J-PARC, KEK & JAEA, Ibaraki-ken
The Japan Proton Accelerator Research Complex (J-PARC) is a multi-purpose facility making full use of secondary particles like neutrons, muons, Kaons, and neutrinos produced by the MW-class proton accelerators. The J-PARC accelerator scheme inserts a 3-GeV Rapid-Cycling Synchrotron (RCS) in between a 400-MeV injector linac (at present 181 MeV) and a several-ten GeV Main Ring (MR). The RCS has already demonstrated extraction of one pulse of 2.6·1013 protons at 3 GeV, which corresponds to 315 kW if operated at 25 Hz, with a beam loss less than one percent, and a beam power of 210 kW for a period of 70 sec in September. The beam circulation and RF capture in MR have been done in May. Also, the neutron production target was beam-commissioned, providing high-resolution, high-efficiency neutrons. The RCS users’ run and the 30-GeV MR acceleration are planned in December. Rationale for the J-PARC accelerator scheme will be resumed on the basis of the results and difficulties encountered during the development, the construction and the commissioning. The upgrade plan, and, hopefully, some experimental results will be presented.
RIKEN Nishina Center, Wako
The RIKEN RI Beam Factory (RIBF) is pushing the limits of energy for heavy ion cyclotrons. The first experiment of the RIBF has successfully finished with the discovery of new isotopes 125Pd and 126Pd* in June 2007 with a 345-MeV/nucleon uranium beam. However, the total transmission efficiency was limited to be less than 1%. In addition, a carry-over of oil was found in the refrigerator of the Superconducting Ring Cyclotron (SRC), which was the main accelerator of the RIBF. To solve these problems, we have improved beam monitors, upgraded the oil remover system of the compressor of the liquid helium cryogenic plant at SRC and made a series of acceleration tests. As a result, 0.3 pnA of a 345-MeV/nucleon uranium beam was stably delivered to RIBF users in November 2008 and a 345-MeV/nucleon 48Ca beam with the intensity of 170 pnA was obtained in December 2008. In the PAC09 presentation, we will summarize our operating experience with the SRC and developments of RIBF accelerators in addition to most up-to-date performance of the RIBF accelerator complex.
*T. Ohnishi et al., J. Phys. Soc. Jpn. 77 (2008) 083201
BNL, Upton, Long Island, New York
Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka
Department of Energy Sciences, Tokyo Institute of Technology, Yokohama
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Work supported by RIKEN.
We have studied a laser ion source in Brookhaven National Laboratory since 2006. In November 2008, we had first beam through an RFQ and the measured current reached about 50 mA with carbon beam. The RFQ and ion source were originally commissioned in Japan and moved to BNL in 2006. We will report various acceleration test results at the conference.
Tech-X, Boulder, Colorado
KEK, Ibaraki
BNL, Upton, Long Island, New York
Funding: Supported in part by the DOE Office of Science, Office of Nuclear Physics under grant No. DE-FG02-06ER84508.
Non-scaling FFAGs are sensitive to a slew of resonances during the acceleration ramp. An important consideration - because it affects the amount of rf power required - will be the speed at which resonances must be crossed. We present simulations of possible non-scaling FFAGs, focusing especially on the effects of space charge, using newly developed capabilities in the code PTC*.
* E. Forest, Y. Nogiwa, F. Schmidt, "The FPP and PTC Libraries", ICAP'2006.
TUB, Beijing
PSI, Villigen
CIAE, Beijing
In high intensity cyclotrons with small turn separation, both the space charge effects of single bunch and the interaction of radially neighbouring bunches play important roles. A PIC-based three-dimensional parallel code, OPAL-CYCL, is newly developed under OPAL framework which self-consistently covers these two collective effects. In this paper we also present the simulation results from the compact cyclotron CYCIAE-100 in the context of the ongoing upgrade program of BRIF at CIAE, with the goal of 100 MeV, 200 μA CW proton beam on target.
KEK, Ibaraki
KEK/JAEA, Ibaraki-Ken
J-PARC is a unique accelerator, because magnetic alloy (MA) loaded cavities are employed for the first time in the rf systems of high intensity proton synchrotrons. High field gradients of more than 20 kV/m are achieved covering the frequency range from 0.9 MHz to 3.4 MHz. The peak voltage of 45 kV per cavity is obtained by driving with two 600 kW tetrodes in push-pull. The first high intensity beam acceleration was successfully initiated at J-PARC RCS. Although RCS beam commissioning started with 10 rf systems, instead of 11 as designed, RCS succeeded in the acceleration of an intense proton beam, which is equivalent to 300 kW when operated at 25 Hz. The longitudinal painting based on the simulation with superimposed second harmonics and with phase and momentum manipulations was the key of success. In December 2008, the J-PARC MR beam is scheduled for its first acceleration up to 30 GeV, and the Material and Life Science facilities start the user operations. During the development stage of the MA cavities, some serious problems such as electrical breakdown on core surfaces occurred. The problems were solved in a short term, and all rf systems were completed on schedule.
Fermilab, Batavia
Muons, Inc, Batavia
CERN, Geneva
Funding: supported in part by USDOE STTR Grant DE-FG02-08ER86350
The great advantage of the helical ionization cooling channel (HCC) is its compact structure that enables the fast cooling of muon beam 6-dimensional phase space. This compact aspect requires a high average RF gradient, with few places that do not have cavities. Also, the muon beam is diffuse and requires an RF system with large transverse and longitudinal acceptance. A traveling wave system can address these requirements. First, the number of RF power coupling ports can be significantly reduced compared with our previous pillbox concept. Secondly, by adding a nose on the cell iris, the presence of thin metal foils traversed by the muons can possibly be avoided. We show simulations of the cooling performance of a traveling wave RF system in a HCC, including cavity geometries with inter-cell RF power couplers needed for power propagation.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
GUAS, Kanagawa
J-PARC RCS accelerates a high intensity beam using 11 sets of Magnetic Alloy loaded cavities. It supplies the proton beam to the MLF (Material Life Science Facility) for the neutron and muon experiments. For very high resolution muon experiments, a short proton beam bunch of few ten ns is necessary. To reduce the bunch width to several ten ns, a bunch rotation scheme before extraction will be useful. For the bunch width of few ten ns, a much higher RF voltage is also required. Based on a new magnetic alloy core technology, a design of a new RF cavity to increase the maximum RF voltage by a factor of two will be described in this paper.
KEK, Ibaraki
High-gradient RF breakdown studies have been in progress at Nextef (New X-band Test Facility at KEK) since 2006. To study the characteristics of different materials on high-field RF breakdown, we have performed high-gradient experiments by using narrow waveguides that has a field of around 140 MV/m at 50 MW power. Breakdown rates of stainless-steel and copper cases were measured and the results are described in this paper.
DESY, Hamburg
ACCEL, Bergisch Gladbach
W.C. Heraeus GmbH, Materials Technology Dept., Hanau
A test program of 1.3 GHz TESLA shape 9-cell large grain (LG) resonators for the European XFEL project was started at DESY. The main aim is to find out whether or not the choice of LG material could be an option for the fabrication of approx. 800 XFEL resonators. Several aspects are under investigation and will be compared with the conventional polycrystalline material option. One of the aspects is the material issue: could the required amount of LG niobium be produced at industry in a cost effective and reliable manner? The second issue is the fabrication of cavities: could the series production of resonators be done on the level of required accuracy and costs? The third one is the performance issue: what is the appropriate treatment for reproducibly achieving the specified XFEL accelerating gradients? Development of the LG disc production was done within the framework of the R&D program of DESY and W. C. HERAEUS. Eleven resonators are produced at the company ACCEL. Up to now three resonators are RF-tested vertically. The He-vessel was welded onto one of the resonators which passed the horizontal RF-test. The data and perspectives of the LG cavity application are discussed.
Fermilab, Batavia
MIPT, Dolgoprudniy, Moscow Region
Long 11-cell, beta=0.81 L-band structure is considered as an initial stage of the high-energy part of the Project-X in order to accommodate to a standard CM4 cryomodule. The cavity shape is optimized for maximal energy gain providing the same time field flatness along the structure not worse than for ILC beta=1 cavity, and the same ratio of surface magnetic field to electric field. The results of spectrum analysis for monopole and dipole HOMs is presented as well as the HOM damper design.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
EMMA is a prototype non-scaling FFAG that requires a demanding RF system. Production for the final RF system is due for completion in Spring 09 and testing of the combined hardware has taken place. This paper describes the high power verification tests of the IOT transmitter, waveguide distribution, RF cavity and LLRF control system.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
EMMA (Electron Model for Many Applications) is a non-scaling Fixed Field Accelerating Gradient (NS-FFAG) accelerator presently in the process of being built at Daresbury Laboratory as a proof of principle demonstrator for proton/carbon therapy application. Its aim is to take an injected beam from ALICE (Accelerators and Lasers in Combined Experiments) at 10MeV and accelerate it to 20MeV, so that the characteristics of NS-FFAGs can be studied. The beam is to be accelerated by 19 identical 1.3GHz RF cavities, which each need to provide the same accelerating voltage to the beam. The initial design stage of the RF system design has been completed, utilising three commercial suppliers of the major RF sub-system components.
