Keyword: cathode
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MOODA03 First Characterization of a Fully Superconducting RF Photoinjector Cavity cavity, laser, linac, solenoid 41
 
  • A. Neumann, W. Anders, R. Barday, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, A.N. Matveenko, T. Quast, J. Rudolph, S.G. Schubert, J. Völker
    HZB, Berlin, Germany
  • P. Kneisel
    JLAB, Newport News, Virginia, USA
  • R. Nietubyc
    The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  • J. Smedley
    BNL, Upton, Long Island, New York, USA
  • V. Volkov
    BINP SB RAS, Novosibirsk, Russia
  • G. Weinberg
    FHI, Berlin, Germany
  • I. Will
    MBI, Berlin, Germany
  
  As a first step towards a high brightness, high average current electron source for the BERLinPro ERL a fully superconducting photo-injector was developed by HZB in collaboration with JLab, DESY and the A. Soltan Institute. This cavity-injector ensemble is made up of a 1.6-cell superconducting cavity with a superconducting lead cathode deposited on the half-cell backwall. A superconducting solenoid is used for emittance compensation. This system, including a diagnostics beamline, has been installed in the HoBiCaT facility to serve as a testbed for beam dynamics studies and to test the combination SRF cavity and superconducting solenoid. This paper summarizes the characterization of the cavity in this configuration including Q measurements, dark current tests and field-stability analyses.  
slides icon Slides MOODA03 [10.343 MB]  
 
MOPC007 Cold Photocathode RF Gun cavity, gun, vacuum, cryogenics 77
 
  • V. Vogel, K. Flöttmann, S. Schreiber
    DESY, Hamburg, Germany
  
  Heating and thermal expansion in the normal conductivity RF-photo electron gun, are the main limitations to achieve high accelerating gradient and consequently a low emittance beam. Some pure materials show a significant increase in thermal conductivity with a small coefficient of temperature expansion at temperatures around 20 degrees Kelvin. Possible materials are Molybdenum, Iridium or Tungsten. However, machining of these materials is very difficult. Therefore we propose a simplified shape for an L-band RF gun. We expect to achieve a significant increase in gradient for similar RF powers as used in the present DESY RF-gun. On the other hand, it would also be possible to increase the duty cycle keeping a moderate gradient. In this report we discuss one possible design of an RF-gun using hard metals and present simulations on thermal properties.  
 
MOPC014 RF Processing of L-band RF Gun for KEK-STF cavity, gun, laser, solenoid 92
 
  • M. Kuriki, H. Iijima, Y.M. Masumoto
    HU/AdSM, Higashi-Hiroshima, Japan
  • H. Hayano, H. Sugiyama, J. Urakawa, K. Watanabe
    KEK, Ibaraki, Japan
  • G. Isoyama, R. Kato
    ISIR, Osaka, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • Y. Takahashi
    Sokendai, Ibaraki, Japan
  
  Funding: This work is supported by MEXT Quantum Beam Technology Program, KEK Promotion of collaborative research programs in universitie.
KEK STF (Superconducting Test Facility) is established for developing super-conducting accelerator technology for ILC (International Linear Collider). At KEK-STF, accelerator operation with a beam loading is planned in 2013. An electron injector based on L-band Photo-cathode RF gun is now being developed. A L-band RF gun designed by DESY and fabricated by FNAL has been placed in KEK-STF and RF processing was carried out. The results of the RF processing and status of STF injector will be presented. 		 
 
MOPC022 Development of a Compact C-band Photocathode RF Gun gun, electron, injection, emittance 116
 
  • X.H. Liu, H. Chen, W.-H. Huang, H.J. Qian, C.-X. Tang, Z. Zhang
    TUB, Beijing, People's Republic of China
  
  Funding: This work is supported by National Natural Science Foundation of China and National Basic Research Program of China (973 Program).
A C-band photocathode RF gun for a compact electron diffraction facility is developed in Tsinghua University, which is designed to work at the frequency of 5.712GHz. This paper presents the physics and structure design of this C-band RF gun, and the comparison on beam dynamics of S-band and C-band photoinjector has been done. Some new structure design will be adopted in this gun, including the optimized cavity length and elliptical iris, which is helpful to achieve lower emittance and larger mode separation. 		 
 
MOPC033 The Status of a 1.6-cell Photocathode RF Gun at PAL gun, cavity, klystron, emittance 142
 
  • M.S. Chae, J.H. Hong, I.S. Ko, Y.W. Parc
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • S.J. Park
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  The RF power conditioning of the photocathode RF gun with four holes at the side of the full cell named as 'Pohang gun' is in progress. The first goal of the conditioning is the operation of the gun with RF pulse width of 1.5 μm, repetition rate of 30 Hz, field gradient at the cathode of 130 MV/m. We operated the RF gun successfully with the conditions within last few months. It was first operational experience with such conditions in PAL. Now we have a plan to operate RF gun with higher repetition rate up to 60 Hz.  
 
MOPC034 Design of a 0.6-cell Cell Photocathode RF Gun for FED gun, electron, simulation, solenoid 145
 
  • Y.W. Parc, M.S. Chae, I.S. Ko
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  
  Final goal of this study is the development of single cell radio-frequency (RF) electron gun which is optimized to the femotosecond electron diffraction. This study will open new technology basis for the laboratory research in the femto-second (fs) chemistry at the university. RF electron gun will be fabricated with single cell which will reduce the cost and effort. We will also conduct a simulation study to find an optimized operation condition of the RF gun to provide the best electron beam to the femtosecond electron diffraction experimentalist. In this presentation, we will show the status of the RF gun development. The results with the simulation code PARMELA will be presented to find the optimal operation condition of the single cell RF gun for FED.  
 
MOPC064 Upgrade and Commissioning of the 88-Inch Cyclotron Final Power Amplifier cyclotron, resonance, ion, impedance 229
 
  • M. Kireeff Covo, D.F. Byford, P.W. Casey, A. Hodgkinson, S. Kwiatkowski, C.M. Lyneis, L. Phair, A. Ratti, C.P. Reiter
    LBNL, Berkeley, California, USA
  
  Funding: This work was supported by the Director, Office of Science, Office of High Energy and Nuclear Physics, Division of Nuclear Physics, U.S. Department of Energy under Contract DE-AC02-05CH11231.
The RF system of the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory is a resonant system based on the quarter-wave cantilever type resonating structure. Power is fed to the Dee from the anode of the 500 kW RCA 6949 tetrode tube operating in grounded cathode configuration, which is capacitively coupled to the side of the Dee stem. The tube is obsolete and makes its continued use impractical. A new final power amplifier was designed and built using the commercially available tube Eimac 4W150,000E. The new amplifier was successfully commissioned and has been reliable and easy to operate. An overview of the system upgrade and details of the commissioning will be presented. 		 
 
