Articles you may be interested inSystematic uncertainties in shock-wave impedance-match analysis and the high-pressure equation of state of AlWe have developed a versatile tool for generating planar shock waves. This system, which we call the electric gun, is capable of projecting thin flyer plates with velocities in the range 1-20 km/s. It is presently being used in high-explosives-initiation experiments and is being developed for equation-of-state measurements in the 1-5 TPa range. We describe the electric gun facilities that are operational at Lawerence Livermore Laboratory and discuss applications of electric gun technology to problems of interest to shock-wave researchers.

Experimental observations of the energy-dependent electron-beam penetration in type II-A natural diamond are reported. The experimental data are compared with results obtained from numerical Monte Carlo simulations, and the results are in very good agreement. The results also reveal that a threshold energy of about 125 keV is necessary for complete penetration for a 35 µm sample. It is found that over the 30-180 ke V range, the energy dependence of the penetration depth and total path length exhibits a power-law relation. Monte Carlo simulations have also been performed to investigate the excess carrier-generation profiles within diamond for a set of incident e-beam energy distributions. The simulation results demonstrate the feasibility of tailoring the internal source function, and hence influencing the diffusion currents, the internal electric fields, and charge injection throµgh the contacts.

LAWRENCE UVERMORE LABORATORY MS, tlaio; April 27, U"T2 -NOTICE-This, report n prepared as an accotrat of work spaasored fay the United States Gofcrnment. Neither tt~ United States nor the United States Atomic Energy CaamiB»n, nor any of t^-cir employees, nor any of thek contractors, fecoatneton. or their cmpSoyees. makes any warrant, express or implied, or essoincs any legal EacOity or responsibility for the teem icy. com* pUteness or cieiqtoess of any inforcutioa, sppvitos, product or process diseased, cr represents that its tac would not iafriaie priYaiely owned rights. We have measured the conductivity induced in films of polyethylene, epoxy, polytetrafluoroethylene, polyethylene terephthalate, polyimide, and glass by 9 x rays at dose rates between 10 and 10 rads/sec (dose in air). The films were 0.05 to 1.25 mm thick. The x-ray spectrum peaked in the vicinity of 10 keV, and the x-ray pulse width was about 40 nsec FWHRI. X-ray-induced photocurrents were found to obey Ohm's law at low bias voltages (less than I kVl. Above 1 kV, however, we observed that the peak photoconductivity signals from some of the 0.05-mm-thick materials tegan to When the electrical components and circuitry of a warhead are exposed to a nuclear radiation environment, induced voltages and currents are generated that may be large enough to damage critical components and disable the warhead. In our continuing program at LL.L to under stand the mechanisms by which these voltages and electrical currents are gen erated, we are making careful laboratory measurements of charge emission from material surfaces as well as the charge displacement effects that occur within the bulk of the insulating layer under increase at a slightly faster than linear rate with bias voltage. The glass samples exhibited no appr.r^nt delaved conductivity, while the other sample materials shewed various amounts. The magnitude of the delayed conductivity in polytetrafluoro ethylene, polyethylene terephthalate, and polyimide depended on the electric field, ec an effect that is consistent with PooleFrenkel fie'.d-assis :eo carrier generation.

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Ballistic electron emission microscopy studies of electron scattering in Au/GaAs Schottky diodes damaged by focused ion beam implantationExperimental studies on a vertical metal-diamond-silicon switch structure have been conducted for potential pulsed power applications. Both the dc current-voltage characteristics and the transient switching response have been measured for a range of voltages. With a 1 pm diamond film, the switch has been seen to withstand electric Aelds up to 1.8 MV/cm. Our results show a polarity dependence which can be associated with current injection at the asymmetric contacts. Polarity effects were also observed in the presence of e-beam excitation, and arise due to nonuniform carrier generation near the diamond-silicon interface. Our switching transients were seen to follow the shape of the e-beam for a negative bias at the silicon substrate. For positive voltage values exceeding about 80 V however, the switch is seen to go into a persistent-photocurrent mode. This effect is a result of free carrier trapping within diamond and is enhanced by the double injection process.