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|Light-initiated detonation systems
United States. Assistant Secretary of the Army (R & D)
Cooper, Stafford S.
Malone, P. G.
Bartholomew, Stephen W.
Necker, William J.
|Geotechnical Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
|Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; GL-86-28.
Abstract: Explosives can, theoretically, be initiated either by photochemical reactions or by heat and shock effects in sensitive compounds. Explosive photochemical reactions are attractive because they require very low energy inputs and operate at specific wavelengths. However, most of these reactions require energetic (ultr aviolet or near ultra-violet) light. The optical fibers that are presently manufactured are intended for data transmission and have low efficiency at short wavelengths. Heat and shock initiation uses longer wavelengths that are transmitted efficiently on existing fibers. Numerous light sources could be employed in detonation systems, but lasers have the most efficient coupling to optical fibers and can generate energetic light pulses required for detonation. Flash lamp-pumped, solid state lasers are presently the mosl useful light source for explosives initiation. Laser diodes in current production cannot generate enough energy for practical applications. The most useful optical fiber for blast line application is a step index fiber with a large core-to-cladding ratio. The large core minimizes energy losses due to misalignment core of fibers in connectors. Couplers that involve mechanically crimped connectors and cleaved fibers, rather than the epoxy-cemented connectors with polished fibers, provide superior energy transmission due to the reduced carbonization at the fiber end. Detonators for optical initiation systems are similar in basic construction to those employed in electrical initiation systems. Explosive and pyrotechnic charges can also be similar. Either primary or secondary explosives can be initiated in present laser-based systems. Two laser detonation systems are presently accessible; a multiple-shot laser with a single-shot, single fiber system designed for use with detonators containing primary explosives. Additional research related to development of low-energy, photoreactive detonators, continuity checking techniques and improved connectors and fibers can produce significant improvements in presently fielded systems.
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