Production of fissioning uranium plasma to approximate gas-core reactor conditions

The intense burst of neutrons from the d-d reaction in a plasma-focus apparatus is exploited to produce a fissioning uranium plasma. The plasma-focus apparatus consists of a pair of coaxial electrodes and is energized by a 25 kJ capacitor bank. A 15-g rod of 93% enriched 235U is placed in the end of the center electrode where an intense electron beam impinges during the plasma-focus formation. The resulting uranium plasma is heated to about 5 eV. Fission reactions are induced in the uranium plasma by neutrons from the d-d reaction which were moderated by the polyethylene walls. The fission yield is determined by evaluating the gamma peaks of 134I, 138Cs, and other fission products, and it is found that more than 106 fissions are induced in the uranium for each focus formation, with at least 1% of these occurring in the uranium plasma. This technique is most convenient and inexpensive for the study of a fissioning uranium plasma and can be extended to the production of other metallic plasmas in a high neutron flux.