LINAC2016 - List of Keywords (cathode)

Paper	Title	Other Keywords	Page
MOOP08	Latest News on High Average RF Power Operation at PITZ	gun, operation, vacuum, Windows	59
	Y. Renier, G. Asova, P. Boonpornprasert, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, O. Lishilin, G. Loisch, D. Melkumyan, A. Oppelt, T. Rublack, F. Stephan DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria M. Bousonville, S. Choroba, S. Lederer DESY, Hamburg, Germany C. Saisa-ard Chiang Mai University, Chiang Mai, Thailand Q.T. Zhao IMP/CAS, Lanzhou, People's Republic of China
	The Photo Injector Test Facility at DESY in Zeuthen (PITZ) develops, tests and characterizes high brightness electron sources for FLASH and European XFEL. Since these FELs work with superconducting accelerators in pulsed mode, also the corresponding normal-conducting RF gun has to operate with long RF pulses. Generating high beam quality from the photocathode RF gun in addition requires a high accelerating gradient at the cathode. Therefore, the RF gun has to ensure stable and reliable operation at high average RF power, e.g. 6.5 MW peak power in the gun for 650 μs RF pulse length at 10 Hz repetition rate for the European XFEL. Several RF gun setups have been operated towards these goals over the last years. The latest gun setup was brought into the PITZ tunnel on February 10th 2016 and its RF operation started on March 7th. This setup includes RF gun prototype 4.6 with a new cathode contact spring design and an RF input distribution which consists of an in-vacuum coaxial coupler, an in-vacuum T-combiner and 2 RF windows from DESY production. In this contribution we will summarize the experience from the RF conditioning of this setup towards high average RF power and first experience from the operation with photoelectrons.
	Slides MOOP08 [0.563 MB]
	Poster MOOP08 [0.367 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP08
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MOPLR016	Status of the Injection System of the CLARA FEL Test Facility	gun, cavity, FEL, solenoid	174
	B.L. Militsyn, D. Angal-Kalinin, R.K. Buckley, R.J. Cash, J.A. Clarke, L.S. Cowie, B.D. Fell, P. Goudket, T.J. Jones, K.B. Marinov, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, T.C.Q. Noakes, B.J.A. Shepherd, R. Valizadeh, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom V.V. Paramonov RAS/INR, Moscow, Russia
	The 250 MeV CLARA FEL test facility is now under construction at Daresbury Laboratory. Electron beam for this facility is provided by two normal conducting S-band photocathode guns: a 10 Hz 2.5 cell gun earlier used as the injector for the VELA machine, and a 400 Hz 1.5 cell gun now under commissioning. At the initial stage of Phase I CLARA will operate with the 10 Hz gun and a 45 MeV 2 m long linac section working as a buncher and/or booster. The beam will be deflected into the existing VELA beamline with an S-bend and directed to the spectrometer line for analysing beam properties or into one of two VELA user areas. The 400 Hz gun will be installed in the VELA beamline for detailed high power RF and beam commissioning in the VELA beam diagnostics suite. As the 400 Hz gun is equipped with an interchangeable photocathode it is possible to investigate different metal photocathodes and select the one providing minimal beam emittance at highest quantum efficiency. A state of the art photocathode preparation system is under commissioning at Daresbury. After commissioning the 400 Hz gun will be installed to the CLARA beam line to deliver high energy, high repetition rate beams for the FEL facility, and the 10 Hz gun will be returned to the VELA beam line.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR016
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MOPLR037	Study of the Surface and Performance of Single-Cell Nb Cavities After Vertical EP Using Ninja Cathodes	cavity, experiment, polarization, niobium	217
	V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan P. Carbonnier, F. Éozénou, Y. Gasser, L. Maurice, C. Servouin CEA/DSM/IRFU, France F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan K. Ishimi MGI, Chiba, Japan
	A 1.3 GHz single-cell niobium (Nb) coupon cavity was vertically electropolished (VEPed) with three different Ninja cathodes which were specially designed for VEP of 1.3 GHz superconducting RF elliptical (ILC/Tesla type) cavities. The cathodes were fabricated to have different surface areas and different distances between cathode surface and the equator. The Ninja cathode prepared with an enhanced cathode surface area was covered with a meshed shield to avoid bubble attack on the surface of the cavity cell. It has been turned out that the anode-cathode distance and the cathode area affect surface morphology of the equator. A smooth equator surface was obtained in the cases in which the cathode surface was geometrically close to the equator or instead the cathode surface area was sufficiently larger. Two 1.3 GHz ILC/Tesla type single-cell cavities VEPed with the Ninja cathodes and using optimized conditions showed good performance in vertical tests.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR037
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MOPLR038	Fabrication of 9 Cell Coupon Cavity for Vertical Electropolishing Test	cavity, SRF, polarization, controls	220
	S. Kato, H. Hayano, H. Inoue, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan
	We have been using single cell coupon cavities to establish vertical electropolishing (VEP) process for a couple of years. A series of in-situ measurements of an EP current at an individual coupon in a coupon cavity can help determination of appropriate EP conditions. VEPed coupons which are surface analysed with XPS, SEM and the other tools can also bring lot information and expertise to development of VEP cathode and optimization of VEP conditions. This time we fabricated the world first 9-cell coupon cavity where 3 sample coupons at the equators and 6 sample coupons at positions close to the irises can be installed. VEP of this coupon cavity with a newly developed Ninja cathode brought useful information for improvement of the VEP facility and optimization of the VEP conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR038
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MOPLR039	Development of New Type "Ninja" Cathode for Nb 9-cell Cavity and Experiment of Vertical Electro-Polishing	cavity, experiment, target, collider	223
	K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan K. Ishimi MGI, Chiba, Japan
	Marui Galvanizing Co. Ltd. has been improving Vertical Electro-Polishing (VEP) technologies and facilities for Nb 9-cell superconducting accelerator cavity for International Linear Collider (ILC) in collaboration with KEK. This time, we developed new type 'Ninja' cathode in order to improve VEP uniformity of Nb 9-cell cavity inner surface based on the results of 1-cell cavity VEP experiment. In this article, we will report construction of new type "Ninja" cathode for Nb 9-cell cavity and experiment of VEP using this.
	Poster MOPLR039 [0.610 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR039
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MOPLR043	Cavity Processing and Preparation of 650 MHz Elliptical Cell Cavities for PIP-II	cavity, SRF, vacuum, factory	229
	A.M. Rowe, S.K. Chandrasekaran, A. Grassellino, O.S. Melnychuk, M. Merio, D.A. Sergatskov Fermilab, Batavia, Illinois, USA T. Reid ANL, Argonne, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. The PIP-II project at Fermilab requires fifteen 650 MHz SRF cryomodules as part of the 800 MeV LINAC that will provide a high intensity proton beam to the Fermilab neutrino program. A total of fifty-seven high-performance SRF cavities will populate the cryomodules and will operate in both pulsed and continuous wave modes. These cavities will be processed and prepared for performance testing utilizing adapted cavity processing infrastructure already in place at Fermilab and Argonne. The processing recipes implemented for these structures will incorporate state-of-the art processing and cleaning techniques developed for 1.3 GHz SRF cavities for the ILC, XFEL, and LCLS-II projects. This paper describes the details of the processing recipes and associated chemistry, heat treatment, and cleanroom processes at the Fermilab and Argonne cavity processing facilities. This paper also presents single and multi-cell cavity test results with quality factors above 5·10¹⁰ and accelerating gradients above 30 MV/m.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR043
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TU3A01	Beam Commissioning Results From the R&D ERL at BNL	gun, SRF, laser, cavity	374
	D. Kayran, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, D.M. Gassner, L.R. Hammons, J.P. Jamilkowski, P. K. Kankiya, R.F. Lambiase, V. Litvinenko, R.J. Michnoff, T.A. Miller, J. Morris, V. Ptitsyn, T. Seda, B. Sheehy, K.S. Smith, E. Wang, W. Xu BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, L.R. Hammons, V. Litvinenko, V. Ptitsyn Stony Brook University, Stony Brook, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy BNL R&D ERL beam commissioning started in June 2014 []. The key components of R&D ERL are the highly damped 5-cell 704 MHz superconducting RF cavity and the high-current superconducting RF gun. The gun is equipped with a multi-alkaline photocathode insertion system. The first photocurrent from ERL SRF gun has been observed in November 2014. In June 2015 a high charge 0.5nC and 20 uA average current were demonstrated. In July 2015 gun to dump beam test started. The beam was successfully transported from the SRF gun through the injection system, then through the linac to the beam dump. All ERL components have been installed. In October 2015, SRF gun cavity has been found contaminated during severe cathode stalk RF conditioning. This cavity has been sent for repair and modification for later use in low-energy RHIC electron cooler (LEReC)[]. LEReC scheduled to start commissioning in early of 2018. We present our results of BNL ERL beam commissioning, the measured beam properties, the operational status, and future prospects. ) D.Kayran et al., Status and commissioning results of the R&D ERL at BNL. Proc. ERL2015, p. 11-14 **)J. Kewisch et al., ERL for Low Energy Electron Cooling at RHIC (LEReC). Proc. ERL2015, p. 67-71
	Slides TU3A01 [12.502 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TU3A01
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TUOP09	State of the Art Advanced Magnetron for Accelerator RF Power Source	linac, cavity, radiation, electron	405
	H. Obata, K. Furumoto, H. Miyamoto New Japan Radio Co., Ltd., Fujimino Saitama, Japan
	X ray sources for linear accelerators continue to be a necessary requirement for industries such as medical, inspection, and nondestructive test equipment. Future requirements for such sources are; low cost, compact packaging and high performance of the RF source for electron acceleration. The magnetron has proven to be a perfect source over other RF sources for linear accelerator use. Because of its simple design, low cost per output, small size and proven performance it meets all required characteristics. New Japan Radio Co., Ltd. has improved and modified its linac magnetrons' performance and characteristics enabling easy matching to the linac modulator, long life and maximum output power. This paper will provide a detailed explanation on the improved magnetron design methodology and its effects on the performance of these magnetrons installed in linac systems. These technologies have been utilized successfully on a commercial level worldwide over the last few years. The technology has been deployed into linac systems operating in S and X band and soon C band, at various output power levels.
