Effects of gas temperature and gas mixtures on a triggered, sub-ns jitter, 50 kV, 100 Hz spark gap

Recent research efforts at Texas Tech University on impulse antenna phased array have shown that an ideal jitter of a small fraction of the rise-time is required to accurately synchronize the array to steer and preserve the rise-time of the radiated pulse. This has necessitated the need to develop a reliable high voltage, high repetition rate switch that will operate with very low jitter. This manuscript presents the impact gases and gas mixtures have on switch performance which includes recovery rate and in particular jitter. A 50 Ω, 1 nF pulse forming line is charged to 50 kV and provides the low inductance voltage source to test the different gases. Gases tested include N₂, dry air, H₂, and SF₆, as well as N₂-H₂, N₂-SF₆, N₂-Ar, and gas mixtures containing Kr⁸⁵. This manuscript will discuss in detail 50 kV, 100 Hz triggered switch operations of such gases. Switch jitter as a result of triggering conditions is also discussed, also including an evaluation of jitter as a function of formative delay in various gases. An evaluation of switch jitter as a function of operation time and gas temperature is also included. Triggering is provided by a solid state opening switch voltage source that supplies ~150 kV, 10 ns rise-time pulses at a rep-rate up to 100 Hz in burst mode. A hermetically sealed spark gap with a Kel-F -PCTFE (PolyCholoroTriFluoroEthylene) lining is used to house the switch and high pressure gas. It is shown that jitter is strongly dependent on the triggering technique, as well as the trigger magnitude, with ionization rates playing an important role. Sub-ns jitter is seen with a variety of gases and gas mixtures with H₂ producing the best results. Varying the gas temperature and addition of radioactive sources are seen to improve the switch jitter.