Keyword: cathode
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MOPEA021 Status of the HESR Electron Cooler Test Set-up electron, simulation, controls, vacuum 115
 
  • M.W. Bruker, K. Aulenbacher, J. Dietrich, S. Friederich, A. Hofmann, T. Weilbach
    HIM, Mainz, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
  
  For the proposed High Energy Storage Ring (HESR) at FAIR, it is foreseen to install an electron cooling device with a beam current of 3 A and a beam energy of 8 MeV. A test set-up was built at Helmholtz-Insitut Mainz (HIM) to conduct a feasibility study. One of the main goals of the test set-up is to evaluate the gun design proposed by TSL (Uppsala) with respect to vacuum handling, EM fields and the resulting beam parameters. Another purpose of the set-up is to achieve an energy recuperation efficiency of 1 - 10-5. To measure this quantity, a Wien filter has to be employed, which will also prove capable of mitigating collection losses. The current status of the project will be presented.  
 
MOPFI001 Characterization of a Superconducting Pb Photocathode in a SRF Gun Cavity laser, gun, cavity, electron 279
 
  • R. Barday, T. Kamps, O. Kugeler, A. Neumann, M. Schmeißer, J. Völker
    HZB, Berlin, Germany
  • P. Kneisel
    JLAB, Newport News, Virginia, USA
  • R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  • J. Smedley
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Bundesministerium für Bildung und Forschung and Land Berlin. The Pb deposition activity is supported by EuCARD.
Photocathodes are a limiting factor for the next generation of ultra-high brightness photoinjector driven accelerators. We studied the behavior of a superconducting Pb cathode in the cryogenic environment of a superconducting rf gun cavity related to the quantum efficiency, its spatial distribution and the work function. Cathode surface contaminations can modify the performance of the photocathodes as well as the gun cavity. We discuss the possibilities to remove these contaminations. 		 
 
MOPFI002 Results from Beam Commissioning of an SRF Plug-gun Cavity Photoinjector cavity, laser, emittance, gun 282
 
  • M. Schmeißer, R. Barday, A. Burrill, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, P. Lauinger, A. Neumann, J. Völker
    HZB, Berlin, Germany
  • P. Kneisel
    JLAB, Newport News, Virginia, USA
  • R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  • I. Will
    MBI, Berlin, Germany
  
  Superconducting rf photoelectron injectors (SRF guns) hold the promise to deliver high brightness, high average current electron beam for future lightsources or other applications demanding continuous wave operation of an electron injector. This paper discusses results from beam commissioning of a hybrid Pb coated plug-gun Nb cavity based SRF photoinjector for beam energies up to 3 MeV at Helmholtz-Zentrum Berlin. Emittance measurements and transverse phase space characterization with solenoid-scan and pepperpot methods will be presented.  
 
MOPFI003 SRF Photoinjector Cavity for BERLinPro cavity, SRF, gun, HOM 285
 
  • A. Neumann, W. Anders, A. Burrill, A. Frahm, T. Kamps, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  
  For the funded BERLinPro project, a 100 mA CW-driven SRF energy recovery linac, a SRF photoinjector cavity has to be developed which delivers a small emittance, 1 mm*mr, high brightness beam while accelerating a high average current within given high power limitations. To achieve these goals the injector is being developed in a three stage approach. In the current design step a cavity shape was developed which fulfills the beam dynamics requirements, implements a high quantum efficiency normal conducting photocathode with the HZDR choke and insert design and allows for beam studies at currents up to 4 mA. This paper will describe the RF design process, higher order mode studies and final mechanical calculations prior to the cavity production.  
 
MOPFI004 The Injector Layout of BERLinPro emittance, linac, cavity, gun 288
 
  • B.C. Kuske, M. Abo-Bakr, V. Dürr, A. Jankowiak, T. Kamps, J. Knobloch, P. Kuske, S. Wesch
    HZB, Berlin, Germany
  
  Funding: The Bundesministerium für Bildung und Forschung (BMBF) and the state of Berlin, Germany.
BERLinPro is an Energy Recovery Linac Project running since 2011 at the HZB in Berlin. The key component of the project is the 100mA superconducting RF photocathode gun under development at the HZB since 2010. Starting in 2016 the injector will go into operation providing 6 MeV electrons with an emittance well below 1mm mrad and bunches shorter than 4ps. 2017 the 50MeV linac will be set up and full recirculation is planned for 2018. The injector design including a dogleg merger has been finalized and is described in detail in this paper. Emphasis is laid on the final layout including collimators and diagnostics and performance simulations of two different gun cavities and first tolerance studies. 		 
 
MOPFI005 XPS and UHV-AFM Analysis of the K2CsSb Photocathodes Growth vacuum, electron, background, factory 291
 
  • S.G. Schubert
    HZB, Berlin, Germany
  • I. Ben-Zvi, M. Ruiz-Osés
    Stony Brook University, Stony Brook, USA
  • X. Liang
    SBU, Stony Brook, New York, USA
  • H.A. Padmore, T. Vecchione
    LBNL, Berkeley, California, USA
  • T. Rao, J. Smedley
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work is funded by the Department of Energy, under Contract No. KC0407-ALSJNT-I0013, DE-SC0005713, the Bundesministerium für Bildung und Forschung (BMBF) and the state of Berlin, Germany.
Next generation light sources, based on Energy Recovery Linac and Free Electron Laser technology will rely on photoinjector based electron sources. Successful operation of such sources requires reliable photocathodes with long operational life, uniform and high quantum efficiency, low thermal emittance and low dark current. The goal of this project is to construct a cathode which meets these requirements. Advances in photocathode research must take a combined effort. The materials have to be analyzed by means of chemical composition, surface structure and these findings have to be correlated to the quantum efficiency and performance in the injector. The presented work focuses on the chemical composition and surface structure of K2CsSb photocathodes. The XPS and AFM measurements were performed at the Center of Functional Nanomaterials at BNL. K2CsSb photocathodes were grown under UHV conditions. The components were adsorbed one at a time and after each growth step the corresponding XPS spectra was taken. During growth the quantum efficiency was recorded. As last step the sample was moved into the AFM without exposure to air to determine the surface roughness. 		 
 
MOPFI012 Measurement of Adsorption Rates of Residual Gases for NEA-GaAs Surface electron, ion, vacuum, emittance 306
 
  • M. Kuriki, H. Iijima, K. Miyoshi, K.U. Uchida
    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. The NEA surface is normally formed by a yo-yo technique in which cesium and oxygen are applied onto the surface alternately. Although the initial quantum efficiency is relatively larger than that of another cathode, the lifetime is shorter. The degradation with time elapsing even if the electron beam is not extracted is mainly caused by adsorption of residual gases in a vacuum chamber. We have evaluated the adsorption rates of various gases for the NEA surface by measuring the dark lifetime in sample gases such as hydrogen, carbon oxide and carbon dioxide.  
 
MOPFI013 A Lifetime Study of CsK2Sb Cathode laser, electron, vacuum, brightness 309
 
  • M. Kuriki, H. Iijima, K. Miyoshi, N. Norihito
    HU/AdSM, Higashi-Hiroshima, Japan
  
  Funding: Cooperative and Supporting Program for Researches and Educations in　Universities by High energy accelerator research organization (KEK)
CsK2Sb multi-alkali cathode is one of the candidates of robust and high efficiency cathode for high brightness electron source. CsKSb can be driven by green laser and it is a big advantage comparing to Cs2Te cathode which is widely used as a robust photo-cathode and driven by UV light. In Hiroshima University, a test chamber for CsK2Sb photo-cathode study is developed. In the chamber, CsK2Sb photo-cathode is formed by evaporation on SUS base plate. During the evaporation, amount is monitored by quartz meter. We devised good locations of the evaporation source, base plate, and thickness monitor, so that all evaporation processes for Cs, K, and Sb are under control. The base plate temperature is also controlled during the cathode formation. More than 2.0% quantum efficiency was achieved at the first activation test. The cathode lifetime was more than 200 hours and more than 20C in charge. The latest experimental result will be reported. 		 
 
