SRF2011 - List of Authors (Ozelis, J.P.)

Paper

Title

Page

Gradient R&D in the US

625

J.P. Ozelis
Fermilab, Batavia, USA

Funding: cOperated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Over the past few years, significant effort has been made to systematically improve multi-cell cavity accelerating gradients, driven in large part by the requirements of the ILC, for which the reproducible achievement of high gradients is a prerequisite. Substantial progress has been made by teams at Cornell University, Fermilab, and Jefferson Lab, in pushing gradients to higher values and in achieving this performance on a more regular basis. Development of improved diagnostic/inspection techniques along with the utilization of both localized and global repair tools have helped enable this improvement. Likewise, processing and assembly procedures that led to a lower incidence of field emission have facilitated this progress. The present status of cavity performance will be presented along with its evolution, and examples of the role the aforementioned techniques and tools have played in achieving this performance.

Slides THIOA02 [0.870 MB]

THIOA07

Single-cell SC Cavity Development in India

659

A. Puntambekar, J. Dwivedi, P.D. Gupta, S.C. Joshi, G. Mundra, P. Shrivastava
RRCAT, Indore (M.P.), India
C.A. Cooper, M.H. Foley, T.N. Khabiboulline, C.S. Mishra, J.P. Ozelis, A.M. Rowe
Fermilab, Batavia, USA
P.N. Potukuchi
IUAC, New Delhi, India
G. Wu
ANL, Argonne, USA

Under Indian Institutions and Fermilab Collaboration (IIFC), Raja Ramanna Centre for Advanced Technology (RRCAT) Indore, India has initiated the development of SCRF cavity technology in collaboration with Fermi National Accelerator Laboratory (FNAL) USA. The R & D efforts are focused on the proposed Project-X accelerator complex at FNAL and High Intensity Proton Accelerator activities in India. As an initial effort, two prototype 1.3 GHz single cell bulk niobium cavities have been developed in collaboration with the Inter University Accelerator Centre (IUAC), New Delhi. Learning from the experience gained and the initial results of these prototypes (achieving Eacc ~23 MV/m), two more improved 1.3 GHz single cell cavities are being developed. These two improved single cell cavities will also be processed and tested at FNAL. Development of a 1.3 GHz, 5-cell SCRF cavity with simple end groups, development of end group, and fabrication of a single -cell 650 MHz (β=0.9) prototype cavity are being undertaken as the next stage in these efforts. This paper will present the development and test results on the 1.3 GHz single cell cavities and status of the ongoing work.

Slides THIOA07 [2.937 MB]

THPO015

Repair SRFCavity by Re-Melting Surface Defects via High Power Laser Technique

740

G.M. Ge
CLASSE, Ithaca, New York, USA
E. Borissov, L.D. Cooley, D.T. Hicks, T.H. Nicol, J.P. Ozelis, J. Ruan, D.A. Sergatskov
Fermilab, Batavia, USA
G. Wu
ANL, Argonne, USA

As the field emission is gradually under control in recent SRF activities, cavity performance is limited by hard quench in the most case. Surface defect has been identified as one of main reasons caused cavity quench scattering cavity accelerating gradient from 12 MV/m to 40 MV/m. Laser processing is able to re-shape the steep flaws to be flat and smooth surface. In Fermilab, a sophisticated laser repair system has been built for 1.3GHz low performance SRF cavity which is limited by surface defect. The pit in a 1.3GHz single-cell cavity was re-melted by high power laser pulse, cavity took 30 μm light Electropolishing after that. The gradient achieved 39MV/m in initial run; after another 30 μm Electropolishing, it achieved 40 MV/m. The improved laser repair system is able to re-melt the surface defect in one meter long 9-cell SRF cavity. It successfully re-melted a pit in 9-cell SRF cavity TB9ACC017.

THPO023

External Magnetic Fields and Operating SRF Cavity

763

D.A. Sergatskov, T.N. Khabiboulline, R.L. Madrak, J.P. Ozelis, I. Terechkine
Fermilab, Batavia, USA

Funding: The work herein has been performed at Fermilab, which is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
When an SRF cavity is undergoing a transition to the superconducting state in an external magnetic field it traps some of the flux which results in an increase of surface resistance. This effect was extensively studied, is well understood by now and results in stringent requirements for an ambient magnetic field on the surface of an SRF cavity. The situation is quite different when magnetic field is applied to a cavity already in the superconducting state. During normal operation the bulk of the superconducting Nb should protect the RF surface of the cavity from fields on the outside. So we expect that the requirements on an external magnetic field applied to an operating cavity could be significantly relaxed. One possible failure mode is when the cavity quenches while the external field is applied. The magnetic field would penetrate through a normal zone formed during the quench and can get trapped during the subsequent post-quench cooling. We studied the effects of an external magnetic field applied to an operating SRF cavity and report the results.

