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Title: Surface processing for bulk niobium superconducting radio frequency cavities

The majority of niobium cavities for superconducting particle accelerators continue to be fabricated from thin-walled (2-4mm) polycrystalline niobium sheet and, as a final step, require material removal from the radio frequency (RF) surface in order to achieve performance needed for use as practical accelerator devices. More recently bulk niobium in the form of, single-or large-grain slices cut from an ingot has become a viable alternative for some cavity types. In both cases the so-called damaged layer must be chemically etched or electrochemically polished away. The methods for doing this date back at least four decades, however, vigorous empirical studies on real cavities and more fundamental studies on niobium samples at laboratories worldwide have led to seemingly modest improvements that, when taken together, constitute a substantial advance in the reproducibility for surface processing techniques and overall cavity performance. This article reviews the development of niobium cavity surface processing, and summarizes results of recent studies. We place some emphasis on practical details for real cavity processing systems which are difficult to find in the literature but are, nonetheless, crucial for achieving the good and reproducible cavity performance. New approaches for bulk niobium surface treatment which aim to reduce cost or increase performance,more » including alternate chemical recipes, barrel polishing and 'nitrogen doping' of the RF surface, continue to be pursued and are closely linked to the requirements for surface processing.« less
Authors:
 [1] ;  [1]
  1. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; AC52-07NA27344; FG02-94ER40834; FG02-08ER41556
Type:
Accepted Manuscript
Journal Name:
Superconductor Science and Technology
Additional Journal Information:
Journal Volume: 30; Journal Issue: 4; Journal ID: ISSN 0953-2048
Publisher:
IOP Publishing
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; niobium RF cavities; surface processing; electropolishing; chemical polishing
OSTI Identifier:
1368074