Transition from Regular to Mach Reflection of Shock Waves in Laterally Colliding Laser-Produced Plasmas

Shock wave reflections in laterally colliding laser-produced aluminum plasmas at 10(-1) and 1 mbar argon ambient has been studied using fast imaging technique. In 10(-1) mbar pressure regime, the two shock fronts interact to form an intense interaction region. In the case of 1 mbar pressure regime, at early stages of plume expansion, individual shock fronts interact to form a collision front resulting in regular reflection of shock waves. At later times, the collision front split and a channel-like structure was observed and the width of the channel increases with time which is the cause of Mach reflection of shock waves. Incident angle and Mach stem length were measured from ICCD images, and it is found that Mach stem length increases with angle of incidence and time delay. Thus, the transition from regular reflection to Mach reflection of shock waves is reported in this paper.