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Title: Measurement of the high-field Q drop in the TM010 and TE011 modes in a niobium cavity

Abstract

In the last few years superconducting radio-frequency (rf) cavities made of high-purity (residual resistivity ratio>200) niobium achieved accelerating gradients close to the theoretical limits. An obstacle towards achieving reproducibly higher fields is represented by ''anomalous'' losses causing a sharp degradation of the cavity quality factor when the peak surface magnetic field (Bp) is above about 90 mT, in the absence of field emission. This effect, called ''Q drop'' has been measured in many laboratories with single- and multicell cavities mainly in the gigahertz range. In addition, a low-temperature (100-140 C) ''in situ'' baking of the cavity was found to be beneficial in reducing the Q drop. In order to gain some understanding of the nature of these losses, a single-cell cavity has been tested in the TM010 and TE011 modes at 2 K. The feature of the TE011 mode is to have zero electric field on the cavity surface, so that electric field effects can be excluded as a source for the Q drop. This article will present some of the experimental results for different cavity treatments and will compare them with existing models.

Authors:
;
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA
Sponsoring Org.:
USDOE - Office of Energy Research (ER)
OSTI Identifier:
885348
Report Number(s):
JLAB-ACP-06-478; DOE/ER/40150-3958
Journal ID: ISSN 1098-4402; TRN: US0603821
DOE Contract Number:  
AC05-84ER40150
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Special Topics. Accelerators and Beams; Journal Volume: 9
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; SUPERCONDUCTING CAVITY RESONATORS; ELECTRIC FIELDS; FIELD EMISSION; MAGNETIC FIELDS; NIOBIUM; QUALITY FACTOR; PERFORMANCE

Citation Formats

Gianluigi Ciovati, and Peter Kneisel. Measurement of the high-field Q drop in the TM010 and TE011 modes in a niobium cavity. United States: N. p., 2006. Web. doi:10.1103/PhysRevSTAB.9.042001.
Gianluigi Ciovati, & Peter Kneisel. Measurement of the high-field Q drop in the TM010 and TE011 modes in a niobium cavity. United States. doi:10.1103/PhysRevSTAB.9.042001.
Gianluigi Ciovati, and Peter Kneisel. Sat . "Measurement of the high-field Q drop in the TM010 and TE011 modes in a niobium cavity". United States. doi:10.1103/PhysRevSTAB.9.042001. https://www.osti.gov/servlets/purl/885348.
@article{osti_885348,
title = {Measurement of the high-field Q drop in the TM010 and TE011 modes in a niobium cavity},
author = {Gianluigi Ciovati and Peter Kneisel},
abstractNote = {In the last few years superconducting radio-frequency (rf) cavities made of high-purity (residual resistivity ratio>200) niobium achieved accelerating gradients close to the theoretical limits. An obstacle towards achieving reproducibly higher fields is represented by ''anomalous'' losses causing a sharp degradation of the cavity quality factor when the peak surface magnetic field (Bp) is above about 90 mT, in the absence of field emission. This effect, called ''Q drop'' has been measured in many laboratories with single- and multicell cavities mainly in the gigahertz range. In addition, a low-temperature (100-140 C) ''in situ'' baking of the cavity was found to be beneficial in reducing the Q drop. In order to gain some understanding of the nature of these losses, a single-cell cavity has been tested in the TM010 and TE011 modes at 2 K. The feature of the TE011 mode is to have zero electric field on the cavity surface, so that electric field effects can be excluded as a source for the Q drop. This article will present some of the experimental results for different cavity treatments and will compare them with existing models.},
doi = {10.1103/PhysRevSTAB.9.042001},
journal = {Physical Review Special Topics. Accelerators and Beams},
number = ,
volume = 9,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 2006},
month = {Sat Apr 01 00:00:00 EST 2006}
}