MOPFI014 A Charge Lifetime Study of NEA GaAs Cathode by Ion Back-bombardment electron, ion, vacuum, simulation 312
 
  • M. Kuriki
    KEK, Ibaraki, Japan
  • L. Guo, H. Iijima, K. Miyoshi
    HU/AdSM, Higashi-Hiroshima, Japan
  
  Funding: Quantum beam project by the Ministry of Education, Culture, Sports, Science and Technology; The title is High Brightness Photon Beam by Laser-Compton Scattering.
NEA GaAs cathode is one of the most important techniques for advanced future projects based on linac. Up to 90% polarized beam can be generated with high quantum efficiency, 0.1 – 10%. The extremely low emittance beam can be generated driven by optimized wavelength laser. Although these remarkable features, the less robustness has been the biggest issue on the real operation of this cathode. According to past experiments, there are three sources of the cathode degradation; gas absorption, thermal desorption, and ion-back bombardment. First two processes could be controlled by less vacuum pressure in order of 10-10Pa and keeping the cathode temperature low. The ion back-bombardment is the last issue which should be solved for high brightness operation in such as ERL. We observed the cathode quantum efficiency evolution in various laser power density and bias voltage. We found that the cathode degradation was due to the ion back-bombardment quantitatively and the deactivation coefficient of NEA surface by one ion collision did not depend on the bias voltage. We report the experimental results and its analysis based on the ion back-bombardment hypothesis. 		 
 
MOPFI019 Beam Generation from a 500 kV DC Photoemission Electron Gun gun, electron, laser, high-voltage 321
 
  • N. Nishimori, R. Hajima, S.M. Matsuba, R. Nagai
    JAEA, Ibaraki-ken, Japan
  • Y. Honda, T. Miyajima, M. Yamamoto
    KEK, Ibaraki, Japan
  • H. Iijima, M. Kuriki
    HU/AdSM, Higashi-Hiroshima, Japan
  • M. Kuwahara
    Nagoya University, Nagoya, Japan
  
  Funding: This work is supported by MEXT Quantum Beam Technology Program and partially supported by JSPS Grants-in-Aid for Scientific Research in Japan (23540353).
The next generation light source such as X-ray FEL oscillator requires high brightness electron gun with megahertz repetition rate. We have developed a DC photoemission electron gun at JAEA for the compact energy recovery linac (cERL) light source under construction at KEK. This DC gun employs a segmented insulator with guard rings to protect the insulator from field emission generated from central stem electrode. We have successfully applied 500-kV on the ceramics with a cathode electrode in place and generated beam from the 500kV DC photoemission gun in October 2012. Details of the beam generation test will be presented. 		 
 
MOPFI023 Development of Better Quantum Efficiency and Long Lifetime Iridium Cerium Photocathode for High Charge electron RF Gun laser, electron, gun, linac 327
 
  • D. Satoh
    TIT, Tokyo, Japan
  • N. Hayashizaki
    RLNR, Tokyo, Japan
  • M. Yoshida
    KEK, Ibaraki, Japan
  
  We developed an Ir5Ce photocathode as a high charge electron source for SuperKEKB electron linac. The required electron beam parameters are 5 nC and 10 mm•mrad from the electron gun of the SuperKEKB electron linac. We plan to generate this electron beam using a laser-driven RF gun installed with a photocathode that has a long lifetime and a high-power laser system through more than a year without replacement. Therefore, we focused on the Ir5Ce compound as a new photocathode which has a high melting point (> 2100 K) and a low work function (2.57 eV). The results of measurements showed that the quantum efficiency of Ir5Ce photocathode was 1.0×10-4 treated by the laser cleaning using the 4nd harmonic of Nd:YAG laser or the heater treatment. Furthermore, its photoemission properties could be maintained for a long term even if its photocathode was in the low vacuum conditions ( ～10-6 Pa) since the Ir5Ce compound is far less contaminated than other photocathodes. Finally, We have succeed to generate electron beams of 4.4 nC by the Ir5Ce photocathode installed at the 3-2 sector DAW type RF gun and accelerate it through a linac end in KEK electron linac.  
 
MOPFI024 Ultra-short Electron Bunch Generation by an ECC RF Gun gun, electron, radiation, laser 330
 
  • Y. Koshiba, T. Aoki, M. Mizugaki, K. Sakaue, M. Washio
    Waseda University, Tokyo, Japan
  • T. Takatomi, J. Urakawa
    KEK, Ibaraki, Japan
  
  Funding: Work supported by JSPS Grant-in-Aid for Young Scientists (B) 23740203 and Scientific Research (A) 10001690
Energy Chirping Cell attached rf gun (ECC rf gun) is a photocathode rf gun specialized for ultra-short bunch generation. This ECC rf gun has been made with the collaboration of High Energy Accelerator Research Organization (KEK). Although the bunch length could be controlled by the laser pulse width, the bunch length ends up to be more than 1ps due to space charge effect when using a femto-second laser and a normal 1.6 cell cavity. Concerning this phenomenon, ECC is attached right after the 1.6 cell so that the electron bunch would be compressed after the electron bunch is accelerated around 5MeV. The roll of ECC is to chirp the energy with the linear part of the rf electric field. The electron bunch would be compressed by velocity difference as it drifts. Simulation results from PARMELA and GPT show that ECC rf gun can accelerate an 100pC bunch with the bunch length less than 100fs. We already manufactured this ECC rf gun and installed in our system. We demonstrated the ultra-short bunch by measuring the coherent THz light by synchrotron radiation and transition radiation. In this conference, we will report the results of ultra-short bunch generation experiments, and future plans. 		 
 
MOPFI036 Study of the Cold Cathode RF Electron Gun Based on Doped Diamond Films at CAEP gun, electron, FEL, emittance 366
 
  • X. Li
    TUB, Beijing, People's Republic of China
  • W. Bai, M. Li
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  
  Diamond relevant materials have been considered as a promising field emission cathode in recent years. High current density can be obtained either by diamond field emission arrays or by doped diamond films under electrical strengths of several decades of MV/m. Based on the doped films a half cell S-band electron gun has been designed and constructed at CAEP. The gun can provide an accelerating gradient of 60-80 MV/m on the cathode surface (6 mm in diameter). Simulations have proven good performance of such a gun but it needs confirmed by further experiments. Details of the experiments and comparisons with simulations will be reported.  
 
MOPFI037 Design and Experiment of a Compact C-band Photocathode RF Gun for UED gun, solenoid, emittance, electron 369
 
  • X.H. Liu, H.B. Chen, W.-H. Huang, C.-X. Tang, Z. Zhang
    TUB, Beijing, People's Republic of China
  
  A compact C-band photocathode RF gun for the MeV UED facility is developed in Tsinghua University, which is designed to work at the frequency of 5.712GHz. This paper presents the physics and RF structure design, and beam dynamics optimization of this C-band RF gun. 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. This paper likewise presents experiment parameters and the cold test results of this C-band RF gun.  
 
MOPFI058 Studies of Cs3Sb Cathodes for the CLIC Drive Beam Photoinjector Option gun, laser, electron, vacuum 413
 
  • I. Martini, E. Chevallay, S. Döbert, V. Fedosseev, C. Heßler, M. Martyanov
    CERN, Geneva, Switzerland
  
  Within the CLIC (Compact Linear Collider) project, feasibility studies of a photoinjector option for the drive beam as an alternative to its baseline design using a thermionic electron gun are on-going. This R&D program covers both the laser and the photocathode side. Whereas the available laser pulse energy in ultra-violet (UV) is currently limited by the optical defects in the 4th harmonics frequency conversion crystal induced by the 0.14 ms long pulse trains, recent measurements of Cs3Sb photocathodes sensitive to green light showed their potential to overcome this limitation. Moreover, using visible laser beams leads to better stability of produced electron bunches and one can take advantages of the availability of higher quality optics. The studied Cs3Sb photocathodes have been produced in the CERN photoemission laboratory using the co-deposition technique and tested in a DC gun set-up. The analysis of data acquired during the cathode production process will be presented in this paper, as well as the results of life-time measurements in the DC gun.  
 
MOPFI062 Optimization Studies for the SwissFEL RF-Gun gun, laser, emittance, solenoid 425
 
  • M. Schaer, A. Adelmann, A. Anghel, S. Bettoni, P. Craievich, L. Stingelin, C. Vicario, R. Zennaro
    PSI, Villigen PSI, Switzerland
  • Z. Zhang
    TUB, Beijing, People's Republic of China
  
  The 250 MeV SwissFEL injector test facility is in operation since August 2010. Measurements with the "CTF2 Gun 5" photocathode S-band rf-gun show promising beam parameters and satisfy the requirements of the SwissFEL project. Since the performance of the electron source is fundamental for the stability and brightness of a free electron laser, further gun optimization studies are pursued. Under investigation is currently a 3.6 cell C-band gun. First ASTRA simulations indicate that with this gun the peak-current can be increased, thanks to a shorter laser pulse and a higher initial acceleration, by almost a factor of two, at slightly better emittance values than the S-band "PSI Gun 1". Since the beam-quality depends also on the achieved performance of the cathode, several copper cathodes had been tested in the SwissFEL injector test facility to analyze the observed rapid degradation of quantum efficiency.  
 