	Slides TUOP09 [1.127 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP09
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TUPRC015	Final Acceptance Test of SRF Photo-Injector Cold String for the BERLinPro Energy Recovery Linac	cavity, SRF, gun, target	445
	A. Neumann, D. Böhlick, P. Echevarria, A. Frahm, F. Göbel, T. Kamps, J. Knobloch, O. Kugeler, M. Schuster, J. Ullrich, A. Ushakov HZB, Berlin, Germany A. Burrill SLAC, Menlo Park, California, USA G. Ciovati, P. Kneisel JLab, Newport News, Virginia, USA A. Matheisen, M. Schalwat, M. Schmökel DESY, Hamburg, Germany E.N. Zaplatin FZJ, Jülich, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association. Helmholtz-Zentrum Berlin (HZB) is currently designing and building an high average current all superconducting CW driven ERL as a prototype to demonstrate low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. In order to achieve these demanding goals HZB started a staged program for developing this class of required high current, high brightness SRF electron sources. In this contribution we will present the current status of the module assembly and testing of the prototype SRF photo-injector cavity cold string. The steps taken to install the cathode insert system with the cavity in the cleanroom and the following horizontal test of the cold string as final acceptance test prior installation into its cryostat are shown. First beam in a dedicated diagnostics teststand called Gunlab are planned for this winter.
	Poster TUPRC015 [2.077 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC015
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TUPRC017	Field Flatness and Frequency Tuning of the CLARA High Repetition Rate Photoinjector	cavity, coupling, FEL, gun	452
	L.S. Cowie, P. Goudket, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom T.J. Jones STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom B. Keune RI Research Instruments GmbH, Bergisch Gladbach, Germany
	The High Repetition Rate Photoinjector, designed for the CLARA FEL at Daresbury Laboratory, was tuned at the manufacturers for both field flatness and frequency. Due to the high average power in the cavity of 6.8 kW the cavity requires significant cooling, achieved by water channels in the cavity body. These channels prohibit the use of tuning studs to tune the cavity. The cavity was tuned by taking pre-braze clamped low power RF measurements and using the data to trim the cavity cells to the optimum length for both field flatness and frequency. The optimum field flatness is 100% and the design frequency is 2998.5 MHz. Both cells were trimmed in 3 stages, resulting in a post-braze frequency of 2998.51 MHz and field flatness of 98%.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC017
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TUPRC020	The TRIUMF ARIEL RF Modulated Thermionic Electron Source	electron, emittance, TRIUMF, target	458
	F. Ames, Y.-C. Chao, K. Fong, N. Khan, S.R. Koscielniak, A. Laxdal, L. Merminga, T. Planche, S. Saminathan, D.W. Storey TRIUMF, Vancouver, Canada Y.-C. Chao, L. Merminga SLAC, Menlo Park, California, USA C.K. Sinclair Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: ARIEL is funded by the Canada Foundation for Innovation, the Provinces AB, BC, MA, ON, QC, and TRIUMF. TRIUMF receives funding via a contribution agreement with the National Research Council of Canada Within the ARIEL (Advanced Rare IsotopE Laboratory) at TRIUMF, a high power electron beam is used to produce radioactive ion beams via photo-fission. The electron beam is accelerated in a superconducting linac up to 50 MeV. The electron source provides electron bunches with charge up to 16 pC at a repetition frequency of 650 MHz leading to an average current of 10 mA . The kinetic energy of the electrons has been chosen to be 300 keV to allow direct injection into an accelerator cavity. The main components of the source are a gridded dispenser cathode (CPI 'Y845) in an SF6 filled vessel and an in-air HV power supply. The beam is bunched by applying DC and RF fields to the grid. Unique features of the gun are its cathode/anode geometry to reduce field emission, and transmission of RF modulation via a dielectric (ceramic) waveguide through the SF6. The latter obviates the need for an HV platform inside the vessel to carry the RF generator and results in a significantly smaller/simpler vessel. The source has been installed and first tests with accelerated beams have been performed. Measurements of the beam properties and results from the commissioning of the source will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC020
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TUPRC022	UPS Study for CsK2Sb Photocathode	electron, laser, experiment, ion	465
	M. Kuriki, T. Konomi, Y. Seimiya KEK, Ibaraki, Japan L. Guo, M. Urano, A. Yokota HU/AdSM, Higashi-Hiroshima, Japan K. Negishi Iwate University, Morioka, Iwate, Japan
	CsK2Sb photo-cathode is one of the ideal cathode for accelerators requiring the high brightness electron beam. It can be driven with a green laser which can be generated as SHG from solid state laser. The QE (Quantum Efficiency) of photo-electron emission is as high as more than 10% with 532nm light. The material is robust and the typical operational lifetime is more than several months. It is also vital against the high intensity beam extraction. The photo-cathode is generated as a thin film in-situ and the material property and optimized condition for the cathode formation is not understood well. In this article, we present UPS analysis of CsK2Sb cathode for deeper understanding.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC022
