GAS-CONTACT COOLING FOR QUASI-STATIONARY OSCILLATION OF THE XUV LASER RECOMBINING PLASMAS

Oda,T., Takiyama,Y., Kamiura,Y., Fujita,T., Sato,K., Ishii,K., Akiyama,R., Otsuka,M., Furukane,U., Sakai,H., Ono,K., Oomori,T.: 1993, 'Short wavelength and X-ray lasers'.

To produce a rapidly cooled recombining plasma for generation of an XUV laser beam, gas-contact cooling has a high potentiality. The approach has two advantages : One is that a stationary population inversion is possible, and the other is a rapid cooling due to inelastic collisions between electrons and atoms. The first experiment on gas-contact cooling was carried out in a magnetically confined stationary plasma column of a TPD-1 device in IPP, Nagoya. It was demonstrated that stationary population inversions were produced between the lower excited levels of the He II when a He plasma was brought into contact with a helium gas. The gain per unit length in the medium of population inversion, however, was quite low because the electron density was relatively low and introduced helium gas pressure was also low. We describe a numerical investigation of a He recombining plasma, rapidly cooled by hydrogen gas-contact, to show the possibility of a stationary laser oscillation of the He II 164 nm line, and we also present measurements of population inversion of He I and II lines in the magnetically confined plasma (TPD-1 in IPP, Nagoya) which is brought into contact with hydrogen gas puffed by a fast-acting valve, and also in a Z-pinch produced plasma. We display the numerical investigation performed on the basis of a collisional-radiative (CR) model and energy equations for electron. Experiments in the TPD-1 plasma and in the Z-pinch plasma are presented.


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