Mega-Amp Opening Switch with Nested Electrodes/Pulsed Generator of Ion and Ion Cluster Beams

摘要

The use of a plasma focus as a mega-amp opening switch has been demonstrated by two modes of operation: (a) Single shot mode; (b) Repetitive Mode with a repetition rate of 0.1-1-1 MHz. The peak current in (a) was about 0.6 MA (from a 8 kJ capacitor bank at 18 kV) and in (b) about 0.2 MA (from a 40 kJ pulse forming network at about 40 kV). A voltage multiplication by a factor somewhat > 7 was observed during the 0.1 us opening stage in (a), and by a factor somewhat > 2.4 in (b). The use of field distortion elements (FDE) in the interelectrode gap indicates that the neutron yield (from D-D fusion reactions; deuterium filling of the discharge chamber) increased by a factor 10 as compared to the yield of the same system operating at the same energy level and under the same voltage and filling-pressure conditions but without field distortion elements. Misfirings of the plasma focus machine are also virtually eliminated by using FDE at the coaxial electrode breech. The tests (based on about 10000 shots and five plasma focus machines) demonstrated that a sizable amount of nuclear reactions with high-Z nuclei (C,N) are induced by the MeV D(+) ions which are accelerated and trapped in the pinch when entered in the filling gas D2+1-15% of carbon (or nitrogen) atoms. The observed reaction yield for high-Z nuclei is increased by suitable FDE's and is about 3% of the D-D fusion reaction yield. The neutron yield Y provides for all shots a good quantitative estimate of the performance of the plasma focus as an opening switch, i.e., Y is strongly correlated with the drop of the electrode current during the 'opening' stage. (JHD)