Picosecond X-Ray Sources

Abstract

Publisher Summary The chapter provides an overview of short-wavelength light pulses with a duration of less than a picosecond, which can be produced by focusing high-intensity, ultrafast laser pulses onto a solid. The intense, ultrafast laser pulses are absorbed by plasma formed inside the surface of the solid before ablation occurs. The resulting short-wavelength emission spectrum is characteristic of a high-temperature, short-lived, high-density plasma. In a study mentioned in the chapter, the importance of using low prepulse energy for the production of short pulse x-rays from laser-produced plasmas was demonstrated. Energy deposited before the arrival of the short pulse can cause ionized material to be ablated, leading to the formation of lower density plasma in front of the solid surface. Ultrashort laser pulse absorbs in that lower density region and can lead to relatively long x-ray emission times. The short-pulse laser is coupled into solid or near-solid density plasma with an associated high, metal-like reflectivity. At high electron densities, ionization depression reduces the number of bound levels to the first few excited levels and Stark broadening is severe; this can lead to rapidly varying line broadenings. Continuum emission is expected to dominate until the plasma cools and expands. Resonance line emission from long lived states has been observed to radiate for tens of picoseconds longer than the short pulse integrated emission observed using the streak camera.