2011 Particle Accelerator Conference - Table of Session: THOCS (Accelerator Technology VI)

Paper

Title

Page

Would >50 MV/m be Possible with Superconducting RF Cavities?

2119

T. Tajima
LANL, Los Alamos, New Mexico, USA

Several laboratories are working on the development of thin-film superconductor technology to overcome the fundamental limit of ~50 MV/m accelerating gradient with niobium SRF cavities. Efforts at LANL attempt to enhance the sustainable surface magnetic field by coating thin layers of superconductors, such as MgB2 on top of niobium. The coating techniques being developed and the results of RF critical field and surface resistance measurements that were obtained in collaboration with other national laboratories, universities and industry will be presented.

Slides THOCS1 [0.751 MB]

THOCS2

SRF Materials R&D

L.D. Cooley
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The push for higher yield of high-gradient SRF cavities has recently received support from a nationwide multi-disciplinary program to understand limitations of superconducting cavities and improve their fabrication and processing. Materials science has revealed deeper understanding of how oxidation, cold work, hydrogen, and roughness affect both fundamental behavior as well as real performance after different processing stages. Processing advances, such as optical inspection, laser re-melting, tumbling, and atomic layer deposition, provide opportunities to optimize the technology, benefiting the design of future SRF-based accelerators such as ILC or Project X.

Slides THOCS2 [4.470 MB]

THOCS3

R&D Status for In-Situ Plasma Surface Cleaning of SRF Cavities at Spallation Neutron Source

2124

S.-H. Kim, M.T. Crofford
ORNL, Oak Ridge, Tennessee, USA
M. Doleans
NSCL, East Lansing, Michigan, USA
J.D. Mammosser
JLAB, Newport News, Virginia, USA
J. Saunders
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The SNS SCL is reliably operating at 0.93 GeV output energy with an energy reserve of 10MeV with high availability. Most of the cavities exhibit field emission, which directly or indirectly (through heating of end groups) limits the gradients achievable in the high beta cavities in normal operation with the beam. One of the field emission sources would be surface contaminations during surface processing for which mild surface cleaning, if any, will help in reducing field emission. An R&D effort is in progress to develop in-situ surface processing for the cryomodules in the tunnel without disassembly. As the first attempt, in-situ plasma processing has been applied to the CM12 in the SNS SRF facility after the repair work with a promising result. This paper will report the R&D status of plasma processing in the SNS.

Slides THOCS3 [3.294 MB]

THOCS4

RF Power Upgrade for CEBAF at Jefferson Laboratory

2127

A.J. Kimber, R.M. Nelson
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Jefferson Laboratory (JLab) is currently upgrading the 6GeV Continuous Electron Beam Accelerator Facility (CEBAF) to 12GeV. As part of the upgrade, RF systems will be added, bringing the total from 340 to 420. Existing RF systems can provide up to 6.5 kW of CW RF at 1497 MHZ. The 80 new systems will provide increased RF power of up to 13 kW CW each. Built around a newly designed and higher efficiency 13 kW klystron developed for JLab by L-3 Communications, each new RF chain is a completely revamped system using hardware different than our present installations. This paper will discuss the main components of the new systems including the 13 kW klystron, waveguide isolator, and HV power supply using switch-mode technology. Methodology for selection of the various components and results of initial testing will also be addressed.

Slides THOCS4 [3.364 MB]

THOCS5

Resonance Control in SRF Cavities at FNAL

2130

Y.M. Pischalnikov, W. Schappert
Fermilab, Batavia, USA
M. Scorrano
INFN-Pisa, Pisa, Italy

Funding: Work is supported by the U.S. Department of Energy
An adaptive Least Squares algorithm to control Lorentz force detuning in SRF cavities has been developed and tested in the HTS at FNAL. During open-loop tests in the FNAL HTS, the algorithm was able to reduce LFD in a 9-cell 1.3 GHz elliptical cavity operating at 35 MV/m from 600 Hz to less than 10 Hz during both the fill and the flattop. The algorithm was also able to adapt to changes in the gradient of the cavity and to changes in the pulse length.

Slides THOCS5 [3.572 MB]

THOCS6

Progress in Cavity and Cryomodule Design for the Project X Linac

2133

M.S. Champion, S. Barbanotti, M.H. Foley, C.M. Ginsburg, I.G. Gonin, C.J. Grimm, J.S. Kerby, S. Nagaitsev, T.H. Nicol, T.J. Peterson, L. Ristori, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, USA

The continuous wave 3 GeV Project X Linac requires the development of two families of cavities and cryomodules at 325 and 650 MHz. The baseline design calls for three types of superconducting single-spoke resonators at 325 MHz having betas of 0.11, 0.22, and 0.42 and two types of superconducting five-cell elliptical cavities having betas of 0.61 and 0.9. These cavities shall accelerate a 1 mA H⁻ beam initially and must support eventual operation at 4 mA. The electromagnetic and mechanical designs of the cavities are in progress and acquisition of prototypes is planned. The heat load to the cryogenic system is up to 25 W per cavity in the 650 MHz section, thus segmentation of the cryogenic system is a major issue in the cryomodule design. Designs for the two families of cryomodules are underway.

