A large anisotropy of the electron distribution function in plasma production with prepulse-controlled high power KrF laser

A large anisotropy of the electron distribution function (EDF) was observed in high density plasma. The plasma was created by a 2-ps TW KrF laser syst em in which a prepulse energy was well controlled with a saturable absorber . The observed electron density at the emission area with He-like F ions wa s 0.7-1.5 x 10(22) Cm-3. A 90 degrees deflection time by electron-ion colli sions was calculated to be two orders of magnitude smaller than the laser p ulse duration. Even with this high collisionality, the anisotropy of EDF wa s driven by the laser field and was maintained. That means the anisotropy w ill become a parameter instead of temperature in the high density plasma wh ich was far from the equilibrium state. The energy transfer process will be discussed with these new measurements in future. (C) 1999 Elsevier Science S.A. All rights reserved.