Browsing by Author "Dumitrescu-Zoita, C."

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    Characteristics of a small plasma focus device
    (IET, 1996) Favre Domínguez, Mario Benjamin; Silva, P.; Chuaqui, Hernán; Wyndham Hodder, Edmund Sydenham; Choi, P.; Dumitrescu-Zoita, C.
    We report on experimental observations in PFP-I, a small 3.8 kJ plasma focus, which is operated in Hydrogen-Argon mixtures to investigate the effect of parameter modifications on the overall performance of the device. An extensive array of diagnostics is been used, which includes voltage and current probes in the external circuit, a novel small magnetic probes array located along the cathode rods, filtered PIN diodes located side and end on, and multi-pinhole X-ray camera. EX1ended operated range from below 0.2 Torr upwards has been achieved with the implementation of the auxiliary discharge circuit. Despite the low voltage and low energy operation, energetic beam formation has been observed at the time of the final compression, prior to disruption. Current sheath formation and evolution has been characterised using the magnetic probes array, in correlation with beam formation and plasma emission. Time integrated visible plasma spectroscopy is performed to investigate impurity effects on focus performance and plasma dynamics at the collapse phase.
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    Experimental investigations of hotspots in a low energy plasma focus operating in hydrogen-argon mixtures
    (IEEE, 1998) Favre Domínguez, Mario; Silva, P.; Choi, P.; Chuaqui, Hernán; Dumitrescu-Zoita, C.; Wyndham, Edmund
    We present experimental results on the investigation of hotspot formation in PFP-I, a small 3.8 kJ plasma focus device operating in hydrogen-argon mixtures, at pressures from below 0.2 torr upward. A combination of multipinhole and slit-wire X-ray photography is used to measure the characteristic size and temperature of the hotspots, over a range of pressure and gas mixing ratios. Filtered p-i-n diodes and a beam-target detector are used to investigate the time evolution of the hotspots. Typical size for the hottest emitting region, at temperatures between 200 and 400 eV, is found to be around 150 /spl mu/m, with a typical duration of the high temperature phase of the order of 10 ns. In general, the temperature in the final phase of the time evolution of the hotspots reaches values which are nearly twice those of the plasma column where they are formed. Characteristic size of the hotspots is about half of that of the initial plasma column.