Title:  Studies on high electric field in liquid helium for the SNS neutron electric dipole moment experiment

Abstract:
The neutron electric dipole moment (nEDM) experiment at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is a novel, liquid helium-based experiment, planning to push the sensitivity of the nEDM measurement to nearly two orders of magnitude beyond the existing limit.  To achieve this goal, operating at the highest electric fields (~ 75 kV/cm) is necessary for the reason that the shift in the neutron spin precession frequency, which is a signature of a non-zero EDM, is proportional to the strength of the applied field.  This precession frequency is determined from measurements of the liquid helium scintillation generated by the spin-dependent capture of neutrons onto a small concentration of 3-He atoms in the bulk 4-He liquid volume.  However, the requirement for such high electric fields in the experiment brings about many challenges.  One of which is the suppression of electrical breakdown, and this, in turn, requires a better understanding of this complicated phenomenon.  Furthermore, the presence of a high applied electric field has a significant effect on the scintillation yield.  It is, therefore, important to measure the field dependence of the yield in conditions closely approximating that in the actual EDM experiment.  In this talk, I will discuss the R&D work that we have done at LANL to address these challenges and the implications of our findings thus far, and the plans for our future work.