Nanofocus: An Ultra Miniature Pinch Focus Discharge Operating at 0.1 Joule

An ultra miniature device has been designed and constructed (nanofocus NF: 5 nF, 510 kV, 5-10 kA, 60-250 mJ, 16 ns time to peak current). Sub-millimetric anode radii covered by coaxial insulators were used for experiments in hydrogen. Evidence of pinch was observed in electrical signals in discharges operating at 100 mJ. A single-frame image converter camera (4 ns exposure) was used to obtain plasma images in the visible range. The dynamics observed from the photographs is consistent with: (a) formation of a plasma sheath close to the insulator surface, (b) the plasma sheath arrive over the anode, (c) radial compression over the anode, and (d) finally the plasma is detached from the anode in the axial direction. The total time since stage (a) to (d) was observed in -30 ns. This ultra miniature device has a value for the "plasma energy density parameter" and for the "drive parameter" of the same order or higher than plasma focus devices operating at energies several orders of magnitude higher. X ray and neutron emission is being studied. Neutron yield of the order of 10 neutron per shot is expected for discharges operating in deuterium at 10 kA.