Streaked visible-light spectroscopy measurements of aluminum wire-array z-pinches on COBRA

Streaked visible-light spectroscopy measurements are presented for aluminum (Al) wire-array z-pinch experiments on the 1-MA, 100-ns rise-time COBRA pulsed-power generator. For these measurements, a half-meter Czerny- Turner spectrometer was used in conjunction with the COBRA visible-light streak camera system. This allowed us to record visible-light spectra emitted from Al coronal plasma as a continuous function of time throughout the initiation, ablation, and implosion phases of the given wire-array z- pinch experiment. When using thick wires (~100-mum in diameter), the visible-band spectra observed consisted solely of continuum emission, which began at the moment of resistive voltage collapse. (Resistive voltage collapse occurs when coronal plasma first forms around the wire cores, and marks the transition from the initiation/resistive-heating phase to the ablation phase.) The continuum data collected are now being used to determine electron density. To determine electron density from this continuum data, an absolute calibration of the detection system was required. The details of these experiments and the absolute calibration technique are presented.