On the electric breakdown in liquid argon at centimeter scale (original) (raw)
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Experimental study of electric breakdowns in liquid argon at centimeter scale
Journal of Instrumentation, 2014
In this paper we present results on measurements of the dielectric strength of liquid argon near its boiling point and cathode-anode distances in the range of 0.1 mm to 40 mm with spherical cathode and plane anode. We show that at such distances the applied electric field at which breakdowns occur is as low as 40 kV/cm. Flash-overs across the ribbed dielectric of the high voltage feed-through are observed for a length of 300 mm starting from a voltage of 55 kV. These results contribute to set reference for the breakdown-free design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).
Cathode sheath formation of corona discharge in liquid argon
Proceedings of the 2002 Ieee 14th International Conference on Dielectric Liquids, 2002
Abstraer: A onedimensional longitudinal model including the cathode sheath, the drift region and the external circuit has been used for conditions close to experiments of a COIOM discharge in liquid AI. The model provides the space and time variations of the electric field, electron and positive ion densities in the cathode region, as well as the time variations of the electric current through the discharge. The cathode electric field kzn reach values as high as several MV/cm. The influence of secondary electron emission due to ion impact has been taken into account. Creation of the cathode sheath occurs rapidly due to the multiplication of cathode-emitted elecaons in the strong electric field near the cathode, leading to a fast increase in the ion density in this region.
Stochastic and Relaxation Processes in Argon by Measurements of Dynamic Breakdown Voltages
Contributions to Plasma Physics, 2005
Statistically based measurements of breakdown voltages U b and breakdown delay times t d and their variations in transient regimes of establishment and relaxation of discharges are a convenient method to study stochastic processes of electrical breakdown of gases, as well as relaxation kinetics in afterglow. In this paper the measurements and statistical analysis of the dynamic breakdown voltages U b for linearly rising (ramp) pulses in argon at 1.33 mbar and the rates of voltage rise k up to 800 V s −1 are presented. It was found that electrical breakdowns by linearly rising (ramp) pulses is an inhomogeneous Poisson process caused by primary and secondary ionization coefficients α, γ and electron yield Y variations on the voltage (time). The experimental breakdown voltage distributions were fitted by theoretical distributions by applying approximate analytical and numerical models. The afterglow kinetics in argon was studied based on the dependence of the initial electron yield on the relaxation time Y0 (τ) derived from fitting of distributions. The space charge decay was explained by the surface recombination of nitrogen atoms present as impurities. The afterglow kinetics and the surface recombination coefficients on the gas tube and cathode were determined from a gas-phase model.
Inter-Electrode Distance and Breakdown Voltage in Low Pressure Argon Discharges
Contributions to Plasma Physics, 2012
This work deals with the Paschen law in electrical breakdown of gases at pd values around the Paschen minimum. From the Townsend model, it is possible to deduce theoretical forms of the coefficients in Paschen's law, of which our calculated values are in the range of the tabulated values from the literature. These formulae show that the breakdown voltage must be influenced by the inter-electrode distance, while the product pd remains a key parameter. This is confirmed by the Paschen curves measured in an argon discharge for inter-electrode distances varying from 2 to 9 cm.
Liquid argon dielectric breakdown studies with the MicroBooNE purification system
Journal of Instrumentation, 2014
The proliferation of liquid argon time projection chamber detectors makes the characterization of the dielectric properties of liquid argon a critical task. To improve understanding of these properties, a systematic study of the breakdown electric field in liquid argon was conducted using a dedicated cryostat connected to the MicroBooNE cryogenic system at Fermilab. An electrode sphere-plate geometry was implemented using spheres with diameters of 1.3 mm, 5.0 mm, and 76 mm. The MicroBooNE cryogenic system allowed measurements to be taken at a variety of electronegative contamination levels ranging from a few parts-per-million to tens of parts-pertrillion. The cathode-anode distance was varied from 0.1 mm to 2.5 cm. The results demonstrate a geometric dependence of the electric field strength at breakdown. This study is the first time that the dependence of the breakdown field on stressed cathode area has been shown for liquid argon.