BNL, Upton, Long Island, New York
Cultural noise generated within or in the proximity of a light source facility aiming to achieve stability levels of just tens of nanometers in the electron beam and extremely small photon beams in special experimental lines could be a limiting factor towards achieving the performance goals. While operating systems within the facility are more readily identifiable as sources of vibration and cause of instabilities and they tend to be of deterministic nature so appropriate action can be taken to minimize their impact, moving-type loads such as traffic in the general vicinity or within the bounds of the accelerator facility are more of a stochastic nature and require a different approach in assessing its impact on the synchrotron facility. In this study the effect of such loads which poses both stochastic elements and a complex spectrum on the stability performance goals of the NSLS II synchrotron and its vibration-sensitive experimental lines is addressed prior to the construction of the facility. This is achieved through the synergy of a comprehensive numerical model and an array of recorded field data.
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
INFN-Pisa, Pisa
UNIPI, Pisa
CNR/IPP, Pisa
INFN-Cagliari, Monserrato (Cagliari)
The PLASMONX project foresees the installation at LNF of a 0.2 PW (6 J, 30 fs pulse) Ti:Sa laser system FLAME (Frascati Laser for Acceleration and Multidisciplinary Experiments) to operate in close connection with the existent SPARC electron photo-injector, allowing for advanced laser/e-beam interaction experiments. Among the foreseen scientific activities, a Thomson scattering experiment between the SPARC electron bunch and the high power laser will be performed and a new dedicated beamline is foreseen for such experiments. The beam lines transporting the beam to the interaction chamber with the laser have been designed, and the IP region geometry has been fixed. The electron final focusing system, featuring a quadrupole triplet and large radius solenoid magnet (ensuring an e-beam waist of {10}-15 microns) as well as the whole interaction chamber layout have been defined. The optical transfer line issues: transport up to the interaction, tight focusing, diagnostics, fine positioning, have been solved within the final design. The building hosting the laser has been completed; delivering and installation of the laser,as beam lines elements are now being completed.
CERN, Geneva
The PS2 is proposed as a replacement for the ageing PS and will provide proton beams with kinetic energies up to 50 GeV. It must also deliver Pb54+ ions, for which the revolution frequency swing will be more than a factor of two. The favoured rf scenario considers a 40 MHz accelerating system and is motivated by the possibility of chopping at up to 40 MHz in the SPL, the proposed proton injector. Using the same principal rf system for ions implies pushing for an unprecedented tuning range and the introduction of a new rf system in LEIR, the existing ion source. We present a solution to the disparate requirements of protons and ions based on a 40 MHz rf system with switchable tuning ranges to cover the large frequency swing required.
KAERI, Daejon
BNL, Upton, Long Island, New York
Funding: This work is supported by Ministry of Education, Science and Technology of the Korean government.
The proton engineering frontier project (PEFP) is designing the rapid cycling synchrotron (RCS) whose main purpose is the spallation neutron source. The PEFP 100-MeV linac will be the injector to the RCS. The output energy and beam power are 1 GeV and 60 kW at the initial stage. We studied the H- charge exchange injection with transverse and momentum painting schemes. In order to enhance the machine versatility, we studied the slow extraction options for the nuclear physics and medical research in addition to the single turn extraction for the spallation neutron source. This paper summarizes the present status of the physics design of the RCS.
FZJ, Jülich
BINP SB RAS, Novosibirsk
The design, construction and installation of a 2 MeV electron cooling system for COSY-Jülich is proposed to further boost the luminosity even with strong heating effects of high-density internal targets. In addition the 2 MeV electron cooler for COSY is intended to test some new features of the high energy electron cooler for HESR at FAIR in Darmstadt. The design of the 2 MeV electron cooler will be accomplished in cooperation with the Budker Institute of Nuclear Physics in Novosibirsk, Russia. A new developed prototype of the high voltage section, consisting of a gas turbine, magnetic coils and high voltage generator with electronics was successfully tested . Special emphasis is given to a voltage stability better than 10-4. First experiments with three combined high voltage sections, arranged in a SF6 pressurized gas tank are reported.
Fermilab, Batavia
MSU, East Lansing, Michigan
TRIUMF, Vancouver
PAC, Batavia, Illinois
UCR, Riverside, California
The quest for higher beam power and duty factor and precisely controlled beams at reasonable cost has generated world-wide interest in Fixed-field Alternating Gradient accelerators (FFAGs). A new concept in non-scaling FFAGs to stabilize the betatron tune is under development. The emphasis to date has been on electron and proton accelerators, yet many facilities utilize H- front ends. This concept naturally extends to H- FFAGs and under conditions of rapid acceleration, the FFAG functions essentially as a recirculating linac with a common-aperture arc. As such it may be suitable for replacement of aging H- linac sections. For a slow acceleration cycle, an H- FFAG machine can exploit H- techniques to control extraction and intensity, and represents an innovation in proton therapy accelerators. Prototype RF and magnet component design have been initiated. For ten-turn acceleration, the rf cavities in a 10-100 MeV FFAG cannot be re-phased on the revolution time scale, and local adjustment of the pathlength is the proposed approach. For slow acceleration, broad-band, low-frequency rf can be applied. The basic optics and components for such FFAGs are presented.
Bilbao, Faculty of Science and Technology, Bilbao
ESS Bilbao, Bilbao
Elytt Energy, Madrid
Funding: ESS-Bilbao Consortium
A baseline design for the proton linear accelerator as proposed by the European Spallation Source-Bilbao bid to host the installation (ESS-B) is here described. The new machine concept incorporates advances which have been registered within high power accelerators during the last decade. The design of such a new accelerator layout heavily relies upon low-beta superconducting spoke resonators which are already under development.
UCLA, Los Angeles, California
Instituto Superior Tecnico, Lisbon
Funding: Fundacao Calouste Gulbenkian and Fundacao para a Ciencia e Tecnologia under grants SFRH/BD/35749/2007.
The possibility of using a CO2 laser (10 micron wavelength) to drive a plasma density compression and achieve effective ion acceleration in gaseous targets (density>~ 1019cm-3) is explored. A parameter scan is performed with a set of particle in cell simulations in OSIRIS*, both in 2D and 3D, for various laser intensities, linear/circular polarization pulses, and plasma densities. Results show that, to generate the shock compression, plasma density must be increased above the critical value to account for the relativistic motion of the electrons. Under these conditions, 2-5MeV ions are observed with moderate intensity (a0=3) laser pulses. Finally, configurations to generate a shock structure are suggested, that will more efficiently accelerate the particles. This scenario is also of particular relevance to fast-ignition, inertial confinement fusion, and implications to those regimes can be obtained from numerical simulations by using the appropriate density normalization.
*R. A. Fonseca et al, LNCS 2329, III-342, Springer-Verlag, (2002)
LLNL, Livermore, California
TomoTherapy, Madison
CPAC, Madison
Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
We are developing a compact proton accelerator for cancer treatment by using the dielectric high-gradient insulator wall technology. The goal is to fit the compact dielectric wall proton therapy machine inside a conventional treatment room. To make the proton dielectric wall accelerator (DWA) compact requires a compact proton source capable of delivering protons in a sub-ns bunch. We are testing all the essential DWA components, including the compact proton source, on the First Accelerator System Test (FAST), which is designed to be taken apart and rebuilt many times to increase system performance by using improved components. The proton source being investigated currently is a surface flashover source. Five induction cells with HGI in the acceleration gaps are used to provide the 300-keV, 20-ns injector voltage for the proton injector. The physics design and the configuration of the injector and FAST will be presented.
Fermilab, Batavia
DESY, Hamburg
INFN/LASA, Segrate (MI)
CEA, Gif-sur-Yvette
Albert Einstein, Leibniz Universität, Hannover
With a view to the series production of one hundred, 12 m long XFEL 1.3 GHz cryomodules and their transportation from the assembly site at CEA Saclay (F) to the installation site at DESY Hamburg (D) a test transportation of a FLASH cryomodule has been performed, in the condition foreseen for the mass transportation. The present study examines the stresses induced on the module and verify the damping capabilities of the transport frame in order to minimize risk of damage to the most critical components. During the transportation, acceleration and vibration have been monitored as well as coupler antenna contacts and vacuum performances. This paper describes the analysis performed and compares those results to the data of a similar transportation study at Fermilab for the CM1 cryomodule.
