DETONATION-WAVES IN PENTAERYTHRITOL TETRANITRATE

Fabry-Perot laser interferometry was used to obtain nanosecond time re solved particle velocity histories of the free surfaces of tantalum di scs accelerated by detonating pentaerythritol tetranitrate (PETN) char ges and of the interfaces between PETN detonation products and lithium fluoride crystals. The experimental records were compared to particle velocity histories calculated using very finely zoned meshes of the e xact dimensions with the DYNA2D hydrodynamic code. The duration of the PETN detonation reaction zone was demonstrated to be less than the 5 ns initial resolution of the Fabry-Perot technique, because the experi mental records were accurately calculated using an instantaneous chemi cal reaction, the Chapman-Jouguet (C-J) model of detonation, and the r eaction product Jones-Wilkins-Lee (JWL) equation of state for PETN det onation products previously determined by supracompression (overdriven detonation) studies. Some of the PETN charges were pressed to densiti es approaching the crystal density and exhibited the phenomenon of sup erdetonation. An ignition and growth Zeldovich-von Neumann-Doring (ZND ) reactive flow model was developed to explain these experimental reco rds and the results of previous PETN shock initiation experiments on s ingle crystals of PETN. Good agreement was obtained for the induction time delays preceding chemical reaction, the run distances at which th e initial shock waves were overtaken by the detonation waves in the co mpressed PETN, and the measured particle velocity histories produced b y the overdriven detonation waves before they could relax to steady st ate C-J velocity and pressure. (C) 1997 American Institute of Physics.