SRF2013 - List of Authors (Posen, S.)

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.

TUP031

Muon Spin Rotation Studies of Bulk Electropolished Cavity Cutouts and Thin Films of Alternative Materials

A. Grassellino, A. Romanenko, D.A. Sergatskov
Fermilab, Batavia, USA
T. Buck, R.E. Laxdal
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
M. Liepe, S. Posen
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Y. Trenikhina
IIT, Chicago, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
In the previous studies [*] magnetic flux penetration into fine and large grain BCP cavity cutouts was investigated using the muon spin rotation (muSR) technique. The technique is based on implanting muons, which serve as sensitive magnetic probes inside the material. Here we report muSR studies on fine grain EP cavity cutouts, both before and after 120C baking, and on the films of new materials.
[*] A. Grassellino et al, Phys. Rev. ST Accel. Beams 16, 062002 (2013)

TUP058

Recent Findings on Nitrogen Treated Niobium

558

R.G. Eichhorn, A. Ganshin, A. Holmes, J.J. Kaufman, S.R. Markham, S. Posen, E.N. Smith
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Recent findings on Nitrogen treated Niobiums Based on recent findings at Fermilab, Cornell investigated the role of Nitrogen being present during the cavity hydrogen degassing process. We treated several samples at different temperatures being exposed to nitrogen between 10 minutes and 3 hours at pressures around 15 mbar as well as single cell cavities. This contribution will summarize our findings from surface analysis, Tc measurements and cavity Qs, addressing the question, if such a process can form Niobium-Nitride.

TUP087

RF Test Results of the first Nb3Sn Cavities Coated at Cornell

666

S. Posen, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

As an alternative material to niobium for SRF cavities in particle accelerators, Nb3Sn presents two significant advantages. With a Tc of 18 K, it has a very small surface resistance at a given temperature, leading to a significant reduction in cryogenic costs; and with a predicted Hsh of nearly 400 mT, it has the potential to produce cavities with higher gradients and therefore shorter high energy linacs. Recently, two 1.3 GHz cavities have been fabricated and coated with Nb3Sn at Cornell. Tests of these first cavities have produced encouraging results, including a very high Tc and some very high-performing surface regions. These cavity results as well as new results of samples studied using TEM will be presented.

WEIOA04

Nb3Sn for SRF Application

773

M. Liepe, S. Posen
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The superconductor Nb3Sn is a promising alternative to standard niobium for SRF applications for two reasons: Its larger superconducting energy gap results in significantly lower BCS surface resistance at typical SRF operating temperatures. Additionally, theoretical predictions suggest that the maximum operating field of Nb3Sn cavities could be twice that of niobium cavities. Early work on a small number of Nb3Sn coated cavities indeed showed 2K to 4.2K quality factors well above what is achievable with niobium, though at accelerating fields below ~10 MV/m only. After many years of worldwide inactivity, Cornell has taken the lead and initiated a new R&D program on Nb3Sn to explore its full potential for SRF applications. New facilities for coating cavities with Nb3Sn have been set up at Cornell, and 1.3 GHz single cell cavities have been coated and tested. This talk presents the Cornell Nb3Sn program, discusses first promising results obtained, and also gives an overview of other Nb3Sn SRF work worldwide.

Slides WEIOA04 [3.854 MB]

WEIOC04

Theoretical Field Limits for Multi-Layer Superconductors

794

S. Posen, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
G. Catelani
Forschungszentrum Jülich, Peter Gruenberg Institut (PGI-2), Jülich, Germany
J.P. Sethna
Cornell University, Ithaca, New York, USA
M.K. Transtrum
M.D.A.C.C., Houston, Texas, USA

With modern cavity preparation techniques, niobium SRF cavities reach surface magnetic fields very close to the fundamental limit of the superheating field of the material, and researchers are looking to alternative superconductors to sustain even higher fields. However, these materials may have an increased vulnerability to flux penetration at defects, even small ones, as a result of their short coherence lengths. A. Gurevich has proposed [1] a method of mitigating this vulnerability: coating a bulk superconducting cavity with a series of very thin insulating and superconducting films. In this work, we present a thorough mathematical description of the SIS thin films proposed by Gurevich in the language of the SRF community, to help researchers to optimize cavities made from alternative superconductors.
[1] A. Gurevich, Appl. Phys. Lett. 88, 012511 (2006)

Slides WEIOC04 [4.116 MB]

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]

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.