MOPFI066 An Ultra-Low Energy Electron Beam Ion Trap in Shanghai electron, ion, plasma, injection 434
 
  • J. Xiao, R. Hutton, X. Jin, D. Lu, B. Tu, Y. Yang, R. Zhao, Y. Zou
    Fudan University, Shanghai, People's Republic of China
  
  Electron beam ion traps (EBITs) are very useful tools for disentanglement studies of atomic processes in plasmas. In this paper, a new ultra-low energy EBIT, SH-HtscEBIT, is reported. This EBIT can operate in the electron energy range of 30–4000 eV, with a current density of up to 100 A/cm2. The low energy limit of this machine is 30 eV, which is the lowest energy among the EBITs around the world. The maximum magnetic field in the central drift tube region of this EBIT is around 0.25 T, produced by a pair of high temperature superconductor coils. This EBIT is set up for the purpose of disentangling spectroscopic studies of edge plasmas relevant to magnetic fusion devices, and of astro-plasmas. All the elements for the spectroscopic studies can be injected through an injection system. Both the design and the performance of this EBIT are presented.  
 
MOPFI068 High Repetition Rate Highly Stable S-band Photocathode Gun for the CLARA Project gun, cavity, laser, electron 437
 
  • B.L. Militsyn, L.S. Cowie, P. Goudket, S.P. Jamison, J.W. McKenzie, K.J. Middleman, R. Valizadeh, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • V.V. Paramonov
    RAS/INR, Moscow, Russia
  • M.D. Roper
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  Compact Linear Accelerator for Research and Applications (CLARA) is a 250 MeV electron facility which is under development at STFC ASTeC. The CLARA photo-injector is based on a RF photocathode gun operating with metal photocathodes and driven by a third harmonic of Ti: Sapphire laser (266 nm). The injector will be operated with laser pulses with an energy of up to 2 mJ, pulse durations down to 180 fs FWHM and a repetition rate of up to 400 Hz. In order to investigate performance of different photocathodes the gun is equipped with a load-lock system which would allow replacement of the photocathodes. Duration and emittance of electron bunches essentially depends on the mode of operation and vary from 0.1 ps at 20 pC to 5 ps at 200 pC and from 0.2 to 2 mm mrad respectively. Requirements for the stability of beam arrival time at the CLARA experimental area are extremely high and vary from hundreds down to tenths femtoseconds. In the presented article we analyse stability of the guns with 1.5 and 2.5 cell and the beam quality delivered by a gun with coaxial and waveguide coupler and analyse possibility of injection time stabilisation with low level RF and optical feedback system.  
 
MOPFI069 Preparation of the Polycrystalline Copper Photocathodes for the VELA RF Photocathode Gun plasma, gun, ion, electron 440
 
  • R. Valizadeh, A.N. Hannah, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes, R.N.C. Santer
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • M.D. Roper
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  The Electron Beam Test Facility (EBTF) is a high performance electron source under commissioning at ASTeC. The photoinjector of the source is based on a S-band photocathode RF gun operating with a copper photocathode which is driven by a third harmonic of Ti: Sapphire laser (266 nm). The photocathode used in the RF gun is an integrated part of the gun cavity which is polycrystalline copper disk, polished to 1um roughness, and is placed at the back wall of the first 0.5 cell in the gun cavity. In order to accomplish a procedure to activate surface prior installation, copper test samples with roughness of 0.1 um were prepared by different techniques. The best results have been obtained by ex-situ plasma cleaning in an oxygen atmosphere. Analyses showed that there was no carbon on the surface and the surface was composed of copper oxide. After heating the sample in-situ to 220 C for almost all the surface oxide was removed. For this surface a QE of 2 x10-5 was measured. Further heating to higher temperature did not result in any improvement either in surface composition nor a noticeable increase in QE. Prepared such a way operational photocathode is now under commissioning in the gun.  
 
MOPFI076 Electron Emission Studies in the New High-charge Cs2Te Photoinjector at Argonne National Laboratory gun, laser, wakefield, factory 455
 
  • E.E. Wisniewski, M.E. Conde, W. Gai, C.-J. Jing, W. Liu, J.G. Power
    ANL, Argonne, USA
  • L.K. Spentzouris, Z.M. Yusof
    Illinois Institute of Technology, Chicago, Illinois, USA
  
  Funding: This work was funded by the U.S. Dept. of Energy Office of Science under contract number DE-AC02-06CH11357.
A new L-band 1.3 GHz 1.5 cell gun for the new 75 MeV drive beam is being commissioned and will soon be operating at the Argonne Wakefield Accelerator (AWA) facility as part of the facility upgrade (see M. E. Conde, this proceedings.) The photoinjector is high-field (peak accelerating field > 80MV/m) and has a large \mathrm{Cs}2\mathrm{Te} photocathode (diameter > 30 mm) fabricated in-house. The photoinjector generates high-charge, short pulse, single bunches (Q > 100 nC) or bunch-trains (Q ≈ 1000 nC) for wakefield experiments. Field emission from the \mathrm{Cs}2\mathrm{Te} cathode is to be measured during RF conditioning and benchmarked against measurements from a copper cathode. Quantum efficiency (QE) will be measured in single and multi-bunch modes. Preliminary results are presented. 		 
 
MOPFI080 Fabrication, Transport and Characterization of Cesium Potassium Antimonide Cathode in Electron Guns gun, laser, vacuum, SRF 461
 
  • T. Rao, S.A. Belomestnykh, I. Ben-Zvi, X. Liang, I. Pinayev, B. Sheehy, J. Skaritka, J. Smedley, E. Wang, T. Xin
    BNL, Upton, Long Island, New York, USA
  • R.R. Mammei, J.L. McCarter, M. Poelker
    JLAB, Newport News, Virginia, USA
  • M. Ruiz-Osés
    Stony Brook University, Stony Brook, USA
  
  a number of accelerator applications need high current, low emittance and high brightness electron beams. Recent studies have shown cesium potassium antimonide to be a robust photocathode capable of producing high peak and average currents. However, for some applications, the UHV conditions required for producing these cathodes necessitate their fabrication site to be physically removed from the gun location and the cathode to be transferred between the two sites in UHV load-lock chambers. We have fabricated two cathodes at BNL, transported and tested them in DC gun at JLab at 100 kV and 200 kV. These cathodes have delivered up to 8A/cm2 without significant degradation. Localized changes in the QE have been attributed to heating due to laser, increasing the QE at lower laser power, but damaging the cathode at higher power. Two more load-lock chambers have been built to transport and insert similar cathodes in SRF guns operating at 700 MHz and 112 MHz for the first time. In this paper, we will describe the design of the load-lock chambers, transfer mechanisms, transport of the cathodes over ~ 1000 km and the cathode performance in gun environment.  
 
MOPFI081 Correlating Structure and Function - In situ X-ray Analysis of High QE Alkali-antimonide Photocathodes scattering, emittance, controls, vacuum 464
 
  • J. Smedley, K. Attenkofer, S.G. Schubert
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi, X. Liang, E.M. Muller, M. Ruiz-Osés
    Stony Brook University, Stony Brook, USA
  • T. Forrest, H.A. Padmore, T. Vecchione, J.J. Wong
    LBNL, Berkeley, California, USA
  • J. Xie
    ANL, Argonne, USA
  
  Funding: The authors wish to acknowledge the support of the US DOE, under Contract No. KC0407-ALSJNT-I0013, DE-AC02-98CH10886 and DE-SC0005713. Use of CHESS is supported by NSF award DMR-0936384.
Alkali antimonide photocathodes have high quantum efficiency and low emittance when illuminated by visible light, and are thought to be well suited for use in high-brightness photoinjectors of 4th generation light sources. Here we report on the growth of multi-alkali K2CsSb cathodes on [100] silicon substrates measured using in-situ X-ray diffraction (XRD) and X-ray reflection (XRR). Correlations between cathode structure and growth parameters and the resulting quantum efficiency (QE) are also explored. The best cathodes have a QE at 532 nm in excess of 6% and are structurally textured K2CsSb with grain sizes in excess of 20 nm. In an attempt to reduce the complexity of the current growth methodology we are also making alkali antimonides in parallel via the reaction of bulk materials in an inert environment. This approach has the advantage that the desired stoichiometry can be obtained exactly. Initial diffraction results from prepared bulk materials are promising and show the formation of well reacted K3Sb. In the future we intend to transfer this material to smooth thin photocathode films by either sputtering or pulsed laser deposition. 		 
 
