The Effect of Heat Treatments and Coatings on the Outgassing Rate of Stainless Steel Chambers

Journal Article · Sat Mar 01 04:00:00 EST 2014 · Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films

DOI:https://doi.org/10.1116/1.4853795· OSTI ID:1114181

Mamum, Md Abdullah A. ^[1]; Elmustafa, Abdelmageed A, ^[1]; Stutzman, Marcy L. ^[2]; Adderley, Philip A. ^[2]; Poelker, Matthew ^[2]

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1. Old Dominion Univ., Norfolk, VA (United States)
2. JLAB, Newport News, VA (United States)

The outgassing rates of four nominally identical 304L stainless steel vacuum chambers were measured to determine the effect of chamber coatings and heat treatments. One chamber was coated with titanium nitride (TiN) and one with amorphous silicon (a-Si) immediately following fabrication. One chamber remained uncoated throughout, and the last chamber was first tested without any coating, and then coated with a-Si following a series of heat treatments. The outgassing rate of each chamber was measured at room temperatures between 15 and 30 deg C following bakes at temperatures between 90 and 400 deg C. Measurements for bare steel showed a significant reduction in the outgassing rate by more than a factor of 20 after a 400 deg C heat treatment (3.5 x 10{sup 12} TorrL s{sup -1}cm{sup -2} prior to heat treatment, reduced to 1.7 x 10{ sup -13} TorrL s{sup -1}cm{sup -2} following heat treatment). The chambers that were coated with a-Si showed minimal change in outgassing rates with heat treatment, though an outgassing rate reduced by heat treatments prior to a-Si coating was successfully preserved throughout a series of bakes. The TiN coated chamber exhibited remarkably low outgassing rates, up to four orders of magnitude lower than the uncoated stainless steel. An evaluation of coating composition suggests the presence of elemental titanium which could provide pumping and lead to an artificially low outgassing rate. The outgassing results are discussed in terms of diffusion-limited versus recombination-limited processes.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE SC Office of Nuclear Physics (SC-26) (United States)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1114181
• Report Number(s): JLAB-ACC--13-1780; DOE/OR--23177-2744; arXiv:1307.4338
• Journal Information: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films, Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films Journal Issue: 02 Vol. 32; ISSN 0734-2101
• Country of Publication: United States
• Language: English

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