IPAC2012 - List of Authors (Xu, W.)

Paper	Title	Page
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.

WEPPC112	Development of a Fundamental Power Coupler for High-Current Superconducting RF Cavity	2483
	P. Jain Stony Brook University, Stony Brook, USA S.A. Belomestnykh, I. Ben-Zvi, W. Xu BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE and by the DOE grant DE-SC0002496 to Stony Brook University. Brookhaven National Laboratory has undertaken a project to design a five-cell superconducting 703.75 MHz RF cavity for the Energy Recovery Linac (ERL) and the planned RHIC electron cooler. The earlier developed cavity, viz., the BNL1 is fed by a klystron using a co-axial Fundamental Power Coupler (FPC), which delivers 50 kW of cw RF power to the cavity. During the cavity operation, it has been observed that a 5 K cooling line intercept in the FPC introduces undesirable microphonics. A modification in the existing FPC has been planned to determine the feasibility of getting rid of the 5 K cooling line. The modified coupler will be incorporated in the newly designed, under construction BNL3 cavity. In order to accommodate this modification, peak microphonics of 12 Hz and 20 kW of cw RF power will be considered. This paper describes the design of the new FPC starting from the analysis of thermal profile along its length from first principles.

WEPPC113	Progress on the High-Current 704 MHz Superconducting RF Cavity at BNL	2486
	W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, P. Jain BNL, Upton, Long Island, New York, USA C.M. Astefanous, M.D. Cole, J.P. Deacutis, D. Holmes AES, Medford, NY, USA
	Funding: This work was supported by Sotny Brook under contract No. DE-SC0002496 and Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups for the copper prototype, and presents comparison of the experimental results with computer simulations. The progress with the niobium cavity fabrication will also be described.

WEPPC114	Design, Simulation and Conditioning of the Fundamental Power Couplers for BNL SRF Gun	2489
	W. Xu, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, S. Deonarine, D.M. Gassner, J.P. Jamilkowski, P. Kankiya, D. Kayran, N. Laloudakis, L. Masi, G.T. McIntyre, D. Pate, D. Phillips, T. Seda, A.N. Steszyn, T.N. Tallerico, R.J. Todd, D. Weiss, A. Zaltsman BNL, Upton, Long Island, New York, USA M.D. Cole, G.J. Whitbeck AES, Medford, NY, USA
	Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The 704 MHz SRF gun for the BNL Energy Recovery Linac (ERL) prototype uses two fundamental power couplers (FPCs) to deliver up to total 1 MW of CW RF power into the half-cell cavity. To prepare the couplers for high-power RF service and process multipacting, the FPCs should be conditioned prior to installation into the gun cryomodule. A room-temperature test stand was configured for conditioning FPCs in full reflection regime with varied phase of the reflecting wave. The FPCs have been conditioned up to 250 kW in pulse mode and 125 kW in CW mode. The multipacting simulations were carried out with Track3P code developed at SLAC. The simulations matched the experimental results very well. This paper presents the FPC RF and thermal design, multipacting simulations and conditioning of the BNL gun FPCs.

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.

MOPPR032	Electron Beam Diagnostics based on Transverse Feedback System at Duke Storage Ring	849
	W. Xu, D.H. He USTC/NSRL, Hefei, Anhui, People's Republic of China J.Y. Li, W. Wu, Y.K. Wu FEL/Duke University, Durham, North Carolina, USA
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. To combat electron beam instabilities, a field programmable gate array (FPGA) based bunch-by-bunch transverse feedback (TFB) has been developed for the Duke storage ring. While it is capable of suppressing transverse beam instabilities for multi-bunch operation, the TFB system has not been needed for typical operation of the Duke storage ring FEL. To explore the great potential of this system, we have focused on the development of TFB based beam diagnostics. A TFB based tune measurement system has been developed using two methods: the tune scan method and tune monitoring method. With the tune monitoring method, a much faster method of the two, we have studied the tune stability of the electron beam in the Duke storage ring. This tune measurement system also allows us to conduct chromaticity measurements more quickly, compared with the existing chromaticity measurement system using a network analyzer. Finally, the TFB based tune system has been used to calibrate the tune knob and chromaticity knob for the Duke storage ring.

