Experimental results on imploding dynamics of aluminum wire array z-pinch and x-pinch loads driven by QG-I facility are presented. The generator, mainly consisting of a linear transformer driver (240 kJ, 2.4 MV, 1 Ils) and three sections of water coaxial lines, can deliver a 1.6 MA peak current, 60-70 ns 10%-90% rise time main pulse, with a pre-pulse of 100 kA amplitude, 200 ns duration, to z-pinch like loads. The pre pulse may explode the wires to form core-coronal plasma columns with much larger diameters than the initial values, before the arrival of the main pulse. Cylindrical (CWA) and double planar wire arrays (DPWA) consisting of 20-50 micron diameter aluminum wires, and 2-4 wire x-pinches loads consisting of 50-200 micron diameter wires, have been tested to check the variation of plasma dynamics under different global magnetic field topologies.Time-gated x-ray images reveal similar features for both 8-16-wire CWA and two-wire x-pinch loads, i. e. , formation of plasma streams perpendicular to the wire and quasi-periodic ally modulated structures along the wire with a wavelength of �1 mm. In the CWA configuration, spots and gaps formed al ternately on different wires seem to be azimuthally correlated in many shots, although the interwire gaps are several millimeter large. While in the two-wire x-pinch configuration, plasma streams ablated from the wires form extremely intense axial jets, which interact with both A-K electrodes and lead to other rapidly expanding plasmas towards the crosspoint. This structural evolution causes collapse of the initial "X" shape and formation of more distributed plasma loads. Implosions of DP WA appear to be dominated by fast moving spots on the outer wires, resulting in axial modulation and trailing mass distribution, as the case of CWA loads. These observations, as well as characteristics of K-shell x-ray production, will be compared to reported results from other I-M A facilities which provide different dr iven pulses.
The results of an experimental investigation of X -pinch performance on the 1-MA "QiangGuang-1" facility are presented. "QiangGuang-1" is a linear-transformer-driver-based low-impedance pulsed power machine which provides a peak current of 0.9-1.3 MA and a 10%-90% rise time of 50-60 ns. X -pinch loads with 2-32 wires of different wire materials (Al, W, and Mo) with wire diameters from 25 to 100 μm have been tested. The number and size of bright spots, timing of the first X-ray burst, X -pinch dynamics, and X-ray spectroscopy have been studied using a set of diagnostics with spatial and/or temporal resolution. A single bright spot obtained from a 30 × 25 μm W X -pinch produced 42 J (35 GW) in the 1-10-keV energy range. The smallest bright spot size (radiating > 1.2 keV) observed was about 70 μm. Linear relations between the timing of the first X-ray burst and the wire parameters (diameter and number) in W X -pinches were observed. A spatially large extreme ultraviolet plasma radiation region at the crossing point was typically observed. Al X -pinch plasma parameters were estimated from X-ray spectroscopy.Index Terms-Plasma diagnostics, pulse power, X -pinch, X-ray spectroscopy.
Experiments of the return current post installed X-pinches were carried out on the 1-MA "QiangGuang-1" facility with the purpose of understanding X-pinch characteristics under this setup and establishing X-pinch backlighting diagnostics for the wire-array Z-pinches. Different wire-array loads along with the two-wire 30 μm Mo X-pinch backlighter were tested. The X-pinches emit the X-ray radiation with the burst time variation of ± 4 ns and the bright spot size of ∼30 μm. X-ray backlighting shadowgraphy images of the over-mass and radiation-suppressed Z-pinch wire array were obtained.
X-pinch radiography experiments were carried out on the 1 MA QiangGuang-1 facility to investigate the wire core behaviors of the tungsten and aluminum planar wire array. An axial quencher and over-massed loads were used to suppress keV radiation from the planar wire array. Two-wire 30 lm Mo and/or 25 lm W X-pinches were used as backlighters. The x-ray point-projection images showed quite uneven characteristics of the dense wire cores and the current distribution in the linear array. For the W single planar wire array (SPWA), Wire core diameter profiles are likely to reveal that the initial current distributed inductively among the wires with the same diameter in the array, and both inductively and resistively among the wires with different diameters. For the Al SPWA, wires in different positions were in quite different ablation processes. No correlations of stratifications or plasma jets between adjacent wires were observed.
X-pinch experiments have been carried out on a 100 kA, 100 ns linear transformer driver stage recently built up. The X-pinches exhibited a source size of about 10 lm, a pulse duration of 3 ns, 3-5 keV radiation energy of 3.9 mJ, and a burst time jitter of tens of nanosecond with the 2-wire 8 lm W X-pinch load. The generator output current and the X-pinch characteristics depended on the X-pinch wire materials in the tests. X-ray backlighting images from the insects showed the significant phase-contrast effect.
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