LINAC2016 - Classification: 4 Beam Dynamics, Extreme Beams, Sources and Beam Related Technology / 4B Electron and Ion Sources, Guns, Photo Injectors, Charge Breeders

Paper	Title	Page
MOOP08	Latest News on High Average RF Power Operation at PITZ	59
MOPRC002	use link to see paper's listing under its alternate paper code
	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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TUOP03	Developments on the 1.4 MeV/u Pulsed Gas Stripper Cell	387
SPWR028	use link to see paper's listing under its alternate paper code
TUPRC001	use link to see paper's listing under its alternate paper code
	P. Scharrer, W.A. Barth, Ch.E. Düllmann, J. Khuyagbaatar, A. Yakushev HIM, Mainz, Germany W.A. Barth, M. Bevcic, Ch.E. Düllmann, L. Groening, K.P. Horn, E. Jäger, J. Khuyagbaatar, J. Krier, P. Scharrer, A. Yakushev GSI, Darmstadt, Germany Ch.E. Düllmann, P. Scharrer Mainz University, Mainz, Germany
	The GSI UNILAC in combination with SIS18 will serve as a high-current, heavy-ion injector for the FAIR facility. It must meet high demands in terms of beam brilliance at a low duty factor. As part of an UNILAC upgrade program dedicated to FAIR, a new pulsed gas stripper cell was developed, aiming for increased beam intensities inside the post-stripper. The pulsed gas injection is synchronized with the beam pulse timing, enabling a highly-demanded, increased gas density. First tests using uranium beams on a hydrogen target showed a 60%-increased stripping efficiency into the desired 28+ charge state. In 2015, the setup was improved to be able to deliver increased target thicknesses and enhanced flexibility of the gas injection. In recent beam times, the pulsed gas cell was used with various ion-beam types, to test the capabilities for operation at the GSI UNILAC. The stripping of two ion beams in different gases at different gas densities was successfully tested in mixed-beam operation. Charge fractions, beam emittance, and energy-loss were systematically measured using uranium, bismuth, titanium, and argon beams on hydrogen, helium, and nitrogen targets. Selected results will be presented at the conference.
	Slides TUOP03 [1.131 MB]
	Poster TUOP03 [5.943 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP03
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TUPRC015	Final Acceptance Test of SRF Photo-Injector Cold String for the BERLinPro Energy Recovery Linac	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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TUPRC016	S-Band Booster Design and Emittance Preservation for the Awake e-Injector	449
	O. Mete Apsimon, R. Apsimon, G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom S. Döbert CERN, Geneva, Switzerland G.X. Xia UMAN, Manchester, United Kingdom
	AWAKE is a proton driven plasma wakefield acceleration experiment at CERN which uses the protons from the SPS. It aims to study the self modulation instability of a proton bunch and the acceleration of an externally injected electron beam in the plasma wakefields, during the so called Phase II until the technical stop of LHC and its injector chain (LS2) in 2019. The external electron beam of 0.1 to 1nC charge per bunch will be generated using an S-band photo injector with a high QE semiconducting cathode. A booster linac was designed to allow variable electron energy for the plasma experiments from 16 to 20 MeV. For an RF gun and booster system, emittance control can be highlighted as a challenging transmission task. Once the beam emittance is compensated at the gun exit and the beam is delivered to the booster with an optimum beam envelope, fringing fields and imperfections in the linac become critical for preserving the injection emittance. This paper summarises the rf design studies in order to preserve the initial beam emittance at the entrance of the linac and alternative mitigation schemes in case of emittance growth.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC016
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TUPRC017	Field Flatness and Frequency Tuning of the CLARA High Repetition Rate Photoinjector	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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TUPRC019	Beam Instabilities in Electron Cyclotron Resonance Ion Sources	455
SPWR041	use link to see paper's listing under its alternate paper code
	B.C. Isherwood MSU, East Lansing, Michigan, USA G. Machicoane, G. Pozdeyev NSCL, East Lansing, Michigan, USA G. Machicoane, G. Pozdeyev, Y. Yamazaki FRIB, East Lansing, Michigan, USA
	Funding: This research is funded by joint assistance from the NSF and D.O.E. Accelerator facilities for radioactive beams and low energy nuclear physics such as FRIB require intense, stable ion beam currents in order to achieve required reaction rates for rare and undiscovered isotopes. Presently, the only way to produce intense Continuous Wave beams of highly-charged, medium to heavy-mass ions is with Electron Cyclotron Resonance Ion Sources (ECRIS). The complex nature of these devices causes temporal instabilities to occur, most notably: Slow and fast instabilities. Slow instabilities and drifts, occurring over hours, decay the beam current intensity due to variations in ambient and hardware conditions. These drifts require beam operators to constantly monitor and tune ECRIS plasma parameters in order to maintain experimental beam requirements. Fast instabilities, in the form of ms oscillations, occur at operational parameters needed for high-intensity, high-charge state beams. These oscillations cause sudden drops in beam current of the order of 30%. We present here initial results of recent measurements to investigate these instabilities. Results for slow instabilities indicate a linear decay of beam intensity following a sharp current drop due to a brief source conditioning period. Results for fast instabilities show a relationship between the frequency and amplitude of beam oscillations and the electric potential of the plasma chamber bias disk.
	Poster TUPRC019 [0.817 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC019
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TUPRC020	The TRIUMF ARIEL RF Modulated Thermionic Electron Source	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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TUPRC021	Low-Temperature Properties of 2.6-Cell Cryogenic C-Band RF-Gun Cold Model Cavity	462
	T. Sakai, M. Inagaki, K. Nakao, K. Nogami, K. Takatsuka, T. Tanaka LEBRA, Funabashi, Japan M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan
	Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). Development of a cryogenic C-band photocathode RF gun cavity has been conducted at Nihon University in collaboration with KEK. Improved dimensions of the RF input coupler and the 2.6-cell accelerating structure from the first cold model were determined using the 3D simulation code CST Studio. The high-purity copper cavity was fabricated at KEK with ultraprecision machining and diffusion bonding technique. The low level RF properties of the cavity measured at room temperature have been in good agreement with the predictions based on the CST Studio calculation. Preparations for the 20-K cooling tests of the cavity are underway in KEK and Nihon University. The design of the improved cavity and the results of the cold test at low temperature will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC021
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TUPRC022	UPS Study for CsK2Sb Photocathode	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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TUPRC032	An Analysis of Fast Sputtering Studies for Ion Confinement Time	475
SPWR043	use link to see paper's listing under its alternate paper code
	D.E. Neben, G. Machicoane, A.N. Pham, J.W. Stetson NSCL, East Lansing, Michigan, USA G. Machicoane FRIB, East Lansing, USA G. Parsey MSU, East Lansing, Michigan, USA J.P. Verboncoeur Michigan State University, East Lansing, Michigan, USA
	Funding: This work was supported by Michigan State University and the National Science Foundation: NSF Award Number PHY-1415462 Existing heavy ion facilities such as the National Superconducting Cyclotron Laboratory at Michigan State University rely on Electron Cyclotron Resonance (ECR) ion sources as injectors of highly charged ion beams. Long ion confinement times are necessary to produce dense populations of highly charged ions because of steadily decreasing ionization cross sections with increasing charge state. To further understand ion extraction and confinement we are using a fast sputtering technique first developed at Argonne National Laboratory (ANL) [1] to introduce a small amount of uranium metal into the plasma at a well-defined time. We present an analytical solution to the coupled ion density rate equations for using a piecewise constant neutral density to interpret the fast sputtering method. *R. Vondrasek et al., Rev. Sci. Instrum. 73, 548-551 (2002).
	Poster TUPRC032 [0.699 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC032
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FR1A02	Installation and On-Line Commissioning of EBIS at ATLAS	1022
	P.N. Ostroumov, A. Barcikowski, J.A. Clark, C. Dickerson, M.R. Hendricks, Y. Luo, R.C. Pardo, C.E. Peters, M.A. Power, G. Savard, S.I. Sharamentov, R.C. Vondrasek, G.P. Zinkann ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract DE-AC02-06CH11357. An Electron Beam Ion Source Charge Breeder (EBIS-CB) has been developed at Argonne to breed radioactive beams from the CAlifornium Rare Ion Breeder Upgrade (CARIBU) facility at ATLAS. The CARIBU EBIS-CB has been successfully commissioned offline with an external singly-charged cesium ion source. The EBIS performance meets the breeding requirements to deliver CARIBU beams to ATLAS. EBIS can provide charge-to-mass ratios >=1/7 for all CARIBU beams with breeding times in the range of 6 ms to 30 ms. A record high breeding efficiency of up to 28% into a single charge state of Cs²⁸⁺ has been demonstrated. Following the offline testing EBIS was moved to the front end of ATLAS where the alignment of EBIS was substantially improved and additional beam diagnostic tools both for electron and ion beams were installed. This paper will discuss EBIS improvements and present the results of on-line commissioning.
	Slides FR1A02 [7.717 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-FR1A02
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FR1A03	Intense Beam Production of Highly Charged Ions by the Superconducting ECR Ion Source SECRAL for Heavy Ion Linacs	1027
	L.T. Sun, X. Fang, Y.C. Feng, J.W. Guo, W. Lu, L.Z. Ma, C. Qian, Z. Shen, W. Wu, Y. Yang, W.H. Zhang, X.Z. Zhang, H.W. Zhao, L. Zhu IMP/CAS, Lanzhou, People's Republic of China
	Superconducting ECR ion source (SC-ECRIS) represents the state of the art technologies of ECR ion sources. Existing SC-ECRISs developed in different labs have contributed significantly for ECRIS technology advancement in the last 15 years. Recently the superconducting ECR ion source SECRAL operated at 24 GHz at IMP has produced many new world recorded beam intensities of highly charged ions due to new technologies applied, such as a new microwave coupling scheme. At the meantime, the world first 4th generation ECR ion source operated at 45 GHz is being developed at IMP. All these developments on intense beam production of highly charged ions with superconducting ECR ion source may play significant roles for the next generation heavy ion linacs such as FRIB and Linac of HIAF project. This paper will report the recent developments of intense highly charged heavy ion beams at IMP and the discussion on perspectives of next generation ECRIS for the future heavy ion liancs.
	Slides FR1A03 [13.557 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-FR1A03
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FR1A04	Ion Effects in High Brightness Electron Linac Beams	1032
SPWR030	use link to see paper's listing under its alternate paper code
	S.J. Full, A.C. Bartnik, I.V. Bazarov, J. Dobbins, B.M. Dunham, G.H. Hoffstaetter, K. J. Smith Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Electron beams ionize rest gas particles which then accumulate around them, disturbing beam dynamics and causing background radiation. While this effect has been predicted in the past, linacs have hitherto not suffered from it because of their rather small beam current. The effect of ions increases with larger currents and smaller cross sections of the beam, and it has clearly been observed in Cornell's high-brightness ERL injector for the first time. This presentation will show experimental evidence for ions, demonstrate strategies for their elimination, and will compare the experimental data to theories of beam-ion interactions.
	Slides FR1A04 [5.995 MB]
	Poster FR1A04 [2.630 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-FR1A04
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Paper

