Study on K-shell X-ray production of double-shellneon gas puff Z-pinch

Abstract

The main results of investigation on K-shell X-ray production of double-shell neon gas puff Z-pinch, driven by Qiangguang-I facility (1.6 MA, 70 ns), are reported. The exit radii of the outer and inner shells are 1.5—1.4 cm and 0.75—0.6 cm, respectively. Both shells have a throat width of 0.32 mm, while the ratio of the throat radii is 2.8 ∶1, to which the mass ratio would be approximately equal for identical plenum pressures. K-shell yield and peak power up to 7 kJ and 0.28 TW, respectively, for a 20 ns full width at half maximum pulse have been obtained with about 120 ns implosions, the load mass per unit length of which are estimated to be 60—70 μg/cm. Time-resolved X-ray images show that RT instability during the implosion stage has been well suppressed, resulting in a final pinch diameter compressed to less than 2.5 mm. The final implosion velocity exceeds 25 cm/μs. K-shell yields and peak powers are largely reduced with longer implosion time. For shots with lower mass, i.e. 28—63 μg/cm, the electron temperature inferred from time-gated K-shell spectra should be greater than 500 eV, implying an overheated plasma column being formed in the stagnation stage. While for shots with load mass of 72—80 μg/cm, time resolved electron temperatures are in the range of 300—400 eV. The inferred ion densities of the K-shell emitting region are in the range of (3—9)×1019 cm-3, which have been used to calculate the mass fractions that contribute to K-shell radiation. Those shots with near 7 kJ yields also have maximum K-shell emitting load mass (about 46 μg/cm).