Optical diagnostics on dense Z-pinch plasmas

摘要

A novel ''point-diffraction'' interferometer has been implemented on the Los Alamos Solid Fiber Z-Pinch experiment. The laser beam is split into two legs after passing through the plasma. The reference leg is filtered with a pin-hole aperture and recombined with the other leg to form an interferogram. This allows compact mounting of the optics and relative ease of alignment. The Z-Pinch experiment employs a pulsed-power generator that delivers up to 700 KA with a 100ns rise-time through a fiber of deuterium or deuterated polyethylene (CD(sub s)) that is 5-cm long and initially solid with radius r(approx)15(mu)m. The interferometer, using a (triangle)t(approx)200ps pulse from a Nd:YAG laser frequency doubled to (lambda)=532nm, measures the electron line density and, assuming azimuthal symmetry, the density as a function of radial and axial position. Calculations predict Faraday rotations of order (pi)/2 for plasma and current densities that this experiment was designed to produce. The resulting periodic loss of fringes would provide the current density distribution.