High-Sensitivity Measurement of 3He-4He Isotopic Ratios for Ultracold Neutron Experiments

TL;DR

This paper presents a highly sensitive accelerator mass spectroscopy method to measure ultra-low 3He/4He isotopic ratios, surpassing traditional techniques, with implications for neutron experiments and future sensitivity improvements.

Contribution

The paper introduces a novel accelerator mass spectroscopy approach achieving 10^-14 sensitivity for helium isotopic ratios, enabling measurements previously unattainable with standard methods.

Findings

Achieved 10^-14 sensitivity in 3He/4He measurements.

Identified the need for corrections in samples relevant to neutron lifetime.

Outlined a clear path to further increase sensitivity by at least an order of magnitude.

Abstract

Research efforts ranging from studies of solid helium to searches for a neutron electric dipole moment require isotopically purified helium with a ratio of 3He to 4He at levels below that which can be measured using traditional mass spectroscopy techniques. We demonstrate an approach to such a measurement using accelerator mass spectroscopy, reaching the 10e-14 level of sensitivity, several orders of magnitude more sensitive than other techniques. Measurements of 3He/4He in samples relevant to the measurement of the neutron lifetime indicate the need for substantial corrections. We also argue that there is a clear path forward to sensitivity increases of at least another order of magnitude.