Fermilab, Batavia
INFN/LASA, Segrate (MI)
Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
In an exchange of technology agreement, Deutsches Elektron-Synchrotron (DESY) Laboratory in Hamburg Germany has provided a 1.3 GHz cryomodule “kit” to Fermilab. The cryomodule components (qualified dressed cavities, cold mass parts, vacuum vessel, etc.) sent from Germany in pieces were assembled at Fermilab’s Cryomodule Assembly Facility (CAF). The cavity string was assembled at CAF-MP9 Class 10 cleanroom and then transported to CAF-ICB cold mass assembly area via a flatbed air ride truck. Finite Element Analysis (FEA) studies were implemented to define location of instrumentation for initial coldmass transport, providing modal frequencies and shapes. Subsequently, the fully assembled cryomodule CM1 was transported to the SRF Accelerator Test Facility at New Muon Lab (NML). Internal geophones (velocity sensors) were attached during the coldmass assembly for transport (warm) and operational (cold) measurements. A description of the isolation system that maintained alignment during transport and protected fragile components is provided. Shock and vibration measurement results of each transport and modal analysis are discussed.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
In an exchange of technology agreement, Fermilab has built and delivered a 3.9 GHz (3rd harmonic) cryomodule to Deutsches Elektron-Synchrotron (DESY) Laboratory to be installed in the TTF/FLASH beamline. Transport to Hamburg, Germany was completed via a combination of flatbed air ride truck and commercial aircraft, while minimizing transition or handling points. Initially, destructive testing of fragile components, transport and corresponding alignment stability studies were performed in order to assess the risk associated with transatlantic travel of a fully assembled cryomodule. Data logged tri-axial acceleration results of the transport with a comparison to the transport study predicted values are presented.
KEK, Ibaraki
The J-PARC accelerator comprises a 400 MeV linac, a 3-GeV Rapid Cycling Synchrotron (RCS) and a Main Ring (MR). In the linac, an H- ion beam was successfully accelerated to 181 MeV, the design target for the first step in Phase I, on January 24, 2007. Subsequently, full beam energy of 3 GeV was achieved in the RCS on October 31, 2007. The first beam commissioning of the MR was carried out in May and June 2008. Injection, circulation with rf capture and extraction to the injection beam dump were successfully performed. Some other basic tunings such as COD correction and chromaticity correction were also done well. In the MR, there are two extraction sections. One is for the Hadron Experimental Facility for which slow extraction will be mainly used and the other for neutrino experiment, which requires fast beam extraction. After confirming the basic performance of beam injection and beam circulation with rf capture, we have installed all devices for these two extraction sections and have progressed fine-tuning of ramp-up patterns of power supplies. Beam acceleration will start from December 2008. The first result of beam acceleration and extraction will be reported.
ORNL, Oak Ridge, Tennessee
University of Tennessee, Knoxville, Tennessee
MIT Lincoln Laboratory, Boston MA
Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
Investigations of the rf properties of certain twisted waveguide structures show that they support favorable accelerating fields. This makes them potential candidates for accelerating cavities. Using the particle tracking code, ORBIT, We examine the beam - rf interaction in the twisted cavity structures to understand their beam transport and acceleration properties. The results will show the distinctive properties of these new structures for particle transport and acceleration, which have not been previously analyzed.
TEMF, TU Darmstadt, Darmstadt
DESY, Hamburg
The rf and wakefield transverse kicks resulting from the asymmetry of input and HOM couplers in the third harmonic module for the XFEL are investigated. The fundamental mode is computed using eigenvalue analysis. The short range wakefields in a string of cavities are simulated with the PBCI code. Using the simulation data, the transverse kick factors associated with the presence of cavity couplers are evaluated.
* P. Pierini, "Third Harmonic Superconducting Cavity Prototypes for the XFEL", LINAC08.
** T. Khabiboulline, "New HOM Coupler Design For 3.9 Ghz Superconducting Cavities At FNAL", PAC07.
TRIUMF, Vancouver
LPSC, Grenoble
Most ion sources at ISOL (isotope separation on-line) facilities can produce only singly charged ions but efficient post acceleration requires high charge states. For light ions this can be achieved by stripping after a first moderate acceleration but with heavy ions this is no longer possible and charge state breeding is necessary. The breeder should be able to work at a high efficiency for the required charge state and especially for short-lived radioactive isotopes the process should be fast. For the ISAC facility at TRIUMF an ECRIS charge breeder (14 GHz PHOENIX from Pantechnik) has been chosen as it is well adapted to the continuous mode operation of the accelerator and for radioactive ions there is practically no limit for the beam intensity. After off-line optimization on a test bench the source has been moved on-line to the ISAC facility. Mass separated beams of radioactive ions from the on-line ion sources can be directed into the source. During a first test in fall 2008 a beam of 80Rb14+ was successfully created from 80Rb1+ and accelerated by the ISAC post accelerator. A summary of the results from the test bench and from the on-line commissioning will be presented.
CERN, Geneva
SLAC, Menlo Park, California
Uppsala University, Uppsala
A fundamental element of the CLIC concept is two-beam acceleration, where rf power is extracted from a high-current and low-energy beam in order to accelerate the low-current main beam to high energy. The power extraction occurs in special X-band Power Extraction and Transfer Structures (PETS). The structures are large aperture, high-group velocity and overmoded periodic structures. Following the substantial changes of the CLIC baseline parameters in 2006, the PETS design has been thoroughly updated along with the fabrication methods and corresponding rf components. Two PETS prototypes have been fabricated and high power tested. Test results and future plans are presented.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
EMMA, the Electron Model with Many Applications, was originally conceived as a model of a GeV-scale muon accelerator. The non-scaling (NS) properties of resonance crossing, small apertures, parabolic ToF and serpentine acceleration are novel, unproven accelerator physics and require "proof of principle". EMMA has metamorphosed from a simple "demonstration" objective to a sophisticated instrument for accelerator physics investigation with operational demands far in excess of the muon application that lead to technological challenges in magnet design, rf optimisation, injection and extraction, and beam diagnostics. Machine components procured in 2008 will be installed February-May 2009 leading to full system tests June-August and commissioning with electrons beginning September 2009.
JAEA/J-PARC, Tokai-mura
KEK, Ibaraki
KEK/JAEA, Ibaraki-Ken
The J-PARC Rapid Cycling Synchrotron (RCS) uses broadband magnetic alloy loaded cavities to create the acceleration voltages needed for rapid cycling at 25 Hz rate. Besides the desired second harmonic of the acceleration frequency, which is employed in the painting process of RCS injection, also unwanted harmonics can be found at the acceleration gaps of the cavities. Here, the effect of the vector sums of undesired harmonics during the acceleration process is estimated.
University of Tennessee, Knoxville, Tennessee
ORNL RAD, Oak Ridge, Tennessee
ORNL, Oak Ridge, Tennessee
RF properties of twisted waveguide structures were investigated to show that slow-wave accelerating fields can be excited and used for acceleration of particle at various velocities lately. To build a practical accelerating cavity structure using the twisted waveguide, more development work was needed: cavity structure tuning, end wall effect of the structures, incorporating beam pipes and input power coupler, and HOM damping, etc. In this paper, the practical aspects of the designs to make more complete accelerating structures are discussed with the results of computer simulations.
OXFORDphysics, Oxford, Oxon
Imperial College of Science and Technology, Department of Physics, London
UMAN, Manchester
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Brunel University, Middlesex
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
JAI, Oxford
Cockcroft Institute, Lancaster University, Lancaster
Manchester University, Manchester
Gray Cancer Institute, Northwood, Middlesex
Funding: EP/E032869/1
AMELA (Particle Accelerator for MEdicaL Applications) is a newly developed fixed field accelerator, which has capability for rapid beam acceleration, which is interesting for practical applications such as charged particle therapy. PAMELA aims to design a particle therapy facility using Non-Scaling FFAG technology, with a target beam repetition rate of 1kHz, which is far beyond that of conventional synchrotron. To realize the repetition rate, the key component is rf acceleration system. The combination of a high field gradient and a high duty factor is a significant challenge. In this paper, options for the system and the status of their development are presented.
SAMEER, Mumbai
Shunt impedance of an accelerating structure is an important parameter. It gives an idea of the power coupled to the beam. A 6 MeV to 15 MeV ‘S’ band standing wave side coupled linac structure is developed in SAMEER*. The measurement of the shunt impedance of the cavity is done using bead pull method. The shunt impedance is calculated after plotting the electric field profile. The calculation is done using a C code which first calculates the area of the plot and then uses appropriate variables to give the final value of the shunt impedance. The automation of the bead pull setup is planned and then the integration of calculation and automated setup. This paper describes the method used in the code and outlines the results of the measurement.
*R.Krishnan et.al. submitted in this conference.