MOPC067 X-Band Test Station at Lawrence Livermore National Laboratory electron, klystron, laser, brightness 235
 
  • R.A. Marsh, F. Albert, S.G. Anderson, C.P.J. Barty, G.K. Beer, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck
    LLNL, Livermore, California, USA
  • C. Adolphsen, A.E. Candel, T.S. Chu, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou
    SLAC, Menlo Park, California, USA
  
  Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
An X-band multi-bunch test station is being built at LLNL to investigate the science and technology paths required to boost the current mono-energetic gamma-ray (MEGa-Ray) brightness by orders of magnitude. The test station will consist of a 5.5 cell X-band RF photoinjector, single accelerator section, and beam diagnostics. Beam quality must be exceedingly high in order to produce narrow-bandwidth gamma-rays, requiring a robust state of the art photoinjector. The photoinjector will be a high gradient (200 MV/m peak surface field on the cathode) standing wave structure, featuring a dual feed racetrack coupler, elliptical irises, and an optimized first cell length. A solid-state Scandinova modulator will power a single SLAC XL4 11.424 GHz 50 MW klystron. RF distribution will allow for full powering of the photoinjector with the balance of the RF powering a single accelerator section so that the electron parameters can be measured. The status of the facility will be presented including commissioning schedule and first experiment plans. Future experimental programs pertinent to Compton scattering R&D, high gradient structure testing, and light source development will be discussed. 		 
 
MOPC081 Pulsed Mode Operation and Longitudinal Parameter Measurement of the Rossendorf SRF Gun gun, cavity, SRF, laser 262
 
  • J. Teichert, A. Arnold, H. Büttig, M. Justus, U. Lehnert, P. Michel, P. Murcek, Ch. Schneider, R. Schurig, R. Xiang
    HZDR, Dresden, Germany
  • T. Kamps, J. Rudolph, M. Schenk
    HZB, Berlin, Germany
  • I. Will
    MBI, Berlin, Germany
  
  Funding: The European Community-Research Infrastructure Activity under the FP7 program (EuCARD, contract number 227579) the German Federal Ministry of Education and Research grant 05 ES4BR1/8.
The Rossendorf SRF gun with a 3 1/2 cell cavity has been operated since 2007. It has produced CW beam with the electron energy of 3 MeV and the average current up to 16 μA. The electron beam of the gun has successfully injected the ELBE superconducting linac since 2010. The Nb cavity has shown constant quality during the operation and for the Cs2Te photocathode life time of months could be obtained. Recently the gun started to run in the pulsed mode with higher gradient. The longitudinal parameters have been measured in this mode. The dark current arose from the high gradient is studied. The main field emission source has been found to be the half cell. Meanwhile, two modified 3+1/2 cell niobium cavities have been fabricated and tested in Jlab. In this paper the new status of the SRF gun will be presented, and the latest results of the beam experiments will be discussed. 		 
 
MOPC092 Effect of Current Densities on Sulfur Generation at Electropolished Niobium Surface cavity, niobium, electron, vacuum 292
 
  • P.V. Tyagi
    Sokendai, Ibaraki, Japan
  • H. Hayano, S. Kato, M. Nishiwaki, T. Noguchi, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
  
  We conducted a series of electropolishing (EP) experiments in aged EP acid with high (≈50 mA/cm2) and low (≈30 mA/cm2) current densities on Nb surfaces. The experiments were carried out both for laboratory coupons and a real Nb single cell cavity with six witness samples located at three typical positions (equator, iris and beam pipe). All the samples surface were investigated by XPS (x-ray photoelectron spectroscopy), SEM (scanning electron microscope) and EDX (energy dispersive x-ray spectroscopy). The surface analysis showed the EP with a high current density produced a huge amount sulfate particles at Nb surface whereas the EP with a low current density is very helpful to mitigate sulfate at Nb surface in both the experiments.  
 
MOPC104 HIE-ISOLDE SRF Development Activities at CERN cavity, vacuum, niobium, SRF 316
 
  • M. Therasse, O. Brunner, S. Calatroni, J.K. Chambrillon, B. Delaup, M. Pasini
    CERN, Geneva, Switzerland
  
  The HIE-ISOLDE project has initiated a new development phase on the SRF domain at CERN. In particular, the HIE-ISOLDE project aims at the construction of the 32 Quarter Wave Resonators (QWRs) using the Nb on Cu sputtering technology. The paper describes the refurbishment of the test infrastructure and the activities from the cavity production to the cold test, including quality assurance procedure for the correct handling of the resonators.  
 
MOPC117 Advance in Vertical Buffered Electropolishing on Niobium for Particle Accelerators* cavity, SRF, niobium, radio-frequency 352
 
  • A.T. Wu, S. Jin, J.D. Mammosser, C.E. Reece, R.A. Rimmer
    JLAB, Newport News, Virginia, USA
  • L. Lin, X.Y. Lu, K. Zhao
    PKU/IHIP, Beijing, People's Republic of China
  
  Funding: The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
Niobium (Nb) is the most popular material that has been employed for making superconducting radio frequency (SRF) cavities to be used in various particle accelerators over the last couple of decades. One of the most important steps in fabricating Nb SRF cavities is the final chemical removal of 150 μm of Nb from the inner surfaces of the SRF cavities. This is usually done by either buffered chemical polishing (BCP) or electropolishing (EP). Recently a new Nb surface treatment technique called buffered electropolishing (BEP) has been developed at Jefferson Lab. It has been demonstrated that BEP can produce the smoothest surface finish on Nb ever reported in the literature while realizing a Nb removal rate as high as 10 μm/min that is more than 25 and 5 times quicker than those of EP and BCP(112) respectively. In this contribution, recent advance in optimizing and understanding BEP treatment technique is reviewed. Latest results from RF measurements on BEP treated Nb single cell cavities by our unique vertical polishing system will be reported.
Authored by The Southeastern Universities Research Association, Inc. under U.S. DOE Contract No. DE-AC05-84ER40150. 		 
 
MOPC119 Fastest Electropolishing Technique on Niobium for Particle Accelerators* cavity, SRF, niobium, linear-collider 358
 
  • A.T. Wu, S. Jin, R.A. Rimmer
    JLAB, Newport News, Virginia, USA
  • X.Y. Lu, K. Zhao
    PKU/IHIP, Beijing, People's Republic of China
  
  Funding: The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
Field emission on the inner surfaces of niobium (Nb) superconducting radio frequency (SRF) cavities is still one of the major obstacles for reaching high accelerating gradients for SRF community. Our previous experimental results [1] seemed to imply that the threshold of field emission was related to the thickness of Nb surface oxide layers. In this contribution, a more detailed study on the influences of the surface oxide layers on the field emission on Nb surfaces will be reported. By anodization technique, the thickness of the surface pentoxide layer was artificially fabricated from 3nm up to 460nm. A home-made scanning field emission microscope (SFEM) was employed to perform the scans on the surfaces. Emitters were characterized using a scanning electron microscope together with an energy dispersive x-ray analyzer. The experimental results could be understood by a simple model calculation based on classic electromagnetic theory as shown in Ref.1. Possibly implications for Nb SRF cavity applications from this study will be discussed.
Authored by The Southeastern Universities Research Association, Inc. under U.S. DOE Contract No. DE-AC05-84ER40150. 		 
 