Paper

Title

Page

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.

WEPPC112

Development of a Fundamental Power Coupler for High-Current Superconducting RF Cavity

2483

P. Jain
Stony Brook University, Stony Brook, USA
S.A. Belomestnykh, I. Ben-Zvi, W. Xu
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE and by the DOE grant DE-SC0002496 to Stony Brook University.
Brookhaven National Laboratory has undertaken a project to design a five-cell superconducting 703.75 MHz RF cavity for the Energy Recovery Linac (ERL) and the planned RHIC electron cooler. The earlier developed cavity, viz., the BNL1 is fed by a klystron using a co-axial Fundamental Power Coupler (FPC), which delivers 50 kW of cw RF power to the cavity. During the cavity operation, it has been observed that a 5 K cooling line intercept in the FPC introduces undesirable microphonics. A modification in the existing FPC has been planned to determine the feasibility of getting rid of the 5 K cooling line. The modified coupler will be incorporated in the newly designed, under construction BNL3 cavity. In order to accommodate this modification, peak microphonics of 12 Hz and 20 kW of cw RF power will be considered. This paper describes the design of the new FPC starting from the analysis of thermal profile along its length from first principles.

WEPPC113

Progress on the High-Current 704 MHz Superconducting RF Cavity at BNL

2486

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, P. Jain
BNL, Upton, Long Island, New York, USA
C.M. Astefanous, M.D. Cole, J.P. Deacutis, D. Holmes
AES, Medford, NY, USA

Funding: This work was supported by Sotny Brook under contract No. DE-SC0002496 and Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups for the copper prototype, and presents comparison of the experimental results with computer simulations. The progress with the niobium cavity fabrication will also be described.

WEPPC114

Design, Simulation and Conditioning of the Fundamental Power Couplers for BNL SRF Gun

2489

W. Xu, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, S. Deonarine, D.M. Gassner, J.P. Jamilkowski, P. Kankiya, D. Kayran, N. Laloudakis, L. Masi, G.T. McIntyre, D. Pate, D. Phillips, T. Seda, A.N. Steszyn, T.N. Tallerico, R.J. Todd, D. Weiss, A. Zaltsman
BNL, Upton, Long Island, New York, USA
M.D. Cole, G.J. Whitbeck
AES, Medford, NY, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 704 MHz SRF gun for the BNL Energy Recovery Linac (ERL) prototype uses two fundamental power couplers (FPCs) to deliver up to total 1 MW of CW RF power into the half-cell cavity. To prepare the couplers for high-power RF service and process multipacting, the FPCs should be conditioned prior to installation into the gun cryomodule. A room-temperature test stand was configured for conditioning FPCs in full reflection regime with varied phase of the reflecting wave. The FPCs have been conditioned up to 250 kW in pulse mode and 125 kW in CW mode. The multipacting simulations were carried out with Track3P code developed at SLAC. The simulations matched the experimental results very well. This paper presents the FPC RF and thermal design, multipacting simulations and conditioning of the BNL gun FPCs.

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.

MOPPR032

Electron Beam Diagnostics based on Transverse Feedback System at Duke Storage Ring

849

W. Xu, D.H. He
USTC/NSRL, Hefei, Anhui, People's Republic of China
J.Y. Li, W. Wu, Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
To combat electron beam instabilities, a field programmable gate array (FPGA) based bunch-by-bunch transverse feedback (TFB) has been developed for the Duke storage ring. While it is capable of suppressing transverse beam instabilities for multi-bunch operation, the TFB system has not been needed for typical operation of the Duke storage ring FEL. To explore the great potential of this system, we have focused on the development of TFB based beam diagnostics. A TFB based tune measurement system has been developed using two methods: the tune scan method and tune monitoring method. With the tune monitoring method, a much faster method of the two, we have studied the tune stability of the electron beam in the Duke storage ring. This tune measurement system also allows us to conduct chromaticity measurements more quickly, compared with the existing chromaticity measurement system using a network analyzer. Finally, the TFB based tune system has been used to calibrate the tune knob and chromaticity knob for the Duke storage ring.