Study of micro-pinches in wire-array Z pinches

Abstract

Bright and hot areas with a high plasma density and temperature are observed in all kinds of Z pinches. We studied bright radiating spots produced by micro-pinches in cylindrical and planar wire-arrays at the 1 MA Zebra pulsed power generator using an x-ray streak camera synchronized with laser diagnostics, x-ray time-gated pinhole camera, and spectroscopy. Hot spots with extremely dense and relatively hot plasma arise during the collapse of the micro-pinches. These hot spots radiate a continuum spectrum with energy >2.5 keV. Typical micro-pinches in Al wire arrays generate x-ray bursts with durations of 0.4-1 ns in the soft x-ray range and 0.1-0.4 ns in the keV range. UV two-frame shadowgraphy shows spatial correlation of hot spots with the collapse and explosion of micro-pinches. Micro-pinches typically occur at the necks of the Z pinch, but can demonstrate a variety of parameters and different dynamics. An analysis of x-ray streak images shows that micro-pinches can generate >20% of the x-ray energy in some types of wire-array Z pinches. V C 2013 AIP Publishing LLC. [http://dx.

Temporal characteristics and radiative properties of uniform Mo and combined with Al triple planar wire arrays

“…The TGPH images indicate many random bright spot formations for both > 1.0 and > 3.0 keV images, which correlate well with the random burst nature of the XRD and PCD signals. The bright spot formations have been shown in other wire array configurations[7][8][9][10] to correlate with Rayleigh Taylor instabilities which are seeded by the development of quasi-periodic gaps in the wire cores at the start of the implosion phase, that may occur also in these experiments.Next inFigure 2are the signals and time-gated spectrometer (TGSP) images from Mo/Al/Mo (1968).The TGSP[11] was implemented to understand how K-shell Al and Mg radiate in time and utilized a potassium hydrogen phthalate (KAP) crystal (2d = 26.63 Å) which allowed for viewing of wavelengths between 6.2 and 11.0 Å, wide enough to cover most of K-shell Al and Mg spectra. Bio-max MS Kodak x-ray film was implemented in this work.…”

Study of magnetic fields and current in the Z pinch at stagnation

“…18,24 Necks and micropinches with a diameter 60-300 lm are well seen in wire-array Z pinches with UV laser diagnostics. 16,24 A simple estimation shows that necks could generate the magnetic field B > 10 MG if, for example, 0.5 MA current flows in the neck 0.2 mm in diameter. From another side, authors of paper 12 claim a "disappearance" of current in the neck on the fiber Z pinch at 0.1 MA current.…”

“…A three-channel polarimeter with shadowgraphy, the Faraday channel, and differential air-wedge interferometer 21 with three UV charge-coupled device (CCD) cameras was described elsewhere. [22][23][24] An UV polarizer was inserted in the laser path before the vacuum chamber to create a beam with a high-contrast linear polarization. A crystal wedge was installed at the output window for angular separation of the shadow and Faraday rotation channels.…”

Visualization of the magnetic field and current path in Z-pinch and X-pinch plasmas

“…The fourth x-ray frame (d) in Fig 2(e) is taken at the same time as the laser images and shows a wide Z pinch with smaller intensity of x-ray radiation in the photon energy range > 1 keV. A white arrow in the shadowgram (b) points to the break in the stagnated Z pinch which may be formed by the explosion of the hot spot [13]. A possible current path cannot be derived from the shadowgram and interferogram in Fig.…”

“…This image shows that current switches to another route after a break formed in the stagnated pinch. The break is, presumably, produced by the collapse and explosion of the micropinch on the Z-pinch [13]. Micropinches are typical for implosions of cylindrical loads at the Zebra facility [8].…”