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Title: Impact of remanent magnetic field on the heat load of original CEBAF cryomodule

The heat load of the original cryomodules for the CEBAF accelerator is ~50% higher than the target value of 100 W at 2.07 K for refurbished cavities operating at an accelerating gradient of 12.5 MV/m. This issue is due to the quality factor of the cavities being ~50% lower in the cryomodule than when tested in a vertical cryostat, even at low RF field. Previous studies were not conclusive about the origin of the additional losses. We present the results of a systematic study of the additional losses in a five-cell cavity from a decommissioned cryomodule after attaching components, which are part of the cryomodule, such as the cold tuner, the He tank and the cold magnetic shield, prior to cryogenic testing in a vertical cryostat. Flux-gate magnetometers and temperature sensors are used as diagnostic elements. Different cool-down procedures and tests in different residual magnetic fields were investigated during the study. Here, three flux-gate magnetometers attached to one of the cavities installed in the refurbished cryomodule C50-12 confirmed the hypothesis of high residual magnetic field as a major cause for the increased RF losses.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
Report Number(s):
JLAB-ACC-16-2339; DOE/OR/23177-3942
Journal ID: ISSN 1051-8223; TRN: US1701227
Grant/Contract Number:
AC05-06OR23177
Type:
Accepted Manuscript
Journal Name:
IEEE Transactions on Applied Superconductivity
Additional Journal Information:
Journal Volume: 27; Journal Issue: 4; Journal ID: ISSN 1051-8223
Publisher:
Institute of Electrical and Electronics Engineers (IEEE)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; superconducting resonators; cryomodules; magnetic remanence; niobium
OSTI Identifier:
1338913

Ciovati, Gianluigi, Cheng, Guangfeng, Drury, Michael, Fischer, John, and Geng, Rongli. Impact of remanent magnetic field on the heat load of original CEBAF cryomodule. United States: N. p., Web. doi:10.1109/TASC.2016.2631938.
Ciovati, Gianluigi, Cheng, Guangfeng, Drury, Michael, Fischer, John, & Geng, Rongli. Impact of remanent magnetic field on the heat load of original CEBAF cryomodule. United States. doi:10.1109/TASC.2016.2631938.
Ciovati, Gianluigi, Cheng, Guangfeng, Drury, Michael, Fischer, John, and Geng, Rongli. 2016. "Impact of remanent magnetic field on the heat load of original CEBAF cryomodule". United States. doi:10.1109/TASC.2016.2631938. https://www.osti.gov/servlets/purl/1338913.
@article{osti_1338913,
title = {Impact of remanent magnetic field on the heat load of original CEBAF cryomodule},
author = {Ciovati, Gianluigi and Cheng, Guangfeng and Drury, Michael and Fischer, John and Geng, Rongli},
abstractNote = {The heat load of the original cryomodules for the CEBAF accelerator is ~50% higher than the target value of 100 W at 2.07 K for refurbished cavities operating at an accelerating gradient of 12.5 MV/m. This issue is due to the quality factor of the cavities being ~50% lower in the cryomodule than when tested in a vertical cryostat, even at low RF field. Previous studies were not conclusive about the origin of the additional losses. We present the results of a systematic study of the additional losses in a five-cell cavity from a decommissioned cryomodule after attaching components, which are part of the cryomodule, such as the cold tuner, the He tank and the cold magnetic shield, prior to cryogenic testing in a vertical cryostat. Flux-gate magnetometers and temperature sensors are used as diagnostic elements. Different cool-down procedures and tests in different residual magnetic fields were investigated during the study. Here, three flux-gate magnetometers attached to one of the cavities installed in the refurbished cryomodule C50-12 confirmed the hypothesis of high residual magnetic field as a major cause for the increased RF losses.},
doi = {10.1109/TASC.2016.2631938},
journal = {IEEE Transactions on Applied Superconductivity},
number = 4,
volume = 27,
place = {United States},
year = {2016},
month = {11}
}