Investigating High Voltage Breakdowns for the nEDM Experiment at ORNL*

Roshan Gautam (Valparaiso University) 

For the nEDM collaboration

The neutron electric dipole moment (nEDM)experiment at Oak Ridge National Laboratory’s (ORNL) Spallation Neutron Source (SNS) aims to measure the nEDM to the level of 3 x 10-28e.cm , an improvement of two orders of magnitude from the current limit. In order to reach this goal, it is necessary to produce an electric field of 75 kV/cm inside a measurement volume containing superfluid helium at 0.4 K. But to obtain such a high operating field and properly inform the design of the final high voltage (HV) system in the experiment, a better understanding of electrical breakdown in liquid helium is needed. Several cryogenic HV apparatuses, including the Half-Scale HV (HSHV) and Small-Scale HV (SSHV) systems, have been constructed at Los Alamos National Laboratory (LANL) to support this effort. In this talk, the purpose of these two systems will be explained.  In addition, details on the work to improve the performance of the HV transfer line in the HSHV system as well as testing of the modifications to the SSHV system will be presented.