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TUPLR013	Lifetime Study of CKk2Sb Robust Photo-Cathode for a High Brightness Electron Source	laser, vacuum, electron, brightness	500
	M. Kuriki, Y. Seimiya KEK, Ibaraki, Japan L. Guo, K. Moriya, M. Urano, A. Yokota HU/AdSM, Higashi-Hiroshima, Japan K. Negishi Iwate University, Morioka, Iwate, Japan
	CsK2Sb photo-cathode is one of the ideal cathode for accelerators requiring the high brightness electron beam. It can be driven with a green laser which can be generated as SHG from solid state laser. The QE (Quantum Efficiency) of photo-electron emission is as high as more than 10% with 532nm light. In this article, the robustness of the cathode is studied. Two indexes of lifetime regarding to time and extracted charge density were evaluated experimentally. The result shows that the cathode is robust enough for a high brightness accelerator.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR013
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TUPLR017	Summary of the Test and Installation of 10 MW MBKs for the XFEL Project	klystron, ion, vacuum, linac	506
	V. Vogel (Fogel), L. Butkowski, A. Cherepenko, S. Choroba, J. Hartung, V.V. Kachaev, R. Wagner, S. Wiesenberg DESY, Hamburg, Germany
	For the European XFEL project, horizontal multi-beam klystrons (MBK) which produce RF power up to 10 MW, at an RF frequency of 1.3 GHz, 1.5 ms pulse length and 10 Hz repetition rate, were chosen as RF power sources. All MBKs have been manufactured by two companies, 22 tubes from Thales Electron Devices and 7 tubes from Toshiba Electron Tubes & Devices. In this article we will give a summary of the tube testing, conditioning and installation in the underground linear accelerator tunnel.
	Poster TUPLR017 [1.975 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR017
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TUPLR035	RF Analysis of Electropolishing for EXFEL Cavities Production at Ettore Zanon Spa	cavity, shielding, SRF, superconductivity	544
	A.A. Sulimov DESY, Hamburg, Germany M. Giaretta, A. Gresele, A. Visentin Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
	After successful finishing of superconducting cavities mass production at Ettore Zanon S.p.A. (EZ) for the European XFEL (EXFEL), the authors had the possibility to provide a detailed analysis of the electropolishing (EP) process. The analysis of EP material removal is based on specified RF measurements and was used for the determination of both, the ratio between cavity's iris and equator and uniformity in different cells. A comparison of the RF measurements results with mechanical measurements is presented.
	Poster TUPLR035 [0.195 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR035
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THPLR013	LEETCHI: The High Current Electron Source for the CLIC Drive Beam Injector	electron, gun, high-voltage, simulation	870
	K. Pepitone, S. Döbert CERN, Geneva, Switzerland B. Cadilhon, B. Cassany, J. Gardelle CEA, LE BARP cedex, France
	LEETCHI is a source which will produce 140 keV, 5 A, 140 μs electron beams at a repetition rate of 50 Hz. The shot to shot and flat top current stability of this drive beam injector for CLIC has to be better than 0.1% and a geometrical emittance of 14 mm mrad is expected. The development of a high voltage modulator, to achieve those requirements, is ongoing. A small test stand has been built which allows to diagnose and dump the beam produced by the thermionic cathode. The thermionic cathode is equipped with a grid which will allow us to control the current and eventually to have a feedback on the flattop shape. The beam dump, made of graphite, has been designed using two different codes, the Monte Carlo code GEANT4 to simulate the energy deposition and ANSYS used to simulate the thermal resistance of the graphite due to the long pulse duration. The geometry has been optimized with the ray tracing code EGUN and the 2D PIC-code MAGIC. All these simulations allowed us to optimize the geometry of the gun and to develop diagnostics which must survive to the heat deposition. Finally, the first electrical measurements of the beam will be presented.
	Poster THPLR013 [19.847 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR013
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THPLR021	Identification of Emitting Sources of Dark Currents From Gridded Thermionic Electron Gun and Measures to Suppress Dark Currents From Electron Gun in SPring-8 Linear Accelerator	electron, gun, acceleration, synchrotron	888
	T. Magome, H. Hanaki, T. Kobayashi, S. Suzuki, T. Taniuchi JASRI/SPring-8, Hyogo-ken, Japan
	The dark current is emitted from a gridded thermionic electron gun although the grid-electrode potential against the cathode is negative enough to suppress the cathode emission current. This dark current in the SPring-8 linear accelerator caused satellite bunches unignorable for precise experiments in the downstream electron storage ring. The dark current has been investigated by means of our electron-gun test equipment applying a DC accelerator voltage to the electron gun. The investigations revealed that the dark current was generated from the wehnelt electrode, the gird electrode, and the cathode surface. The dark current from the wehnelt electrode was decreased under the measurement limit 2·10^-15 A by replacing the wehnelt and the anode electrodes with new electro-polished ones. The dark current from the cathode surface was reduced by lowering the grid-electrode potential against the cathode down to -160 V. To reduce the dark current from the grid electrode, the surface of the grid electrode was significantly smoothed by electro-polishing.
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Paper