MOPC142 25 Year Performance Review of the SLAC 5045 S-Band Klystron klystron, high-voltage, linac, linear-collider 409
 
  • A. Jensen, A.S. Beebe, M.V. Fazio, A.A. Haase, E.N. Jongewaard, C. Pearson, D.W. Sprehn, A.E. Vlieks, L.E. Whicker
    SLAC, Menlo Park, California, USA
  
  Funding: This work was supported by the U.S. Department of Energy under contract DE-AC03-76SF00515.
The SLAC 5045 S-band klystron has proven to be a remarkably reliable high peak power tube. Originally developed in the 1980’s as an upgraded RF power source for the Stanford Linear Collider, it has continually powered the SLAC linac in support of numerous programs in particle physics and photon science. The large number of tubes built and operated (more than 800) coupled with accumulated running statistics over the last 25+ years represents an unprecedented wealth of operational experience for high pulse power klystrons in accelerator applications. Mean time between failures has continued to rise during this period and is frequently in excess of 100,000 hours during the last several years. Lifetime statistics as well as some important failure modes are presented and examined here. 		 
 
MOPC150 High Charge PHIN Photo Injector at CERN with Fast Phase Switching within the Bunch Train for Beam Combination laser, vacuum, gun, bunching 430
 
  • M. Divall Csatari, A. Andersson, B. Bolzon, E. Bravin, E. Chevallay, A.E. Dabrowski, S. Döbert, V. Fedosseev, C. Heßler, T. Lefèvre, S. Livesley, R. Losito, O. Mete, M. Olvegård, M. Petrarca, A. Rabiller
    CERN, Geneva, Switzerland
  • A. Drozdy
    BUTE, Budapest, Hungary
  • D. Egger
    EPFL, Lausanne, Switzerland
  
  The high charge PHIN photo-injector was developed within the frame of the European CARE program to provide an alternative to the drive beam thermionic gun in CTF3 (CLIC Test Facility) at CERN. In PHIN 1908 bunches are delivered with bunch spacing of 1.5 GHz and 2.33 nC charge per bunch. Furthermore the drive beam generated by CTF3 requires several fast 180 deg phase-shifts with respect to the 1.5 GHz bunch repetition frequency in order to allow the beam combination scheme developed at CTF3. A total of 8 sub-trains, each 140 ns long and shifted in phase with respect to each other, have to be produced with very high phase and amplitude stability. A novel fiber modulator based phase-switching technique developed on the laser system provides this phase-shift between two consecutive pulses much faster and cleaner than the base line scheme, where a thermionic electron gun and sub-harmonic bunching are used. The paper describes the fiber-based switching system and the measurements verifying the scheme. Stability measurements are presented for the phase-coded system. The paper also discusses the latest 8nC charge production and cathode life-time studies on Cs2Te.  
 
MOPO018 Active Beam Current Stabilization in the Cornell ERL Prototype Injector laser, feedback, gun, cavity 523
 
  • F. Löhl, P. Szypryt
    CLASSE, Ithaca, New York, USA
  
  In order to operate the Cornell ERL prototype injector at beam currents beyond 10 mA, the beam current has to be highly stable. The reason is that fast beam current fluctuations generate transient effects in the DC gun voltage as well as in the fields of subsequent superconducting cavities, which can lead to excessive beam loss or to trips of subsystems. Therefore, a feedback scheme was developed which uses the signal of a beam current monitor as an input, and applies appropriate corrections to a Pockels cell installed within the laser path of the photo-injector laser. In this paper, high current results achieved with this feedback scheme are presented.  
 
MOPO043 Applications of Lasers to Accelerator Physics at SSRL laser, gun, photon, electron 580
 
  • D.L. Robinson
    Cal Poly, San Luis Obispo, California, USA
  • W.J. Corbett
    SLAC, Menlo Park, California, USA
  
  Recent advances in accelerator physics and SR research have generated the need for high-power lasers in the SPEAR3 accelerator complex. On the injector side, two lasers are being used to test different photocathode materials and to provide photo-assisted emission from the standard dispenser cathode RF gun. For the storage ring, both a TiSa oscillator and a fiber laser locked to the RF master oscillator have been used to characterize short-pulse electron bunches in cross-correlation experiments. These lasers are also used in SR experiments for pump-probe characterization of materials. In this paper we review the laser-based systems, preliminary results and outlook for the future.  
 
MOPS024 Bunch Dynamics through Accelerator Column space-charge, TRIUMF, gun, electron 649
 
  • R.A. Baartman
    TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
  
  Funding: TRIUMF research is supported by the National Research Council of Canada.
The differential equations for the bunched beam envelope through an axially symmetric DC accelerator are derived. In the case of no space charge, a particle's total energy is conserved, so the longitudinal evolution is simple: particles of same energy are a fixed time increment apart and this implies in first order that their separation is proportional to their speed. However, with space charge, the longitudinal force depends upon the bunch length, so we need equations that track this parameter. The full 6-dimensional and relativistically correct envelope equations are derived. 		 
 
TUODB02 Extreme High Vacuum System of High Brightness Electron Source for ERL gun, vacuum, electron, ion 979
 
  • M. Yamamoto, T. Honda, Y. Honda, T. Miyajima, Y. Saito, Y. Tanimoto, T. Uchiyama
    KEK, Ibaraki, Japan
  • H. Akimichi, H. Yoshida
    AIST, Tsukuba, Japan
  • H. Kurisu
    Yamaguchi University, Ube-Shi, Japan
  
  A compact test accelerator for Japan’s future light source based on energy recovery linac (ERL) is under construction in KEK, aiming to demonstrate key technologies such as a high-brightness photocathode DC-gun and superconducting RF cavities. A DC-gun using GaAs-type photocathode which has a negative electron affinity (NEA) surface is employed. The NEA surface plays an indispensable role to extract electrons from conduction band minimum into vacuum. It assures high quantum efficiency of the photocathode and very low intrinsic emittance of the extracted beam. However, the NEA surface is extremely delicate against residual gas in vacuum. In order to extract mA-level beam currents continuously for more than several tens of hours, the pressure should be lower than the order of ·10-10 Pa to avid the backbombardment of positive ions produced by the collision of accelerated electrons with residual gas molecules in the beam path. Recent achievements in the development of a 500-kV photocathode DC-gun and in the fundamental studies of its extreme high vacuum system will be presented.  
slides icon Slides TUODB02 [1.606 MB]  
 
TUPC043 SEM Field Emission Probe Surface Science Study vacuum, electron, gun, laser 1096
 
  • L. Laurent, R.E. Kirby, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  
  Funding: This work is supported by Department of Energy Contract No. DE-AC03- 76SF00515.
After decades of rf breakdown research, a common acknowledgement among researchers is that a better understanding of what is happening on the surface at a microscopic level needs to be the impetus for future studies. We are designing and fabricating an electron microscope-based high-electric-field current-emission probe to study topographic material features which will enable us to better understand and further advance the technology of high-brightness photocathode rf guns and enable the study of high gradient phenomena. The SEM field emission probe will provide an important diagnostic tool allowing cathodes and high gradient surfaces to be evaluated before and after testing and will help identify and understand the relationship between high field emission locations and vacuum breakdown, non-uniform emission, surface cracking, hotspots, etc. The preliminary results and 2012 goals will be presented. 		 
 
