Non-evaporable getter coating chambers for extreme high vacuum

TL;DR

This paper presents advanced NEG coating techniques for large and complex chambers achieving ultra-high vacuum levels, with detailed surface analysis and pressure measurements in polarized electron sources.

Contribution

It introduces new NEG coating processes for complex geometries and demonstrates ultra-high vacuum performance in polarized electron source chambers.

Findings

Achieved base pressure as low as 1.56x10^-12 Torr with NEG coating.

Modified NEG coating process for complex geometries.

Pressure in electron source chambers approaches XHV range.

Abstract

Techniques for NEG coating a large diameter chamber are presented along with vacuum measurements in the chamber using several pumping configurations, with base pressure as low as 1.56x10^-12 Torr (N2 equivalent) with only a NEG coating and small ion pump. We then describe modifications to the NEG coating process to coat complex geometry chambers for ultra-cold atom trap experiments. Surface analysis of NEG coated samples are used to measure composition and morphology of the thin films. Finally, pressure measurements are compared for two NEG coated polarized electron source chambers: the 130 kV polarized electron source at Jefferson Lab and the upgraded 350 kV polarized 2 electron source, both of which are approaching or within the extreme high vacuum (XHV) range, defined as P<7.5x10^-13 Torr.