IPAC2011 - List of Authors (Liepe, M.)

Paper	Title	Page
MOODA01	Experience with the Cornell ERL Injector SRF Cryomodule during High Beam Current Operation	35
	M. Liepe, D.L. Hartill, G.H. Hoffstaetter, S. Posen, P. Quigley, V. Veshcherevich CLASSE, Ithaca, New York, USA
	Funding: Supported by NSF award DMR-0807731 Cornell University has developed and fabricated a SCRF injector cryomodule for the acceleration of high current, low emittance CW beams. This cryomodule is based on superconducting RF technology with five 2-cell SRF cavities operated in CW mode. Strong Higher-Order-Mode (HOM) damping and high power RF input couplers support accelerating beam currents of tens of mA. The cryomodule is currently under extensive testing in the Cornell ERL injector prototype with CW beam currents exceeding 25 mA. This paper gives an overview of the experience gained during the high beam current operation of the cryomodule, with a focus on the intrinsic cavity quality factors, input coupler performance, and HOM damping.

MOPC108	Cornell SRF New Materials Program*	328
	S. Posen, M. Liepe, Y. Xie CLASSE, Ithaca, New York, USA
	Funding: Work supported by NSF Career award PHY-0841213, DOE award ER41628, and the Alfred P. Sloan Foundation The SRF group at Cornell has recently pioneered an extensive program to investigate alternative materials for superconducting cavities. We have developed facilities to fabricate Nb3Sn, a superconductor which will theoretically be able to reach more than twice the maximum accelerating field of Nb in a cavity under the same operating conditions. In addition, with the critical temperature of Nb3Sn being twice that of Nb, Nb3Sn would allow operation of SRF cavities with a much higher cryogenic efficiency. We have also manufactured two TE cavities that measure the RF properties of small, flat samples, ideal for material fabrication methods in development. This paper presents an overview of the materials research program. First results from tests of Nb3Sn samples are presented.

MOPC109	Suppression of Coupler Kicks in 7-Cell Main Linac Cavities for Cornell's ERL	331
	N.R.A. Valles, M. Liepe, V.D. Shemelin CLASSE, Ithaca, New York, USA
	Funding: Supported by NSF award DMR-0807731 Cornell is developing a 5 GeV Energy Recovery Linac operating at 100 mA with very small emittances (~30 pm at 77 pC bunch charge) in the horizontal and vertical directions. We investigate the effect of the fundamental RF power couplers of the main linac SRF cavities on the beam using the ACE3P software package. The cavities in the ERL main linac will be operated at very high loaded quality factors of up to 6.5·10⁷, corresponding to a full bandwidth of only 20 Hz. Cavity microphonics will detune the cavities by more than one bandwidth during operation, thereby causing a time dependent change of the coupler kick in addition to its fast oscillation at the RF frequency. In order to investigate the dependence of the coupler kick on the cavity frequency, we calculate the coupler kick given to the beam for the case of a detuned RF cavity. We show that a compensation stub geometry located opposite to the input coupler port can be optimized to reduce the overall kick given to the beam and the emittace growth caused by its time dependence.

Paper

Title

Page

Experience with the Cornell ERL Injector SRF Cryomodule during High Beam Current Operation

35

M. Liepe, D.L. Hartill, G.H. Hoffstaetter, S. Posen, P. Quigley, V. Veshcherevich
CLASSE, Ithaca, New York, USA

Funding: Supported by NSF award DMR-0807731
Cornell University has developed and fabricated a SCRF injector cryomodule for the acceleration of high current, low emittance CW beams. This cryomodule is based on superconducting RF technology with five 2-cell SRF cavities operated in CW mode. Strong Higher-Order-Mode (HOM) damping and high power RF input couplers support accelerating beam currents of tens of mA. The cryomodule is currently under extensive testing in the Cornell ERL injector prototype with CW beam currents exceeding 25 mA. This paper gives an overview of the experience gained during the high beam current operation of the cryomodule, with a focus on the intrinsic cavity quality factors, input coupler performance, and HOM damping.

MOPC108

Cornell SRF New Materials Program*

328

S. Posen, M. Liepe, Y. Xie
CLASSE, Ithaca, New York, USA

Funding: Work supported by NSF Career award PHY-0841213, DOE award ER41628, and the Alfred P. Sloan Foundation
The SRF group at Cornell has recently pioneered an extensive program to investigate alternative materials for superconducting cavities. We have developed facilities to fabricate Nb3Sn, a superconductor which will theoretically be able to reach more than twice the maximum accelerating field of Nb in a cavity under the same operating conditions. In addition, with the critical temperature of Nb3Sn being twice that of Nb, Nb3Sn would allow operation of SRF cavities with a much higher cryogenic efficiency. We have also manufactured two TE cavities that measure the RF properties of small, flat samples, ideal for material fabrication methods in development. This paper presents an overview of the materials research program. First results from tests of Nb3Sn samples are presented.

MOPC109

Suppression of Coupler Kicks in 7-Cell Main Linac Cavities for Cornell's ERL

331

N.R.A. Valles, M. Liepe, V.D. Shemelin
CLASSE, Ithaca, New York, USA

Funding: Supported by NSF award DMR-0807731
Cornell is developing a 5 GeV Energy Recovery Linac operating at 100 mA with very small emittances (~30 pm at 77 pC bunch charge) in the horizontal and vertical directions. We investigate the effect of the fundamental RF power couplers of the main linac SRF cavities on the beam using the ACE3P software package. The cavities in the ERL main linac will be operated at very high loaded quality factors of up to 6.5·10⁷, corresponding to a full bandwidth of only 20 Hz. Cavity microphonics will detune the cavities by more than one bandwidth during operation, thereby causing a time dependent change of the coupler kick in addition to its fast oscillation at the RF frequency. In order to investigate the dependence of the coupler kick on the cavity frequency, we calculate the coupler kick given to the beam for the case of a detuned RF cavity. We show that a compensation stub geometry located opposite to the input coupler port can be optimized to reduce the overall kick given to the beam and the emittace growth caused by its time dependence.