange at existing facilities of beam energy at this level. Parametric studies of the dipole magnets and cavity strengths, as well as initial beam parameters, are presented.
ANL, Argonne, Illinois
We present a triple-bend lattice design that uses the current APS tunnel. The new lattice has a 1 nm-rad effective emittance at 7 GeV. A forty-period symmetric optics is presented. For the benefit of some X-ray user experiments, an optics with four special straight sections of one-third the beam size of normal sections was investigated as well. The associated nonlinear optical difficulties are addressed and simulation results are presented.
ANL, Argonne, Illinois
We present a lattice design based on the theoretical-minimum-emittance (TME) cell for the International Linear Collider (ILC0 6.6-km 5-GeV damping ring. Several areas are discussed: momentum compaction, lattice layout, injection and extraction, circumference adjusters, phase adjuster, and dynamic aperture calculation with multipole errors.
ANL, Argonne, Illinois
The Touschek effect is a major concern for lepton storage rings of low emittance (i.e., high bunch density) and low or moderate beam energy, such as third-generation synchrotron light sources. Piwinski's formula, which includes beam shape variation along the beamline and which is suitable for any beam energy, has been incorporated into a program that interoperates with elegant for use in lifetime calculations. The difference between using Piwinski's method and other simplified methods for the APS is shown in this paper. Furthermore, because of the generality of this formula, we also applied it to transport lines to predict beam loss rates and beam loss locations for the first time. An example related to a possible energy recovery linac upgrade of the APS (APS-ERL) is also given in this paper.
ANL, Argonne, Illinois
Fermilab, Batavia, Illinois
A direct space-charge force model has been implemented in the tracking code elegant. The user can simulate transverse space-charge effects by inserting space-charge elements in the beamline at any desired position. Application to the International Linear Collider damping ring is presented in this paper. We simulated beam under equilibrium conditions, as well as the entire damping cycle from injection to extraction. Results show that beam halo is generated due to space charge effects. This would be a significant concern for the ILC damping ring and a detailed follow-up study is needed.
ANL, Argonne, Illinois
Large scale beam dynamics simulations are important to support the design and operations of an accelerator. From the beginning, the beam dynamics code TRACK was developed to make it useful in the three stages of a hadron (proton and heavy-ion) linac project, namely the design, commissioning and operation of the machine. In order to combine the unique features of TRACK with large scale and fast parallel computing we have recently developed a parallel version of the code*. We have successfully benchmarked the parallel TRACK on different platforms: BG/L and Jazz at ANL, Iceberg at ARSC, Lemieux at PSC and Seaborg at NERSC. We have performed large scale RFQ and end-to-end simulations of the FNAL proton driver where particles were simulated. The actual parallel version has the potential of simulating particles on 10 racks with 20,480 processors of BG/L at ANL, which will be available soon. After a brief description of the parallel TRACK, we'll present results from highlight applications.
* "Parallelization of a Beam Dynamics Code and First large Scale RFQ Simulations", J. Xu, B. Mustapha, V. N. Aseev and P. N. Ostroumov, accepted for publication in PRST-AB.
Pavilion Technologies, Inc, Austin, Texas
SLAC, Menlo Park, California
High brightness electron beam sources such as rf photo-injectors as proposed for SASE FELs must consistently produce the desired beam quality. We report the results of a study in which a combined neural network (NN) and first-principles (FP) model is used to model the transverse phase space of the beam as a function of quadrupole magnet current, while beam charge, solenoid field, accelerator gradient, and linac voltage and phase are kept constant. The parametric transport matrix between the exit of the linac section and the spectrometer screen constitutes the FP component of the combined model. The NN block provides the parameters of the transport matrix as functions of quad current. Using real data from SLAC Gun Test Facility, we will highlight the significance of the constrained training of the NN block and show that the phase space of the beam is accurately modelled by the combined NN and FP model, while variations of beam matrix parameters with the quad current are correctly captured. We plan to extend the combined model in the future to capture the effects of variations in beam charge, solenoid field, and accelerator voltage and phase.
