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Title: Quench Studies of Six High Temperature Nitrogen Doped 9 Cell Cavities for Use in the LCLS-II Baseline Prototype Cryomodule at Jefferson Laboratory

Jefferson Lab (JLab) processed six nine-cell cavities as part of a small-scale production for LCLS-II cavity processing development utilizing the promising nitrogen-doping process. Various nitrogen-doping recipes have been scrutinized to optimize process parameters with the aim to guarantee an unloaded quality factor (Q_0) of 2.7∙1010 at an accelerating field (Eacc) of 16 MV/m at 2.0 K in the cryomodule. During the R&D phase the characteristic Q0 vs. Eacc performance curve of the cavities has been measured in JLab’s vertical test area at 2 K. The findings showed the characteristic rise of the Q0 with Eacc as expected from nitrogen-doping. Initially, five cavities achieved an average Q0 of 3.3·1010 at the limiting Eacc averaging to 16.8 MV/m, while one cavity experienced an early quench accompanied by an unusual Q_0 vs. Eacc curve. The project accounts for a cavity performance loss from the vertical dewar test (with or without the helium vessel) to the horizontal performance in a cryomodule, such that these results leave no save margin to the cryomodule specification. Consequently, a refinement of the nitrogen-doping has been initiated to guarantee an average quench field above 20 MV/m without impeding the Q_0. This paper covers the refinement work performed for eachmore » cavity, which depends on the initial results, as well as a quench analysis carried out before and after the rework during the vertical RF tests as far as applicable.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1]
  1. Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Publication Date:
OSTI Identifier:
1223383
Report Number(s):
JLAB-ACC--15-2084; DOE/OR/23177--3419
TRN: US1601421
DOE Contract Number:
AC05-06OR23177
Resource Type:
Conference
Resource Relation:
Conference: IPAC 2015, Richmond, VA (United States), 3-5 May 2015
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; CEBAF ACCELERATOR; NITROGEN; SUPERCONDUCTING CAVITY RESONATORS; TEMPERATURE RANGE 0000-0013 K; DOPED MATERIALS; PERFORMANCE TESTING; QUALITY FACTOR; LOSSES; SPECIFICATIONS