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MO4PBC04 The Wisconsin Free Electron Laser Initiative laser, electron, FEL, gun 109
 
  • K. Jacobs, J. Bisognano, M. Bissen, R.A. Bosch, M.A. Green, H. Höchst, K.J. Kleman, R.A. Legg, R. Reininger, R. Wehlitz
    UW-Madison/SRC, Madison, Wisconsin
  • W. Graves, F.X. Kärtner, D.E. Moncton
    MIT, Cambridge, Massachusetts
 
 

Funding: Work supported by the University of Wisconsin - Madison. SRC is supported by the U.S. National Science Foundation under Award No. DMR-0537588.


The University of Wisconsin-Madison/Synchrotron Radiation Center and MIT are developing a design for a seeded VUV/soft X-ray Free Electron Laser serving multiple simultaneous users. The present design uses an L-band CW superconducting 2.2 GeV electron linac to deliver 200 pC bunches to multiple FELs operating at repetition rates from kHz to MHz. The FEL output will be fully coherent both longitudinally and transversely, with tunable pulse energy, cover the 5-900 eV photon range, and have variable polarization. We have proposed a program of R&D to address the most critical aspects of the project. The five components of the R&D program are:

  1. Prototyping of a CW superconducting RF photoinjector operating in the self-inflating bunch mode.
  2. Development of conventional laser systems for MHz seeding of the FEL, and femtosecond timing and synchronization.
  3. Address thermal distortion and surface contamination issues on the photon optics.
  4. Investigate advanced undulator concepts to help reduce facility cost and/or extend performance.
  5. Perform detailed modeling of all aspects of the FEL, as part of production of a Conceptual Design Report for the FEL facility.

 

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MO4GRI03 Laser Systems for Next Generation Light Sources laser, FEL, gun, optics 122
 
  • M.B. Danailov, A.A. Demidovich, R. Ivanov, I. Nikolov, P. Sigalotti
    ELETTRA, Basovizza
  • Yu.V. Loiko
    B.I. Stepanov Institute of Physics, Belarus
 
 

Funding: The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2


Particle accelerator and laser technologies are effectively combining with each other in the development of next generation light sources, with the latter being one of the key factors determining the ultimate performance of these machines. VUV and X-FEL facilities take advantage of laser technology at many strategic points: creation of the electron bunch (photo-injector laser), acceleration (laser heater), undulators (seed laser), beam diagnostics (electro-optic sampling lasers), user experiments (pump-probe lasers). The talk will discuss the main requirements and challenges (photoinjector and seed lasers in particular) for the laser systems and will illustrate proposed solutions and obtained results. Recent laser achievements that are likely to have impact on important developments like high average power injectors, different guns,tunable short wavelength FEL seeding will also be addressed.

 

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MO6PFP022 Main Magnet and Central Region Design for a 10 MeV PET Cyclotron CYCHU-10 cyclotron, controls, beam-losses, ion-source 184
 
  • B. Qin, M. Fan, D. Li, K.F. Liu, Y.Q. Xiong, J. Yang, T. Yu, L. Zhao
    HUST, Wuhan
 
 

Funding: Work supported by National Nature Science Foundation of China (10435030) and National Science Foundation for Post-doctoral Scientists of China (20080430973)


Low energy compact cyclotrons for short-life isotopes production delivered to the Positron Emission Tomography (PET) facilities have foreseeable prospects with growing demands in medical applications. The Huazhong University of Science and Technology (HUST) proposed to develop a 10MeV PET cyclotron CYCHU-10. The design study of the main magnet and the central region was introduced. A matrix shaping method with the radial fringe field effect and artificial control was adopted to obtain field isochronisms precisely. The central region was optimized to attain 35° RF phase acceptance and low vertical beam loss rate.

 
MO6RFP001 Enhancing RHIC Luminosity Capabilities with In-situ Beam Pipe Coating plasma, electron, vacuum, ion 345
 
  • A. Hershcovitch, M. Blaskiewicz, W. Fischer
    BNL, Upton, Long Island, New York
  • H.J. Poole
    PVI, Oxnard
 
 

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.


Electron clouds have been observed in many accelerators, including RHIC at BNL. They can limit the machine performance through pressure degradation, beam instabilities or incoherent emittance growth. The formation of electron clouds can be suppressed with beam pipe surfaces that have low secondary electron yield. Also, high wall resistivity in accelerators can result in unacceptably high ohmic heating levels for superconducting magnets. These are concerns RHIC, as its vacuum chamber in the superconducting dipoles is made from relatively high resistivity 316LN stainless steel. The high resistivity can be addressed with a copper (Cu) coating; a reduction in the secondary electron yield can be achieved with a titanium nitride (TiN) or amorphous carbon (a-C) coating. Applying such coatings in an already constructed machine is rather challenging. We sta rted developing a robotic plasma deposition technique for in-situ coating of long, small diameter tubes. The technique entails fabricating a device comprising of staged magnetrons and/or cathodic arcs mounted on a mobile mole for deposition of about 5 μm (a few skin depths) of Cu followed by about 0.1 μm of TiN (or a-C).

 
MO6RFP014 Thin Film Coating for the Upgrade of the Ion Synchrotron SIS18 at GSI ion, vacuum, dipole, quadrupole 378
 
  • M.C. Bellachioma, H. Kollmus, A. Krämer, J. Kurdal, H. Reich-Sprenger
    GSI, Darmstadt
  • M. Bender
    LMU, München
 
 

Funding: EU design study, contract 515876, DIRAC-PHASE-1, RP6 SIS 18-2


For the future FAIR facility intensities up to 1012 U28+ ions per second are required. For this purpose the existing heavy ion synchrotron SIS18, which will serve as injector, has to be upgraded. Since the required base pressure is 10-10 Pa, among the different measures undertaken to improve the existing UHV system, the installation of NEG coated magnet chambers is foreseen. Two magnetron sputtering facilities were designed and commissioned at GSI to perform the coating. The characterization of the thin films has been carried out by RBS and XPS. Considering that the vacuum chambers mounted in accelerators undergo several venting-activation cycles, a deep investigation on the NEG aging was performed by ERDA. Fourteen dipole and one quadrupole chambers were coated and installed in the SIS 18, and the replacement of the remaining magnet pipes will follow in the next years. Additionally to overcome the dynamic vacuum instability a collimation system equipped with thin film coated absorbers was successfully tested in 2008. The coating facilities, their operating mode, the results achieved on the thin film characterization, and the ones obtained in the SIS 18 are presented.

 
MO6RFP015 Gas Desorption from TiN-Coated Copper Beam Duct electron, vacuum, positron, proton 381
 
  • K. Shibata, H. Hisamatsu, K. Kanazawa, M. Shirai, Y. Suetsugu
    KEK, Ibaraki
 
 

The titanium nitride (TiN) coating inside a beam duct has been recently attracting attention as a measure to mitigate the electron cloud effect in positron/proton rings. Here studied is the gas desorption from the TiN-coated copper beam duct, which will be adopted in the upgrade of KEK B-factory (KEKB). In the experiment, the pressure in a TiN-coated duct was measured and compared with that in a non-coated one. The TiN film (200 nm thick) was coated by DC magnetron sputtering at KEK. After an air exposure for the previously-determined period, the duct was evacuated by a turbo-molecular pump (300 l/s). At 50 hours after evacuation, the pressure was about 4 times larger than that for the case of the non-coated one. The residual gas was mainly water. In order to fine the minimum baking temperature to decrease the gas desorption from the TiN coating, the pressures were measured after the baking by changing the temperatures in the practical range, from 50 to 150 degrees. The pressure after the baking at 80 degrees was finally found to be comparable to that for the non-coated one. This paper describes these results in detail including the measurements of gas desorption rates.

 
MO6RFP023 Experimental Study of Stainless Steel Vacuum Chamber with TiN Film Coating vacuum, photon, survey, synchrotron 401
 
  • Y. Wang, L. Fan, L. Liu, J. P. Wang, W. Wei, B. Zhang
    USTC/NSRL, Hefei, Anhui
  • Y.F. Zhang
    IHEP Beijing, Beijing
 
 

TiN coating has been widely applied in surface treatments of particle accelerator vacuum chambers because of its characteristics such as good electrical conductivity, stability of performance, ability to block hydrogen permeation, low SEY, etc. With DC sputtering, TiN film has been coated on the inner face of a stainless steel pipe vacuum chamber, 86 mm in diameter and 2300 mm in length. The vacuum performances testing of the coated chamber has also been done, including thermal outgassing rate measurement, PSD measurement, and SEY measurement of samples. Compared with those of uncoated stainless steel chamber, the results show that coating TiN film is a very effective method of the treatment of particle accelerator vacuum chamber.

 
MO6RFP024 Deposition of Titanium-Zirconium-Vanadium Films by DC Magnetron Sputtering electron, vacuum, target, radiation 404
 
  • Y. Wang, L. Fan, W. Li, J. P. Wang, W. Wei, B. Zhang
    USTC/NSRL, Hefei, Anhui
  • Y.F. Zhang
    IHEP Beijing, Beijing
 
 

Titanium-Zirconium-Vanadium (TiZrV) nonevaporable getter (NEG), which can be fully activated after 4 hours heating at 200°;C, has been applied in many accelerators owing to the outstanding vacuum performance. In our experiments, TiZrV films have been deposited onto the inner face of stainless steel pipes via DC sputtering using argon gas as the sputtering gas. Samples have been investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) to determine film composition and thickness, and by X-ray diffraction (XRD) to determine film structure and morphology. Second Electron Yields (SEY) of the TiZrV film have also been measured.

 
MO6RFP034 The EBIT Charge State Booster for Exotic Beam Reacceleration at MSU electron, gun, ion, simulation 429
 
  • O.K. Kester, G. Bollen, M.J. Johnson, M. A. Kostin, J. Ottarson, M. Portillo, S. Schwarz, C. Wilson
    NSCL, East Lansing, Michigan
 
 

The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is implementing a system to reaccelerate rare isotope beams from projectile fragmentation to energies of about 3 MeV/u. The reacceleration of stopped radioactive beams from projectile fragmentation at the NSCL/MSU makes use of charge state breeding in an Electron Beam Ion Trap (EBIT) to provide a compact and cost efficient system layout of MSU’s ReA3. The MSU EBIT breeder device will provide a high electron beam current density of about 104 A/cm2 making it well suited to rapidly increase the charge state of short-lived isotopes within tens of milliseconds or less. In addition, the breeder is optimized to provide a high storage capacity, a high beam acceptance and uses a continuous injection and beam accumulation scheme explicitly, which makes it unique. To match the beam of singly charged rare isotope ions into the acceptance of the EBIT and to analyze and purify the EBIT beams, a sophisticated beam line and diagnostic system is required. The present paper will present an overview and the status of the ReA3 EBIT.

 
MO6RFP037 Development of the SNS External Antenna H- Ion Source plasma, ion, ion-source, gun 438
 
  • R.F. Welton, J.R. Carmichael, D.W. Crisp, S.N. Murray, T.R. Pennisi, M. Santana, M.P. Stockli
    ORNL, Oak Ridge, Tennessee
  • B. Han
    ORNL RAD, Oak Ridge, Tennessee
 
 

Funding: The work at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, was performed under contract DE-AC05-00OR2275 for the US Department of Energy.


The U.S. Spallation Neutron Source (SNS) is an accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to insure that we will meet our operational commitments as well as provide for future facility upgrades with high reliability, we have developed an RF-driven, H- ion source based on a ceramic aluminum nitride (AlN) plasma chamber*. This source is expected to enter service as the SNS neutron production source starting in 2009. This report details the design of the production source which features an AlN plasma chamber, 2-layer external antenna, cooled-multicusp magnet array, Cs2CrO4 cesium system and a Molybdenum plasma ignition gun. Performance of the production source both on the SNS accelerator and SNS test stand is reported. The source has also been designed to accommodate an elemental Cs system with an external reservoir which has demonstrated unanalyzed beam currents up to ~100mA (60Hz, 1ms) on the SNS ion source test stand.


