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Title: Decrease of the surface resistance in superconducting niobium resonator cavities by the microwave field

Measurements of the quality factor, Q, of Nb superconducting microwave resonators often show that Q increases by {approx_equal} 10%–30% with increasing radio-frequency (rf) field, H, up to {approx} 15-20 mT. Recent high temperature heat treatments can amplify this rf field-induced increase of Q up to {approx_equal} 50%–100% and extend it to much higher fields, but the mechanisms of the enhancement of Q(H) remain unclear. Here, we suggest a method to reveal these mechanisms by measuring temperature dependencies of Q at different rf field amplitudes. We show that the increase of Q(H) does not come from a field dependent quasi-particles activation energy or residual resistance, but rather results from the smearing of the density of state by the rf field.
Authors:
 [1] ;  [1] ;  [2]
  1. Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
  2. Old Dominion University, Norfolk, VA (United States)
Publication Date:
OSTI Identifier:
1126864
Report Number(s):
JLAB-ACC--14-1849; DOE/OR/23177-3010
Journal ID: ISSN 0003-6951; DE-SC0010081; TRN: US1400275
DOE Contract Number:
AC05-06OR23177
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 09
Publisher:
American Institute of Physics (AIP)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC) (United States)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY