SRF2013 - List of Authors (Sergatskov, D.A.)

Paper

Title

Page

Cold Tests of SSR1 Resonators for PXIE

112

A.I. Sukhanov, M.H. Awida, P. Berrutti, C.M. Ginsburg, T.N. Khabiboulline, O.S. Melnychuk, R.V. Pilipenko, Y.M. Pischalnikov, L. Ristori, A.M. Rowe, D.A. Sergatskov, V.P. Yakovlev
Fermilab, Batavia, USA

Fermilab is currently building the Project X Injector experiment (PXIE). PXIE linac will accelerate 1 mA H⁻ beam up to 30 MeV and serve as a testbed for validation of Project X concepts and mitigation of technical risks. A cryomodule of eight superconducting RF Single Spoke Resonators of type 1 (SSR1) cavities operating at 325 MHz is an integral part of PXIE. Ten SSR1 cavities were manufactured in industry and delivered to Fermilab. In this paper we discuss surface processing and tests of bare SSR1 cavities at the Fermilab Vertical Test Stand (VTS). We report on the measured performance parameters of nine cavities achieved during tests.

MOP015

Status of the SRF Development for the Project X

117

V.P. Yakovlev, T.T. Arkan, M.H. Awida, P. Berrutti, E. Borissov, A.C. Crawford, M.H. Foley, C.M. Ginsburg, I.V. Gonin, A. Grassellino, C.J. Grimm, S.D. Holmes, S. Kazakov, R.D. Kephart, T.N. Khabiboulline, V.A. Lebedev, A. Lunin, M. Merio, S. Nagaitsev, T.H. Nicol, Y.O. Orlov, D. Passarelli, T.J. Peterson, Y.M. Pischalnikov, O.V. Pronitchev, L. Ristori, A.M. Rowe, D.A. Sergatskov, N. Solyak, A.I. Sukhanov, I. Terechkine
Fermilab, Batavia, USA

Project X is a high intensity proton facility being developed to support a world-leading program of Intensity Frontier physics over the next two decades at Fermilab. The proposed facility is based on the SRF technology and consists of two linacs: CW linac to accelerate beam from 2.1 MeV to 3 GeV and pulsed linac accelerate 5% of the beam up to 8 GeV. In a CW linac five families of SC cavities are used: half-wave resonators (162.5 MHz); single-spoke cavities: SSR1 and SSR2 (325 MHz) and elliptical 5-cell β=0.6 and β=0.9 cavities (650 MHz). Pulsed 3-8 GeV linac linac are based on 9-cell 1.3 GHz cavities. In the paper the basic requirements and the status of development of SC accelerating cavities, auxiliaries (couplers, tuners, etc.) and cryomodules are presented as well as technology challenges caused by their specifics.

MOP073

IHEP 1.3 GHz Low Loss Large Grain 9-cell Cavity Fabrication, Processing and Test

305

J.Y. Zhai, J. Gao, S. Jin, Z.Q. Li, Y. Liu, Z.C. Liu, Z.H. Mi, X.H. Peng, T.X. Zhao, H.J. Zheng
IHEP, Beijing, People's Republic of China
C.A. Cooper, C.M. Ginsburg, T.N. Khabiboulline, A.M. Rowe, D.A. Sergatskov
Fermilab, Batavia, USA
J.X. Wang, H. Yu, H. Yuan
BIAM, Beijing, People's Republic of China

The combination of the low-loss shape and large grain niobium material is expected to be the possible way to achieve higher gradient and lower cost for ILC 9-cell cavities, and will be essential for the ILC 1 TeV upgrade. As the key component of the “IHEP 1.3 GHz SRF Accelerating Unit Project”, a low-loss shape 9-cell cavity with full end groups using Ningxia large grain niobium (IHEP-02) was fabricated at IHEP in 2012. The cavity was processed (CBP and EP) and tested at FNAL. The cavity processing,test performance and gradient limitation is reported in this paper. We will weld the helium vessel, assemble the magnetic shield and install the cavity to IHEP ILC-TC1 cryomodule.

