SRF2015 - List of Authors (Eichhorn, R.G.)

Paper	Title	Page
MOBA08	Niobium Impurity-Doping Studies at Cornell and CM Cool-Down Dynamic Effect on Q0	55
	M. Liepe, B. Clasby, R.G. Eichhorn, B. Elmore, F. Furuta, G.M. Ge, D. Gonnella, T. Gruber, D.L. Hall, G.H. Hoffstaetter, J.J. Kaufman, P.N. Koufalis, J.T. Maniscalco, T.I. O'Connell, 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
	As part of a multi-laboratory research initiative on high Q0 niobium cavities for LCLS-II and other future CW SRF accelerators, Cornell has conducted an extensive research program during the last two years on impurity-doping of niobium cavities and related material characterization. Here we give an overview of these activities, and present results from single-cell studies, from vertical performance testing of nitrogen-doped nine-cell cavities, and from cryomodule testing of nitrogen-doped nine-cell cavities.
	Slides MOBA08 [8.983 MB]
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MOPB010	Field-Dependent Surface Resistance for Superconducting Niobium Accelerating Cavities: The Case of N-Doping	95
	W. Weingarten Private Address, SERGY, France R.G. Eichhorn Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The dependence of the Q-value on the RF field (Q-slope) for superconducting RF cavities is actively studied in various accelerator laboratories. Although remedies against this dependence have been found, the physical cause still remains obscure. A rather straightforward two-fluid model description of the Q-slope in the low and high field domains is extended to the case of the recently experimentally identified increase of the Q-value with the RF field obtained by so-called "N-doping”. This paper was initiated when one of the authors (W.W., retiree from CERN) visited Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, NY.
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MOPB011	How Uniform Are Cool-Downs?	100
	J.A. Robbins, R.G. Eichhorn Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Since the last SRF conference it has become clear that achieving extremely high quality factors of SRF cavities depend on the cool-down scenario. While some findings favor a fast cool-down, others suggest a slow cycle to be advantageous, and many variations to that have been investigated: the role of thermocurrents, amount of ambient magnetic field and flux trapping. This paper will investigate, how uniformly different cool-down procedures are and if they can explain the more efficient magnetic flux expulsion.
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MOPB013	Simulation of Geometry Dependent Flux Trapping	105
	J. May-Mann, R.G. Eichhorn Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Trapping or expulsion of ambient magnetic field has become an important factor in the performance of superconducting cavities with very high Q. As experimental data is limited, we set up a numerical field calculation model to study this effect in more details. We will report, how the cavity orientation, the movement of the transition to superconductivity front, and the orientation of the magnetic field contributes to the amount of magnetic field being vulnerable for trapping.
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MOPB033	LCLS-II SRF Cavity Processing Protocol Development and Baseline Cavity Performance Demonstration	159
	M. Liepe, P. Bishop, H. Conklin, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, T. Gruber, D.L. Hall, G.H. Hoffstaetter, J.J. Kaufman, G. Kulina, J.T. Maniscalco, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA M. Checchin, A.C. Crawford, A. Grassellino, C.J. Grimm, A. Hocker, M. Martinello, O.S. Melnychuk, J.P. Ozelis, A. Romanenko, A.M. Rowe, D.A. Sergatskov, W.M. Soyars, R.P. Stanek, G. Wu Fermilab, Batavia, Illinois, USA E. Daly, G.K. Davis, M.A. Drury, J.F. Fischer, A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA M.C. Ross SLAC, Menlo Park, California, USA
	Funding: Work supported, in part, by the US DOE and the LCLS-II Project under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-76SF00515. The ”Linac Coherent Light Source-II” Project will construct a 4 GeV CW superconducting RF linac in the first kilometer of the existing SLAC linac tunnel. The baseline design calls for 280 1.3 GHz nine-cell cavities with an average intrinsic quality factor Q0 of 2.7·10¹⁰ at 2K and 16 MV/m accelerating gradient. The LCLS-II high Q0 cavity treatment protocol utilizes the reduction in BCS surface resistance by nitrogen doping of the RF surface layer, which was discovered originally at FNAL. Cornell University, FNAL, and TJNAF conducted a joint high Q0 R&D program with the goal of (a) exploring the robustness of the N-doping technique and establishing the LCLS-II cavity high Q0 processing protocol suitable for production use, and (b) demonstrating that this process can reliably achieve LCLS-II cavity specification in a production acceptance testing setting. In this paper we describe the LCLS-II cavity protocol and analyze combined cavity performance data from both vertical and horizontal testing at the three partner labs, which clearly shows that LCLS-II specifications were met, and thus demonstrates readiness for LCLS-II cavity production.
