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SRF2003 Show Abstract

Title Development of a Niobium Bellow for Beamline Connections
Type Poster materials / surface effects
Abstract Superconducting cavities in an accelerator assembly are usually connected at thebeampipes with stainless steel bellows at an intermediate temperature, which compensate for alignment tolerances on the cavity beamlines and for thermal contraction during cooldown to cryogenic temperatures. This transition from one cavity to the next in a cavity string is typically of the order of 3/2 lambda long with approximately 1/2 lambda taken up by the bellow. If one would incorporate a niobium bellow in the beam pipe, this distance could be reduced by half a wave length. In the case of an accelerator such as TESLA the overall cavity length for the accelerator could be reduced by roughly 10 % or 2000 m. In terms of cost savings this would amount to 20 - 30 Million Dollars.   Based on this estimate we have started to develop a niobium bellow to be used on a 2.75 inch diameter beamline. It is made from 0.3 mm thick niobium sheet, which has been rolled into a tube and completed by a longitudinal full penetration electron beam weld; the weld is made with a narrow, focused beam to reduce the heat affected zone and therefore limit the grain growth, which could affect the formability. Subsequently, two convolutions have been pressed into this tube in a 2-stage process, using an external die and a polyurethane internal expander. Niobium cuffs and flanges were electron beam welded to the formed bellow, which then makes leak testing possible and allows some measurements of compression/expansion and bending. In this contribution the fabrication process and the subsequent mechanical and vacuum tests with the bellows will be described.

List of authors...

Principle author first.

Last (Family) Name First Name (Initials only) Affiliation or Organization (abbreviations if possible)
Turlington L. JLAB
Brawley J. JLAB
Manus B. JLAB
Manning S. JLAB
Morgan S. JLAB
Slack G. JLAB
Kneisel P. JLAB

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