CERN Accelerating science

Article
Title	Development of NEG Coating for RHIC Experimental Beamtubes
Author(s)	Weiss, Daniel ; He, Ping ; Hseuh Hsiao Chaun ; Todd, Robert J
Affiliation	(BNL, Upton, Long Island, New York)
Publication	2005
In:	21st IEEE Particle Accelerator Conference, Knoxville, TN, USA, 16 - 20 May 2005, pp.3120
Subject category	Accelerators and Storage Rings
Abstract	As RHIC beam intensity increases beyond original scope, pressure rises in some regions have been observed. The luminosity limiting pressure rises are associated with electron multi-pacting, electron stimulated desorption and beam induced desorption. Non-Evaporable Getter (NEG) coated beampipes have been proven effective to suppress pressure rise in synchrotron radiation facilities. Standard beampipes have been NEG coated by a vendor and added to many RHIC UHV regions. BNL is developing a cylindrical magnetron sputtering system to NEG coat special beryllium beampipes installed in RHIC experimental regions. It features a hollow, liquid cooled cathode producing power density of 500W/m and deposition rate of 5000 Angstrom/hr on 7.5cm OD beampipe. The cathode, a titanium tube partially covered with zirconium and vanadium ribbons, is oriented for horizontal coating of 4m long chambers. Ribbons and magnets are arranged to provide uniform sputtering distribution and deposited NEG composition. Vacuum performance of NEG coated pipes was measured. Coating analysis includes energy dispersive spectroscopy, auger electron spectroscopy and scanning electron microscopy. System design, development, and analysis results are presented.