Development of a Niobium Bellow for Beamline Connections

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

OSTI ID:816824

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. The bellows 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 long 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. Motivated by this 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 at high speed with a narrow, focused beam reducing the heat affected zone, thus limiting the grain growth, which could affect the formability. Subsequently, two convolutions are pressed into this tube in a 2-stage process, using an external die and a polyurethane internal expander. Niobium cuffs and flanges are electron beam welded to the formed bellows, which facilitates leak testing 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.

• 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: 816824
• Report Number(s): JLAB-ACC-03-194; DOE/ER/40150-2576
• Country of Publication: United States
• Language: English

Related Subjects

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