Progress in double-shell gas puff z-pinches

An experimental study of high current (3–15 MA), high fidelity (multiple atomic number) and long implosion time (100–200 ns) gas puff loads using the 1–2–3–4 cm double-shell gas puff is in progress at Titan/PSD. Results of experiments conducted on Double-EAGLE, Saturn, Decade Quad and the Z accelerators will be analyzed and presented. The principal observations are: (1) The overall pinch quality and radiative characteristics of all the argon double shell z-pinches are quite satisfactory. The Ar K-shell yields varies from the expected I⁴ scaling in the inefficient regime for 3 to 7 MA to I² scaling in the efficient regime from 7 to 15 MA. (2) On all experiments from 3–15 MA, selective seeding of the shells demonstrates that the hottest mass of the pinch originates from the inner shell. This suggests that mixing between the two plasma shells during their collision and final implosion is limited. (3) On the 15 MA Sandia Z accelerator, with a load mass of 0.8 mg/cm, the K-shell x-ray output reached 275 kJ in a 15 TW peak power, 12 ns pulse. The analyzed ion and electron densities reach 5 × 10¹⁹ and 1.0 × 10²¹ /cc and the highest electron temperature observed is up to 2.2 keV with a 2.0 keV continuum