Title

Other Keywords

Page

MOOP08

Latest News on High Average RF Power Operation at PITZ

gun, operation, vacuum, Windows

59

Y. Renier, G. Asova, P. Boonpornprasert, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, O. Lishilin, G. Loisch, D. Melkumyan, A. Oppelt, T. Rublack, F. Stephan
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
M. Bousonville, S. Choroba, S. Lederer
DESY, Hamburg, Germany
C. Saisa-ard
Chiang Mai University, Chiang Mai, Thailand
Q.T. Zhao
IMP/CAS, Lanzhou, People's Republic of China

The Photo Injector Test Facility at DESY in Zeuthen (PITZ) develops, tests and characterizes high brightness electron sources for FLASH and European XFEL. Since these FELs work with superconducting accelerators in pulsed mode, also the corresponding normal-conducting RF gun has to operate with long RF pulses. Generating high beam quality from the photocathode RF gun in addition requires a high accelerating gradient at the cathode. Therefore, the RF gun has to ensure stable and reliable operation at high average RF power, e.g. 6.5 MW peak power in the gun for 650 μs RF pulse length at 10 Hz repetition rate for the European XFEL. Several RF gun setups have been operated towards these goals over the last years. The latest gun setup was brought into the PITZ tunnel on February 10th 2016 and its RF operation started on March 7th. This setup includes RF gun prototype 4.6 with a new cathode contact spring design and an RF input distribution which consists of an in-vacuum coaxial coupler, an in-vacuum T-combiner and 2 RF windows from DESY production. In this contribution we will summarize the experience from the RF conditioning of this setup towards high average RF power and first experience from the operation with photoelectrons.

Slides MOOP08 [0.563 MB]

Poster MOOP08 [0.367 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP08

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MOPLR016

Status of the Injection System of the CLARA FEL Test Facility

gun, cavity, FEL, solenoid

174

B.L. Militsyn, D. Angal-Kalinin, R.K. Buckley, R.J. Cash, J.A. Clarke, L.S. Cowie, B.D. Fell, P. Goudket, T.J. Jones, K.B. Marinov, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, T.C.Q. Noakes, B.J.A. Shepherd, R. Valizadeh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
V.V. Paramonov
RAS/INR, Moscow, Russia

The 250 MeV CLARA FEL test facility is now under construction at Daresbury Laboratory. Electron beam for this facility is provided by two normal conducting S-band photocathode guns: a 10 Hz 2.5 cell gun earlier used as the injector for the VELA machine, and a 400 Hz 1.5 cell gun now under commissioning. At the initial stage of Phase I CLARA will operate with the 10 Hz gun and a 45 MeV 2 m long linac section working as a buncher and/or booster. The beam will be deflected into the existing VELA beamline with an S-bend and directed to the spectrometer line for analysing beam properties or into one of two VELA user areas. The 400 Hz gun will be installed in the VELA beamline for detailed high power RF and beam commissioning in the VELA beam diagnostics suite. As the 400 Hz gun is equipped with an interchangeable photocathode it is possible to investigate different metal photocathodes and select the one providing minimal beam emittance at highest quantum efficiency. A state of the art photocathode preparation system is under commissioning at Daresbury. After commissioning the 400 Hz gun will be installed to the CLARA beam line to deliver high energy, high repetition rate beams for the FEL facility, and the 10 Hz gun will be returned to the VELA beam line.

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MOPLR037

Study of the Surface and Performance of Single-Cell Nb Cavities After Vertical EP Using Ninja Cathodes

cavity, experiment, polarization, niobium

217

V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
P. Carbonnier, F. Éozénou, Y. Gasser, L. Maurice, C. Servouin
CEA/DSM/IRFU, France
F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
K. Ishimi
MGI, Chiba, Japan

A 1.3 GHz single-cell niobium (Nb) coupon cavity was vertically electropolished (VEPed) with three different Ninja cathodes which were specially designed for VEP of 1.3 GHz superconducting RF elliptical (ILC/Tesla type) cavities. The cathodes were fabricated to have different surface areas and different distances between cathode surface and the equator. The Ninja cathode prepared with an enhanced cathode surface area was covered with a meshed shield to avoid bubble attack on the surface of the cavity cell. It has been turned out that the anode-cathode distance and the cathode area affect surface morphology of the equator. A smooth equator surface was obtained in the cases in which the cathode surface was geometrically close to the equator or instead the cathode surface area was sufficiently larger. Two 1.3 GHz ILC/Tesla type single-cell cavities VEPed with the Ninja cathodes and using optimized conditions showed good performance in vertical tests.

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MOPLR038

Fabrication of 9 Cell Coupon Cavity for Vertical Electropolishing Test

cavity, SRF, polarization, controls

220

S. Kato, H. Hayano, H. Inoue, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan

We have been using single cell coupon cavities to establish vertical electropolishing (VEP) process for a couple of years. A series of in-situ measurements of an EP current at an individual coupon in a coupon cavity can help determination of appropriate EP conditions. VEPed coupons which are surface analysed with XPS, SEM and the other tools can also bring lot information and expertise to development of VEP cathode and optimization of VEP conditions. This time we fabricated the world first 9-cell coupon cavity where 3 sample coupons at the equators and 6 sample coupons at positions close to the irises can be installed. VEP of this coupon cavity with a newly developed Ninja cathode brought useful information for improvement of the VEP facility and optimization of the VEP conditions.

