A small plasma focus (3.3 kJ) is designed from the viewpoint of simplicity, reliability, and cost effectiveness to act as a source of pulsed high-density plasmas. The simplicity of the device and associated diagnostics coupled with its rich variety of plasma phenomena makes this device ideal for the teaching of plasma nuclear fusion particularly for developing countries where such facilities are at present rarely available. Six sets of the device have been constructed and tested in various gases with better than 95% reliability and reproducibility in various plasma phenomena including neutron production of 0.5–1.0×108 per discharge when operated in 3-Torr deuterium. The design principles, procedures, and parameters are discussed and test results shown.

A Mather-type small plasma focus device was operated in air filling in the pressure range of 0.5 to 1.0 Torr and capacitor bank charging voltage of 13–15 kV. A strong focusing action was observed in this pressure range. Magnetic probe signals at various axial positions were used to estimate velocity of current sheet and axial magnetic field distribution profiles. It was observed that under the present experimental conditions the magnetic field remains constant at 0.72 T from z=0.0 cm to z=8.0 cm but falls rapidly to 0.52 T at about z=14.5 cm at a fixed radial distance of 2.65 cm. The magnetic field and velocity measurements indicate a current shedding effect—only 68.5% of the total injected current flows into the focus region. The rapid drop of the magnetic field at z=8.0 cm suggests that further (initial shedding is at the insulator) current and mass shedding in the focus tube is significant after this value of z. Experimental values of velocity of the current sheet are compared with those of the snow plough theoretical model.

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Cassava and maize starch were irradiated with an ultraviolet beam of light (337.8 nm) obtained from Blumlien flat plate transmission line transversely excited atmospheric pressure nitrogen gas laser. Irradiation was carried out on solid starch with and without addition of either zinc, magnesium or titanium oxide.

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