Title

Page

MOOP08

Latest News on High Average RF Power Operation at PITZ

59

MOPRC002

use link to see paper's listing under its alternate paper code

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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TUOP03

Developments on the 1.4 MeV/u Pulsed Gas Stripper Cell

387

SPWR028

use link to see paper's listing under its alternate paper code

TUPRC001

use link to see paper's listing under its alternate paper code

P. Scharrer, W.A. Barth, Ch.E. Düllmann, J. Khuyagbaatar, A. Yakushev
HIM, Mainz, Germany
W.A. Barth, M. Bevcic, Ch.E. Düllmann, L. Groening, K.P. Horn, E. Jäger, J. Khuyagbaatar, J. Krier, P. Scharrer, A. Yakushev
GSI, Darmstadt, Germany
Ch.E. Düllmann, P. Scharrer
Mainz University, Mainz, Germany

The GSI UNILAC in combination with SIS18 will serve as a high-current, heavy-ion injector for the FAIR facility. It must meet high demands in terms of beam brilliance at a low duty factor. As part of an UNILAC upgrade program dedicated to FAIR, a new pulsed gas stripper cell was developed, aiming for increased beam intensities inside the post-stripper. The pulsed gas injection is synchronized with the beam pulse timing, enabling a highly-demanded, increased gas density. First tests using uranium beams on a hydrogen target showed a 60%-increased stripping efficiency into the desired 28+ charge state. In 2015, the setup was improved to be able to deliver increased target thicknesses and enhanced flexibility of the gas injection. In recent beam times, the pulsed gas cell was used with various ion-beam types, to test the capabilities for operation at the GSI UNILAC. The stripping of two ion beams in different gases at different gas densities was successfully tested in mixed-beam operation. Charge fractions, beam emittance, and energy-loss were systematically measured using uranium, bismuth, titanium, and argon beams on hydrogen, helium, and nitrogen targets. Selected results will be presented at the conference.

