Spatial and Temporal Characteristics of Jets in X-Pinch Plasmas

Summary form only given. Radiographs of X-pinches driven by ~400 kA current pulses show jets of matter extending along the anode-cathode axis from both sides of the crossing point of the X pinch wires. The jets, formed by ablation of material from the heated wires of the X pinch, extend over a few mm of the 15 mm anode-cathode gap and persist over tens of ns during the X-pinch implosion. Spatially resolved spectra of Ti X-pinches show that while emission from highly ionized Ti is localized in a 10-100 mum region near the crossing point of the wires, K-alpha emission from Ti I to Ti XIII extends over several mm on the anode side of the hot, dense central portion of the X-pinch plasma. Streak camera measurements show ns-scale bursts of K-alpha emission following the sub-ns bursts of X-ray emission from H- and He-like Ti. We present spectroscopic modeling of the spatially and temporally resolved K-alpha emission measurements, giving ionization balance and electron temperature estimates resolved in space and time. We show that the electron energies required for excitation of inner-shell K-alpha transitions from low charge states of Ti are much greater than the thermal temperatures that can support such charge states, indicating that beams of hot electrons play an important role in the X-ray emission from the jets