*R.F. Welton, et al., “Next Generation Ion Sources for the SNS”, Proceedings of the 1st Conference on Negative Ion Beams and Sources, Aix-en-Provence, France, 2008

 
MO6RFP043 Design of an SRF Gun for Polarized Electron Beams gun, SRF, electron, vacuum 454
 
  • H. Bluem, D. Holmes, T. Schultheiss
    AES, Medford, NY
  • I. Ben-Zvi, A. Burrill, J. Kewisch, D. Pate, T. Rao, R.J. Todd, E. Wang, Q. Wu
    BNL, Upton, Long Island, New York
 
 

Funding: AES is funded under DOE SBIR contract #DE-FG02-06ER84450. BNL work is performed under DOE contract #DE-AC02-98CH10886.


The use of an RF electron gun with a magnetized cathode in place of a DC gun for ILC may reduce the requirements for emittance damping rings. Maintaining adequate lifetime of the necessary cathode material requires vacuum levels in the 10-11 torr range. While vacuum levels around the 10-9 torr range are common in a normal conducting RF gun, the cryogenic pumping of the cavity walls of a superconducting RF (SRF) gun may maintain vacuum in the range needed for GaAs cathode longevity. Advanced Energy Systems, Inc. is collaborating with Brookhaven National Laboratory to investigate the generation of polarized electron beams using a SRF photocathode gun. The team is developing an experiment to study the quantum lifetime of a GaAs cathode in a SRF cavity and investigate long term cavity performance while integrated with a cesiated GaAs cathode*. In addition to the experimental investigation, a design is being developed that is compatible with the production of high aspect ratio polarized electron beams. The mechanical and physics aspects of this design will be discussed.


*J. Kewisch, et. al., Presentation at PAC09.

 
MO6RFP045 Photocathode Studies for Ultra-Low Emittance Electron Sources electron, emittance, FEL, laser 458
 
  • K.C. Harkay, Y.L. Li, K. Nemeth, R.A. Rosenberg, M. White
    ANL, Argonne
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois
 
 

Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.


Future x-ray light sources such as FELs and ERLs impose requirements on emittance and bunch repetition rate that are very demanding on the electron source. Even if perfect compensation of space-charge effects could be attained, the fundamental cathode emission properties determine a lower bound on achievable source emittance. Development of ultra-low-emittance sources is a rapidly evolving area of R&D with exciting new results measured for low bunch charge, but it is very difficult to compare different results and quantify what works. The study of photocathodes, with the goal of optimizing for low emittance, is limited in scope. In this paper, we describe an R&D effort to systematically measure and design the fundamental properties of photocathodes suitable for an FEL or ERL. We plan to apply surface analysis lab techniques to characterize photoemission, and then correlate material properties with emittance. On the theory side, we plan to calculate electron band structure for crystal surfaces, correlate with lattice parameters and work function, and then estimate the transverse momentum using the three-step model. The status and results to date of this effort will be reported.

 
MO6RFP048 Simulation Study of a Normal-Conducting RF Photoinjector for ERL X-Ray Sources gun, cavity, simulation, emittance 467
 
  • C.-X. Wang
    ANL, Argonne
 
 

Funding: This work was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.


Low-frequency normal-conducting photoinjectors have the potential to generate CW beam due to low frequency and relatively low field. They can provide a much higher accelerating field at the cathode than envisioned DC injectors but without the complexity involved in superconducting rf injectors. Low frequency allows a relatively long bunch near the cathode to reduce space-charge effects, which is detrimental for generating demandingly high-brightness beams. However, low frequency means higher bunch charge for a given average current, counteracting the potential benefits of low-frequency rf injectors. Furthermore, significant bunch length reduction in the injectors is often needed, which may degrade transverse brightness. To explore the potential of a normal-conducting injector for the envisioned ERL upgrade of the Advanced Photon Source, we made a preliminary design and searched for a suitable solution using genetic optimization. Simulation results are presented.

 
MO6RFP049 An Experiment to Test the Viability of a Gallium-Arsenide Cathode in a SRF Electron Gun gun, electron, vacuum, ion 470
 
  • J. Kewisch, I. Ben-Zvi, A. Burrill, D. Pate, T. Rao, R.J. Todd, E. Wang, Q. Wu
    BNL, Upton, Long Island, New York
  • H. Bluem, D. Holmes, T. Schultheiss
    AES, Medford, NY
 
 

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.


Gallium arsenide cathodes are used in electron guns for the production of polarized electrons. In order to have a sufficient quantum efficiency lifetime of the cathode the vacuum in the gun must be 10-11 torr or better, so that the cathode is not destroyed by ion back bombardment. All successful polarized guns are DC guns, because such vacuum levels can not be obtained in normal conducting RF guns. A superconductive RF gun may provide a sufficient vacuum level due to cryo-pumping of the cavity walls. We report on the progress of our experiment to test such a gun.

 
MO6RFP050 Ion Bombardment in RF Photoguns ion, gun, SRF, electron 473
 
  • E. Pozdeyev, A. Kayran, V. Litvinenko
    BNL, Upton, Long Island, New York
 
 

A linac-ring eRHIC design requires a high-intensity CW source of polarized electrons. An SRF gun is viable option that can deliver the required beam. Numerical simulations presented elsewhere have shown that ion bombardment can occur in an RF gun, possibly limiting lifetime of a NEA GaAs cathode. In this paper, we analytically solve the equations of motion of ions in an RF gun using the ponderomotive potential of the RF field. We apply the method to the BNL 1/2-cell SRF photogun and demonstrate that a significant portion of ions produced in the gun can reach the cathode if no special precautions are taken. Also, the paper discusses possible mitigation techniques that can reduce the rate of ion bombardment.

 
MO6RFP051 High-Brightness Electron Beam Studies at the NSLS SDL emittance, electron, laser, gun 476
 
  • X.J. Wang, Y. Hidaka, J.B. Murphy, B. Podobedov, H.J. Qian, S. Seletskiy, Y. Shen, X. Yang
    BNL, Upton, Long Island, New York
  • C.-X. Tang
    TUB, Beijing
 
 

There is a growing interest in optimizing the electron beam for an X-ray Free Electron Laser (FEL) in the low charge (10 to 200 pC) and femto-seconds regimes. We have experimentally demonstrated sub-picosecond high-brightness electron beam for a 40 pC charge with ballistic bunch compression and a reduced laser spot size*. Simulation studies showed the feasibility of generating 10 femto-seconds kilo-ampere electron beam with a 20 pC charge**. This paper reports the progress of experimental demonstration of a femto-seconds kilo-ampere electron beam at the NSLS Source Development Lab (SDL). The femto-seconds kilo-ampere electron beam will be used to drive a self-amplified spontaneous emission (SASE) FEL, and SASE FEL spectra and pulse length will be used to measure the electron beam bunch length. The transverse properties of the electron beam will also be experimentally characterized.


*X.J. Wang, et al, Phys. Rev. E , 54, No.4, R3121 -3124 (1996).
**X.J. Wang and X.Y. Chang, Nuclear Instruments and Methods in Physics Research A 507, 310–313 (2003)

 
MO6RFP053 A Continuous Wave, Normal Conducting, L-Band PWT Photoelectron Gun cavity, gun, vacuum, simulation 479
 
  • D. Yu, Y. Luo
    DULY Research Inc., Rancho Palos Verdes, California
 
 

A Gallium Arsenide (GaAs) photocathode RF electron gun is useful if high polarization (>85%) and low emittance are required as, for example, in the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility. DULY Research is developing a normal-conducting, L-band photoelectron gun in an ultra high vacuum accelerating structure called the Plane-Wave-Transformer (PWT) integrated with an activated, strained-lattice GaAs photocathode, as a continuous wave polarized electron source. We compare two designs (1-cell and ½ cell) of an L-Band PWT photoelectron gun in this paper. This RF gun will simplify the CEBAF photoinjector design by replacing the direct current (DC) gun, buncher cavities and the capture section. The new compact design provides a stiffer beam that is less subject to space charge blowup. In addition, a higher field gradient at the photocathode would mitigate electron and ion backbombardment problems. Cooling for a CW PWT gun is challenging but manageable.

 
MO6RFP054 XPS Investigations on Cs2Te Photocathodes of FLASH and PITZ vacuum, survey, electron, photon 482
 
  • S. Lederer, S. Schreiber
    DESY, Hamburg
  • P.M. Michelato, L. Monaco, C. Pagani, D. Sertore
    INFN/LASA, Segrate (MI)
  • R. Ovsyannikov, M. Sperling, A. Vollmer
    BESSY GmbH, Berlin
  • F. Stephan
    DESY Zeuthen, Zeuthen
 
 

Caesium telluride (Cs2Te) photocathodes are used as sources for electron beams because of their high quantum efficiency (QE) and their ability to release high peak current electron bunches in a high gradient RF-gun. A rapid unexpected decrease of the initial QE, from 10% to values below 0.5% in only a few weeks of operation, was observed. In XPS measurements we identify a peak of Fluorine possibly originating from Teflon. After identification and removal of this specific contaminant, the life time of the cathodes increased to several months. In addition we have investigated the response of fully functional photocathodes to extensive usage, bad vacuum conditions, and oxidation by means of XPS measurements. The experiments - carried out at the ISISS and the PM3 beam lines at the synchrotron facility BESSY – compare the chemical composition and electronic structure of freshly prepared, contaminated, used, and oxidised Cs2Te cathodes.

 
MO6RFP055 Investigations on the Increased Lifetime of Photocathodes at FLASH and PITZ gun, laser, electron, vacuum 485
 
  • S. Lederer, S. Schreiber
    DESY, Hamburg
  • J.H. Han
    Diamond, Oxfordshire
  • M. Hänel, F. Stephan
    DESY Zeuthen, Zeuthen
  • P.M. Michelato, L. Monaco, C. Pagani, D. Sertore
    INFN/LASA, Segrate (MI)
 
 

Caesium telluride photocathodes are used as laser driven electron sources at FLASH and PITZ. FLASH is operated as user facility as well as for accelerator related studies and therefore has a constant and moderate usage of the cathodes. In contrary, PITZ is an injector R&D facility with a stronger usage of cathodes including gradients in the RF-gun of up to 60 MV/m. In the past, one concern of operating RF-guns with Cs2Te cathodes was the degradation of the quantum efficiency in a few weeks at FLASH and a couple of days at PITZ. Improved vacuum conditions and removing contaminants in both accelerators yielded an increased life time of several months. In this contribution we report on routinely performed QE measurements, investigations on the homogeneity of the electron emission, and dark current issues for both facilities.

 
MO6RFP056 Cryogenic Test of the Nb-Pb SRF Photoinjector Cavities cavity, niobium, SRF, plasma 488
 
  • J.K. Sekutowicz, A. Muhs
    DESY, Hamburg
  • P. Kneisel
    JLAB, Newport News, Virginia
  • R. Nietubyc
    The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
 
 

In this contribution, we report progress on the development of a hybrid lead/niobium superconducting RF (SRF) photoinjector. The goal of this effort is to build a Nb injector with the superconducting cathode made of lead, which demonstrated in the past superior quantum efficiency (QE) compared to Nb Three prototype hybrid devices, consisting of an all-niobium cavity with an arc-deposited spot of lead in the cathode region, have been constructed and tested. We present the cold test results of these cavities with and without lead.

 
MO6RFP057 Recent Electron Beam Measurements at PITZ with a New Photocathode Laser System laser, emittance, electron, gun 491
 
  • M. Krasilnikov, G. Asova, J.W. Bähr, C.H. Boulware, U. Gensch, H.-J. Grabosch, L. Hakobyan, M. Hänel, Ye. Ivanisenko, M.A. Khojoyan, M. Otevrel, B. Petrosyan, S. Riemann, S. Rimjaem, J. Rönsch-Schulenburg, A. Shapovalov, R. Spesyvtsev, L. Staykov, F. Stephan, G. Vashchenko
    DESY Zeuthen, Zeuthen
  • K. Flöttmann, S. Lederer, S. Schreiber
    DESY, Hamburg
  • G. Klemz, I. Will
    MBI, Berlin
  • D. Richter
    BESSY GmbH, Berlin
 
 

The Photo Injector Test facility at DESY, Zeuthen site, (PITZ*) aims to develop and optimize electron sources for frontiers linac based FELs such as FLASH and the European XFEL. A new laser system has been commissioned at PITZ in autumn 2008. It is capable to deliver laser pulses with challenging temporal shape: a flat-top profile with ~20 ps FWHM and rise and fall times of ≤2 ps. This laser system, being a significant step towards the European XFEL photo injector specifications, has been used in a 1.6-cell L-band rf gun with ~60MV/m electric field at the cathode to produce high brightness electron beams. A major part of the PITZ measurement program is the optimizing of the transverse phase space. Recent electron beam measurements at PITZ will be presented.


*for the PITZ team

 
MO6RFP058 Design of an Ultrafast Electron Diffraction System with an L-band Photocathode Gun electron, gun, laser, solenoid 494
 
  • J.H. Han
    Diamond, Oxfordshire
 
 

To investigate ultrafast dynamics of physical or chemical systems, ultrashort X-rays or electron beams may be used. Compared to X-rays, electron beams are less destructive to material and the scattering cross section is larger, however it is difficult to decrease the electron beam pulse length due to space charge forces. One way of overcoming this difficulty is by means of a photocathode RF gun, which allows the beam energy to be rapidly increased immediately after the electron emission from the photocathode, minimizing therefore the pulse lengthening due to space charge forces. For time-resolved observation of atomic processes electron beams shorter than 100 fs (fwhm) with small divergence are required. In this paper, a conceptual design of a gun system is proposed with beam parameters optimized for relativistic electron diffraction experiments.

 
MO6RFP059 Design of a Normal Conducting L-Band Photoinjector cavity, gun, emittance, simulation 497
 
  • J.H. Han
    Diamond, Oxfordshire
 
 

For the successful operation of an X-ray free electron laser the injector must be robust and able to provide a high quality beam. In this paper we present the design of a normal conducting L-band photoinjector which is based on the successful DESY/PITZ gun, but with improved cavity geometry. The result of beam dynamics simulations predicts that a beam with a normalized transverse emittance of less than 0.7 mm mrad at 1 nC can be produced. With an expected repetition rate of at least 1 kHz this gun meets the requirements of the first stage injector for the UK's New Light Source project.

 
MO6RFP060 Numerical Study of the RF Heating of an L-Band Gun cavity, gun, electron, simulation 500
 
  • J.H. Han, H.C. Huang
    Diamond, Oxfordshire
 
 

To precisely control the electron beam parameters from a photocathode RF gun, the RF field distribution during real RF operation must be known. During RF operation, the RF field induces local RF heating on the cavity surface. This non-uniform temperature distribution may deform the cavity and affect the output beam parameters. Here, we model a copper RF gun cavity and calculate the temperature distribution and the stress over the cavity surface. Then, the beam parameter change caused by the cavity deformation is simulated.

 
MO6RFP062 Microbunching Studies for SPARX Photoinjector bunching, space-charge, linac, FEL 506
 
  • C. Ronsivalle
    ENEA C.R. Frascati, Frascati (Roma)
  • M. Ferrario, C. Vaccarezza
    INFN/LNF, Frascati (Roma)
  • M. Migliorati
    Rome University La Sapienza, Roma
  • M. Venturini
    LBNL, Berkeley, California
 
 

The SPARX X-FEL accelerator will be the first FEL facility to operate with a hybrid (RF plus magnetic chicane) compression scheme. Numerical studies of propagation of beam density modulations stemming from photogun laser, through the photoinjector operating under velocity bunching conditions have been carried out. A semi-analytical model for the linear gain in a RF compressor is also being developed and some preliminary results are presented.

 
MO6RFP063 First Results from Commissioning of the PHIN Photo Injector for CTF3 laser, gun, emittance, electron 509
 
  • M. Petrarca, H.-H. Braun, N. Champault, E. Chevallay, R. Corsini, A.E. Dabrowski, M. Divall Csatari, S. Döbert, K. Elsener, V. Fedosseev, G. Geschonke, R. Losito, A. Masi, O. Mete, L. Rinolfi
    CERN, Geneva
  • G. Bienvenu, M. Joré, B.M. Mercier, C. Prevost, R. Roux
    LAL, Orsay
  • C. Vicario
    INFN/LNF, Frascati (Roma)
 
 

Installation of the new photo-injector for the CTF3 drive beam (PHIN) has been completed on a stand-alone test bench. The photo-injector operates with a 2.5 cell RF gun at 3 GHz, using a Cs2Te photocathode illuminated by a UV laser beam. The test bench is equipped with different beam monitoring devices as well as a 90-degree spectrometer. A grid of 200 micrometer wide slits can be inserted for emittance measurements. The laser used to trigger the photo-emission process is a Nd:YLF system consisting of an oscillator and a preamplifier operating at 1.5 GHz and two powerful amplifier stages. The infrared radiation produced is frequency quadrupled in two stages to obtain the UV. A Pockels cell allows adjusting the length of the pulse train between 50 nanoseconds and 50 microseconds. The nominal train length for CTF3 is 1.272 microseconds (1908 bunches). The first electron beam in PHIN was produced in November 2008. In this paper, results concerning the operation of the laser system and measurements performed to characterize the electron beam are presented.

 
MO6RFP065 Simulations of Mode Separated RF Photo Cathode Gun gun, emittance, laser, linac 515
 
  • A. Deshpande
    Sokendai, Ibaraki
  • S. Araki, M.K. Fukuda, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • K. Sakaue, M. Washio
    RISE, Tokyo
  • N. Sasao
    Kyoto University, Kyoto
 
 

At Accelerator Test Facility (ATF), we have developed and successfully used RF Photocathode gun as the source of electrons. We have also used a similar gun in the Laser Undulator Compact X-ray source facility (LUCX), KEK (High Energy Accelerator Research Organization) for performing experiments to generate X-rays by inverse Compton scattering. Both the existing guns have mode separation of 4 MHz. We designed a new RF Gun with high mode separation of around 9 MHz and high Q value to achieve a low emittance beam of good quality. We are also modifying the power delivery scheme to the accelerator at LUCX to achieve the acceleration of 200 nC in 100 bunches with low emittance. This will help to increase the intensity of X-rays by the inverse Compton scattering.

 
MO6RFP067 Beam Dynamics Simulation for the Compact ERL Injector emittance, space-charge, cavity, simulation 521
 
  • T. Miyajima, Y. Honda, Y. Kobayashi, T.M. Mitsuhashi, T. Muto, S. Sakanaka, M. Shimada
    KEK, Ibaraki
  • R. Hajima
    JAEA/ERL, Ibaraki
 
 

The compact ERL, cERL, is a project to test an energy recovery linac (ERL) with 60 MeV and 100 mA electron beam to generate synchrotron radiation with smaller emittance and shorter pulse length. The design work of the cERL injector has been carried out using a space charge simulation code. The injector consists of 500 kV photo cathode DC gun, two solenoid magnets, buncher cavity, three super conducting RF cavities and merger section to return pass. It generates an electron beam with -77 pC bunch charge and 1.3 GHz repetition rate. Our target value of emittance is less than 1 mm mrad with the bunch length of 1 mm at the exit of the injector. The parameter optimization of the injector using the multi objected method has been carried out to obtain the minimum emittance. The simulation results will be presented in detail.

 
MO6RFP069 A Study of Lifetime of GaAs Photocathode for High Brightness Electron Source laser, electron, vacuum, brightness 527
 
  • C. Shonaka, H. Higaki, K. Ito, D. Kubo, M. Kuriki, H. Okamoto
    HU/AdSM, Higashi-Hiroshima
  • T. Konomi, T. Nakanishi, S. Okumi, M. Yamamoto
    Nagoya University, Nagoya
 
 

High brightness electron source is a key technology for future projects based on advanced accelerators. Although GaAs photo-cathode is very attractive because it can generate highly polarized and extremely high brightness electron beam, the limited operational life time is a technical issue. In Hiroshima University, a photo-cathode test bench is implemented for various studies of GaAs photo-cathode. Super high vacuum, 9E-9Pa, was achieved and the cathode was successfully activated by processes of heat cleaning technique and the alternate evaporation of Cs and oxygen. The quantum efficiency and its lifetime were investigated as a function of cathode temperature, simulating temperature rise by the high power cathode drive laser. Wavelength dependence was also investigated.

 
MO6RFP072 On-Line Diagnostic during Cs2Te Photocathodes Formation diagnostics, photon, monitoring, gun 536
 
  • L. Monaco, P.M. Michelato, C. Pagani, D. Sertore
    INFN/LASA, Segrate (MI)
 
 

Funding: This work has partly been supported by the European Community, Contract Number RII3-CT-2004-506008.


Since ‘90s our laboratory is in charge of producing Cs2Te photocathodes employed as laser driven electron sources in the high brightness photoinjectors of the FLASH and PITZ facilities. The production recipe has been developed and standardized during years, fulfilling the requests for photocathode operation in the photoinjectors. Nevertheless, the growing process of the film is still not totally understood, mainly respect to the final material properties. In this paper, reflectivity and spectral response measurements, at different wavelengths, measured during the photocathode growth are presented and compared with the corresponding photocurrent behavior. The new information, together with results obtained with standard diagnostic tools, will help to improve the understanding of the growing process, of the compounds formation with different Cs/Te ratio and of the reproducibility of the Cs2Te film structure.

 
MO6RFP073 Drive Laser System for the SPARC Photoinjector laser, electron, FEL, brightness 539
 
  • C. Vicario, D. Filippetto, G. Gatti, A. Ghigo
    INFN/LNF, Frascati (Roma)
 
 

In this paper we report the status of the SPARC photocathode drive laser system. In the high brightness photoinjector the properties of the electron beam are directly related to the drive laser features. In fact the 3-D distribution of the electron beam and the time of emission are determined by the incoming laser pulse. The SPARC laser is a 10 Hz frequency-tripled TW-class Ti:Sa commercial system. A dedicated activity on the shape of the laser pulse has been performed in order to produce high energy UV flat top and multi-peaks time profile. To achieve the required flat top shape we perform a manipulation of the laser spectrum at the fundamental wavelength and directly at the third harmonic. The production of multi peaks laser pulse have been studied and tested. Finally we present the key laser performances recorded for the SPARC FEL experiment.

 
MO6RFP074 Design and Fabrication of a 500-kV Photocathode DC Gun for ERL Light Sources gun, vacuum, high-voltage, electron 542
 
  • R. Hajima
    JAEA/FEL, Ibaraki-ken
  • Y. Honda, T. Miyajima, T. Muto, M. Yamamoto
    KEK, Ibaraki
  • H. Iijima, R. Nagai, N. Nishimori
    JAEA/ERL, Ibaraki
  • M. Kuriki
    HU/AdSM, Higashi-Hiroshima
  • T. Nakanishi, S. Okumi
    Nagoya University, Nagoya
 
 

A 500-kV, 10-mA photocathode DC gun has been designed and is now under fabrication by the collaboration efforts of JAEA, KEK, Hiroshima Univ. and Nagoya Univ. The Cockcroft-Walton generator and the ceramic insulator are installed upright in the SF6 tank. We have adopted a multiple-stacked cylindrical ceramic insulator, because this type of ceramic insulator has shown good stability and robustness at the 200-kV Nagoya polarized gun and the 250-kV JAEA FEL gun. All the vacuum chambers are made of titanium alloy with very low out-gassing. The Cockcroft-Walton generator, the ceramic insulator, the vacuum chambers will be fabricated by April 2009 and a high-voltage test will be started soon later. Up-to-date status of the gun development will be presented in detail.