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MOPB041	Cryomodule Testing of Nitrogen-Doped Cavities	182
	D. Gonnella, B. Clasby, R.G. Eichhorn, B. Elmore, F. Furuta, G.M. Ge, D.L. Hall, Y. He, G.H. Hoffstaetter, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco, T.I. O'Connell, P. Quigley, D.M. Sabol, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A. Grassellino, C.J. Grimm, J.P. Holzbauer, O.S. Melnychuk, Y.M. Pischalnikov, A. Romanenko, W. Schappert, D.A. Sergatskov Fermilab, Batavia, Illinois, USA A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: DOE and the LCLS-II High Q Project The Linac Coherent Light Source-II (LCLS-II) is a new FEL x-ray source that is planned to be constructed in the existing SLAC tunnel. In order to meet the required high Q0 specification of 2.7x10¹⁰ at 2 K and 16 MV/m, nitrogen-doping has been proposed as a preparation method for the SRF cavities in the linac. In order to test the feasibility of these goals, four nitrogen-doped cavities have been tested at Cornell in the Horizontal Test Cryomodule (HTC) in five separate tests. The first three tests consisted of cavities assembled in the HTC with high Q input coupler. The fourth test used the same cavity as the third but with the prototype high power LCLS-II coupler installed. Finally, the fifth test used a high power LCLS-II coupler, cavity tuner, and HOM antennas. Here we report on the results from these tests along with a systematic analysis of change in performance due to the various steps in preparing and assembling LCLS-II cavities for cryomodule operation. These results represent one of the final steps to demonstrate readiness for full prototype cryomodule assembly for LCLS-II.
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MOPB083	Cooling Front Measurement of a 9-Cell Cavity via the Multi-Cell Temperature-Mapping System at Cornell University	324
	G.M. Ge, R.G. Eichhorn, F. Furuta Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cooling speed significantly affects flux trapping of a SRF cavity, which will determine the residual resistance and the quality factor of the cavity. We measured the temperature distribution of a 9-cell cavity at different cooling speeds by the multi-cell T-map system of Cornell University. This paper proposed a method to evaluate the formation of a normal conducting island at different cooling speed. The fast cool-down and slow cool-down has been compared. We conclude that the slow cool-down freezes less normal conducting islands.
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MOPB084	Performance of Nitrogen-Doped 9-Cell SRF Cavities in Vertical Tests at Cornell University	328
	G.M. Ge, R.G. Eichhorn, B. Elmore, F. Furuta, D. Gonnella, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, T.I. O'Connell, J. Sears, E.N. Smith Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cornell University treated five LCLS-II 9-cell cavities by nitrogen-doping recipe. In this paper, we reported the performance of these 9-cell cavities. In the treatments, the nitrogen recipes are slightly different. The cavities have been firstly doped under high nitrogen pressure; after the vertical tests some of the cavities has been reset the surface and re-doped under light nitrogen pressure. The detail of the cavity preparation and test results will be shown. The comparison of the different recipes will be discussed.
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TUPB044	High Quality Factor Studies in SRF Nb3Sn Cavities	661
	D.L. Hall, B. Clasby, H. Conklin, R.G. Eichhorn, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by DOE grant DE-SC0008431 and NSF grant PHY-141638 A significant advantage of Nb3Sn coated on niobium over conventional bulk niobium is the substantial reduction in the BCS losses at equal temperatures of the former relative to the latter. The quality factor of a 1.3 GHz Nb3Sn cavity is thus almost entirely dictated by the residual resistance at temperatures at and below 4.2 K, which, if minimised, offers the ability to operate the cavity in liquid helium at atmospheric pressure with quality factors exceeding 4·10¹⁰. In this paper we look at the impact of the cooldown procedure – which is intrinsically linked to the effect of spatial and temporal gradients – and the impact of external ambient magnetic fields on the performance of a Nb3Sn cavity.
