STUDIES ON WORKING TIME REPRODUCIBILITY OF A LASER IGNITED DETONATOR

摘要

By means of laser diode or solid laser source, it is known how to operate an optical detonator by a thermal laser ignition thanks to the internal control of a transition process: either a deflagration-detonation transition (DDT) or a shock-detonation transition (SDT). This paper shows how, with a Nd-YAG source, in free running mode, the function time reproducibility of a laser thermally ignited detonator can be controlled. The experimental results point out that, with an optical power density close to 3 MW/cm~2 delivered to the first ignition increment through a 200 μm optical fiber, a laser thermally ignited detonator characterized by a second stage operating along an SDT mechanism, has a function time equal to 47 us with a dispersion less than ±5 μs. This low time dispersion has been observed on operational temperature range (-50°C, + 100°C). The first ignition increment where occurs the laser ignition in the first stage of the detonator is loaded with micronized HMX mixed with an optical dopant. Experimental results show that, depending on the optical dopant mixed with HMX, the reproducibility of the detonator function time can be kept on a temperature range more or less extended, especially at high temperatures. So, ultrafine aluminium powder is observed much more efficient than carbon black to master this time reproducibility.