Enhanced stability and neutron production in a dense<i>Z</i>-pinch plasma formed from a frozen deuterium fiber

We have formed dense Z pinches from frozen deuterium fibers ranging in diameter from 80 to 125 \ensuremath{\mu}m and at peak currents of up to 640 kA. The pinch remains stable for the entire 130 nsec of the current rise. This anomalously long stable period corresponds to about 100 MHD growth times. As soon as the current peaks, i.e., when dI/dt=0, the pinch goes rapidly m=0 unstable and produces nearly ${10}^{12}$ neutrons in a 30--60-nsec-wide pulse. The instability occurs only at dI/dt=0 and is independent of either the current magnitude or the time to peak.