SLAC, Menlo Park, California
Funding: Work supported by the DOE under contract DE-AC02-76SF00515.
The Multi-TeV colliders should have the capability to accelerate low emittance beam with high rf efficiency, X-band normal conducting high gradient accelerating structure is one of the promising candidate. However, the long range transverse wake field which can cause beam emittance dilution is one of the critical issues. We examined effectiveness of dipole mode damping in three kinds of X-band, π-mode standing wave structures at 11.424GHz with no detuning considered. They represent three damping schemes: damping with cylindrical iris slot, damping with choke cavity and damping with waveguide coupler. We try to reduce external Q factor below 20 in the first two dipole bands, which usually have very high (RT/Q)T. The effect of damping on the acceleration mode is also discussed.
RIKEN/SPring-8, Hyogo
The compact XFEL facility under construction in the SPring-8 campus aims at generation of SASE based XFEL at the wavelength of ~0.1 nm in 2010. Toward the smooth completion of the beam commissioning and achieving the reliable SASE XFEL operation, it is critically important to suppress the dark current upstream of the accelerator as much as possible. We thus investigated a removal scheme of the spatially diverged and energy deviated electrons forming the dark current by using sextupole magnets, which are installed over the C-band accelerating structures. The beam simulation showed that the combination of the distributed sextupole magnets with a small chicane, which locates in the adequate middle of the C-band accelerating structures, could efficiently remove the dark current emitted from the C-band acceleration structures. Here, we present the simulation results and the dark current suppression scheme designed for the compact XFEL facility at SPring-8.
UW-Madison/SRC, Madison, Wisconsin
SLAC, Menlo Park, California
The microbunching gain of a free-electron laser (FEL) driver is affected by the beam spreader that distributes bunches to the FEL beam lines. For the Wisconsin FEL (WiFEL), analytic formulas and tracking simulations indicate that a beam spreader design with a low value of R56 has little effect upon the gain.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
USC, Los Angeles, California
Funding: Work supported by the DOE under contract DE-AC02-76SF00515.
Plasma Wake-Field Acceleration (PWFA) has demonstrated acceleration gradients above 50 GeV/m. Simulations have shown drive/witness bunch configurations that yield small energy spreads in the accelerated witness bunch and high energy transfer efficiency from the drive bunch to the witness bunch, ranging from 30% for a Gaussian drive bunch to 95% for shaped longitudinal profile. These results open the opportunity for a linear collider that could be compact, efficient and more cost effective that the present microwave technologies. A concept of a PWFA-based Linear Collider (PWFA-LC) has been developed and is described in this paper. The scheme of the drive beam generation and distribution, requirements on the plasma cells, and optimization of the interaction region parameters are described in detail. The research and development steps, necessary for further development of the concept, are also outlined.
Fermilab, Batavia
Muons, Inc, Batavia
Northern Illinois University, DeKalb, Illinois
Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282 and by FRA under DOE Contract DE-AC02-07CH11359
MANX is a six-dimensional muon ionization cooling demonstration experiment based on the concept of a helical cooling channel in which a beam of muons loses energy in a continuous helium or hydrogen absorber while passing through a special superconducting magnet called a helical solenoid. The goals of the experiment include tests of the theory of the helical cooling channel and the helical solenoid implementation of it, verification of the simulation programs, and a demonstration of effective six-dimensional cooling of a muon beam. We report the status of the experiment and in particular, the proposal to have MANX follow MICE at the Rutherford-Appleton Laboratory (RAL) as an extension of the MICE experimental program. We describe the economies of such an approach which allow the MICE beam line and much of the MICE apparatus and expertise to be reused.
Imperial College of Science and Technology, Department of Physics, London
BNL, Upton, Long Island, New York
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
Non-scaling FFAG rings have been proposed as a solution for muon acceleration in the Neutrino Factory. In order to achieve small orbit excursion and small time of flight variation, lattices with a very compact cell structure and short straight sections are required. The resulting geometry dictates very difficult constraints on injection/extraction systems. The feasibility of injection/extraction is discussed and various implementations focusing on minimization of kicker/septum strength are presented.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
ODU, Norfolk, Virginia
Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86351
We have previously considered the application of fast pulsing quadrupoles to increase the focusing of muon beams as they gain energy in the linac region of a recirculating linear accelerator (RLA) in order to allow more passes. In this work we consider the use of pulsed magnets, both quads and dipoles, to reduce the number of beam lines needed for the return arcs of the RLA. We investigate the required relationships between the linac parameters (length and energy gain) and the momentum acceptance of the return arcs and consider the optimum strategy for accelerating both muon charge signs.
Fermilab, Batavia
Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
The Fermilab Main Injector is moving toward providing 400 kW of 120 GeV proton beams using slip stacking injection of eleven Booster batches. Loss of 5% of the beam at or near injection energy results in 1.5 kW of beam loss. A collimation system has been implemented to localize this loss with the design emphasis on beam not captured in the accelerating rf buckets. More than 90% of these losses are captured in the collimation region. We will report on the construction, commissioning and operation of this collimation system. Commissioning studies and loss measurement tools will be discussed. Residual radiation monitoring of the Main Injector machine components since 2004 will be used to demonstrate the effectiveness and limitations of these efforts.
Sheffield University, Sheffield
The MICE Experiment requires a beam of low energy muons to demonstrate muon cooling. This beam is derived parasitically from the ISIS accelerator. A novel target mechanism has been developed that inserts a small titanium target into the proton beam on demand. The target remains outside the beam envelope during acceleration and then overtakes the shrinking beam envelope to enter the proton beam during the last 2 ms before beam extraction. The technical specifications for the target mechanism are demanding, requiring large accelerations and precise and reproducible location of the target each cycle. The mechanism operates in a high radiation environment, and the moving parts are compatible with the stringent requirements of the accelerator’s vacuum system. This paper will describe the design of the MICE target and how it is able to achieve its required acceleration whilst still meeting all of the necessary requirements for operation within the ISIS vacuum. The first operational linear electromagnetic drive was installed onto ISIS in January 2008 and has since been operated for over one hundred thousand actuations.
ANL, Argonne
Euclid TechLabs, LLC, Solon, Ohio
Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
The Argonne Wakefield Accelerator Facility is dedicated to the study of advanced accelerator concepts based on electron beam driven wakefield acceleration and RF power generation. The facility employs an L-band photocathode RF gun to generate high charge short electron bunches, which are used to drive wakefields in dielectric loaded structures as well as in metallic structures (iris loaded, photonic band gap, etc). Accelerating gradients as high as 100 MV/m have been reached in dielectric loaded structures, and RF pulses of up to 44 MW have been generated at 7.8 GHz. In order to reach higher accelerating gradients, and also be able to generate higher RF power levels, a photocathode with higher quantum efficiency is needed. Therefore, a new RF gun with a Cesium Telluride photocathode will replace the electron gun that has been used to generate the drive bunches. In addition to this, a new L-band klystron will be added to the facility, increasing the beam energy from 15 MeV to 23 MeV, and thus increasing the total power in the drive beam to a few GW. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level.
Euclid TechLabs, LLC, Solon, Ohio
LETI, Saint-Petersburg
Fermilab, Batavia
Funding: Work supported by the US Department of Energy.
Materials possessing large variations in the permittivity as a function of the electric field exhibit a rich variety of phenomena for electromagnetic wave propagation such as frequency multiplication, wave steepening and shock formation, solitary waves, and mode mixing. New low loss nonlinear microwave ferroelectric materials present interesting and potentially useful applications for both advanced and conventional particle accelerators. Accelerating structures (either wakefield-based or driven by an external rf source) loaded with a nonlinear dielectric may exhibit significant field enhancements. Nonlinear transmission lines can be used to generate short, high intensity rf pulses to drive fast rf kickers. In this paper we will explore the large signal permittivity of these new materials and applications of nonlinear dielectric devices to high gradient acceleration, rf sources, and beam manipulation. We describe planned measurements using a planar nonlinear transmission line to study the electric field dependence of the permittivity of these materials. Diagnostics include appearance of harmonics with a cw drive signal and sharpening of a pulse waveform as it propagates.
IAP/RAS, Nizhny Novgorod
A new two-beam accelerating structure based on periodic chain of rectangular shape multi-mode cavities was suggested recently*. The structure is aimed to increase threshold breakdown surface field and thus to provide a high gradient. This threshold increase is to be brought about by designing cavities of the structure to operate simultaneously in several harmonically-related TMn,n,0 modes, thereby reducing the effective exposure time of the cavity surface to the peak fields. The more number of the operating modes is the more reduction of the exposure time. Unfortunately, a big amount of modes leads to limitation for cavity length and practical limitation of filling factor. In order to avoid this, it is suggested to operate with several TMn,n,l modes with non-zero longitudinal indices. These modes are able to provide the long interaction of a moving bunch with RF fields along the cavity. Such regime requires for the longitudinal index l to be strictly proportional the mode frequency. A cylindrical shape cavity design is also considered.
