Mesh-initiated detonation and effect of current-pulse waveform

The paper describes the development and manufacture of novel electrically exploding etched and through-hole plated copper mesh bridgewire designs, to detonate coated PETN (pentaerythritol tetranitrate) explosive on both single curved and hemispherical surfaces. Results which demonstrate that the required rise time of the mesh current must lie within certain boundaries are presented. Two very low inductance circuit rigs are mentioned; a 450 J, 30 kV unit employing a 1 /spl mu/F capacitor, and a 12 kJ, 30 kV unit employing a 28 /spl mu/F capacitor. Both rigs utilise triggered three-electrode spark gaps to switch the capacitors into the mesh circuit elements. Chemically etched copper surface and novel through-hole plated mesh designs up to 150 mm square are described, with breakout simultaneity within 100 ns and adjacent fuse site simultaneity to within 40 ns. Through-hole plating techniques normally associated with printed circuit board manufacture have been modified to form the fuse sites, and utilised to enable even distribution of fuse sites over a hemispherical surface and the capability of switching array sizes and configurations. Inner and outer copper coated surfaces form the current path to the fuse sites. The small holes produced during the manufacture of the fuse sites provide both a key between the PETN explosive coating and the mesh surface and also confine the explosive, and thereby improve the detonation interface.