Slides THOCS6 [2.241 MB]

Paper	Title	Page
THOCS1	Would >50 MV/m be Possible with Superconducting RF Cavities?	2119
	T. Tajima LANL, Los Alamos, New Mexico, USA
	Several laboratories are working on the development of thin-film superconductor technology to overcome the fundamental limit of ~50 MV/m accelerating gradient with niobium SRF cavities. Efforts at LANL attempt to enhance the sustainable surface magnetic field by coating thin layers of superconductors, such as MgB2 on top of niobium. The coating techniques being developed and the results of RF critical field and surface resistance measurements that were obtained in collaboration with other national laboratories, universities and industry will be presented.
	Slides THOCS1 [0.751 MB]

THOCS2	SRF Materials R&D
	L.D. Cooley Fermilab, Batavia, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The push for higher yield of high-gradient SRF cavities has recently received support from a nationwide multi-disciplinary program to understand limitations of superconducting cavities and improve their fabrication and processing. Materials science has revealed deeper understanding of how oxidation, cold work, hydrogen, and roughness affect both fundamental behavior as well as real performance after different processing stages. Processing advances, such as optical inspection, laser re-melting, tumbling, and atomic layer deposition, provide opportunities to optimize the technology, benefiting the design of future SRF-based accelerators such as ILC or Project X.
	Slides THOCS2 [4.470 MB]

THOCS3	R&D Status for In-Situ Plasma Surface Cleaning of SRF Cavities at Spallation Neutron Source	2124
	S.-H. Kim, M.T. Crofford ORNL, Oak Ridge, Tennessee, USA M. Doleans NSCL, East Lansing, Michigan, USA J.D. Mammosser JLAB, Newport News, Virginia, USA J. Saunders ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. The SNS SCL is reliably operating at 0.93 GeV output energy with an energy reserve of 10MeV with high availability. Most of the cavities exhibit field emission, which directly or indirectly (through heating of end groups) limits the gradients achievable in the high beta cavities in normal operation with the beam. One of the field emission sources would be surface contaminations during surface processing for which mild surface cleaning, if any, will help in reducing field emission. An R&D effort is in progress to develop in-situ surface processing for the cryomodules in the tunnel without disassembly. As the first attempt, in-situ plasma processing has been applied to the CM12 in the SNS SRF facility after the repair work with a promising result. This paper will report the R&D status of plasma processing in the SNS.
	Slides THOCS3 [3.294 MB]

THOCS4	RF Power Upgrade for CEBAF at Jefferson Laboratory	2127
	A.J. Kimber, R.M. Nelson JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Jefferson Laboratory (JLab) is currently upgrading the 6GeV Continuous Electron Beam Accelerator Facility (CEBAF) to 12GeV. As part of the upgrade, RF systems will be added, bringing the total from 340 to 420. Existing RF systems can provide up to 6.5 kW of CW RF at 1497 MHZ. The 80 new systems will provide increased RF power of up to 13 kW CW each. Built around a newly designed and higher efficiency 13 kW klystron developed for JLab by L-3 Communications, each new RF chain is a completely revamped system using hardware different than our present installations. This paper will discuss the main components of the new systems including the 13 kW klystron, waveguide isolator, and HV power supply using switch-mode technology. Methodology for selection of the various components and results of initial testing will also be addressed.
	Slides THOCS4 [3.364 MB]

THOCS5	Resonance Control in SRF Cavities at FNAL	2130
	Y.M. Pischalnikov, W. Schappert Fermilab, Batavia, USA M. Scorrano INFN-Pisa, Pisa, Italy
	Funding: Work is supported by the U.S. Department of Energy An adaptive Least Squares algorithm to control Lorentz force detuning in SRF cavities has been developed and tested in the HTS at FNAL. During open-loop tests in the FNAL HTS, the algorithm was able to reduce LFD in a 9-cell 1.3 GHz elliptical cavity operating at 35 MV/m from 600 Hz to less than 10 Hz during both the fill and the flattop. The algorithm was also able to adapt to changes in the gradient of the cavity and to changes in the pulse length.
	Slides THOCS5 [3.572 MB]

THOCS6	Progress in Cavity and Cryomodule Design for the Project X Linac	2133
	M.S. Champion, S. Barbanotti, M.H. Foley, C.M. Ginsburg, I.G. Gonin, C.J. Grimm, J.S. Kerby, S. Nagaitsev, T.H. Nicol, T.J. Peterson, L. Ristori, N. Solyak, V.P. Yakovlev Fermilab, Batavia, USA
	The continuous wave 3 GeV Project X Linac requires the development of two families of cavities and cryomodules at 325 and 650 MHz. The baseline design calls for three types of superconducting single-spoke resonators at 325 MHz having betas of 0.11, 0.22, and 0.42 and two types of superconducting five-cell elliptical cavities having betas of 0.61 and 0.9. These cavities shall accelerate a 1 mA H⁻ beam initially and must support eventual operation at 4 mA. The electromagnetic and mechanical designs of the cavities are in progress and acquisition of prototypes is planned. The heat load to the cryogenic system is up to 25 W per cavity in the 650 MHz section, thus segmentation of the cryogenic system is a major issue in the cryomodule design. Designs for the two families of cryomodules are underway.
	Slides THOCS6 [2.241 MB]