Effect of the axial magnetic field on a radiating z-pinch plasma

Summary form only given. Effect of the axial magnetic field B_z on z-pinch implosion was reported earlier in the Ref. [1-4]. The present research focuses on a systematic study of the effect of the B_z on the total radiation of a bismuth z-pinch and the evolution of the z-pinch instabilities. The experimental setup employs a z-pinch configuration with a preembedded, nearly uniform axial magnetic field of up to 1.35 T. The implosion is driven by a capacitive pulse generator (V=70 kV, C=3.2 μF) capable of storing 7.84 kJ of energy and producing a load current up to 450 kA with a rise time of 450 ns. To judge the stability of the shell implosion, we performed 3-ns time-gated imaging of the visible pinch radiation. A Bi-metal-puff jet [5,6] is injected into a 10-mm anode-cathode gap through a 5-mm diameter collimator. Start diameter of the current sheath exceeds 3 cm. The Bi-metal-puff has a near-normal density distribution. We speculated that the RT instabilities are mitigated with the help of mechanism described in Ref. [7,8]. Note, that the pinch compression has not a strong axisymmetric instabilities during the implosion phase owing to the large start current layer diameter. During the stagnation phase, at B_z=0 we observed the strong MHD instabilities, the maximal pinch radiation was equal to 1.9 kJ (bolometer). At B_z=0.3 T the amplitude of the MHD instabilities decreases slightly during the stagnation phase. While the radiation energy peaked at B_z =0.3 T and it is equal to 2.8 kJ (36 % from the storage energy). At B_z =1.35 T the radiation falls up to 0.25 kJ; the plasma column has the diameter about 0.5 cm and it was stable during the stagnation phase. We compared our data with the results of the 1D RMHD simulation.