Soft X-ray emission from a CO 2 laser-heated Z-pinch plasma

Abstract

We report results of soft X-ray measurements in which a high-power (10 10 –10 11 W/cm 2 ) CO 2 laser was used to heat a near critical density (<10 19 cm −3 ) helium Z-pinch plasma. Frequency-integrated X-ray data show that the unheated Z-pinch plasma is Maxwellian with a temperature of about 30 eV. During laser heating, the X-ray emissions were enhanced over the unheated emissions. Analysis of the experimental X-ray spectra indicate that the low-energy portion of the X-ray emission spectrum (up to 600 eV) is enhanced over the baseline 30 eV Maxwellian emissions. This result is consistent with an inverse bremsstrahlung-modified distribution which results when the plasma heating rate is more rapid than the collisional thermalization rate. These results suggest that it may be possible to enhance the soft X-ray yield of a plasma lithographic source with laser heating.