JPS61168839A - Thyratron - Google Patents

Abstract

PURPOSE:To heighten discharge starting voltage by circulating sealed hydrogen gas of a thyratron while supplementing a consumed portion and cooling it. CONSTITUTION:A gas circulator 40 and a heat exchanger 80 are serially connected to a thyratron proper 101 while a hydrogen gas feeder 60 is connected in parallel with the heat exchanger 80. When using the thyratron discharge, for instance, for a switching element of a laser power supply device of a large output, the high discharge starting voltage is required. The lower the sealed hydrogen pressure is, the higher the discharge starting voltage is, so that the sealed hydrogen gas is cooled by the heat exchanger 80 for obtaining the assigned pressure while finely regulating the pressure of hydrogen gas to be supplemented by using, for instance, a paradium pipe in the feeder 60 for being pressure-circulated by a circulator 40. Thereby, the temperature of hydrogen gas inside the tube can be held low thus maintaining charge starting voltage of the thyratron.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thyratron used as a switching element or the like in a power supply device for a large output laser such as an excimer laser.

(Prior Art) Thyratrons have conventionally been used as switching elements for pulsed lasers such as excimer lasers.

A thyratron is a discharge tube that has a structure similar to a triode vacuum tube and has hydrogen gas etc. sealed inside.

The basic structure of a conventional cycitron will be explained with reference to FIG.

FIG. 5 shows a schematic cross-sectional view of the thyratron. A voltage of 6.3 cm is applied between the terminals 6 and 8 to cause the cathode 2 to emit thermoelectrons.

Moreover, by further applying a trigger pulse to the terminal 6, a discharge is caused between the anode 1 and the grid 3, and switching is performed.

The reservoir 4 is used to replenish hydrogen gas lost during the switching operation, and the hydrogen gas occluded in titanium is heated by the voltage applied to the terminal 6.7 to release the hydrogen gas from the reservoir heater.

The thyratron container 5 is made of ceramic with high mechanical strength so as to be able to withstand shocks during switching.

Since thermionic electrons are constantly emitted from the cathode of the thyratron, the rise time is faster compared to the cold electron emission type switching element spark gap, and the fluctuation of the discharge start time (
Jitter) is low.

For this purpose, a thyratron of the type described above is passed through an excimer laser excitation circuit.

FIG. 6 is a circuit diagram showing the power supply circuit of the excimer laser device. The operation of the thyratron used in the power supply section of the excimer laser device will be briefly explained with reference to this drawing.

A commercial power source is connected to the slide transformer 16.

This slide transformer 16 allows the primary side voltage of the step-up transformer 17 to be adjusted.

The secondary AC high voltage of the step-up transformer 17 is passed through the full-wave rectifier 1.
8.

This rectified voltage causes the main capacitor 10 to connect to the charging resistor 9. It is charged via the charging coil 11.

Note that although the thyratron 100 is normally non-conductive, approximately 1ooo applied to the trigger input terminal 6 of the thyratron
It is made conductive by a trigger pulse signal of v.

When the thyratron 100 is energized, the charge on the main capacitor 10 is transferred to the anode 1. Through the grid 3 and the pre-discharge gap 15 in the laser tube, the peaking capacitor 14
transfer to.

Note that a plurality of preliminary discharge gaps 15 are arranged in parallel with the rod-shaped electrodes 12 and 13.

The charge of this peaking capacitor 14 is now transferred to the electrode 12.
．． 13. By flowing through the circuit formed by the preliminary discharge gap 15, a discharge occurs in the laser gas between the electrodes 12.13,
Laser light is generated. The reason why a discharge is performed in the preliminary discharge gap 15 before the discharge between the electrodes 12.13 is that the ultraviolet light generated thereby preliminarily ionizes the laser gas between the electrodes 12.13 and causes the discharge between the electrodes 12.13 to occur. This is to sometimes obtain a spatially uniform glow discharge.

If a spatially uniform glow discharge is obtained, laser light can be obtained efficiently.

Since the deionization time of the hydrogen gas sealed in the thyratron is about 10 μsec, the maximum switching frequency of the thyratron is theoretically f2 (1/10X10-
'5ec=105Hz=100KHz) is possible.

However, in reality, the repetition rate of Thyratron is only a few KH at most.
2 and is limited to low input.

Stable operation over a long period of time is possible only with an input of several kilowatts.