 
MO6RFP075 Development of a 250-kV Photo-Cathode Electron Gun for the ERL Light Sources at JAEA emittance, gun, electron, laser 545
 
  • R. Nagai, R. Hajima, H. Iijima, N. Nishimori
    JAEA/ERL, Ibaraki
  • Y. Honda, T. Miyajima, T. Muto
    KEK, Ibaraki
 
 

A 250-kV, 50-mA electron gun has been developed at JAEA for establishing fundamental technologies to generate and evaluate a ultra-small emittance beam, which is required for future ERLs such as a coherent X-ray source and a high-flux gamma-ray source. The gun has been assembled and the first photo-current was obtained from a cathode of NEA-GaAs. Apparatuses for beam measurements has been installed. We plan to measure the transverse emittance by a double-slit configuration and the temporal profile with a deflecting cavity.

 
MO6RFP077 Status of the LBNL Normal-Conducting CW VHF Photo-Injector cavity, gun, emittance, laser 551
 
  • F. Sannibale, K.M. Baptiste, J.N. Corlett, T.M. Huang, S. Kwiatkowski, D. Li, J. Qiang, J.W. Staples, R.P. Wells, L. Yang, A. Zholents
    LBNL, Berkeley, California
  • J.W. McKenzie
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
 
 

Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231


A high-brightness high-repetition rate photo-injector based on a normal conducting 187 MHz RF cavity design capable of CW operation is under construction at the Lawrence Berkeley National Laboratory. A cathode field of ~20 MV/m accelerates electron bunches to 750 keV with peak current, energy spread and transverse emittance suitable for FEL and ERL applications. A vacuum load-lock mechanism is included and a 10 picoTorr range vacuum capability allows most types of photocathodes to operate at a MHz repetition rate with present laser technology. The status of the project is presented.

 
MO6RFP078 Upgrades to the Injector Cathode and Supporting Structure of the DARHT Second Axis Accelerator alignment, vacuum, induction, electron 554
 
  • R.R. Mitchell, B.A. Gardner, T. Ilg
    LANL, Los Alamos, New Mexico
  • M. Leitner
    LBNL, Berkeley, California
  • B.A. Prichard
    SAIC, Los Alamos, New Mexico
 
 

Funding: National Nuclear Security Administration of the US Department of Energy


The Dual-Axis Radiographic Hydrodynamic Test Facility (DARHT) at Los Alamos National Laboratory (LANL) consists of two linear induction accelerators oriented at right angles to each other. The DARHT First Axis has been successfully operated since 1999 and produces a 60 ns pulse with beam energy of 20 MeV and beam current of 1.9 kA. The DARHT Second Axis was successfully commissioned in May 2008 and produces a 1600 ns pulse with beam energy of 17.5 MeV and beam current of 2.1 kA. The Second Axis Injector uses a 16.5 cm diameter thermionic cathode with a 10 A/cm2 required current density to emit electrons into the accelerator. During the early Second Axis commissioning activities in 2006, deficiencies in the DARHT Second Axis Injector were found that prevented the injector cathode from meeting the required 10 A/cm2 current density. A comprehensive campaign was initiated to solve the injector cathode performance issues. This paper describes the deficiencies found and the solutions used to enable the DARHT Second Axis Injector to meet its requirements.

 
MO6RFP082 Theory and Modeling of Electron Emission from Cesiated Semiconductor Surfaces electron, laser, scattering, emittance 566
 
  • K. L. Jensen, J.L. Shaw, J.E. Yater
    NRL, Washington, DC
  • D.W. Feldman, E.J. Montgomery, P.G. O'Shea, P.Z. Pan
    UMD, College Park, Maryland
  • N.A. Moody
    LANL, Los Alamos, New Mexico
  • J.J. Petillo
    SAIC, Burlington, Massachusetts
 
 

Funding: We gratefully acknowledge funding provided by the Joint Technology Office and the Office of Naval Research


Laser switched photocathodes are now the electron source of choice for short wavelength Free Electron Lasers. The photocathode requirements are profound: ideally, capabilities such as high peak and average current, high quantum efficiency (QE) in the visible, long lifetime in an rf injector and the ability to be repaired in situ are desired. We are pursuing cathodes with self-rejuvenating surfaces based on cesium dispenser cathode technology*,**, in which the physics of recesiation, evaporation, diffusion, and evolution of the surface coating and the QE are the metrics of performance. Here, we present predictive theoretical models of surface evolution and QE in a manner appropriate for inclusion in beam simulation codes, wherein emission non-uniformity and dark current affect emittance, beam halo, and dynamic evolution of bunched electron beams***. The emission models focus on bulk transport issues (including scattering processes) and surface conditions (including diffusion in the presence of random, non-uniform sub-monolayer coverage), and relate these factors to recent experimental characterizations of the surface evolution.


*Jensen, et al., JAP{10}2, 074902 ; Moody, et al., APL90, 114108.
**E. Montgomery, et al., (this conference)
***Petillo, et al., Proc IEEE PAC (2007); Jensen, et al., PRST-AB 11, 081001.

 
MO6RFP083 Fabrication and Recesiation of Alkali Antimonide Photocathodes FEL, vacuum 567
 
  • E.J. Montgomery, D.W. Feldman, P.G. O'Shea, P.Z. Pan
    UMD, College Park, Maryland
  • K. L. Jensen
    NRL, Washington, DC
  • N.A. Moody
    LANL, Los Alamos, New Mexico
 
 

Funding: This project is funded by the Joint Technology Office and the Office of Naval Research.


High performance FELs require photocathodes with quantum efficiencies of several percent at green wavelengths, kHr lifetime, kA/cm2 peak and A/cm2 average current, and ps response. Such cathodes are challenged to maintain requisite high quantum efficiency while in harsh accelerator vacuum conditions. Delicate surface coatings are often cesium-based, and therefore are reactive with contaminant gases. The dispenser photocathode architecture resupplies the cesium coating from a subsurface reservoir through a porous substrate, thereby extending lifetime*. Recesiation has been shown to rejuvenate Cs:Ag cathodes from O2, CO2, and N2O contamination**, and theory of dispenser photocathodes is advancing***. We here investigate the fabrication, contamination, and external recesiation of alkali antimonides with high quantum efficiency, in support of the dispenser photocathode design.


*Moody et al., APL90, 114108.
**Montgomery et al., Proc. AACW 2008 (submitted for publication).
***K. Jensen et al., (this conference).

 
MO6RFP086 Design, Construction and Operation of the Dutch RF-Photoguns cavity, electron, resonance, plasma 569
 
  • S.B. van der Geer
    Pulsar Physics, Eindhoven
  • G.J.H. Brussaard, O.J. Luiten, W.P.E.M. Op 't Root, M.J. de Loos, W. van Dijk, W.J. van Hemmen, S.B. van der Geer
    TUE, Eindhoven
  • W. Knulst, M.J.W. Vermeulen
    Delft University of Technology, Opto-electronic Section, Delft
 
 

Three different S-band rf-photoguns have been constructed by Eindhoven University of Technology in the Netherlands: A 1.5-cell, a 100 Hz 1.6-cell, and a 2.6-cell. They share a design concept that differs from the ‘standard’ BNL-gun in many aspects: Individual cells are clamped and not brazed saving valuable manufacturing time and allowing damaged parts to be replaced individually. The inner geometry employs axial incoupling, inspired by DESY, to eliminate any non-cylindrically symmetric modes. Elliptical irises, identical to a 2.6-cell design of Strathclyde University, reduce the maximum field on the irises and thereby reduce electrical breakdown problems. The manufacturing process uses single-point diamond turning based on a micrometer-precise design. The overall precision is such that the clamped cavities are spot-on resonance and have near-perfect field balance without the need for any post-production tuning. Operational performance of the three Dutch rf-photoguns will be presented.

 
MO6RFP087 Thermionic Cathode-Grid Assembly Simulations for RF Guns emittance, simulation, gun, cavity 572
 
  • V. Volkov, E. Kenzhbulatov, S.A. Krutikhin, G.Y. Kurkin, V.M. Petrov, E. Rotov, N. Vinokurov
    BINP SB RAS, Novosibirsk
 
 

The projected electron RF gun of Novosibirsk Microtron-Recuperator injector employs an industrial thermionic cathode grid assembly with 0.08 mm gap that usually used in metal-ceramic RF tubes. Three-dimensional (3D)computer simulations have been performed that use the mesh refinement capability of the both Microwave Studio and 2D SAM codes to examine the full region of the real cathode grid assembly in static fields in order to illustrate the beam quality that can result from such a gridded structure. These simulations have been found to reproduce the beam current behaviors versus of applied potentials that are observed experimentally. Based on it ASTRA RF beam simulations also predict a complicated time-dependent response to the waveform applied to the grid during the current turn-on, calculation of the dissipated power by electrons at the grid, and particle tracking downstream of the grid into RF gun cavity and farther on. These simulations may be representative in other sources, such as some L-band RF injectors for industrial applications.

 
MO6RFP088 Operating a Tungsten Dispenser Cathode in Photo-Emission Mode laser, gun, linac, electron 575
 
  • S.M. Gierman, P.R. Bolton, W.J. Corbett, G.R. Hays, F. King, R.E. Kirby, J.F. Schmerge, J.J. Sebek
    SLAC, Menlo Park, California
 
 

Funding: Supported by US DOE under contract DE-AC03-76SF00515.


The Stanford Synchrotron Radiation Laboratory operates a thermionic radio-frequency gun as part of its injector for the SPEAR 3 storage ring. In order to generate the high bunch charge required for top-off injection, it may be advantageous to operate the thermionic cathode as a photo-emitter. In this note we report on measurements of the wavelength dependence of the quantum efficiency of a tungsten dispenser cathode in a low-field environment, and on high-power tests of the injector in photoemission mode.

 
MO6RFP091 A Laser-Cooled Electron Source for Ultrafast Electron Diffraction electron, laser, simulation, brightness 580
 
  • S.B. van der Geer, B. Fleskens, O.J. Luiten, M.P. Reijnders, G. Taban, E.J.D. Vredenbregt
    TUE, Eindhoven
  • S.B. van der Geer
    Pulsar Physics, Eindhoven
 
 

Ultrafast electron diffraction (UED) enables single-shot studies of structural dynamics at atomic length and time scales, i.e. 0.1 nm and 0.1 ps. At present UED experiments are based on femtosecond laser photoemission from solid state cathodes. We propose a new type of electron source, based on near-threshold photoionization of a laser-cooled and trapped atomic gas. The electron temperature of these sources can be as low as 10 K. This implies an increase in brightness by orders of magnitude and enables single-shot studies of, e.g., biomolecular samples. In this contribution we numerically investigate the performance of a laser-cooled electron source by GPT tracking simulations with realistic fields and all pairwise Coulomb interactions.

 
MO6RFP094 Commissioning of Na2KSb Photocathode RF Gun in S-Band Linac at the University of Tokyo gun, laser, vacuum, electron 587
 
  • K. Miyoshi, Y. Muroya, A. Sakumi, T. Ueda, M. Uesaka
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken
  • K. Kambe
    UTNL, Ibaraki
 
 

Multi-Alkali photocathode has the good possibility as a electron source which has high quantum efficiency and low workfunction. However the surface of the cathode is sensitive over the electric field of 100[MV/m] in a RFgun, the amount of dark current is not negligible. In order to reduce such a dark current, we consider the valance of the electric field between half-cell and full-cell of BNL-IV RF gun by numerical simulation using GPT code. In this work we will show that high quality electron beam can be transported on the condition that appled electric field in half and full cell is about 50[MV/m] and 150[MV/m] respectively.