Illinois Institute of Technology, Chicago, Illinois
G4beamline is a single-particle simulation program optimized for the design and evaluation of beam lines. It is based on the Geant4 toolkit, and can implement accurate and realistic simulations of particle transport in both EM fields and in matter. This makes it particularly well suited for studies of muon collider and neutrino factory design concepts. G4beamline includes a rich repertoire of beamline elements and is intended to be used directly without C++ programming by accelerator physicists. The program has been enhanced to handle a larger class of beamline and detector systems, and to run on Linux, Windows, and Macintosh platforms.
Fermilab, Batavia, Illinois
JINR, Dubna, Moscow Region
Presently the Fermilab Booster can accomodate about half the maximum proton beam intensity which the Linac can deliver. One of the limitations is related to large vertical tuneshift produced by space-charge forces at injection energy. In the present report we study the nonlinear beam dynamics in the presence of space charge and magnet imperfections and analyze the possibility of space charge compensation with electron lenses.
BNL, Upton, Long Island, New York
Fermilab, Batavia, Illinois
For muons with preferable for ionization cooling momentum <300MeV/c the longitudinal motion is naturally undamped. In order to provide the longitudinal damping a correlation between muon momentum and transverse position - described in terms of the dispersion function - should be introduced. In the present report we consider the possibility of dispersion generation in a periodic sequence of alternating solenoids (FOFO channel) by choosing the tune in the second passband (i.e. above half-integer per cell) and tilting the solenoids in adjacent cells in the opposite direction. Analytical estimates as well as simulation results for equilibrium emittances and cooling rates are presented.
Fermilab, Batavia, Illinois
CHEF is both a framework and an interactive application emphasizing accelerator optics calculations. The framework supports, using a common infrastructure, multiple domains of applications: e.g. nonlinear analysis, perturbation theory, and tracking. Its underlying philosophy is to provide infrastructure with minimum hidden implicit assumptions, general enough to facilitate both routine and specialized computational tasks and to minimize duplication of necessary, complex bookkeeping tasks. CHEF was already described in recent conferences. In this paper we present a status report on the most recent developments, including issues related to its application to high energy linacs.
The University of Texas at Austin, Austin, Texas
Until recently, values of the amplitude functions through the Interaction Regions of the Tevatron collider detectors have been inferred either by reconstructing event locations through the detector and mapping out the luminous region to deduce the beam emittance and amplitude function or by performing differential closed orbit measurements while varying steering magnets and producing detailed models of the synchrotron's optical properties which reproduce the observed orbital deviations. Both of these methods rely on often lengthy off-line analyses and sometimes many hours of experimental data to obtain a meaningful result. The new Tevatron Beam Position Monitor system, commissioned in 2005, has allowed unprecedented detail of turn-by-turn motion to be measured at the 20-micron level and for thousands of beam revolutions. Such measurements performed with a freely oscillating proton beam, excited by a kicker magnet, allow for the direct measurement of the amplitude function which is model independent. A simple measurement procedure, data analysis method, and typical results for the Tevatron experimental regions are presented.
Fermilab, Batavia, Illinois
Estimates indicate that the electron cloud effect could be a limiting factor for Main Injector intensity upgrades, with or without a the presence of a new 8 GeV superconducting 8GeV Linac injector. The effect may turn out to be an issue of operational relevance for other parts of the Fermilab accelerator complex as well. To improve our understanding of the situation, two sections of specially made vacuum test pipe outfitted for electron cloud detection with ANL provided Retarding Field Analyzers (RFAs), were installed in the Tevatron and the Main Injector. In this report we present some measurements, compare them with simulations and discuss future plans for studies.
LLNL, Livermore, California
The Kapchinskij-Vladimirskij equations describe the evolution of the beam envelopes in a periodic system of quadrupole focusing cells and are widely used to help predict the performance of such systems. Being nonlinear, they are usually solved by numerical integration. There have been numerous papers describing approximate solutions with varying degrees of accuracy. We have found an exact solution for a matched beam in the limit of zero space charge. The model is FODO with a full occupancy, piecewise-constant focusing function. Our explicit result for the envelope a(z) is exact for phase advances up to 180 degrees and all other values except multiples of 180 degrees. The peak envelope size is minimized at 90 degrees. The higher stable bands require larger, very accurate, field strengths while producing significantly larger envelope excursions.