For example, when the laser light energy is 0.3J and the operation is repeated for 100H2, the laser output is 0.3 x 100=
It becomes 30W.

If the conversion efficiency from electricity to laser light is 1%, it is 30W.
The electrical input required to obtain a laser light output of 30W1
0.01=3000W=3KW.

Recently, excimer laser equipment has been used for applications such as uranium enrichment that require high output (laser output of several kilowatts).

There is a request to use it as a light source (requiring several hundred kilowatts of electrical input). However, as mentioned above, the output of the excimer laser device is determined by the ability of the thyratron.
It is not possible to provide a high output excimer laser device.

We will specifically examine the problems with Thyratron that determine this limit.

FIG. 7 shows the relationship between hydrogen pressure and discharge starting voltage when the anode and grid spacing is 3.5 mm.

Keep the thyratron discharge starting voltage above 25KV.
In order to input electrical energy into the laser tube corresponding to voltages greater than KV, the hydrogen gas pressure must be maintained below 0.2 Torr.

This is at low input (laser light output is 0.3JX100H2
= 30W or less and the electrical input is 3KW or less), this condition can be met.

At high inputs, the hydrogen pressure increases due to the heat generated by the thyratron's discharge, making it impossible to satisfy this condition.

In other words, the laser light output is 0.3JX200Hz-60
When obtained at W level, the hydrogen gas pressure decreases to 0.0 due to temperature rise.
It will be close to 3 torr.

When the hydrogen gas pressure becomes 0.3 Torr, as can be seen from FIG. 7, the discharge starting voltage drops to 3.5 KV, making it impossible to provide the desired power.

Furthermore, in high power thyratron switches, the temperature increase can further cause various problems.

The thyratron container is assembled by brazing ceramic and metal electrode materials.

Normally, alumina ceramic is used for ceramics and Kovar for metals in order to bring the expansion coefficients of the two closer together.
There is no problem with small inputs.

However, when the input is high, the temperature becomes high, and the difference in coefficient of expansion causes strain at the joint, which eventually causes cracks in the ceramic and peeling of the joint, making it impossible to maintain airtightness.

Furthermore, another problem is expected to be the depletion of hydrogen gas within the thyratron.

The reason for the disappearance of hydrogen gas from inside the Sila Drone is: ■Permeation through the ceramic wall.

■Hydrogen trapping occurs due to sputtering of the grid and cathode metal during thyratron discharge.

At low inputs, these are kept low and can be covered by replenishment from the reservoir, but at high inputs they seem to increase for the following reasons.

■: When the input is high, the thyratron becomes hot and the gaps between the alumina ceramic particles (crystals) become large.
Because it will be easier to pass through here.

■: At high temperatures, discharge tends to localize on the electrode surface.
Sputtering becomes noticeable.

(Problems to be Solved by the Invention) An object of the present invention is to solve the problems of a decrease in discharge starting voltage due to the temperature rise associated with a high-power switch of a thyratron, damage to the container due to the temperature rise, and consumption of hydrogen gas. By doing so, it is an object of the present invention to provide a thyratron that enables high output operation of an excimer laser device or the like.

(Means for Solving the Problems) In order to solve the above problems, a thyratron according to the present invention includes a thyratron main body having an anode, a grid, and a thermionic emission cathode and filled with hydrogen gas, a gas circulator,
a heat exchanger, a connection means for connecting the thyratron main body, the gas circulator and the heat exchanger in series to form hydrogen gas circulation cooling means, and a hydrogen gas supply device connected to the circulation cooling means. It is configured.

(Example) The present invention will be explained in more detail with reference to the drawings and the like.

FIG. 1 is a block diagram showing an embodiment of a thyratron according to the present invention. A circulator 40 and a heat exchanger 80 are connected to the thyratron body to form a gas circulation path.

A hydrogen gas supply device 60 is connected to a metal pipe that connects the gas circulator 40 and the heat exchanger 80.

The thyratron main body 101 is basically the same as the thyratron described in FIG. 5 above, except that it does not include a hydrogen reservoir inside and a heater for heating it.

Hydrogen gas within the thyratron main body 101 is circulated at high speed through the circulation path by a gas circulator 40 provided in the circulation path, and is cooled by a heat exchanger 80 .

Due to the operation of the thyratron, the hydrogen gas that has disappeared is replenished by the hydrogen gas supply device 60. The heat exchanger 80 is placed immediately upstream of the thyratron so that the cooled hydrogen gas returns directly to the thyratron main body 101.