MOPME036 Prototype Experiment Preparation of a 54.167MHz Laser Wire System for FEL-THz Facility at CAEP laser, electron, photon, FEL 550
 
  • D. Wu
    TUB, Beijing, People's Republic of China
  • W. Bai, M. Li, H. Wang, J. Wang, X. Yang
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  
  In this paper, a prototype experiment preparation of a 54.167 MHz laser wire system is presented, which will be used to measure the beam size of a CW DC gun built as an electron source of FEL-THz facility in China Academmy of Engineering Physics (CAEP). The rms beam size is less than 1 mm and the average current of the electron beam is more than 1 mA. This new-type LW system ultilizes the excess power other the photocathode drive laser and becomes much cheaper and simpler. Plus, it can distinguish beams with different energies which are very close in ERLs. The system layout and the simulation results are also presented.  
 
MOPWA036 GEM Detectors for the Transverse Profile Measurement of Low Energy Antiprotons and High Energy Hadrons antiproton, electron, hadron, scattering 747
 
  • J. Spanggaard, P. Carriere, S.C. Duarte Pinto, G. Tranquille
    CERN, Geneva, Switzerland
  
  Gas Electron Multipliers (GEM) are finding more and more applications in beam instrumentation. Gas Electron Multiplication is a very similar physical phenomenon to that which occurs in Multi Wire Proportional Chambers (MWPC), but for small profile monitors GEMs are much more cost effective to produce and maintain. In 2012, all Multi-Wire Proportional Chambers in the experimental areas of the Antiproton Decelerator at CERN were successfully replaced by Gas Electron Multipliers. This paper describes the choice of detector and reports on the commissioning of 20 GEM detectors for transverse profile measurement on low energy antiproton beams (5.3 MeV, equal to 100 MeV/c). It will also cover the development of, and first results from, a new 200x200 mm GEM detector for profiling the high energy muon beam (172 GeV/c) delivered to the COMPASS experiment and discuss the outlook for replacing all Multi-Wire Proportional Chambers in the CERN experimental areas by GEM based monitors.  
 
MOPWA066 Components of Heating and Fueling of Fusion Plasmas high-voltage, simulation, controls, synchrotron 831
 
  • K. Schrock, M.P.J. Gaudreau, M.K. Kempkes
    Diversified Technologies, Inc., Bedford, Massachusetts, USA
  
  Funding: Funded by US DOE, Grant # DE-SC0004250
Next generation fusion facilities will require many megawatts of RF power from dozens of gyrotrons. Each gyrotron requires a power system that must deliver the high-voltage power, modulate cathode voltage, and protect these expensive gyrotrons from arcing damage. It must be highly efficient, to minimize both the power and cooling costs associated with operation and to ensure high facility availability. Diversified Technologies, Inc. (DTI) has bench-tested a table-top scale ‘Buck Matrix’ modulator which uses a single set of IGBT switches for voltage regulation, arc protection, and pulse modulation. Although pulse step modulators represent a one-step solution, their size, and the complexity of their driving transformer make them more expensive than DTI’s two-step approach. DTI’s Buck Matrix modulator, with an efficiency of ~96%, cuts the size of the system in half, using a single layer of solid state switches for both voltage regulation and arc protection/modulation. This cuts the total hardware costs by a~30% or more, and eliminates the need for a separate opening switch or crowbar. DTI will present the system components of the design as well as the performance results to date. 		 
 
TUOCB103 Quasi Traveling Wave Side Couple RF Gun for SuperKEKB gun, cavity, emittance, focusing 1117
 
  • T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou
    KEK, Ibaraki, Japan
  
  We are developing a new RF gun for SuperKEKB. High charge low emittance electron and positron beams are required for SuperKEKB. We will generate 7.0 GeV electron beam at 5 nC 20 mm-mrad by J-linac. In this linac, a photo cathode S-band RF gun will be used as the electron beam source. For this reason, we are developing an advanced RF gun. We have tested a Disk and Washer (DAW) type RF gun. Additionally, another new RF gun which has two side coupled standing wave field is developed. We call it quasi traveling wave side couple RF gun. This gun has a strong focusing field at the cathode and the acceleration field distribution also has a focusing effect. The design of RF gun and experimental results will be shown.  
slides icon Slides TUOCB103 [2.959 MB]  
 
TUODB202 Experiment and Numerical Simulation Results of Plasma Window plasma, simulation, vacuum, cavity 1155
 
  • K. Zhu, S. Huang, Y.R. Lu, B.L. Shi
    PKU, Beijing, People's Republic of China
  
  Funding: Supported by NSFC 91026012
A windowless vacuum seal technique has been widely researched and designed, which can connect high pressure cavity to a vacuum condition with rather little thickness of material. As a result, it will reduce most interaction with the particle beam penetrating through comparing to that of foil window. It is desired extensively in experiments using high-intensity heavy ion beams which will break foil window in a short time or in experiments which require the injecting beams with mono-energy and high purity for example. In this work, we study the plasma window in argon which is used as a windowless vacuum sealing device. A numerical 2D FLUENT-based magneto-hydrodynamic model has been developed to investigate the physical reasons of high pressure difference in plasma window. Further, preliminary experimental results are presented and discussed. 		 
slides icon Slides TUODB202 [2.180 MB]  
 
TUPEA003 Components for CW and LP Operation of the XFEL Linac cavity, cryomodule, linac, HOM 1164
 
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  
  The European XFEL will use superconducting TESLA cavities operating with 650 μs long bunch trains. With 220 ns bunch spacing and 10 Hz RF-pulse repetition rate, up to 27000 high quality bunches/s will be delivered to insertion devices generating unprecedented high average brilliance photon beams at very short wavelength. While many experiments can take advantage of full bunch trains, others prefer an increased intra-pulse distance of several μ-seconds between bunches, or short bursts with a kHz repetition rate. In this contribution, we discuss progress in the R&D program for a future upgrade of the European XFEL linac, to operation in the continuous wave (cw) and long pulse (lp) mode, which will allow for much more flexibility in the electron and photon beam time structure. Modifications and cw tests of XFEL cryomodules, recent tests result of the SRF injector, test of the second prototype of 120 kW IOT are presented. In addition, computer modeling of the cw-operating TESLA-like cavity with modified HOM couplers is briefly discussed.  
 
TUPEA060 Jitter Tolerance for CLARA linac, laser, electron, FEL 1271
 
  • B.P.M. Liggins, J.K. Jones, J.W. McKenzie, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • J.K. Jones, B.P.M. Liggins, J.W. McKenzie, P.H. Williams
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  Funding: Science & Technology Facilities Council
CLARA (Compact Linear Accelerator for Research and Applications) at Daresbury Laboratory will be a test-bed for novel FEL configurations. CLARA will consist of an RF photoinjector, S-band acceleration and transport to 250 MeV including X-band linearisation and magnetic bunch compression. Ensuring stability of the VUV radiation pulses is a key aim of the project. To this end, we investigate in detail the jitter tolerance of the machine. This will ultimately determine the pulse stability. 		 
 
TUPWO060 Flat Electron Bunch Compression at the Advanced Superconducting Test Accelerator emittance, quadrupole, simulation, solenoid 2003
 
  • C.R. Prokop, D. Mihalcea, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
  • P. Piot, Y.-E. Sun
    Fermilab, Batavia, USA
  
  Funding: This work is supported by LANL LDRD #20110067DR and by the U.S. DOE contracts DE-FG02-08ER41532 and DE-AC02-07CH11359.
The generation of flat beam using round-to-flat beam conversion of an incoming canonical-angular-momentum dominated electron beam could have important application in the field of advanced acceleration techniques and accelerator-based light source. In this paper we explore the temporal compression of flat beams and especially compare the resulting phase space dilutions with the case of round beam. Finally, we propose and detail a possible experiment to investigate the flat-beam bunch compression at the Advanced Superconducting Test Accelerator currently in construction at Fermilab. 		 
 