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
IUCF, Bloomington, Indiana
Two partial helical dipole snakes were found to be able to overcome all imperfection and intrinsic spin resonances provided that the vertical betatron tunes were maintained in the spin tune gap near the integer 9. Recent vertical betatron tune scan showed that the two weak resonances at the beginning of the acceleration cycle may be the cause of polarization loss. This result has been confirmed by the vertical polarization profile measurement, and spin tracking simulations. Possible cure of the remaining beam polarization is discussed.
MIT/PSFC, Cambridge, Massachusetts
A warm-fluid theory of a thermal equilibrium for a rotating charged particle beam in a periodic solenoidal focusing magnetic field is presented. The warm-fluid equilibrium equations are solved in the paraxial approximation. It is shown that the flow velocity for the thermal equilibrium corresponds to periodic rigid rotation and radial pulsation. The equation of state for the thermal equilibrium is adiabatic. The beam envelope equation and self-consistent Poisson's equation are derived. The numerical algorithm for solving self-consistent Poisson's equation is discussed. Density profiles are calculated numerically for high-intensity beams. Temperature effects in such beams are investigated, and the validity of the warm-fluid theory is discussed. Examples of electron and ion beams are presented for space-charge-dominated beam and high energy density physics (HEDP) research.
UMD, College Park, Maryland
This is a numerical study of the effects of skew quadrupoles on the beam used in University of Maryland Electron Ring (UMER). As this beam is space-charge dominated, we expect new phenomena to be present compared to the emittance-dominated case. In our studies we find that skew quadrupoles can severely affect the halo of the beam and cause emittance growth, even in the first turn of the beam. For our simulations we used the WARP particle-in-cell code and we compared the results with the experimental study of skew quadrupole effects (to be reported separately).
CLASSE, Ithaca
One of the main concerns in the design of a high energy Energy Recovery Linac x-ray source is the preservation of beam emittance. Discussed is one possible source of emittance dilution due to transverse electromagnetic fields in the accelerating cavities of the linac caused by the power coupler geometry. This has already been found to be a significant effect in Cornell's ERL injector cavities if only one coupler per cavity is chosen. Here we present results of simulations for Cornell's main ERL linac with three possible coupler configurations and compare them with regards to total normalized emittance growth after one complete pass through the linac. We explain why the sign of the phase between the transverse kick and the accelerating force alternates each cavity, which leads to a cancellation of the emittance growth to acceptable values. We also investigate the effect of cavity detuning on the coupler-kick effect.
INFN/LNF, Frascati (Roma)
UCLA, Los Angeles, California
Rome University La Sapienza, Roma
SLAC, Menlo Park, California
The low energy ring (LER) in PEP-II has a design emittance of 0.5 nm-rad in the vertical, compared to nearly 0.1 nm-rad for the HER ring. This was thought to come from the "vertical step" of about 1 m in the interaction straight, where the LER beam after horizontal separation gets bend vertical so it sits on top of the HER in the rest of the ring. Since the program MAD does not easily reveal the location of the major emittance contribution, a program was written to calculate the coupled "curly H" parameter of mode 2 (mainly vertical) along z. Weighting it with the magnet bending revealed that the weak long bends inside the "vertical step" did less than 20% of the emittance growth. More than 80% comes from the ends of the adjacent arcs with strong bends. This is caused by the coupling cancellation of the solenoid starting already there with the skew quadrupoles SK5 and 6. By introducing additional skews in the straight instead of SK5 and 6 the emittance could be reduced by a factor of ten in simulations, but with very strong skews. Reasonable strong magnets might generate a workable compromise, since a factor of two in emittance promises 50% more luminosity in beam-beam simulations.
SLAC, Menlo Park, California
LBNL, Berkeley, California
* J. Qiang et al, Phys. Rev. ST Accel. Beams 9,044204 (2006).