MOP090

Feasibility of Using Conductively Cooled Magnets in Cryomodules of Superconducting Linacs

361

I. Terechkine, S. Cheban, T.H. Nicol, V. Poloubotko, D.A. Sergatskov
Fermilab, Batavia, USA

While trying to find an optimal way to configure cryomodule for the low energy part of a high-current, high-power superconducting linac, an option of using conductively cooled superconducting focusing lenses was evaluated. As part of this evaluation, several tests were made using existing test cryostat. The cryostat was modified by adding current feed-throughs and two conductively cooled current leads, each equipped with heat sinks at the temperatures of liquid nitrogen and liquid helium. A superconducting magnet was mounted inside the cryostat on an individual heat sink, and thermometers were installed on the leads, heat sinks, and on the magnet’s winding. In this report we provide some details of the heat exchangers’ designs, compare predicted and measured temperature distribution along the leads, and analyze results of the winding temperature measurements.

TUP030

Elimination of post annealing chemistry: a route to high Q cavities and processing simplification

A. Grassellino, A.C. Crawford, R.D. Kephart, O.S. Melnychuk, A. Romanenko, A.M. Rowe, D.A. Sergatskov, M. Wong
Fermilab, Batavia, USA
M. Checchin
INFN/LNL, Legnaro (PD), Italy
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.
We investigate the effect of high temperature treatments followed by only high-pressure water rinse (HPR) of superconducting radio frequency (SRF) niobium cavities. The objective is to provide a cost effective alternative to the typical cavity processing sequence, by eliminating the material removal step post furnace treatment while preserving or improving the RF performance. The studies have been conducted in the temperature range 800-1000C for different conditions of the starting substrate: large grain and fine grain, electro-polished (EP) and centrifugal barrel polished (CBP) to mirror finish. An interesting effect of the grain size on the performances is found. Cavity results and samples characterization show that furnace contaminants cause poor cavity performance, and a practical solution is found to prevent surface contamination. Extraordinary values of residual resistances ~ 1 nOhm and below are then consistently achieved for the contamination-free cavities. We explore the addition of a small partial pressure of gas during the anneal to further increase the cavity quality factor by reducing the BCS resistance.

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)

TUP038

Field Dependence of Residual and BCS Surface Resistances Measured by Explicit Deconvolution Up to High Fields

A. Romanenko, A. Grassellino, O.S. Melnychuk, D.A. Sergatskov
Fermilab, Batavia, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
For both fundamental understanding of performance limiting processes and practical design of future accelerators a crucial information is the temperature and field dependence of the components in surface resistance. We report an explicit deconvolution of temperature-independent residual (Rres) and temperature-dependent BCS (Rbcs) components in multiple cavities treated by standard processing techniques (EP, BCP, 120C bake, 800C degassing) at all fields up to Brf > 100 mT. Such deconvolution allows to address the nature of the low, medium, and high field Q slopes, and provides input for accelerator parametric design optimization.

TUP040

Quench Dynamics in SRF Cavities

D.A. Sergatskov, I. Terechkine, V.P. Yakovlev
Fermilab, Batavia, USA
S. Antipov
University of Chicago, Chicago, Illinois, USA
E. Toropov
CMU, Pittsburgh, Pennsylvania, USA

Funding: The work herein has been performed at Fermilab, which is operated by Fermi Research Alliance, LLC under Contract with the United States Department of Energy.
A quench in SRF cavities is a thermal runaway process that causes a rapid loss of the stored RF energy. A quench is one of the factors that limits performance of the cavity. We have developed a comprehensive model describing the thermal and electromagnetic dynamics in the quench zone of an SRF cavity. The model has already provided us with insights essential to improved performance of SRF cavities. The predicted size of the hot spot that emits 2nd-sound during the quench is important for the Oscillating Sound Transducer (OST) quench detection technique; the maximum size of the normal zone formed during the quench determines cavity quality degradation; anomalous RF decay time distinguishes a real quench from other mechanisms of sudden loss of RF power in the cavities. We describe the model, discuss the most important results and compare them to experimental data.

