SCIENTIFIC APPLICATIONS & RESEARCH ASSOCIATES, INC. — Department of Defense STTR Phase II: DTRA16A-004

Description

For effective protection against radiated threats, produced by high altitude electromagnetic pulse (HEMP) caused by nuclear detonations and high-power microwave (HPM) Directed Energy (DE) weapons it is important to understand not only the physics of the threats, but also to quantify the effects on mission-critical electrical systems. EMP/HMP simulators enable threat level testing of MCS and provide stakeholders valuable quantitative information pertaining to such threats so that engineering principals, risk mitigation designs/protocols, and countermeasures can be implemented. The protection of MCS is necessary to ensure the integrity and survivability of government and economic assets from HEMP and HMP events. HEMP vulnerability and susceptibility testing requires the delivery of high peak power and high peak electric fields to targets. The most practical solution to simulate such environments on mission -critical systems is to develop a modular, portable, optically isolated MV-antenna array. This proposal presents an inexpensive 100 kV Pulse Charger and a low-jitter Laser Trigger System capable of simultaneously driving many gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS) to drive largescale antenna arrays with <300 ps of timing jitter. The goal is to fabricate a mobile EMP simulator capable of generating the early time E1 portion of a HEMP event. To prevent damaging the GaAs PCSS, the primary charge storage capacitor and GaAs PCSS must be pulse charged to ± 50 kV in less than 10 us, therefore limiting the voltage seen by the switch. The developed pulse charger architecture has achieved ≈ 100 kV differential output in < 4 ms.   The developed Q-switched laser system has operating wavelength of 840 nm, optical pulse rise time (10 to 90 %) of 3-4 ns, pulse width (FWHM) of 10 - 15 ns. The pulse energy delivered to each GaAs PCSS is >1500 mJ and spread over about 3 cm2 (500 mJ/cm2) and provides prompt triggering with peak power exceeding 100 kW. The primarily focus of the proposed effort will be on designing an improved and novel antenna radiator which minimizes impedance mismatches, demonstrating the 3x3 array to be a viable E1 EMP simulator test option, comparing acquired electric field data to openly available published data on existing E1 standards, and electric field characterization of the improved single horn antenna and array.