*S.V. Kuzikov, S.Yu. Kazakov, M.E. Plotkin, J.L. Hirshfield, High-Gradient Multi-Mode Two-Beam Accelerating Structure, Proc. of EPAC’08 Conf., Genoa, June 23-27, 2008, WEPP133.
IAP/RAS, Nizhny Novgorod
Yale University, Physics Department, New Haven, CT
Omega-P, Inc., New Haven, Connecticut
Funding: Sponsored in part by US Department of Energy, Office of High Energy Physics.
A multi-mode cavity design for a two-beam accelerator aimed to achieve an accelerating gradient exceeding 150 MeV/m is reported. The cavity has a square cross section which allows excitation in several equidistantly-spaced eigen modes by a bunched drive beam in such a way that the RF fields reach peak values only during time intervals that can be much shorter than for excitation of a single mode, thus exposing the cavity surfaces to strong fields for shorter times. This feature is expected to raise the breakdown and pulse heating thresholds. In order to measure an increase in breakdown threshold surface electric field due to this reduction of exposure time during each RF period, a high-power experiment is planned. Preliminary calculations show that such a study in which comparison of breakdown threshold would be made of a conventional single-mode cavity with a multi-mode cavity can in principle be carried out using the drive beam of the CTF-3 test stand at CERN.
MIT/PSFC, Cambridge, Massachusetts
The University of Texas at Austin, Austin, Texas
Funding: US Department of Energy, Office of High Energy Physics
Negative refraction metamaterials (NR MTL) have been developed at microwave, THz, and optical frequencies. At present, microwave MTL's are studied for applications such as microwave filters and patch antennas. Accelerator-relevant applications, such as measuring electron bunch length using its inverse Cherenkov radiation in a NR MTL, have also been proposed. Here we propose a MTL based linear accelerator structure. The MTL is built as an array of complimentary split-ring resonators cut in two metallic plates. The accelerating electron bunch traverses between the plates. The operating mode's properties and standard accelerator parameters (R/Q, accelerating gradient, etc.) of the proposed structure will be reported.
NSC/KIPT, Kharkov
Essential increase of wakefield intensity at excitation by a long train of relativistic electron bunches when the rectangular dielectric structure is filled with plasma was experimentally observed. A train of bunches was produced by the linear resonant accelerator. Parameters of the beam: energy 4.5 MeV, pulsed current 0.5 A, pulse duration 2 mksec. Such macro-pulse consists of a periodic sequence of 6000 electron bunches. Each electron bunch has duration 60 psec, diameter 1.0 cm, angular spread 0.05 mrad, charge 0.16 nC. Bunches repetition frequency is 2805 MHz. Transit channel for bunches is filled with gas at various pressure. The first portion of the bunches ionizes gas so that plasma frequency is equal to bunch repetition frequency and to the frequency of principal eigen mode of the dielectric structure. Excitation enhancement at such resonant conditions is being studied taking into account the improvement of bunch train propagation in the transit channel and electrodynamics change of the dielectric structure at filling with plasma.
NSC/KIPT, Kharkov
Yale University, Physics Department, New Haven, CT
Omega-P, Inc., New Haven, Connecticut
Yale University, Beam Physics Laboratory, New Haven, Connecticut
Funding: The research was supported by US Department of Energy, Office of High Energy Physics, Advanced Accelerator R & D.
A new scheme for a dielectric wakefield accelerator is proposed that em-ploys a cylindrical multi-zone dielectric structure configured as two concentric dielectric tubes with outer and inner vacuum channels for drive and accelerated bunches. Analytical and numerical studies have been carried out for such coaxial dielectric-loaded structures (CDS) for high-gradient acceleration. An analytical theory of wakefield excitation by particle bunches in a multi-zone CDS has been formulated. Numerical calculations were made for an example of a CDS using dielectric tubes of material with dielectric permittivity 5.7, having external diameters of 2.121 mm and 0.179 mm with inner diameters of 2.095 mm and 0.1 mm. An annular 5 GeV, 5 nC electron bunch with RMS length of 0.14 mm energizes a wakefield on the structure axis having an accelerating gradient of ~600 MeV/m with a transformer ratio ~8. The period of the accelerating field is ~0.38 mm. Full numerical simulation using a PIC code has confirmed results of the linear theory and furthermore has shown the important influence of the quenching wave. The simulation also has shown stable transport of drive and accelerated bunches through the CDS.
NRL, Washington, DC
ANL, Argonne
Euclid TechLabs, LLC, Solon, Ohio
Icarus Research, Inc., Bethesda, Maryland
Funding: Department of Energy, Office of Naval Research, and DoE SBIR Phase II grant DE-FG02-06ER84463
Dielectric-loaded accelerating (DLA) structures, in which a dielectric liner is placed inside a cylindrical metal tube, offer the potential of a simple, inexpensive alternative to copper disk-loaded structures for use in high-gradient rf linear accelerators. A joint Naval Research Laboratory/Euclid Techlabs/Argonne National Laboratory study is under way to investigate the performance of X-band DLA structures using high-power 11.43-GHz radiation from the NRL Magnicon Facility*. The initial goal of the program has been to develop structures capable of sustaining high accelerating gradients. The two significant limitations that have been discovered relate to multipactor loading of the structures and rf breakdown at joints between ceramic sections. We will report the results of several recent structure tests that have demonstrated significant progress in addressing both of these issues. The longer-range goal of the program is to study electron acceleration in DLA structures. For this purpose, we are developing an X-band DLA test accelerator. We will also report the results of initial operation of a 5-MeV injector for the new accelerator.
*C. Jing, W. Gai, J. Power, R. Konecny, S. Gold, W. Liu and A. Kinkead, IEEE Trans. Plasma Sci., vol. 33, pp.1155-1160, August 2005.
SLAC, Menlo Park, California
We present recent progress in the fabrication of a 3D photonic crystal laser accelerator structure. Direct acceleration of electrons by lasers offer promising improvements over traditional RF acceleration techniques in terms of cost, gradient, technology used, and short temporal bunches produced. Microbunching and net acceleration experiments were successfully performed at the E163 facility at SLAC, setting the stage for design, fabrication, and testing of optical structures. This paper describes work done at the Stanford Nanofabrication Facility towards fabricating such structures. A process based on standard optical lithographic techniques was used to fabricate a four layer woodpile photonic crystal with a bandgap centered at 4.55μm and a full width half max of 2.71μm. Infrared spectroscopy measurements were taken and compared with simulations yielding good agreement. SEM images were used to measure fabrication deviations in rod width, rod shape, layer thickness, and alignment, and further simulations are being done to study the effect of these deviations on properties of the accelerating mode excited in the defect of a 20 layer structure currently under design.
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
Plasma Wake Field Accelerator (PWFA) has a very attractive accelerating gradient which can be three orders of magnitude higher than that of the traditional accelerator. In this paper the positron acceleration in a particle beam driven PWFA is studied both in the linear and weakly nonlinear region by using Particle In Cell (PIC) simulation. A preliminary parameters design is obtained for such acceleration scheme.
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
The novel and revolutionary concept of VLA proof of principle is described in this paper. The simulation with the current BNL-ATF parameter shows that electron beam can get net energy from intense laser beam. The initial 20 MeV electron beam with energy spread of 0.001 can get hundreds of keV energy gain with energy spread of 0.010 by interacting with a laser a0=1. BNL-ATF's spectrometer can tell 0.0001 accuracy of energy spread and distinguish 0.001 accuracy energy spread. The proposal has been approved by BNL-ATF and the experiment for this proof of principle is going to be scheduled.
UCLA, Los Angeles, California
SLAC, Menlo Park, California
Duke University, Durham, North Carolina
USC, Los Angeles, California
Funding: Work supported by DOE under contracts DE-FG03-92ER40727, DE-FG52-06NA26195, DE-FC02-07ER41500, DE-FG02-03ER54721.
Recent Plasma Wake-Field Acceleration (PWFA) experiments at Stanford Linear Accelerator Center has demonstrated electron acceleration from 42GeV to 84GeV in less than one meter long plasma section. The accelerating gradient is above 50GeV/m, which is three orders of magnitude higher than those in current state-of-art RF linac. Further experiments are also planned with the goal of achieving acceleration of a witness bunch with high efficiency and good quality. Such PWFA sections with 25 GeV energy gain will be the building blocks for a staged TeV electron-positron linear collider concept based on PWFA (PWFA-LC). We conduct Particle-In-Cell simulations of these PWFA sections at both the initial and final witness beam energies. Different design options, such as Gaussian and shaped bunch profiles, self-ionized and pre-ionized plasmas, optimal bunch separation and plasma density are explored. Theoretical analysis of the beam-loading* in the blow-out regime of PWFA and simulation results show that highly efficient PWFA stages are possible. The simulation needs, code developments and preliminary simulation results for future collider parameters will be discussed.