A classical electron/positron accelerating structure is a disk loaded cylindrical waveguide. The accelerator structure here has azimuth symmetry. The proposed structure contains a disk-loaded cylindrical waveguide where there is a periodical change of rf-field vs. azimuth. The modulation deforms the rf-field in such a manner that the accelerated particles undergo transverse focusing forces. The new class of accelerator structures covers the initial part of e+/e- linacs where a bunch is not rigid and additional transverse focusing fields are necessary. We discuss a bunch formation with a high transverse aspect ratio in the proposed structure and particularly in the photoinjector part of a linac.
Jefferson Lab, Newport News, Virginia
Particle beam modeling in accelerators has been the focus of much effort (at great expense) since the 1950s. Several generations of tools have resulted from this process, each leveraging both the understanding provided by predecessors and the availability of increasingly powerful computer hardware. Nonetheless, the process remains on-going, in part due to innovations in accelerator design, construction, and operation that result in machines not easily described by existing tools. We discuss a novel response to this issue, which was encountered when Jefferson Lab began operation of its energy-recovering linacs. As such machines are not conveniently described using legacy software, a machine model was been built using Microsoft Excel. This interactive simulation can query data from the accelerator, use it to compute machine parameters, analyze difference orbit data, and evaluate beam properties. It can also derive new accelerator tunings and rapidly evaluate the impact of changes in machine configuration. As it is spreadsheet-based, it can be easily user-modified in response to changing requirements. Examples for the JLab IR Upgrade FEL are presented.
The SNS ring injection dump beam line has been suffering high beam losses since its commissioning. In order to understand the mechanisms of the beam losses, we have built a 3D simulation model consisting of three injection chicane dipoles and one injection dump septum. The magnetic field distributions and the 3D particle trajectories in the model are obtained. The study has clearly shown two design problems causing beam losses in the injection dump beam line. This paper reports our simulation model, particle trajectory calculations, beam losses due to small vertical aperture of the injection dump septum and inadequate focusing down stream. The remedy of the beam losses is also discussed.
Fermilab, Batavia, Illinois
An experiment is being constructed at Fermilab's A0 Photoinjector to exchange longitudinal and transverse beam emittances. The exchange is preformed by an optics channel consisting of two dogleg bend sections with a transverse deflecting mode cavity between them. In this paper we discuss the construction of the TM110 Mode Cavity. The cavity, based on a superconducting design will be constructed of copper. In addition, the cavity will be cooled with liquid nitrogen to fit within power and mode spacing requirements. The TM110 cavity operating requirements are presented as will the detail of the design, construction, tuning, and commissioning of the TM110 cavity.
PPPL, Princeton, New Jersey
The transverse compression and dynamics of intense charged particle beams, propagating through a periodic quadrupole lattice, play an important role in many accelerator physics applications. Typically, the compression can be achieved by means of increasing the focusing strength of the lattice along the beam propagation direction. However, beam propagation through the lattice transition region inevitably leads to a certain level of beam mismatch and halo formation. In this paper we present a detailed analysis of these phenomena using particle-in-cell (PIC) numerical simulations performed with the WARP code. A new definition of beam halo is proposed in this work that provides the opportunity to carry out a quantitative analysis of halo production by a beam mismatch.
DULY Research Inc., Rancho Palos Verdes, California
One of the most important targets for building modern particle accelerators is to increase the beam brightness. The purposes of building a dc/rf gun are to seek high bunch charge and low beam transverse emittance, two key parameters for enhancing brightness of accelerators. We present simulation results of the beam emittance changes in a dc/rf gun under different gun voltages. SUPERFISH and PARMELA were used to simulate the beam dynamics in the gun. These simulations indicate that a small beam transverse emittance (< 0.5 mm.mrad) can be obtained when the voltage on the dc gap is lower than 200 kV and the bunch charge is 200 pc, and increments of dc gap voltages will greatly improve the emittances.
