Study of dynamics of hot spots in wire-array Z-pinches

Summary form only given. Hot spots with a high plasma density and temperature spontaneously arise in all kinds of Z-pinches with currents from 0.1 to 4 MA. Instabilities generate bright and hot spots with the enhanced electron temperature and density. The electron temperature of 9 keV was measured in the hot spot of the X-pinch with current of 5 MA. The formation of hot spots can be interpreted as a result of the collapse of the Z-pinch due to the radiative loss of energy and plasma flowing out of the spot. Hot spots carry current and can generate strong MG magnetic fields in the Z pinch. Hot spots contribute to the energy balance and neutron yield in Z pinches. In our experiments bright radiating spots were observed in small diameter cylindrical and planar wire-arrays. Bubble-like implosion in wire arrays initiates the formation of necks on the pinch which produce hot spots. We investigated hot spots at the 1 MA Zebra generator using synchronized x-ray streak camera, laser diagnostics at 266 and 532 nm, and x-ray time-gated pinhole camera. Hot spots in Al wire arrays generate x-ray bursts with durations of 0.4-1 ns in the soft range and 150-400 ps in the keV range. Continuum radiation with photon energy > 2.5 keV was observed in hot spots generated in Al Z pinches. UV two-frame shadowgraphy shows spatial correlation of hot spots with necks on the pinch. An analysis of x-ray streak images shows that a collapse of a single hot spot can generate >10% of radiated x-ray power of the 1 MA Z pinch.