RU2536094C1 - Device for shaping volumetric self-sustained discharge - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: device for shaping a volumetric self-sustained discharge includes a tight housing, in which two extended shaped electrodes galvanically connected to a pulse power source are installed along the axis. One of the electrodes is fixed on a dielectric base with a developed surface, and the other one is fixed on reverse current leads so that a discharge gap is formed between the electrodes. Both electrodes are of a replaceable type and have a shaped surface along the perimeter, which is made on the basis of a Stepperch profile; with that, the electrode fixed on the reverse current leads has a possibility of being moved relative to the other electrode to adjust the discharge gap. The reverse current leads are made in the form of bent rods and located so that distance from the electrode fixed on the dielectric base to the reverse current leads along the surface of the dielectric base meets the ratio of L_surf≥2.5D, where D - height of the discharge gap.

EFFECT: providing a possibility of shaping a homogeneous and stable volumetric self-sustained discharge during a pump pulse period.

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Description

Technical field

The invention relates to quantum electronics, and in particular to devices for forming a self-sustained volume discharge (OCR), and can be used in the development of pulsed and repetitively pulsed gas lasers.

State of the art

A device is known for forming a self-sustained volume discharge in mixtures of SF ₆ with hydrocarbons (carbon deuterides) without special gas preionisation devices, containing an electric-discharge glass-epoxy chamber and an electrode system for producing OCP from two flat electrodes with a discharge gap of 150 mm [1]. The cathode with the size of the flat part of the surface 150 × 750 mm was rounded around the perimeter with a radius of 1 mm, its surface was subjected to sandblasting. The size of the anode was 300 × 900 mm. The discharge volume was ≈21 l. The pressure of the mixtures was 103 Torr. The voltage pulse generator (GIN) was designed according to a ten-stage Arkadyev-Marx generator with a shock capacitance of 40 nF and a maximum output voltage of 550 kV. The generation pulse had a duration at half maximum ≈180 ns. The laser generation energy reached 144 J at HF and 115 J at DF with electric efficiency of 2.8 and 2.2%, respectively.

The disadvantage of this device is the high edge heterogeneity of the electric field in the discharge gap, as well as the fact that in this device all the characteristics are obtained in the mode of single inclusions.

In this installation, tires are used as return conductors that do not allow gas purging in the discharge gap, which does not allow the device to be used in a pulse-periodic mode.

A device is known for forming an OCR for use in an XeCl laser [2], comprising a sealed housing in which two profiled electrodes extended along the optical axis of the laser are installed, one of which (the anode) is grounded and the other (the cathode) is high-voltage and placed on a dielectric cover with a developed surface. The cathode is connected to the generator via reverse current conductors, which are a metal grid. The preionization of the discharge gap is carried out by UV radiation of spark discharges. Calculations and experiments were performed for the following laser parameters: discharge gap of 50 mm, active discharge length of 800 mm. The profile of the electrodes and the geometry of the reverse conductors were optimized in terms of obtaining maximum uniformity of the electric field in the interelectrode gap. A generation energy of ≈3.6 J was obtained in a volume of the active medium of about 1.5 L, a laser efficiency of ≈3.6% with a pulse duration at its half maximum of ≈210 ns and a pulse repetition rate of ≈100 Hz. Forming line capacitance 240 nF.

However, this design is unsuitable for large volumes of active medium. As the discharge gap increased due to the design limitations of the chamber, it was impossible to increase the discharge aperture without reducing the generation efficiency. With an increase in the distance from the discharge axis to the edge of the reverse current conductor, an increase in the electric field strength at the edges of the electrodes occurred, which caused the discharge and generation to be heterogeneous.

The disadvantage of this design is also the use of the grid as reverse current conductors. At high currents, the probability of grid burning increases. To work with high currents, it is necessary to increase the thickness of the grid, which, due to a decrease in the gas flow rate, will lead to a decrease in the pulse repetition rate. As a result, the laser power will decrease.

In addition, in this device, slightly electronegative gases are used as the working medium (PC). To initiate OCP in such gases, preionization is necessary to obtain primary electrons. When using this system, an additional power supply system for preionization is required, a synchronization system with the main power supply system, which leads to a design complexity.

As a prototype, a laser [2] was chosen as the closest in technical and physical nature.

