Small metal bridgewires are commonly used to ignite energetic powders such as pyrotechnics, propellants, and primary or secondary explosives. In this paper we describe a new means for igniting explosive materials using a semiconductor bridge (SCB). When driven with a short (20 μs), low-energy pulse (less than 3.5 mJ), the SCB produces a hot plasma that ignites explosives. The SCB, a heavily n-doped silicon film, typically 100 μm long by 380 μm wide by 2 μm thick, is 30 times smaller in volume than a conventional bridgewire. SCB devices produce a usable explosive output in a few tens of microseconds and operate at one-tenth the input energy of metal bridgewires. In spite of the low energies for ignition, SCB devices are explosively safe. We describe SCB processing and experiments evaluating SCB operation. Also discussed are the SCB vaporization process, plasma formation, optical spectra from the discharge, heat transfer mechanisms from the SCB to the explosive powders, and SCB device applications.
Integral elastic cross sections of hydrogen atoms scattered by rare gases have been measured in the velocity range 1.4-14 x lo5 cm s-' (0.01 < Ecm< 1.00 eV). The experimental data have been fitted to the Lennard-Jones and exp (a,6) potential models and are found to provide information on the attractive and repulsive parts of the potential. The potential well parameters E, Rm and the Born-Mayer repulsive potential parameters A , ac have been determined for all of the rare gases. These c, Rm parameters, in combination with the corresponding rare gas dimer parameters, are shown to be consistent with combining rules.Despite the fact that the H-atom is the simplest of atoms, its interaction potentials with other atoms and molecules are largely unknown. Being an abundant constituent on earth and the most abundant element in outer space these potentials are of fundamental importance for understanding gas phase reactions,' recombination mechanisms,2 9 high temperature transport properties and collisional energy transfer, both in the laboratory and in interstellar space.4* Theory only provides reliable values for the coefficient of the leading term in the long range potential.6 The next higher order attractive R-8 term, which is expected to make a large (20-30 %) contribution to the well depth, has, however, not yet been calculated. A priori calculations of the short range repulsive potential are only available for H-He ' and H-Ne.8Work is in progress on H-Ar.'The first measurements of the velocity dependence of the integral cross section for these systems were carried out by Herschbach and coworkers lo* who were able to deduce rough values for the strength parameter (= ER,) for these systems. Recently, more accurate absolute integral cross sections have been measured for Ar, Kr and Xe at H-atom velocities in the range of 1.8 to 6.2 x lo5 cm s-',12 and the results were interpreted in terms of E and Rm. A precision measurement of absolute integral cross sections for H-He has been used in connection with the relative measurements reported here to obtain an accurate potential curve for this system for comparison with theory.' EXPERIMENTAL A schematic drawing of the apparatus is shown in fig. l.14 The hydrogen atom beam is produced by thermal dissociation in a cylindrical tungsten oven, which is heated by electron bombardment to 2500-2600K. At inlet pressures of about 1 Torr the measured degree of dissociation is roughly 0.40. After leaving the oven chamber (at the left in fig. 1) through a conical skimmer, the beam passes through a mechanical Fizeau-type velocity selector (Av/v = 11 %, Av is the FWHM spread ; urnax = 14x lo5 cm s-' at 650 Hz
Sandia National Laboratories' semiconductor bridge, SCB, is a maturing technology now in use in several new applications. Those applications required explosive assemblies that were light weight, small volume, low cost, and needed only small quantities of electrical energy to function. Explosive assembly here refers to the combination of the firing set (the current source for the firing signal) and the explosive component. Because conventional firing systems could not meet the new reduced size, weight and energy requirements, SCB systems were developed for applications that range from Sandia devices to commercial igniters for fireworks. This paper is a brief overview of SCB technology with examples of SCB explosive systems designed to meet modern requirements.
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