SRF2013 - List of Authors (Ge, G.M.)

Paper

Title

Page

Record Quality Factor Performance of the Prototype Cornell ERL Main Linac Cavity in the Horizontal Test Cryomodule

300

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'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Supported by NSF grant DMR-0807731
Future SRF linac driven accelerators operated in CW mode will require very efficient SRF cavities with high intrinsic quality factors Q at medium accelerating fields. Cornell has recently ﬁnished testing the fully equipped 1.3 GHz, 7-cell main linac cavity for the Cornell Energy Recovery Linac in a horizontal test cryomodule (HTC). Measurements characterizing the fundamental mode’s quality factor have been completed, showing record Q performance. In this paper, we present detailed quality factor vs gradient results for three HTC assembly stages. We show that the performance of an SRF cavity can be maintained when installed into a cryomodule, and that thermal cycling reduces residual surface resistance. We present world record results for a fully equipped multicell cavity in a cryomodule, reaching intrinsic quality factors at operating accelerating field of Q(E =16.2 MV/m, 1.8K) > 6·10¹⁰ and Q(E =16.2 MV/m, 1.6K) > 1.0·10¹¹, corresponding to a very low residual surface resistance of 1.1 nOhm.

TUP048

Preparations and VT Results of ERL7-cell at Cornell

521

F. Furuta, B. Bullock, R.G. Eichhorn, B. Elmore, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

We have fabricated 7 ERL 7-cell cavities for Cornell ERL project. 4 nu-stiffened and 3-stiffened cavities have been fabricated in house so far. Specification values of our 7-cell is 16.2MV/m with Qo of 2.0·10¹⁰ at 1.8K. In this report, we will describe our surface treatments recipe which is based on BCP and the results of vertical tests of these 7-cell cavities.

TUP059

TM-Furnace Qualification at Cornell

561

F. Furuta, B. Bullock, R.G. Eichhorn, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell's SRF group had new vacuum furnace for hydrogen degassing of SRF Nb cavity. Systematic study and testing have been done to qualify this new furnace. We will report the results of those qualification tests include cavity bake and vertical testing.

TUP105

Investigation of the Surface Resistivity of SRF Cavities via the Heat and Srimp Program as Well as the Multi-Cell T-Map System

724

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

THIOB02

High Q Cavities for the Cornell ERL Main Linac

844

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

While SRF research for linear colliders was focused on achieving high gradients, Cornell’s proposal for an energy recovery linac (ERL) demanded for low cw losses. Starting several years ago, a high-Q R&D phase was launched that led to remarkable results recently: A fully dressed cavity (7 cells, 1.3 GHz) with side-mounted input coupler and beamline HOM absorbers achieved a Q of 3.5·10¹⁰ ((16 MV/m, 1.8 K). This talk will review the staged approach we have chosen in testing a single cavity in a horizontal short cryomodule (HTC), report results on each step and conclude on our findings about preserving high Q from vertical testing. We also discuss the production of six additional cavities as we progress toward constructing a full 6-cavity cryomodule as a prototype for Cornell’s main linac module

Slides THIOB02 [8.378 MB]

THP008

High Voltage Cavity R&D at Cornell, RE and ICHIRO

F. Furuta, B. Elmore, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

We have been investigated 1.3GHz high gradient SRF Nb cavity with shape of low Hpk/Eacc, such as re-entrant(RE) and KEK low-loss (ICHIRO) shapes. We have single-/multi-cell RE cavities and ICHIRO single-cell cavities at Cornell. We have processed those cavities based on buffered chemical-polishing(BCP), vertical electro-polishing(VEP), and centrifugal barrel-polsihing(CBP). In this paper, we will report the details of processes and the results of vertical tests of these cavities.

Paper	Title	Page
MOP071	Record Quality Factor Performance of the Prototype Cornell ERL Main Linac Cavity in the Horizontal Test Cryomodule	300
	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'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Supported by NSF grant DMR-0807731 Future SRF linac driven accelerators operated in CW mode will require very efficient SRF cavities with high intrinsic quality factors Q at medium accelerating fields. Cornell has recently ﬁnished testing the fully equipped 1.3 GHz, 7-cell main linac cavity for the Cornell Energy Recovery Linac in a horizontal test cryomodule (HTC). Measurements characterizing the fundamental mode’s quality factor have been completed, showing record Q performance. In this paper, we present detailed quality factor vs gradient results for three HTC assembly stages. We show that the performance of an SRF cavity can be maintained when installed into a cryomodule, and that thermal cycling reduces residual surface resistance. We present world record results for a fully equipped multicell cavity in a cryomodule, reaching intrinsic quality factors at operating accelerating field of Q(E =16.2 MV/m, 1.8K) > 6·10¹⁰ and Q(E =16.2 MV/m, 1.6K) > 1.0·10¹¹, corresponding to a very low residual surface resistance of 1.1 nOhm.

TUP048	Preparations and VT Results of ERL7-cell at Cornell	521
	F. Furuta, B. Bullock, R.G. Eichhorn, B. Elmore, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	We have fabricated 7 ERL 7-cell cavities for Cornell ERL project. 4 nu-stiffened and 3-stiffened cavities have been fabricated in house so far. Specification values of our 7-cell is 16.2MV/m with Qo of 2.0·10¹⁰ at 1.8K. In this report, we will describe our surface treatments recipe which is based on BCP and the results of vertical tests of these 7-cell cavities.

TUP059	TM-Furnace Qualification at Cornell	561
	F. Furuta, B. Bullock, R.G. Eichhorn, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cornell's SRF group had new vacuum furnace for hydrogen degassing of SRF Nb cavity. Systematic study and testing have been done to qualify this new furnace. We will report the results of those qualification tests include cavity bake and vertical testing.

TUP105	Investigation of the Surface Resistivity of SRF Cavities via the Heat and Srimp Program as Well as the Multi-Cell T-Map System	724
	G.M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, H. Padamsee Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA F. Furuta Cornell University, 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.

THIOB02	High Q Cavities for the Cornell ERL Main Linac	844
	R.G. Eichhorn, B. Bullock, B. Clasby, B. Elmore, F. Furuta, A. Ganshin, G.M. Ge, D. Gonnella, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V.D. Shemelin, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	While SRF research for linear colliders was focused on achieving high gradients, Cornell’s proposal for an energy recovery linac (ERL) demanded for low cw losses. Starting several years ago, a high-Q R&D phase was launched that led to remarkable results recently: A fully dressed cavity (7 cells, 1.3 GHz) with side-mounted input coupler and beamline HOM absorbers achieved a Q of 3.5·10¹⁰ ((16 MV/m, 1.8 K). This talk will review the staged approach we have chosen in testing a single cavity in a horizontal short cryomodule (HTC), report results on each step and conclude on our findings about preserving high Q from vertical testing. We also discuss the production of six additional cavities as we progress toward constructing a full 6-cavity cryomodule as a prototype for Cornell’s main linac module
	Slides THIOB02 [8.378 MB]

THP008	High Voltage Cavity R&D at Cornell, RE and ICHIRO
	F. Furuta, B. Elmore, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	We have been investigated 1.3GHz high gradient SRF Nb cavity with shape of low Hpk/Eacc, such as re-entrant(RE) and KEK low-loss (ICHIRO) shapes. We have single-/multi-cell RE cavities and ICHIRO single-cell cavities at Cornell. We have processed those cavities based on buffered chemical-polishing(BCP), vertical electro-polishing(VEP), and centrifugal barrel-polsihing(CBP). In this paper, we will report the details of processes and the results of vertical tests of these cavities.