Development of a Niobium Bellow for Beamline Connections

Conference · Mon Sep 01 04:00:00 EDT 2003

OSTI ID:822206

Turlington, Larry; Brawley, John; Manus, Robert; Manning, Stephen; Morgan, Samuel; Slack, Gary; Kneisel, Peter

Superconducting cavities in an accelerator assembly are usually connected at the beampipes by stainless steel bellows. They operate at an intermediate temperature, compensating 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 wavelength along with approximately half a wavelength taken up by the bellows. If one could incorporate a niobium bellows in the beam pipe, this distance could be reduced by half a wave length. In the case of a big 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 several million dollars. Based on this estimate we have begun to develop a niobium bellows to be used on a 2.75 inch diameter beamline. It is made from 0.3 mm thick niobium sheet, rolled into a tube and secured by a longitudinal full penetration electron beam weld; the weld is made with a high speed a narrow, focused beam reducing the heat affected zone, thus limiting 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 bellows, which facilitated leak testing and allowed 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.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (US)
• Sponsoring Organization: USDOE Office of Energy Research (ER) (US)
• DOE Contract Number: AC05-84ER40150
• OSTI ID: 822206
• Report Number(s): JLAB-ACC-03-194; DOE/ER/40150-2620
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
43 PARTICLE ACCELERATORS
ACCELERATORS
ALIGNMENT
CAVITIES
CONTRACTION
CRYOGENICS
ELECTRON BEAMS
FABRICATION
FLANGES
GRAIN GROWTH
HEAT AFFECTED ZONE
LEAK TESTING
NIOBIUM
POLYURETHANES
STAINLESS STEELS
SUPERCONDUCTIVITY
VELOCITY
WAVELENGTHS