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Title: High field Q slope and the baking effect: Review of recent experimental results and new data on Nb heat treatments

Here, the performance of superconducting radio-frequency (SRF) cavities made of bulk Nb at high fields (peak surface magnetic field greater than about 90 mT) is characterized by exponentially increasing rf losses (high-field Q-slope), in the absence of field emission, which are often mitigated by low temperature (100-140 °C, 12-48 h) baking. In this contribution, recent experimental results and phenomenological models to explain this effect will be briefly reviewed. New experimental results on the high-field Q-slope will be presented for cavities that had been heat treated in a vacuum furnace at high temperature without subsequent chemical etching. These studies are aimed at understanding the role of hydrogen on the high-field Q-slope and at the passivation of the Nb surface during heat treatment. Improvement of the cavity performances, particularly of the cavities’ quality factor, have been obtained following the high temperature heat-treatments, while SIMS surface analysis measurements on Nb samples treated with the cavities revealed significantly lower hydrogen concentration than for samples that followed standard cavity treatments.
Authors:
;  [1] ;  [2] ;  [2] ;  [2]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  2. North Carolina State Univ., Raleigh, NC (United States)
Publication Date:
OSTI Identifier:
1021722
Report Number(s):
JLAB-ACC--10-1204; DOE/OR/23177--1255
Journal ID: ISSN 1098-4402; TRN: US201117%%312
Grant/Contract Number:
AC05-06OR23177
Type:
Accepted Manuscript
Journal Name:
Physical Review Special Topics. Accelerators and Beams
Additional Journal Information:
Journal Volume: 13; Journal Issue: 02; Journal ID: ISSN 1098-4402
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 36 MATERIALS SCIENCE; BAKING; CAVITIES; ETCHING; FIELD EMISSION; HEAT TREATMENTS; HYDROGEN; MAGNETIC FIELDS; PASSIVATION; PERFORMANCE; QUALITY FACTOR; VACUUM FURNACES