Poster THPO023 [1.370 MB]

Paper	Title	Page
THIOA02	Gradient R&D in the US	625
	J.P. Ozelis Fermilab, Batavia, USA
	Funding: cOperated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Over the past few years, significant effort has been made to systematically improve multi-cell cavity accelerating gradients, driven in large part by the requirements of the ILC, for which the reproducible achievement of high gradients is a prerequisite. Substantial progress has been made by teams at Cornell University, Fermilab, and Jefferson Lab, in pushing gradients to higher values and in achieving this performance on a more regular basis. Development of improved diagnostic/inspection techniques along with the utilization of both localized and global repair tools have helped enable this improvement. Likewise, processing and assembly procedures that led to a lower incidence of field emission have facilitated this progress. The present status of cavity performance will be presented along with its evolution, and examples of the role the aforementioned techniques and tools have played in achieving this performance.
	Slides THIOA02 [0.870 MB]

THIOA07	Single-cell SC Cavity Development in India	659
	A. Puntambekar, J. Dwivedi, P.D. Gupta, S.C. Joshi, G. Mundra, P. Shrivastava RRCAT, Indore (M.P.), India C.A. Cooper, M.H. Foley, T.N. Khabiboulline, C.S. Mishra, J.P. Ozelis, A.M. Rowe Fermilab, Batavia, USA P.N. Potukuchi IUAC, New Delhi, India G. Wu ANL, Argonne, USA
	Under Indian Institutions and Fermilab Collaboration (IIFC), Raja Ramanna Centre for Advanced Technology (RRCAT) Indore, India has initiated the development of SCRF cavity technology in collaboration with Fermi National Accelerator Laboratory (FNAL) USA. The R & D efforts are focused on the proposed Project-X accelerator complex at FNAL and High Intensity Proton Accelerator activities in India. As an initial effort, two prototype 1.3 GHz single cell bulk niobium cavities have been developed in collaboration with the Inter University Accelerator Centre (IUAC), New Delhi. Learning from the experience gained and the initial results of these prototypes (achieving Eacc ~23 MV/m), two more improved 1.3 GHz single cell cavities are being developed. These two improved single cell cavities will also be processed and tested at FNAL. Development of a 1.3 GHz, 5-cell SCRF cavity with simple end groups, development of end group, and fabrication of a single -cell 650 MHz (β=0.9) prototype cavity are being undertaken as the next stage in these efforts. This paper will present the development and test results on the 1.3 GHz single cell cavities and status of the ongoing work.
	Slides THIOA07 [2.937 MB]

THPO015	Repair SRFCavity by Re-Melting Surface Defects via High Power Laser Technique	740
	G.M. Ge CLASSE, Ithaca, New York, USA E. Borissov, L.D. Cooley, D.T. Hicks, T.H. Nicol, J.P. Ozelis, J. Ruan, D.A. Sergatskov Fermilab, Batavia, USA G. Wu ANL, Argonne, USA
	As the field emission is gradually under control in recent SRF activities, cavity performance is limited by hard quench in the most case. Surface defect has been identified as one of main reasons caused cavity quench scattering cavity accelerating gradient from 12 MV/m to 40 MV/m. Laser processing is able to re-shape the steep flaws to be flat and smooth surface. In Fermilab, a sophisticated laser repair system has been built for 1.3GHz low performance SRF cavity which is limited by surface defect. The pit in a 1.3GHz single-cell cavity was re-melted by high power laser pulse, cavity took 30 μm light Electropolishing after that. The gradient achieved 39MV/m in initial run; after another 30 μm Electropolishing, it achieved 40 MV/m. The improved laser repair system is able to re-melt the surface defect in one meter long 9-cell SRF cavity. It successfully re-melted a pit in 9-cell SRF cavity TB9ACC017.

THPO023	External Magnetic Fields and Operating SRF Cavity	763
	D.A. Sergatskov, T.N. Khabiboulline, R.L. Madrak, J.P. Ozelis, I. Terechkine Fermilab, Batavia, USA
	Funding: The work herein has been performed at Fermilab, which is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. When an SRF cavity is undergoing a transition to the superconducting state in an external magnetic field it traps some of the flux which results in an increase of surface resistance. This effect was extensively studied, is well understood by now and results in stringent requirements for an ambient magnetic field on the surface of an SRF cavity. The situation is quite different when magnetic field is applied to a cavity already in the superconducting state. During normal operation the bulk of the superconducting Nb should protect the RF surface of the cavity from fields on the outside. So we expect that the requirements on an external magnetic field applied to an operating cavity could be significantly relaxed. One possible failure mode is when the cavity quenches while the external field is applied. The magnetic field would penetrate through a normal zone formed during the quench and can get trapped during the subsequent post-quench cooling. We studied the effects of an external magnetic field applied to an operating SRF cavity and report the results.
	Poster THPO023 [1.370 MB]