Browsing by Author "CHUAQUI, H"

Now showing 1 - 11 of 11
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    BREAKDOWN CHARACTERISTICS OF A LASER-TRIGGERED PSEUDOSPARK DISCHARGE
    (1989) CHUAQUI, H; FAVRE, M; WYNDHAM, E; ARROYO, L; CHOI, P
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    BREAKDOWN FORMATION IN A TRANSIENT HOLLOW-CATHODE DISCHARGE - A STATISTICAL STUDY
    (1995) CHOI, P; CHUAQUI, H; FAVRE, M; COLAS, V
    Discharge formation at low pressure is found to be greatly influenced in the presence of a suitable hollow cathode region. The formation of a moving virtual anode which extends the anode potential to within the hollow cathode region is thought to be responsible for the enhanced ionization growth which subsequently leads to gas breakdown, In this paper, the spatial evolution of the local potential in the discharge region of a pulsed hollow cathode discharge has been measured in a range of pressures with two different cathode apertures. An extensive data set has been collected and analyzed using a statistical technique, From the characteristic of the statistical distribution of the data, unique features associated with the role of hollow cathode at the different stages of discharge formation have been identified, It was found that the influence of the hollow cathode region is strongest iri the start of ionization growth and in the final change over to high current breakdown.
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    DEPENDENCE OF CATHODE APERTURE IN PULSED HOLLOW-CATHODE DISCHARGES
    (1992) FAVRE, M; LENERO, AM; CHOI, P; CHUAQUI, H; WYNDHAM, E
    The effect of electric field penetration in the hollow-cathode region of self-initiated pulsed hollow-cathode discharge is investigated. The discharge is operated in hydrogen at pressures between 30 and 200 mTorr with applied voltages between 10 and 30 kV. Aluminum cathodes with aperture diameters and lengths from 1 to 5 and 2 to 18 mm, respectively, are used. The results show that the effect of the hollow cathode in discharge initiation is particularly strong at low pressures. In the range of parameters investigated, the time delay to breakdown and the jitter decrease when cathode aperture with larger diameters and shorter lengths are used. At high pressure the pulsed hollow-cathode effect is less important as ionization processes in the main gap become dominant.
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    EXPERIMENTAL STUDIES OF IONIZATION PROCESSES IN THE BREAKDOWN PHASE OF A TRANSIENT HOLLOW-CATHODE DISCHARGE
    (1993) CHOI, P; ALIAGA, R; BLOTTIERE, B; FAVRE, M; MORENO, J; CHUAQUI, H; WYNDHAM, E
    The ionization process in the prebreakdown phase of a transient hollow cathode discharge (THCD) is investigated. The discharge is operated in H-2 and N-2 at pressures between 30 and 750 mTorr with applied voltages up to 30 kV. A capacitive probe array is used to measure the spatial and temporal evolution of plasma formation in the interelectrode spacing. The results obtained are consistent with the formation of a moving virtual anode. The growth and evolution of the virtual anode are closely linked to the formation of electron beams emitted from the hollow cathode region before and at the time of electric breakdown.
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    HIGH-CURRENT ELECTRON-BEAM GENERATION IN A VACUUM TRANSIENT HOLLOW-CATHODE DISCHARGE
    (1993) CHUAQUI, H; FAVRE, M; SOTO, L; WYNDHAM, ES
    Experimental observations are presented of prebreakdown electron beam generation in a Transient Hollow Cathode Discharge (THCD) in a vacuum. The discharge driver consists of a 400 kV maximum voltage, 25 nF Marx operated at 450 J stored energy coupled to a 120 ns, 1.5 Omega coaxial line. Electron beams with peak currents up to tens of kA are observed when a pulsed Nd-YAG laser is used to produce a plasma at the back Of the cathode surface, inside the Hollow Cathode Region (HCR). It is found that a plasma density of a few 10(18) cm(-3) in a volume of a few mm(3) is required to generate intense electron beams. Optimal conditions are determined by varying the position of the laser focal spot inside the HCR and the time delay between the laser and the applied voltage. The main features of the electron beams are similar to those observed in conventional THCD at pressures in the 10-200 mtorr range.
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    HOLLOW-CATHODE EFFECTS IN CHARGE DEVELOPMENT PROCESSES IN TRANSIENT HOLLOW-CATHODE DISCHARGES
    (1995) FAVRE, M; CHOI, P; CHUAQUI, H; KAUFMAN, Y; MORENO, J; WYNDHAM, E
    A detailed experimental study of space charge formation and ionization growth in Transient Hollow Cathode Discharges (THCD) is presented, The experiment was performed with an applied step voltage up to 30 kV, with rise time less than 50 ns, The discharge was operated in different gases, at pressures in the range 50-750 mTorr, with cathode apertures ranging from 1 to 5 mm diameter and 5 to 20 mm long, with 10 cm electrode separation, Spatial charge formation, both in the Hollow Cathode Region (HCR) and inter electrode space, has been studied with a capacitive probe array. Properties of high energy electron beams have been measured with a beam-target scintillator-photomultiplier arrangement, Detailed correlations of the electron beam evolution with the charge probe signals inside and outside the HCR clearly demonstrate the role of the electron beam in the initial formation and late evolution of a virtual anode and, in turn, the field enhanced ionization when the anode potential is brought close to the HCR, These results clearly identify the different regimes in which the Hollow Cathode plays a significant role in ionization growth in the inter electrode space and in the processes which eventually lead to electric breakdown.
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    MEASUREMENTS ON ELECTRON-BEAMS IN PULSED HOLLOW-CATHODE DISCHARGES
    (1992) FAVRE, M; CHUAQUI, H; WYNDHAM, ES; CHOI, P
    Two different regimes of electron beams have been reported in the pulsed hollow cathode discharge-a low-current, high-energy beam, and a relatively hi-current beam of low energy. The high-energy beam is related to the hollow cathode geometry and is found to be present even in the absence of subsequent gas breakdown, while the low-energy beam is always associated with voltage breakdown. In the present work, detailed measurements of the spatial and temporal distribution of the electron beam transported beyond a semi-transparent anode associated with gas breakdown are reported. In particular, a high-energy component is observed after electrical breakdown. Low-energy electron beams are observed to be transported beyond the anode throughout the main discharge period.
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    OBSERVATIONS OF HOLLOW-CATHODE LIGHT-EMISSION FROM A TRANSIENT HOLLOW-CATHODE DISCHARGE
    (1991) WYNDHAM, E; CHUAQUI, H; FAVRE, M; CHOI, P
    Experimental observations are presented on the light emission from the hollow cathode region of a pulsed hollow cathode discharge. A 2 mJ, 30 ns, 1.06-mu-m laser pulse incident on the back of the cathode is used to trigger the discharge. The temporal evolution of the light emission from this region is recorded in 50 nm spectral bands. Comparisons are made with the laser applied before and after the application of voltage across the discharge chamber. Clear experimental evidence is found of the importance of a transient volume hollow cathode process prior to gas breakdown in the main discharge region.
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    QUANTUM-THEORY OF 2ND-HARMONIC GENERATION
    (1983) ORSZAG, M; CARRAZANA, P; CHUAQUI, H
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    SIMPLE FARADAY CUP WITH SUBNANOSECOND RESPONSE
    (1989) CHUAQUI, H; FAVRE, M; WYNDHAM, E; ARROYO, L; CHOI, P
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    SOLUTION PHYSICAL DEVELOPMENT OF AGFA-GEVAERT EMULSIONS FOR HOLOGRAPHY
    (1983) ALIAGA, R; CHUAQUI, H; PEDRAZA, P