PAC2013 - List of Authors (Ge, G.M.)

Paper	Title	Page
WEPAC09	A Temperature-Mapping System for Multi-Cell SRF Accelerator Cavities	805
	G.M. Ge, G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	A Temperature mapping (T-map) system for Superconducting Radio Frequency (SRF) cavities consists of a thermometer array positioned precisely on an exterior cavity wall, capable of detecting small increases in temperature; therefore it is a powerful tool for research on the quality factor (Q0) of SRF cavities. A new multi-cell T-mapping system is has been developed at Cornell University. The system has nearly two thousand thermometers to cover 7-cell SRF cavities for Cornell’s ERL project. A new multiplexing scheme was adopted to reduce number of wires. A 1mK resolution of the temperature increase ΔT is achieved. A 9-cell cavity of TESLA geometry was tested with the T-map system. By converting ΔT to power loss and quality factor, it has been found that for this cavity, most surface losses were generated by the first cell when the accelerating gradient is increased above 15MV/m. Effective and intuitive ways of displaying surface properties of the cavity interior, e.g. the residual resistivity, will be shown.

WEPAC10	Investigation of the Surface Resistivity of SRF Cavities via theHEAT and SRIMP Program as well as the Multi-cell T-Map System	808
	G.M. Ge, G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	A high-sensitive temperature mapping system for multi-cell SRF cavities has been constructed at Cornell University. The resolution of the system is 1mK. Hence it’s able to detect small temperature increases when cavities reach at low accelerating gradients e.g. 3MV/m. The surface resistivity of superconductor under radio-frequency electromagnetic field can be calculated from the temperature increases. In this contribution, the surface resistance map of multi-cell SRF cavities is shown. The temperature mapping result is possible to establish a relationship between the surface resistivity and the magnetic field as well. Unlike the RF method which is average value of the surface resistance, the T-map results give local surface resistivity versus magnetic field. BCS theory assumes the surface resistivity is independent to the magnetic field. The T-map results, however, suggest that the surface resistance at high-loss region is field dependent and caused Q-slope.

WEPAC11	Cornell's Main Linac Cryo-module Prototype	811
	R.G. Eichhorn, G.M. Ge, Y. He, G.H. Hoffstaetter, M. Liepe, T. O'Connel, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Supported by NSF award DMR-0807731 In preparation to built an energy-recovery linac (ERL) based synchrotron-light facility at Cornell University which can provide greatly improved X-ray beams due to the high electron-beam quality that is available from a linac, a phase 1 R&D program was launched, adressing critical challenges in the design. One of them being a full linac cryo-module, housing 6 superconducting cavities (operated at 1.8 K in cw mode), 7 HOM absorbers and 1 magnet/ BPM section. The final design will be presented and a report on the fabrication status that started in late 2012 will be given

THPMA07	Cryomodule Performance of the Main Linac Prototype Cavity for Cornell's Energy Recovery Linac	1367
	N.R.A. Valles, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, S. Posen, P. Quigley, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF Grants: NSF DMR-0807731 and NSF PHY-1002467 Energy Recovery Linacs (ERLs) require strong damping of higher-order modes in main linac cavities to avoid beam loss from beam break-up effects. In addition, the cavities need to have very high intrinsic quality factors to minimize the size of cryogenic plants in CW cavity operation. We present world record results for a fully equipped multicell cavity in a cryomodule, reaching intrinsic quality factors at operating accelerating field of Q₀(E =16.2 MV/m, 1.8~K) > 6.0\ee10 and Q₀(E =16.2 MV/m, 1.6~K) = 1.0\ee{11}, corresponding to a residual surface resistance of 1.1~nΩ.

Paper

Title

Page

A Temperature-Mapping System for Multi-Cell SRF Accelerator Cavities

805

G.M. Ge, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

A Temperature mapping (T-map) system for Superconducting Radio Frequency (SRF) cavities consists of a thermometer array positioned precisely on an exterior cavity wall, capable of detecting small increases in temperature; therefore it is a powerful tool for research on the quality factor (Q0) of SRF cavities. A new multi-cell T-mapping system is has been developed at Cornell University. The system has nearly two thousand thermometers to cover 7-cell SRF cavities for Cornell’s ERL project. A new multiplexing scheme was adopted to reduce number of wires. A 1mK resolution of the temperature increase ΔT is achieved. A 9-cell cavity of TESLA geometry was tested with the T-map system. By converting ΔT to power loss and quality factor, it has been found that for this cavity, most surface losses were generated by the first cell when the accelerating gradient is increased above 15MV/m. Effective and intuitive ways of displaying surface properties of the cavity interior, e.g. the residual resistivity, will be shown.

WEPAC10

Investigation of the Surface Resistivity of SRF Cavities via theHEAT and SRIMP Program as well as the Multi-cell T-Map System

808

G.M. Ge, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

A high-sensitive temperature mapping system for multi-cell SRF cavities has been constructed at Cornell University. The resolution of the system is 1mK. Hence it’s able to detect small temperature increases when cavities reach at low accelerating gradients e.g. 3MV/m. The surface resistivity of superconductor under radio-frequency electromagnetic field can be calculated from the temperature increases. In this contribution, the surface resistance map of multi-cell SRF cavities is shown. The temperature mapping result is possible to establish a relationship between the surface resistivity and the magnetic field as well. Unlike the RF method which is average value of the surface resistance, the T-map results give local surface resistivity versus magnetic field. BCS theory assumes the surface resistivity is independent to the magnetic field. The T-map results, however, suggest that the surface resistance at high-loss region is field dependent and caused Q-slope.

WEPAC11

Cornell's Main Linac Cryo-module Prototype

811

R.G. Eichhorn, G.M. Ge, Y. He, G.H. Hoffstaetter, M. Liepe, T. O'Connel, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Supported by NSF award DMR-0807731
In preparation to built an energy-recovery linac (ERL) based synchrotron-light facility at Cornell University which can provide greatly improved X-ray beams due to the high electron-beam quality that is available from a linac, a phase 1 R&D program was launched, adressing critical challenges in the design. One of them being a full linac cryo-module, housing 6 superconducting cavities (operated at 1.8 K in cw mode), 7 HOM absorbers and 1 magnet/ BPM section. The final design will be presented and a report on the fabrication status that started in late 2012 will be given

THPMA07

Cryomodule Performance of the Main Linac Prototype Cavity for Cornell's Energy Recovery Linac

1367

N.R.A. Valles, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, S. Posen, P. Quigley, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF Grants: NSF DMR-0807731 and NSF PHY-1002467
Energy Recovery Linacs (ERLs) require strong damping of higher-order modes in main linac cavities to avoid beam loss from beam break-up effects. In addition, the cavities need to have very high intrinsic quality factors to minimize the size of cryogenic plants in CW cavity operation. We present world record results for a fully equipped multicell cavity in a cryomodule, reaching intrinsic quality factors at operating accelerating field of Q₀(E =16.2 MV/m, 1.8~K) > 6.0\ee10 and Q₀(E =16.2 MV/m, 1.6~K) = 1.0\ee{11}, corresponding to a residual surface resistance of 1.1~nΩ.