Monochromatic X-ray self-emission imaging of imploding wire array Z-pinches on the Z accelerator

• Published in: IEEE transactions on plasma science Vol. 34; no. 2; pp. 213 - 222
• Main Authors: Jones, B., Deeney, C., Coverdale, C.A., Meyer, C.J., LePell, P.D.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-04-2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acceleration; Accelerators; Arrays; Cameras; Chromium; Copper; Detectors; Emissions; Exact sciences and technology; Imaging; Implosions; Instruments; K-shell radiation; Magnetic confinement and equilibrium; Magnetohydrodynamics; Microchannel; Mirrors; Nonhomogeneous media; nonhomogenous media; Optical imaging; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma diagnostic techniques and instrumentation; plasma measurements; plasma pinch; Scientific imaging; Theta pinch; Wire; X-ray and y-ray measurements; X-ray and γ-ray measurements; X-ray imaging; X-ray measurements; X-ray production; X-rays; Magnetohydrodynamics; Soft X radiation; plasma pinch; Bremsstrahlung; Implosions; X-ray sources; K shell; Experimental device; Experimental study; Wire; plasma measurements; X-ray production; X-ray imaging; nonhomogenous media; Plasma diagnostics; X-ray measurements; Plasma magnetohydrodynamics; Longitudinal pinch; K-shell radiation
• ISSN: 0093-3813; 1939-9375
• DOI: 10.1109/TPS.2006.872177

A monochromatic X-ray self-emission imaging diagnostic has been developed for the Z accelerator, which drives 20 MA in 100 ns to implode wire array Z-pinches, generating up to 250 TW of soft X-ray radiation. This instrument reflects eight pinhole images from a flat Cr/C multilayer mirror (MLM) onto a 1-ns time-resolved microchannel plate detector. The MLM reflects 277-eV photons with /spl sim/5-eV bandwidth and 20% peak reflectivity, and an aluminized parylene filter shields the detector from visible light. High-energy bremsstrahlung X-rays do not follow the reflected beam path, and so the background on the shielded detector is reduced compared to a standard pinhole camera. The MLM-reflected images offer low-photon-energy spectral resolution that filtration alone cannot, yielding high-quality images of the final stages of the Z-pinch implosion. Initial data on Z from a Cu wire array will be presented. Observed phenomena include implosion instabilities, zippered implosion of a piston onto a precursor column during the onset of stagnation, accretion of trailing colder mass during the X-ray pulse, and cathode reemission. The inferred implosion velocity is significantly less than thin-shell implosion model calculations, and well below what is required for efficient Cu K-shell radiation. Instability-dominated, bright-spot Cu K-shell emission is seen on a second adjacent eight-frame filtered pinhole camera that is in the same beamline.