Apparatus for generating volumetric self-sustained discharge

FIELD: physics.

SUBSTANCE: apparatus for generating volumetric self-sustained discharge has a discharge chamber in which are mounted three electrode pairs which are connected to a pumping source, each pair consisting of plate-like profiled electrodes. Each cathode plate is situated in the plane of the corresponding anode plate and electrode pairs are mounted either parallel to the longitudinal axis of the chamber or at an acute angle to said axis. The working edge of the central cathode plates has at the centre a straight portion to which portions with a Stepperch profile adjoin at both sides. The working edge of the central anode plates has an arched shape and faces the discharge gap with its convex surface. Portions of the working edges of the outermost anode and cathode plates, facing the centre electrodes, repeat the profile of the working edge of corresponding anode and cathode central plates. Outer portions of working edges of the outermost anode and cathode plates have an arched shape and a longer length than portions of working edges of the outermost anode and cathode plates facing the centre electrodes, wherein all portions of the working edges have smooth mating.

EFFECT: enabling generation of a uniform volumetric self-sustained discharge between pairs of electrode plates in different gaseous media.

7 cl, 3 dwg

The device relates to the field of quantum electronics, namely, devices for forming a self-sustained volume discharge (OCR). Especially preferable to use the inventive device in an electrical discharge pulse-periodic lasers pumped volume self-sustained discharge in active environments, UV and IR lasers based on XeCl, XeF, KrF, ArF, CO₂, HF and other Device may also be used to address plasma-chemical problems.

Well-known [1], which studied the dynamics of the development of the OCR system using flat electrodes and were not considered questions of formation of a homogeneous discharge due to the profiling of the electrodes. In addition, in this work, the experiments were carried out at low pressures of a gas mixture in a single generation mode discharge. At higher pressures the active medium or in the frequency mode of operation, the discharge will be less uniform.

Famous work [2], which is devoted to the development of a wide-aperture electric discharge laser with plate electrodes. It is shown that the distribution of the glow discharge coincides with the distribution of Energobud in the discharge plasma. In this work we used the anode-cathode pair with the working edge of the three species. Plate with arcuate profile had a width of 60 mm and the radius of the working edge 200 mm (edge ka the DOI plates were rounded, the corner radius was 8 mm). Plates of other species also had a width of 60 mm and a working edge with a profile Steppers [3]calculated for a period of 30 mm with coefficients in₀=0.45, d₄=0.8. Plate of the third kind had a width of 120 mm and a working edge with a profile Steppers at the edges and the Central flat part of the width of 60 mm Electrodes were placed perpendicular to the optical axis of the laser, it was not possible to form a narrow beam of laser radiation. In addition, the analogue is designed to work in single mode pulses, i.e. the conditions described in this paper cannot explore the formation of a discharge in the high frequency mode of the laser. In this work did not take into account edge effects associated with the inhomogeneity of the electric field at the electrodes. In addition, this device was not used system preionization mode.

A prototype device for forming a uniform discharge between the plate electrodes is the device first described in [4]. Multiple-bit interval was formed 12 pairs of anode-cathode plates with different combinations of profile of the working edge of the anode and cathode plates. For example, in one embodiment, the working edge of all the cathode plates had a profile Steppers, and the working edge of all of the anode plate is arcuate Fort is at. Design of electrode site was allowed to establish the electrodes along the optical axis of the laser or at a slight angle to it. To improve the conditions of formation volume discharge was used mechanism of preionization mode. The pre-ionization was carried out spark discharges, located on both sides of the discharge gap.

In this work were recorded only the total intensity of all places, therefore, about the degree of homogeneity of the discharge between each cathode-anode pair is difficult to speak. In the prototype was considered only two types of profiles electrodes, in addition, the design did not take into account edge effects associated with the inhomogeneity of the electric field at the electrodes. The disadvantage of this device also may include the use of spark system preionization mode, which contributes to the formation of inhomogeneous discharge near sparks, which leads to the deterioration of the output characteristics of the laser.

The challenge which seeks the invention is a device for forming a homogeneous self-sustained volume discharge between the plate electrodes in mixtures of high-frequency UV and IR lasers.

