Browsing by Author "Chuaqui Kettlun, Hernán"
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- ItemComparative studies of ion emission characteristics in a low energy Plasma Focus operating with different gas fillings(IEEE, 2004) Bhuyan, Heman; Favre Domínguez, Mario; Kauffmann, Karla; Chuaqui Kettlun, Hernán; Mitchell, Ian H.; Wyndham Hodder, Edmund SydenhamThe results of an investigation of ion emission from a low energy Plasma Focus (PF), operating at 20 kV, with 1.8 kJ stored energy, using several different gas fillings, including hydrogen, nitrogen, argon and methane, are presented. Graphite collectors, operating in the bias ion collector mode, are used to estimate the energy spectrum and ion flux along the PF axis, using the time of flight technique. The ion beam signals are time correlated with the emission of soft X-ray pulses from the focus plasma. Characteristic duration of the ion beam pulses is found to be in the 10s to 100 s of nanoseconds. Characteristic ion energy is found to be in the 50 to 500 keV range, depending on the operating gas. Ion beam energy correlations for operation in methane indicate that the dominant charge states in carbon ions are C+4 and C+5.
- ItemDischarge formation in fast pulsed capillary discharges(IEEE, 2002) Favre Domínguez, Mario; Choi, Peter; Leñero Marchant, Ana María; Castillo, Francisco; Suzuki Vidal, Francisco Andrés; Chuaqui Kettlun, Hernán; Mitchell, Ian H.; Wyndham Hodder, Edmund SydenhamWe present a study of discharge formation in a fast pulsed capillary discharge operated in Argon or Methane, in a 50 mm long, 1.6 mm internal diameter capillary, at −15 kV applied voltage. A pressure gradient is used along the capillary, with pressures between 0.2 and 1.0 Torr in the cathode region and a pressure one tenth lower in the anode side. The diagnostics include a capacitive probe array, Faraday cup and beam-target scintillator-photomultiplier detectors. It is found that following the emission of electron beams from the hollow cathode region, a fast ionization wave propagates from the cathode towards the anode, with characteristic velocities of the order of 106 to 107 m/s. The propagation of the ionization front is assisted by the electron beams, which reach a peak current of around 200 mA.
- ItemGermicidal effect of UV light on epiphytic fungi isolated from blueberry = Efecto germinicida de luz ultravioleta sobre hongos epifíticos aislados desde arándanos.(2012) Latorre G., Bernardo; Rojas de la Fuente, Susana Dennis; Díaz, Gonzalo A.; Chuaqui Kettlun, Hernán
- ItemLaser initiated hollow gas-embedded Z-pinch(IEEE, 2004) Chuaqui Kettlun, Hernán; Aliaga Rossel, Raul; Veloso Espinosa, Felipe; Pavez Morales, Cristian Arturo; Favre Domínguez, Mario; Mitchell, Ian H.; Wyndham Hodder, Edmund SydenhamResults of new optical method of generating a precursor plasma for a shell gas embedded Z-pinch are presented. Experiments were performed on a pulse power generator using a peak current up to 150 kA with a rise time of 70 ns, 120 ns pulse length. The optical precursor plasma was generated by using a Nd-Y AG laser, 200 ml, 8 ns at 1.06 μm. Two different optical schemes were used, one consists of a combination of lenses capable of producing a hollow beam; while the other uses an axicon to generate the hollow beam. In both cases the hollow beam was focused at the cathode surface where metallic ring plasma, of either 2 or 6 mm diameter, is created. The annular preionization is created immediately before or during the first 30 ns after the line voltage is applied. The discharge was carried out in a chamber filled with hydrogen gas at 1/3 atm. Flat electrodes were used with 10 mm separation. The anode has a 6 mm diameter central hole to allow the passage of the preionizing laser. Optical diagnostics (schlieren, shadowgraphy and interferometry) were performed using the second harmonics of the same laser used to preionize. Preionizing using an axicon results in better formed hollow discharges.