WEPWA024 Study of an Electron Gun for Terahertz Radiation Source gun, electron, focusing, radiation 2184
 
  • J. Li, C. Li, Y.J. Pei, L. Shang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • Q.S. Chen, T. Hu
    HUST, Wuhan, People's Republic of China
  • G. Feng
    DESY, Hamburg, Germany
  
  With the aim to obtain short-pulse bunches with high peak current for a terahertz radiation source, an RF gun with independently tunable cells (ITC) was employed. As the electron source of the ITC RF gun, a grid-control DC gun plays a key role, the performance of which determines the beam quality in the injector and transport line. In order to make the beam well compressed in the ITC RF gun, the energy of the electrons acquired from the grid-control DC gun should be 15 KeV at most. A proper structure of the grid-gun is shown to overcome the strong space charge force on the cathode, which is able to generate 1us beam with 4.5A current successfully. Simulations considering the grid net are also introduced.  
 
WEPWA040 Options for PAL-XFEL Injector Operation emittance, laser, gun, FEL 2217
 
  • J.H. Han
    PAL, Pohang, Kyungbuk, Republic of Korea
  • M.S. Chae
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  
  Present designs of the PAL-XFEL injector assume a 120 MV/m peak field at the cathode in the gun and a flat-top longitudinal drive-laser profile. As accelerating field in the gun decreases and laser shape becomes imperfect, beam quality degradation takes place. On the other hand, by reducing accelerating field in the gun and by relaxing drive-laser shaping requirement the stability of the injector can be increased. We study various options for operating conditions of the injector with relaxed RF and drive-laser parameters.  
 
WEPWA058 Operation of the NSRRC 2998 MHz Photo-cathode RF Gun gun, laser, electron, cavity 2247
 
  • A.P. Lee, M.C. Chou, J.-Y. Hwang, W.K. Lau
    NSRRC, Hsinchu, Taiwan
  • P. Chiu, N.Y. Huang, P. Wang
    NTHU, Hsinchu, Taiwan
  
  We are developing the photoinjector technology for single pass high gain FEL research at NSRRC. A gun test facility(GTF) equipped with a 35 MW, S-band high power pulsed klystron as well as a 300 uJ, UV driver laser has been constructed for testing photo-cathode rf guns. Recently, a 2998 MHz, 1.6-cell photo-cathode rf gun has been fabricated in house and is being tested at the NSRRC GTF. Details of this setup will be described and the operational performance of this electron gun will be reported.  
 
WEPWA059 Operation of the Drive Laser System for the 2998 MHz NSRRC Photoinjector laser, gun, electron, target 2250
 
  • M.C. Chou, W.K. Lau, A.P. Lee
    NSRRC, Hsinchu, Taiwan
  
  A 266nm UV laser system has been installed as the drive laser of the NSRRC 2998 MHz photo-cathode rf gun. We will report our experiences on using such laser system for rf gun beam test. UV optics for laser beam transport as well as shaping technique we used for emittance preservation will also be presented.  
 
WEPWA061 ALICE ERL Intra-train Variation Investigation using Bunch-by-bunch BPMs laser, FEL, linac, gun 2256
 
  • D. Angal-Kalinin, F. Jackson, S.P. Jamison, J.K. Jones, A. Kalinin, T.T. Thakker, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  The ALICE ERL is an energy recovery test facility based at Daresbury Laboratory. We present investigations of charge and transverse variations/oscillations in the ALICE trains (up to 1600 bunches, spacing 55.2ns, bunch charge up to 60pC), using turn-by-turn EMMA BPMs adjusted for bunch-by-bunch measurements*. A set-up was established which allows use of pickups immediately downstream of the DC Gun as well as in the Arcs. To analyse variations, a DFT was used. It was established that a previously observed prominent (~10%) 300kHz charge envelope variation is a feature of the Photoinjector Laser. A set of transverse variations at 300kHz and below that depended on steering was also observed in the Injection Line. Downstream of the Booster, it was discovered that the transverse spectra are different. Prevailing quite regular variations (in range of 50um) were observed around 100kHz, manifesting themselves in the horizontal plane, present in non-dispersive regions, and dependent on trajectory offset in the Booster. We discuss the results, and also present our plans to apply this technique to a new single bunch injector EBTF now under commissioning in Daresbury Laboratory.
* A. Kalinin et al, MOPA30, IBIC12, Tsukuba, Japan. 		 
 
WEPWA091 Simulation Design of a Low Energy Bunch Compressor with Space Charge Effect space-charge, gun, electron, dipole 2307
 
  • A. He, Y. Hidaka, T.V. Shaftan, G.M. Wang, F.J. Willeke, L. Yang, L.-H. Yu
    BNL, Upton, Long Island, New York, USA
  
  Funding: Department of Energy, USA
Following the proposal of electron beam slicing method to generate short x-ray pulses in storage ring, we studied the feasibility of the crucial technique required by electron beam slicing, i.e., the generation of very low energy electron beam with very small beam size (30 μm) and very short bunch length (100 fs). Based on one of the BNL RF gun, 5 MeV beam energy and 50 pC bunch charge was assumed in the study. The beam ‘natural’ energy-time negative chirp, due to space charge effect, was used and the bunch length is compressed from from 0.8 ps to ~150 fs with a chicane structure. The system is in the space charge dominated regime. We use the code PARMELA and Generic optimization method for parameters optimization with various strategies to overcome the damaging from the space charge effect. After optimization, the beam transverse size is 50 micron and the bunch length is 150 fs, close to our original specification. In this paper we describe the design and the physical process in the compressor and focus section. The study confirmed the possibility to generate strong focused and compressed very low energy beam in the space charge dominated regime. 		 
 
WEPWO002 RF Measurements of the 1.6 Cell Lead/Niobium Photoinjector in HoBiCaT cavity, gun, vacuum, SRF 2313
 
  • A. Burrill, W. Anders, T. Kamps, J. Knobloch, O. Kugeler, P. Lauinger, A. Neumann
    HZB, Berlin, Germany
  • P. Kneisel
    JLAB, Newport News, Virginia, USA
  • R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  
  The development of a simple and robust SRF photoinjector capable of delivering up to 1 mA average current in c.w. operation continues to progress with the horizontal RF testing of the 1.6 cell Pb/Nb hybrid photoinjector. This injector utilizes a sputtered lead coating on a removable Nb cathode plug as the photoelectron source and has recently been tested in the horizontal test cryostat facility, HoBiCaT, at HZB. In this paper we will report on the status of these RF measurements and compare the performance to previous vertical RF tests performed at JLab. We will also report on the experience operating this cavity with a TTF-III high power RF input coupler, as well as provide a summary of the microphonics susceptibility now that it has been installed into a helium vessel and equipped with a Saclay style tuner.  
 
WEPWO007 Shape Optimization of a SRF Injector Cavity emittance, cavity, solenoid, electron 2322
 
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  • W.C. Grabowski, R. Nietubyć, T. Wasiewicz
    NCBJ, Świerk/Otwock, Poland
  
  In this contribution we present studies on the shape optimization of 1.6-cell cavity with solenoid for a 1-mA class photo injector, meant as an electron source for FEL facilities. The main criterion for the optimization was the lowest slice emittance. Inclination angle of the cavity back wall, solenoid position and magnetic field, amplitude of the accelerating field, and emission phase were varied in these studies in order to find the minimum of slice emittance at the distance of 1 m from a photocathode, located in center of the cavity back wall  
 
WEPWO009 Numerical Coupling Analyses of BERLinPro SRF Gun cavity, gun, simulation, SRF 2328
 
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  • W. Anders, A. Burrill, T. Kamps, J. Knobloch, O. Kugeler, A. Neumann
    HZB, Berlin, Germany
  
  BERLinPro is an approved ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity (1300 MHz, β=1) for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.8 MeV kinetic energy while limited by fundamental power coupler performance to about 230 kW forward power. The RF and beam dynamics gun cavity features 1.4 λ/2 cell resonator. We present results of mechanical structure developments of SRF gun. The main purpose of the whole structure optimization was the design of the gun helium vessel together with the tuner and stiffening rings to provide the simple construction for structure tuning with minimization of the cavity frequency dependence on external pressure. During the resonator tuning and external load structure deformations the cavity field profile variation along the beam path should stay within 5%.  
 
