Initial Distribution of Gas Density as a Method to Control the Radiation Characteristics of a High-Current Pulse Discharge*

The plasma pinch (current I$_{max}$ = 250 kA, rise time T = 1 $\mu$s) on the basis of a gas jet with special density distribution is described. The gas jet was produced by means of a pulse gas valve with a nozzle that was capable of forming a gas flow with a maximum density in the center of the discharge gap. The diagnostic techniques involved measurements of the discharge current and the pinch voltage, the size of the radiation area and the X-ray intensity. The experiments with different gases (Ar, Ne and N) showed that as a result of the discharge at this gas distribution the hot plasma area of ``point'' form (its typical size is 100 $\mu$m and life-time 3-5 ns) arises in the middle of the discharge gap. This area is the X-ray source of energy of quanta 50-5000 eV. The radiation spectrum depends on the gas type. The experimental results are presented.