PAC2013 - List of Authors (Liang, X.)

Paper	Title	Page
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.

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.

THPAC18	Progress on Growth of a Multi-alkali Photocathode for ERL	1181
	E. Wang, S.A. Belomestnykh, I. Ben-Zvi, T. Rao, J. Smedley BNL, Upton, Long Island, New York, USA I. Ben-Zvi, M. Ruiz-Osés Stony Brook University, Stony Brook, USA X. Liang SBU, Stony Brook, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and DOE grant at Stony Brook DE-SC0005713 K2CsSb is a robust photocathode capable of generating electron beams with high peak, high average current and low thermal emittance. During the last two year, a great improvement in the design and fabrication of a reliable deposition system suitable for K2CsSb cathode growth and its insertion into BNL high current ERL SRF gun has been achieved. A standard procedure for the growth of multi-alkali cathodes combined with another procedure to transport these cathodes into the SRF gun was developed. The first cathode growth on a copper insertion was ready to mount into the 704MHz gun. In this article, we will describe the progress of cathode growth and transportation for ERL project. In particular, laser heating and the cathode growth on Ta will be included.

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.

THPAC17	Alkali Antimonide Photocathodes for Everyone	1178
	J. Smedley, K. Attenkofer, S.G. Schubert BNL, Upton, Long Island, New York, USA I. Ben-Zvi, X. Liang, E.M. Muller, M. Ruiz-Osés Stony Brook University, Stony Brook, USA J. DeFazio PHOTONIS USA PENNSYLVANIA, INC., Lancaster, USA H.A. Padmore, J.J. Wong LBNL, Berkeley, California, USA J. Xie ANL, Argonne, USA
	Funding: The authors wish to acknowledge the support of the US DOE, under Contract No. KC0407-ALSJNT-I0013, DE-AC02-98CH10886 and DE-SC0005713. Use of CHESS is supported by NSF award DMR-0936384. Alkali Antimonide photocathodes have yielded the highest current on record for any photoinjector source (75 mA), with QE of ~10% for green light. However, traditional growth methods for these cathodes yield material that is inherently rough, leading to rise of the intrinsic emittance for high gradient injectors such as those for next-generation light sources. It this presentation we will explore the origin of roughness in these materials, as well as the growth dynamics, using in situ and in operando techniques, including Grazing Incidence X-ray Diffraction, Grazing Incidence Small Angle X-ray Scattering, X-ray reflectivity and in vacuum Atomic Force Microscopy.

Paper

Title

Page

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.

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.

THPAC18

Progress on Growth of a Multi-alkali Photocathode for ERL

1181

E. Wang, S.A. Belomestnykh, I. Ben-Zvi, T. Rao, J. Smedley
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi, M. Ruiz-Osés
Stony Brook University, Stony Brook, USA
X. Liang
SBU, Stony Brook, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and DOE grant at Stony Brook DE-SC0005713
K2CsSb is a robust photocathode capable of generating electron beams with high peak, high average current and low thermal emittance. During the last two year, a great improvement in the design and fabrication of a reliable deposition system suitable for K2CsSb cathode growth and its insertion into BNL high current ERL SRF gun has been achieved. A standard procedure for the growth of multi-alkali cathodes combined with another procedure to transport these cathodes into the SRF gun was developed. The first cathode growth on a copper insertion was ready to mount into the 704MHz gun. In this article, we will describe the progress of cathode growth and transportation for ERL project. In particular, laser heating and the cathode growth on Ta will be included.

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.

THPAC17

Alkali Antimonide Photocathodes for Everyone

1178

J. Smedley, K. Attenkofer, S.G. Schubert
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi, X. Liang, E.M. Muller, M. Ruiz-Osés
Stony Brook University, Stony Brook, USA
J. DeFazio
PHOTONIS USA PENNSYLVANIA, INC., Lancaster, USA
H.A. Padmore, J.J. Wong
LBNL, Berkeley, California, USA
J. Xie
ANL, Argonne, USA

Funding: The authors wish to acknowledge the support of the US DOE, under Contract No. KC0407-ALSJNT-I0013, DE-AC02-98CH10886 and DE-SC0005713. Use of CHESS is supported by NSF award DMR-0936384.
Alkali Antimonide photocathodes have yielded the highest current on record for any photoinjector source (75 mA), with QE of ~10% for green light. However, traditional growth methods for these cathodes yield material that is inherently rough, leading to rise of the intrinsic emittance for high gradient injectors such as those for next-generation light sources. It this presentation we will explore the origin of roughness in these materials, as well as the growth dynamics, using in situ and in operando techniques, including Grazing Incidence X-ray Diffraction, Grazing Incidence Small Angle X-ray Scattering, X-ray reflectivity and in vacuum Atomic Force Microscopy.