Experimental observations in compact capillary discharges
Plasma Sources Science & Technology, 2008
We present experimental results on the characterization of a non-ablating fast pulsed capillary discharge, with a hollow cathode (HC) geometry, operating in argon below 1 Torr. Both the pre-breakdown and breakdown phase of the discharge are investigated with several diagnostics, which include electron beam monitoring, capacitive probe array and extreme ultraviolet (EUV) detector array. The pre-breakdown phase is found to be characterized by the emission of HC electron beams, which assist the propagation of a high speed ionization wave, with typical velocity in the 10 6 -10 7 m s −1 . Coinciding with electric breakdown a fast EUV radiation pulse is emitted. The leading edge of the radiation pulse is due to beam target emission by the HC electron beams. At the breakdown the radiation emission is mainly centered in the 5-15 nm spectral window, and is emitted from a capillary plasma which is being heated by a kiloampere level, 10 ns half-width current pulse.
The European Physical Journal D, 2010
This paper is dedicated to the study of the electrical and optical characteristics of direct current microhollow cathode discharges (MHCD) in argon flow. Experiments have been carried out in order to determine the so-called Paschen's curves in a static open MHCD. Current-voltage characteristics were obtained as a function of the pressure and hole diameter. MHCD enable stable direct current discharge operation, which could be ignited for pressures ranging from 12 to 800 Torr, in a very wide range of current densities and electrodes materials. Optical emission spectroscopy and analysis of the spectral line broadening of plasma line emissions were performed in order to measure parameters such as electron number density (2-4 × 10 14 cm −3 ), gas temperature (460-640 K), excitation temperature (∼ 7000 K) and electron temperature (∼ 8500 K), for current ranging from 7 to 15 mA. Lower gas temperature was measured compared to the static MHCD ones.
Journal of Applied Physics, 2013
Simulation of an Ar/NH3 low pressure magnetized direct current discharge Phys. Plasmas 20, 013508 Simulation benchmarks for low-pressure plasmas: Capacitive discharges Phys. Plasmas 20, 013507 Spatiotemporal structure of a millimetric annular dielectric barrier discharge plasma actuator Phys. Fluids 25, 017103 Electron and ion thermal forces in complex (dusty) plasmas Phys. Plasmas 20, 013703 Temporal evolution of the re-breakdown voltage in small gaps from nanoseconds to milliseconds Appl. Phys. Lett. 102, 012904 (2013) Additional information on J. Appl. Phys.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009
a b s t r a c t A materials test system (MTS) has been developed at FNAL to assess the suitability of materials for use in a large liquid argon time projection chamber. During development of the MTS, it was noted that controlling the cryostat pressure with a 'raining' condenser reduced the electron drift lifetime in the liquid argon. The effect of condensing has been investigated using a series of passive materials to filter the condensate. We report the results of these studies and of tests on different candidate materials for detector construction. The inferred reduction of electron drift lifetime by water concentrations in the parts per trillion is of particular interest.
Physical Review E, 2001
The accuracy of secondary-electron emission coefficients, that are used as input data of discharge models, seriously influences the calculated discharge characteristics. As it is very difficult to consider all possible electron emission processes of a cold cathode separately, in most of the recent models an apparent secondary coefficient ␥ is applied, which is often assumed to be constant, even for a wide range of discharge conditions. In contrast with this common assumption, the present calculations-based on a heavy-particle hybrid modelshow that in abnormal glow discharges ␥ varies considerably with changing discharge conditions: a factor of 3 change of ␥ has been found in the range of reduced current densities (0.04 mA cm Ϫ2 Torr Ϫ2 р j/p 2 р4 mA cm Ϫ2 Torr Ϫ2 ) covered in this study. The present simulations also confirm that ionization by heavy particles plays a significant role in the ion production at the abnormal cathode fall. Moreover, it is shown, that the fast heavy particles reflected from the cathode surface play the dominant role in the gas heating.