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TUPB081	Multi-Cell Temperature Mapping and Conclusions	783
	F. Furuta, R.G. Eichhorn, G.M. Ge, D. Gonnella, D.L. Hartill, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, E.N. Smith Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Multi-cell temperature mapping (T-map) system has been developed and applied on SRF Nb cavities vertical tests (VT) at Cornell. It has nearly two thousand thermometers and achieved a 1mK resolution of niobium surface temperature rinsing in superfluid helium . We have upgraded the system to be capable of monitoring the temperature profiles of quench spot on cavity. The recent results of T-map during cavity tests and details will be reported.
	Poster TUPB081 [4.421 MB]
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TUPB088	On Quench Propagation, Quench Detection and Second Sound in SRF Cavities	804
	S.R. Markham, R.G. Eichhorn, D.L. Hartill, G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Quench location detection has provided valuable insight in SRF cavity operation since two decades. While in earlier days temperature maps were used the state of the art technique nowadays is detecting the second sound wave, excited by a quench, using oscillating super-leak detector (OSTs). Typically, many OSTs surround the cavity and the quench location is determined by triangulation of the different OST signals. Convenient as the method is there is a mystery: taking the well-known velocity of the second sound wave, the quench seems to come from a place slightly above the cavity’s outer surface. In addition, not all triangulation spheres intersect in one point. We will present a model based on numerical quench propagation simulations that is able to fully explaining this discrepancy.
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THBA05	Higher Order Mode Absorbers for High Current SRF Applications	1036
	R.G. Eichhorn, J.V. Conway, T. Gruber, Y. He, G.H. Hoffstaetter, Y. Li, M. Liepe, T.I. O'Connell, P. Quigley, J. Sears, V.D. Shemelin, E.N. Smith, M. Tigner Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Efficient damping of the higher-order modes (HOMs) of the superconducting cavities is essential for any high current operation. The talk will provide an overview on the latest advances of HOM absorber development for high intensity SRF applications. As the ideal absorber does not exist, the different conceptual approaches will be presented and the associated issues are outlined. Design examples from various labs will be given that help explain the issues and resolutions. Some focus will be given to the Cornell HOM beamline absorber that was design for high current, short bunch operation with up to 400 W heating. The design will be reviewed and testing results will be reported.
	Slides THBA05 [4.022 MB]
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THPB093	A 1.3 GHz Waveguide to Coax Coupler for Superconducting Cavities With a Minimum Kick	1360
	J.A. Robbins, C. Egerer, R.G. Eichhorn, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Transversal forces as a result of asymmetric field generated by the fundamental power couplers have become a concern for low emittance beam in future accelerators. In pushing for smallest emittances, Cornell has finished a physics design for a symmetric coupler for superconducting accelerating cavities. This coupler consists of a rectangular waveguide that transforms into a coaxial line inside the beam pipe, eventually feeding the cavity. We will report on the RF design yielding to the extremely low transversal kick. In addition, heating, heat transfer and thermal stability of this coupler has been evaluated.
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FRAA04	Performance of the Cornell ERL Main Linac Prototype Cryomodule	1437
	F. Furuta, B. Clasby, R.G. Eichhorn, B. Elmore, G.M. Ge, D. Gonnella, D.L. Hall, G.H. Hoffstaetter, R.P.K. Kaplan, J.J. Kaufman, M. Liepe, T.I. O'Connell, S. Posen, 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
	Cornell has designed, fabricated, and tested (by the time of the conference) a high current (100 mA) CW SRF prototype cryomodule for the Cornell ERL. This talk will report on the design and performance of this very high Q0 CW cryomodule including design issues and mitigation strategies.
	Slides FRAA04 [4.614 MB]
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Paper

