Return current in large aperture electron-beam-excited KrF lasers

Results from a model for an e-beam excited KrF laser are presented, and the effects of return currents on plasma parameters and laser performance are discussed. The author finds that the joule heating caused by the return currents, expressed as a fraction of total power deposition, increases with increasing halogen density, increasing aperture size, increasing pressure, and decreasing power deposition. The return current electric field causes a decrease in the rate coefficients for dissociate recombination and attachment and an increase in the rate of multistep ionization. As a result, the electron density near the foil increases by more than tens of percentage points. The laser intensity in those regions also increases. These effects are practically important in lasers having apertures exceeding 1 m