We present detonation wave profiles measured in two TATB based explosives and two HMX based explosives. Profiles were measured at the interface of the explosive and a Lithium-Fluoride (LiF) window using 1550 nm Photon Doppler Velocimetry (PDV). Planar detonations were produced by impacting the explosive with a projectile launched in a gas-gun. The impact state was changed from shot to shot in order to produce varied distances to detonation. In this way, we tuned the support of the Taylor wave following the Chapman-Jouget (CJ) or sonic state. Profiles from experiments with different support should be the same between the Von-Neumann (VN) spike and CJ state and different thereafter. Comparison of profiles with differing support, therefore, allows us to estimate reaction zone lengths. For the TATB based explosive, a reaction zone length of approximate to 3.9 mm, 500 ns was measured in EDC-35, and a reaction zone length of approximate to 6.3 mm, 800 ns was measured in PBX 9502 pre-cooled to -55 degrees C. The respective VN spike state was 2.25 +/- 0.05 km/s in EDC-35 and 2.4 +/- 0.1 km/s in the cooled PBX 9502. We do not believe we have resolved either the VN spike state (> 2.6 km/s) nor the reaction zone length (<< 50 ns) in the HMX based explosives.
