Inductance modulation effects on the PF reaction yield

Summary form only given. A variation of the interelectrode spacing as a function of the axial coordinate z is used to assess the bearing on the D+D neutron yield per pulse, Y, of the inductance [L(z) dl/dt] and of the resistivity [ldL/dt] term amplitude during the axial propagation of the plasma current sheet in the interelectrode gap of plasma focus discharges. Two funnel-shaped electrodes were assembled coaxially in a PF machine to replace the two Y-optimizing cylindrical electrodes. Two configurations (A), (B) were used, both with the same center electrode (anode) of 30/spl deg/ conic aperture. In configuration (A) the outer electrode (cathode) had the same conic aperture /spl theta/=30/spl deg/ of the anode. In configuration (B), the cathode aperture was /spl theta//sub c/>30/spl deg/. It was found that, systematically, Y(B)>Y(A), under identical operation conditions of capacitor charging voltage and filling pressure. The current-sheet propelling force j_(r)/spl times/B_(r) near the anode surface is essentially the same in (A) and (B). The electrode current variations dl/dt were monitored by a Rogowski coil at the electrode breech. The velocity of the current sheet v(z) measured via magnetic probes in the interelectrode gap determines dL/dt/spl equiv/(dl/dz)v for the assigned dl/dz. Reaction yield Y and emission of ion and ion cluster beams from the PF pinch depend critically on the current distribution between pinch region and breech region.