BNL, Upton, Long Island, New York
JINR, Dubna, Moscow Region
The low-energy electron cooling system is based on an electron beam immersed in a longitudinal magnetic field of a solenoid. The coupling of the horizontal and vertical motion allows representation of the friction force as a sum of the transverse and longitudinal components. The analytic treatment proceeds by allowing several approximations, for example, uniform transverse density distribution of electron beam and Maxwellian distribution in the velocity space. The high-energy electron cooling system for RHIC is unique compared to standard coolers. It requires bunched electron beam. Electron bunches are produced by an Energy Recovery Linac (ERL), and cooling is planned without a longitudinal magnetic field. To address the unique features of the RHIC cooler, a generalized 3-D treatment of the cooling force was introduced in the BETACOOL code which allows to calculate the friction force from an arbitrary six-dimensional distribution of the electrons. Results based on this treatment are compared to typical approximations. Simulations for the RHIC cooler based on a realistic electron distribution from the ERL are presented.
Fermilab, Batavia, Illinois
ANL, Argonne, Illinois
Rutgers University, The State University of New Jersey, Piscataway, New Jersey
The A0 photoinjector is being reconfigured to test the principal of transverse to longitudinal emittance exchange as proposed by Emma et. al., Kim and Sessler, and others. The ability to perform such an exchange could have major advantages to FELs by reducing the transverse emittance. Several schemes to carry out the exchange are possible and will be reported separately. At the Fermilab A0 Photoinjector we are constructing a beamline to demonstrate this transverse to longitudinal emittance exchange. This beamline will consist of a dogleg, and a TM110 5 cell copper cavity followed by another dogleg. The beamline is designed to reuse the bunch compressor dipoles of the photoinjector, along with some existing diagnostics. Beamline layout and optics discussed along with inital data. Future possibilites of performing a similar experiment at the proposed NML facility at Fermilab are also discussed.
BNL, Upton, Long Island, New York
Non-magnetized electron cooling of RHIC requires an electron beam energy of 54.3 MeV, electron charge per bunch of 5 nC, normalized rms beam emittance of 4 mm-mrad, and rms energy spread of 3·10-4 *. In this paper we describe a lattice of a two-pass SCRF energy recovery linac (ERL) and results of a PARMELA simulation that provides electron beam parameters satisfying RHIC electron cooling requirements.
* A. Fedotov, Electron Cooling Studies for RHIC II http://www.bnl.gov/cad/ecooling/docs/PDF/Electron_Cooling.pdf
BNL, Upton, Long Island, New York
A super-conducting RF R&D Energy recovery linac (ERL) is under construction at Brookhaven National Laboratory (BNL). This ERL will be used as a test facility to study issues relevant to high-current, high-brightness beams. One of the goals is to demonstrate an electron beam with high charge per bunch (~ 5 nC) and extremely low normalized emittance (~ 5 mm-mrad) at an energy of 20 MeV. In contrast with operational high-brightness linear electron accelerators, all presently operating ERLs have an order of magnitude larger emittances for the same charge per bunch. One reason for this emittance growth is that the merger system mixes transverse and longitudinal degrees of freedom, and consequently violates emittance compensation conditions. A merger system based on zigzag scheme* resolves this problem. In this paper we discuss performance of the present design of the BNL R&D ERL injector with a zigzag merger.
* V. N. Litvinenko, R. Hajima, and D. Kayran, Nucl. Instr. and Meth. A 557 (2006) 165.
BNL, Upton, Long Island, New York
ORNL, Oak Ridge, Tennessee
ORNL/SNS is managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract DE-AC05-00OR22725
LBNL, Berkeley, California
LLNL, Livermore, California
To provide a compact high-brightness heavy-ion beam source for Heavy Ion Fusion, we have performed experiments to study a proposed merging beamlet approach for the injector. We used an RF plasma source to produce the initial beamlets. An extraction current density of 100 mA/cm2 was achieved, and the thermal temperature of the ions was below 1 eV. An array of converging beamlets was used to produce a beam with the envelope radius, convergence, and ellipticity matched to an electrostatic quadrupole channel. Experimental results were in good quantitative agreement with simulation and have demonstrated the feasibility of this concept. The size of a driver-scale injector system using this approach will be several times smaller than one designed using traditional single large-aperture beams. The success of this experiment has possible significant economical and technical impacts on the architecture of HIF drivers.