TUPC057 Femtosecond Photoinjector and Relativistic Electron Microscopy gun, electron, emittance, laser 1126
 
  • J. Yang, K. Kan, Y. Murooka, N. Naruse, K. Tanimura, Y. Yoshida
    ISIR, Osaka, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
  
  A new rf gun driven by a femtosecond laser has been developed successfully for the relativistic electron diffraction in Osaka University for the study of ultrafast dynamics of intricate molecular and atomic processes in materials. The beam dynamics of femtosecond electron bunch in the rf gun were investigated to achieve a low-emittance and low-energy-spread; i.e. 0.1 mm-mrad and 10-4. A time-resolved relativistic electron microscopy is being developed to reveal the hidden dynamics on the femtosecond and nanometer scales. The same demonstrations of the MeV electron diffraction/imaging measurements were reported.  
 
TUPC060 A Multi-mode RF Photocathode Gun gun, cavity, injection, electron 1135
 
  • S.V. Kuzikov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT, USA
  • Y. Jiang
    Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
  • V. Vogel
    DESY, Hamburg, Germany
  
  A photocathode injection gun based on standard emittance compensating techniques and driven by several (N ≥ 2) harmonically related RF sources is considered. Multi-harmonic excitation can provide high-quality flatness in time of the field at the cathode when a bunch is being injected. This allows one to obtain ≥1 nC, 20-40 ps electron bunches with preservation of low emittance. Another advantage is a reduction of Ohmic losses and the required input RF power (for a given cathode field). Preliminary calculations show that input power in a three-mode cavity (0.65 GHz, 1.3 GHz, 2.6 GHz) is nearly half the power needed to feed a single mode with the same cathode field. A further appealing property is the predicted increase of breakdown threshold due to a reduction of surface exposure time to high fields in a symmetric cavity, and due to the so-called anode-cathode effect in a longitudinally asymmetric cavity. These properties may help one to reach bunch energies as high as 3-5 MeV after the first half cell.  
 
TUPC101 Generation of Multimode Quasi-monochromatic Terahertz electron, linac, radiation, gun 1248
 
  • K. Kan, T. Kondoh, K. Norizawa, A. Ogata, J. Yang, Y. Yoshida
    ISIR, Osaka, Japan
  
  Generation of quasi-monochromatic terahertz (THz) using multimode Coherent Cherenkov Radiation (CCR) on the order of 0.1 THz was investigated. CCR was generated by a hollow dielectric tube covered by a metal and an electron bunch from a photocathode radio-frequency (RF) gun linac. The intensity and frequency of CCR were measured directly by a Michelson interferometer and a bolometer. The frequency spectra measured by the interferometer indicated sharp peaks close to frequencies of 0.09 THz and 0.14 THz, which corresponded to TM03 and TM04 modes, respectively, according to theoretical calculation for a tube with inner and outer radii of 5 mm and 7 mm. The maximum gain of TM03 mode due to the tube length was obtained as 1.5 dB/cm. The other higher modes, e. g. 0.36 THz (TM09) and 0.40 THz (TM010), were also observed from a 150 mm long tube at a bunch charge of 15 pC, which decreased space charge effect and the bunch length. Finally, a new method for bunch diagnostic based on multimode CCR was proposed. The bunch length was estimated to be 0.45 ps at a bunch charge of 5 pC with the intensity ratio of TM03 to TM09 mode.  
 
TUPC126 Indirect Measurement of Power Deposition on the IFMIF/EVEDA Beam Dump by means of Radiation Chambers neutron, radiation, diagnostics, light-ion 1314
 
  • D. Rapisarda, J.M. Arroyo, B. Brañas, A. Ibarra, D. Iglesias, C. Oliver
    CIEMAT, Madrid, Spain
  • F. Ogando
    UNED, Madrid, Spain
  
  Funding: Work partially supported by Spanish Ministry of Science and Innovation under project AIC10-A-000441 and ENE2009-11230
The beam stop of the IFMIF/EVEDA accelerator will be a copper cone receiving a total power of ~1 MW, coming from 9 MeV D+ at 125 mA. The mechanical stresses in this beam dump come mainly from the thermal gradients generated in the cone, being therefore related with the power deposition profile. Anomalous situations such as beam misalignments or incorrect focusing can lead to variations in this profile outside the normal operation range. These variations must be detected and corrected for beam dump protection. Due to the interaction between D+ and the copper cone important neutron and gamma fluxes are generated around the beam dump (1010 – 1011 n/cm2/s, 1010 p/cm2/s) with a spatial profile which is directly linked to the power deposition. In this work, a diagnostic based on a set of radiation chambers is proposed to measure on-line this radiation field, giving indirect information about the power deposition on the beam dump. The sensitivity of the radiation field to the power deposition profile is demonstrated and the diagnostic strategy explained, establishing the main specifications and requirements of the detectors. 		 
 
TUPC178 Charge Lifetime Study of K2CsSb Photocathode Inside a Jlab DC High Voltage Gun laser, vacuum, gun, high-voltage 1443
 
  • R.R. Mammei, M. Poelker, R. Suleiman
    JLAB, Newport News, Virginia, USA
  • J.L. McCarter
    UVa, Charlottesville, Virginia, USA
  • T. Rao, J. Smedley
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE
Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness for current and future accelerator applications: GaAs:Cs and K2CsSb. Each photocathode has advantages and disadvantages, and need to demonstrate performance at “production” accelerator facilities. To this end a K2CsSb photocathode was manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ~ 5x10-11 Torr. This photocathode was installed inside a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at 440 or 532 nm, to generate beams up to 20 mA. Photocathode charge lifetime measurements indicate that under some conditions this cathode has exceptionally high charge lifetime, without measurable QE decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. These studies also suggest a complex QE decay mechanism likely related to chemistry and localized heating via the laser beam. 		 
 
TUPO026 Developments towards a Full Energy Recovery Linac cavity, gun, HOM, SRF 1494
 
  • P. vom Stein, J.H. Hottenbacher, A. Metz
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  
  Energy Recovery Linacs (ERLs) are high potential candidates for driving light sources based on laser Compton scattering with high brilliance photon beams and sub pico second time structure. We report on developments for an advanced ERL design, which allows the recovery of nearly full electron beam energy up to the limits set by the energy width of the beam. This “Full” Energy Recovery Linac (FERL) allows a substantial reduction of the complexity of the accelerator systems resulting into a very compact light source design suitable for industrial and medical applications.  
 
TUPS001 Upgrade of the ESRF Vacuum System vacuum, storage-ring, controls, synchrotron 1515
 
  • M. Hahn, J.C. Biasci, H.P. Marques, A. Meunier
    ESRF, Grenoble, France
  
  The upgrade program of the ESRF concerns in terms of electron storage ring vacuum chambers mainly the insertion device (ID) sectors. Here the length available for the production of intense synchrotron light is being increased from five to six or even seven meters. The presence of canted ID sectors where two independent synchrotron light beams will be produced in the same straight section requires new quadrupole chambers compatible with the new geometry. A number of long insertion device vacuum chambers for the new ID sectors has already been produced by ESRF and coated with non-evaporable getter (NEG) material, a new generation of in vacuum undulators for the extended ID sections are under preparation. This paper outlines the status of the modification of the vacuum system and informs about consequences for the ESRF NEG coating activity and some recent improvements of the vacuum measurement and control system.  
 