 
MO6RFP097 Longitudinal Beam Dynamics of the Photoinjector Blowout Regime cavity, electron, space-charge, laser 596
 
  • J.T. Moody, M.S. Gutierrez, P. Musumeci, C.M. Scoby
    UCLA, Los Angeles, California
 
 

Funding: Office of Naval Research (US) Grant No. N000140711174


Longitudinal beam dynamics of the photoinjector "blowout" regime are investigated. A two beamlet macroparticle approach is first used to investigate the effects of S-Band RF photogun fields on a picosecond time scale. The beams' longitudinal phase spaces (LPS) are measured via an X-band RF deflecting cavity and dipole spectrometer. Lastly, the LPS of a single subpicosecond beam is investigated as a function of initial charge density at the cathode and compared to simulation.

 
MO6RFP098 Time Resolved Relativistic Electron Diffraction electron, laser, emittance, feedback 599
 
  • P. Musumeci, M.S. Gutierrez, J.T. Moody, C.M. Scoby
    UCLA, Los Angeles, California
 
 

We report on the use of a ultrashort high brigthness relativistic beam from the UCLA Pegasus laboratory RF photoinjector source for probing matter transformation at the atomic scale with sub-100 fs time resolution. The high accelerating gradient and the relativistic electron energy allow to pack more than 107 electrons in less than 100 fs bunch length, enabling the study of irreversible ultrafast phenomena by single-shot diffraction patterns. The experimental setup, and the initial results from the first ever relativistic electron diffraction time-resolved study will be discussed.

 
MO6RFP099 A Single Bunch Electron Gun for the ANKA Injector gun, emittance, electron, simulation 602
 
  • A. Hofmann, M. Fitterer, M. Klein, A.-S. Müller, K.G. Sonnad
    KIT, Karlsruhe
  • G. Blokesch
    PPT, Dortmund
  • E. Huttel, N.J. Smale
    FZK, Karlsruhe
  • S. Marsching, T. Weis
    DELTA, Dortmund
  • C. Piel
    ACCEL, Bergisch Gladbach
  • R. Weigel
    Max-Planck Institute for Metal Research, Stuttgart
 
 

Funding: This work has been supported by the Initiative and Networking Fund of the Helmholtz Association under contract number VH-NG-320.


The microtron of the ANKA injector is presently equipped with a diode- type electron gun, which produces long pulses. A new thermionic DC triode-type electron gun has been ordered and foreseen for installation in the ANKA injector. The new gun allows single bunch as well as long pulse operation, thus offering the possibility to study beam properties in single bunch operation. This is particularly of interest for the investigation of the short bunch dynamics in the generation of coherent THz radiation. Furthermore, the new gun will make time resolved measurement possible. Simulations of the gun-to-microtron transport with special emphasis on the emittance evolution e.g. due to space charge have been done. Measurements of the gun performance are presently underway and are summarised in this paper.

 
MO6RFP101 Development of High Brightness Injector at NSRL gun, emittance, laser, solenoid 605
 
  • S.C. Zhang, D.H. He, Q.K. Jia, Z. Jin, W. Li, S. Lu, L. Shang, B. Sun, Y. Wang, C. Yao, R. Zhuo
    USTC/NSRL, Hefei, Anhui
 
 

A photocathode injector system is developing at NSRL. A BNL type S-band photocathode RF gun has been built. The emittance will be compensated by a Solenoid. The driving laser is a high-Q product. It will be reformed into uniform distribution in the transverse distribution, but will not in the longitudinal direction. The whole system will be tested soon.

 
MO6RFP102 Present Status of a Multi-Bunch Electron Beam Linac Based on Cs-Te Photo-Cathode RF-Gun at Waseda University laser, electron, gun, cavity 608
 
  • T. Suzuki, T. Fujino, Y. Kato, A. Masuda, A. Murata, K. Sakaue, M. Washio
    RISE, Tokyo
  • H. Hayano, T. Takatomi, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • S. Kashiwagi
    ISIR, Osaka
  • R. Kuroda
    AIST, Tsukuba, Ibaraki
 
 

At Waseda University, we have been developing a high quality electron source based on photo-cathode rf-gun and its application experiments. To produce a high current electron beam, we installed a Cs-Te cathode which has higher quantum efficiency and improved the structure of the rf cavity. By adopting a Cs-Te cathode, it is expected that the production of the higher charged single bunch electron beam with a low emittance can be achieved. Moreover, the generation of high quality multi-bunch electron beam is also expected to be possible due to the high quantum efficiency of Cs-Te. For understanding of a Cs-Te cathode and higher quantum efficiency operation, we have performed the fundamental studies by single bunch beam. On the other hand, we have also developed a multi-pulse UV laser for generating the multi-bunch electron beam. Our laser system is composed by all-solid-state Nd:YLF for the stable operation, and the specification of this laser is expected to generate a 100bunch/train with the bunch charge of 800pC/bunch. In this conference, the experimental results of Cs-Te and new laser system and the recent progress of multi-bunch electron beam generation will be reported.

 
TU2GRC03 First Observation of an Electron Beam Emitted from a Diamond Amplified Cathode electron, shielding, high-voltage, focusing 691
 
  • X. Chang, I. Ben-Zvi, A. Burrill, J. Kewisch, E.M. Muller, T. Rao, J. Smedley, E. Wang, Y.C. Wang, Q. Wu
    BNL, Upton, Long Island, New York
 
 

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.


We observed, for the first time, the emission of an electron beam from a hydrogenated diamond in the emission mode on a phosphor screen. Our experimental device is based on the following concept: primary electrons of a few keV energy generate a large number of secondary electron-hole pairs in a diamond. The secondary electrons are transmitted to the opposite face of the diamond, which is hydrogenated, and emitted from its negative-electron-affinity (NEA) surface. Under our present conditions, the maximum emission gain of the primary electron is about 40, and the bunch charge is 50pC/0.5mm2. Our achievement led to new understanding of the hydrogenated surface of the diamond. We propose an electron-trapping mechanism near the hydrogenated surface. The probability of electron trapping in our tests is less than 70%. The hydrogenated diamond was demonstrated to be extremely robust. After exposure to air for days, the sample exhibited no observable degradation in emission.

 

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TU4RAI02 Development of a 10 MW Sheet Beam Klystron for the ILC cavity, klystron, gun, simulation 762
 
  • D.W. Sprehn, A.A. Haase, A. Jensen, E.N. Jongewaard, D.W. Martin
    SLAC, Menlo Park, California
  • A.T. Burke
    SAIC, Billerica, Massachusetts
 
 

Funding: Work supported by Department of Energy contract DE-AC02-76SF00515


SLAC is developing a 10 MW, 5 Hz, 1.6 ms, L-band (1.3 GHz) Sheet-Beam Klystron as a less expensive and more compact alternative to the ILC baseline Multiple-Beam Klystron. The Klystron is intended as a plug-compatible device of the same beam current and operating voltage as existing Multiple-Beam Klystrons. At this time, a beam tester has been constructed and currently is in test. The beam tester includes an intercepting cup for making beam quality measurements of the 130 A, 40-to-1 aspect ratio beam. Measurements will be made of the electrostatic beam and of the beam after transporting through a drift tube and magnetic focusing system. General theory of operation, design trade-offs, and manufacturing considerations of both the beam tester and klystron will be discussed.

 

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Slides

 
TU4RAC03 Modeling and Design of High-Power Inductive Output Tubes simulation, cavity, electron, gun 767
 
  • E.L. Wright, K.T. Nguyen
    Beam-Wave Research, Inc., Union City
  • I.A. Chernyavskiy, J.J. Petillo
    SAIC, McLean
  • S.J. Cooke, B. Levush, J.A. Pasour
    NRL, Washington, DC
  • J.F. DeFord, B. Held
    STAAR/AWR Corporation, Mequon
 
 

Funding: Research funded by the Office of Naval Research and Naval Research Laboratory.


The accelerator community is making the transition to IOT technology for a number of high-power UHF and L-band applications as a result their inherent benefits. Scientists, funded by the Office of Naval Research and Naval Research Laboratory, are investigating the physics of the beam-wave interaction of the IOT. The time-domain electrostatic PIC code MICHELLE, in conjunction with the Analyst® suite of electromagnetic codes, were used to model the cathode-grid-anode structure that comprise the input cavity. Our investigation has led to the discovery of a delay mechanism responsible for intra-bunch charge formation, as evidenced by IOT X-ray generation with energies significantly higher than the cathode accelerating potential, increasing with RF output power. Time-domain PIC results of this effect will be shown. We will also present simulation results of the large-signal beam wave interaction in the output cavity using the code TESLA. Examples of single beam and multiple-beam IOTs will also be shown.

 

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TU5PFP012 Statistical Modeling of DC Sparks site, simulation, vacuum, cavity 833
 
  • Y.I. Levinsen, S. Calatroni, A. Descoeudres, M. Taborelli, W. Wuensch
    CERN, Geneva
 
 

The understanding of electrical breakdowns has a critical role in the design of the RF accelerating cavities for the CLIC linear collider. In this context a new statistical model of the conditioning process and breakdown rate evolution is presented for a DC spark system with tip-plane electrode geometry charged from a capacitance. The approach requires a small amount of assumptions, but can still make several interesting predictions. Electrode gap distance dependence on the saturated breakdown field and spitfest (grouped breakdowns) are among the phenomena that could be explained from this simple model.

 
TU5PFP013 Quantitative Outgassing Studies in DC Electrical Breakdown vacuum, cavity, ion, simulation 836
 
  • Y.I. Levinsen, S. Calatroni, A. Descoeudres, M. Taborelli, W. Wuensch
    CERN, Geneva
 
 

Electrical breakdown in the accelerating cavities set a potential limit to the performance of the CLIC linear collider. Vacuum degradation and beam instability are possible outcomes from a breakdown if too much gas is released from the cavity surface. Quantitative data of gas release are provided for copper electrodes (milled Cu-OFE, as-received and heat-treated), and molybdenum electrodes. These data are produced from a controlled DC spark environment with capacitance charged anode at fixed energy.

 
TU5PFP019 Phase and Frequency Locked Magnetrons for SRF Sources feedback, solenoid, injection, controls 852
 
  • M.L. Neubauer, R.P. Johnson
    Muons, Inc, Batavia
  • A. Moretti, M. Popovic
    Fermilab, Batavia
 
 

Funding: Supported in part by USDOE Contract. DE-AC05-84-ER-40150 and by FRA DOE contract number DE-AC02-07CH11359


Magnetrons are low-cost highly-efficient microwave sources, but they have several limitations, primarily centered about the phase and frequency stability of their output. When the stability requirements are low, such as for medical accelerators or kitchen ovens, magnetrons are the very efficient power source of choice. But for high energy accelerators, because of the need for frequency and phase stability–-proton accelerators need 1-2 degrees source phase stability, and electron accelerators need .1-.2 degrees of phase stability–-they have rarely been used. We describe a novel variable frequency cavity technique which will be utilized to phase and frequency lock magnetrons.

 
TU5PFP093 Low Beam Voltage, 10 MW, L-Band Cluster Klystron cavity, gun, klystron, simulation 1051
 
  • V.E. Teryaev
    BINP SB RAS, Novosibirsk
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT
  • S. Kazakov
    KEK, Ibaraki
  • V.P. Yakovlev
    Fermilab, Batavia
 
 

Funding: Sponsored in part by US Department of Energy, Office of High Energy Physics.


Conceptual design of a multi-beam klystron (MBK) for ILC and Project X application is presented. The chief distinction between the MBK design and existing 10-MW MBK’s is the low operating voltage of 60 kV. There are at least four compelling reasons that justify development of a low-voltage MBK, namely (i) no pulse transformer would be required; (ii) no oil tank would be required for the tube socket; (iii) modulator would be a compact 60-kV IGBT switching circuit. The proposed klystron consists of four clusters that contain six beams each. The tube has common input and output cavities for all 24 beams, and individual gain cavities for each cluster. A closely related optional configuration for a 10 MW tube would involve a design having four totally independent cavity clusters and four 2.5 MW output ports, all within a common magnetic circuit. This option has appeal because the output waveguides would not require a controlled atmosphere and because it would be easier to achieve phase and amplitude stability as required in individual SC cavities.

