LINAC2014 - List of Authors (Xu, W.)

Paper	Title	Page
MOPP002	Design of a Superconducting Quarter-Wave Resonator for eRHIC	49
	S.V. Kutsaev, Z.A. Conway, M.P. Kelly, B. Mustapha, P.N. Ostroumov ANL, Argonne, USA S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA S.A. Belomestnykh, I. Ben-Zvi, Q. Wu, W. Xu BNL, Upton, Long Island, New York, USA B. P. Xiao SBU, Stony Brook, New York, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 The electron-ion collider project (eRHIC) at Brookhaven National Laboratory requires a 50 mA 12 MeV electron injector linac for eRHIC main linac and an SRF electron gun for a Coherent electron Cooling (CeC) linac. The necessity to deal with long electron bunches required for both the eRHIC injector and the coherent electron cooler sets the frequency requirement of 84.5 MHz. Quarter wave resonator is a perfect choice for this frequency because of its dimensions, RF parameters and good experience with manufacturing and using them at ANL. Here we present the design and optimization of an 84.5 MHz 2.5 MV superconducting quarter-wave cavity suitable for both machines. One such QWR will be used as a bunching cavity in the injector linac, the other one as the photoemission electron source for the CeC linac. In addition to the optimization of the QWR electromagnetic design we will discuss the tuner design, approaches to cavity fabrication and processing.

MOPP012	Beam Commissioning of the SRF 704 MHz Photoemission Gun	70
	W. Xu, S.A. Belomestnykh, I. Ben-Zvi, D.M. Gassner, H. Hahn, J.P. Jamilkowski, P. Kankiya, D. Kayran, N. Laloudakis, R.F. Lambiase, G.T. McIntyre, D. Phillips, V. Ptitsyn, K.S. Smith, R. Than, D. Weiss, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, V. Ptitsyn Stony Brook University, Stony Brook, USA D. Holmes AES, Medford, New York, USA
	Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. A 704 MHz superconducting RF photoemission electron gun for the R&D ERL project is under comissioning at BNL. Without a cathode insert, the SRF gun achieved its design goal: an accelerating voltage of 2 MV in CW mode. During commissioning with a copper cathode insert it reached 1.9 MV with 18% duty factor, which is limited by mulitpacting in a choke-joint cathode stalk. A new cathode stalk has been designed to eliminate multipacting in the choke-joint. This paper presents recent commissioning results, including cavity commissioning without the cathode stalk insert, first beam commissioning of the SRF gun in pulsed regime, and the design of a multipacting-free cathode stalk.

MOPP013	Vertical Test Results of 704 MHz BNL3 SRF Cavities	73
	W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, R. Porgueddu, R. Than, D. Weiss BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA C.H. Boulware, T.L. Grimm Niowave, Inc., Lansing, Michigan, USA M.D. Cole, D. Holmes, T. Schultheiss AES, Medford, New York, USA
	Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE, and Award No. DE-SC0002496 to Stony Brook University with the U.S. DOE. An electron-ion collider (eRHIC) proposed at BNL requires superconducting RF cavities able to support high average beam current. A 5-cell niobium SRF cavity, called BNL3, was designed for a conventional lattice eRHIC design. To avoid inducing emittance degradation and beam-break-up (BBU), the BNL3 cavity was optimized to damp all dangerous higher-order-modes (HOMs) by employing a large beam pipes and coaxial antenna-type couplers. Additionally, the cavity was designed for an acceptable cryogenic load and peak surface RF fields. Two BNL3 cavities have been fabricated and tested at a vertical test facility at BNL. This paper addresses development of the SRF cavities for eRHIC, including SRF cavity design, fabrication and test results.

Paper

Title

Page

Design of a Superconducting Quarter-Wave Resonator for eRHIC

49

S.V. Kutsaev, Z.A. Conway, M.P. Kelly, B. Mustapha, P.N. Ostroumov
ANL, Argonne, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
S.A. Belomestnykh, I. Ben-Zvi, Q. Wu, W. Xu
BNL, Upton, Long Island, New York, USA
B. P. Xiao
SBU, Stony Brook, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357
The electron-ion collider project (eRHIC) at Brookhaven National Laboratory requires a 50 mA 12 MeV electron injector linac for eRHIC main linac and an SRF electron gun for a Coherent electron Cooling (CeC) linac. The necessity to deal with long electron bunches required for both the eRHIC injector and the coherent electron cooler sets the frequency requirement of 84.5 MHz. Quarter wave resonator is a perfect choice for this frequency because of its dimensions, RF parameters and good experience with manufacturing and using them at ANL. Here we present the design and optimization of an 84.5 MHz 2.5 MV superconducting quarter-wave cavity suitable for both machines. One such QWR will be used as a bunching cavity in the injector linac, the other one as the photoemission electron source for the CeC linac. In addition to the optimization of the QWR electromagnetic design we will discuss the tuner design, approaches to cavity fabrication and processing.

MOPP012

Beam Commissioning of the SRF 704 MHz Photoemission Gun

70

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, D.M. Gassner, H. Hahn, J.P. Jamilkowski, P. Kankiya, D. Kayran, N. Laloudakis, R.F. Lambiase, G.T. McIntyre, D. Phillips, V. Ptitsyn, K.S. Smith, R. Than, D. Weiss, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Ptitsyn
Stony Brook University, Stony Brook, USA
D. Holmes
AES, Medford, New York, USA

Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
A 704 MHz superconducting RF photoemission electron gun for the R&D ERL project is under comissioning at BNL. Without a cathode insert, the SRF gun achieved its design goal: an accelerating voltage of 2 MV in CW mode. During commissioning with a copper cathode insert it reached 1.9 MV with 18% duty factor, which is limited by mulitpacting in a choke-joint cathode stalk. A new cathode stalk has been designed to eliminate multipacting in the choke-joint. This paper presents recent commissioning results, including cavity commissioning without the cathode stalk insert, first beam commissioning of the SRF gun in pulsed regime, and the design of a multipacting-free cathode stalk.

MOPP013

Vertical Test Results of 704 MHz BNL3 SRF Cavities

73

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, R. Porgueddu, R. Than, D. Weiss
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
M.D. Cole, D. Holmes, T. Schultheiss
AES, Medford, New York, USA

Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE, and Award No. DE-SC0002496 to Stony Brook University with the U.S. DOE.
An electron-ion collider (eRHIC) proposed at BNL requires superconducting RF cavities able to support high average beam current. A 5-cell niobium SRF cavity, called BNL3, was designed for a conventional lattice eRHIC design. To avoid inducing emittance degradation and beam-break-up (BBU), the BNL3 cavity was optimized to damp all dangerous higher-order-modes (HOMs) by employing a large beam pipes and coaxial antenna-type couplers. Additionally, the cavity was designed for an acceptable cryogenic load and peak surface RF fields. Two BNL3 cavities have been fabricated and tested at a vertical test facility at BNL. This paper addresses development of the SRF cavities for eRHIC, including SRF cavity design, fabrication and test results.