TUPS004 Enhanced High-voltage Holding under Vacuum by Field Induced Adsorption of Gas on Metal Surfaces high-voltage, vacuum, electron, plasma 1524
 
  • A. Simonin, L. Christin, L. Doceul, F. Faisse, F. Villecroze, H. de Esch
    CEA, St Paul Lez Durance, France
  
  *The energy of future neutral beam injector heating systems of fusion power plants ranges from 1 to 2 MeV. The beam line and the reactor chamber are under vacuum, while all the electrical components (power supplies) are connected to the injector via a long pressured (SF6) high-voltage (1-2 MV) transmission line. The bushing is a key component that ensures the barrier between the transmission line and the injector under vacuum; the design of this component is very challenging as it faces several stringent constraints due to the nuclear environment, in which high-voltage holding, mechanical stresses, and radiations are combined. Moreover, it is a high-voltage feed-through that allows supply of the accelerator electrodes with electrical power, active water cooling, and gas. In this paper, a new high-voltage bushing concept based on experimental findings previously obtained in the laboratory is presented. The main advantages of the concept is a reduction of the electron field emission under vacuum, which is an issue for conventional bushings, a reduction in size, and mechanical simplification of the device resulting in cost reduction and greater reliability."  
 
TUPS011 Use of NEG Pumps to Ensure Long Term Performances of High Quantum Efficiency Photocathodes ion, vacuum, photon, gun 1539
 
  • L. Monaco, P.M. Michelato, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • P. Manini, F. Siviero
    SAES Getters S.p.A., Lainate, Italy
  
  Laser triggered photo-cathodes are key components of the electron sources of 4th generation light machines. However, they are very sensitive to the vacuum level and its composition. Photo-cathodes are usually prepared in UHV chamber and then transferred, keeping the extreme vacuum condition, to the operation sites. Since transportation/storage may last from several days to weeks, retaining UHV conditions is a fundamental task to the photocathode usage. In this paper the results obtained using a novel pumping approach are given. This approach is based on coupling a 20 l.s−1 ion getter pump with a Capacitorr® D100 Non Evaporable Getter (NEG) pump. Pressure of 2x10-11 mbar was achieved with the NEG pump after 2 days bake-out, as compared to 8x10-10 mbar achieved with the ion pump alone, after 7 days bake-out. Such pressure values were retained even in absence of power, due to the ability of the NEG to remove gases by chemical reaction. Long term monitoring of cathodes QEs was also carried out at different photon wavelengths over more than 6 months, showing no degradation of the photo-emissive film properties.  
 
TUPS087 Development of Permanent Magnet Focusing for Klystrons klystron, permanent-magnet, focusing, target 1743
 
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto, Japan
  • S. Fukuda, T. Matsumoto, S. Michizono, M. Yoshida
    KEK, Ibaraki, Japan
  
  Funding: KEK
Applying permanent magnet technology to beam focusing in klystrons can reduce their power consumption and reliability. These features benefit variety of applications especially for large facilities that use number of klystrons such as ILC. A half scaled model will be available in summer and full model should be available in September. Research and Development status will be reported. 		 
 
WEOAA02 Performance of 2 MeV, 2 kA, 200 ns Linear Induction Accelerator with Ultra Low Beam Emittance for X-Ray Flash Radiography target, electron, focusing, induction 1906
 
  • P.V. Logachev, A. Akimov, P.A. Bak, M.A. Batazova, A.M. Batrakov, Y.M. Boimelshtain, D. Bolkhovityanov, A.A. Eliseev, F.A. Emanov, G.A. Fatkin, A.A. Korepanov, Ya.V. Kulenko, G.I. Kuznetsov, I.V. Nikolaev, A.V. Ottmar, A.A. Pachkov, A. Panov, O.A. Pavlov, D.A. Starostenko
    BINP SB RAS, Novosibirsk, Russia
  
  Funding: The minestry of education and science of Russian Federation R&D contracts:P2493 and 14.740.11.0160
LIA-2 linear induction accelerator is designed in Budker INP as an injector for full scale 20 MeV linear induction accelerator which can be used for X-ray flash radiography with high space resolution. This machine utilizes ultra high vacuum, precise beam optics design based on low temperature dispenser cathode of 190 mm in diameter. The results of LIA-2 commissioning are presented. The designed value of beam emittance (120 π mm•mrad, not normalized) is achieved at 2 MeV and 2 kA of electron beam energy and current. 		 
slides icon Slides WEOAA02 [7.094 MB]  
 
WEPC074 Investigation of the Nonlinear Transformation of an Ion Beam in the Plasma Lens* plasma, ion, focusing, target 2190
 
  • N.N. Alexeev, A.A. Drozdovsky, S.A. Drozdovsky, A. Golubev, Yu.B. Novozhilov, P.V. Sasorov, S.M. Savin, V.V. Yanenko
    ITEP, Moscow, Russia
  
  The plasma lens can carry out not only sharp focusing of ions beam. At those stages at which the magnetic field is nonlinear, formation of other interesting configurations of beams is possible. Plasma lens provides formation of hollow beams of ions in a wide range of parameters*. Application of the several plasma lenses allow to create some nontrivial spatial configurations of ions beams**: to get a conic and a cylindrical beams. The plasma lens can be used for transformation of beams with Gaussian distribution of particles density in a beams with homogeneous spatial distribution. The calculations showed that it is possible for a case of equilibrium Bennett's distribution of a discharge current. This requires a long duration of a discharge current pulse of > 10 μs. The first beam tests have essentially confirmed expected result. Calculations and measurements were performed for a C+6 and Fe+26 beams of 200-300 MeV/a.u.m. energy. The obtained results and analysis are reported.
* A. Drozdovskiy et al., IPAC'10, Kioto, Japan, http://cern.ch/AccelConf/IPAC10 /MOPE040.
** A.Drozdovskiy et al., RUPAC’10, Protvino, Russia, http://cern.ch/AccelConf/RUPAC10 /THCHA01. 		 
 