WEPWO061 Readiness for the Cornell ERL emittance, cavity, linac, laser 2447
 
  • G.H. Hoffstaetter, A.C. Bartnik, I.V. Bazarov, D.H. Bilderback, M.G. Billing, J.D. Brock, J.A. Crittenden, L. Cultrera, D.S. Dale, J. Dobbins, B.M. Dunham, R.D. Ehrlich, M. P. Ehrlichman, R. Eichhorn, K. Finkelstein, E. Fontes, M.J. Forster, S.J. Full, F. Furuta, D. Gonnella, S.W. Gray, S.M. Gruner, C.M. Gulliford, D.L. Hartill, Y. He, R.G. Helmke, K.M.V. Ho, R.P.K. Kaplan, S.S. Karkare, V.O. Kostroun, H. Lee, Y. Li, M. Liepe, X. Liu, J.M. Maxson, C.E. Mayes, A.A. Mikhailichenko, H. Padamsee, J.R. Patterson, S.B. Peck, S. Posen, P. Quigley, P. Revesz, D.H. Rice, D. Sagan, J. Sears, V.D. Shemelin, D.M. Smilgies, E.N. Smith, K.W. Smolenski, A.B. Temnykh, M. Tigner, N.R.A. Valles, V. Veshcherevich, A.R. Woll, Y. Xie, Z. Zhao
    CLASSE, Ithaca, New York, USA
  
  Funding: Supported by NSF award DMR-0807731 and NY State
Energy-Recovery Linacs (ERLs) are proposed as drivers for hard x-ray sources because of their ability to produce electron bunches with small, flexible cross sections and short lengths at high repetition rates. Cornell University has pioneered the design and hardware for ERL lightsources. This preparatory research for ERL-lightsource construction will be discussed. Important milestones have been achieved in Cornell's prototype ERL injector, including the production of a prototype SRF cavity that exceeds design specifications, the regular production of long-lived and low emittance cathodes, the acceleration of ultra-low emittance bunches, and the world-record of 65 mA current from a photoemission DC gun. We believe that demonstration of the practical feasibility of these technologies have progressed sufficiently to allow the construction of an ERL-based lightsource like that described in [erl.chess.cornell.edu/PDDR]. 		 
 
WEPFI024 Anisotropic Ferrite Magnet Focusing System for Klystrons klystron, focusing, permanent-magnet, simulation 2756
 
  • Y. Fuwa, H. Ikeda, Y. Iwashita, R. Kitahara, Y. Nasu, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • S. Fukuda, T. Matsumoto, S. Michizono
    KEK, Ibaraki, Japan
  
  The permanent magnet beam focusing for klystrons can eliminate the solenoid coil with the water cooling system and the power supply that consumes electricity. Hence the failure rate and the operating cost of RF systems should decrease. This feature is suitable for a large facility that requires a lot of klystrons such as ILC. Since the required magnetic field for klystron beam is moderate, inexpensive anisotropic ferrite magnets can be applied. The test model is fabricated for a 1.3 GHz klystron whose output power is 800 kW. Each magnet block in the model is movable for magnetic field adjustment and the iron yoke in the oil tank improves magnetic field distribution around cathode area. The result of a klystron power test will be presented.  
 
WEPFI030 Design Studies on NSC KIPT Electron Gun System gun, electron, high-voltage, power-supply 2768
 
  • Z.S. Zhou, Y.L. Chi, D.Y. He
    IHEP, Beijing, People's Republic of China
  
  In NSC KIPT, a neutron source based on a subcritical assembly driven by a 100MeV/100kW electron linear accelerator is under design and development. The linear accelerator needs a new high current electron gun. In this paper, physical design, mechanical fabrication and beam test of this new electron gun are described. The emission current is designed to be higher than 2A for the pulse width of 3us with repetition rate of 50 Hz. The gun will operate with a DC high voltage power supply which can provide up to 150 kV high voltages. Computer simulations and optimizations have been carried out in the design stage, including the gun geometry and beam transport line. The test results of high voltage conditioning and beam test are presented. The operation status of the electron gun system is also included. The basic test results show that the design, manufacture and operation of the new electron system are basically successful.  
 
WEPFI062 Precise Cavity Tuning System of a Low Output-impedance Second-harmonic Cavity at ISIS cavity, impedance, resonance, beam-loading 2836
 
  • Y. Irie, S. Fukumoto, K. Muto, H. Nakanishi
    KEK, Ibaraki, Japan
  • D.B. Allen, D. Bayley, N.E. Farthing, I.S.K. Gardner, R.J. Mathieson, A. Seville, J.W.G. Thomason
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf
    ANL, Argonne, USA
  
  A very low output-impedance (~35ohms) second-harmonic cavity system is being developed for high intensity proton accelerators. The final amplifier is comprised of a grounded cathode scheme with a feedback loop from anode to grid. Due to the Miller effect, the grid voltage waveform is seriously distorted even if only a few percent of sub-harmonic or higher harmonic are mixed in the generator current. Such distortion is much enhanced by the beam loading. In order to eliminate the effect of this distortion upon the phase detector used to achieve precise cavity tuning, a swept bandpass filter was applied to the grid voltage at the phase detector input. Filter design details and the result of high power tests are reported.  
 
WEPFI072 Analysis of Breakdown Damage in an 805 MHz Pillbox Cavity for Muon Ionization Cooling R&D cavity, site, plasma, radiation 2857
 
  • D.L. Bowring, D. Li
    LBNL, Berkeley, California, USA
  • A. Moretti, Y. Torun
    Fermilab, Batavia, USA
  
  When operating in multi-Tesla solenoidal magnetic fields, normal-conducting cavities exhibit RF breakdown at anomalously low gradients. This breakdown behavior may be due to field-emitted electrons, focused by the magnetic field into "beamlets" with relatively large current densities. These beamlets may then cause pulsed heating and cyclic fatigue damage on cavity interior surfaces. If this model is correct, materials with long radiation lengths (relative to copper) may alleviate the problem of RF breakdown in strong magnetic fields. To study this phenomenon, RF breakdown was induced on pairs of "buttons" in an 805 MHz pillbox cavity. The shape of the buttons creates a local enhancement of the surface electric field, such that breakdown occurs preferentially on the button surface. Beryllium and copper buttons were tested in order to evaluate the effect of radiation length on RF breakdown performance. This poster presents an analysis of the damage to these buttons and suggests a path forward for future materials R&D related to breakdown in strong magnetic fields.  
 
WEPFI077 LLNL X-band Test Station Status gun, alignment, emittance, vacuum 2872
 
  • R.A. Marsh, F. Albert, G.G. Anderson, S.G. Anderson, C.P.J. Barty, E.T. Dayton, S.E. Fisher, D.J. Gibson, F.V. Hartemann, S.S.Q. Wu
    LLNL, Livermore, 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
In support of Compton scattering gamma-ray source efforts at LLNL, a multi-bunch test station is being developed to investigate accelerator optimization for future upgrades. This test station will enable work to explore the science and technology paths required to boost the current mono-energetic gamma-ray technology a higher effective repetition rate, potentially increasing the average gamma-ray brightness by two orders of magnitude. The test station will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. Detailed design of the test station including is complete, and will be presented with modeling simulations and future upgrade paths. The current status of the installation will also be discussed with future commissioning plans. 		 
 
WEPFI078 LLNL X-band RF System klystron, high-voltage, vacuum, gun 2875
 
  • R.A. Marsh, G.G. Anderson, S.G. Anderson, C.P.J. Barty, S.E. Fisher, D.J. Gibson, F.V. Hartemann
    LLNL, Livermore, 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 test station is being developed at LLNL to investigate accelerator optimization for future upgrades to mono-energetic gamma-ray technology at LLNL. The test station will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. The high power RF for the test station will be provided by a SLAC XL4 11.424 GHz klystron driven by a ScandiNova solid state modulator. The high power system has been installed and results of initial testing into high power loads will be presented. Performance of the system with respect to processing and stability will be discussed as well as future plans for the low level RF system. 		 
 
WEPFI082 Double-tip Magnetic Field Enhancement simulation, cavity, vacuum, electron 2887
 
  • F.Y. Wang, L. Xiao
    SLAC, Menlo Park, California, USA
  
  The local electric field enhancement factor β in an rf accelerator cavity has been studied experimentally for decades and found to be in the range from few tens up to few hundreds for various rf frequencies and materials. A large field enhancement factor is usually thought to come from sharp tips whose β is roughly the ratio of their height to their tip radius. For a β of few hundred, the corresponding tip height would need to be more than 10 microns, which should be visible in a scanning electron microscope (SEM). However, the estimated β from SEM images of cavity surfaces is around 10. Therefore, the physics of such large β values is still not clear. In this paper, we have studied differentμstructures and found that the magnetic field could be enhanced many times in the presence of two nearby tips with β of 10. The large local magnetic field enhancement could lead to large enhanced pulsed heating and thus could melt surface in a very short time and form a liquid Taylor cone.  
 
