PAC2013 - List of Authors (Wu, Q.)

Paper	Title	Page
TUPSM06	The Cathode Preparation Chamber for the DC High Current High Polarization Gun	640
	O.H. Rahman, I. Ben-Zvi, D.M. Gassner, A.I. Pikin, T. Rao, E.J. Riehn, B. Sheehy, J. Skaritka, E. Wang, Q. Wu BNL, Upton, Long Island, New York, USA I. Ben-Zvi 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. A compact cathode preparation chamber for the high current high polarization gun for the proposed eRHIC project has been designed and assembled at Brookhaven National Laboratory. This preparation chamber will be used to activate GaAs photocathodes to be used in the Gatling gun. The chamber is capable of achieving XHV on a consistent basis. Bulk GaAs samples were activated in this chamber with standard QE for the respective wavelength. In this paper, we discuss the design of this vacuum system, the heat cleaning and the activation procedure for the GaAs sample which will eventually be followed for the Gatling gun.

WEPAC07	Mechanical Design of 112 MHz SRF Gun FPC for CeC PoP Experiment	802
	J.C. Brutus, S.A. Belomestnykh, Y. Huang, V. Litvinenko, G.J. Mahler, I. Pinayev, J. Skaritka, L. Snydstrup, R. Than, J.E. Tuozzolo, Q. Wu, T. Xin BNL, Upton, Long Island, New York, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. A Quarter-Wave Resonator (QWR) type SRF gun operating at 112 MHz will be used for Coherent Electron Cooling Proof of Principle (CeC PoP) system under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The CeC PoP experiment will demonstrate the ability of relativistic electrons to cool a single bunch of heavy ions in RHIC. This cavity is designed to generate a 2 MeV, high charge (several nC), low repetition rate (78 kHz) electron beam using a new fundamental power coupler (FPC) design approach. Structural and thermal analysis, using ANSYS were performed to confirm the FPC structural stability and to calculate the deflection due to heat load from RF power generation. This paper provides an overview of the design, structural and thermal analysis, test results, and FPC tuning drive system for the 112 MHz gun.

THPAC12	Preparation and Investigation of Antimony Thin Films for Multi-Alkali Photocathodes	1163
	X. Liang, K. Attenkofer, T. Rao, S.G. Schubert, J. Smedley, E. Wang, Q. Wu BNL, Upton, Long Island, New York, USA I. Ben-Zvi, M. Ruiz-Osés Stony Brook University, Stony Brook, USA J. Jordan-Sweet IBM T. J. Watson Center, Yorktown Heights, New York, USA H.A. Padmore, J.J. Wong LBNL, Berkeley, California, USA
	Funding: Work is supported at BNL by Brookhaven Science Associates, LLC under Contract No. DEAC02-98CH10886 with the U.S. DOE. The work at Stony Brook is supported by the US DOE under grant DE-SC0005713. Multialikali antimonide cathodes provide high visible light quantum efficiency, with low thermal emittance and are excellent candidate materials for high average current next generation ERLs or high repetition rate FELs. Although these materials have some excellent characteristics, control of the growth mode of the thin film and ultimately the surface roughness is difficult and will effect the emittance that can be obtained in high gradient fields. To complement our growth studies of crystalline phases using x-ray diffraction studies, here we use the technique of grazing incidence small angle x-ray scattering (GI-SAXS) and atomic force microscopy (AFM) to measure the roughness as a function of film thickness. In this study, we demonstrate these techniques as applied to the growth of Sb, for a range of thicknesses, temperatures and growth rates, and show the wide range of moprphologies that can be formed with relatively minor changes in deposition conditions.

THPAC34	Diamond Amplifier Design and Preliminary Test Results	1211
	T. Xin, S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA S.A. Belomestnykh, I. Ben-Zvi, T. Rao, J. Skaritka, J. Smedley, E. Wang, Q. Wu BNL, Upton, Long Island, New York, USA M. Gaowei, E.M. Muller SBU, Stony Brook, New York, 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. Diamond as a large energy gap material can be easily made into a negative electron affinity (NEA) device. Using a few keV primary electrons as input and a few kV bias, the NEA diamond will emit cold electrons into vacuum with a large gain. We had tested and reported the performance of the diamond amplifier in our DC system somewhere else. The best amplification achieved so far was above 170. Next step of the experiment is to test the diamond amplifier in the 112 MHz superconducting RF electron gun. In this report we describe the design and simulations of the diamond amplifier to be tested in our SRF gun, show the finished amplifier containing the DC primary gun and light optics. We also provide preliminary test results of the laser and electron beam transport.