Title

Page

Niobium Impurity-Doping Studies at Cornell and CM Cool-Down Dynamic Effect on Q0

55

M. Liepe, B. Clasby, R.G. Eichhorn, B. Elmore, F. Furuta, G.M. Ge, D. Gonnella, T. Gruber, D.L. Hall, G.H. Hoffstaetter, J.J. Kaufman, P.N. Koufalis, J.T. Maniscalco, T.I. O'Connell, 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

As part of a multi-laboratory research initiative on high Q0 niobium cavities for LCLS-II and other future CW SRF accelerators, Cornell has conducted an extensive research program during the last two years on impurity-doping of niobium cavities and related material characterization. Here we give an overview of these activities, and present results from single-cell studies, from vertical performance testing of nitrogen-doped nine-cell cavities, and from cryomodule testing of nitrogen-doped nine-cell cavities.

Slides MOBA08 [8.983 MB]

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MOPB010

Field-Dependent Surface Resistance for Superconducting Niobium Accelerating Cavities: The Case of N-Doping

95

W. Weingarten
Private Address, SERGY, France
R.G. Eichhorn
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The dependence of the Q-value on the RF field (Q-slope) for superconducting RF cavities is actively studied in various accelerator laboratories. Although remedies against this dependence have been found, the physical cause still remains obscure. A rather straightforward two-fluid model description of the Q-slope in the low and high field domains is extended to the case of the recently experimentally identified increase of the Q-value with the RF field obtained by so-called "N-doping”.
This paper was initiated when one of the authors (W.W., retiree from CERN) visited Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, NY.

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MOPB011

How Uniform Are Cool-Downs?

100

J.A. Robbins, R.G. Eichhorn
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Since the last SRF conference it has become clear that achieving extremely high quality factors of SRF cavities depend on the cool-down scenario. While some findings favor a fast cool-down, others suggest a slow cycle to be advantageous, and many variations to that have been investigated: the role of thermocurrents, amount of ambient magnetic field and flux trapping. This paper will investigate, how uniformly different cool-down procedures are and if they can explain the more efficient magnetic flux expulsion.

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MOPB013

Simulation of Geometry Dependent Flux Trapping

105

J. May-Mann, R.G. Eichhorn
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Trapping or expulsion of ambient magnetic field has become an important factor in the performance of superconducting cavities with very high Q. As experimental data is limited, we set up a numerical field calculation model to study this effect in more details. We will report, how the cavity orientation, the movement of the transition to superconductivity front, and the orientation of the magnetic field contributes to the amount of magnetic field being vulnerable for trapping.

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MOPB033

LCLS-II SRF Cavity Processing Protocol Development and Baseline Cavity Performance Demonstration

159

M. Liepe, P. Bishop, H. Conklin, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, T. Gruber, D.L. Hall, G.H. Hoffstaetter, J.J. Kaufman, G. Kulina, J.T. Maniscalco, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
M. Checchin, A.C. Crawford, A. Grassellino, C.J. Grimm, A. Hocker, M. Martinello, O.S. Melnychuk, J.P. Ozelis, A. Romanenko, A.M. Rowe, D.A. Sergatskov, W.M. Soyars, R.P. Stanek, G. Wu
Fermilab, Batavia, Illinois, USA
E. Daly, G.K. Davis, M.A. Drury, J.F. Fischer, A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA
M.C. Ross
SLAC, Menlo Park, California, USA

