KrFレーザにおける紫外線予備電離電子密度のガス分圧率依存性

抄録

The Behavior of electrons produced by UV preionization is investigated in mixtures of helium/krypton and helium/fluorine. The concentration of krypton and fluorine is varied in the range of 1 to 20% and 0.05 to 0.3%, respectively. Excimer laser output is obtained for He/Kr/F₂=97.8/2/0.2%. In the mixtures of helium/krypton, electron density decreases with the increase of krypton concentration, because the DV light is absorbed by the krypton in a space between UV source and electron detection electrodes. After few microseconds from the initiation of an arc discharge for the preionization, the number of electrons decreases owing to the absorption of UV photons with the krypton and the electron attachment by the fluorine. It is found in the case of helium/fluorine gas mixtures that the preionized electron density is inversely proportional to the fluorine concentration owing to the attachment. For the laser gas mixtures, the electron density becomes lower by a rate of one-tenth of that of helium/krypton and helium/fluorine mixtures. The lower electron density is caused by the UV absorption by the krypton and the attachment. It is discussed that the increase of the electron density brings a larger laser energy due to the production of a stable pumping discharge for the laser.