WEPC132 Simulations of Surface Effects and Electron Emission from Diamond-Amplifier Cathodes electron, simulation, vacuum, scattering 2307
 
  • D.A. Dimitrov, R. Busby, J.R. Cary, D.N. Smithe
    Tech-X, Boulder, Colorado, USA
  • I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  • X. Chang, T. Rao, J. Smedley, Q. Wu
    BNL, Upton, Long Island, New York, USA
  • E. Wang
    PKU/IHIP, Beijing, People's Republic of China
  
  Funding: The authors wish to acknowledge the support of the U.S. Department of Energy (DOE) under grants DE-SC0004431 (Tech-X Corp.), DE-AC02-98CH10886 (BNL), and DE-SC0005713 (Stony Brook University).
Emission of electrons in diamond experiments based on the promising diamond-amplifier concept* was recently demonstrated**. Transmission mode experiments have shown the potential to realize over two orders of magnitude charge amplification. However, the recent emission experiments indicate that surface effects should be understood in detail to build cathodes with optimal properties. We have made progress in understanding secondary electron generation and charge transport in diamond with models we implemented in the VORPAL particle-in-cell computational framework. We will introduce models that we have been implementing for surface effects (band bending and electron affinity), charge trapping, and electron emission from diamond. Then, we will present results from 3D VORPAL diamond-vacuum simulations with the integrated capabilities on generating electrons and holes, initiated by energetic primary electrons, charge transport, and then emission of electrons from diamond into vacuum. Finally, we will discuss simulation results on the dependence of the electron emission on diamond surface properties.
* I. Ben-Zvi et al., Secondary emission enhanced photoinjector, C-AD Accel. Phys. Rep. C-A/AP/149, BNL (2004).
** X. Chang et al., Phys. Rev. Lett. 105, 164801 (2010). 		 
 
WEPZ005 Field Calculations to obtain Attosecond/Femtosecond Electron Bunches laser, electron, injection, radiation 2772
 
  • V.A. Papadichev
    LPI, Moscow, Russia
  
  Obtaining short electron bunches of attosecond and femtosecond duration in a combined quasi-static and laser electric field [* - ****] requires careful field formation in the cathode region. First, the maximum of laser electric field normal to the cathode plate, depending on the incidence angle, was found employing Fresnel formulae using complex dielectric permittivity of metals. Second, laser field enhancement on cathode spikes was calculated for the case of an ellipsoid in a qusi-static approximation (laser wavelength larger than spike dimensions). Field enhancement is approximately proportional to the square of the ratio of major to minor axes of ellipsoid. Thus, enhancement factors as large as 100 - 1000 are obtainable, allowing to reduce laser power by 10 thousand to 1 million times.
* V.A.Papadichev, Patent RU 2 269 877 C1, 10.02.06, Bull. 4.
** V.A.Papadichev, Proc. EPAC08, p.2812.
*** V.A.Papadichev, Proc. EPAC08, p.2815.
**** V.A.Papadichev, Proc. IPAC'10, p. 4372
 		 
 
THPC041 Injector System of Test Accelerator as Coherent Terahertz Source gun, cavity, electron, radiation 2993
 
  • S. Kashiwagi, H. Hama, F. Hinode, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka
    Tohoku University, School of Science, Sendai, Japan
  • N.Y. Huang
    NTHU, Hsinchu, Taiwan
  • F. Miyahara
    KEK, Ibaraki, Japan
  
  Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
A test accelerator as a coherent terahertz source (t-ACTS) project has been under development at Tohoku University, in which a generation of intense coherent terahertz (THz) radiation from sub-picosecond electron bunch will be demonstrated. We will supply a wide-band coherent radiation from bending magnets in an isochronous ring and a narrow-band coherent THz radiation using an undulator in a linac. Stable generation of very short electron bunch is one of the key issues in the t-ACTS project. The injector system is consists of a thermionic RF gun with two independent cavity cells, an alpha magnet and an accelerating structure. A velocity bunching scheme is employed to produce the very short electron bunch. Components of the t-ACTS injector except the accelerating structure have already been installed and we have started a high power RF processing of the gun cavities. The characteristics of electron bunch extracted from the RF gun are measured by varying phase and amplitude of input RF fields for the gun cavities. The status of t-ACTS project will be presented in the conference. 		 
 
THPC109 First Demonstration of Electron Beam Generation and Characterization with an All Superconducting Radio-frequency (SRF) Photoinjector* cavity, SRF, laser, solenoid 3143
 
  • T. Kamps, W. Anders, R. Barday, A. Jankowiak, J. Knobloch, O. Kugeler, A.N. Matveenko, A. Neumann, T. Quast, J. Rudolph, S.G. Schubert, J. Völker
    HZB, Berlin, Germany
  • P. Kneisel
    JLAB, Newport News, Virginia, USA
  • R. Nietubyc
    The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  • J. Smedley
    BNL, Upton, Long Island, New York, USA
  • V. Volkov
    BINP SB RAS, Novosibirsk, Russia
  • G. Weinberg
    FHI, Berlin, Germany
  • I. Will
    MBI, Berlin, Germany
  
  Funding: Work supported by Bundesministerium für Bildung und Forschung und Land Berlin. The work on the Pb cathode film is supported by EuCARD Grant Agreement No. 227579
In preparation for a high brightness, high average current electron source for the energy-recovery linac BERLinPro an all superconducting radio-frequency photoinjector is now in operation at Helmholtz-Zentrum Berlin. The aim of this experiment is beam demonstration with a high brightness electron source able to generate sub-ps pulse length electron bunches from a superconducting (SC) cathode film made of Pb coated on the backwall of a Nb SRF cavity. This paper describes the setup of the experiment and first results from beam measurements. 		 
 
THPC116 Surface Analysis of a Degraded NEA-GaAs Photocathode by Temperature Programmed Desorption Technique vacuum, electron, quadrupole, ion 3158
 
  • H. Iijima, M. Kuriki, Y.M. Masumoto
    HU/AdSM, Higashi-Hiroshima, Japan
  
  A GaAs photocathode activated the surface to negative electron affinity (NEA) is an important device for high-average-current electron accelerators, such as a next-generation light source based on an energy recovery linac. It is well known that the quantum efficiency of the NEA-GaAs photocathode is decaying with time elapsing, even if the electron beam is not extracted. The degradation is mainly caused by adsorption of residual gases in a vacuum chamber. Previously a few investigators reported that the quantum efficiency of the photocathode was rapidly degraded by water or carbon dioxide vapor. In order to analyze such surface states, we have measured desorption of gases from the degraded NEA-GaAs photocathode by using of temperature programmed desorption (TPD) technique with a quadrupole mass spectrometer. The desorption peaks of hydrogen, carbon oxide and carbon dioxide from the degraded NEA surface were observed, while that of water was not observed.  
 
THPC117 Analysis Quantum Efficiency Spectrum of NEA-GaAs Photocathode electron, vacuum, brightness, linac 3161
 
  • Y.M. Masumoto, H. Iijima, M. Kuriki
    HU/AdSM, Higashi-Hiroshima, Japan
  
  ERL is a future project of synchrotron light source with high brightness and partial coherence. ERL is based on super conducting linear accelerator providing the high brightness electron beam to insertion devices continuously. One of the most difficult technical challenge is the electron source for ERL. A photo-cathode DC biased gun is assumed, but several issues should be solved. One of the issue is the operational lifetime of cathode material, NEA GaAs. NEA stands for Negative electron affinity made by artificial treatment on clean GaAs surface. Emission from the cathode is decreased in time and extracted beam current. In order to research the phenomena, the surface potential is studied by measuring the QE　(Quantum Efficiency) spectrum. Observing temporal evolution of QE, we found that the photon energy threshold did not change during the decay. The spectrum shape was changed suggesting that the surface potential barrier becomes thicker.  
 