*M. Tzoufras et al, Phys. Rev. Lett. {10}1, 145002 (2008).
UCLA, Los Angeles, California
Funding: This work was supported by The Department of Energy Grant No.DEFG02-92ER40727.
The self-guiding of relativistically intense but ultra-short laser pulses has been experimentally investigated as a function of laser power, plasma density and plasma length in the so-called "blowout" regime. Although etching of the short laser pulse due to diffraction and local pump depletion erodes the the head of the laser pulse, an intense portion of the pulse is guided over tens of Rayleigh lengths, as observed by imaging the exit of the plasma. Spectrally-resolved images of the laser pulse at the exit of the plasma show evidence for photon acceleration as well as deceleration (pump depletion)in a well defined narrow guided region. This is indicative of the self-guided pulse residing in the wake excited in the plasma. Energy outside the guided region was found to be minimized when the initial conditions at the plasma entrance were closest to the theoretical matching conditions for guiding in the blowout regime. The maximum extent of the guided length is shown to be consistent with the nonlinear pump depletion length predicted by theory.
Yale University, Beam Physics Laboratory, New Haven, Connecticut
Yale University, Physics Department, New Haven, CT
Omega-P, Inc., New Haven, Connecticut
Fermilab, Batavia
Funding: Supported by US Department of Energy, Office of High Energy Physics
A detailed analysis is presented of a new concept for a high current, high gradient proton beam accelerator in a normal conducting (i.e. room temperature) structure. The structure consists of a cascade of RF cavities in a nearly uniform magnetic axial field. The proton energy gain mechanism relies upon cyclotron resonance acceleration in each cavity. In order to check the concept and determine its limits, an engineering design is presented of a four cavity electron counterpart test accelerator under construction that will mimic parameters of the multi-cavity proton accelerator.
QMUL, London
USC, Los Angeles, California
For 70 years particle acceleration schemes have been based on the same technology which places particles onto rf electric fields inside metallic cavities. However, since the accelerating gradients cannot be increased arbitrarily due to limiting effects such as wall breakdown, in order to reach higher energies today’s accelerators require km-long structures that have become very expensive to build, and therefore novel accelerating techniques are needed to push the energy frontier further. Plasmas do not suffer from those limitations since they are gases that are already broken down into electrons and ions. In addition, the collective behavior of the particles in plasmas allows for generated accelerating electric fields that are orders of magnitude larger than those available in conventional accelerators. As plasma acceleration technologies mature, one of the main future challenges is to monoenergetically accelerate a second trailing bunch by multiplying its energy in an efficient manner, so that it can potentially be used in a future particle collider. The work presented here analyzes the use of multiple electron bunches in order to enhance certain plasma acceleration schemes.
LLNL, Livermore, California
TomoTherapy, Madison
TPL, Albuquerque, NM
CPAC, Madison
Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livvermore National Laboratory under Contract DE-AC52-07NA27344.
The dielectric wall accelerator* (DWA) system being developed at the Lawrence Livermore National Laboratory (LLNL) uses fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. High electric field gradients are achieved by the use of alternating insulators and conductors and short pulse times. The system is capable of accelerating any charge to mass ratio particle. Applications of high gradient proton and electron versions of this accelerator will be discussed. The status of the developmental new technologies that make the compact system possible will be reviewed. These include high gradient vacuum insulators, solid dielectric materials, photoconductive switches and compact proton sources.
*Patents pending.
CERN, Geneva
The path towards a multi-TeV e+e- linear collider proposed by the CLIC study is based on the Two Beam Acceleration scheme. Such a scheme is promising in term of efficiency, reliability and cost. The rationale behind the two-beam scheme is discussed in the paper, together with the special issues related to this technology and the R&D needed to demonstrate its feasibility.
LULI, Palaiseau
INRS-EMT, Varennes (Québec)
Osaka University, Graduate School of Engineering, Osaka
Beam optimization of laser-accelerated protons is a crucial point for the development of applications in various areas. Several directions need to be pursued, namely (i) optimization of the high-energy end of the spectrum e.g. for dense plasma radiography, and (ii) enhancement of laser-to-protons conversion efficiency and reduction of divergence e.g. for fast ignition. We will present recent experimental results and simulations on these topics. We will show that high-energy protons in the TNSA regime could be enhanced using low-density plasmas [2] or reduced mass solid targets [3]. The laser-to-protons conversion efficiency is equally sensitive to laser and target parameters and can be increased using ultra-thin targets [4] or reduced mass solid targets [3]. In addition, we will present some results in exploring radiation-pressure acceleration of ions using circularly polarized laser pulses.
[3] S. Buffechoux et al., “Enhanced laser acceleration of protons from reduced mass targets”, in preparation
[4] P. Antici, J. Fuchs et al., IEEE Trans. On Plasma Sci. 36, 1817 - 1820 (2008).
UNL, Lincoln
Funding: Air Force Office of Scientific Research, Defense Advanced Research Projects Agency, Domestic Nuclear Detection Office, Department of Homeland Security
High-power, ultrashort laser pulses have been shown to generate quasi-monoenergetic electron beams from underdense plasmas. Several groups have reported generating high-energy electron beams using either supersonic nozzles* or a capillary based system**. Many issues still remain, with respect to pointing and energy stability of the beam, charge in the monoenergetic component, energy spread, and robustness. We demonstrate for the first time the generation of 300-400 MeV electron beams with 600 pC of charge, using self-guided laser pulses and a stable, high-quality laser pulse. Matching the laser to the plasma is crucial for stable operation since there is minimal nonlinear evolution of the pulse. The beam is highly reproducible in terms of pointing stability and energy with parameters superior to those previously obtained using optical injection***. The stability and compactness of this accelerator make it possible to conceive of mobile applications in non-destructive testing, or long-standoff detection of shielded special nuclear materials. Scaling laws indicate that with a longer plasma and higher laser powers it should be possible to obtain stable, GeV class electron beams.
* S.P.D. Mangles et al., Nature 431, 535-538 (2004.
** W.P. Leemans et al., Nature Physics 2, 696-699 (2006).
*** J. Faure et al., Nature 444, 737-739 (2007).
LBNL, Berkeley, California
Funding: Funded by the U.S. DOE Office of Science HEP including contract DE-AC02-05CH11231, and by DARPA.
A key issue in laser wakefield accelerators (LWFAs) is injection of electrons into the accelerating region of the wake. Typically electron beams have been self-injected into the wake in a highly non-linear process, and at a higher plasma density than that for an optimized guiding and accelerating structure. This in turn limits the electron beam energy and quality that can be achieved. In this talk it is shown that this coupling of injection and acceleration can be addressed for LWFA in a capillary discharge waveguide with the use of a gas jet embedded into the capillary to longitudinally tailor the electron density profile. Previous experiments without a gas jet have shown self-trapping and acceleration of electrons with energy up to 1 GeV [Leemans et al., Nature Phys. Vol. 2, 696, 2006]. By adding a gas jet in the capillary it has been shown that electrons can be trapped and accelerated to high-energy using plasma densities in the capillary lower than in previous experiments, and that use of this technique improved electron beam properties.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
Nippon Advanced Technology Co. Ltd., Ibaraki-prefecture
J-PARC RCS is in the beam commissioning period. Some longitudinal beam gymnastics and the acceleration has been successfully perfomed under the high intensity operation. We have developed a longitudinal particle tracking code, which includes beam loading and space charge effects. The comparison between the beam test result and the particle tracking simulation is described.
Kyoto ICR, Uji, Kyoto
MPI-K, Heidelberg
Kyoto IAE, Kyoto
JINR, Dubna, Moscow Region
NIRS, Chiba-shi
HU/AdSM, Higashi-Hiroshima
AEC, Chiba
Funding: The present work was supported by Advanced Compact Accelerator Development program by MEXT of Japanese Government. Support from Global COE, The Next Generation of Physics, is also greatly appreciated.
Creation of 3-dimensional crystalline beam by application of laser-cooling for a Mg ion beam with kinetic energy of 40 keV is a major research subject of the ion storage ring, S-LSR, at ICR, Kyoto University*. Based on the success of longitudinal laser cooling in 2007**, an approach to extend the effect of laser cooling to the transverse degree of freedom has been performed. An indication of heat transfer from the horizontal to longitudinal direction has been obtained by synchro-betatron coupling. By application of bunched beam laser cooling at the operation point around (2.07, 1.10), the momentum spread of the cooled ion beam has been observed to have a peak at a synchrotron tune around 0.07 and simultaneously transverse beam size seems to be reduced in this region. An increase of beam brightness in the horizontal profile has also been observed by measuring spontaneous emission of absorbed laser light. In the present paper, strategy to reach the final 3-dimensional crystalline state by application of 3-dimensional laser cooling by careful adjustment of coupling among 3 degrees of freedom is to be presented based upon the recent experimental results.
