Colecciones Institucionales

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Browsing Colecciones Institucionales by browse.metadata.fuente "IET"

Now showing 1 - 9 of 9
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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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    Characteristics of electron beam formation in a hollow cathode triggered fast capillary discharge
    (IET, 2000) Favre Domínguez, Mario Benjamin; Choi, P.; Dumitrescu, C.; Chuaqui, Hernán; Wyndham Hodder, Edmund Sydenham; Krisch, I.; Larour, J.; Rous, J.; LeBlanc, C.; Rutkevich, I.; Mond, M.
    The fast pulsed capillary discharge has been shown to be an efficient source of radiation in the XUV range. Two main conditions are required to operate a pulsed capillary discharge as a fast XUV radiation source. First, initial formation of an on-axis conducting plasma column detached from the capillary wall, and second, application of a high rate of current rise to an inductive load, to heat the capillary plasma. To satisfy these requirements we have developed a pulsed capillary discharge device which combines the features of a transient hollow cathode discharge (THCD) with the inherent characteristics of the capillary discharge, to obtain XUV radiation with ns rise time. The discharge operates in the nanosecond regime with current in the kA region into a millimeter diameter capillary. The initial breakdown process is controlled by the physics of the THCD, with hollow cathode emitted electron beams, which assist the formation of an on-axis ionization channel. In this paper we present a theoretical model of breakdown formation in the capillary which is compared with experimental measurements of ionization growth. The properties of the electron beams are quantified and their influence on the subsequent breakdown formation is considered through time-resolved measurements on the plasma emission properties and VUV spectroscopy.
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    Electrical characteristics of a small plasma focus device
    (IET, 1996) Choi, P.; Favre Domínguez, Mario Benjamin; Silva, P.; Chuaqui, Hernán; Wyndham Hodder, Edmund Sydenham
    Efficient plasma focus operation relies on uniform initial breakdown across the insulator surface. In this paper, we discuss basic plasma focus electric circuit, in order to highlight circuit modifications that produce high voltage oscillation at initial breakdown time. Superimposed on the main discharge voltage such oscillating voltage has been found in real systems to enhance the initial gas breakdown by localizing the initial current path across the insulator surface. PSpice circuit simulations are compared with electric signals from different operational plasma focus devices.
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    Hollow Cathode Ionization Processes In The Breakdown Phase Of A Transient Hollow Cathode Discharge
    (IET, 1998) Favre Domínguez, Mario Benjamin; Choi, P.; Zambra, M.; Moreno Martinez, José Alberto; Chuaqui, Hernán; Wyndham Hodder, Edmund Sydenham
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    Improving distribution network resilience against earthquakes
    (IET, 2017) Navarro-Espinosa, A.; Moreno, R.; Lagos, T.; Ordoñez, F.; Sacaan, R.; Espinoza, S.; Rudnick, Hugh
    Historically, reliability analysis has ignored the occurrence of natural hazards such as those associated with extreme weather, flooding, earthquakes and tsunamis, which are becoming more and more relevant due to recent events. In this content, we present an assessment methodology to determine the resiliency levels of a distribution system e,posed to a major earthquake. The proposed 4-stage methodology models (i) the earthquake, (ii) the fragility of network components, (iv) the network outages, and (v) the impacts on network operation (including the energy not supplied) through sequential Monte Carlo simulations. This methodology is used to study the resilience of distribution networks under two particular strategies: one that hardens substations infrastructure in order to reduce their fragility levels, and the other one that uses additional network infrastructure in the form of transfer cables to shift load among substations in case a major event occurs. Through several case studies based on a real distribution network in Chile, we demonstrate that hardening substations infrastructure may be a more resilient way to deal with earthquakes, even when compared to an alternative, extreme case where a vast number of transfer cables are installed to support damaged substations
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    Space and time resolved observations of plasma dynamics in a compressional gas embedded Z-pinch
    (IET, 1996) Soto, L.; Chuaqui, Hernán; Favre Domínguez, Mario Benjamin; Saavedra Sanchez, Renato Alejandro; Wyndham Hodder, Edmund Sydenham; Aliaga-Rossel, R.; Mitchell, I.
    Recent experiments in a gas embedded compressional Z-pinch are presented. The experiments have been carried out in H2 at 1/3 atm, using a pulse power generator capable of delivering a dI/dt > 1012 A/s. The pinch is initiated by a focused laser pulse, which is coaxial with a cylindrical DC rnicrodischarge. This configuration results in double column pinch at early times, which at current rise evolves into a gas embedded compressional Z-pinch. Diagnostics used are Rogowskii coil, single frame holographic interferometry and holographic shadowgraphy, visible streak camera images from which, current, density, line density, pinch radius and plasma motion are obtained. The pinch is characterized by a maximum on axis density which is much higher than the expected value from filling pressure, with a Bennett temperature of 40 eV at 130 kA‥ Results shown confirm the high degree of compression achievable with the composite preionization scheme.
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    Studies of current sheath evolution in a small plasma focus device
    (IET, 1996) Silva, P.; Favre Domínguez, Mario Benjamin; Chuaqui, Hernán; Wyndham Hodder, Edmund Sydenham; Choi, P.
    We present preliminary time and space resolved studies of current sheath formation in Plasma Focus discharges, using a novel array of non invasive magnetic field probes. The experiments are performed in a Mather type plasma focus, which is powered by a 9 µf capacitor bank, operating at 30 kV. The discharge is formed between a hollowed anode and six symmetrically arranged cathode rods. The array of small magnetic probes is located along the cathode rods. The probes are of millimeter size. They are shielded behind the rods, as to minimize capacitive coupling to the anode electrode, and allow nonperturbing measurements to be made. The array probe signals are recorded simultaneously, with 2 ns time resolution. Other available diagnostics include voltage and current probes in the ex1emal circuit, filtered PIN diodes located side and end on, and a multi-pinhole x-ray camera. A simple analytical model of current sheath evolution is used to interpret the probe signals. The experiments have been performed in pure Hydrogen and Hydrogen with Argon mixture, at pressures from below 0.2 Torr upwards. The effect of the Argon mixture on the current sheath structure is investigated with the probe array. It is found that at constant mass density operation, the increase in the percentage of Argon results in a thinner sheath, with steeper current profile.
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    Studies on pulsed hollow cathode capillary discharges
    (IET, 1996) Choi, P.; Dumitrescu-Zoita, C.; Larour, J.; Rous, J.; Favre Domínguez, Mario Benjamin; Zambra, M.; Moreno Martinez, José Alberto; Chuaqui, Hernán; Wyndham Hodder, Edmund Sydenham; Wong, C. S.
    We present preliminary results on radiation characteristics of pulsed hollow cathode capillary discharges. The device combines the on axis electron beam assisted ionization capabilities of the transient hollow cathode discharge with a novel high voltage low inductance geometrical design, which integrates the local energy storage into the electrode system. A nanosecond regime high temperature plasma is produced in a long, high aspect ratio capillary, with light emission in the UV to XUV region. The discharge is operated from near vacuum to pressure in the 1000 mTorr range
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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