The aim is to realize a soft X-ray laser pumping by fast capillary discharge. Lasing is expected on Balmer α transition of C⁵⁺ ion. The three-body recombination process is judged as elementary process of pumping. Soft X-ray spectroscopy is used as a capillary plasma diagnostic tool. Experimental and computer studies of plasma created in initially evacuated polyacetal and polyethylene capillaries have been done.
Our experimental setup [3] is composed of capillary discharge system and the diagnostic one. Electrical energy is stored in 24 knob capacitors of 2.5 nF each mounted in serial-parallel to capillary. Total capacity is 15 nF. Maximum voltage is 40 kV. Capillaries with 1.1 mm diam. and 56 mm length are used. Emission spectra in the wavelength region from 10 nm to 26 nm have been measured by means of the JOBIN YVON monochromator PGM-PGS 200 and Reflex, Ltd. BICCD camera RXBIC 512c in many repetitive shots.
Space-time dependences of plasma electron density and temperature have been calculated by means of MHD code [1]. Time profiles of selected lithium-, helium- and hydrogen-like carbon and oxygen ion populations have been evaluated by means of the FLY code [2]. Time resolved and time integrated emission spectra are expressed by means of the subprogram FLYSPEC separately for the carbon and oxygen.
The measured time integrated spectra for polyacetal and polyethylene capillaries correspond properly to the spectra resulting from the computer simulations.

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