Disclosure of invention

In the inventive device, PCs based on strongly electronegative gases (for example, SF ₆ , fluorides, iodides, chlorides) used in non-chain electric discharge pulsed lasers are used.

The objective of the present invention is to increase the output power and specific energy of a laser with a large PC volume with a closed pump cycle of a medium operating in pulsed and pulse-periodic modes with a high pulse repetition rate.

The technical result is the formation of a homogeneous and stable OCR during the duration of the pump pulse (≈350 ns).

The technical result is achieved by the fact that in the device for forming an OCP containing a sealed enclosure, in which two extended profiled electrodes are mounted along the axis, galvanically connected to a GIN, one of the electrodes being mounted on a dielectric base with a developed surface, and the second on reverse current conductors that a discharge gap is formed between the electrodes, it is new that both electrodes are replaceable and have a perimeter profile surface made on the basis of the Stepperch profile, and the electrode mounted on the return conductors has the ability to move relative to another electrode to adjust the discharge gap and the exact installation of the electrodes relative to each other, while the return conductors are made in the form of curved rods and are located so that the distance from the electrode mounted on a dielectric base, inverse to conductors on a dielectric base surface satisfies the relation L _dressings ≥2,5D, where D - the height of the discharge gap.

Small-scale inhomogeneities 40–50 μm high are made over the entire working surface of the electrodes, which forms the required cross section, and the remaining profile surface of the electrodes is polished.

Adjustment of the discharge gap and the exact installation of the electrodes relative to each other is carried out using quotation mechanisms made according to the type of ball bearing, while the reverse current conductors have the possibility of bending.

The return conductors are covered with a layer of insulation.

The distance from the electrode, mounted on a dielectric base, to the return conductors in the gas satisfies the relation L _gas ≥1.5D, where D is the height of the discharge gap.

The implementation of electrodes along the perimeter with a profile made on the basis of the Stepperch profile allows one to reduce the heterogeneity of the electric field strength in the discharge gap, which leads to a uniform energy deposition in PC and a uniform distribution of the generation energy density over the active volume cross section.

To satisfy condition L _dressings ≥2,5D, where D - the height of the discharge gap, is formed on the dielectric base surface-developed, grooves formed triangular or trapezoidal, or sinusoidal shape, which provides the dielectric strength of the dielectric surface.

The presence of a developed surface of the dielectric base, formed by triangular, trapezoidal, or sinusoidal grooves, leads to a decrease in the chamber volume, and additional insulation of the reverse conductors allows the return conductors to be located as close to the electrode as possible, this together leads to a decrease in the inductance of the discharge circuit, and, consequently, shortening of the pump pulse, which allows working with strongly electronegative PCs without streamers (breakdown) in the discharge gap.

Adjustment of the discharge gap is carried out using quotation mechanisms made according to the type of ball bearing, while the reverse conductors have the ability to bend. These adjustment mechanisms allow the use of electrodes with different profiles based on the Stepperch profile at different height of the discharge gap. The use of detachable connections makes it possible to periodically change the electrodes in order to update the quality of their surface and ensure a stable discharge. The ability to accurately install the electrodes relative to each other allows you to form a uniform volumetric electric field along the entire length of the discharge gap.

On the working surface of the electrodes, small-scale inhomogeneities 40–50 μm high are made, which improve the development of the OCP and allow for a more uniform and stable volume discharge in the discharge gap without preionization. In this case, the working surface is understood as the flat and part of the profiled surface, which form the necessary volume of OCP. To ensure the formation of the required volume of OCP, the remaining profile surface of the electrode is polished (Ra1.25).

Figure 1 shows the design of the device for the formation of OCP, where: 1 - housing; 2 - anode; 3 - dielectric base; 4 - cathode; 5 - reverse current lead; 6 - dielectric plate; 7 - adapter; 8 - threaded sleeve; 9 - clamping flange; 10 - liner; 11 - finger.

Figure 2 shows the autograph of the OCP, where 2 is the anode; 4 - cathode. From this drawing it can be seen that the dimensions of the cross section of the OCP correspond to the required values. The device operates as follows.

A high-voltage voltage pulse from the GIN is supplied to electrode 2. An OCR is formed in the discharge gap, which initiates a chemical reaction in the PC, which leads to the generation of laser radiation.