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MOPLR039

Development of New Type "Ninja" Cathode for Nb 9-cell Cavity and Experiment of Vertical Electro-Polishing

cavity, experiment, target, collider

223

K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
K. Ishimi
MGI, Chiba, Japan

Marui Galvanizing Co. Ltd. has been improving Vertical Electro-Polishing (VEP) technologies and facilities for Nb 9-cell superconducting accelerator cavity for International Linear Collider (ILC) in collaboration with KEK. This time, we developed new type 'Ninja' cathode in order to improve VEP uniformity of Nb 9-cell cavity inner surface based on the results of 1-cell cavity VEP experiment. In this article, we will report construction of new type "Ninja" cathode for Nb 9-cell cavity and experiment of VEP using this.

Poster MOPLR039 [0.610 MB]

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MOPLR043

Cavity Processing and Preparation of 650 MHz Elliptical Cell Cavities for PIP-II

cavity, SRF, vacuum, factory

229

A.M. Rowe, S.K. Chandrasekaran, A. Grassellino, O.S. Melnychuk, M. Merio, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
T. Reid
ANL, Argonne, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
The PIP-II project at Fermilab requires fifteen 650 MHz SRF cryomodules as part of the 800 MeV LINAC that will provide a high intensity proton beam to the Fermilab neutrino program. A total of fifty-seven high-performance SRF cavities will populate the cryomodules and will operate in both pulsed and continuous wave modes. These cavities will be processed and prepared for performance testing utilizing adapted cavity processing infrastructure already in place at Fermilab and Argonne. The processing recipes implemented for these structures will incorporate state-of-the art processing and cleaning techniques developed for 1.3 GHz SRF cavities for the ILC, XFEL, and LCLS-II projects. This paper describes the details of the processing recipes and associated chemistry, heat treatment, and cleanroom processes at the Fermilab and Argonne cavity processing facilities. This paper also presents single and multi-cell cavity test results with quality factors above 5·10¹⁰ and accelerating gradients above 30 MV/m.

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TU3A01

Beam Commissioning Results From the R&D ERL at BNL

gun, SRF, laser, cavity

374

D. Kayran, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, D.M. Gassner, L.R. Hammons, J.P. Jamilkowski, P. K. Kankiya, R.F. Lambiase, V. Litvinenko, R.J. Michnoff, T.A. Miller, J. Morris, V. Ptitsyn, T. Seda, B. Sheehy, K.S. Smith, E. Wang, W. Xu
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, L.R. Hammons, V. Litvinenko, V. Ptitsyn
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
BNL R&D ERL beam commissioning started in June 2014 [*]. The key components of R&D ERL are the highly damped 5-cell 704 MHz superconducting RF cavity and the high-current superconducting RF gun. The gun is equipped with a multi-alkaline photocathode insertion system. The first photocurrent from ERL SRF gun has been observed in November 2014. In June 2015 a high charge 0.5nC and 20 uA average current were demonstrated. In July 2015 gun to dump beam test started. The beam was successfully transported from the SRF gun through the injection system, then through the linac to the beam dump. All ERL components have been installed. In October 2015, SRF gun cavity has been found contaminated during severe cathode stalk RF conditioning. This cavity has been sent for repair and modification for later use in low-energy RHIC electron cooler (LEReC)[**]. LEReC scheduled to start commissioning in early of 2018. We present our results of BNL ERL beam commissioning, the measured beam properties, the operational status, and future prospects.
*) D.Kayran et al., Status and commissioning results of the R&D ERL at BNL. Proc. ERL2015, p. 11-14
**)J. Kewisch et al., ERL for Low Energy Electron Cooling at RHIC (LEReC). Proc. ERL2015, p. 67-71

Slides TU3A01 [12.502 MB]

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TUOP09

State of the Art Advanced Magnetron for Accelerator RF Power Source

linac, cavity, radiation, electron

405

H. Obata, K. Furumoto, H. Miyamoto
New Japan Radio Co., Ltd., Fujimino Saitama, Japan

X ray sources for linear accelerators continue to be a necessary requirement for industries such as medical, inspection, and nondestructive test equipment. Future requirements for such sources are; low cost, compact packaging and high performance of the RF source for electron acceleration. The magnetron has proven to be a perfect source over other RF sources for linear accelerator use. Because of its simple design, low cost per output, small size and proven performance it meets all required characteristics. New Japan Radio Co., Ltd. has improved and modified its linac magnetrons' performance and characteristics enabling easy matching to the linac modulator, long life and maximum output power. This paper will provide a detailed explanation on the improved magnetron design methodology and its effects on the performance of these magnetrons installed in linac systems. These technologies have been utilized successfully on a commercial level worldwide over the last few years. The technology has been deployed into linac systems operating in S and X band and soon C band, at various output power levels.

