Vacuum Ultraviolet Emission from High Density Spark Discharges in Argon and Helium

The spectral radiant intensity (without imaging) is observed between 5000 A and 1250 A with gas pressures 1-8 atm in argon and 10-40 atm in helium. Tungsten and carbon electrodes with 1-mm gaps were used at breakdown voltages of 1.5-6.5 kV and C = 0.85 microF and L = 16.8 nHy. After reaching opacity and saturation within the visible range, the continuum radiation shifts toward shorter wavelengths with increasing voltage and gas pressure and reaches the intensity of the broad A(+), A(++), and He(+) lines. Saturation of spectral intensity and self-reversal of lines is observed; intensities at 1250 A may be higher by a factor of 25 than those at 5000 A. Mean gas temperatures of approximately 60,000 K in argon and 100,000 K in helium are determined from the spectral lines of the electrode vapor in the case of relatively low gas pressures and foremost transparent channels by means of the Norm-temperature method. Channel pressures and particle densities are ca culated from the channel expansion. Theoretical values of the continuum radiant intensity agree with the experimental results reasonably well.