Investigating the minimum post-burst energy required to function an exploding bridgewire detonator

摘要

The minimum energy required after bridge-burst to function a commercially available RP-1 exploding bridgewire detonator with a gold bridgewire was investigated using two capacitor discharge units (CDUs) making use of state-of-the-art on/off high-voltage high-current switches. Both switches are capable of shutting off the current flow in ≈ 100 ns and the conduction time was varied systematically to limit the duration of electrical energy delivered from the CDU until a detonation goo-go threshold was reached. It was found that the minimal extra electrical energy required for a soft-fire (a statistically marginal go) was approximately half that required for a hard-fire (a definite go). The measured energy required to function the RP-1 detonator from the 11.5kV CDU was approximately 20 mJ greater than for the 600 V CDU, and it is postulated that this was due to arcing across the detonator terminals and an associated current shunt that was not efficient at depositing energy conducive to detonator functioning. Measurements of the bridgewire temperatures bursting in air showed that the maximum temperature reached was consistent (≈ 18 kK) when sufficient energy was delivered that the detonator functioned (either soft- or hard-fire), but that the temperature for a sub-threshold bridgewire burst was significantly cooler at approximately 8 kK. Furthermore, it was demonstrated that the intensity of the light emitted at burst scaled with deposited energy. A related finding is that the light emission from the bridgewire peaks some tens of nanoseconds after both peak voltage and peak electrical power.