SU1725778A3 - Gas discharge laser with convective cooling - Google Patents

Abstract

SUMMARY OF THE INVENTION: A laser comprises a discharge chamber made in the form of a cylindrical dielectric tube, a main discharge power source connected to the main electrodes, a pulse generator, an optical resonator, a gas circuit. The gas circuit is connected to the discharge chamber through two dielectric adapters. On the surface of the dielectric tube are installed preionization electrodes connected to the pulse generator. Holes for connecting dielectric adapters are made in the side surface of the pipe with an axis perpendicular to the axis of the pipe. The electrodes of the main discharge are installed in dielectric adapters. 1 il. (L

Description

The invention relates to the field of quantum electronics and can be used in high-power gas lasers with convective cooling of the working mixture.

A device of a gas laser with convective cooling of the working mixture is known, which consists of a discharge chamber, inside which a gas discharge plasma is created using an electrode system. The resonator mirrors are placed at the ends of the discharge tube. The enhancement properties of the CO-laser medium are limited by the overheating of the active medium. To prevent overheating in such devices, the CO-laser gas mixture is pumped along the discharge tube. The limiting value of the specific output power of the radiation is limited by the value of the density of the input power Rvl.

To increase the radiation power of gas lasers with convective cooling of the medium, combined discharges are used, in which most of the energy is invested during recombination plasma decay with relatively small E / P (E is the electric field intensity; P is the gas pressure), and pulsed high E / P bit is used to create a high degree of gas ionization.

The closest to the proposed technical essence and the achieved result is a gas-discharge laser with

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by convective cooling of the working mixture Lanthanum 2M, consisting of a gas circuit providing the gas flow rate up to 70 m / s, and a discharge chamber with an optical resonator. The gas discharge chamber is a flat channel bounded above and below by preionization electrodes, asbestos-glass fiber textolite walls with openings for the passage of radiation and electrodes of the main discharge. When high voltage pulses are applied to the preionization electrodes, a capacitive discharge is maintained in the chamber volume.

From the main discharge power source, a voltage is applied to the main discharge electrodes. The need to isolate the power supply, gas circuit and resonator has led to the fact that the direction of the capacitive discharge current, the main discharge current vector coinciding with the gas flow direction, and the optical axis of the resonator are oriented in mutually perpendicular directions.

The disadvantages of the prototype are the small radiation power and the large divergence of the radiation. Since a significant amount of heat is emitted during laser operation in a gaseous medium, the gas temperature increases downstream from initial 300 to 500-600 K, which causes a corresponding decrease in gas density. Since the direction of light propagation is perpendicular to the direction of the gas flow, because of the transverse inhomogeneities of the gas density, an optical wedge arises, the refraction of light on which leads to large-scale linear aberrations of the wave background. The angular displacement of the light beam cannot be compensated for by the alignment of the resonator due to the nonstationarity of the thermal mode of the laser operation caused by a change in the energy input to the discharge chamber, turbulent pulsations of the gas flow, etc. The angular displacement of the light beam during its propagation through the active medium leads to phase distortions of the output light beam and to a deterioration of its divergence. In the prototype, the main discharge electrodes are located between the preionization electrodes. This causes distortion of the electric field in the capacitive discharge, which is used to ionize the medium. A portion of the capacitive discharge current is closed through the main discharge electrodes, which are at a high frequency under the potential of one of the preionization electrodes. This leads to the appearance of areas near the electrodes where ionization of the gaseous medium is practically absent. Therefore, the main discharge current is partially closed to the electrodes through the areas of the self-sustained discharge.

Contraction of the discharge in these areas reduces the energy input to the discharge, since the pinching of the discharge in the area of self-discharge initiates the germination of highly conductive cords in the main region and

makes it impossible for a uniform discharge to exist. In addition, the refraction of light on these inhomogeneities degrades the divergence of the laser output.

The aim of the invention is to increase the radiation power and reduce its divergence.

This goal is achieved by the fact that in an electric discharge laser with convective cooling consisting of a filled active medium of a discharge chamber made of a dielectric, a power source of the main discharge, a pulse generator, an optical resonator, a gas circuit, two dielectric adapters, through which the circuit is connected to the discharge chamber, the main electrodes connected to the power source of the main discharge and isolated by the dielectric from the active

the environment of two pre-ionization electrodes connected to a pulse generator; the discharge chamber is made in the form of a cylindrical tube, whose axis is aligned with the optical axis of the resonator, the electrodes

pre-ionization are located on the outer surface of this pipe symmetrically about its axis, the dielectric adapters are connected to the side surface of the pipe from the side of one of the electrodes

pre-ionization distance less than the length of the pre-ionization electrodes, and the main electrodes are installed in dielectric adapters so that their working surfaces do not protrude inwards

pipes.

The drawing shows a block diagram of the device.

The device contains a discharge chamber 1, a power source 2 for the main discharge, a generator of 3 pulses, an optical resonator formed by mirrors 4 and 5 installed at the ends of the discharge chamber 1, a gas circuit 6, dielectric adapters 7 and 8. In The composition of the discharge chamber includes a cylindrical tube 9, electrodes 10 and 11 of the pre-ionization, and electrodes 12 and 13 of the main discharge.

