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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