New World Vistas Research on Intense, Photoconductively-Switched Stacked Blumlein Modulators to Supply Ultra-Wideband HPM Systems

摘要

In this work, Several photoconductively- switched stacked Blumlein prototype were developed and successfully tested at power levels approaching 100 MW. These devices had a compact geometry and commutated by a single avalanche photoconductive switch. Special attention was placed on broadening of the switch current channels. Device longevity was tested by fabricating switch with metal or diamond coatings and by implementing different switch/electrode configurations. A significant improvement in switch lifetime was resulted by testing the diamond-coated switch performance in a prototype pulser. In order to obtain an understanding of electrical conduction mechanisms, semiconductor properties of amorphic diamond coatings were examined. Deposition of thin films of amorphic diamond on both Si and GaAs crystalline substrates produced rectifying heterojunctions with highly asymmetric current-voltage characteristics. When reversed biased, current levels from the heterojunction varied with the amount of reverse bias and the illumination and a photoconductive effect was observed. Measurements indicated an electrical breakdown strength of better than 3 x 10(exp 9) V/m for the amorphic diamond. The diamond/Si heterojunction devices were tested as photoconductive switches in our Blumlein pulsers where they successfully commutated the pulsers at low powers.