Slides TUOP09 [1.127 MB]

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TUPRC015

Final Acceptance Test of SRF Photo-Injector Cold String for the BERLinPro Energy Recovery Linac

cavity, SRF, gun, target

445

A. Neumann, D. Böhlick, P. Echevarria, A. Frahm, F. Göbel, T. Kamps, J. Knobloch, O. Kugeler, M. Schuster, J. Ullrich, A. Ushakov
HZB, Berlin, Germany
A. Burrill
SLAC, Menlo Park, California, USA
G. Ciovati, P. Kneisel
JLab, Newport News, Virginia, USA
A. Matheisen, M. Schalwat, M. Schmökel
DESY, Hamburg, Germany
E.N. Zaplatin
FZJ, Jülich, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin and grants of Helmholtz Association.
Helmholtz-Zentrum Berlin (HZB) is currently designing and building an high average current all superconducting CW driven ERL as a prototype to demonstrate low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. In order to achieve these demanding goals HZB started a staged program for developing this class of required high current, high brightness SRF electron sources. In this contribution we will present the current status of the module assembly and testing of the prototype SRF photo-injector cavity cold string. The steps taken to install the cathode insert system with the cavity in the cleanroom and the following horizontal test of the cold string as final acceptance test prior installation into its cryostat are shown. First beam in a dedicated diagnostics teststand called Gunlab are planned for this winter.

Poster TUPRC015 [2.077 MB]

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TUPRC017

Field Flatness and Frequency Tuning of the CLARA High Repetition Rate Photoinjector

cavity, coupling, FEL, gun

452

L.S. Cowie, P. Goudket, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
B. Keune
RI Research Instruments GmbH, Bergisch Gladbach, Germany

The High Repetition Rate Photoinjector, designed for the CLARA FEL at Daresbury Laboratory, was tuned at the manufacturers for both field flatness and frequency. Due to the high average power in the cavity of 6.8 kW the cavity requires significant cooling, achieved by water channels in the cavity body. These channels prohibit the use of tuning studs to tune the cavity. The cavity was tuned by taking pre-braze clamped low power RF measurements and using the data to trim the cavity cells to the optimum length for both field flatness and frequency. The optimum field flatness is 100% and the design frequency is 2998.5 MHz. Both cells were trimmed in 3 stages, resulting in a post-braze frequency of 2998.51 MHz and field flatness of 98%.

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TUPRC020

The TRIUMF ARIEL RF Modulated Thermionic Electron Source

electron, emittance, TRIUMF, target

458

F. Ames, Y.-C. Chao, K. Fong, N. Khan, S.R. Koscielniak, A. Laxdal, L. Merminga, T. Planche, S. Saminathan, D.W. Storey
TRIUMF, Vancouver, Canada
Y.-C. Chao, L. Merminga
SLAC, Menlo Park, California, USA
C.K. Sinclair
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: ARIEL is funded by the Canada Foundation for Innovation, the Provinces AB, BC, MA, ON, QC, and TRIUMF. TRIUMF receives funding via a contribution agreement with the National Research Council of Canada
Within the ARIEL (Advanced Rare IsotopE Laboratory) at TRIUMF, a high power electron beam is used to produce radioactive ion beams via photo-fission. The electron beam is accelerated in a superconducting linac up to 50 MeV. The electron source provides electron bunches with charge up to 16 pC at a repetition frequency of 650 MHz leading to an average current of 10 mA . The kinetic energy of the electrons has been chosen to be 300 keV to allow direct injection into an accelerator cavity. The main components of the source are a gridded dispenser cathode (CPI 'Y845) in an SF6 filled vessel and an in-air HV power supply. The beam is bunched by applying DC and RF fields to the grid. Unique features of the gun are its cathode/anode geometry to reduce field emission, and transmission of RF modulation via a dielectric (ceramic) waveguide through the SF6. The latter obviates the need for an HV platform inside the vessel to carry the RF generator and results in a significantly smaller/simpler vessel. The source has been installed and first tests with accelerated beams have been performed. Measurements of the beam properties and results from the commissioning of the source will be presented.

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TUPRC022

UPS Study for CsK2Sb Photocathode

electron, laser, experiment, ion

465

M. Kuriki, T. Konomi, Y. Seimiya
KEK, Ibaraki, Japan
L. Guo, M. Urano, A. Yokota
HU/AdSM, Higashi-Hiroshima, Japan
K. Negishi
Iwate University, Morioka, Iwate, Japan

CsK2Sb photo-cathode is one of the ideal cathode for accelerators requiring the high brightness electron beam. It can be driven with a green laser which can be generated as SHG from solid state laser. The QE (Quantum Efficiency) of photo-electron emission is as high as more than 10% with 532nm light. The material is robust and the typical operational lifetime is more than several months. It is also vital against the high intensity beam extraction. The photo-cathode is generated as a thin film in-situ and the material property and optimized condition for the cathode formation is not understood well. In this article, we present UPS analysis of CsK2Sb cathode for deeper understanding.