THPAC35	Multipacting Study of 112 MHz SRF Electron Gun	1214
	T. Xin, S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA S.A. Belomestnykh, I. Ben-Zvi, X. Liang, T. Rao, J. Skaritka, E. Wang, Q. Wu BNL, Upton, Long Island, New York, USA C.H. Boulware, T.L. Grimm Niowave, Inc., Lansing, Michigan, USA X. Liang SBU, Stony Brook, New York, 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. The 112 MHz quarter wave superconducting electron gun was designed and built as an injector for the coherent electron cooling experiment. Besides that, the gun is suitable for testing various types of photocathodes thanks to its specially designed cathode holder. In recent RF tests of the gun at 4 K, the accelerating voltage reached 0.9 MV CW and more than 1 MV in pulsed mode. During this testing, we observed several multipacting barriers at low electromagnetic field levels. Since the final setup of the gun will be different from the cool down test configuration, we want to understand the exact location of the multipacting sites. We used Track3P to simulate multipacting. The results show several resonant trajectories that might be responsible for the observed barriers, but fortunately no strong multipacting barriers have been found in the cavity.

THPHO06	SRF and RF Systems for CeC PoP Experiment	1310
	S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, D. Kayran, V. Litvinenko, P. Orfin, I. Pinayev, T. Rao, B. Sheehy, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, M. Ruiz-Osés, T. Xin Stony Brook University, Stony Brook, USA C.H. Boulware, T.L. Grimm Niowave, Inc., Lansing, Michigan, USA Y. Huang Fermilab, Batavia, USA X. Liang SBU, Stony Brook, New York, USA P.A. McIntosh, A.J. Moss, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. Efforts to experimentally prove a concept of the coherent electron cooling are underway at BNL. A short 22-MeV linac will provide high charge, low repetition rate beam to cool a single ion bunch in RHIC. The linac will consist of a 112 MHz SRF gun, two 500 MHz normal conducting bunching cavities and a 704 MHz five-cell accelerating SRF cavity. The paper describes the SRF and RF systems, the linac layout, and discusses the project status, first test results and schedule.

Paper

Title

Page

The Cathode Preparation Chamber for the DC High Current High Polarization Gun

640

O.H. Rahman, I. Ben-Zvi, D.M. Gassner, A.I. Pikin, T. Rao, E.J. Riehn, B. Sheehy, J. Skaritka, E. Wang, Q. Wu
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
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.
A compact cathode preparation chamber for the high current high polarization gun for the proposed eRHIC project has been designed and assembled at Brookhaven National Laboratory. This preparation chamber will be used to activate GaAs photocathodes to be used in the Gatling gun. The chamber is capable of achieving XHV on a consistent basis. Bulk GaAs samples were activated in this chamber with standard QE for the respective wavelength. In this paper, we discuss the design of this vacuum system, the heat cleaning and the activation procedure for the GaAs sample which will eventually be followed for the Gatling gun.

WEPAC07

Mechanical Design of 112 MHz SRF Gun FPC for CeC PoP Experiment

802

J.C. Brutus, S.A. Belomestnykh, Y. Huang, V. Litvinenko, G.J. Mahler, I. Pinayev, J. Skaritka, L. Snydstrup, R. Than, J.E. Tuozzolo, Q. Wu, T. Xin
BNL, Upton, Long Island, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
A Quarter-Wave Resonator (QWR) type SRF gun operating at 112 MHz will be used for Coherent Electron Cooling Proof of Principle (CeC PoP) system under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The CeC PoP experiment will demonstrate the ability of relativistic electrons to cool a single bunch of heavy ions in RHIC. This cavity is designed to generate a 2 MeV, high charge (several nC), low repetition rate (78 kHz) electron beam using a new fundamental power coupler (FPC) design approach. Structural and thermal analysis, using ANSYS were performed to confirm the FPC structural stability and to calculate the deflection due to heat load from RF power generation. This paper provides an overview of the design, structural and thermal analysis, test results, and FPC tuning drive system for the 112 MHz gun.

