IPAC2012 - List of Authors (Liang, X.)

Paper	Title	Page
MOPPP028	SRF Photoinjector for Proof-of-principle Experiment of Coherent Electron Cooling at RHIC	622
	D. Kayran, S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, X. Liang, G.T. McIntyre, I. Pinayev, B. Sheehy, J. Skaritka, T. Srinivasan-Rao, R. Than, J.E. Tuozzolo, Q. Wu, T. Xin BNL, Upton, Long Island, New York, USA V. Litvinenko, M. Ruiz-Osés 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 and by Stony Brook DOE grant DE-SC0005713. Coherent Electron Cooling (CEC) based on FEL amplifier promises to be a very good way to cool protons and ions at high energies. A proof of principle experiment to demonstrate cooling at 40 GeV/u is under construction at BNL. One of possible sources to provide sufficient quality electron beam for this experiment is a SRF photoinjector. In this paper we discuss design and simulated performance of the photoinjector based on existing 112 MHz SRF gun and newly designed single-cavity SRF linac operating at 704 MHz.

WEPPC111	Multipacting Simulation ADN Test Results of BNL 704 MHz SRF Gun	2480
	W. Xu, S.A. Belomestnykh, I. Ben-Zvi, C. Cullen, H. Hahn, X. Liang, G.T. McIntyre, D. Pate, S.P. Pontieri, C. Schultheiss, T. Seda, T.N. Tallerico, R. Than, R.J. Todd, S.J. Tuozzolo, A. Zaltsman BNL, Upton, Long Island, New York, USA J. Dai SBU, Stony Brook, New York, USA L.R. Hammons Stony Brook University, Stony Brook, USA
	Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The BNL 704 MHz SRF gun has a grooved choke joint to support the photo-cathode. Due to the distortion of grooves at the choke joint during the BCP for the choke joint, several multipacting barriers showed up when it was tested with Nb cathode stalk at JLab. We built a setup to use the spare large grain SRF cavity to test and condition the multipacting at BNL with various power sources. The test is carried out with three steps: cavity, cavity with Nb cathode stalk, and cavity with copper cathode stalk. This paper summarizes the results of multipacting simulation, and presents large grain cavity test setup and the test results.

MOPPP049	Deposition and In-Situ Characterization of Alkali Antimonide Photocathodes	670
	X. Liang SBU, Stony Brook, New York, USA K. Attenkofer ANL, Argonne, USA I. Ben-Zvi, M. Ruiz-Osés Stony Brook University, Stony Brook, USA H.A. Padmore, T. Vecchione LBNL, Berkeley, California, USA S.G. Schubert HZB, Berlin, Germany J. Smedley BNL, Upton, Long Island, New York, USA
	Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences of the U. S. Department of Energy, under Contract No. KC0407-ALSJNT-I0013, and DE-SC0005713. Alkali antimonide cathodes have the potential to provide high quantum efficiency for visible light, and are significantly more tolerant of vacuum contaminants than GaAs, so they are attractive for high-average-current photoinjectors to generate high quality electron beams. These cathodes are crystalline; however, standard growth recipes used today do not produce large crystals. We have grown multi-alkali cathodes on silicon and molybdenum substrates with in-situ X-ray diffraction (XRD) and X-ray reflection (XRR) analysis. The correlation of the cathode structure to the growth parameters and quantum efficiency was explored. During the deposition and evaporation of Sb and K layers, the possibility of selective growth of specific crystalline orientation was observed via X-ray diffraction.

TUPPD082	Simulations of Multipacting in the Cathode Stalk and FPC of 112 MHz Superconducting Electron Gun	1593
	T. Xin, X. Liang Stony Brook University, Stony Brook, USA S.A. Belomestnykh, I. Ben-Zvi, T. Rao, J. Skaritka, E. Wang, Q. Wu BNL, Upton, Long Island, New York, USA X. Chang Far-Tech, Inc., San Diego, California, USA
	Funding: Work is supported at BNL by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The work at Stony Brook is supported by the US DOE under grant DE-SC0005713. A 112 MHz superconducting quarter-wave resonator electron gun will be used as the injector of the Coherent Electron Cooling (CEC) proof-of-principle experiment at BNL. Furthermore, this electron gun can be used for testing of the performance of various high quantum efficiency photocathodes. In a previous paper, we presented the design of the cathode stalks and a Fundamental Power Coupler (FPC). In this paper we present updated designs of the cathode stalk and FPC. Multipacting in the cathode stalk and FPC was simulated using three different codes, Multipac, CST particle studio and FishPact respectively. All simulation results show no serious multipacting in the cathode stalk structure and FPC.

