High-voltage pulse testing of cables on Hawk

The Hawk facility at NRL was used to pulse test Dielectric Sciences(1) 2158 cable to voltages in excess of 900 kV. The motivation for the testing was to assess the utility of these cables to connect elements in a high-impedance inductive voltage adder system. A high voltage pulse was launched at both ends of a long length of cable to obtain high voltage by wave adding in the middle of the cable while limiting high voltage complications at the power feeds to the cables. The pulse width was controlled with a point-plane electron beam diode. Extensive modeling was used to design and analyze the experiment. Potential plotting was employed to design the field shapers used to connect the outer conductor of the cable to the power feeds, and verify that we could expect to achieve appropriately high voltage on the cables. The initial impedance of the point-plane diode was modeled with the MAGIC PIC code. A transmission-line code was used to model the overall circuit and infer the voltage in the cable as a function of position and time. Four lengths of cable were tested. The cable is designed for use as 69 kV AC power cable. Three of the four cables survived pulses in excess of 900 kV before failing, and the fourth cable failed at over 700 kV. Extensive results of the tests on the 2158 cables will be presented.