 
TU5PFP095 The MICE RF System cavity, LLRF, power-supply, controls 1057
 
  • A.J. Moss, J.F. Orrett
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
 
 

The Muon Ionisation Cooling Experiment (MICE) at the Rutherford Appleton Laboratory uses normal conducting copper cavities to re-accelerate a muon beam after it has been retarded by liquid hydrogen absorbers. Each cavity operates at 200MHz and requires 1MW of RF power in a 1ms pulse at a repetition rate of 1Hz. In order to provide this power, a Thales TH116 triode, driven by a Burle 4616 tetrode is used, with each amplifier chain providing ~2.5MW. This power is then split between 2 cavities. The complete MICE RF system is described, including details of the low level RF, the power amplifiers and the coaxial power distribution system. Testing of the amplifier chain, power supplies and low level RF is described.

 
TU5RFP064 Towards A Self Sustained Free Electron Laser Device cavity, FEL, radiation, electron 1232
 
  • E. Sabia, G. Dattoli, A. Dipace
    ENEA C.R. Frascati, Frascati (Roma)
 
 

We explore the possibility of using free-electron laser (FEL) triggered cathodes to produce high quality e-beams. We propose a scheme which foresees cathodes operating either as thermionic and photo-cathodes, which can be exploited in devices using the same e-beam to drive the laser and the cathode. We discuss different modes of operation, in particular we consider oscillator FELs, in which the light from higher order harmonics, generated in the oscillator cavity, is used to light the cathode. The dynamics of the system is explored along with the technical solutions, necessary for the stability of the system. The Master Oscillator Power Amplifier FEL scheme is explored too. The use of the same e-beam, driving the photocathode and the FEL, makes the system naturally free of any synchronization problem, arising when an external laser is used. The device is a kind of regenerative amplifier in which the growth of the optical power can be controlled by using a proper detuning or misalignment of the optical cavity. Specific examples are reported. The use of this technique for an ab-initio control the Coherent Radiation Synchrotron instability is finally discussed too.

 
TU5RFP083 Progress on the Commissioning of ALICE, the Energy Recovery Linac-Based Light Source at Daresbury Laboratory gun, radiation, linac, electron 1281
 
  • S.L. Smith, R. Bate, C.D. Beard, M.A. Bowler, R.K. Buckley, S.R. Buckley, J.A. Clarke, P.A. Corlett, M. Dufau, D.J. Dunning, B.D. Fell, P. Goudket, A.R. Goulden, S.A. Griffiths, J.D. Herbert, C. Hill, F. Jackson, S.P. Jamison, J.K. Jones, L.B. Jones, A. Kalinin, N. Marks, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, A.J. Moss, B.D. Muratori, J.F. Orrett, S.M. Pattalwar, P.J. Phillips, M.W. Poole, Y.M. Saveliev, D.J. Scott, B.J.A. Shepherd, R.J. Smith, N. Thompson, B. Todd, T.M. Weston, A.E. Wheelhouse, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • J.R. Alexander, P. Atkinson, N. Bliss, I. Burrows, G. Cox, P.A.D. Dickenson, A. Gallagher, K.D. Gleave, J.P. Hindley, B.G. Martlew, I.D. Mullacrane, A. Oates, P.D. Quinn, D.G. Stokes, J. Strachan, P.J. Warburton, C.J. White
    STFC/DL, Daresbury, Warrington, Cheshire
  • W.R. Flavell, E.A. Seddon
    UMAN, Manchester
  • F.G. Gabriel
    FZD, Dresden
  • C. Gerth
    DESY, Hamburg
  • F.E. Hannon, C. Hernandez-Garcia, K. Jordan, G. Neil
    JLAB, Newport News, Virginia
  • K. Harada
    KEK, Ibaraki
  • P. Harrison, D.J. Holder, G.M. Holder, P. Weightman
    The University of Liverpool, Liverpool
  • S.F. Hill, G. Priebe, R.V. Rotheroe, M. Surman
    STFC/DL/SRD, Daresbury, Warrington, Cheshire
  • G.J. Hirst, P.G. Huggard
    STFC/RAL, Chilton, Didcot, Oxon
  • P. vom Stein
    ACCEL, Bergisch Gladbach
 
 

ALICE (Accelerators and Lasers in Combined Experiments) is a 35 MeV energy recovery linac based light source. ALICE is being developed as an experimental test-bed for a broad suite of science and technology activities that make use of electron acceleration and ultra-short pulse laser techniques. This paper reports the progress made in accelerator commissioning and includes the results of measurement made on the commissioning beam. The steps taken to prepare the beam for short pulse operation as a driver for a Compton Back Scattered source and in preparation for the commissioning of the free electron laser are reported.

 
TU6PFP027 Improvement of Compact Pico-Second and Nano-Second Pulse Radiolysis Systems at Waseda University electron, gun, radiation, laser 1345
 
  • A. Fujita, Y. Hama, Y. Hosaka, T. Nomoto, K. Sakaue, M. Washio
    RISE, Tokyo
  • S. Kashiwagi
    ISIR, Osaka
  • R. Kuroda
    AIST, Tsukuba, Ibaraki
  • K. Ushida
    RIKEN, Saitama
 
 

A pulse radiolysis method is very useful in clarifying primary processes of radiation chemistry. At Waseda University, compact pico-second and nano-second pulse radiolysis systems have been developing. A pico-second system is based on pump-probe method. IR and UV pico-second laser pulses are generated from Nd:YLF mode-locked laser and used for generating of white light continuum as analyzing light and irradiating to photo-cathode RF gun, respectively. Recently, we have installed a new photo-cathode RF gun with Cs-Te cathode which has high quantum efficiency, so we have succeeded in improving optical density and S/N ratio of our pulse radiolysis system. We are now developing a new nano-second system which can get time profile with only one-shot and follow up wider time region than pico-second system. In the past, this system has been used He-Ne laser as analyzing light, but it can measure only 633nm. Instead of He-Ne laser, this system adopts Xe flush lamp which has broad spectrum as analyzing light. As system evaluation experiments, we tried to get time profile of some species. In this conference, present status and future plans of our pulse radiolysis systems will be reported.

 
TU6PFP084 A 15 MeV Accelerator Scheme Based on a DC Photo-Injector and a RF Superconducting Linac vacuum, simulation, electron, target 1488
 
  • D. Guilhem, J.-L. Lemaire
    CEA, Arpajon
 
 

A 15 MeV accelerator scheme based on a DC photo-injector and a RF superconducting linac has been proposed as a new facility for radiography applications. The design of a 15 MeV, 2 kA peak current, electron accelerator for the DEINOS project is presented The beam operating condition is a limited number of bunches up to twenty electron micro-pulses of 100 ps time duration and 200 nC bunch charge emitted at 352 MHz repetition rate from a Cs2Te photocathode and accelerated to 2.5 MeV in the DC diode before injection into a superconducting linac. A general description of the main accelerator components and the beam dynamics simulations are presented. The overall beam dynamics simulation process based on LANL POISSON-SUPERFISH and PARMELA codes and the results will be reviewed.

 
TU6PFP096 Cold-Cathode Kiloampere Electron Gun with Secondary Emission at Relativistic Voltage gun, electron, injection, high-voltage 1522
 
  • S.A. Cherenshchykov
    NSC/KIPT, Kharkov
 
 

Funding: The research was supported the STCU foundation in frame of the project 1968.


Magnetron Injection Gun with voltage up {10}00 kV and current more 1 kA was calculated, designed and manufactured. The gun was tested in nanosecond and microsecond operating modes. The application of nanosecond voltage pulses with amplitude up to 600 kV permitted to obtain the secondary-emission current up to 5 kA. The cathode testing in microsecond mode permitted to obtain beam pulse with amplitude up to 1.2 kA at voltage of 400 kV in magnetic field of 0.3 T. There were obtained beam traces on the copper plate. Traces had the form of rings with diameter of 125 mm and width of 5 mm. The secondary emission nature of the cathode current was established. The identification was held basing on considered features of the exciting and on the maintenance of the secondary emission current. However, there is the probability of the parasitic explosive emission at extremely high voltage values since 800 kV. The gun may be used for charge particle accelerators in injectors and RF power sources. Results of the work and prospects of the secondary emission gun development are discussed.

 
TU6RFP016 Klystron Cathode Heater Power Supply System Based on the High-Voltage Gap Transformer klystron, power-supply, resonance, high-voltage 1562
 
  • P.A. Bak, A.A. Korepanov, V.D. Zabrodin
    BINP SB RAS, Novosibirsk
  • V. Vogel
    DESY, Hamburg
 
 

Funding: This work was performed within the framework of the agreement between Deutsches Elektronen-Synchrotron (DESY, Hamburg) and BINP SB RAS (Russia, Novosibirsk), "Attachment N 18".


Power system for the klystron cathode heater power supply has been developed to transfer 800 Watts up to 130 kV potential based on the high-voltage gap transformer. Power transfer has been implemented resonant way on the frequency of 19.5 kHz using coupled LC-loops with further transformation to DC. Transformer coupling factor is of 0.58, high-voltage gap is 49 mm, and maximum calculated electric field intensity is 35 kV/cm. Primary winding is powered by the full bridge inverter using phase shifted pulse modulation. This inverter topology provides soft switching of the transistors in a wide range of power regulation (from 18 up to 800 Watts) without an auxiliary active resonant snubber circuits. High stability (0.3%) of the output power has been reached using proportional regulation in the feedback circuit. The achieved power conversion efficiency of inverter is more than 0.95 in the regulation range; efficiency of the whole power system is more than 0.88. The reliable operation of the power system is guaranteed on three types of klystrons (Toshiba E3736; Thales TH1801; CPI VKL8301). The work has been performed within the European XFEL project.

 
TU6RFP079 A High Voltage, High Rep-Rate, High Duty Factor Stacked Transformer Modulator gun, electron, proton, damping 1733
 
  • G.W. Saewert, H. Pfeffer
    Fermilab, Batavia
 
 

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.


A high voltage modulator has been built and installed at Fermi National Accelerator Laboratory for the purpose of driving the gun anode of the Tevatron Electron Lens (TEL). It produces a defined voltage for each of the 36 (anti)proton bunches. This modulator employs five transformers to produce high voltage at a high repetition rate and high duty factor. It is capable of outputting sustained complex waveforms having peak voltages over 6 kV and average periodic rates up to 450 kHz with voltage transitions occurring at 395 ns intervals. This paper describes key aspects of the hardware design and performance.

 
TU6RFP080 Cold Cathode Thyratron Based High-Voltage Kicker System for the Duke Accelerators: Performance and Improvements kicker, booster, injection, high-voltage 1736
 
  • V. Popov, S.F. Mikhailov, P.W. Wallace
    FEL/Duke University, Durham, North Carolina
  • O. Anchugov, Yu. Matveev, D.A. Shvedov
    BINP SB RAS, Novosibirsk
 
 

Funding: Supported by US DoE grant #DE-FG02-01ER41175


The Duke FEL/HIGS (Free electron laser/High Intensity Gamma-ray source) facility has recently undergone through a series of major upgrade. As a part of this upgrade, a kicker system was designed to provide reliable injection from the booster into the storage ring at any energy chosen from the range of 240 MeV to 1.2 GeV. Relatively new and not sufficiently studied switching device has been selected as a basic component to build a set of nanosecond resolution high-voltage generators. So called Pseudo-Spark Switch (PSS), also known as a cold cathode thyratron, has the same or slightly better jitter, reasonable range of switched high voltages and significantly lower heater power as compared to the traditional “hot” thyratrons. Despite of the fact that it requires more complicated triggering system, this device still seems very attractive as a driver for short pulse kickers. Almost three years of operation of the Duke FEL facility has revealed number of advantages and challenges related to the thyratrons of this type. In this paper we depict design features of the kicker system, discuss some accomplished improvements and summarize our three year experience.

