Electron energy deposition in an electron-beam pumped KrF amplifier: Impact of the gas composition

Calculations for electron deposition in electron beam generated KrF laser at atmospheric pressure have been performed. The impact of the Ar/Kr/F-2 gas mixture on the electron energy distribution function, electron density, and mean energy, energy per electron-ion pair, attachment, dissociation, excitation, and ionization rates have been investigated. The F-2 abundance controls the low energy (less than or similar to9 eV) component of the distribution function, while both the fluorine and krypton mole fraction affect the distribution in the midenergy domain (9 to similar to25 eV). Consequently, the F-2 attachment rate coefficient varies with the F-2 mole fraction (x(F2)) such that the electron density scales as 1/x(F2)(0.7). The rate coefficient for direct dissociation of F-2 is smaller than for attachment but the former contributes more to the total power dissipation (similar to8% at x(F2)=0.01). The excitation-to-ionization ratio for Kr is not constant, as generally assumed, but increases by a factor of two with a decrease in either the Kr or F-2 abundance. Combining the former and present investigations leads to a set of fitting formulas to be used in beam kinetics codes for various collision rates as a function of both the electron beam power density and the composition. (C) 2002 American Institute of Physics.