Paper

Title

Page

SRF Photoinjector for Proof-of-principle Experiment of Coherent Electron Cooling at RHIC

622

D. Kayran, S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, X. Liang, G.T. McIntyre, I. Pinayev, B. Sheehy, J. Skaritka, T. Srinivasan-Rao, R. Than, J.E. Tuozzolo, Q. Wu, T. Xin
BNL, Upton, Long Island, New York, USA
V. Litvinenko, M. Ruiz-Osés
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 and by Stony Brook DOE grant DE-SC0005713.
Coherent Electron Cooling (CEC) based on FEL amplifier promises to be a very good way to cool protons and ions at high energies. A proof of principle experiment to demonstrate cooling at 40 GeV/u is under construction at BNL. One of possible sources to provide sufficient quality electron beam for this experiment is a SRF photoinjector. In this paper we discuss design and simulated performance of the photoinjector based on existing 112 MHz SRF gun and newly designed single-cavity SRF linac operating at 704 MHz.

WEPPC111

Multipacting Simulation ADN Test Results of BNL 704 MHz SRF Gun

2480

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, C. Cullen, H. Hahn, X. Liang, G.T. McIntyre, D. Pate, S.P. Pontieri, C. Schultheiss, T. Seda, T.N. Tallerico, R. Than, R.J. Todd, S.J. Tuozzolo, A. Zaltsman
BNL, Upton, Long Island, New York, USA
J. Dai
SBU, Stony Brook, New York, USA
L.R. Hammons
Stony Brook University, Stony Brook, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The BNL 704 MHz SRF gun has a grooved choke joint to support the photo-cathode. Due to the distortion of grooves at the choke joint during the BCP for the choke joint, several multipacting barriers showed up when it was tested with Nb cathode stalk at JLab. We built a setup to use the spare large grain SRF cavity to test and condition the multipacting at BNL with various power sources. The test is carried out with three steps: cavity, cavity with Nb cathode stalk, and cavity with copper cathode stalk. This paper summarizes the results of multipacting simulation, and presents large grain cavity test setup and the test results.

MOPPP049

Deposition and In-Situ Characterization of Alkali Antimonide Photocathodes

670

X. Liang
SBU, Stony Brook, New York, USA
K. Attenkofer
ANL, Argonne, USA
I. Ben-Zvi, M. Ruiz-Osés
Stony Brook University, Stony Brook, USA
H.A. Padmore, T. Vecchione
LBNL, Berkeley, California, USA
S.G. Schubert
HZB, Berlin, Germany
J. Smedley
BNL, Upton, Long Island, New York, USA

Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences of the U. S. Department of Energy, under Contract No. KC0407-ALSJNT-I0013, and DE-SC0005713.
Alkali antimonide cathodes have the potential to provide high quantum efficiency for visible light, and are significantly more tolerant of vacuum contaminants than GaAs, so they are attractive for high-average-current photoinjectors to generate high quality electron beams. These cathodes are crystalline; however, standard growth recipes used today do not produce large crystals. We have grown multi-alkali cathodes on silicon and molybdenum substrates with in-situ X-ray diffraction (XRD) and X-ray reflection (XRR) analysis. The correlation of the cathode structure to the growth parameters and quantum efficiency was explored. During the deposition and evaporation of Sb and K layers, the possibility of selective growth of specific crystalline orientation was observed via X-ray diffraction.

TUPPD082

Simulations of Multipacting in the Cathode Stalk and FPC of 112 MHz Superconducting Electron Gun

1593

T. Xin, X. Liang
Stony Brook University, Stony Brook, USA
S.A. Belomestnykh, I. Ben-Zvi, T. Rao, J. Skaritka, E. Wang, Q. Wu
BNL, Upton, Long Island, New York, USA
X. Chang
Far-Tech, Inc., San Diego, California, USA

Funding: Work is supported at BNL by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The work at Stony Brook is supported by the US DOE under grant DE-SC0005713.
A 112 MHz superconducting quarter-wave resonator electron gun will be used as the injector of the Coherent Electron Cooling (CEC) proof-of-principle experiment at BNL. Furthermore, this electron gun can be used for testing of the performance of various high quantum efficiency photocathodes. In a previous paper, we presented the design of the cathode stalks and a Fundamental Power Coupler (FPC). In this paper we present updated designs of the cathode stalk and FPC. Multipacting in the cathode stalk and FPC was simulated using three different codes, Multipac, CST particle studio and FishPact respectively. All simulation results show no serious multipacting in the cathode stalk structure and FPC.