 
TU6RFP088 Design of Electron Gun System for the PLS-II Linear Accelerator gun, electron, high-voltage, simulation 1751
 
  • Y.G. Son, K.R. Kim, S.H. Nam, S.J. Park
    PAL, Pohang, Kyungbuk
  • T. Asaka
    JASRI/SPring-8, Hyogo-ken
 
 

Funding: This work was supported by the MEST (Ministry of Education, Science and Technology) and the POSCO (POhang iron and Steel making COmpany) in Korea.


The PLS-II, the major upgrade program of the PLS (Pohang Light Source, a 2.5-GeV 3rd generation light source), is planned at the Pohang Accelerator Laboratory. The PLS 2.5-GeV linear accelerator, being the full-energy injector for the PLS storage ring, should be upgraded to provide the beam energy of 3 GeV. For the PLS-II linac, we are going to establish a dual electron gun system in which two guns will be on the accelerator beamline with a bending magnet enabling immediate switching of guns. The dual gun system is expected to achieve high reliability for the top-up injection to the PLS-II storage ring. Also the gun will be upgraded to provide the beam energy of 200 keV and a pulse high-voltage modulator will be constructed. Fifteen-section PFNs will be connected in series to make final impedance of approximately 17.3 ohm. A new modulator applying the inverter technology will be used to charge the PFN and obtain more stable charging performances. In this article the authours would like to report on the design status of the accelerator beamline and inverter modulator for the dual gun system.

 
TU6RFP095 Towards a PEBB-Based Design Approach for a Marx-Topology ILC Klystron Modulator klystron, high-voltage, power-supply 1769
 
  • K.J.P. Macken, T.G. Beukers, C. Burkhart, M.A. Kemp, M.N. Nguyen, T. Tang
    SLAC, Menlo Park, California
 
 

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515


Introduced by the U.S. Navy more than a decade ago*, the concept of Power Electronic Building Blocks (PEBBs) has been successfully applied in various applications. It is well accepted within the power electronics arena that this concept offers the potential to achieve increased levels of modularity and compactness. This approach is thus ideally suited for applications where easy serviceability and high availability are key, such as the ILC. This paper presents a building block approach for designing Marx modulators. First the concept of "bricks and buses" is briefly discussed. Then a PEBB-oriented design is presented for the basic Marx cell of a 32-cell Marx modulator to power an ILC klystron; 120 kV, 140 A, 1.6 ms pulses at a repetition rate of 5 Hz. Each basic Marx cell is composed of a main cell and a correction cell that compensates the main cell droop. The main cell has a stored energy of 2.1 kJ per Marx cell and the correction cell an additional 0.5 kJ. This design allows over 30% of the total stored energy in the Marx modulator, 84 kJ, to be delivered in the output pulse, 26.9 kJ, while keeping the droop within a ±0.5% range.


*T. Ericsen. 'Power Electronics Building Blocks - A systematic approach to power electronics.' In: Proceedings of Power Engineering Society Summer Meeting, Seattle, WA, 16-20 July 2000.

 
WE3RAC03 High-Power Test Results of a 10 MW, High Efficiency, L-Band Multiple Beam Klystron klystron, cavity, vacuum, electron 1876
 
  • T.W. Habermann, A. Balkcum, R. Begum, H.P. Bohlen, M. Cattelino, E. Cesca, L. Cox, E.L. Eisen, S. Forrest, D. Gajaria, T. Kimura, J.L. Ramirez-Aldana, A. Staprans, B. Stockwell, L. Zitelli
    CPI, Palo Alto, California
 
 

Funding: The authors would like to thank DESY for their support. In addition, we appreciate SLAC helping us out with test equipment.


CPI has designed and is currently in the process of building a prototype of a horizontally oriented multiple beam klystron (MBK) required to provide at least 10 MW peak rf output and 65% efficiency at 1300 MHz and 1.5% rf duty. The klystron was ordered by DESY for the European XFEL. In our design six off-axis electron beams go through seven ring resonators operating in the fundamental-mode. This ensures sufficient beam separation for longer cathode life while keeping the overall diameter of the device small. The MBK was designed using sate-of-the-art multi-dimensional design codes which showed that it was exceeding all performance requirements. First rf hot test data at reduced duty produced 11.2 MW peak saturated rf output and 74% efficiency, which was however accompanied by high beam interception. Initial optimization of the electromagnet resulted in a 70% reduction of the rf body current, but at the expense of rf output power, efficiency (down to 67%) and gain. The magnetic field balance has to be further optimized for low body current and high efficiency at all required operating conditions. Complete test data after optimization and tuning will be presented at the conference.

 

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Slides

 
WE5PFP060 Buffered Electropolishing – A New Way for Achieving Extremely Smooth Surface Finish on Nb SRF Cavities to be Used in Particle Accelerators cavity, SRF, superconductivity, radio-frequency 2141
 
  • A.T. Wu, G. Ciovati, R. Manus, H.L. Phillips, C.E. Reece, R.A. Rimmer, W. Sommer, H. Tian, J.S. Williams
    JLAB, Newport News, Virginia
  • F. Eozénou
    CEA, Gif-sur-Yvette
  • S. Jin, L. Lin, X.Y. Lu, E. Wang
    PKU/IHIP, Beijing
  • J. Mammosser
    ORNL, Oak Ridge, Tennessee
 
 

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.


A new surface treatment technique for niobium (Nb) Superconducting Radio Frequency (SRF) cavities called Buffered Electropolishing (BEP) has been developed at JLab. It was found that BEP could produce the smoothest surface finish on Nb samples ever reported in the literature. Experimental results revealed that the Nb removal rate of BEP could reach as high as 4.67 μm/min. This is significantly faster* than that of the conventional electropolishing technique employing an acid mixture of HF and H2SO4. An investigation is underway to determine the optimum values for all relevant BEP parameters so that the high quality of surface finish achieved on samples can be realized within the geometry of an elliptical RF cavity. Toward this end, single cell Nb cavities are being electropolished by BEP at both CEA-Saclay and JLAB. These cavities will be RF tested and the results will be reported through this presentation.


*Xiangyang Lu et al, to be published.

 
WE5PFP090 Energy Saving Controller for the TLS Booster RF System injection, booster, klystron, cavity 2222
 
  • M.-S. Yeh, L.-H. Chang, L.J. Chen, F.-T. Chung, K.T. Hsu, M.-C. Lin, C.H. Lo, Ch. Wang
    NSRRC, Hsinchu
 
 

The quasi-constant current operation is achieved in the NSRRC by periodically injecting electrons from the booster to the storage ring. It means the booster RF system keeps running during operation period, even the injection period occupies only a small portion of the total operation time. To benefit both the energy saving and klystron life, an energy saving controller has been developed and integrated into the TLS booster RF system. The cathode current of the klystron is decreased during the top-injection period. The energy consumption is thus dramatically reduced. A continuous record since the beginning of 2009 shows this controller can save about 78 percent of energy consumption of the booster RF system during normal operation. An overview of the control architecture and its functionality is presented herein.

 
WE5RFP034 Drive Laser System for the NSRRC Photoinjector laser, gun, electron, linac 2337
 
  • C.S. Chou, J.H. Chen, S.B. Hung, W.K. Lau, A.P. Lee, C.C. Liang
    NSRRC, Hsinchu
  • N.Y. Huang
    NTHU, Hsinchu
 
 

A 266nm ultra-violet laser system has been installed as the drive laser of the NSRRC photoinjector. According to beam dynamic studies for the photoinjector, a 10ps uniform cylindrical beam will be generated at the Cu cathode to reduce emittance growth due to space charge and transverse RF fields in the photoinjector cavity. The main part of this system is diode laser pumped, 798nm regenerative IR amplifier that can provide 85fs pulse at 3.85mJ pulse energy. The conversion of frequency from IR to 266nm UV is achieved by a third harmonic generator. UV output pulse energy exceeds 300uJ. Synchronization between seed laser and the high power microwave system can be better than 1ps. In order to produce a uniform cylindrical beam for emittance reduction in the photoinjector, a refreactive UV beam shape and a pulse stacking temporal beam shape are being implemented.

 
WE6RFP056 Development of a Non-Axisymmetric Permanent Magnet Focusing System for Elliptic Charged-Particle Beams electron, gun, simulation, focusing 2926
 
  • T.M. Bemis, M.H. Lawrence, J.Z. Zhou
    Beam Power Technology, Inc., Chelmsford, MA
  • C. Chen
    MIT/PSFC, Cambridge, Massachusetts
 
 

Funding: This work was funded in part by the Department of Energy, Grant No. DE-FG02-07ER84910 and Grant No. DE-FG02-95ER40919, and the MIT Deshpande Center for Technological Innovation.


High-brightness space-charge-dominated elliptic electron or ion beams have wide applications in high-power rf sources, particle accelerators, and/or ion implantation. Building upon recent inventions and theoretical studies on the generation and transport of elliptic charged-particle beams, a basic research and development program is being carried out to experimentally demonstrate a high-brightness, space-charge-dominated elliptic electron beam using a non-axisymmetric permanent magnet focusing system and an elliptic electron gun. Results of the design of such an elliptic electron beam system are presented.

 
WE6RFP087 Development and Testing of X-Band Dielectric-Loaded Accelerating Structures multipactoring, accelerating-gradient, electron, acceleration 3001
 
  • S.H. Gold
    NRL, Washington, DC
  • W. Gai, R. Konecny, W. Liu, J.G. Power
    ANL, Argonne
  • C.-J. Jing, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • A.K. Kinkead
    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.

 
TH5PFP063 A Dispersion Free Three-Dimensional Space-Charge Modeling Method space-charge, klystron, electron, linac 3348
 
  • M. Hess, C.S. Park
    IUCF, Bloomington, Indiana
 
 

Funding: This work is supported by AFOSR under grant FA9550-08-1-0160.


We present the theoretical and numerical results of a dispersion free time-dependent Green's function method which can be utilized for calculating electromagnetic space-charge fields due to arbitrary current in a conducting pipe. since the Green's function can be expanded in terms of solutions to the wave equation, the numerical solutions to the fields also satisfy the wave equation yielding a completely dispersion free numerical method. This technique is adequately suited for modeling bunched space-charge dominated beams, such as those found in high-power microwave sources, for which the effects of numerical grid dispersion and numerical Cherenkov radiation are typically found when using FDTD type methods.

 
TH5PFP064 Time-Retardation Effect Causing Beamloss in the RF Photoinjector space-charge, beam-losses, laser, simulation 3351
 
  • C.S. Park, M. Hess
    IUCF, Bloomington, Indiana
  • W. Gai, J.G. Power
    ANL, Argonne
 
 

Funding: Supported in part by DOE(DE-FG029ER40747) and in part by NSF(PHY-0552389)


Near the cathode in a photoinjector, the electron beam is emitted with low energy, and its dynamics are strongly affected by the beam's space-charge fields. This can cause beam loss at the cathode due to virtual cathode formation. In general, a fully electromagnetic code can correctly predict the beam space-charge fields, beam dynamics, and beam loss. However, an electrostatic type algorithm would overestimate the space-charge fields since it does not incorporate relativistic time-retardation effects which limit the size of the fields near the cathode. IRPSS (Indiana RF Photocathode Source Simulator) can calculate the electromagnetic space-charge fields using a Green’s function method to a high-precision, and can track beam dynamics in the RF photoinjector. Using IRPSS, we simulated the beam dynamics and beam loss near the cathode for the Argonne Wakefield Accelerator 1.3 GHz gun* and compared those results to electrostatic codes, such as PARMELA and ASTRA.


