Time dependence of neon emission during NEG cartridge heating

Determine the time dependence of neon emission from heated non-evaporable getter (NEG) cartridges (SAES Capacitorr D-400) installed in the LHC beam vacuum near ATLAS, specifically whether neon is released gradually with the total amount scaling with heating duration or is emitted predominantly immediately after heating begins.

Background

To explain unphysically high BCM detection efficiencies inferred for pressure bumps near 19 m and 22 m, the authors hypothesize that neon in addition to hydrogen was released from heated NEG cartridges. Laboratory tests indicate that significant amounts of neon can indeed be emitted upon heating a cartridge that was previously exposed to neon at atmospheric pressure. However, the temporal emission profile of neon during heating critically affects the interpretation of observed background features, such as early overshoots in BCM rates and lingering excess after heating stops.

The study notes that without knowing whether neon is emitted promptly or gradually over the heating period, it is impossible to refine the modeling and conclusively attribute certain observed time-dependent features to neon. Clarifying the emission dynamics is necessary to validate or refute the two-gas hypothesis and to improve future background predictions and mitigation strategies.

References

A detailed time dependence of the neon emission, however, is not determined in these tests. It is not clear if the neon is emitted gradually such that the total amount would scale with the heating time or predominantly soon after the heating of the NEG cartridge starts.

— Beam-induced backgrounds measured in the ATLAS detector during local gas injection into the LHC beam vacuum  (2405.05054 - Collaboration, 2024) in Section 6.3 (Possible neon contribution)