*A. Noda, M. Ikegami, T. Shirai, New Journal of Physics, 8, 288-307(2006).
**M. Tanabe et al.,Applied Physics Express 1, 028001-1-028001-3 (2008).
Brunel University, Middlesex
CEA, Gif-sur-Yvette
The Non Scaling FFAG EMMA lattice allows a important displacement of the magnets in the radial direction. From this peculiarity, interesting studies of beam dynamics can be performed comparing simulated and experimental results. Being able to study a specific resonance, choosing a certain set of parameters for the lattice is really challenging. Simulations have been done integrating particle trajectories with Zgoubi through Magnetic Field Map created with OPERA. From a chosen tune evolution, one can find the corresponding magnets' configuration required by interpolating between a various sets of Field Map. Relative position and strength of the magnets are degrees of freedom. However, summing field maps requires a special care since the real magnetic field created by two magnets is not obviously linearly dependent on each single magnet. For this reason, frequently used hard edge and fringe field models may not be accurate enough. This linearity of the magnetic field has been studied directly through OPERA finite element method solutions and further on with Zgoubi tracking results.
Euclid TechLabs, LLC, Solon, Ohio
Technion, Haifa
Funding: Work supported by the US Department of Energy.
The PASER is one of the first advanced accelerator modeling applications that requires a more sophisticated treatment of dielectric and paramagnetic media properties than simply assuming a constant permittivity or permeability. So far the PASER medium has been described by a linear, frequency-dependent, single-frequency, scalar dielectric function. We have been developing algorithms to model the high frequency response of dispersive, active, and nonlinear media with an emphasis on areas most useful for PASER simulations. The work described also has applications for modeling of other electromagnetic problems involving realistic dielectric and magnetic media. Results to be reported include treatment of multiple Lorentz resonances based on auxiliary differential equation, Fourier, and hybrid approaches, and Kerr, Brillouin, and Raman optical nonlinearities.
IAP, Frankfurt am Main
For the development of high energy and high duty cycle RFQs accurate particle dynamic simulation tools are important optimize designs especially in high current applications. To describe the external fields in RFQs the Poisson equation has to be solved taking the boundary conditions into account. In the newly developed subroutines this is done by using a finite difference method on a grid. The results of this improvement are shown and compared to the old two term and multipol expansions.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK/JAEA, Ibaraki-Ken
In order to observe two-dimensional beam profiles in the longitudinal phase space, the reconstruction techniques with the computer tomography algorithms can be adopted at the J-PARC RCS. On the assumption that the longitudinal profiles should not be disturbed for one period of the synchrotron oscillation, such two-dimensional profiles can be reconstructed easily from one-dimensional bunch beam profiles, which are measured for every turn by the wall current monitor. In this presentation, we introduce the experimental results and the comparison to the longitudinal beam tracking simulation, and we discuss the technical issues and applicability of this longitudinal tomography techniques.
LLNL, Livermore, California
LBNL, Berkeley, California
Funding: Work performed under the auspices of US Department of Energy by LLNL under Contract DE- AC52-07NA27344 and by LBNL under Contract DE-AC03-76SF00098.
The Virtual National Laboratory for Heavy-Ion Fusion is developing a physics design for NDCX-II, an experiment to study warm dense matter heated by ions near the Bragg-peak energy. Present plans call for using about thirty induction cells to accelerate 30 nC of Li+ ions to more than 3 MeV, followed by neutralized drift-compression. To heat targets to useful temperatures, the beam must be compressed to a sub-millimeter radius and a duration of about 1 ns. An interactive 1-D particle-in-cell simulation with an electrostatic field solver, acceleation-gap fringe fields, and a library of realizable analytic waveforms has been used for developing NDCX-II acceleration schedules. Multidimensional source-to-final-focus simulations with the particle-in-cell code Warp have validated this 1-D model and have been used both to design transverse focusing and to compensate for injection non-uniformities and 3-D effects. Results from this work are presented, and ongoing work to replace the analytic waveforms with output from circuit models is discussed.
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
Funding: Institute for Nuclear Studies, Swierk, Poland
The five parameter method of tuning of biperiodic π/2 linear accelerating structure is presented. The method consists in analytical calculation of the five parameters determining the dispersion relation of such structure: two eigen frequencies fa and fc of accelerating and coupling cavities, the first coupling coefficient kac and two second coupling coefficients kaa and kcc, using five measured dispersion frequencies. Usually the process of tuning is based on sets of 3 cavities however, to include directly also the second coupling coeffients kaa and kcc, one should consider sets composed of five cells. For each such set, using the dispersion relation, a set of five equations for five unknowns is solved by successive elimination of unknowns by expressing them in terms of Fa = fa/f π/2. For Fa one obtains biquadratic equation. Coefficients of this equation are expressed as functions of measured quantities: dispersion phases and frequencies. Knowing Fa all other parameters are easily calculated and the Stop Band SB = fa fc . In this way, on each step of building up the structure one can control precision of measurements and the Stop Band.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
JAEA/LINAC, Ibaraki-ken
In the J-PARC LINAC, BPMs with 4 strip lines (up, down, right, left) have been used to monitor the beam position by taking log ratio of signals on the opposite (facing) sides of stirp lines. We are studying possibility to monitor beam phase by measuring phase of summed signal of all four stlip lines. In this paper, status of the study is presented.
ELSA, Bonn
Acceleration of polarized electrons in a fast ramping circular accelerator poses challenging demands on the control and stabilization/correction of the closed orbit and the vertical betatron tune, in particular on the fast energy ramp. In order to successfully compensate depolarizing resonances at a ramping speed of up to 7.5 GeV/sec (dB/dt = 2 T/sec), at ELSA the closed orbit is stabilized with high precision using a system of Beam Position Monitors and steerer magnets distributed along the ring. During acceleration, the beam positions are read out from the BPMs at a rate of 1 kHz and energy-dependent orbit corrections are applied accordingly by means of offline feed-forward techniques. The system is thus sensitive to dynamic effects and an orbit stabilization of 100 microns rms is achieved routinely. At the same time, the betatron tunes are stabilized to 0.01 by time-resolved tune measurement and appropriate manipulations of the machine optics. This presentation will cover the concepts and implementation of techniques for orbit stabilization required for the acceleration of a polarized electron beam in the fast ramping stretcher ring ELSA.
CLASSE, Ithaca, New York
The production of ultra-short x-rays in Cornell's Energy Recovery Linac (ERL) requires electron bunch lengths of less than 100fs with minimal transverse emittance growth and energy spread. Because the linac consists of two sections separated by an arc, CSR forces limit the bunch length in the linac, and bunch compression has to be installed after acceleration. Creation of such short bunches requires a second order bunch compression scheme with correction of the third order dispersion. In this paper, we discuss possible bunch compression systems and explore the benefits of each using the tracking program TAO including CSR forces. Overall, we find that a FODO compressor utilizing dipole, quadrupole and sextupole magnets can achieve the design goals of the short pulse mode.
KEK, Ibaraki
KURRI, Osaka
Crossing of integer resonance in scaling FFAG accelerator has been studied experimentally with the injector of 150MeV FFAG complex at Kyoto University Research Reactor Institute (KURRI). The results were analyzed based on harmonic oscillator model and compared with beam tracking simulations.
CERN, Geneva
The aim of the last CLIC test facility CTF3, built at CERN by an international collaboration, is to prove the main feasibility issues of the CLIC two-beam acceleration technology. The main points which CTF3 should demonstrate by 2010 are the generation of a very high current drive beam and its use to efficiently produce and transfer RF power to high-gradient accelerating structures. To prove the first point a delay loop and a combiner ring have been built, following a linac, in order to multiply the current by a factor two and four, respectively. The power generation and transfer and the high gradient acceleration are instead demonstrated in the CLIC experimental area (CLEX), where the drive beam is decelerated in special power extraction structures(PETS). In this paper we describe the results of the combination in the ring, properly working after the cure of the vertical instability which limited high current operation, and the commissioning of the new beam lines installed in the second half of 2008, including response matrix analysis and dispersion measurements used to validate the optics model. The results of the energy transfer will be also briefly described.
JAI, Oxford
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
PAMELA (Particle Accelerator for MEdicaL Applications) is a design for a non-scaling Fixed Field Alternating Gradient accelerator facility for Charged Particle Therapy, using protons and light ions such as carbon to treat certain types of cancer. A lattice has been designed which constrains the variation of betatron tunes through acceleration and thus avoids integer resonance crossing and beam blow-up. This paper outlines the design and performance of this proposed PAMELA lattice.
