Density measurements in exploding wire-initiated plasmas using tungsten wires

Abstract

Calibrated density measurements have been obtained of the coronal plasmas around exploding 7.5-40 m W wires carrying 15-120 kA per wire for 30-70 ns. X-ray radiographs of the exploding wire plasmas using 2.5-10 keV photons from a Mo wire X-pinch backlighter enabled measurements of areal densities of W ranging from 2ϫ10 17 /cm 2 , equivalent to 0.03 m of solid density W, to about 10 19 /cm 2 . The rapidly expanding ͑few mm/s͒ coronal plasmas surrounding the slowly expanding ͑Ͻ1 mm/s͒ residual wire cores have areal densities up to about 2ϫ10 18 /cm 2 . Single 7.5 m wires tested with 100 kA had as much as 90% of the initial wire material in the coronal plasma. Coronal plasma W number densities were estimated to be up to a few times 10 18 /cm 3 , while core W densities as low as a few times 10 20 /cm 3 were observed. With linear arrays of four ͑eight͒ 7.5 m wires carrying 30 kA ͑15 kA͒/wire, up to 35% ͑25%͒ of the initial W wire material was in the plasma around and between the wires at 46-48 ns after the current started. Preheating the wires to drive off adsorbed gases and hydrocarbons increased the W mass in the coronal plasma and made it more uniform then when wires were not preheated.

Nucleation Mechanism of Explosive Destruction of Conductors of High Energy Density

“…We derive the following expressions for phase pressures as a result of linearization of chemical potentials in Eq. (20) with respect to pressure in the neighborhood of point p s : ,…”

“…The logarithmic dependence of the parameter ξ on its arguments leads one to hope for attaining an acceptable accuracy for its estimation even if it is only the order of magnitude of these arguments or the range of its admissible values that are known. The data of a number of experiments were analyzed [14,[18][19][20][21][22][23][24] in order to estimate the parameter ξ. In so doing, it turned out that, in experiments with both high-melting and low-melting metals, the range of variation of parameter ξ is quite narrow and lies in the range from 32 to 41.…”

“…At the interface between two magnetically inactive media (liquid and gas) in which the electric field and current are directed normally to the interface, equilibrium is described by the equations [10] , (20) . (21) Here, the subscript l and g indicate liquid and gas, respectively.…”

Cross-point coronal plasma dynamics in two- and four-wire x-pinches

“…8,9 These hot spots are of great interest for their high energy density conditions and are used as a source for high energy radiography. 7,[10][11][12][13][14][15] Following the x-ray burst, plasma is rapidly evacuated from the central region, leaving a gap in the axial density profile which continually expands late in time. 7,13,16 Much of the research on x-pinches has been to characterize the implosion dynamics at the cross point, in order to more fully understand the x-ray generation mechanics.…”

Soft X-ray laser diagnostics of exploding aluminum wire plasmas

“…Maximization of the X-ray yield requires an understanding of all phases of the plasma. The new success at Sandia National Laboratories Z-machine in the production of thermonuclear neutrons [11] driven by such X-ray burst further encourages the study of thin wire explosions.Several recent studies of the dynamics of single wire explosions conducted utilizing hard X-ray shadowgraphy and optical laser techniques [13][14][15][16][17][18][19][20][21][22] have significantly increased the understanding of single wire explosions. The probing of exploding wire plasmas with soft X-ray lasers can potentially provide complementary information on the initial stages of the explosion, where the density is high.…”