Current filamentation in discharge-excited F2-based excimer laser gas mixtures

Discharge instabilities in x-ray preionized F2-doped excimer laser gas mixtures are investigated using an intensified charge coupled device camera with a gating time of 300 ps. In contradiction with earlier theories and observations, it is found that the discharges in He/F2 mixtures are homogeneous only at very low concentration of F2 0.025%. We present experimental results, which prove that in He/Kr/F2 mixtures the appearance of discharge filaments is coupled with the presence of F2 rather than Kr.