THPAC12

Preparation and Investigation of Antimony Thin Films for Multi-Alkali Photocathodes

1163

X. Liang, K. Attenkofer, T. Rao, S.G. Schubert, J. Smedley, E. Wang, Q. Wu
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi, M. Ruiz-Osés
Stony Brook University, Stony Brook, USA
J. Jordan-Sweet
IBM T. J. Watson Center, Yorktown Heights, New York, USA
H.A. Padmore, J.J. Wong
LBNL, Berkeley, California, USA

Funding: Work is supported at BNL by Brookhaven Science Associates, LLC under Contract No. DEAC02-98CH10886 with the U.S. DOE. The work at Stony Brook is supported by the US DOE under grant DE-SC0005713.
Multialikali antimonide cathodes provide high visible light quantum efficiency, with low thermal emittance and are excellent candidate materials for high average current next generation ERLs or high repetition rate FELs. Although these materials have some excellent characteristics, control of the growth mode of the thin film and ultimately the surface roughness is difficult and will effect the emittance that can be obtained in high gradient fields. To complement our growth studies of crystalline phases using x-ray diffraction studies, here we use the technique of grazing incidence small angle x-ray scattering (GI-SAXS) and atomic force microscopy (AFM) to measure the roughness as a function of film thickness. In this study, we demonstrate these techniques as applied to the growth of Sb, for a range of thicknesses, temperatures and growth rates, and show the wide range of moprphologies that can be formed with relatively minor changes in deposition conditions.

THPAC34

Diamond Amplifier Design and Preliminary Test Results

1211

T. Xin, S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
S.A. Belomestnykh, I. Ben-Zvi, T. Rao, J. Skaritka, J. Smedley, E. Wang, Q. Wu
BNL, Upton, Long Island, New York, USA
M. Gaowei, E.M. Muller
SBU, Stony Brook, New York, 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.
Diamond as a large energy gap material can be easily made into a negative electron affinity (NEA) device. Using a few keV primary electrons as input and a few kV bias, the NEA diamond will emit cold electrons into vacuum with a large gain. We had tested and reported the performance of the diamond amplifier in our DC system somewhere else. The best amplification achieved so far was above 170. Next step of the experiment is to test the diamond amplifier in the 112 MHz superconducting RF electron gun. In this report we describe the design and simulations of the diamond amplifier to be tested in our SRF gun, show the finished amplifier containing the DC primary gun and light optics. We also provide preliminary test results of the laser and electron beam transport.

THPAC35

Multipacting Study of 112 MHz SRF Electron Gun

1214

T. Xin, S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
S.A. Belomestnykh, I. Ben-Zvi, X. Liang, T. Rao, J. Skaritka, E. Wang, Q. Wu
BNL, Upton, Long Island, New York, USA
C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
X. Liang
SBU, Stony Brook, New York, 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.
The 112 MHz quarter wave superconducting electron gun was designed and built as an injector for the coherent electron cooling experiment. Besides that, the gun is suitable for testing various types of photocathodes thanks to its specially designed cathode holder. In recent RF tests of the gun at 4 K, the accelerating voltage reached 0.9 MV CW and more than 1 MV in pulsed mode. During this testing, we observed several multipacting barriers at low electromagnetic field levels. Since the final setup of the gun will be different from the cool down test configuration, we want to understand the exact location of the multipacting sites. We used Track3P to simulate multipacting. The results show several resonant trajectories that might be responsible for the observed barriers, but fortunately no strong multipacting barriers have been found in the cavity.

THPHO06

SRF and RF Systems for CeC PoP Experiment

1310

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, D. Kayran, V. Litvinenko, P. Orfin, I. Pinayev, T. Rao, B. Sheehy, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, M. Ruiz-Osés, T. Xin
Stony Brook University, Stony Brook, USA
C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
Y. Huang
Fermilab, Batavia, USA
X. Liang
SBU, Stony Brook, New York, USA
P.A. McIntosh, A.J. Moss, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
Efforts to experimentally prove a concept of the coherent electron cooling are underway at BNL. A short 22-MeV linac will provide high charge, low repetition rate beam to cool a single ion bunch in RHIC. The linac will consist of a 112 MHz SRF gun, two 500 MHz normal conducting bunching cavities and a 704 MHz five-cell accelerating SRF cavity. The paper describes the SRF and RF systems, the linac layout, and discusses the project status, first test results and schedule.