Comprehensive study of high power ignitrons
Loree, Diana Lynn
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This dissertation describes research involving various aspects of high power ignitron switches and their behavior under high current and/or high coulomb conditions. Three workshops held at Texas Tech University, Lawrence Livermore National Laboratory, and Richardson Electronics, produced suggestions for areas of research necessary to improve the coulomb capability, peak current carrying capability, and lifetime of ignitron switches. As a result, the effects of axially applied magnetic fields have been studied, and plasma diagnostic investigations, including optical and microwave interferometry, have been conducted. Special ignitrons, some of which had optical access to the discharge volume, have been used to achieve this. Application of the magnetic field caused a drastic reduction in the holdoff voltage capability of the test switches, reducing it to just over 300 volts for some tubes. Four anode geometries, flat, cup, slit-cup, and spiral, were studied for their effects upon the discharge plasma and its arc resistance. Photographic studies of anode geometry reveal the sculptured anodes can induce discharge motion, which can reduce material vaporization from the anode thus increasing tube lifetime by limiting the contamination of the mercury pool. Interferometry covering two density ranges revealed the first measured plasma density for a full size ignitron, which was on the order of 1.4*10^16 cm^-3 at 115 kA with an average post-conduction diffusion rate constant on the order of 2.7*10^3 s^-1. Further research comparing the performance of a spark gap igniter to a normal igniter has also been performed with the jitter value for both igniters shown to be on the order of 100 ns. Much of this work has used a specially built, demountable ignitron, and a 2.56 mF, 10 kV capacitor bank, charged with a 2 A constant current power supply.