INVESTIGATION OF RF BREAKDOWNS ON THE MILO

This paper describes a series of experiments performed to isolate the RF breakdown mechanisms in the hard tube magnetically insulated transm ission line oscillator (MILO) Experiment at the Air Force Phillips Lab oratory, Albuquerque, NM. Specifically, several causes of RF breakdown in the region of the vacuum-air interface and the antenna region have been investigated. These causes are X-ray induced electron emission, VUV and visible photoemission of electrons, and breakdown due to large field stresses in the antenna. Each of these mechanisms has the effec t of liberating electrons from a surface in a high field region which then are a seed for a breakdown. This paper discusses measurements in the X-ray, VUV, and visible regimes with support from computer simulat ion. Also, imagery results are shown, which in conjunction with the co mputer work, point to the presence of high electric field stresses in the antenna, which cause a subsequent breakdown. In particular, X-rays , VUV, visible light, and plasmas do not seem to be the major source o f RF breakdown in this tube.