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TUPLR013

Lifetime Study of CKk2Sb Robust Photo-Cathode for a High Brightness Electron Source

laser, vacuum, electron, brightness

500

M. Kuriki, Y. Seimiya
KEK, Ibaraki, Japan
L. Guo, K. Moriya, M. Urano, A. Yokota
HU/AdSM, Higashi-Hiroshima, Japan
K. Negishi
Iwate University, Morioka, Iwate, Japan

CsK2Sb photo-cathode is one of the ideal cathode for accelerators requiring the high brightness electron beam. It can be driven with a green laser which can be generated as SHG from solid state laser. The QE (Quantum Efficiency) of photo-electron emission is as high as more than 10% with 532nm light. In this article, the robustness of the cathode is studied. Two indexes of lifetime regarding to time and extracted charge density were evaluated experimentally. The result shows that the cathode is robust enough for a high brightness accelerator.

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TUPLR017

Summary of the Test and Installation of 10 MW MBKs for the XFEL Project

klystron, ion, vacuum, linac

506

V. Vogel (Fogel), L. Butkowski, A. Cherepenko, S. Choroba, J. Hartung, V.V. Kachaev, R. Wagner, S. Wiesenberg
DESY, Hamburg, Germany

For the European XFEL project, horizontal multi-beam klystrons (MBK) which produce RF power up to 10 MW, at an RF frequency of 1.3 GHz, 1.5 ms pulse length and 10 Hz repetition rate, were chosen as RF power sources. All MBKs have been manufactured by two companies, 22 tubes from Thales Electron Devices and 7 tubes from Toshiba Electron Tubes & Devices. In this article we will give a summary of the tube testing, conditioning and installation in the underground linear accelerator tunnel.

Poster TUPLR017 [1.975 MB]

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TUPLR035

RF Analysis of Electropolishing for EXFEL Cavities Production at Ettore Zanon Spa

cavity, shielding, SRF, superconductivity

544

A.A. Sulimov
DESY, Hamburg, Germany
M. Giaretta, A. Gresele, A. Visentin
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy

After successful finishing of superconducting cavities mass production at Ettore Zanon S.p.A. (EZ) for the European XFEL (EXFEL), the authors had the possibility to provide a detailed analysis of the electropolishing (EP) process. The analysis of EP material removal is based on specified RF measurements and was used for the determination of both, the ratio between cavity's iris and equator and uniformity in different cells. A comparison of the RF measurements results with mechanical measurements is presented.

Poster TUPLR035 [0.195 MB]

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THPLR013

LEETCHI: The High Current Electron Source for the CLIC Drive Beam Injector

electron, gun, high-voltage, simulation

870

K. Pepitone, S. Döbert
CERN, Geneva, Switzerland
B. Cadilhon, B. Cassany, J. Gardelle
CEA, LE BARP cedex, France

LEETCHI is a source which will produce 140 keV, 5 A, 140 μs electron beams at a repetition rate of 50 Hz. The shot to shot and flat top current stability of this drive beam injector for CLIC has to be better than 0.1% and a geometrical emittance of 14 mm mrad is expected. The development of a high voltage modulator, to achieve those requirements, is ongoing. A small test stand has been built which allows to diagnose and dump the beam produced by the thermionic cathode. The thermionic cathode is equipped with a grid which will allow us to control the current and eventually to have a feedback on the flattop shape. The beam dump, made of graphite, has been designed using two different codes, the Monte Carlo code GEANT4 to simulate the energy deposition and ANSYS used to simulate the thermal resistance of the graphite due to the long pulse duration. The geometry has been optimized with the ray tracing code EGUN and the 2D PIC-code MAGIC. All these simulations allowed us to optimize the geometry of the gun and to develop diagnostics which must survive to the heat deposition. Finally, the first electrical measurements of the beam will be presented.

Poster THPLR013 [19.847 MB]

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THPLR021

Identification of Emitting Sources of Dark Currents From Gridded Thermionic Electron Gun and Measures to Suppress Dark Currents From Electron Gun in SPring-8 Linear Accelerator

electron, gun, acceleration, synchrotron

888

T. Magome, H. Hanaki, T. Kobayashi, S. Suzuki, T. Taniuchi
JASRI/SPring-8, Hyogo-ken, Japan

The dark current is emitted from a gridded thermionic electron gun although the grid-electrode potential against the cathode is negative enough to suppress the cathode emission current. This dark current in the SPring-8 linear accelerator caused satellite bunches unignorable for precise experiments in the downstream electron storage ring. The dark current has been investigated by means of our electron-gun test equipment applying a DC accelerator voltage to the electron gun. The investigations revealed that the dark current was generated from the wehnelt electrode, the gird electrode, and the cathode surface. The dark current from the wehnelt electrode was decreased under the measurement limit 2·10^-15 A by replacing the wehnelt and the anode electrodes with new electro-polished ones. The dark current from the cathode surface was reduced by lowering the grid-electrode potential against the cathode down to -160 V. To reduce the dark current from the grid electrode, the surface of the grid electrode was significantly smoothed by electro-polishing.

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