TUP050

R&D Program for 650 MHz Niobium Cavities for Project X

A. Grassellino, A.C. Crawford, C.M. Ginsburg, R.D. Kephart, T.N. Khabiboulline, O.S. Melnychuk, A. Romanenko, A.M. Rowe, D.A. Sergatskov, A.I. Sukhanov, M. Wong, V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
We report the first test results of several 650 MHz single cell niobium cavities processed at Fermilab. The target for the 5-cell 650 MHz cavities for Project X is CW operation at magnetic peak field ~ 60-70 mT, making high quality factors at medium accelerating fields the main goal of the surface processing R&D. We will discuss how the performance vary with the different surface processing and parameters/criteria of choice for the final surface preparation sequence.

TUP060

Acid Free Extended Mechanical Polishing R&D

564

C.A. Cooper, A.C. Crawford, C.M. Ginsburg, A. Grassellino, R.D. Kephart, O.S. Melnychuk, A. Romanenko, A.M. Rowe, D.A. Sergatskov
Fermilab, Batavia, USA

We report the progress in the development of a centrifugal barrel polishing recipe which can lead to standard cavity performance without the need of any chemical treatments. Q ~ 10¹⁰ at 20 MV/m and gradients above 35 MV/m have already been demonstrated for cavities whose preparation sequence was CBP, degassing and no subsequent chemical treatments. Results of studies on the effect of different CBP media on RF performance will be reported, including full body T-map showing the distribution of RF losses.

TUP112

Time-Resolved Measurements of High-Field Quench in SRF Cavities

743

S. Antipov
University of Chicago, Chicago, Illinois, USA
E. Efimenko
MIPT, Dolgoprudniy, Moscow Region, Russia
A. Romanenko, D.A. Sergatskov
Fermilab, Batavia, USA

Fermilab’s temperature mapping system for SRF cavities has been improved to observe quench dynamics with 1ms time resolution. The increase in sampling rate was achieved by localizing the quench and then performing the measurements using a limited subset of thermometers. Implemented experimental procedure allowed to measure temperature distribution within quench spot, as well as the amount of stored energy, at the moment quench starts, during its growth, and decay. For three tested SRF cavities, quenching at fields 21.7 – 33 MeV/m, maximal radius of the normal zone was 40 – 65 mm; time to return to superconducting state: 90 – 250 ms. In the beginning of the process temperature increase rate in the center of the normal zone is as high as 2.5 K/ms, radius increase rate – 20 mm/ms. The described experimental procedure can be useful for investigating how different surface treatments affect the breakdown, understanding of the nature of high-field quench, improvement of quench detection techniques, and material science research for future SRF cavities.

THP030

Superconducting RF Cavity Development With UK Industry

966

A.E. Wheelhouse, R.K. Buckley, L.S. Cowie, P. Goudket, A.R. Goulden, P.A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C.A. Cooper, C.M. Ginsburg, A. Grassellino, O.S. Melnychuk, A.M. Rowe, D.A. Sergatskov
Fermilab, Batavia, USA
J.R. Everard, N. Shakespeare
Shakespeare Engineering, South Woodham Ferrers, Essex, United Kingdom

As part of a continuing STFC Innovations Partnership Scheme (IPS) grant, in support of enabling UK industry to address the large potential market for superconducting RF structures Daresbury Laboratory and Shakespeare Engineering Ltd are developing the capability to fabricate, process and test a niobium 9-cell 1.3 GHz superconducting RF cavity. A single-cell cavity fabricated under this grant was surface processed and tested at Fermilab, and achieved an accelerating gradient in excess of 40 MV/m at an unloaded quality factor in excess of 1.0 x 10¹⁰. This paper presents the results of the single-cell cavity testing and discusses the progress made to date in the development of the design and manufacture of a 9-cell niobium cavity, which Shakespeare Engineering Ltd will fabricate and which is anticipated to be qualified in 2014.

