IPAC2012 - List of Authors (Wu, Q.)

Paper

Title

Page

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.

TUPPR084

HOM Damping and Multipacting Analysis of the Quarter-wave Crab Cavity

2020

Q. Wu, S.A. Belomestnykh, I. Ben-Zvi
BNL, Upton, Long Island, New York, USA
R. Calaga
CERN, Geneva, Switzerland

The Quarter-Wave Crab Cavity design has been analyzed further to accommodate LHC requirements. The goal for the design is to provide strong deflecting voltage to the proton bunches at the IP, while keeping the effective length as short as possible. We will evaluate the Higher Order Mode damping with two magnetic coupling dampers of 90 degrees apart. In this paper, we also show possible multipacting locations which are simulated by 3D code.

WEPPC027

A Quarter Wave Design for Crab Crossing in the LHC

2260

R. Calaga
CERN, Geneva, Switzerland
S.A. Belomestnykh, I. Ben-Zvi, Q. Wu
BNL, Upton, Long Island, New York, USA

Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
The aperture constraints of the LHC interaction region and the alternating crossing schemes at two collision points calls for a superconducting deflecting cavity with very compact dimensions at low frequencies for the purpose of crab crossing. A new concept of using a superconducting 1/4-wave design, ideally suited to address the LHC constraints at 400 MHz, is proposed. The optimized RF cavity design and associated advantages of using a 1/4 wave resonator are presented. Aspects related to higher order mode damping, multipacting and frequency tuning are also addressed.

WEPPC110

3D Simulations of Multipacting in the 56 MHz SRF Cavity

2477

Q. Wu, S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA
L. Ge, C. Ko, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 56 MHz SRF Quarter-Wave Resonator (QWR) is designed for RHIC as a storage cavity to improve the collider performance. 2D multipacting simulation has been done for the cavity alone. Ripples were added to the outer body of the cavity for multipacting suppression based on the simulation findings. During operation, there will be four higher order mode (HOM) couplers and a fundamental power coupler (FPC) inserted through the end ports of the cavity and a fundamental mode damper (FD) inserted through a special port on the outer body. All of these components will be exposed to high RF fields. In this presentation we compare 2D and 3D codes simulation results for multipacting in the cavity. We also report 3D simulation results for multipacting simulation at the couplers.

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.

WEPPC109

Superconducting RF Systems for eRHIC

2474

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, H. Hahn, D. Kayran, G.J. Mahler, G.T. McIntyre, C. Pai, I. Pinayev, V. Ptitsyn, J. Skaritka, R. Than, J.E. Tuozzolo, Q. Wu, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, V. Litvinenko, T. Xin
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.
Future electron-hadron collider eRHIC will consist of a six-pass 30-GeV electron ERL and one of RHIC storage rings operating with energy up to 250 GeV. The collider design extensively utilizes superconducting RF (SRF) technology in both electron and hadron parts. This paper describes various SRF systems, their requirements and parameters.

THAP01

Secondary-electron Emission from Hydrogen-terminated Diamond

3223

E. Wang, I. Ben-Zvi, T. Rao, Q. Wu
BNL, Upton, Long Island, New York, USA
D.A. Dimitrov
Tech-X, Boulder, Colorado, USA
T. Xin
Stony Brook University, Stony Brook, USA

Diamond amplifiers demonstrably are an electron source with the potential to support high-brightness, high-average-current emission into a vacuum. We recently developed a reliable hydrogenation procedure for the diamond amplifier. The systematic study of hydrogenation resulted in the reproducible fabrication of high gain diamond amplifier. Furthermore, we measured the emission probability of diamond amplifier as a function of the external field and modeled the process with resulting changes in the vacuum level due to the Schottky effect. We demonstrated that the decrease in the secondary electrons’ average emission gain was a function of the pulse width and related this to the trapping of electrons by the effective NEA surface. The findings from the model agree well with our experimental measurements. As an application of the model, the energy spread of secondary electrons inside the diamond was estimated from the measured emission.

Slides THAP01 [2.034 MB]

Paper	Title	Page
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.