The technical result achieved by the device involves the formation of a homogeneous relationships between all pairs of electrode plates in various who's gas environments that will lead to the improvement of the energy characteristics of the laser.

The technical result is achieved in that the device for forming a self-sustained volume discharge containing a discharge chamber, which has connected to the pumping source, at least three electrode pairs, each of which consists of a plate shaped electrodes, so that each plate of the cathode is located in the plane of the respective plate anode electrode pairs placed either parallel to the longitudinal axis of the camera or at an acute angle to it, it is new that the working edge of the Central cathode plates contains located at the center of a straight line segment to which both sides are adjacent plots with profile Steppers and the working edge of the Central anode plate has an arched shape and is convex in the direction of the discharge gap; areas of working edges at the anode and cathode plates facing the Central electrode, repeat the profile of the working edge of the respective anode and cathode of the Central plate, and the outer sections of the working edges at the anode and cathode plates are arcuate in shape and longer length than the sections of the working edges at the anode and cathode plates facing the Central electrode, all of which phase the working edges are smooth mate.

Pump source includes at least one pre-ionization, which is a dielectric tube, located along the working edge of the cathode plate, and two electrodes, providing a sliding discharge on the surface of the dielectric tube.

The edges of all of the electrode plates are rounded with a radius not less than 1 mm.

The working edge of the cathode plate in cross section has the shape of an arc.

Neighboring electrode plates are arranged at a distance of 0.5-2 mm from each other.

The thickness of the electrode plates is 0.5-2 mm.

The formation of a homogeneous discharge in the electric discharge lasers plays a very important role to get good energy parameters. The distribution of the intensity of the glow discharge is largely determined by the profile of the electrodes. Study on the selection of the required profile are quite labor intensive theoretical and experimental work. You want to obtain a homogeneous diffuse discharge in the electrode gap at high specific Energobud. In lasers with plate electrodes and the level of specific Energobud up to 11 MW/cm³at a current density of up to 3 kA/cm². Such a high Energobud due to the small width of the discharge in these lasers, which allows to achieve a high repetition frequency is FL laser pulses. At elevated Energobud much more difficult to form a uniform volumetric discharge, which will not fall into the spark phase. Thus, the question of the choice of the profile of the electrodes to form a homogeneous discharge in lasers with plate electrodes was most acute.

Design of laser cameras analogues [1, 2] and a prototype [4] makes the observation of the discharge across the optical axis of the laser in order to investigate the degree of homogeneity of the discharge along the length of the plate electrode. Therefore, experimental studies on the formation of a homogeneous discharge between the plate electrodes was developed specialized gas-discharge chamber, which allows observation of the discharge between each anode-cathode pair of plate electrodes.

1 schematically shows the inventive device, where:

1 - pump source;

2 - cathode;

3 - anode;

4 is a dielectric tube;

5 - the internal electrode device of the preionization mode;

6 is an external electrode device of the preionization mode.

7 - zone self-sustained volume discharge.

Figure 2 presents a photograph of the discharge and the distribution of light intensity for two different combinations of electrodes in a mixture of F₂:Heh:Ne=10:10:2000 Top. All the photographs of the glow discharge cathode is located at the top and the anode - to decrease the. On figa presents a photograph of the discharge and the distribution of the intensity of its glow when the cathode had a profile Steppers, and PIGB - modified profile Steppers (with a straight portion of the center). The anode plate in both cases had an arched shape. As can be seen from figure 2, insert the flat part in the middle of the cathode to avoid failure in the Central part of the intensity distribution of the glow discharge and to obtain a more uniform discharge.

Figure 3 presents a photograph of the discharge and the distribution of the intensity of the glow discharge between the outermost electrodes: symmetric (a) and asymmetrical (b) in a mixture of F₂:Xe:Ne=10:10:2000 Top. As can be seen from figure 3, the replacement of the external sections of the working edges at the anode and cathode plates helps to avoid breakdowns on the edges of the electrode gap, and also to obtain a uniform discharge of greater length.