THP047

Performance Degradation of a Superconducting Cavity Quenching in Magnetic Field

1013

I. Terechkine, T.N. Khabiboulline, D.A. Sergatskov
Fermilab, Batavia, USA

Although degradation of a superconducting RF (SRF) cavity performance induced by magnetic field trapped in its walls is a well understood phenomenon, a criterion for an acceptable level of magnetic field existing in the vicinity of an SRF cavity and generated after the cavity is cooled down has not been agreed upon. The bulk of superconducting Nb should protect the RF surface of the cavity from the magnetic field on the outside; nevertheless a failure mode exists when the cavity quenches while the external field is applied. The amount of trapped magnetic flux in this case depends on the size of normally conducting zone developed in walls of the cavity during quenching. Although propagation of the normally conducting zone in walls of a cavity can be modeled, no dedicated studies of this process that would include experimental verifications of its impact on the cavity performance could be found. We tried to address his issue in a special study by using as an example a superconducting coil mounted near a quenching cavity; the method and some results of the study can be applied to any RF structure and magnetic system.

FRIOB02

Development and Performance of 325 MHz Single Spoke Resonators for Project X

1187

L. Ristori, M.H. Awida, P. Berrutti, C.M. Ginsburg, I.V. Gonin, T.N. Khabiboulline, M. Merio, T.H. Nicol, D. Passarelli, A.M. Rowe, D.A. Sergatskov, A.I. Sukhanov, V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
Two types of single spoke resonators will be utilized for beam-acceleration in the low energy part of the Project X linac. SSR1 and SSR2 operate at 325 MHz and at an optimal beta of 0.22 and 0.51 respectively. After the initial phase of prototyping, a production run of 10 SSR1 resonators was recently completed in US industry. The qualification of this group of resonators in the Fermilab VTS is proceeding successfully and nearly complete. The first qualified resonator has been outfitted with a Stainless Steel helium vessel. Preliminary test results for the first jacketed SSR1 are presented. The first RF power couplers were ordered, the design of the double-lever tuning mechanism is almost complete.

Slides FRIOB02 [8.800 MB]

Paper	Title	Page
MOP014	Cold Tests of SSR1 Resonators for PXIE	112
	A.I. Sukhanov, M.H. Awida, P. Berrutti, C.M. Ginsburg, T.N. Khabiboulline, O.S. Melnychuk, R.V. Pilipenko, Y.M. Pischalnikov, L. Ristori, A.M. Rowe, D.A. Sergatskov, V.P. Yakovlev Fermilab, Batavia, USA
	Fermilab is currently building the Project X Injector experiment (PXIE). PXIE linac will accelerate 1 mA H⁻ beam up to 30 MeV and serve as a testbed for validation of Project X concepts and mitigation of technical risks. A cryomodule of eight superconducting RF Single Spoke Resonators of type 1 (SSR1) cavities operating at 325 MHz is an integral part of PXIE. Ten SSR1 cavities were manufactured in industry and delivered to Fermilab. In this paper we discuss surface processing and tests of bare SSR1 cavities at the Fermilab Vertical Test Stand (VTS). We report on the measured performance parameters of nine cavities achieved during tests.

MOP015	Status of the SRF Development for the Project X	117
	V.P. Yakovlev, T.T. Arkan, M.H. Awida, P. Berrutti, E. Borissov, A.C. Crawford, M.H. Foley, C.M. Ginsburg, I.V. Gonin, A. Grassellino, C.J. Grimm, S.D. Holmes, S. Kazakov, R.D. Kephart, T.N. Khabiboulline, V.A. Lebedev, A. Lunin, M. Merio, S. Nagaitsev, T.H. Nicol, Y.O. Orlov, D. Passarelli, T.J. Peterson, Y.M. Pischalnikov, O.V. Pronitchev, L. Ristori, A.M. Rowe, D.A. Sergatskov, N. Solyak, A.I. Sukhanov, I. Terechkine Fermilab, Batavia, USA
	Project X is a high intensity proton facility being developed to support a world-leading program of Intensity Frontier physics over the next two decades at Fermilab. The proposed facility is based on the SRF technology and consists of two linacs: CW linac to accelerate beam from 2.1 MeV to 3 GeV and pulsed linac accelerate 5% of the beam up to 8 GeV. In a CW linac five families of SC cavities are used: half-wave resonators (162.5 MHz); single-spoke cavities: SSR1 and SSR2 (325 MHz) and elliptical 5-cell β=0.6 and β=0.9 cavities (650 MHz). Pulsed 3-8 GeV linac linac are based on 9-cell 1.3 GHz cavities. In the paper the basic requirements and the status of development of SC accelerating cavities, auxiliaries (couplers, tuners, etc.) and cryomodules are presented as well as technology challenges caused by their specifics.

