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Investigations of medium-temperature bakes to achieve low outgassing rates in stainless steel ultra-high vacuum chambers

Published

Author(s)

Makfir Sefa, James A. Fedchak, Julia Scherschligt

Abstract

We determined the outgassing rate of vacuum chambers constructed from common 304 stainless steel vacuum components. The vacuum components were assembled into identical vacuum chambers and subjected to either a medium temperature vacuum bake or a medium temperature air-bake. Both heat treatments were in the range of 400 °C to 450 °C. The air-bake was performed with the interior and exterior surfaces of the vacuum chambers exposed to air at atmospheric pressure; the vacuum bake was performed with the interior surfaces of the components in high-vacuum, but the exterior surfaces exposed to the ambient atmosphere. The medium temperature vacuum bake produced an outgassing rate on the order of 10-11 Pa L/cm2/s, nearly one order of magnitude lower than the air bake for identical components baked for the same period of time and at the same temperature. We then took the components subject to the medium-temperature vacuum heat treatment and subjected them to a 24-hour air bake at 430 °C. This additional heat treatment lowered the outgassing rate by nearly a factor of two. A third identical vacuum chamber was constructed and baked in dry air at 250 °C for 48 hours. Compared to identical vacuum chambers subjected to no heat treatment, the lower temperature dry-air bake resulted in an outgassing rate that was lower by more than a factor of two. Finally, a fourth identical chamber was subjected to a dry-air bake at 415 °C for 48 hours, resulting in an outgassing rate that was lower by more than a factor of 4 compared to an identical chamber subjected to no heat treatment. The aim of this study was to obtain ultra-low outgassing rates using commonly available vacuum components. We conclude that the medium-temperature vacuum bake was sufficient for this purpose.
Citation
Journal of Vacuum Science & Technology A
Volume
35
Issue
4

Keywords

Outgassing, vacuum science, ultra-high vacuum, extreme-high vacuum, ultra-low outgassing

Citation

Sefa, M. , Fedchak, J. and Scherschligt, J. (2017), Investigations of medium-temperature bakes to achieve low outgassing rates in stainless steel ultra-high vacuum chambers, Journal of Vacuum Science & Technology A, [online], https://doi.org/10.1116/1.4983211, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=922647 (Accessed April 22, 2024)
Created June 30, 2017, Updated October 12, 2021