Electrode pairs placed either parallel to the longitudinal axis of the camera or at an acute angle thereto. Each plate of the cathode 2 is located in the plane of the respective plate anode 3. The cathode 2 is connected via a shared bus with the pumping source 1. The pumping source 1 was connected, at least one system of the preionization mode, located along the cathode plates near their working edges, consisting of a dielectric tube 4 and the two electrodes, one of the 5 which is located inside the tube 4, and the second 6 - outside.

For the formation of self-sustained volume discharge 7 is carried out, as a rule, the pre-ionization of the active medium (for some active environments need in the preionization mode is missing). For the preionization mode interelectrode gap was used sliding discharge on the surface of the dielectric tube 4 located at a distance of ≈12 mm from the working edge of the cathode plates. While reaching to the electrode gap of a certain voltage on the open surface of the ceramic tube is formed by a sliding discharge, which is a UV pre-ionization for the main discharge. When reaching between the electrodes, the breakdown voltage is formed in the main discharge 7.

In the specific example of the discharge was observed perpendicular to the plane of installation of the electrodes or along it through the window of the CaF₂located on 4 sides of the discharge chamber. Inside the chamber was located electrode plates of brass with a thickness of 1 mm, an Electrode plate used in a discharge chamber whose dimensions are similar to the plates installed in full-scale models of lasers, for example, in [4]. The length of the electrode plates was 22.2 mm or 25.6 mm and was determined by the diameter obostriteliv tanks specifying step of electrode systems full-scale lasers. Interelectrode be the tion could vary in the range of 10-20 mm. Electrode pairs placed either in one plane or at an acute (α≤0-20°) angle to it, the distance between adjacent pairs were 0.5-2 mm were used In the experiments the electrodes with curved profiles of the working edges with different radii of curvature R (100...450 mm), and with modified profiles Steppers calculated for different parameters in₀(0.4-0.45) and d₄(0.65-0.8).

The electrical circuit of the pumping source contained cumulative capacity With_n=2.1 NF and botricello capacity With_about=NF. When switching the thyratron cumulative capacity on C-C diagram was charged obsterilnaya capacity. For the implementation of inductive-capacitive isolation to each pair of electrode plates were connected its obsterilnaya capacity C_oⁱ=0.4 nF. Each obsterilnaya capacity was charged through its own decoupling inductance (L_pⁱ=1 µh) of the total cumulative capacity. Described electric circuit can be used in single or in the frequency mode. The maximum pulse frequency of 30 Hz was limited power supply capacity and resistance discharge mode without the forced pumping of the gas mixture. To determine the electrical characteristics of the discharge were applied resistive divider and a low-inductance current flat shun is. The divider was connected directly to the cathode plate. The shunt was installed in the common circuit of the discharge pump and the preionization mode. The front of rise of voltage level values 0.1...0.9 U_maxwas ≈55 NS. The duration of the current at 0.5 I_maxamounted to 16 NS. Charging voltage was varied in the range of 14 to 20 kV.

For mixtures of UV lasers, the total gas pressure was varied in the interval from 2 to 3 ATM. For mixtures IR lasers, the total gas pressure was considerably lower and amounted to 0.1-0.4 ATM. For each of the active mixture in the whole pressure range, the length of the discharge and the shape of the distribution of the intensity of the glow discharge has not changed significantly.

The experiments showed that the electrode with the working edge with a profile Steppers distribution of intensity of the glow discharge has a failure in the Central part of the electrode (Figa). The working edge with a modified profile Steppers was a straight portion of the center electrode and the profile Steppers at the edges. A straight line segment had a length of 5-15 mm depending on the desired length of the electrode. The modified profile Steppers reduce failure in the middle of the intensity distribution of the glow discharge by 10-15%.

Electrodes with arcuate profile shape with different radii of curvature allow you to get enough Oder the command discharge with a bell-shaped distribution. The profile was chosen experimentally, homogeneous discharge the greatest length was observed when the cathode was modified profile Steppers, and the anode - profile curved shape with R=300 mm (Figb).