MOP073	IHEP 1.3 GHz Low Loss Large Grain 9-cell Cavity Fabrication, Processing and Test	305
	J.Y. Zhai, J. Gao, S. Jin, Z.Q. Li, Y. Liu, Z.C. Liu, Z.H. Mi, X.H. Peng, T.X. Zhao, H.J. Zheng IHEP, Beijing, People's Republic of China C.A. Cooper, C.M. Ginsburg, T.N. Khabiboulline, A.M. Rowe, D.A. Sergatskov Fermilab, Batavia, USA J.X. Wang, H. Yu, H. Yuan BIAM, Beijing, People's Republic of China
	The combination of the low-loss shape and large grain niobium material is expected to be the possible way to achieve higher gradient and lower cost for ILC 9-cell cavities, and will be essential for the ILC 1 TeV upgrade. As the key component of the “IHEP 1.3 GHz SRF Accelerating Unit Project”, a low-loss shape 9-cell cavity with full end groups using Ningxia large grain niobium (IHEP-02) was fabricated at IHEP in 2012. The cavity was processed (CBP and EP) and tested at FNAL. The cavity processing,test performance and gradient limitation is reported in this paper. We will weld the helium vessel, assemble the magnetic shield and install the cavity to IHEP ILC-TC1 cryomodule.

MOP090	Feasibility of Using Conductively Cooled Magnets in Cryomodules of Superconducting Linacs	361
	I. Terechkine, S. Cheban, T.H. Nicol, V. Poloubotko, D.A. Sergatskov Fermilab, Batavia, USA
	While trying to find an optimal way to configure cryomodule for the low energy part of a high-current, high-power superconducting linac, an option of using conductively cooled superconducting focusing lenses was evaluated. As part of this evaluation, several tests were made using existing test cryostat. The cryostat was modified by adding current feed-throughs and two conductively cooled current leads, each equipped with heat sinks at the temperatures of liquid nitrogen and liquid helium. A superconducting magnet was mounted inside the cryostat on an individual heat sink, and thermometers were installed on the leads, heat sinks, and on the magnet’s winding. In this report we provide some details of the heat exchangers’ designs, compare predicted and measured temperature distribution along the leads, and analyze results of the winding temperature measurements.

TUP030	Elimination of post annealing chemistry: a route to high Q cavities and processing simplification
	A. Grassellino, A.C. Crawford, R.D. Kephart, O.S. Melnychuk, A. Romanenko, A.M. Rowe, D.A. Sergatskov, M. Wong Fermilab, Batavia, USA M. Checchin INFN/LNL, Legnaro (PD), Italy 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. We investigate the effect of high temperature treatments followed by only high-pressure water rinse (HPR) of superconducting radio frequency (SRF) niobium cavities. The objective is to provide a cost effective alternative to the typical cavity processing sequence, by eliminating the material removal step post furnace treatment while preserving or improving the RF performance. The studies have been conducted in the temperature range 800-1000C for different conditions of the starting substrate: large grain and fine grain, electro-polished (EP) and centrifugal barrel polished (CBP) to mirror finish. An interesting effect of the grain size on the performances is found. Cavity results and samples characterization show that furnace contaminants cause poor cavity performance, and a practical solution is found to prevent surface contamination. Extraordinary values of residual resistances ~ 1 nOhm and below are then consistently achieved for the contamination-free cavities. We explore the addition of a small partial pressure of gas during the anneal to further increase the cavity quality factor by reducing the BCS resistance.

