Thermal instability of electrolytic capacitor bank used for gas puff valve

Abstract

It is shown that self-heating of electrolytic capacitors causes the output current of a capacitor bank to increase with successive shots even though the charge voltage is held constant. Self heating of only 10°C can cause a near tripling in the gas output of the gas puffing valves commonly used in spheromak research. By using metallized polypropylene film capacitors instead of electrolytic capacitors the reproducibility is substantially improved ͑the shot-to-shot variation in gas output is reduced to be Ͻ0.5%͒.

Magnetically Driven Flows in Arched Plasma Structures

“…The field strength has a temporal FWHM of 7 ms and spatially varies from 0.35 T near the footpoints to 0.01 T near the apex of the arch. At each footpoint is a gas nozzle, connected to a fast gas valve [18]. There is no neutral prefill.…”

Emission and afterglow properties of an expanding RF plasma with nonuniform neutral gas density

“…22 In Fig. 2(a), we show the total time-dependent emission measured by the photodiode at the rear of the discharge tube during discharges with the RF power on for 200 ls, for a range of gas bank voltages from 450 V to 700 V. The discharge was very bright at early times due to the elevated electron temperature and high neutral argon excited state populations, 6 and then it dimmed and approached a steady state brightness from t ¼ 100-200 ls.…”

Battery-powered pulsed high density inductively coupled plasma source for pre-ionization in laboratory astrophysics experiments

“…18 The gas density distribution at the time when the electrodes were energized was not measured in this work, but it was possible to make inferences about the relative gas pressures in different situations based on the known properties of the gas valves 36 and on the observed jet velocity.…”

“…For jet experiments, there was no uniform argon backfill; instead, three fast pulsed gas valves 18 were used to inject gas through small holes in the jet experiment's cathode and anode (see Figs. 1 and 3), and also into the RF plasma source tube.…”

“…For pre-ionized MHDdriven jet experiments, gas was delivered to the discharge tube through a feedthrough at the rear end of the tube by a fast pulsed gas valve. 18 During testing and optimization of the pre-ionization source, a variable leak valve (Granville-Phillips Series 203) attached to a feedthrough near the center of the main chamber was used to produce a uniform fill pressure. An ultraviolet (UV) flashlamp (Excelitas Technologies model FX-1165 Metal Can Xenon Flashlamp with Reflector) was attached to the end of the discharge tube behind the gas feed connection-firing this lamp at the time of RF turn-on provided seed ionization that improved the consistency of the RF plasma breakdown and made the time-dependent behavior of the experiment extremely reproducible.…”