IF-UFRGS, Porto Alegre
This paper analyzes the combined envelope-centroid dynamics of magnetically focused high-intensity charged beams surrounded by conducting walls. Similarly to the case were conducting walls are absent, we show that the envelope and centroid dynamics decouples from each other. Mismatched envelopes still decay into equilibrium with simultaneous emittance growth, but the centroid keeps oscillating with no appreciable energy loss. Some estimates are performed to analytically obtain some characteristics of halo formation seen in the full simulations.
IF-UFRGS, Porto Alegre
We analyze the dynamics of inhomogeneous, magnetically focused high-intensity beams of charged particles. While for homogeneous beams the whole system oscillates with a single frequency, any inhomogeneity leads to propagating transverse density waves which eventually result in a singular density build up, causing wave breaking and jet formation. The theory presented in this paper allows to analytically calculate the time at which the wave breaking takes place. It also gives a good estimate of the time necessary for the beam to relax into the final stationary state consisting of a cold core surrounded by a halo of highly energetic particles.
USP/LAL, Sao Paulo
In this work we describe the determination of the beam emittance for the 100-keV injector of the IFUSP racetrack microtron. We measured the beam spot diameter at a fluorescent screen located 40 cm after a 3-mm diameter collimator (placed at the entrance to the first chopper cavity). A solenoid lens located upstream to the collimator was used to produce a beam waist at the fluorescent screen position. We used the collimator and the beam waist sizes to calculate the emittance for 80 and 90 keV beams. Results showed no dependence with energy, indicating that the collimator is limiting the beam emittance at 2.32(5) ??mm?mrad.
INFN/LNF, Frascati (Roma)
Rome University La Sapienza, Roma
UCLA, Los Angeles, California
This work has been partially supported by the EU in the sixth framework program, Contract no. 011935 EUROFEL-DS1.
CERN, Geneva
POSTECH, Pohang, Kyungbuk
KEK, Ibaraki
TUB, Beijing
* Dao Xiang and Wen-Hui Huang, Nucl. Instr. and Meth. in Phys. Res. B, 254 (2007) 165.** Dao Xiang and Wen-Hui Huang, Nucl. Instr. and Meth. in Phys. Res. A, 570 (2007) 357.*** Dao Xiang and Wen-Hui Huang, Phys. Rev. ST-AB, 10 (2007) 012801.
DESY, Hamburg
FZD, Dresden
CERN, Geneva
EPFL, Lausanne
Fermilab, Batavia, Illinois
CERN, Geneva
The LHC Schottky observation system is based on traveling wave type high sensitivity pickup structures operating at 4.8 GHz. The choice of the structure and operating frequency is driven by the demanding LHC impedance requirements, where very low impedance is required below 2 GHz, and good sensitivity at the selected band at 4.8 GHz. A sophisticated filtering and triple down-mixing signal processing chain has been designed and implemented in order to achieve the specified 100 dB instantaneous dynamic range without range switching. Detailed design aspects for the complete systems and test results without beam are presented and discussed.
CERN, Geneva
GSI, Darmstadt
Longitudinal coupled bunch instabilities in the CERN PS represent a major limitation to the high brightness beam delivered for the LHC. To identify possible impedance sources for these instabilities, machine development studies have been carried out. The growth rates of coupled bunch modes have been measured, and modes have been identified using mountain range data. Growth rate estimations from coupled bunch mode theory are compared to these results. It is shown that the longitudinal impedance of the broad resonance curve of the main 10 MHz RF system can be identified as the most probable source. Possible methods to improve the beam stability are analyzed together with the performance of a damping system.
CERN, Geneva
NSRRC, Hsinchu
UMAN, Manchester
ANL, Argonne, Illinois
The horizontal bursting instability was first observed in a single bunch in the APS in 1998, soon after operation began. Above the instability threshold, the bursting is characterized by exponentially growing bunch centroid oscillations that saturate, then decay, repeating quasi-periodically. More recently, bursting was also observed with multiple bunches in both the horizontal and vertical planes, showing that this is not purely a single-bunch phenomenon. On the other hand, the multibunch instability threshold is strongly dependent on bunch spacing, and the dependence is markedly different for the two transverse planes. Depending on the bunch spacing, the bunch-to-bunch oscillations are sometimes coupled, sometimes not. In this paper, we discuss the threshold in terms of the chromaticity required to stabilize the beam. We present instability imaging data using a streak camera that shows the bunch-to-bunch oscillation phase, and turn-by-turn beam position histories that give the bursting time dependence for different bunch spacings. Finally, we discuss the machine impedance and measured tune shift with current.