To reduce edge effects were produced electrodes with asymmetric profile of the working edge. The profile of the electrodes was chosen experimentally, the most homogeneous discharge was observed when half of the electrode had the same profile as the neighboring (Central) electrode, and the second half - arcuate profile shape with R=300 mm in Addition, the arcuate length of the electrode was increased. The use of electrodes with asymmetric profiles allowed us to avoid breakdown at the edges of the electrode gap, and also led to increased light intensity at the edges of electrode site and increase the length of the discharge along the electrode length.

The sliding discharge for the preionization mode bit period compared to the pre-ionization of the spark that helped to increase the stability and the repetition rate of laser pulses, as well as to increase the lifetime of the active medium of the laser.

Blending all sections of the working edges of the electrodes avoids the amplification of the electric field at the interfaces of different profiles, eliminating unnecessary heterogeneity of the category.

With rohlena all edges of the electrode plates with a radius of not less than 1 mm allowed us to avoid breakdowns between adjacent electrodes, as well as the occurrence of spark channels between the cathode-anode pairs.

Matched the shape of the working electrode surface to UV and IR lasers. The length of the discharge in these laser mixtures was ~70-80% of the length of the electrode. On electrodes with experimentally selected profile studies major dependencies energy laser pulses, the limit frequency of pulse repetition, stability energy of the laser pulses in the high frequency mode of the laser from the composition of the active medium of the laser, the total pressure of the laser mixture, specific energovorov, speed pumping of the working medium of the laser. The use of electrodes with new profiles allowed us to increase the energy characteristics of lasers at ~20%, and the maximum repetition rate of the pulses at ~10%.

SOURCES of INFORMATION

1. Appolonov CENTURIES, Belevtsev A.A., Kazantsev HE, Seifulin AV, Firsov K.M. Savinellis volumetric discharge in nezemnyh HF lasers on mixtures of SF₆with hydrocarbons. Quantum electronics. T, No. 3 (2000), s-214.

2. Andramanov AV, Kabaev S.A., Saginaw BV, nor-Arevyan, VA, Pisetskaya ALEXANDER, V.D. Selemir the Formation of the laser beam profile in the HF laser with plate electrodes. Quantum electronics. T.35, No. 4 (2005), s-364.

3. E.A. Stappaerts A novel analytical design method for discharge laser electrode profiles. Appl. In the period., 40 (12), p.1018-1019.

4. Andramanov AV, Kabaev S.A., L is Ginzel BV, Nor-Arevyan, VA, Pisetskaya ALEXANDER, V.D. Selemir high Frequency HF laser with plate electrodes. Quantum electronics. T.36, No. 3, (2006), s-238

1. Apparatus for forming a self-sustained volume discharge containing a discharge chamber, which has connected to the pumping source, at least three electrode pairs, each of which consists of two plate-shaped electrodes, and installed so that each plate of the cathode is located in the plane of the respective plate anode electrode pairs placed either parallel to the longitudinal axis of the camera or at an acute angle thereto, characterized in that the working edge of the Central cathode plates contains located at the center of a straight line segment to which both sides are adjacent plots with profile Steppers, and the working edge of the Central the anode plate has an arched shape and is convex in the direction of the discharge gap; areas of working edges at the anode and cathode plates facing the Central electrode, repeat the profile of the working edge of the respective anode and cathode of the Central plate, and the outer sections of the working edges at the anode and cathode plates are arcuate in shape and longer length than the sections of the working edges at the anode and cathode plates, facing the s to the Central electrode, all sections of the working edges are smooth mate.

2. The device according to claim 1, wherein the pump source comprises at least one pre-ionization.

3. The device according to claim 2, characterized in that the pre-ionization is a dielectric tube, which is located along the working edge of the cathode plate, and two electrodes, providing a sliding discharge on the surface of the dielectric tube.

4. The device according to claim 1, characterized in that the edges of all of the electrode plates are rounded with a radius not less than 1 mm.

5. The device according to claim 1, characterized in that the working edge of the cathode plate in cross section has the shape of an arc.

6. The device according to claim 1, characterized in that adjacent electrode plates are arranged at a distance of 0.5-2 mm from each other.

7. The device according to claim 1, characterized in that the thickness of the electrode plates is 0.5-2 mm