The role of discrete plasma initiation sites in the high-intensity laser irradiation of surfaces

The total impulse delivered to solid surfaces through irradiation by CO2 lasers of intensity greater than 107 W/cm2 and pulsewidth of order 10−5 sec agrees well with theories which invoke the ignition of laser-supported detonation waves whose pressure scales on the 2/3 power of laser intensity, while the measured peak pressure under the irradiated area scales much more strongly with intensity. It is shown that these seemingly contradictory results may be reconciled through a model in which detonation waves are formed from discrete initiation sites whose size distribution determines the peak pressure scaling.