DEVELOPMENT OF UNIFORM GAS DISCHARGE PLASMA SOURCES FOR PLASMA OPENING SWITCH APPLICATIONS

PLASMA OPENING SWITCHES (POS) ARE WIDELY USED FOR CURRENT COMPRESSION AND OWER AMPLIFICATION IN INDUCTIVE ENERGY STORE PULSE POWER SYSTEMS. FLASHBOARD PLASMA SOURCES ARE WIDELY USED AS PLASMA INJECTORS IN THESE POS'S. THE FLASHBOARD PLASMA IS PRODUCED BY SURFACE BREAKDOWN ON AN INSULATOR IN VACUUM. SINCE THE SURFACE CONDITIONS DEPEND ON THE PREVIOUS HISTORY, THE RESULTING PLASMA IS NOT UNIFORM, REPORDUCIBLE OR OF HIGH PURITY. A GAS BREAKDOWN PLASMA SOURCE IS PROPOSED TO REPLACE FLASHBOARD SOURCES. THIS SOURCE IS A VARIATION ON THE COAXIAL PLASMA GUN INVESTIGATED IN THE EARLY 1060'S FOR FUSION APPLICATIONS. THE PLASMA GUN CONSITS OF TWO CONCENTRIC ELECTRODES FILLED WITH GAS FROM A PUFF VALVE PRIOR TO APPLICATION OF A VOLTAGE PULSE FROM A CAPACITOR BANK. THE PLASMA IS ACCELERATED OUT OF THE GUN BY THE J X B FORCES ACTING ON THE CURRENT SHEET THAT FIRST FORMS ON THE INSULATOR WHEN THE GAS BREAKS DOWN. THE GUN PRODUCES PLASMAS DENSITIES OF 10 13TH TO 10 15TH/CM3 AT VELOCITIES OF 10 CM/US WHICH AE IN THE RANGE REQUIRED FOR POS APPLICATIONS. FURTHERMORE, A REPRODUCTIBLE GAS PUFF INSURES A REPRODUCIBLE PLASMA WITH LITTLE CONTAIMINATION FROM THE ELECTRODES OR INSULATOR. THE PULSE POWER DESIGNER CAN ACHIEVE A WIDE RANGE OF PLASMA CONDITIONS BY VARYING THE PLENUM PRESSURE, TIME DELAY BETWEEN ENERGIZING THE PUFF VALVE AND CAPACITOR BANK, THE CAPACITOR VOLTAGE, AND THE GAS SPECIE. COMPARABLE CONTROL WITH FLASHBOARDS WOULD REQUIRE VARYING THE NUMBER OF FLASHBOARDS WITH VIRTUALLY NO CONTROL OF PLASMA SPECIE. COMPACT SOURCES 15 CM OR LESS ARRE ANTICIPATED WITH THE ELECTRODE CROSS SECTION MODIFIED TO MATCH THE TRANSMISSION LINE GEOMETRY.