RU2029967C1 - Device for recording development phases of wave and current surface discharge structures - Google Patents

Abstract

FIELD: physical facilities for analyzing gas discharges. SUBSTANCE: device has high-voltage electrode 1, grounding electrode 2, both mounted on insulating substrate 3, and photorecording optical system 7 mounted above effective surface of substrate. High-voltage electrode is connected via switch 5 to voltage source and to first lead of energy storage capacitor 4 whose second lead is connected to grounding electrode 2. Matching resistor 6 inserted between high-voltage and grounding electrodes has resistance value R for incomplete stage of discharge found from equation

, where L is discharge circuit inductance; C is energy storage capacitor value; C_g is distributed capacitance of insulating substrate 3 carrying recording layer; for completer stage of discharge resistance R is found from equation

, where R_п is ohmic resistance of plasma channels. EFFECT: improved informative capacity due to shaping of aperiodic-waveform high-voltage pulse. 1 dwg

Description

 The invention relates to physical means for studying gas discharges, and in particular, to devices for recording the phases of development of surface electric discharge processes, for example, sliding discharges formed during electric breakdown of a gas near the surface of a dielectric, and can be used to obtain and study spatio-temporal wave and current structures Sliding discharge (SA). Developing along the interface between solid and gaseous dielectrics in a strongly inhomogeneous electric field, when the other side of the surface of a solid dielectric of small thickness is covered with a conductive layer, SR is characterized by the variety and complexity of physical mechanisms. Only in the initial stage of development does an incomplete superlattice pass through the successively avalanche, streamer, and leader phases, which in the completed stage provide conditions for closing the gap with a high-current channel.

 Known devices for recording the spatio-temporal current structures of superlattices containing high-voltage and grounded electrodes located on the surface of the dielectric substrate, as well as a switching power supply based on a cable transformer and an optical photo-recording system above the surface of the substrate (Andreev S.I., Zobov E.A. ., Sidorov AN A method for controlling the development and formation of a system of parallel channels of moving sparks in air at atmospheric pressure. - ZhPMTF, 1976, N 3, p. 12-17).

 The disadvantage of these devices is the impossibility of recording wave structures of the incomplete phase of development of superlattices, since the voltage pulse generated by a cable transformer has an oscillatory shape (with a period of several microseconds), which causes the superposition and shading of the initial phases of the discharge.

 A device for recording spatially temporary wave and current structures of a sliding discharge is also known, which contains high-voltage and grounded electrodes located on the surface of the dielectric substrate, an optical photographic recording system mounted above the surface of the substrate, a capacitive energy storage device, a switch, and an inductance connected in parallel with the discharge gap [1 ].

,
L = U Δ t_т/I_g, где f - частота следования разрядных импульсов; U - их амплитуда; Δ t_т - время, требуемое для деионизации коммутатора (тиратрона); I_g - остаточный ток коммутатора (тиратрона).A disadvantage of the known device is the low information content of the process of recording wave structures, because due to the vibrational shape of the energy input pulse at the moment of transition through zero, a reverse leader stage is formed on the dielectric substrate, which neutralizes the surface charge carried by the previous phases of the discharge development and leads to repeated bursts of radiation on the substrate . This does not allow the use of other highly informative registration methods for recording wave structures, for example, based on the visualization of residual charge and potential reliefs (Zhuravlev O.A., Kisletsov A.V., Kusochok A.P. et al. Electrographic visualization of the structure of the front of a moving discharge. - Letters to the ZhTF, 1988, v. 14, No. 21, pp. 1933-1938; ed. St. N 1562833, class G 01 N 27/60, 1987). The oscillatory shape of the power pulse is due to the presence of an inductance L _s connected in parallel with the discharge gap and used for resonant charging of the capacitive storage device C. The value of L _s is selected from the conditions:
f = 1 /

,
L = U Δ t _t / I _g , where f is the pulse repetition rate; U is their amplitude; Δ t _t is the time required for deionization of the switch (thyratron); I _g - residual current of the switch (thyratron).

 The purpose of the invention is to increase information content due to the formation of a high-voltage voltage pulse of an aperiodic form.

, где L - индуктивность разрядного контура, С - емкость накопителя энергии, С_g - распределенная емкость диэлектрической подложки с регистрирующим слоем, а для завершенной стадии разряда величина сопротивления R определяется соотношением
R>2R

(R

), где R_п - омическое сопротивление плазменных каналов.This goal is achieved by the fact that in the device for recording the phases of the development of wave and current structures of a sliding discharge, containing high-voltage and grounded electrodes located on the surface of the dielectric substrate, and an optical photographic system installed above the working surface of the substrate, while the high-voltage electrode is connected via a switch to a voltage source and with the first output of a capacitive energy storage device, the second output of which is connected to a grounded electrode, between the high voltage and the straightening electrodes connected resistor, the resistance value R for which incomplete discharge stage is determined by the relation
R> 2

where L is the inductance of the discharge circuit, C is the capacity of the energy storage device, C _g is the distributed capacity of the dielectric substrate with the recording layer, and for the completed stage of the discharge, the resistance value R is determined by the ratio
R> 2R

(R

), where R _p - ohmic resistance of the plasma channels.

