Investigation of regimes of wire array implosion on the 1MA Zebra accelerator

Abstract

Implosion of wire arrays was investigated at the 1MA Zebra accelerator by multiframe laser probing and gated x-ray self-emission diagnostics. Different regimes of implosion were observed in Al and Cu wire arrays. Implosion of Al loads with masses of 33–37μg∕cm produces a dense pinch 1–1.5mm in diameter. Strong instabilities are observed in the Z pinch at the time of stagnation. Implosion of “overmassed” loads produces a plasma column 3–4mm in diameter with a core. The plasma column does not collapse during the x-ray pulse. The core of the plasma column is not subjected to the kink instability and transforms to a chain of dense spots in the later stage. Different regimes of implosion were observed in Al 8×15μm loads presumably due to variations in the current pulse and load conditions. Observed regimes are compared to three-dimensional hybrid simulation of ideal and nonideal magnetohydrodynamics modes of implosion.

Radiation properties and implosion dynamics of planar and cylindrical wire arrays, asymmetric and symmetric, uniform and combined X-pinches on the UNR 1-MA zebra generator

“…This diagnostics [26] included a five-frame laser probe of the target plasma in three directions separated by an angle of 22.5 . Two-frame shadowgraphy was used in two directions.…”

Dynamics of Mass Transport and Magnetic Fields in Low-Wire-Number-ArrayZPinches

“…In MAGPIE experiments, loads with up to 64 wires are imploded from the same diameter as the Zebra experiments due to the longer current rise times and higher accumulated energy available for experiments. Prior to implosion, jets from the wires in MAGPIE experiments display an axial period of 0:5 mm [8], similar to Zebra experiments [10]. Implosion in MAGPIE begins in the same manner as in Zebra experiments, with asymmetric ablation of the wire cores resulting in breaks and bubbles accelerating to the axis (Fig.…”

“…The delay between the first and the last bubbles reaching the axis may be responsible for the duration of the rising edge of the generated x-ray pulse. Indeed, the rise time of the x-ray pulse in 8-wire Al arrays is 15-25 ns on the Zebra generator [10]. The main x-ray pulse begins when bubbles bring material and kinetic energy to the precursor.…”

“…Plasma diagnostics include five-frame laser probing of the Z pinch in three directions [10]. Four frames of the shadowgraphy cover two probing directions.…”

Generation of shear flow in conical wire arrays with a center wire

“…The plasma dynamics were observed using multi-frame shadow imaging (Ivanov et al 2006) with a 532 nm wavelength, 150 ps diagnostic laser. In addition, Faraday rotation images were also taken to qualitatively assess the presence of an azimuthal magnetic field inside the wire array.…”