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)

TUP038	Field Dependence of Residual and BCS Surface Resistances Measured by Explicit Deconvolution Up to High Fields
	A. Romanenko, A. Grassellino, O.S. Melnychuk, D.A. Sergatskov Fermilab, Batavia, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. For both fundamental understanding of performance limiting processes and practical design of future accelerators a crucial information is the temperature and field dependence of the components in surface resistance. We report an explicit deconvolution of temperature-independent residual (Rres) and temperature-dependent BCS (Rbcs) components in multiple cavities treated by standard processing techniques (EP, BCP, 120C bake, 800C degassing) at all fields up to Brf > 100 mT. Such deconvolution allows to address the nature of the low, medium, and high field Q slopes, and provides input for accelerator parametric design optimization.

TUP040	Quench Dynamics in SRF Cavities
	D.A. Sergatskov, I. Terechkine, V.P. Yakovlev Fermilab, Batavia, USA S. Antipov University of Chicago, Chicago, Illinois, USA E. Toropov CMU, Pittsburgh, Pennsylvania, USA
	Funding: The work herein has been performed at Fermilab, which is operated by Fermi Research Alliance, LLC under Contract with the United States Department of Energy. A quench in SRF cavities is a thermal runaway process that causes a rapid loss of the stored RF energy. A quench is one of the factors that limits performance of the cavity. We have developed a comprehensive model describing the thermal and electromagnetic dynamics in the quench zone of an SRF cavity. The model has already provided us with insights essential to improved performance of SRF cavities. The predicted size of the hot spot that emits 2nd-sound during the quench is important for the Oscillating Sound Transducer (OST) quench detection technique; the maximum size of the normal zone formed during the quench determines cavity quality degradation; anomalous RF decay time distinguishes a real quench from other mechanisms of sudden loss of RF power in the cavities. We describe the model, discuss the most important results and compare them to experimental data.

TUP050	R&D Program for 650 MHz Niobium Cavities for Project X
	A. Grassellino, A.C. Crawford, C.M. Ginsburg, R.D. Kephart, T.N. Khabiboulline, O.S. Melnychuk, A. Romanenko, A.M. Rowe, D.A. Sergatskov, A.I. Sukhanov, M. Wong, V.P. Yakovlev Fermilab, Batavia, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. We report the first test results of several 650 MHz single cell niobium cavities processed at Fermilab. The target for the 5-cell 650 MHz cavities for Project X is CW operation at magnetic peak field ~ 60-70 mT, making high quality factors at medium accelerating fields the main goal of the surface processing R&D. We will discuss how the performance vary with the different surface processing and parameters/criteria of choice for the final surface preparation sequence.

TUP060	Acid Free Extended Mechanical Polishing R&D	564
	C.A. Cooper, A.C. Crawford, C.M. Ginsburg, A. Grassellino, R.D. Kephart, O.S. Melnychuk, A. Romanenko, A.M. Rowe, D.A. Sergatskov Fermilab, Batavia, USA
	We report the progress in the development of a centrifugal barrel polishing recipe which can lead to standard cavity performance without the need of any chemical treatments. Q ~ 10¹⁰ at 20 MV/m and gradients above 35 MV/m have already been demonstrated for cavities whose preparation sequence was CBP, degassing and no subsequent chemical treatments. Results of studies on the effect of different CBP media on RF performance will be reported, including full body T-map showing the distribution of RF losses.