WEPFI085 Source and Extraction for Simultaneous Four-hall Beam Delivery System at CEBAF laser, cavity, extraction, electron 2896
 
  • R. Kazimi, J. Hansknecht, M. Spata, H. Wang
    JLAB, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A new design for simultaneous delivery of the electron beam to all four 12 GeV CEBAF experimental halls* requires a new 750 MHz RF separator system in the 5th pass extraction region, a 250 MHz repetition rate for its beams, and addition of a fourth laser at the photo-cathode gun. The proposed system works in tandem with the existing 500 MHz RF separators and beam repetition rate on the lower passes. The new 5th pass RF separators will have the same basic design but modified to run at 750 MHz. The change to the beam repetition rate will be at the photo-cathode gun through an innovative upgrade of the seed laser driver system using electro-optic modulators. The new laser system also allows addition of the fourth laser. The new RF separators, the new laser system and other hardware changes required to implement the Four-Hall operation delivery system will be discussed in this paper.
* Simultaneous Four-Hall Operation for 12 GeV CEBAF, Proceedings of this conference. 		 
 
WEPFI089 High Gradient Normal Conducting Radio-frequency Photoinjector System for Sincrotrone Trieste gun, coupling, quadrupole, dipole 2905
 
  • L. Faillace, R.B. Agustsson, H. Badakov, P. Frigola
    RadiaBeam, Santa Monica, USA
  • F. Cianciosi, P. Craievich, M. Trovò
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • A. Fukasawa, J.B. Rosenzweig, A. Yakub
    UCLA, Los Angeles, California, USA
  
  Radiabeam Technologies, in collaboration with UCLA, presents the development of a high gradient normal conducting radio frequency (NCRF) 1.6 cell photoinjector system for the Sincrotrone Trieste facility. Designed to operate with a 120MV/m accelerating gradient, this single feed, fat lipped racetrack coupler design is modeled after the LCLS photoinjector with a novel demountable cathode which permits cost effective cathode exchange. Full overview of the project to date and installation at Sincrotrone Trieste will be discussed along with basic, design, engineering and manufacturing.  
 
WEPME040 Investigation to Reduce Power Overhead Required in Superconducting RF Cavity Field Control klystron, cavity, controls, feedback 3013
 
  • R. Zeng, S. Molloy, A. Sunesson
    ESS, Lund, Sweden
  • A.J. Johansson
    Lund University, Lund, Sweden
  
  A power overhead of more than 25% is usually required in RF field control of klystron drived superconducting cavity, since it is much easier to implement feild control in a linear region of klystron where it is far below saturation. It however results in a reduced efficiency and more power consumption. Within ESS project it places very high demands on energy efficiency, which leads to stringent requirements on power overhead required in RF field control. Investigation on power overhead reduction in RF field control has been carried out at ESS and related simulation has been done. In this paper we will look at how close we can implement field control to the klystron saturation and discuss if it is possible to make RF field control the RF field with 10% overhead.  
 
WEPME062 Short-Pulse Ti:Sapphire Laser System for Photocathode Research at SLAC laser, gun, cavity, diagnostics 3076
 
  • W.J. Corbett, A. Brachmann, R.N. Coffee, A.R. Fry, S. Gilevich, N. Hartmann, W. Helml, P. Hering, E.N. Jongewaard, D. Kelley, J.R. Lewandowski, W. Polzin, J. Sheppard, P. Stefan, T. Vecchione, S.P. Weathersby, W.E. White, M. Woods, F. Zhou
    SLAC, Menlo Park, California, USA
  
  A photo-cathode research laboratory has been constructed at SLAC to test and characterize the spare LCLS electron gun. At the heart of the laboratory is a dual-purpose Ti:Sapphire oscillator/regen laser that can deliver either a 2.5ps, 760nm beam to the photocathode gun or a 35fs, 800nm beam to prototype diagnostics for the LCLS. The objective of the photocathode research is to definitively identify ‘recipes’ for high-reliability cathode processing resulting in high quantum efficiency and low beam emittance. The LCLS diagnostics program is presently aimed at developing spectral-encoding systems for shot-by-shot pulse arrival time measurements at the 10fs level. In this paper we review the Ti:Sapphire laser system and report on status of the photocathode and diagnostics programs.  
 
THOBB103 THz Electron-pulse-train Dynamics in a MeV Photo-injector electron, acceleration, bunching, laser 3109
 
  • F.H. Chao, C.H. Chen, Y.-C. Huang
    NTHU, Hsinchu, Taiwan
  • P.J. Chou
    NSRRC, Hsinchu, Taiwan
  
  A conventional free electron laser (FEL) is bulky and expensive. In order to quickly build up the FEL power in a short undulator, a laser technology has been proposed to generate a pre-bunched electron pulse-train with a THz bunching frequency from a photoinjector*. The bunching factor** of an accelerated pulse-train beam is influenced by the beam radius, initial bunching frequency, space charge force, acceleration gradient, and acceleration phase in an accelerator. For a given RF accelerator and initial beam parameters, there is a limitation on the maximally attainable bunching factor and bunching frequency for the accelerated pulse-train beam. This paper presents a theoretical analysis for the bunching factor and bunching frequency of an accelerated pulse-train beam subject to nominal initial beam conditions in a photoinjector. The theoretical analysis is compared with the simulation results from the simulation code, PARMELA. To obtain an output bunching factor larger than 0.5%, our simulation study indicates that the maximum bunching frequency at the cathode is 25 THz for a 150 A beam current under a peak acceleration field of 80 MV/m.
* Y.C. Huang, C.H. Chen, A.P. Lee, W.K. Lau, S.G. Liu, NIM, A, 637, S1–S6 (2011).
** Y.C Huang, Appl. Phys. Lett., 96, 231503 (2010). 		 
slides icon Slides THOBB103 [3.076 MB]  
 
THPFI002 Construction and Initial Tests of the Electrostatic Septa for MedAustron septum, vacuum, extraction, injection 3288
 
  • J. Borburgh, R.A. Barlow, C. Boucly, A. Prost
    CERN, Geneva, Switzerland
  • U. Dorda, T. Kramer, T. Stadlbauer
    EBG MedAustron, Wr. Neustadt, Austria
  
  For the MedAustron facility under construction in Wiener Neustadt/Austria, two electrostatic septa are built in collaboration with CERN. These septa will be used for the multi-turn injection of protons and ions, as well as for the slow extraction from the synchrotron. The power supplies are designed to combine the required precision with the capability to cycle sufficiently fast to keep up with the machine cycle. The septa are being assembled at CERN. Initial tests have been done on the remote displacement system to validate its precision and communication protocol with the MedAustron control system. Subsequently the septa are tested for vacuum performance and then HV conditioned. The construction of the septa, the requirements of the power supplies and the high voltage circuit will be described. Results of the initial laboratory tests, prior to installation in the accelerator, will be given.  
 
THPFI024 Application of Electropolishing in CSNS/RCS Primary Collimator Scrapers collimation, synchrotron, proton, scattering 3348
 
  • L. Kang, Z.X. He, H. Qu, J.B. Yu, Y.Q. Zou
    IHEP, Beijing, People's Republic of China
  
  According to the requirements for the beam collimation system physical design of the rapid cycling synchrotron (RCS) of China Spallation Neutron Source (CSNS) , the primary collimator scrapers are made of 0.17±0.005mm thickness tungsten sheets. The machining of the tungsten sheet is very difficult because of high hardness and characteristics of the intrinsic brittleness of tungsten. In this paper, electropolishing processing methods is used for tungsten sheets processing. A special electropolishing device is designed according to the principle and process of electropolishing. The processing of tungsten sheets are finally completed after a series of experiments. And the rules of electropolishing for tungsten sheet processing are obtained according to the experimental results.  
 
THPFI044 NEG Thin Film Coating Development for the MAX IV Vacuum System vacuum, plasma, synchrotron, synchrotron-radiation 3385
 
  • M.J. Grabski, J. Ahlbäck, E. Al-Dmour, P.F. Tavares
    MAX-lab, Lund, Sweden
  • S. Calatroni, P. Chiggiato, P. Costa Pinto, M. Taborelli
    CERN, Geneva, Switzerland
  
  The new synchrotron radiation facility of the MAX IV laboratories is under construction and expected to deliver the first light beam in 2016. To cope with the small aperture, the intense photon bombardment and the low-pressure requirement, most of the beam pipes for the 3-GeV ring are going to be coated with Ti-Zr-V non-evaporable getter (NEG) thin films. To take advantage from the experience acquired during the construction of the Large Hadron Collider (LHC), collaboration between CERN and MAX IV Laboratories has been set up. The choice of the extruded Cu tubes, the preliminary surface treatments, the coating configuration, and the performance validation of the small-diameter vacuum chambers have been addressed. In parallel, an intense development has been tackled at CERN for the coating of vacuum chambers where photon and electron beams circulate in separate pipes. The most important results of the collaboration are presented and future perspectives pointed out.  
 
