X-PINCH PLASMA DYNAMICS STUDIED WITH HIGH TEMPORAL RESOLUTION DIAGNOSTICS
The X-pinch plasma produces extreme material conditions that make it interesting both as a high-energy-density plasma and an x-ray source for imaging. These extreme conditions include high densities (near solid density, 10^23 ions/cm^-3 for Mo), high temperatures (above 2.5 keV for Mo), high energy densities (up to 10^12 J/cm^3), high x-ray power densities (up to 10^22 W/cm^3), small source sizes (which can be less than 1 micron in diameter), and short time scales for the x-ray radiation (less than 100 ps). These extreme conditions are difficult to produce in a laboratory setting and even harder to study. The X-pinch plasma is produced by driving a high current (100-500 kA, 100 ns FWHM pulse for our experiment) through two or more wires that cross at a point forming an "X." A magnetically driven z-pinch forms near the cross point allowing the X-pinch to reliably reproduce the conditions given above. As such, we present a range of experiments designed to study the conditions produced in the X-pinch plasma. Until recently many of the diagnostics used to study the X-pinch have not had the resolution (spatial or temporal) necessary to determine the actual size or duration of the X-pinch x-ray source. We present experimental results showing the temporal extent of the x-ray radiation produced by an X pinch using an x-ray streak camera with better than 10 ps resolution. We also present experiments designed to study the temporal and spatial relationship of the two different radiation sources (thermal and energetic-electron-generated) observed from an X pinch using a filtered diode array. In addition, we studied the plasma dynamics using both a multi-channel 150 ps, 532 nm (Nd:YAG) laser backlighting system and x-ray radiography (using an X pinch as an x-ray source). We correlate the observed plasma parameters (implosion and explosion rate, neck diameter, axial jet propagation speed, and coronal plasma axial modulation wavelength along the X-pinch legs) to wire material.
X pinch; plasma; x-ray
Dissertation or Thesis