Current-sheath oscillations and reactivity in focused discharges

Summary form only given. Oscillations of the current sheath driving force J_/spl times/B_/sub /spl theta// and of its propagation velocity v strongly bear on the maximum energy E, of the accelerated ions and on the D+D neutron yield Y in the PF pinch. Magnetic probe (MP) signals |dB/sub /spl theta///dt| provide the amplitude /spl Delta/v of the velocity oscillations during the radial implosion phase of the current sheath. The relative amplitude /spl Delta/v/v=/spl Delta/|dB/sub /spl theta///dt|/[|dB/sub /spl theta///dt|]=25%/spl plusmn/15% of the oscillations and their period T=35 ns/spl plusmn/17 ns, determined via MP with greater accuracy than ever before, agree with previous measurements via (i) long-exposure-time schlieren imaging and (ii) secondary peaks of the electrode current (I) signal |dI/dt| from a Rogowsky coil between the electrode back plates. If the oscillation of v has an amplitude minimum at t=t/sub 0/-T, where t/sub 0/ is the time of the sharply defined peak in the |dI/dt| signal, Y is usually higher by a factor=4 than the typical value Y/sub av/ from discharges where this phase condition is not satisfied.