A cryogenic buffer gas beam source with in-situ ablation target replacement

TL;DR

This paper presents a cryogenic buffer gas beam source with an in-situ target replacement system that maintains high molecular yield and performance, enabling more efficient eEDM experiments without vacuum interruptions.

Contribution

It introduces a novel load-lock system for in-situ ablation target replacement in a cryogenic buffer gas beam source, improving yield and operational efficiency.

Findings

Produces 1.3×10^11 ThO molecules per pulse

Achieves a rotational temperature of 4.8 K

Long-term yield improved by 40% with biweekly target replacement

Abstract

The design and performance of a cryogenic buffer gas beam (CBGB) source with a load-lock system is presented. The ACME III electron electric dipole moment (eEDM) search experiment uses this source to produce a beam of cold, slow thorium monoxide (ThO) molecules. A key feature of the apparatus is its capability to replace ablation targets without interrupting vacuum or cryogenic conditions, increasing the average signal in the eEDM search. The source produces approximately $1.3 \times 10^{11}$ ground-state ThO molecules per pulse, with a rotational temperature of $4.8$ K, molecular beam solid angle of $0.31$ sr, and forward velocity of $200$ m/s. These parameters match the performance of traditional sources that require time-consuming thermal cycles for target replacement. A long-term yield improvement of about 40% is achieved when the load-lock system is used to replace targets biweekly.