ANL, Argonne, Illinois
Northern Illinois University, DeKalb, Illinois
Fermilab, Batavia, Illinois
The University of Texas at Austin, Austin, Texas
Fermilab, Batavia, Illinois
Two Ionization Profile Monitors (IPMs) were installed in the Tevatron in 2006. The detectors are capable of resolving single bunches turn-by-turn, using a combination of gas injection to boost the ionization signal and very fast and sensitive electronics to detect it. This paper presents recent improvements to the system hardware and its use for beam monitoring. In particular, the correction of beam size oscillations observed at injection is discussed.
In the classical chromaticity measurement technique, chromaticity is measured by measuring the change in betatron tune as the the RF frequency is varied. This paper will describe a way of measuring chromaticity: we will phase modulate the RF with a known sine wave and then phase demodulate the betatron frequency . The result is a line in Fourier space which corresponds to the frequency of our sine wave modulation. The peak of this sine wave is proportional to chromaticity. For this technique to work, a tune tracker PLL system is required because it supplies the betatron carrier frequency. This method has been tested in both the SPS and Tevatron and we will show the results here.
Tech-X, Boulder, Colorado
In the classical head-tail chromaticity measurement technique, a single large kick is applied transversely to the beam. The resulting phase difference between the head and the tail is measured and the chromaticity extracted. In the continuous head-tail kicking technique, a very small transverse kick is applied to the beam and the asymptotic phase difference between the head and the tail is found to be a function of chromaticity. The advantage of this method is that since the tune tracker PLL already supplies the small transverse kicks, no extra modulation is required.
Fermilab, Batavia, Illinois
BNL, Upton, Long Island, New York
Fermilab, Batavia, Illinois
Long-range beam-beam interactions can cause significant degrade of beam quality and lifetime in high energy ring colliders. At RHIC, a series of experiments were carried out to study these effects. In this paper, we report on numerical simulation of the long-range beam-beam interactions at RHIC using a parallel strong-strong particle-in-cell code, BeamBeam3D. The simulation includes nonlinearities from both the beam-beam interactions and the arc sextupoles. We observed significant emittance growth for beam separation below 4 σs under nominal tunes. A scan study in tune space shows strong emittance growth around 7th order resonance. Including the tune modulation due to chromaticity and synchrotron motion shows larger emittance growth than the case without the tune modulation.
LBNL, Berkeley, California
The Fermilab main injector (MI) is being considered for an upgrade as part of the high intensity neutrino source (HINS) effort. This upgrade will involve a significant increasing of the bunch intensity relative to its present value. Such an increase will place the MI in a regime in which electron-cloud effects are expected to become important. We have used the electrostatic particle-in-cell code WARP, recently augmented with new modeling capabilities and simulation techniques, to study the dynamics of beam-electron cloud interaction. This study involves a systematic assesment of beam instabilities due to the presence of electron clouds.
Northern Illinois University, DeKalb, Illinois
We undertake a study of particle dynamics in a model fixed-field alternating-gradient (FFAG) synchrotron in which space-charge plays a central role. The space-charge force corresponds to a Gaussian charge distribution in both transverse dimensions. The betatron-tune is linearly ramped through resonance. This ramping alone can cause particles to enter orbits that have chaotic motion.. We found that space-charge can lead to spreading of the available tunes which can either increase or decrease the effects of resonance. By applying recently developed techniques to measure complexity in the orbital dynamics, we also determine whether chaoticity can arise in particle trajectories and subsequently influence resonance crossings. Furthermore, we can see that the chaoticity changes drastically in the area around a resonance crossing.