KEK, Ibaraki
KURRI, Osaka
Harmonic number jump (HNJ) acceleration in scaling FFAG accelerator, especially for muon acceleration in neutrino factory, has been studied. Criterions for HNJ acceleration were clarified and beam tracking simulations have been carried out.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Using an FFAG for rapid-cycling proton acceleration has the advantage that the acceleration cycle is no longer subject to constraints from the main magnet power supply used in an RCS. The RF can be used to its maximum potential to increase the energy range in a short 50Hz cycle as proposed for multi-MW proton driver projects. The challenge becomes an optical one of maintaining a stable lattice across a wide range of beam momenta without magnet sizes or the ring circumference making the machine prohibitively expensive for its purpose. Investigations of stable energy ranges for proton FFAG lattices in the few GeV regime (relativistic but not ultra-relativistic) are presented here.
UMD, College Park, Maryland
Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office.
Understanding the dynamics of the acceleration of high-intensity space-charge-dominated electron and ion beam is very important. Accelerating by steps a space-charge-dominated beam can be fundamentally different from beams at lower intensities, because at sufficiently high beam intensities the beam response to acceleration can drive to some unknown instabilities leading to a significant beam losses. This work analyses the acceleration of the University of Maryland Electron Ring (UMER) beam, i.e., high current, low-energy and space-charge-dominated electron beam which is applicable, on a scale basis, to a large class of other beam systems. We use the WARP particle-in-cell code to perform simulations that are compared with theoretical predictions and preliminary experimental results.
UCLA, Los Angeles, California
PSI, Villigen
QUINDI has been developed to address the numerical challenge of calculating the radiation spectra from electron bunches in bending magnet systems. Since the introduction of QUINDI, many improvements and features have been added. QUINDI now supports a 3D model for bending magnets which includes fringing fields. A more modular approach has been achieved which allows better interoperability with other tracking and radiation codes. There have been many updates to the electric field calculation and spectrum processing, as well as to the post-processor, SpecGUI.
CIPS, Boulder, Colorado
Funding: This work is supported by the U.S. Department of Energy grant DE-FG02-04ER41317.
Through computer simulation, a 2D photonic crystal (PhC) cavity formed from a truncated triangular lattice of dielectric rods is optimized to confine a single accelerating mode efficiently. Photonic crystals have the ability to reflect radiation within only certain frequency ranges, called bandgaps; the bandgaps are determined by the geometry and material of the PhC and so are tunable. For truncated PhCs, reflection is incomplete. Therefore, the confinement of bandgap frequencies to a cavity within a truncated PhC is weakened by the severity of the truncation. For a cavity made of 18 dielectric rods in a truncated triangular lattice arrangement, the desired accelerating cavity mode is weakly confined. Adjusting the positions and sizes of the dielectric rods away from the best lattice configuration within an optimization procedure gives unintuitive structures, ultimately increasing the confinement of the accelerating mode by a factor of 100. Confinement of higher-order modes is also dramatically reduced by the optimization. Similar increases in confinement of the fundamental accelerating mode are found for a 24-rod structure.
MPI-P, München
BINP SB RAS, Novosibirsk
HHUD, Dusseldorf
The idea of proton bunch driven plasma wakefield acceleration was recently proposed. The motivation is to use an existing high energy proton beam to drive a large amplitude accelerating electric field, and then accelerate the electrons to the energy frontier. Simulations of the plasma wakefield production and acceleration process from a PIC code are given in this paper. In order to get high accelerating field, the required proton bunch length is extremely small. The preliminary design parameters for bunch compression are also presented.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
USC, Los Angeles, California
High gradient acceleration of electrons has recently been achieved in meter scale plasmas at SLAC. Results from these experiments show that the wakefield is sensitive to parameters in the electron beam which drives it. In the experiment the bunch lengths were varied systematically at constant charge. Here we investigate the correlation of peak beam current to the wake amplitude. The effect of beam head erosion will be discussed and an experimental limit on the transformer ratio set. The results are compared to simulation.
UCLA, Los Angeles, California
Funding: This work is supported by the DOE Contract No. DE-FG03-92ER40727.
Over the last several years, the Target Normal Sheath Acceleration (TNSA) mechanism in solid density plasmas produced by a laser pulse has achieved proton energies up to 10’s of MeV and quasi-monoenergetic beams at lower energies. Although solid-target experiments have demonstrated high-charge and low-emittance proton beams, little work has been done with gaseous targets which in principle can be operated at a very high repetition frequency. At the Neptune Laboratory, there is an ongoing experiment on CO2 laser driven proton acceleration using a rectangular (0.5x2mm) H2 gas jet as a target. The main goal is to study the coupling of the laser pulse into a plasma with a well defined density in the range of 0.5 to 2 times critical density and characterize the corresponding spectra of accelerated protons. Towards this end, the Neptune TW CO2 laser system is being upgraded to produce shorter 1-3ps pulses. These high-power pulses will allow us to investigate acceleration of protons via the TNSA and Direct Ponderomotive Pressure mechanisms as well as their combination. The current status of the proton source experiment will be presented.
Fermilab, Batavia
In the paper the results are presented for calculation of the transverse wake and RF kick from the power and HOM couplers of the acceleration structure. The beam emittance dilution caused by the couplers is calculated for the main linac and bunch compressor of ILC. It is shown that for the bunch compressor this effect may constitute a problem, and modification of the coupler unit may be necessary in order to preserve the cavity axial symmetry.
IAP, Frankfurt am Main
GSI, Darmstadt
For the research program with cooled antiprotons at FAIR a dedicated 70MeV, 70mA proton injector is needed. The main acceleration of this room temperature injector will be provided by six coupled CH-cavities operated at 325MHz. Each cavity will be powered by a 3 MW klystron (6 in total). For the second acceleration unit from 11.7 to 24.3 MeV measurements on a 1:2 scaled model are performed. This tank is now ready for construction and will be used for RF power tests at GSI. The RF power test installations are underway. This paper presents the CH-DTL design and especially the status of the first power cavity.
Imperial College of Science and Technology, Department of Physics, London
The PAMELA project aims to design an ns-FFAG accelerator for cancer therapy using protons and carbon ions. For the injection system for carbon ions, an RFQ is one option for the first stage of acceleration. An integrated RFQ design process has been developed using various software packages to take the design parameters for the RFQ, convert this automatically to a CAD model using Autodesk Inventor, and calculate the electric field map for the CAD model using CST EM STUDIO. Particles can then be tracked through this field map using Pulsar Physics’ General Particle Tracer (GPT). Our software uses Visual Basic for Applications and MATLAB to automate this process and allow for optimisation of the RFQ design parameters based on particle dynamical considerations. Initial particle tracking simulations based on modifying the field map from the Front-End Test Stand (FETS) RFQ design have determined the best operating frequency for the PAMELA RFQ to be close to 200 MHz and the length approximately 2.3 m. The status of the injector design with an emphasis on the RFQ will be presented, together with the results of the particle tracking.
LANL, Los Alamos, New Mexico
Muon accelerators are proposed world wide for future neutrino factory, muon colliders and other applications. One of the problem on accelerating muons is their large emittance as well as huge energy spreads. We carried out some simulation works on large acceptance muon linear accelerator that operates at mixed buncher / acceleration mode. The designed linac has following features: iris structure of 12 cm diameter, inject ~100 MeV muon beam and accelerates to several 100 MeV, 700 MHz and 25 MV/m peak field. Further acceleration of the muon beam can be easily done by extending the muon linear accelerator. According to the simulation, our linac can accelerates DC muon beam of 20 - 100 MeV range with 20 % phase acceptance.
Soreq NRC, Yavne
ACCEL, Bergisch Gladbach
The Soreq Applied Research Accelerator Facility, SARAF, is currently under construction at Soreq NRC. SARAF is based on a continuous wave (CW), proton/deuteron RF superconducting linear accelerator with variable energy (540 MeV) and current (0.04-2 mA). SARAF is designed to enable hands-on maintenance, which implies beam loss below 10-5 for the entire accelerator. Phase I of SARAF consists of a 20 keV/u ECR ion source, a low energy beam transport section, a 4-rod RFQ, a medium energy (1.5 MeV/u) transport section, a superconducting module housing 6 half-wave resonators and 3 superconducting solenoids, a diagnostic plate and a beam dump. Phase II will include 5 additional superconducting modules. The ECR source is in routine operation since 2006, the RFQ is in routine operation with protons since 2008 and has been further operated with molecular hydrogen and deuterons. The superconducting module is being operated and characterized with protons. Phase I commissioning results, their comparison to beam dynamics simulations and Phase II plans will be presented.