10.2172/1234568

Abstract

Advanced switching devices with long lifetime will be critical components for Linear Transformer Drivers (LTDs) in next-generation accelerators. LTD designs employ high switch counts. With current gas switch technology at %7E10e3 shot life, a potential game-changer would be the development of a reliable low-impedance (%3C35nh) optically-triggered compact solid-state switch capable of switching 200kV and 50kA with 10e5 shotlife or better. Other applications of this technology, are pulse shaping programmable systems for dynamic material studies (Z-next, Genesis), efficient pulsed power systems for biofuel feedstock, short pulse (10 ns) accelerator designs for the Defense Threat Reduction Agency (DTRA), and sprytron replacements in NW firing sets. This LDRD project has succeeded in developing new optically-triggered photoconductive semiconductor switch (PCSS) designs that show great promise for scaling to modules capable of 200kV (DC) and 5kA current that can be stacked in parallel to achieve 100's of kA with 10e5 shot lifetime. . Executive Summary Advanced switching devices with long lifetime will be critical components for Linear Transformer Drivers (LTDs) in next-generation accelerators. LTD designs employ high switch counts. With current gas switch technology at %7E10e3 shot life, a potential game-changer would be the development of a reliable low-impedance (%3C35nh) optically-triggered compact solid-state switch capablemore » of switching 200kV and 50kA with 10e5 shotlife or better. Other applications of this technology, are pulse shaping programmable systems for dynamic material studies (Z-next, Genesis), efficient pulsed power systems for biofuel feedstock, short pulse (10 ns) accelerator designs for the Defense Threat Reduction Agency (DTRA), and sprytron replacements in NW firing sets. This LDRD project has succeeded in developing new optically-triggered photoconductive semiconductor switch (PCSS) designs that show great promise for scaling to modules capable of 200kV (DC) and 5kA current that can be stacked in parallel to achieve 100's of kA with 10e5 shot lifetime. The new vertical switch design configuration generates parallel filaments in the bulk GaAs (as opposed to just beneath the surface as in previous designs) to achieve breakdown fields close to the maximum for the bulk GaAs while operating in air, and with 2-D scalability of the number of current-sharing filaments. This design also may be highly compatible with 2-D VCSEL arrays for optical triggering. The demonstration of this design in this LDRD utilized standard thickness wafers to trigger 0.4kA at 35kV/cm (limited by 0.6mm wafer thickness), tested to 1e5 shots with no detectable degradation of switch performance. Higher fields, total current, and switching voltages would be achievable with thicker GaAs wafers. Another important application pursued in this LDRD is the use of PCSS for trigger generator applications. Conventional in-plane PCSS have achieved triggering of a 100kV sparkgap (Kinetech-type) switch of the type similar to switches being considered for accelerator upgrades. The trigger is also being developed for pulsed power for HPM applications that require miniaturization and robust performance in noisy compact environments. This has spawned new programs for developing this technology, including an STTR for VCSEL trigger laser integration, also pursuing other follow-on applications.« less