THPFI093 Device and Technique for In-situ Coating of the RHIC Cold Bore Vacuum Tubes with Thick OFHC electron, vacuum, cryogenics, superconducting-magnet 3508
 
  • A. Hershcovitch, M. Blaskiewicz, J.M. Brennan, W. Fischer, C.J. Liaw, W. Meng, R.J. Todd
    BNL, Upton, Long Island, New York, USA
  • A.X. Custer, M.Y. Erickson, N.Z. Jamshidi, H.J. Poole
    PVI, Oxnard, USA
  • J.M. Jimenez, H. Neupert, M. Taborelli, C. Yin Vallgren
    CERN, Geneva, Switzerland
  • N. Sochugov
    Institute of High Current Electronics, Tomsk, Russia
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
To mitigate electron clouds & unacceptable ohmic heating problems in RHIC, we developed a robotic plasma deposition technique & device to in-situ coat the RHIC 316LN SS cold bore tubes based on mobile mole mounted magnetrons for OFHC deposition. Scrubbed Cu has low SEY and suppress electron cloud formation. Room temperature RF resistivity measurement of Cu coated SS RHIC tube samples indicate that 10 μm of Cu coating has conductivity close to copper tubing. A 50 cm long copper cathode magnetron, mounted on a carriage with spring loaded wheels, was successfully operated, traversed magnet interconnect bellows and adjusted for variations in vacuum tube diameter, while keeping the magnetron centered. To maximize cathode lifetime, Cu cathode thickness was maximized its gap to vacuum tube minimized; movable magnet package is used. Novel cabling and vacuum-atmosphere interface system is being developed. Deposition experiments show no indentation in or damage to coating after wheels roll over coated areas; i.e. train like assembly option is a viable for in-situ RHIC coating. Details of experimental setup & coating of full-scale magnet tube sandwiched between bellows will be presented. 		 
 
THPWA012 The Development of a New Type of Electron Microscope using Superconducting RF Acceleration cavity, acceleration, electron, gun 3654
 
  • N. Higashi
    The University of Tokyo, Graduate School of Science, Tokyo, Japan
  • A. Enomoto, Y. Funahashi, T. Furuya, Y. Kamiya, S. Michizono, M. Nishiwaki, H. Sakai, M. Sawabe, K. Ueno, M. Yamamoto
    KEK, Ibaraki, Japan
  • M. Kuriki
    HU/AdSM, Higashi-Hiroshima, Japan
  • S. Yamashita
    ICEPP, Tokyo, Japan
  
  We are developing a new type of electron microscope (EM), which adopts RF acceleration in order to exceed the energy limit of DC acceleration used in conventional EMs. It enables us to make a high-voltage EM more compact and to examine thicker specimens, and possibly to get better spatial resolution. Using a superconducting RF cavity, we can operate the EM in CW mode to obtain a beam flux comparable to that in DC mode. Low energy dispersion ΔE/E , e.g. 10-6 or better, is required for good spatial resolution in EMs, while it is usually between 10-3 to 10-4 in accelerators. We have thus designed a special type of cavity that can be excited with the fundamental and second-harmonic frequencies simultaneously; TM010 and TM020. With the two-mode cavity, the energy dispersion of the order of 10-5 would be obtained by modifying the peak of accelerating field to be flattened. As the proof-of-principle of our concept, we are developing the prototype using a 300 keV transmission electron microscope (TEM), to which a new photocathode gun and the two-mode cavity are attached. We have already manufactured the cavity and it is under test, and the gun is under construction.  
 
THPWA013 Direct Diagnostic Technique of High-intensity Laser Profile based on Laser-Compton Scattering laser, solenoid, electron, gun 3657
 
  • Y. Yoshida, A. Endo, K. Sakaue, R. Sato, M. Washio
    Waseda University, Tokyo, Japan
  
  Funding: Work supported by NEDO (New Energy and Industrial Technology Development Organization).
A high-intensity laser is essential for the LPP (Laser Produced Plasma) EUV generation, which is studied as the next generation light source of ultra-fine semiconductor lithography. Nevertheless, there is no way to directly measure the profile of high-intensity laser. Therefore, we have been developing a method for measuring high-intensity laser profile based on the laser-Compton scattering using a Cs-Te photo cathode RF-Gun at Waseda University. In this diagnostic technique, laser profile is obtained by scanning the extremely-focused electron beam, which is about 10μm by solenoid lens. We have obtained the 10μm beam size by solenoid lens using tracking code GPT (General Particle Tracer) by optimizing the beam parameter and lens shape. Recently, we have installed solenoid lens and generated focused beam. The focused beam size was evaluated by using radiochromic film called GAFCHROMIC dosimetry film type HD-810. In this conference, we will report the results of GPT simulations, beam size measurements and future prospects. 		 
 
THPWA023 Research on Modeling of the High-density Current Electron Gun System Based on T-S Fuzzy Model electron, gun, controls, simulation 3678
 
  • B. Lv, D.M. Li, H.J. Su
    SINAP, Shanghai, People's Republic of China
  
  Abstract: The stability of the electron beam is considered as an important performance of industrial electron accelerators. For the beam control system of the accelerator, it is significant to obtain the accurate model of the electron gun system. The paper presents a fuzzy modeling method based on the Takagi-Sugeno (T-S) fuzzy model. A T-S model can be obtained using the system identification algorithms from input-output data. In our approach, fuzzy c-means (FCM) clustering algorithm is applied to identify the model structure. And a hybrid method based on quantum-inspired differential evolution algorithm (QDE) and genetic algorithm (GA) is proposed to learn the parameters of T-S fuzzy model. Experiments on the Box-Jenkins gas furnace data have verified the validity of the modeling approach. The simulation results show that the T-S fuzzy model is very well to describe the electron gun system and reveal its performance.  
 
THPWA036 Implementation and Commissioning of the New Electron Beam Test Facility (EBTF) at Daresbury Laboratory for Industrial Accelerator System gun, electron, laser, diagnostics 3708
 
  • P.A. McIntosh, D. Angal-Kalinin, R.K. Buckley, S.R. Buckley, J.A. Clarke, B.D. Fell, A.R. Goulden, C. Hill, F. Jackson, S.P. Jamison, J.K. Jones, A. Kalinin, B.P.M. Liggins, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes, Y.M. Saveliev, B.J.A. Shepherd, S.L. Smith, T.T. Thakker, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • N. Bliss, G. Cox, G.P. Diakun, A. Gleeson, L. Ma, B.G. Martlew, A.J. Moss, K. Robertson, M.D. Roper, R.J. Smith
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  The EBTF facility will provide enabling infrastructures targeted at the development and testing of novel and compact accelerator technologies, specifically through partnership with industry and aimed at addressing applications in medicine, health, security, energy and industrial processing. The facility has now been implemented at Daresbury Laboratory and the commissioning of the critical accelerator systems has been performed. The facility is now preparing for first exploitation with partnering industries that will be able to utilise the electron beam parameters available on EBTF to either demonstrate new techniques and/or processes or otherwise develop new technologies for future commercial realisation.  
 
THPWA044 R&D into Laser Applications for Accelerators laser, electron, acceleration, vacuum 3729
 
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  
  Funding: Work supported by the EU under Grant Agreement 289191.
Lasers can be used for the generation of high brightness electron and exotic ion beams, the acceleration of particles with the highest accelerating gradients, as well as for the characterization of many complex particle beams by means of laser-based beam diagnostics methods. In addition, (free electron) lasers can be used for achieving the highest time resolution and strongest fields for experiments in atomic physics, chemistry and biology, i.e. for studies into the dynamics of some of the most fundamental processes in nature. Without constant progress in laser technology and close collaboration between laser experts and accelerator scientists, many of today's most advanced experiments would simply be impossible. The LA3NET consortium combines developments into laser technology and sensors with their application at advanced accelerator facilities, providing complex beams ranging from highest brightness electron beams to high intensity proton beams. This contribution presents the consortium's broad, yet closely interconnected experimental program.