Density Profile Steepening by the Ponderomotive Force of an Intense Picosecond Laser

The high-density plasmas produced by the interaction of short-pulse lasers with solid targets have been proposed as candidate coherent x-ray sources [1]. Large absorption of laser light and rapid cooling of the plasma—both of which are required for this scheme to work—depend strongly on the evolution of the electron-density profile during the laser pulse. We report experimental and theoretical results indicating that when the quiver energy of the electrons exceeds their thermal energy, the ponderomotive pressure of the laser significantly modifies the density profile.