THPC120 Experimental Investigation of Photocathode Thermal Emittance Components with a Copper Cathode* emittance, gun, laser, electron 3167
 
  • H.J. Qian, Y.-C. Du, Hua, J.F. Hua, W.-H. Huang, C. Li, C.-X. Tang, L.X. Yan
    TUB, Beijing, People's Republic of China
  
  With progress of photocathode RF gun technology, thermal emittance has become the primary limitation of electron beam brightness*. Extensive efforts have been devoted to study thermal emittance, but experiment results diverge between research groups and few can be well interpreted**. One possibility is the undefined online cathode surface conditions, which may cause difference of work functions, field enhancement factor and surface roughness, and lead to thermal emittance divergence. In this paper, we report an experiment of characterizing online photocathode work function, field enhancement factor and surface roughness effect by measuring electric field dependence of photoemission quantum efficiency (QE) and thermal emittance in a Cu-cathode RF gun. Preliminary experiment results reveal huge thermal emittance contributed by surface roughness for the first time, and are in reasonable consistency with theoretical model prediction***.
*Ivan V. Bazarov et al., Phys. Rev. Lett. 102, 104801(2009)
** D.H. Dowell et al, Nucl. Instrum. Methods Phys. Res., Sect. A 622, 685 (2010).
***D. Xinag et al, PAC’07, 1049 (2007) 		 
 
THPC121 Design and Cold Tests of a Prototype photocathode RF Gun for Shanghai SXFEL Facility gun, coupling, vacuum, emittance 3170
 
  • H.J. Qian, H. Chen, Y.-C. Du, W.-H. Huang, C. Li, X.H. Liu, X. H. Lu, C.-X. Tang
    TUB, Beijing, People's Republic of China
  
  A soft X-ray (~9 nm) FEL (SXFEL) facility is going to be constructed in Shanghai, China, which requires high charge (>500 pC) electron beam with low transverse emittance (<1.5 mm-mrad) at photoinjector exit. One of the keys to achieve a low emittance with high charge is high gradient on the photocathode, so an S-band photocathode RF gun modified from BNL type gun is designed, which aims running 100 MV/m peak gradient at 10 Hz. By changing the cathode seal technique, removing the insertion RF tuner, and reducing the peak surface field, RF breakdown possibility is reduced. Besides, RF pulse width is also considered to be reduced to lower the RF breakdown possibility. Since zero mode and multipole field degrades the beam emittance, they are also suppressed in the new gun design. Design details and cold testing results are presented in this paper.  
 
THPC126 RF Gun Studies for the SwissFEL Injector gun, laser, emittance, solenoid 3179
 
  • A. Falone, A. Adelmann, J.-Y. Raguin, L. Stingelin
    PSI, Villigen, Switzerland
  
  The Paul Scherrer Institut (PSI) is planning a compact, high brightness hard X-ray free electron laser. For this purpose a new 2.5 cell RF gun has been designed at PSI and is now in production. The RF gun plays an important role in preserving beam emittance, and hence delivers a high quality beam to the injector. We present beam dynamic parametric studies on the effect of cell length variations using two different codes OPAL and ASTRA. Furthermore laser and other RF parameters are scanned to find the best working point of the injector. The simulations are showing that the SwissFEL injector requirements (ϵ<0.4 mm mrad normalized projected emittance) are achievable with a smooth dependence on the geometrical variation of the gun cell lengths confirming a robust RF design of the gun is possible.  
 
THPC127 Recent Results from a Combined Diode-RF Gun emittance, electron, laser, gun 3182
 
  • C.H. Gough, S. Ivkovic, M. Paraliev
    PSI, Villigen, Switzerland
  
  For the SwissFEL project, a novel combined diode-RF electron gun was tested at PSI, as a possible source for XFELs. Typically, electron bunches of 1-100 pC charge , 1-5 MeV energy and 2-0.3 um-rad emittance were produced and measured. The advantage of the combined gun is that diode geometry and emission surface can be changed readily. An optimum polishing procedure for magnesium photo cathodes was found, and various surfaces such as FEA's were tested in high gradient. Emittance changes for emission surface depression within the cathode, as well as laser spot size and anode hole size, were measured. Finally, the excellent performance of the gun permitted detailed study of the pepperpot EMSY (Emittance Measurement System) behaviour with changing beam parameters.  
 
THPC129 Gallium Arsenide Photocathode Research at Daresbury Laboratory electron, laser, vacuum, gun 3185
 
  • L.B. Jones, B.D. Fell, J.W. McKenzie, K.J. Middleman, B.L. Militsyn
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R.J. Cash
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • N. Chanlek
    UMAN, Manchester, United Kingdom
  
  Significant effort has been expended over several years by ASTeC to optimise procedures for preparing GaAs photocathodes for use as high-current electron sources in accelerators. Having established robust chemical and thermal cleaning processes, and carried out lifetime studies on activated photocathodes by deliberately poisoning them*, we present data showing high levels of Quantum Efficiency (QE) for heterostructure photocathodes when activated with Cs-O and Cs-NF3 procedures. We will show that the use of NF3 delivers higher QE, and conveys greater control in that the final QE level can be set more accurately using NF3 than with O. We plan to carry out further experiments on GaAs photocathodes to measure the 2-D energy distribution of the emitted electrons at both room and cryogenic temperatures. We are constructing a retarding-field electron calorimeter which will measure current as a function of retarding voltage. From this, we will establish the 2-D energy distribution in the electron beam, permitting a comparison of these figures for photocathodes at room and low temperatures. The goal is to create an ultra-bright electron source for use with particle accelerators.
* Proc IPAC ’10, TUPEC018, 1752-1754 		 
 
THPC130 A 160 keV Photocathode Electron Gun Test Tacility gun, electron, diagnostics, laser 3188
 
  • L.B. Jones, B.D. Fell, C. Hill, J.W. McKenzie, K.J. Middleman, B.L. Militsyn
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R.J. Cash
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  The ALICE ERL* at Daresbury Laboratory is a prototype 4th generation free-electron laser light source operating at IR wavelengths. An upgrade to the DC photoinjector gun has been designed and partially-constructed, but due to installation postponement, the system will be used for photocathode physics experiments. The re-designed gun will operate at 160 keV. The gun and photocathode preparation facility (PPF) will be assembled with a diagnostic beamline, supporting research towards high-brightness electron beams based on GaAs technology. Combining an external PPF with a load-lock facility allows the rapid exchange of photocathodes, thus permitting the testing of various different photocathode heterostructures, and fine control of the cleaning and activation processes applied during preparation. The diagnostics beamline will include a transverse kicker to study bunch length, and a dipole magnet for beam energy and energy spread measurements. Various horizontal and vertical slit and screen assemblies allow for emittance measurement, so providing full 6-D characterisation of the electron bunches generated. A current transformer and Faraday cups support bunch charge measurements.
* Accelerators and Lasers In Combined Experiments electron Energy-Recovery Linac 		 
 
THPC134 LCLS RF Gun Copper Cathode Performance laser, gun, emittance, electron 3200
 
  • A. Brachmann, F.-J. Decker, P. Emma, R.H. Iverson, P. Stefan, J.L. Turner, F. Zhou
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by Department of Energy contract DE-AC03-76SF00515
We report on the performance and the operational experience of the LCLS RF gun copper photocathodes used during the LCLS run I, II, III and IV. We discuss the problems of cathode surface contamination and our experience with methods to remove such contamination. Techniques to obtain high quantum efficiency (QE) while preserving the low emittance quality are discussed. Furthermore, we will present the current status of the installed cathode, its quantum efficiency and the typical injector emittances of the extracted beam. 		 
 