- ItemObservations of Ablation Dynamics in Wire-Array Z-Pinch Experiments on the Llampüdkeñ Generator(2012) Veloso Espinosa, Felipe; Suzuki Vidal, Francisco Andres; Molina, Francisco; Mitchell, Ian H.; Chuaqui Kettlun, Hernán; Favre Dominguez, Mario Benjamin; Wyndham Hodder, Edmund SydenhamWire-array Z-pinch experiments have been performed on the Llampüdkeñ generator (~470 kA in ~410 ns) [Chuaqui et al., Laser Part. Beams 15, 241 (1997)] using an overmassed load of aluminum wires. Time-resolved optical laser schlieren and extreme ultraviolet imaging were used in order to study the plasma ablation dynamics. The results show the formation and subsequent ablation of plasma from the wires, followed by the appearance of a precursor plasma column on the axis. According to these results and to the rocket model of wire ablation, an ablation velocity of (1.7-2.6) × 105 m/s is estimated, which is larger than those obtained in faster generators. Additionally, the main resemblances and differences with previous experiments are presented, allowing in this way to open the study of this configuration in smaller scale machines.
- ItemProperties of a laser-initiated pseudospark discharge(1989) Chuaqui Kettlun, Hernán; Favre Dominguez, Mario Bejamin; Wyndham Hodder, Edmund Sydenham; Arroyo González, Luis Orlando; Choi, P.A short-pulse Nd:YAG laser is used to illuminate the back electrode surface in the hollow cathode region of a pseudospark discharge. A fast rising step voltage pulse is applied across the electrodes at various times relative to the pulsed laser illumination. The delay and jitter to the onset of gas breakdown at various filling gas pressures are measured for different laser energies and wavelengths. It is observed that the millijoule range of a green laser applied to illuminate the hollow cathode surface at up to tens of microseconds before the application of voltage would significantly reduce both delay and jitter to discharge initiation. Higher laser energy applied after voltage rise is observed to cause gas breakdown in under 100 ns.<>
- ItemX ray emission from X pinch experiments on the Llampudken Generator(IEEE, 2002) Mitchell, Ian H.; Aliaga Rossel, Raul; Gómez Luna, Jorge Antonio; Chuaqui Kettlun, Hernán; Favre Domínguez, Mario; Wyndham Hodder, Edmund SydenhamThe results from the first plasma physics experiments on the Llampüdkeñ Generator (1MA, 250 ns) are presented. X Pinch experiments have been undertaken at current levels of 400 kA with a rise time of ∼250 ns. X pinches were produced mainly from aluminium wires of different diameters and with varying numbers of wires. Results from X-ray diagnostics characterising the emitted radiation are presented. The diagnostics include filtered PIN diodes and a pinhole and slit-wire camera. Radiation of energy greater then 2.5 keV was emitted from hot spots in timescales of a few nanoseconds. Using the results from the slit-wire camera, the diameter of the hot spots is shown to be less than 5 µm.
- ItemX-ray and plasma dynamics of an intermediate size capillary discharge(2002) Wyndham Hodder, Edmund Sydenham; Aliaga Rossel, Raul; Chuaqui Kettlun, Hernán; Favre Dominguez, Mario Benjamin; Mitchell, Ian H.; Choi, PeterA small pulsed power generator, 150 kA and 120 ns, is used to form a plasma in a 5-mm diameter alumina ceramic tube. A hollow cathode geometry is used and a preionized plasma is formed in an initial vacuum background by focussing a pulsed Nd:YAG laser onto a metallic target in the hollow cathode volume. The evolution of the preionizing plasma and its expansion into the main discharge volume may be assisted by applying a current of order Amps for a variable time before the main discharge current is applied. Strong electron beams are observed both during the preionizing stage and during the start of the main current. The plasma species and temporal evolution during the main discharge is observed using X-ray spectroscopy and X-ray pinhole imaging. On varying the rate of rise of the current in the pinching phase, the transient hollow cathode effect was found to be significant at early times in the discharge in the case of the lower value of dI/dt. Both the pinch temperature and diameter depend on varying the dI/dt from 1.5 to 3 /spl times/ 10/sup 12/ A/s. The implications of plasma injection for metal vapor capillary discharges are discussed.