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O'Brien H.K.,U.S. Army | Shaheen W.,Berkeley Research Asociates Inc. | Ogunniyi A.,U.S. Army | Scozzie C.,U.S. Army | And 6 more authors.
Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014 | Year: 2014

Asymmetric thyristors require protection from voltage and current reversals in high-inductance capacitor discharge systems. Silicon carbide (SiC) PiN diodes capable of blocking up to 16 kV were demonstrated to have the high-current capability to transmit forward pulse current in a series configuration with a thyristor, and to clamp reverse current in an anti-parallel configuration. In series with a thyristor, diodes were switched 1000 pulses at a single-shot rate at 2000 A peak current (3.8 kA/cm2 over anode area and 2100 A2s per pulse) without any notable increases in forward voltage or reverse leakage current. In the reverse clamp configuration, a parallel pair of PiN diodes was demonstrated to block 12 kV charge on the capacitor bank, then clamp a total of 4200 A current reversal with good parallel current sharing. These evaluations demonstrate that for high current density pulsing above 10 kV, individual 16 kV PiN diodes yield lower on-state voltage loss (16 V at 2000 A) than series-stacked assemblies of 9 kV SiC PiN diodes or 6 kV Si diodes. © 2014 IEEE. Source


Weaver J.L.,U.S. Navy | Obenschain S.P.,U.S. Navy | Sethian J.D.,U.S. Navy | Schmitt A.,U.S. Navy | And 14 more authors.
Fusion Science and Technology | Year: 2013

Recent designs for laser driven, direct drive inertial confinement fusion (ICF) indicate that substantial gains (G>100) might be achieved with lower total laser energy (E∼500 kJ) than previously considered possible. A leading contender is the shock ignition approach which compresses low aspect ratio pellets with high intensity laser pulses (1015 W/cm2) before achieving ignition with a final higher intensity spike (1016 W/cm2). Excimer laser systems based on a krypton-fluoride (KrF) medium are particularly well suited to these new ideas as they operate in the ultraviolet (248 nm), provide highly uniform illumination, possess large bandwidth (1-3 THz), and can easily exploit beam zooming to improve laser-target coupling for the final spike pulse. This paper will examine target physics advantages of KrF lasers in relation to the new implosion designs and the balancing of hydrodynamic instability and laser-plasma instabilities. Supporting experimental and theoretical studies of are being conducted by the Nike laser group at the U. S. Naval Research Laboratory. Recent experimental work has also shown that the high ablation pressures and smooth profiles obtained with the Nike laser can be used to accelerate planar targets to velocities consistent with the requirements of impact ignition. Source


O'Brien H.,U.S. Army | Ogunniyi A.,Berkeley Research Asociates Inc. | Shaheen W.,Silicon Power Corporation | Scozzie C.J.,U.S. Army | Temple V.,Berkeley Research Asociates Inc.
Digest of Technical Papers-IEEE International Pulsed Power Conference | Year: 2015

The Army Research Laboratory collaborated with Silicon Power Corporation to package sixteen parallel 9 kV, 1.0 cm2 silicon carbide (SiC) super gate turn-off thyristors (SGTOs) in a single 82 cm3 module using Silicon Power's materials and techniques from silicon packaging the peak current switched was 84 kA for a 43-μs pulse width as measured at half-maximum the rising slope calculated from 10-90% of the peak was 10 kA/μs, and the action under the curve was 2.6 × 105 A2s. Results encouraged further development of larger-area devices with higher 15 kV blocking in order to fully utilize the package area and create a single-layer >10 kV pulse switch. Challenges in the development of this SiC SGTO module include optimizing SiC material uniformity and device yield, controlling turn-on of sixteen parallel devices, and maximizing high-voltage blocking of the complete package. © 2015 IEEE. Source

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