J.-C. Gauthier, et al.
J. Phys. IV France 133 (2006) 1155-1159
Production of photoionized plasmas by the interaction of short FEL pulses with gaseous mediumV.Yu. Bychenkov1, D.V. Romanov2, S.I. Samarin3, N.A. Voronina3, W. Rozmus2, C.E. Capjack4 and R. Fedosejevs4
1 P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow 119991, Russia
2 Theoretical Physics Institute, University of Alberta, Edmonton T6G 2J1, Alberta, Canada
3 Russian Federal Nuclear Center, All-Russian Research Institute of Technical Physics, Snezhinsk, Russia
4 Department of Electrical Canada
Photoionized plasmas created in the interaction of short linearly polarized x-ray pulses with a gaseous medium are characterized and discussed in the context of experiments with femtosecond FEL pulses. The electron distribution function in these plasmas remains strongly anisotropic due to unique plasma atomic and kinetic processes until such time that electron-electron collisions are able to thermalize the distribution. The relaxation of nonequilibrium photoionized plasmas is studied by using Monte-Carlo simulations which account for photoabsorption, elastic electron collisions, impact ionization of atoms, and atomic excitations. The dispersion properties and instabilities of a fully ionized x-ray-produced plasma is described. The photoionized plasma is found to be subject to a two-stream type of instability which has a growth rate comparable in magnitude to the plasma frequency and is therefore expected to have a dramatic effect on the evolution of the plasma. We performed 3D PIC simulation of this photo-ionization two-stream (PITS) instability. A model for electromagnetic field generation and emission resulting from the interaction of a short x-ray laser pulse with a gas jet is proposed. This is used to explore the effect of the thermo-EMF at the edge of a plasma characterized by an anisotropic electron energy distribution which results from the photoionization of the gas. Terahertz pulse generation from the plasma is predicted.
© EDP Sciences 2006