 The drawing schematically shows the proposed device.

 The device contains a high-voltage 1 and a grounded 2 electrodes located on the surface of the dielectric substrate 3, a capacitive energy storage 4 and a switch (spark gap) 5. A matching resistor 6 is connected in parallel with the discharge gap, providing an aperiodic shape of the high-voltage voltage pulse. An optical photorecorder 7 (a camera, a television camera, a CCD) is installed above the working surface of the substrate.

, где L - индуктивность разрядного контура; С - емкость накопителя энергии 4; R - сопротивление согласующего резистора 6. С_g ≈ ε ε_o S/d - распределенная емкость диэлектрической подложки 3; где ε - диэлектрическая проницаемость; ε_о = 8,85 ˙ 10^-12 Ф/м - диэлектрическая постоянная; d - толщина диэлектрика; S - площадь, занимаемая СР в незавершенной фазе.The device operates as follows. On the capacitive energy storage device 4, the value of the charging voltage -U _{zar is set} , not exceeding the breakdown voltage of the discharge gap between the high-voltage 1 and the grounded 2 electrodes. This corresponds to the study regime of the spatiotemporal structures of an incomplete superlattice. After charging the capacitive energy storage 4, the arrester 5 is activated and a voltage pulse is generated on the high-voltage electrode 1. The aperiodic shape of the voltage pulse with a slow exponential decay is ensured by the fulfillment of the relation
R> 2

where L is the inductance of the discharge circuit; C is the capacity of the energy storage 4; R is the resistance of the terminating resistor 6. With _g ≈ ε ε _o S / d is the distributed capacitance of the dielectric substrate 3; where ε is the dielectric constant; ε _about = 8.85 ˙ 10 ^-12 F / m is the dielectric constant; d is the thickness of the dielectric; S is the area occupied by the SR in the incomplete phase.

 As a result, from the high-voltage electrode 1 to the side of the grounded electrode 2, the channels of an incomplete superlattice develop on the surface of the dielectric 3, passing successively a series of stages (avalanche, streamer, and direct leader) and carrying charged particles onto the substrate 3. Slowed down exponential decay of the voltage pulse, as well as the high-resistance nature of the dielectric substrate 3 contributes to the long-term conservation of surface charges, which allows to obtain contrasting electrographic structures of the current channels of an incomplete superlattice.

/(R_п-2

), где R_п ≃ l/π а²N σ - омическое сопротивление плазменных каналов; l - расстояние между электродами; а - средний радиус токового канала; N - число токовых каналов; σ - электропроводность плазмы в канале.When 4 charging voltages exceeding the breakdown voltage of the discharge gap are installed on a capacitive energy storage device, the study mode of the spatio-temporal structures of the completed superlattice is implemented. In this case, the aperiodic shape of the voltage pulse is ensured by the fulfillment of the relation
R> 2R

/ (R _p -2

), where R _p ≃ l / π a ² N σ is the ohmic resistance of the plasma channels; l is the distance between the electrodes; a is the average radius of the current channel; N is the number of current channels; σ is the electrical conductivity of the plasma in the channel.

 In both modes, the proposed device allows the use of oscillographic methods for studying the current – voltage characteristics of the discharge, thermooptical recording of current channels (when using CGS films as a substrate), and acoustic and optical methods for recording gasdynamic disturbances during the development of superlattices.

 The use of the proposed device provides greater information in comparison with the prototype, since the shape of the supply voltage discharge eliminates the possibility of neutralizing the charge structures (due to the initial phases of the superlattice) and allows them to be analyzed, as well as to use a set of diagnostic methods that contribute to the construction of an adequate physical model for the development of a sliding discharge.

Claims (1)

DEVICE FOR RECORDING PHASES OF DEVELOPMENT OF WAVE AND CURRENT STRUCTURES OF SLIDING DISCHARGE, containing high-voltage and grounded electrodes located on the surface of the dielectric substrate, and an optical photo-recording system installed above the working surface of the substrate, while the high-voltage electrode is connected through the switch to the first voltage source and energy, the second output of which is connected to a grounded electrode, characterized in that, in order to increase information content by forming a high-voltage voltage pulse of an aperiodic form, between the high-voltage and grounded electrodes a terminating resistor is connected, the resistance value R of which for an incomplete discharge stage is determined by the ratio

where L is the inductance of the discharge circuit;
C is the energy storage capacity;
C _d - the distributed capacity of the dielectric substrate with a recording layer,
and for the completed stage of the discharge, the resistance value R is determined by the relation

where R _p - ohmic resistance of the plasma channels.