Optimization of double shell hybrid gas-puff with outer plasma shell for efficient generation of K-shell radiation in the microsecond implosion regime

Abstract

Studies of Z-pinch plasma as X-ray source were carried out on the GIT-12 generator (4.7 MA, 1.7 μs) in the IHCE SB RAS, Tomsk. The main purpose of the research was optimization of load parameters for efficient generation of the argon K-shell radiation in the microsecond implosion times. A new type of a Z-pinch load, a hybrid gas-puff with an outer plasma shell, was tested. The inner argon shell was actually a solid gas jet on the axis of the system with a small initial diameter. An outer deuterium shell played the role of an implosion stabilizer for the inner gas jet. The third component was the outer plasma shell that provided the initial conductivity. The combination of deuterium shell together with the outer plasma shell has proved its effectiveness in past experiments providing stable implosion at times of the order of a microsecond. In these experiments, the diameter of the inner argon jet was 20 mm, the diameter of the annular deuterium shell was 81 mm, and the outer plasma shell was generated by 48 plasma guns located at the diameter of 350 mm. To increase the K-shell radiation yield, density profile of Z-pinch matter was changed. K-shell radiation yield increased when the matter of the central argon jet did not propagate from the central region to the periphery. As a result, K-shell radiation yield increased to 1.5 kJ/cm, and the power increased to 535 GW/cm at a peak implosion current of 2.8 MA. This radiation yield reached 70% of the theoretically predicted yield calculated by the two-level model. In our earlier experiments with double shell argon gas-puffs, the efficiency of the K-shell plasma radiation source was only 60%. Thus, we consider the hybrid gas-puff with outer plasma shell as a promising load for our further research of the K-shell radiation generation at microsecond implosion times.