Slides TUOP03 [1.131 MB]

Poster TUOP03 [5.943 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUOP03

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TUPRC015

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

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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TUPRC016

S-Band Booster Design and Emittance Preservation for the Awake e-Injector

449

O. Mete Apsimon, R. Apsimon, G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
S. Döbert
CERN, Geneva, Switzerland
G.X. Xia
UMAN, Manchester, United Kingdom

AWAKE is a proton driven plasma wakefield acceleration experiment at CERN which uses the protons from the SPS. It aims to study the self modulation instability of a proton bunch and the acceleration of an externally injected electron beam in the plasma wakefields, during the so called Phase II until the technical stop of LHC and its injector chain (LS2) in 2019. The external electron beam of 0.1 to 1nC charge per bunch will be generated using an S-band photo injector with a high QE semiconducting cathode. A booster linac was designed to allow variable electron energy for the plasma experiments from 16 to 20 MeV. For an RF gun and booster system, emittance control can be highlighted as a challenging transmission task. Once the beam emittance is compensated at the gun exit and the beam is delivered to the booster with an optimum beam envelope, fringing fields and imperfections in the linac become critical for preserving the injection emittance. This paper summarises the rf design studies in order to preserve the initial beam emittance at the entrance of the linac and alternative mitigation schemes in case of emittance growth.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC016

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TUPRC017

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

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 •

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TUPRC019

Beam Instabilities in Electron Cyclotron Resonance Ion Sources

455

SPWR041

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B.C. Isherwood
MSU, East Lansing, Michigan, USA
G. Machicoane, G. Pozdeyev
NSCL, East Lansing, Michigan, USA
G. Machicoane, G. Pozdeyev, Y. Yamazaki
FRIB, East Lansing, Michigan, USA

Funding: This research is funded by joint assistance from the NSF and D.O.E.
Accelerator facilities for radioactive beams and low energy nuclear physics such as FRIB require intense, stable ion beam currents in order to achieve required reaction rates for rare and undiscovered isotopes. Presently, the only way to produce intense Continuous Wave beams of highly-charged, medium to heavy-mass ions is with Electron Cyclotron Resonance Ion Sources (ECRIS). The complex nature of these devices causes temporal instabilities to occur, most notably: Slow and fast instabilities. Slow instabilities and drifts, occurring over hours, decay the beam current intensity due to variations in ambient and hardware conditions. These drifts require beam operators to constantly monitor and tune ECRIS plasma parameters in order to maintain experimental beam requirements. Fast instabilities, in the form of ms oscillations, occur at operational parameters needed for high-intensity, high-charge state beams. These oscillations cause sudden drops in beam current of the order of 30%. We present here initial results of recent measurements to investigate these instabilities. Results for slow instabilities indicate a linear decay of beam intensity following a sharp current drop due to a brief source conditioning period. Results for fast instabilities show a relationship between the frequency and amplitude of beam oscillations and the electric potential of the plasma chamber bias disk.

Poster TUPRC019 [0.817 MB]

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TUPRC020

The TRIUMF ARIEL RF Modulated Thermionic Electron Source

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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TUPRC021

Low-Temperature Properties of 2.6-Cell Cryogenic C-Band RF-Gun Cold Model Cavity

462

T. Sakai, M. Inagaki, K. Nakao, K. Nogami, K. Takatsuka, T. Tanaka
LEBRA, Funabashi, Japan
M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
Development of a cryogenic C-band photocathode RF gun cavity has been conducted at Nihon University in collaboration with KEK. Improved dimensions of the RF input coupler and the 2.6-cell accelerating structure from the first cold model were determined using the 3D simulation code CST Studio. The high-purity copper cavity was fabricated at KEK with ultraprecision machining and diffusion bonding technique. The low level RF properties of the cavity measured at room temperature have been in good agreement with the predictions based on the CST Studio calculation. Preparations for the 20-K cooling tests of the cavity are underway in KEK and Nihon University. The design of the improved cavity and the results of the cold test at low temperature will be discussed.