THPC135 Optimal Parameters of the Photocathode Gun Space Charge to Improve Beam Quality laser, gun, electron, space-charge 3203
 
  • M.G. Fedurin, C. Swinson, V. Yakimenko
    BNL, Upton, Long Island, New York, USA
  
  Accelerator Test Facility at Brookhaven National Laboratory operates with 5 MeV photocathode gun and 70 MeV linac for different range of experiments with a few picoseconds and a few micrometers emittance electron bunch. Many conducted experiments require beam with good spatial resolution and short length as well. NdYaG laser pulse turns to the electron bunch in the gun with space charge affecting on the own bunch length and transverse profile. Optimal beam loading parameters of the space charge in the photocathode RF gun could be found and used to improve bunch length and emittance. Simple model and experimental results on the Accelerator Test Facility at Brookhaven national Laboratory will be described  
 
THPC136 High Efficiency Visible Photocathode Development synchrotron, vacuum, laser, diagnostics 3206
 
  • J. Smedley, K. Mueller, T. Rao
    BNL, Upton, Long Island, New York, USA
  • K. Attenkofer, S.W. Lee
    ANL, Argonne, USA
  • I. Ben-Zvi, X. Liang, E.M. Muller, M. Ruiz-Oses
    Stony Brook University, Stony Brook, USA
  • H.A. Padmore, T. Vecchione
    LBNL, Berkeley, California, USA
  
  Alkali antimonide cathodes are critical both for high average current photoinjectors for energy recovery linacs and for high quantum efficiency photodetectors. These cathodes have historically been plagued by extreme vacuum sensitivity, non-reproducibility and poor lifetime. We report on ongoing efforts to improve the performance of alkali antimonides (principally K2CsSb). Cathodes have been fabricated which have a QE of 7% at 532 nm. The films are much more resistant to oxygen and water exposure than previously thought, with a 50% yield lifetime of 20 hrs at 2 pBar partial pressure of water. Several analysis techniques have been employed in this study, including in-situ x-ray diffraction during growth to measure grain size and texture, measurement of transverse momentum distribution of the emitted electrons, and measurement of the stoichiometry of the films via x-ray fluorescence. An extensive study of the growth parameters, including both transparent and metallic substrates, sputtered and evaporated films, variation of growth time and temperatures and post-growth annealing processes, is currently underway.  
 
THPS025 Overview of the Status and Developments on Primary Ion Sources at CERN ion, linac, plasma, proton 3472
 
  • R. Scrivens, M. Kronberger, D. Kuchler, J. Lettry, O. Midttun, M.M. Paoluzzi, H. Pereira, C. Schmitzer
    CERN, Geneva, Switzerland
  
  Funding: This project has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under the Grant Agreement no 212114.
CERN has 2 operational primary beam ion sources, that are presently used for the production of beam for LHC as well as several other facilities. Protons are produced by a duoplasmatron source, and ions from the GTS-LHC ECR ion source. In addition, new sources are required for a new 160MeV H− Linac, and development has been made on a high power RF plasma generator which could serve for a future high power Linac. In this report, the present status will be given, along with operational statistics and experience for the operation sources, and the development programme reported for the future sources. 		 
 
THPS027 Cesiation in Highly Efficient Surface Plasma Sources ion, plasma, brightness, ion-source 3478
 
  • V.G. Dudnikov, R.P. Johnson
    Muons, Inc, Batavia, USA
  
  Funding: Work supported in part by STTR grant DE-SC0002690.
Features of cesiation* in different modifications of H-/D- source designs have been considered. New sources under development include advanced versions of Compact Surface Plasma Sources (CSPS) which will efficiently generate brighter beam in noiseless discharge, deliver significantly increased (up to 20 mA) average current with better electrode cooling using new materials, have significantly extended lifetime and reduced cesium consumption. Related ion sources that use cesium are described and an improved cesiation procedure for reproducible production of high efficiency H− ion generation is considered.
* V. Dudnikov, SU Author Certificate, C1.H01 3/04, No. 411542, 10 March, 1972. 		 
 
THPS037 Performance Characteristics of HBC-foils by 650 KeV H− and DC High Intensity Ion Beam Irradiation ion, target, light-ion, heavy-ion 3502
 
  • I. Sugai, Y. Irie, H. Kawakami, M. Oyaizu, A. Takagi, Y. Takeda
    KEK, Ibaraki, Japan
  • M. Kinsho, Y. Yamazaki, M. Yoshimoto
    JAEA/J-PARC, Tokai-mura, Japan
  
  Newly developed Hybrid type Boron mixed Carbon stripper foils (HBC-stripper foil) are extensively used for not only J-PARC, for but also LANL-PSR since September of 2007. In order to know further characteristics of the HBC-stripper foils, we measured following parameters; foil lifetimes, thickness reduction, uniformity before and after beam irradiation and foil shrinkage, using 3.2 MeV Ne+ DC beam from TIT-Van de Grraff and 650 keV DC proton beam at KEK Cock-Croft accelerators, which are almost the same energy deposition as well as the J-PARC. We also investigated sputtering yield by hydrogen ion beam, thermal conductivity, weight change in heating and density of the HBC-stripper foils. We compared these values with other tested carbon stripper foils such as commercially available carbon foils (CM-foil), synthetic diamond (DM-foil) and nano-tube carbon foils (NTC-foil). Through these experiments, the　HBC-stripper foils showed superior performance characteristics, in especially, on the lifetime at temperature higher than 1800K compared with other tested CM-, DM- and NTC-foils.  
 
THPS048 Design of Electrostatic Septa and Fast Deflector for MedAustron septum, power-supply, synchrotron, injection 3532
 
  • J. Borburgh, T. Fowler, A. Prost
    CERN, Geneva, Switzerland
  • T. Kramer, T. Stadlbauer
    EBG MedAustron, Wr. Neustadt, Austria
  
  For the MedAustron facility, under construction in Wiener Neustadt, three electric field deflectors are developed in collaboration with CERN. A fast deflector is used in the Low Energy Beam Transfer line to chop the beam. The chopped beam is swept onto a Faraday cup for measurement purposes and to stop beam being sent towards the synchrotron. Electrostatic septa are used for the multi turn injection of protons and ions as well as for the slow extraction from the synchrotron. Novel design features for MedAustron include an inversed cathode/anode support and high voltage feedthroughs rated at 150 kV. The possibility for a higher voltage will significantly improve the conditioning process of the septa surfaces. This paper describes the requirements of these devices as well as the mechanical design and strategies adopted for their power supplies.