A Second-Generation Experimental Apparatus for Direct Observation of Anode Initiated Vacuum Surface Flashover

William Brooks, Texas Tech University

Photo of William Brooks

Vacuum surface flashover imposes size requirements for large-scale pulsed power machines. Our understanding of the subject imposes a hard barrier to the modernization and improvement of existing infrastructure. Modern insulator configurations suppress cathode-initiated flashover and requires anode-initiated flashover to be considered. This is achieved by mitigating the electric field at the cathode at the expense of the anode field being several times higher. The mechanism of anode-initiated flashover is of limited understanding but is believed to depend on the cascade growth of a conducting plasma along the length of the insulator from the anode. In the case of pulsed, anode-initiated flashover, experimental evidence suggests that charge is directly extracted from the insulator resulting in the insulator taking on a net positive charge advancing the anode potential. Along with accompanying gas desorption from the surface, the potential will then propagate from the anode towards the cathode until the effective length of the gap is sufficiently reduced to support flashover. A first-generation test fixture for direct localization and direct observation of vacuum surface flashover is presented along with a discussion of the insight gained by the apparatus. A review of limitations and challenges encountered is included along with a review of the second-generation platform which is being developed.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

Abstract Author(s): William Brooks, Raimi Clark, Jacob Young, Matthew Hopkins, James Dickens, Jacob Stephens, Andreas Neuber