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TUPRC022

UPS Study for CsK2Sb Photocathode

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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TUPRC032

An Analysis of Fast Sputtering Studies for Ion Confinement Time

475

SPWR043

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D.E. Neben, G. Machicoane, A.N. Pham, J.W. Stetson
NSCL, East Lansing, Michigan, USA
G. Machicoane
FRIB, East Lansing, USA
G. Parsey
MSU, East Lansing, Michigan, USA
J.P. Verboncoeur
Michigan State University, East Lansing, Michigan, USA

Funding: This work was supported by Michigan State University and the National Science Foundation: NSF Award Number PHY-1415462
Existing heavy ion facilities such as the National Superconducting Cyclotron Laboratory at Michigan State University rely on Electron Cyclotron Resonance (ECR) ion sources as injectors of highly charged ion beams. Long ion confinement times are necessary to produce dense populations of highly charged ions because of steadily decreasing ionization cross sections with increasing charge state. To further understand ion extraction and confinement we are using a fast sputtering technique first developed at Argonne National Laboratory (ANL) [1] to introduce a small amount of uranium metal into the plasma at a well-defined time. We present an analytical solution to the coupled ion density rate equations for using a piecewise constant neutral density to interpret the fast sputtering method.
*R. Vondrasek et al., Rev. Sci. Instrum. 73, 548-551 (2002).

Poster TUPRC032 [0.699 MB]

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FR1A02

Installation and On-Line Commissioning of EBIS at ATLAS

1022

P.N. Ostroumov, A. Barcikowski, J.A. Clark, C. Dickerson, M.R. Hendricks, Y. Luo, R.C. Pardo, C.E. Peters, M.A. Power, G. Savard, S.I. Sharamentov, R.C. Vondrasek, G.P. Zinkann
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract DE-AC02-06CH11357.
An Electron Beam Ion Source Charge Breeder (EBIS-CB) has been developed at Argonne to breed radioactive beams from the CAlifornium Rare Ion Breeder Upgrade (CARIBU) facility at ATLAS. The CARIBU EBIS-CB has been successfully commissioned offline with an external singly-charged cesium ion source. The EBIS performance meets the breeding requirements to deliver CARIBU beams to ATLAS. EBIS can provide charge-to-mass ratios >=1/7 for all CARIBU beams with breeding times in the range of 6 ms to 30 ms. A record high breeding efficiency of up to 28% into a single charge state of Cs²⁸⁺ has been demonstrated. Following the offline testing EBIS was moved to the front end of ATLAS where the alignment of EBIS was substantially improved and additional beam diagnostic tools both for electron and ion beams were installed. This paper will discuss EBIS improvements and present the results of on-line commissioning.

Slides FR1A02 [7.717 MB]

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FR1A03

Intense Beam Production of Highly Charged Ions by the Superconducting ECR Ion Source SECRAL for Heavy Ion Linacs

1027

L.T. Sun, X. Fang, Y.C. Feng, J.W. Guo, W. Lu, L.Z. Ma, C. Qian, Z. Shen, W. Wu, Y. Yang, W.H. Zhang, X.Z. Zhang, H.W. Zhao, L. Zhu
IMP/CAS, Lanzhou, People's Republic of China

Superconducting ECR ion source (SC-ECRIS) represents the state of the art technologies of ECR ion sources. Existing SC-ECRISs developed in different labs have contributed significantly for ECRIS technology advancement in the last 15 years. Recently the superconducting ECR ion source SECRAL operated at 24 GHz at IMP has produced many new world recorded beam intensities of highly charged ions due to new technologies applied, such as a new microwave coupling scheme. At the meantime, the world first 4th generation ECR ion source operated at 45 GHz is being developed at IMP. All these developments on intense beam production of highly charged ions with superconducting ECR ion source may play significant roles for the next generation heavy ion linacs such as FRIB and Linac of HIAF project. This paper will report the recent developments of intense highly charged heavy ion beams at IMP and the discussion on perspectives of next generation ECRIS for the future heavy ion liancs.

Slides FR1A03 [13.557 MB]

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FR1A04

Ion Effects in High Brightness Electron Linac Beams

1032

SPWR030

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S.J. Full, A.C. Bartnik, I.V. Bazarov, J. Dobbins, B.M. Dunham, G.H. Hoffstaetter, K. J. Smith
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Electron beams ionize rest gas particles which then accumulate around them, disturbing beam dynamics and causing background radiation. While this effect has been predicted in the past, linacs have hitherto not suffered from it because of their rather small beam current. The effect of ions increases with larger currents and smaller cross sections of the beam, and it has clearly been observed in Cornell's high-brightness ERL injector for the first time. This presentation will show experimental evidence for ions, demonstrate strategies for their elimination, and will compare the experimental data to theories of beam-ion interactions.

Slides FR1A04 [5.995 MB]

Poster FR1A04 [2.630 MB]

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