SRF2013 - List of Authors (Crawford, A.C.)

Paper

Title

Page

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.

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.

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.

TUP055

Electropolishing of the ANL Deflecting Cavity for the APS Upgrade

544

Y. Yang, J.D. Fuerst, J.P. Holzbauer, J.A. Kaluzny, A. Nassiri, G. Wu
ANL, Argonne, USA
A.C. Crawford
Fermilab, Batavia, USA
P. Dhakal, J.D. Mammosser, H. Wang
JLAB, Newport News, Virginia, USA
Y. Yang
TUB, Beijing, People's Republic of China

Studies on the application of electropolishing (EP) of the ANL superconducting deflecting cavity have shown promising results. This cavity geometry is a squashed single-cell cavity with Y-end group waveguide as well as on-cell LOM damper. The cavity works at TM110-like deflecting mode, in which the iris between the cavity cell and the Y-end group is the highest magnetic field region. Before EP, the cavity had been chemically etched (BCP) several times. Forty-um EP processing was performed on one Mark II prototype deflecting cavity at Fermilab. No mild baking was performed before the cavity vertical test. The test showed that the low-field Q had improved from 2·10⁹ to 3·10⁹ and the high-field Q-slope had been successfully removed. The quench limit was slightly improved from 10⁶ mT to 113 mT. Fast T-mapping had detected a significant decrease of local temperature rise in the cavity iris. Optical inspection before EP found a lot of grooves around the iris, which might be related to the gas bubbles generated during BCP. This suggests that horizontal EP is a promising processing technique to remove the high-field Q-slope and improve the deflecting cavity performance.

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.

Paper	Title	Page
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.

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.

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.

TUP055	Electropolishing of the ANL Deflecting Cavity for the APS Upgrade	544
	Y. Yang, J.D. Fuerst, J.P. Holzbauer, J.A. Kaluzny, A. Nassiri, G. Wu ANL, Argonne, USA A.C. Crawford Fermilab, Batavia, USA P. Dhakal, J.D. Mammosser, H. Wang JLAB, Newport News, Virginia, USA Y. Yang TUB, Beijing, People's Republic of China
	Studies on the application of electropolishing (EP) of the ANL superconducting deflecting cavity have shown promising results. This cavity geometry is a squashed single-cell cavity with Y-end group waveguide as well as on-cell LOM damper. The cavity works at TM110-like deflecting mode, in which the iris between the cavity cell and the Y-end group is the highest magnetic field region. Before EP, the cavity had been chemically etched (BCP) several times. Forty-um EP processing was performed on one Mark II prototype deflecting cavity at Fermilab. No mild baking was performed before the cavity vertical test. The test showed that the low-field Q had improved from 2·10⁹ to 3·10⁹ and the high-field Q-slope had been successfully removed. The quench limit was slightly improved from 10⁶ mT to 113 mT. Fast T-mapping had detected a significant decrease of local temperature rise in the cavity iris. Optical inspection before EP found a lot of grooves around the iris, which might be related to the gas bubbles generated during BCP. This suggests that horizontal EP is a promising processing technique to remove the high-field Q-slope and improve the deflecting cavity performance.

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.