Positive polarity voltage adder miti, experiments on helia"'

HELIA is a four stage, 4-MV, 250-kA, 30-ns accelerator used to study the design concepts for Hermes III. The accelerator consists of eight pulse forming lines (PFLs) that deliver 1-MV, 125-kA pulses to four linear induction cavities. The cavities are in series. and the voltage addition is accomplished in a coaxial self magnetically insulated transmission line (MITL). A positive polarity experiment has been performed on Hermes Ill that shows efficient current transport through the system. HELIA has been reconfigured for positive polarity operation, and initial experimental results show operation consistent with Hermes Ill results. These experiments are aimed at obtaining a more complete understanding of the system performance in positive polarity and to investigate the interactions of the cavities, adder MITL, and extensions in this configuration. Initial results and details of these tests are presented in this paper.