The device works as follows.

The pulse generator 3 generates a sequence of pulses with a repetition period shorter than the characteristic plasma recombination time. Capacitive discharge arising in a gaseous environment under the action of the electric pulses of the generator 3, applied to the electrodes 10 and 11, maintains high conductivity due to Townsend ionization. The electrical discharge arising between the main discharge electrodes 12 and 13 when the electric field of the main discharge power source 2 is applied, excites the CO-laser gas mixture. Light is generated at a sufficiently high degree of excitation using mirrors 4 and 5 installed at the ends of the cylindrical tube 9 of the discharge chamber 1. The overheated gas mixture is removed from the active region of the resonator by pumping gas, which is carried out through the gas circuit 6, a dielectric adapter 7, a discharge chamber 1, an output dielectric adapter 8 and a gas circuit b in which the mixture is cooled and which maintains the required pressure drop of gas between the inlet and outlet.

The design has lower phase distortions of the light beam, since the optical axis of the resonator coincides with the direction of the gas flow, and the longitudinal heterogeneity of the active medium does not cause phase distortions.

The transverse inhomogeneity caused by the outflow of gas from the energy input region is absent in the construction, since the energy input region is limited by the walls of the discharge tube. The cylindrical channel geometry is much simpler than the rectangular channel used in the prototype. The manufacture of a discharge chamber is much cheaper, since installing pre-ionization electrodes on the outer surface of the tube eliminates the need to isolate them from the active medium. The output power of the laser is also increased. In the design, the capacitive discharge to the outside of the preionization electrodes is closed to earth through the external environment, and not through the gas mixture of the laser as in the prototype (which causes additional heating of the mixture and a decrease in the laser output power).

In the design, the region of inhomogeneity of the capacitive discharge is removed from the optical resonator, which eliminates the refraction of light on such inhomogeneities. As shown by calculations of electrical capacitive discharge, the design has a higher degree of homogeneity compared to the prototype. In addition, the design has less irregularities, since the direction of the luminous flux

coincides in direction with the gradients of gas density inhomogeneities. Therefore, the refraction of light on them is eliminated, phase distortions are reduced and, therefore, the divergence of the laser is worsened.

0. The location of the pre-ionization electrodes on the outer surface of the pipe allowed in this design to place the entire main discharge region into the region of ionized capacitive discharge.

5 gas. Thereby, areas near the electrodes of the non-ionized gas are eliminated, the discharge contraction in which decreases the discharge stability.

Since the discharge is more stable, then

0 active medium, other things being equal, it is possible to invest more power and, accordingly, to increase i the radiation power.

Laser tests showed that the output-frequency power in the frequency-pulse mode was 1.5 kW with a divergence of 10 rad, which is significantly higher than the corresponding values for the Lanthan-2M installation (respectively, 1 kW and

0 3).

PRI me R. Cylindrical glass tubes with a diameter of 4.7 cm, a thickness of 1.7 mm, a total length of 3.6 m, and an axis of symmetry were used in the discharge device.

5 which coincides with the optical axis of the resonator, the gas circuit was used from the Latus-31 installation, the preionization electrodes were made of aluminum foil glued to the external surface of glass tubes. The base circuit is connected to the tube with dielectric adapters, for which holes are made in the side surface of the tube with an axis perpendicular to the axis of the tube. Electrodes main

5 bits are made of copper. The gas mixture is CO2: H2: Not - in the ratio 2: 9: 20, pressure 65 torr. One of the mirrors is deaf with a reflection coefficient of 0.98, the second is translucent with a propane ratio of 0.5. The power supply voltage of the main discharge is 12 kV. The pulse generator generated pulse beams with a repetition rate of 20 kHz, an amplitude of 20 kV, a burst duration of up to 1 ms, a burst repetition rate of up to 400 Hz. The maximum average radiation output power was 1.5 kW with a divergence rad. With a gas flow rate of 1.5 m3 / s, the device is superior in output parameters (power - by 20% and divergence - in 3

times) a prototype working with a gas flow rate twice as large - 3 m3 / s.

Claims (1)

Claims of the invention Electrode-discharge laser with convective cooling, containing an optical resonator, a dielectric discharge chamber filled with active medium, a main discharge power source, a pulse generator, a gas circuit connected to the discharge chamber through two dielectric adapters, main electrodes connected to the power source the main discharge and two pre-ionization electrodes isolated from the active medium, connected to a pulse generator, characterized in that, in order to increase the power of radiation and reduce its divergence, the chamber is made in the form of a cylindrical tube, the axis of which is combined with the optical axis of the resonator, the pre-ionization electrodes are located on the outer surface of this tube symmetrically about its axis, the dielectric adapters are connected to the side surface tubes from one of the preionization electrodes at a distance less than the length of the preionization electrodes, and the main electrodes are installed in dielectric adapters so that working surfaces do not protrude into the pipe.