TUPPR084	HOM Damping and Multipacting Analysis of the Quarter-wave Crab Cavity	2020
	Q. Wu, S.A. Belomestnykh, I. Ben-Zvi BNL, Upton, Long Island, New York, USA R. Calaga CERN, Geneva, Switzerland
	The Quarter-Wave Crab Cavity design has been analyzed further to accommodate LHC requirements. The goal for the design is to provide strong deflecting voltage to the proton bunches at the IP, while keeping the effective length as short as possible. We will evaluate the Higher Order Mode damping with two magnetic coupling dampers of 90 degrees apart. In this paper, we also show possible multipacting locations which are simulated by 3D code.

WEPPC027	A Quarter Wave Design for Crab Crossing in the LHC	2260
	R. Calaga CERN, Geneva, Switzerland S.A. Belomestnykh, I. Ben-Zvi, Q. Wu BNL, Upton, Long Island, New York, USA
	Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP). The aperture constraints of the LHC interaction region and the alternating crossing schemes at two collision points calls for a superconducting deflecting cavity with very compact dimensions at low frequencies for the purpose of crab crossing. A new concept of using a superconducting 1/4-wave design, ideally suited to address the LHC constraints at 400 MHz, is proposed. The optimized RF cavity design and associated advantages of using a 1/4 wave resonator are presented. Aspects related to higher order mode damping, multipacting and frequency tuning are also addressed.

WEPPC110	3D Simulations of Multipacting in the 56 MHz SRF Cavity	2477
	Q. Wu, S.A. Belomestnykh BNL, Upton, Long Island, New York, USA L. Ge, C. Ko, Z. Li, C.-K. Ng, L. Xiao SLAC, Menlo Park, California, USA
	Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The 56 MHz SRF Quarter-Wave Resonator (QWR) is designed for RHIC as a storage cavity to improve the collider performance. 2D multipacting simulation has been done for the cavity alone. Ripples were added to the outer body of the cavity for multipacting suppression based on the simulation findings. During operation, there will be four higher order mode (HOM) couplers and a fundamental power coupler (FPC) inserted through the end ports of the cavity and a fundamental mode damper (FD) inserted through a special port on the outer body. All of these components will be exposed to high RF fields. In this presentation we compare 2D and 3D codes simulation results for multipacting in the cavity. We also report 3D simulation results for multipacting simulation at the couplers.

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.

WEPPC109	Superconducting RF Systems for eRHIC	2474
	S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, H. Hahn, D. Kayran, G.J. Mahler, G.T. McIntyre, C. Pai, I. Pinayev, V. Ptitsyn, J. Skaritka, R. Than, J.E. Tuozzolo, Q. Wu, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, V. Litvinenko, T. Xin 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. Future electron-hadron collider eRHIC will consist of a six-pass 30-GeV electron ERL and one of RHIC storage rings operating with energy up to 250 GeV. The collider design extensively utilizes superconducting RF (SRF) technology in both electron and hadron parts. This paper describes various SRF systems, their requirements and parameters.

THAP01	Secondary-electron Emission from Hydrogen-terminated Diamond	3223
	E. Wang, I. Ben-Zvi, T. Rao, Q. Wu BNL, Upton, Long Island, New York, USA D.A. Dimitrov Tech-X, Boulder, Colorado, USA T. Xin Stony Brook University, Stony Brook, USA
	Diamond amplifiers demonstrably are an electron source with the potential to support high-brightness, high-average-current emission into a vacuum. We recently developed a reliable hydrogenation procedure for the diamond amplifier. The systematic study of hydrogenation resulted in the reproducible fabrication of high gain diamond amplifier. Furthermore, we measured the emission probability of diamond amplifier as a function of the external field and modeled the process with resulting changes in the vacuum level due to the Schottky effect. We demonstrated that the decrease in the secondary electrons’ average emission gain was a function of the pulse width and related this to the trapping of electrons by the effective NEA surface. The findings from the model agree well with our experimental measurements. As an application of the model, the energy spread of secondary electrons inside the diamond was estimated from the measured emission.
	Slides THAP01 [2.034 MB]