Funding: Work supported, in part, by the US DOE and the LCLS-II Project under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-76SF00515.
The ”Linac Coherent Light Source-II” Project will construct a 4 GeV CW superconducting RF linac in the first kilometer of the existing SLAC linac tunnel. The baseline design calls for 280 1.3 GHz nine-cell cavities with an average intrinsic quality factor Q0 of 2.7·10¹⁰ at 2K and 16 MV/m accelerating gradient. The LCLS-II high Q0 cavity treatment protocol utilizes the reduction in BCS surface resistance by nitrogen doping of the RF surface layer, which was discovered originally at FNAL. Cornell University, FNAL, and TJNAF conducted a joint high Q0 R&D program with the goal of (a) exploring the robustness of the N-doping technique and establishing the LCLS-II cavity high Q0 processing protocol suitable for production use, and (b) demonstrating that this process can reliably achieve LCLS-II cavity specification in a production acceptance testing setting. In this paper we describe the LCLS-II cavity protocol and analyze combined cavity performance data from both vertical and horizontal testing at the three partner labs, which clearly shows that LCLS-II specifications were met, and thus demonstrates readiness for LCLS-II cavity production.

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MOPB041

Cryomodule Testing of Nitrogen-Doped Cavities

182

D. Gonnella, B. Clasby, R.G. Eichhorn, B. Elmore, F. Furuta, G.M. Ge, D.L. Hall, Y. He, G.H. Hoffstaetter, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco, T.I. O'Connell, P. Quigley, D.M. Sabol, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Grassellino, C.J. Grimm, J.P. Holzbauer, O.S. Melnychuk, Y.M. Pischalnikov, A. Romanenko, W. Schappert, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: DOE and the LCLS-II High Q Project
The Linac Coherent Light Source-II (LCLS-II) is a new FEL x-ray source that is planned to be constructed in the existing SLAC tunnel. In order to meet the required high Q0 specification of 2.7x10¹⁰ at 2 K and 16 MV/m, nitrogen-doping has been proposed as a preparation method for the SRF cavities in the linac. In order to test the feasibility of these goals, four nitrogen-doped cavities have been tested at Cornell in the Horizontal Test Cryomodule (HTC) in five separate tests. The first three tests consisted of cavities assembled in the HTC with high Q input coupler. The fourth test used the same cavity as the third but with the prototype high power LCLS-II coupler installed. Finally, the fifth test used a high power LCLS-II coupler, cavity tuner, and HOM antennas. Here we report on the results from these tests along with a systematic analysis of change in performance due to the various steps in preparing and assembling LCLS-II cavities for cryomodule operation. These results represent one of the final steps to demonstrate readiness for full prototype cryomodule assembly for LCLS-II.

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MOPB083

Cooling Front Measurement of a 9-Cell Cavity via the Multi-Cell Temperature-Mapping System at Cornell University

324

G.M. Ge, R.G. Eichhorn, F. Furuta
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cooling speed significantly affects flux trapping of a SRF cavity, which will determine the residual resistance and the quality factor of the cavity. We measured the temperature distribution of a 9-cell cavity at different cooling speeds by the multi-cell T-map system of Cornell University. This paper proposed a method to evaluate the formation of a normal conducting island at different cooling speed. The fast cool-down and slow cool-down has been compared. We conclude that the slow cool-down freezes less normal conducting islands.

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MOPB084

Performance of Nitrogen-Doped 9-Cell SRF Cavities in Vertical Tests at Cornell University

328

G.M. Ge, R.G. Eichhorn, B. Elmore, F. Furuta, D. Gonnella, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, T.I. O'Connell, J. Sears, E.N. Smith
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell University treated five LCLS-II 9-cell cavities by nitrogen-doping recipe. In this paper, we reported the performance of these 9-cell cavities. In the treatments, the nitrogen recipes are slightly different. The cavities have been firstly doped under high nitrogen pressure; after the vertical tests some of the cavities has been reset the surface and re-doped under light nitrogen pressure. The detail of the cavity preparation and test results will be shown. The comparison of the different recipes will be discussed.

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TUPB044

High Quality Factor Studies in SRF Nb3Sn Cavities

661

D.L. Hall, B. Clasby, H. Conklin, R.G. Eichhorn, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by DOE grant DE-SC0008431 and NSF grant PHY-141638
A significant advantage of Nb3Sn coated on niobium over conventional bulk niobium is the substantial reduction in the BCS losses at equal temperatures of the former relative to the latter. The quality factor of a 1.3 GHz Nb3Sn cavity is thus almost entirely dictated by the residual resistance at temperatures at and below 4.2 K, which, if minimised, offers the ability to operate the cavity in liquid helium at atmospheric pressure with quality factors exceeding 4·10¹⁰. In this paper we look at the impact of the cooldown procedure – which is intrinsically linked to the effect of spatial and temporal gradients – and the impact of external ambient magnetic fields on the performance of a Nb3Sn cavity.