In order to confirm the feasibility of the claimed device and achieve a technical result, a laboratory prototype was made and tested. Inside the gas-discharge casing 1, solid electrodes 2 and 4 of AMg6 aluminum alloy were located. The electrodes installed in the housing are similar in size to the electrodes installed in a full-scale laser layout. The length of the electrodes was 640 mm; the height of the discharge gap was 130 mm. In the experiments, electrodes were used with dimensions in the plan of 650 × 180 mm with rounding at the ends with a radius of R50 mm. The thickness of the electrodes is 30 mm. Along the perimeter, including the radius parts, the electrodes are made with a Stepperch profile calculated for various parameters Y ₀ (0.4-0.45) and d ₄ (0.7-0.8) [3]. Under the working surface of the electrode, forming the necessary active volume of OCP, in this case, we mean the flat and part of the profiled surface, limited by a contour with dimensions of 600 × 130 mm. The return conductors 5 in an amount of 26 pieces, placed at a distance of 50 mm from each other, are made in the form of curved rods made of brass with insulation made of fluoroplastic. The discharge gap could vary using three quotation mechanisms in the range of 100-130 mm. When the fingers 11 rotate, the electrode 4 moves rectilinearly vertically, due to the sphere made at the end of the finger, the electrode can also bend. With D = 130 mm, the distance L _p = 420 mm, and L _gas = 220 mm. The gas pressure inside the casing was 0.15 atm, while there was a forced pumping of the gas medium. As the working mixture, a mixture of SF ₆ with H _{2 was used} . The operating impulse voltage was 300 kV.

The power source contained a GIN, made according to the Arkadyev-Marx scheme, with a sharpening capacity designed to shorten the high-voltage pulse. The described electrical circuit made it possible to work both in single and in frequency modes. The pulse repetition rate of 25 Hz.

The experiments showed that in this device a homogeneous and sufficiently stable OCP is implemented in a given volume, which allows to achieve high parameters of laser generation.

Information sources

1. Apollonov V.V., Kazantsev S.Yu., Oreshkin V.F., Firsov K.N. "A fuzzy electric discharge HF (DF) laser with high radiation energy." Quantum Electronics, T.25, No. 2, 1998, p.123-125.

2. Borisov V.M., Demyanov A.V., Kiryukhin Yu.B. "A theoretical and experimental study of the development of large-scale instability in the discharge of an XeCl laser with UV preionization." Quantum Electronics T.24, No. 1 (1997), pp. 25-30.

3. E.A. Stappaerts, “A novel analytical design method for discharge laser electrode profiles”, Appl. Phys. Lett, 40 (12), p. 1018.

Claims (6)

1. Device for the formation of a volumetric self-discharge (OCR), containing a sealed enclosure in which along the axis are two extended profiled electrodes galvanically connected to a switching power supply, one of the electrodes mounted on a dielectric base with a developed surface, and the second on the back conductors so that between the electrodes a discharge gap is formed, characterized in that both electrodes are replaceable and have a profile surface around the perimeter, made on the basis of e of the Stepperch profile, while the electrode mounted on the return conductors has the ability to move relative to another electrode to adjust the discharge gap and accurately install the electrodes relative to each other, and the return conductors are made in the form of curved rods and are located so that the distance from the electrode is fixed based on the dielectric to inverse conductors on a dielectric base surface satisfies the relation L _dressings ≥2,5D, where D - the height of the discharge gap. 2. The device for forming a self-contained volume discharge according to claim 1, characterized in that on the entire working surface of the electrodes forming the OCR of the desired section, small-scale inhomogeneities 40-50 microns high are made, and the rest of the profile surface of the electrodes is polished. 3. The device for forming a self-contained volume discharge according to claim 1, characterized in that the adjustment of the discharge gap and the exact installation of the electrodes relative to each other are carried out using quotation mechanisms made according to the type of ball bearing, while the return conductors have the ability to bend. 4. A device for forming a self-contained volume discharge according to claim 1, characterized in that the return conductors are coated with a layer of insulation. 5. The device for forming a self-contained volume discharge according to claim 1, characterized in that the distance from the electrode mounted on a dielectric base to the reverse gas conductors satisfies the ratio L _gas ≥1.5D, where D is the height of the discharge gap. 6. The device for forming a self-contained volume discharge according to claim 1, characterized in that the developed surface of the dielectric base is formed by grooves of a triangular or trapezoidal or sinusoidal shape.

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