TUP112	Time-Resolved Measurements of High-Field Quench in SRF Cavities	743
	S. Antipov University of Chicago, Chicago, Illinois, USA E. Efimenko MIPT, Dolgoprudniy, Moscow Region, Russia A. Romanenko, D.A. Sergatskov Fermilab, Batavia, USA
	Fermilab’s temperature mapping system for SRF cavities has been improved to observe quench dynamics with 1ms time resolution. The increase in sampling rate was achieved by localizing the quench and then performing the measurements using a limited subset of thermometers. Implemented experimental procedure allowed to measure temperature distribution within quench spot, as well as the amount of stored energy, at the moment quench starts, during its growth, and decay. For three tested SRF cavities, quenching at fields 21.7 – 33 MeV/m, maximal radius of the normal zone was 40 – 65 mm; time to return to superconducting state: 90 – 250 ms. In the beginning of the process temperature increase rate in the center of the normal zone is as high as 2.5 K/ms, radius increase rate – 20 mm/ms. The described experimental procedure can be useful for investigating how different surface treatments affect the breakdown, understanding of the nature of high-field quench, improvement of quench detection techniques, and material science research for future SRF cavities.

THP030	Superconducting RF Cavity Development With UK Industry	966
	A.E. Wheelhouse, R.K. Buckley, L.S. Cowie, P. Goudket, A.R. Goulden, P.A. McIntosh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom C.A. Cooper, C.M. Ginsburg, A. Grassellino, O.S. Melnychuk, A.M. Rowe, D.A. Sergatskov Fermilab, Batavia, USA J.R. Everard, N. Shakespeare Shakespeare Engineering, South Woodham Ferrers, Essex, United Kingdom
	As part of a continuing STFC Innovations Partnership Scheme (IPS) grant, in support of enabling UK industry to address the large potential market for superconducting RF structures Daresbury Laboratory and Shakespeare Engineering Ltd are developing the capability to fabricate, process and test a niobium 9-cell 1.3 GHz superconducting RF cavity. A single-cell cavity fabricated under this grant was surface processed and tested at Fermilab, and achieved an accelerating gradient in excess of 40 MV/m at an unloaded quality factor in excess of 1.0 x 10¹⁰. This paper presents the results of the single-cell cavity testing and discusses the progress made to date in the development of the design and manufacture of a 9-cell niobium cavity, which Shakespeare Engineering Ltd will fabricate and which is anticipated to be qualified in 2014.

THP047	Performance Degradation of a Superconducting Cavity Quenching in Magnetic Field	1013
	I. Terechkine, T.N. Khabiboulline, D.A. Sergatskov Fermilab, Batavia, USA
	Although degradation of a superconducting RF (SRF) cavity performance induced by magnetic field trapped in its walls is a well understood phenomenon, a criterion for an acceptable level of magnetic field existing in the vicinity of an SRF cavity and generated after the cavity is cooled down has not been agreed upon. The bulk of superconducting Nb should protect the RF surface of the cavity from the magnetic field on the outside; nevertheless a failure mode exists when the cavity quenches while the external field is applied. The amount of trapped magnetic flux in this case depends on the size of normally conducting zone developed in walls of the cavity during quenching. Although propagation of the normally conducting zone in walls of a cavity can be modeled, no dedicated studies of this process that would include experimental verifications of its impact on the cavity performance could be found. We tried to address his issue in a special study by using as an example a superconducting coil mounted near a quenching cavity; the method and some results of the study can be applied to any RF structure and magnetic system.

FRIOB02	Development and Performance of 325 MHz Single Spoke Resonators for Project X	1187
	L. Ristori, M.H. Awida, P. Berrutti, C.M. Ginsburg, I.V. Gonin, T.N. Khabiboulline, M. Merio, T.H. Nicol, D. Passarelli, A.M. Rowe, D.A. Sergatskov, A.I. Sukhanov, V.P. Yakovlev Fermilab, Batavia, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. Two types of single spoke resonators will be utilized for beam-acceleration in the low energy part of the Project X linac. SSR1 and SSR2 operate at 325 MHz and at an optimal beta of 0.22 and 0.51 respectively. After the initial phase of prototyping, a production run of 10 SSR1 resonators was recently completed in US industry. The qualification of this group of resonators in the Fermilab VTS is proceeding successfully and nearly complete. The first qualified resonator has been outfitted with a Stainless Steel helium vessel. Preliminary test results for the first jacketed SSR1 are presented. The first RF power couplers were ordered, the design of the double-lever tuning mechanism is almost complete.
	Slides FRIOB02 [8.800 MB]