Pulse laser ablation characteristics of quartz diffusion plate and initiation of PETN - Glass fragment size distribution and surface roughness dependence -

This paper describes an investigation of laser-induced initiation of PETN powder based on the pulse laser ablation of ground glass surface previously reported by our group. In this study, we have chosen diffusion plates made of quartz as a ground glass specimen with several different surface roughnesses instead of commercial ground glass adopted in the previous study. This is due to the fact that laser ablation characteristics usually depends on the material. We have found that cloud of glass fragments is generated, when ground glass surface is laser ablated through the glass plate focused from rear side. In this study, we found further properties of this striking ablation phenomena; for example, (i) size distribution of produced glass particles have almost no dependence on the initial surface roughness, (ii) generated number of particles by ablation increases with increasing surface roughness, (iii) particle generation continues more than 10 μs after laser ablation, etc. A series of initiation experiments of a small amount of PETN by pulse laser ablation of ground glass with different surface roughness has been performed. We studied the dependence of initiation sensitivity on the laser fluence. It is found that within tested conditions, threshold laser fluence is around 10 J cm ^-2. For initiation experiments by laser fluence lower than this value, probability of initiation decreases, and initiation delay time after ablation elongates appreciably irrespective of the initial surface roughness, indicating that the initiation is governed almost solely by the magnitude of kinetic energy of generated glass particles.