Browsing by Author "Wyndham Hodder, Edmund Sydenham"

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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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    Time resolved observations of plasma evolution in the hollow cathode region of a transient hollow discharge
    (1996) Favre Domínguez, Mario Benjamin; Zambra Yañez, Marcelo Cristian; Moreno Martinez, Jose Alberto; Chuaqui, F.; Wyndham Hodder, Edmund Sydenham; Choi, P.
    It is known that in a transient hollow cathode discharge (THCD), the formation of a moving virtual anode in the A-K space is causally linked to the emission of high energy electron beams originated in the hollow cathode region (HCR). In this work we report on time and space resolved observations of the formation and evolution of plasma inside the HCR which are time correlated with ionization processes inside the A-K gap. The experiments have been performed in Hydrogen, at pressures between 50 to 500 mTorr, at 30 kV applied voltage. Capacitive probes are used to monitor ionization growth in the A-K gap, in conjunction with time and space resolved spectroscopic observations in the HCR. High energy electron beams are also measured. Stark broadening observations of the Hβ line indicate that the electron density inside the HCR increases up to a few times 1015 cm−3 some time before breakdown in the A-K gap. This time is also related with the electron beam activity