TUP031	Muon Spin Rotation Studies of Bulk Electropolished Cavity Cutouts and Thin Films of Alternative Materials
	A. Grassellino, A. Romanenko, D.A. Sergatskov Fermilab, Batavia, USA T. Buck, R.E. Laxdal TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada M. Liepe, S. Posen Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA Y. Trenikhina IIT, Chicago, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. In the previous studies [] magnetic flux penetration into fine and large grain BCP cavity cutouts was investigated using the muon spin rotation (muSR) technique. The technique is based on implanting muons, which serve as sensitive magnetic probes inside the material. Here we report muSR studies on fine grain EP cavity cutouts, both before and after 120C baking, and on the films of new materials. [] A. Grassellino et al, Phys. Rev. ST Accel. Beams 16, 062002 (2013)

TUP058	Recent Findings on Nitrogen Treated Niobium	558
	R.G. Eichhorn, A. Ganshin, A. Holmes, J.J. Kaufman, S.R. Markham, S. Posen, E.N. Smith Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Recent findings on Nitrogen treated Niobiums Based on recent findings at Fermilab, Cornell investigated the role of Nitrogen being present during the cavity hydrogen degassing process. We treated several samples at different temperatures being exposed to nitrogen between 10 minutes and 3 hours at pressures around 15 mbar as well as single cell cavities. This contribution will summarize our findings from surface analysis, Tc measurements and cavity Qs, addressing the question, if such a process can form Niobium-Nitride.

TUP087	RF Test Results of the first Nb3Sn Cavities Coated at Cornell	666
	S. Posen, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	As an alternative material to niobium for SRF cavities in particle accelerators, Nb3Sn presents two significant advantages. With a Tc of 18 K, it has a very small surface resistance at a given temperature, leading to a significant reduction in cryogenic costs; and with a predicted Hsh of nearly 400 mT, it has the potential to produce cavities with higher gradients and therefore shorter high energy linacs. Recently, two 1.3 GHz cavities have been fabricated and coated with Nb3Sn at Cornell. Tests of these first cavities have produced encouraging results, including a very high Tc and some very high-performing surface regions. These cavity results as well as new results of samples studied using TEM will be presented.

WEIOA04	Nb3Sn for SRF Application	773
	M. Liepe, S. Posen Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The superconductor Nb3Sn is a promising alternative to standard niobium for SRF applications for two reasons: Its larger superconducting energy gap results in significantly lower BCS surface resistance at typical SRF operating temperatures. Additionally, theoretical predictions suggest that the maximum operating field of Nb3Sn cavities could be twice that of niobium cavities. Early work on a small number of Nb3Sn coated cavities indeed showed 2K to 4.2K quality factors well above what is achievable with niobium, though at accelerating fields below ~10 MV/m only. After many years of worldwide inactivity, Cornell has taken the lead and initiated a new R&D program on Nb3Sn to explore its full potential for SRF applications. New facilities for coating cavities with Nb3Sn have been set up at Cornell, and 1.3 GHz single cell cavities have been coated and tested. This talk presents the Cornell Nb3Sn program, discusses first promising results obtained, and also gives an overview of other Nb3Sn SRF work worldwide.
	Slides WEIOA04 [3.854 MB]

WEIOC04	Theoretical Field Limits for Multi-Layer Superconductors	794
	S. Posen, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA G. Catelani Forschungszentrum Jülich, Peter Gruenberg Institut (PGI-2), Jülich, Germany J.P. Sethna Cornell University, Ithaca, New York, USA M.K. Transtrum M.D.A.C.C., Houston, Texas, USA
	With modern cavity preparation techniques, niobium SRF cavities reach surface magnetic fields very close to the fundamental limit of the superheating field of the material, and researchers are looking to alternative superconductors to sustain even higher fields. However, these materials may have an increased vulnerability to flux penetration at defects, even small ones, as a result of their short coherence lengths. A. Gurevich has proposed [1] a method of mitigating this vulnerability: coating a bulk superconducting cavity with a series of very thin insulating and superconducting films. In this work, we present a thorough mathematical description of the SIS thin films proposed by Gurevich in the language of the SRF community, to help researchers to optimize cavities made from alternative superconductors. [1] A. Gurevich, Appl. Phys. Lett. 88, 012511 (2006)
	Slides WEIOC04 [4.116 MB]

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]