“Understanding electrical breakdown and its importance to the search for the neutron electric dipole moment”


The search for the neutron electric dipole moment (EDM) goes back over sixty years, beginning with the pioneering work of Purcell and Ramsey.  Its primary goal is the discovery of new physics in the CP violating sector, which may be critical to explaining the significant excess of baryons over antibaryons in the present Universe.  A novel, liquid helium-based experiment to be operated at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory plans to push the sensitivity of the neutron EDM measurement to unprecedented levels.  Vital to achieving the target sensitivity is the ability to operate at the highest electric fields (~75 kV/cm), but this necessitates a better understanding of the electrical breakdown phenomenon.  In this talk, a statistical analysis of breakdown data acquired in liquid helium is presented.  We show how the findings from this study can be used to inform the design of the high voltage system in the EDM experiment.  But with many present and future large-scale detectors in nuclear, particle, and astroparticle physics experiments employing high voltage inside a noble liquid detection medium, the methods proposed in this work has broader impact and may be applied towards exploring the behavior of electrical breakdown in other noble liquids.