*P. Schoessow, PAC 2009.

 
TH5PFP094 Bunch Length Measurement with RF Deflecting Cavity at Tsinghua Thomson-Scattering X-Ray Source cavity, electron, gun, scattering 3429
 
  • J. Shi, H. Chen, Q. Du, Y.-C. Du, W.-H. Huang, R.K. Li, C.-X. Tang, L.X. Yan
    TUB, Beijing
  • D. Li
    LBNL, Berkeley, California
 
 

Funding: Supported by National Natural Science Foundation of China (No.10775080)


An S-band RF deflecting cavity has been developed and applied for measuring the bunch length at Tsinghua Thomson-Scattering X-ray Source (TTX). This paper briefly introduces the 3-cell pi-mode standing-wave deflecting cavity and reports the recent experiments of the beam diagnostics for the photo-cathode RF gun, which produces electron bunches with RMS length around 1-ps. It is also observed that the bunches are lengthened while the total charge increases, showing the strong space charge effect at a low beam energy.

 
TH5RFP005 Pepper-Pot Based Diagnostics for the Measurement of the 4D Transverse Phase Space Distribution from an RF Photoinjector at the AWA emittance, simulation, electron, solenoid 3444
 
  • J.G. Power, M.E. Conde, W. Gai, W. Liu
    ANL, Argonne
  • P. Piot
    Northern Illinois University, DeKalb, Illinois
 
 

Funding: The work is supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 with Argonne National Laboratory.


Phase space measurements of RF photoinjectors have usually been done with multislit masks or scanning slits. These systems implicitly ignore the correlations between the X and Y planes and thus yield measurements of the projected 2D phase space distributions. In contrast, a grid-patterned pepper-pot is capable of measuring the full 4D transverse phase space distribution, f(x,x',y,y'). 4D measurements allow precise tuning of electron beams with large canonical angular momentum, important for electron cooling and flat beam transformation, as well as zeroing the magnetic field on the photocathode is zero for ultra low emittance applications (e.g. SASE FEL, ERL FEL). In this talk, we report on a parametric set of measurements to characterize the 4D transverse phase space of the 1 nC electron beam from the Argonne Wakefield Accelerator (AWA) RF photoinjector. The diagnostic is simulated with TStep, including the passage of the electron beam trough the mask and tracking of the beamlets to the imaging screen. The phase space retrieval algorithm is then bench marked against simulations and measurements.

 
TH5RFP079 Simulations of Picosecond Timing Using Large-Area Photodetectors electron, simulation, ion, radiation 3630
 
  • T.J. Roberts, R.J. Abrams, V. Ivanov
    Muons, Inc, Batavia
  • H.J. Frisch
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois
 
 

Many measurements in particle and accelerator physics are limited by the time resolution with which individual particles can be detected. This includes particle identification via time-of-flight in major experiments like CDF at Fermilab and Atlas and CMS at the LHC, as well as the measurement of longitudinal variables in accelerator physics experiments. Large-scale systems, such as neutrino detectors, could be significantly improved by inexpensive, large-area photo detectors with resolutions of a few millimeters in space and a few picoseconds in time. Recent innovations make inexpensive, large-area detectors possible, with only minor compromises in spatial and time resolution. The G4beamline program [1] is one of the appropriate tools for simulation of low-energy physics processes. The set of specialized tools - MCPS [2], POISSON-2 [3] and Monte Carlo Simulator was used for numerical study of different photo multipliers.

 
TH6REP090 Laser Timing Jitter Measurements Using a Dual-Sweep Streak Camera at the A0 Photoinjector laser, vacuum, emittance, cavity 4171
 
  • J. Ruan, A.H. Lumpkin, J.K. Santucci
    Fermilab, Batavia
 
 

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.


Excellent phase stability of the drive laser is a critical performance specification of photoinjectors such as Fermilab’s A0 photoinjector (A0PI). Previous efforts based on the measurement of the power spectrum of the signal of a fast photodiode illuminated by the mode locked infra-red laser pulse component indicated a phase jitter of less than 1.4 ps (technique limited). A recently procured dual-sweep plugin unit and existing Hamamatsu C5680 streak camera were used to study the phase stability of the UV laser pulse component. Initial measurements with the synchroscan vertical sweep unit locked to 81.25 MHz showed that the phase slew through the micropulse train and the phase jitter micropulse to micropulse were two key aspects that could be evaluated. The phase slew was much less than 100 fs per micropulse, and the total phase jitter (camera, trigger, and laser) was approximately 300 fs RMS for measurements of 20-micropulse trains. Data on the macropulse phase stability were also obtained. A possible upgrade to achieve better phase stability will be also discussed.

 
TH6REP094 Time Jitter Measurement for the NSRRC Photo-Injector Drive Laser laser, controls, emittance, cavity 4177
 
  • C.C. Liang, C.S. Chou, K.T. Hsu, W.K. Lau, A.P. Lee, S.H. Lee
    NSRRC, Hsinchu
 
 

The 266 nm UV drive laser for the NSRRC 2998 MHz photo-injector system is generated from a nonlinear optical crystal that is driven by a 798 nm, 3.5 mJ Ti:Sapphire laser amplifier system. Synchronization of the seed laser pulses with the master oscillator of the photo-injector high power microwave system is done by locking the laser to the rf clock signal with time jitter of less than a picosecond. A detector circuit is being built to measure this jitter at sub-picosecond time resolution. Preliminary results of this jitter measurement electronics that have been tested with artificial signals are presented.

 
FR5PFP065 The Object Oriented Parallel Accelerator Library (OPAL) space-charge, simulation, emittance, synchrotron 4461
 
  • A. Adelmann, Y. Ineichen, C. Kraus, T. Schietinger
    PSI, Villigen
  • S.J. Russell
    LANL, Los Alamos, New Mexico
  • J.J. Yang
    CIAE, Beijing
 
 

OPAL (Object Oriented Parallel Accelerator Library) is a tool for charged-particle optics in accelerator structures and beam lines including 3D space charge, short range wake-fields and a 1D coherent synchrotron radiation. Built from first principles as a parallel application, OPAL admits simulations of any scale, from the laptop to the largest HPC clusters available today. Simulations, in particular HPC (High Performance Computing) simulations, form the third pillar of science, complementing theory and experiment. In this paper we present numerical and HPC capabilities such as fast direct and iterative solvers together with timings up to several thousands of processors. The application of OPAL to our PSI-XFEL project as well as to the ongoing high power cyclotron upgrade will demonstrate OPAL's capabilities applied to ongoing projects at PSI. Plans for future developments will be discussed.

 
FR5PFP081 3D Simulations of Secondary Electron Generation and Transport in a Diamond Electron Beam Amplifier electron, scattering, simulation, emittance 4497
 
  • R. Busby, J.R. Cary, D.A. Dimitrov
    Tech-X, Boulder, Colorado
  • I. Ben-Zvi, X. Chang, J.W. Keister, E.M. Muller, T. Rao, J. Smedley, Q. Wu
    BNL, Upton, Long Island, New York
 
 

Funding: The work at Tech-X Corp. is supported by the U. S. Department of Energy under the DE-FG02-06ER84509 SBIR grant.


The Relativistic Heavy Ion Collider (RHIC) contributes fundamental advances to nuclear physics by colliding a wide range of ions. A novel electron cooling section, which is a key component of the proposed luminosity upgrade for RHIC, requires the acceleration of high-charge electron bunches with low emittance and energy spread. A promising candidate for the electron source is the recently developed concept of a high quantum efficiency photoinjector with a diamond amplifier. To assist in the development of such an electron source, we have implemented algorithms within the VORPAL particle-in-cell framework for modeling secondary electron and hole generation, and for charge transport in diamond. The algorithms include elastic, phonon, and impurity scattering processes over a wide range of charge carrier energies. Results from simulations using the implemented capabilities will be presented and discussed.

 
FR5PFP082 Investigation of Charge Gain in Diamond Electron Beam Amplifiers via 3D Simulations electron, simulation, scattering, emittance 4500
 
  • D.A. Dimitrov, R. Busby, J.R. Cary
    Tech-X, Boulder, Colorado
  • I. Ben-Zvi, X. Chang, J.W. Keister, E.M. Muller, T. Rao, J. Smedley, Q. Wu
    BNL, Upton, Long Island, New York
 
 

Funding: The work at Tech-X Corp. is supported by the US DoE under grant DE-FG02-06ER84509.


A promising new concept of a diamond amplified photocathode for generation of high-current, high-brightness, and low thermal emittance electron beams was recently proposed* and is currently under active development. To better understand the different effects involved in the generation of electron beams from diamond, we have been developing models (within the VORPAL computational framework) to simulate secondary electron generation and charge transport. The currently implemented models include inelastic scattering of electrons and holes for generation of electron-hole pairs, elastic, phonon, and charge impurity scattering. We will present results from 3D VORPAL simulations with these capabilities on charge gain as a function of primary electron energy and applied electric field. Moreover, we consider effects of electron and hole cloud expansion (initiated by primary electrons) and separation in a surface domain of diamond.


*I. Ben-Zvi et al., Secondary emission enhanced photoinjector, C-AD Accel. Phys. Rep. C-A/AP/149, BNL (2004).

 
FR5REP022 XAL-Based Applications and Online Model for LCLS controls, solenoid, gun, cavity 4811
 
  • P. Chu, R.H. Iverson, P. Krejcik, G.R. White, M. Woodley, J. Wu
    SLAC, Menlo Park, California
  • Q. Gan
    IHEP Beijing, Beijing
 
 

Funding: Work supported in part by the DOE Contract DE-AC02-76SF00515. This work was performed in support of the LCLS project at SLAC.


XAL, a high-level application framework originally developed by Spallation Neutron Source (SNS), has been adapted by the Linac Coherent Light Source (LCLS) project. The work includes proper relational database schema modification to better suit XAL configuration data requirement, addition of new device types for LCLS online modeling purpose, longitudinal coordinate system change to better represent the LCLS electron beam rather than proton or ion beam in the original SNS XAL design, intensively benchmark with MAD and present SLC modeling system for the online model, and various new features to the XAL framework. Storing online model data in a relational database and providing universal access methods for other applications is also described here.

 
FR5REP083 ‘S’ Band Linac Tube Developmental Work in SAMEER linac, cavity, electron, target 4969
 
  • R. Krishnan, S.T. Chavan, A. Deshpande, T.S. Dixit, C.S. Nainwad, S.N. Pethe, T. Tiwari
    SAMEER, Mumbai
 
 

The developmental work on linear electron accelerators in SAMEER, India is briefed in this paper. The technology to develop ‘S’ band compact side coupled standing wave electron linear accelerator is very well established at SAMEER, Mumbai center. 6 MV to 15 MV linacs are developed with the desired specifications. Indigenous 6 MV linac machines for radiotherapy applications have been developed successfully and these machines are in use at premier cancer hospitals in the country. SAMEER is presently working on the development of the dual mode-electron and photon and dual photon energy linear accelerator for radiotherapy application. The 6 MeV linac tube development and its test results are discussed.

 
FR5REP091 The Primary Experiment of Multipactor Electron Gun Based Accelerator electron, cavity, gun, multipactoring 4990
 
  • M. Zhong, C.-X. Tang, S.X. Zheng
    TUB, Beijing
 
 

The Multipactor Electron Gun (MEG) can produce high current self-bunching electron beams. In this paper, the primary experimental results of an S-band MEG based accelerator are presented. The accelerator was modified from a 6MeV standing wave accelerator to integrate the MEG, which has an adjusting structure to control both the cathode-grid distance and frequency tuner. The designed output energy is 5MeV and average current is 100mA. The experiment included low power microwave parameter measurement and high power beam test. In the microwave parameter measurement, the relationship between tuner position and E-field distribution was investigated. Platinum was used as the secondary electron emitters of the MEG. The multipacting process was observed and an average current of 40mA was collected by an aluminum target.