X-RAY GENERATION ENHANCEMENT FROM A LASER-PRODUCED PLASMA WITH A POROUS SILICON TARGET

X-ray generation enhancement from a laser-produced plasma with a porou s Si target is reported. For a porous surface formed on a Si wafer, th e self-reflectivity of a femtosecond pulse becomes considerably small. The observed energy penetration depth is 25-30 mu m, which is much la rger than the skin depth of solid density matter. Using a porous Si ta rget, the threshold of the pre-pulse intensity required for soft x-ray emission enhancement can be reduced. It also contributes to enhance t he pre-pulse effect, and soft x-ray generation enhancement ranging fro m 1.6 to 6.5 times is observed depending on the pre-pulse intensity. ( C) 1997 American Institute of Physics.