Northern Illinois University, DeKalb, Illinois
ANL, Argonne, Illinois
Royal Holloway, University of London, Surrey
LLNL, Livermore, California
SLAC, Menlo Park, California
KEK, Ibaraki
UCB, Berkeley, California
LBNL, Berkeley, California
UCL, London
Cornell University, Department of Physics, Ithaca, New York
Fermilab, Batavia, Illinois
University of Cambridge, Cambridge
DESY, Hamburg
SLAC, Menlo Park, California
UCLA, Los Angeles, California
USC, Los Angeles, California
Recent electron beam driven plasma wakefield accelerator experiments carried out at SLAC showed trapping of plasma electrons. These trapped electrons appeared on an energy spectrometer with smaller transverse size than the beam driving the wake. A connection is made between transverse size and emittance; due to the spectrometer?s resolution, this connection allows for placing an upper limit on the trapped electron emittance. The upper limit for the lowest normalized emittance measured in the experiment is 1 mm∙mrad.
SLAC, Menlo Park, California
Ion induced beam instability is one critical issue for the electron damping ring of the International Linear Collider (ILC) due to its ultra small emittance of 2pm. Bunch train filling pattern is proposed to mitigate the instability and bunch-by-bunch feedback is applied to suppress it. Multi-bunch train fill pattern is introduced in the electron beam to reduce the number of trapped ions. Our study shows that the ion effects can be significantly mitigated by using multiple gaps. However, the beam can still suffer from the beam-ion instability driven by the accumulated ions that cannot escape from the beam during the gaps. The effects of beam fill pattern, emittance, vacuum and various damping mechanism are studied using self-consistent program, which includes the optics of the ring.
SLAC, Menlo Park, California
The effects of the round edge beam hole on the frequency and wake field are studied using variational method, which allows for rounded iris disk hole without any approximation in shape treatment. The frequency and wake field of accelerating mode and dipole mode are studied for different edge radius cases, including the flat edge shape that is often used to approximately represent the actual structure geometry. The edge hole shape has weak effect on the frequency, but much effect on the wake field. Our study shows that the amounts of wake fields are not precise enough with the assumption of the flat edge beam hole instead of round edge.
SLAC, Menlo Park, California
In this paper, we study the single bunch transverse beam dynamics in the presence of random displacements of resistive wall segments and focusing elements. Analytical formulas are obtained for long-range resistive wall wake, together with numerical results for short-range resistive wall wake. Tolerances on this random displacement are studied regarding to emittance growth and phase slippage in an undulator. The results are applied to the LCLS project and some other proposed accelerators.
MIT, Middleton, Massachusetts
The beam-beam interaction has a significant impact on the beam emittance growth and the luminosity lifetime in RHIC. A simulation study of the emittance growth was performed using the Lifetrac code. The operational conditions of RHIC 2006 100GeV polarized proton run were used in the study. In this paper, the result of this study is presented and compared to the experimental measurements.
BNL, Upton, Long Island, New York
The beam lifetime in most medium-energy synchrotron radiation sources is limited by the Touschek effect, which describes the momentum transfer from the transverse into the longitudinal direction due to binary collisions between electrons. While an analytical formula exists to calculate the resulting lifetime, the actual momentum acceptance necessary to perform this calculation can only be determined by tracking. This is especially the case in the presence of small vertical apertures at insertion devices. In this case, nonlinear betatron coupling leads to beam losses at these vertical aperture restrictions. In addition, a realistic model of the storage ring is necessary for calculation of the equilibrium beam sizes (particularly in the vertical direction) which are important for a self-consistent lifetime calculation.
BNL, Upton, Long Island, New York
The ERL Prototype project is currently under development at the Brookhaven National Laboratory. The ERL is expected to demonstrate energy recovery of high-intensity beams with a current of up to a few hundred milliamps, while preserving the emittance of bunches with a charge of a few nanocoulombs produced by a high-current SRF gun. To successfully accomplish this task the machine will include beam diagnostics that will be used for accurate characterization of the three dimensional beam phase space at the injection and recirculation energies, transverse and longitudinal beam matching, orbit alignment, beam current measurement, and machine protection. This paper outlines requirements on the ERL diagnostics and describes its setup and modes of operation.