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TUPB081

Multi-Cell Temperature Mapping and Conclusions

783

F. Furuta, R.G. Eichhorn, G.M. Ge, D. Gonnella, D.L. Hartill, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, E.N. Smith
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Multi-cell temperature mapping (T-map) system has been developed and applied on SRF Nb cavities vertical tests (VT) at Cornell. It has nearly two thousand thermometers and achieved a 1mK resolution of niobium surface temperature rinsing in superfluid helium . We have upgraded the system to be capable of monitoring the temperature profiles of quench spot on cavity. The recent results of T-map during cavity tests and details will be reported.

Poster TUPB081 [4.421 MB]

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TUPB088

On Quench Propagation, Quench Detection and Second Sound in SRF Cavities

804

S.R. Markham, R.G. Eichhorn, D.L. Hartill, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Quench location detection has provided valuable insight in SRF cavity operation since two decades. While in earlier days temperature maps were used the state of the art technique nowadays is detecting the second sound wave, excited by a quench, using oscillating super-leak detector (OSTs). Typically, many OSTs surround the cavity and the quench location is determined by triangulation of the different OST signals. Convenient as the method is there is a mystery: taking the well-known velocity of the second sound wave, the quench seems to come from a place slightly above the cavity’s outer surface. In addition, not all triangulation spheres intersect in one point. We will present a model based on numerical quench propagation simulations that is able to fully explaining this discrepancy.

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THBA05

Higher Order Mode Absorbers for High Current SRF Applications

1036

R.G. Eichhorn, J.V. Conway, T. Gruber, Y. He, G.H. Hoffstaetter, Y. Li, M. Liepe, T.I. O'Connell, P. Quigley, J. Sears, V.D. Shemelin, E.N. Smith, M. Tigner
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Efficient damping of the higher-order modes (HOMs) of the superconducting cavities is essential for any high current operation. The talk will provide an overview on the latest advances of HOM absorber development for high intensity SRF applications. As the ideal absorber does not exist, the different conceptual approaches will be presented and the associated issues are outlined. Design examples from various labs will be given that help explain the issues and resolutions. Some focus will be given to the Cornell HOM beamline absorber that was design for high current, short bunch operation with up to 400 W heating. The design will be reviewed and testing results will be reported.

Slides THBA05 [4.022 MB]

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THPB093

A 1.3 GHz Waveguide to Coax Coupler for Superconducting Cavities With a Minimum Kick

1360

J.A. Robbins, C. Egerer, R.G. Eichhorn, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Transversal forces as a result of asymmetric field generated by the fundamental power couplers have become a concern for low emittance beam in future accelerators. In pushing for smallest emittances, Cornell has finished a physics design for a symmetric coupler for superconducting accelerating cavities. This coupler consists of a rectangular waveguide that transforms into a coaxial line inside the beam pipe, eventually feeding the cavity. We will report on the RF design yielding to the extremely low transversal kick. In addition, heating, heat transfer and thermal stability of this coupler has been evaluated.

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FRAA04

Performance of the Cornell ERL Main Linac Prototype Cryomodule

1437

F. Furuta, B. Clasby, R.G. Eichhorn, B. Elmore, G.M. Ge, D. Gonnella, D.L. Hall, G.H. Hoffstaetter, R.P.K. Kaplan, J.J. Kaufman, M. Liepe, T.I. O'Connell, S. Posen, 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

Cornell has designed, fabricated, and tested (by the time of the conference) a high current (100 mA) CW SRF prototype cryomodule for the Cornell ERL. This talk will report on the design and performance of this very high Q0 CW cryomodule including design issues and mitigation strategies.

Slides FRAA04 [4.614 MB]

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