1995 Volume 79 Issue 11 Pages 672-677
The dependence of 253.7 nm emission efficiency on the discharge tube radius in argon-mercury-mixture gases is investigated using the simulation model for a positive column. The calculated waveforms of electric field, 253.7nm emission, electron energy and electron density show good agreement with the measured waveforms, respectively, for 50 Hz and 50 kHz operations. The obtained results are as follows: (1) The 253.7 nm emission efficiency takes a maximum with the tube radius under the constant discharge power and the constant mercury atom density condition, even though the dependence of emission efficiency on the discharge tube radius is rather weak except for the small radius region.(2) At the large radius region, the effective radiative decay-time increases with the radius. The density at radiative excitation level also decreases with the radius due to the decrement of electron energy and electron density. Thus, 253.7 nm emission decreases even if the discharge volume is increased.(3) At the small radius region, the increasing rate of the density at radiative excitation level begins to decrease with the radius, since the excited atoms at the triplet levels are excited to higher levels. Thus, 253.7 nm emission decreases with a decreasing discharge volume.