Study Of Capillary Discharge Plasmas For Soft X-Ray Recombination Lasers

We have proposed the development of compact and efficient soft X-ray recombination lasers based on a capillary discharge. This laser scheme utilizes a fast discharge pulse for creating a highly ionized plasma with good axial uniformity in a capillary structure. Rapid plasma cooling caused by electron heat conduction to the capillary walls and by plasma radiation is expected to cause large recombination rates and soft X-ray amplification. Here we report results of the spectroscopic study of the soft X-ray emission from high power density poliethilene capillary discharges. In 1 mm diameter capillaries excited by the 100 ns current pulses from a compact table-top discharge, the intensity of CVI transitions is dominant for excitation energies above 20 J, and the degree of ionization of the plasma continues to increase up to the maximum energy investigated, 60 J. Intense Balmer Alpha emission from hydrogenic carbon is observed in the spectra shown below, corresponding to the axial emission from a 1 mm in diameter, 1 cm long capillary excited by a 45 J pulse. The maximum intensity of the 18.2 nm line of CVI occurs 35-50 ns after the peak of the current pulse, and the electron density is estimated to be approximately 1 10
¹⁹
cm
^-3
from the spectral line broadening displayed by high members of the CVI Balmer series.