FIG. 2 is a sectional view showing an embodiment of the gas circulator 40. FIG.

A sirocco fan 41 is housed in the container 42, and a metal tube 43 provided integrally with the container 42 is connected to the upstream thyratron main body 101.

The container 42 is airtightly connected to a flange 46' which is directly connected to a bearing portion that supports a rotating shaft 47 at a flange 45, and a plurality of bolts and nuts 48 via a copper backing (not shown).

A rotating shaft 47 of the sirocco fan 41 is supported by a hub integral with the flange 46 so as to rotate airtightly and smoothly.

Inside the hub integrated with the flange 46, there are three
ring-shaped magnets 49 are arranged.

When fine magnetic powder, which is a magnetic fluid, is sprinkled on the bearing,
These magnetic powders are concentrated in areas on the rotating shaft where magnetic flux is concentrated.

Two concentrated areas can be created using one magnet, and in this embodiment, rings of magnetic powder are formed at six locations.

A belt 53 is passed between a boo IJ 52 directly connected to the rotating shaft of the motor 54 and a pulley 51 directly connected to the sirocco fan rotating shaft 47, and the sirocco fan 41 is rotated by the motor 54.

As the sirocco fan 41 rotates, hydrogen gas from the metal tube 43 is sent to the metal tube 44.

When a sirocco fan (24 blades) with an outer diameter of 90 mm and an inner diameter of 34 mm is rotated at 3200 revolutions, the output is 105 J/s.
A flow rate of ec is obtained.

Next, an embodiment of the hydrogen gas supply device will be described with reference to FIG.

The quartz glass container 6E is connected to hydrogen gas circulation cooling means through a hydrogen gas outlet 62.

A container 61 made of quartz glass is divided into a first chamber 67 and a second chamber 68 by a partition wall 63 and a tube 66 made of palladium metal.

A tungsten coil 65 forming a sensor section of a Pirani gauge is arranged in the second chamber 68 with terminals 65a and 65b fixed to the container.

A heater wire 69 is wound around the palladium metal tube 66 in the first chamber 67, and both ends 69a, 6 of the heater 11t69
9b is fixed to the wall of the container 61.

The first chamber 67 is connected via a valve 70 to a hydrogen gas cylinder 71 (not shown).

Fine pressure adjustment by the valve 70 is not necessary, and a glass hand cock or an electromagnetic valve is used.

The palladium tube 66 has a property of permeating hydrogen gas when heated to 400° C. or higher.

The palladium tube 66 is heated by the heater 69 and the first
The hydrogen gas in the chamber 67 can be sent out to the second chamber and supplied to the outlet port 62.

By controlling the amount of heat generated by the heater 69 that heats the palladium tube 66 based on the output of the Pirani gauge, the amount of hydrogen gas supplied can be controlled.

The inventor of the present invention proposed a gas pressure adjustment having a configuration similar to this in Japanese Patent Publication No. 54-7679, entitled "Gas Laser Apparatus." The gas laser device according to this proposal adjusts the helium gas pressure in the gas laser tube using a quartz glass transmission wall, and extremely good results have been obtained.

The reason why a palladium tube is used to supply hydrogen gas in the present invention is as follows.
This is because it is necessary to finely control the hydrogen pressure of about 0.2 torr.

FIG. 4 is a perspective view of a heat exchanger used in the apparatus of the embodiment. It is partially cut away to show the internal structure.

A plurality of copper plates 84 are arranged inside a metal sealed container 81, and the copper plates 84 are cooled by a copper pipe 85 through which cooling water is introduced through a pipe 86. It is discharged.

Hydrogen gas is introduced through the introduction pipe 82, is cooled (releases heat) by contacting the copper plate 84, etc., and is caused to flow into the thyratron main body through the pipe 83.

If cooling water flows in from the pipe 86 at a flow rate of about 101/min,
The internal copper plate 84 and copper pipe 85 can be maintained at approximately the cooling water temperature.

The hydrogen gas heated within the thyratron main body 101 is cooled to near the temperature of the cooling water while being introduced from the pipe 82 and exiting from the pipe 83, and is returned to the thyratron main body 101.

(Modifications) Various modifications can be made to the embodiments described in detail above within the scope of the present invention.

Instead of using the above-mentioned type of hydrogen gas supply device, it is also possible to heat titanium that has stored a large amount of hydrogen with a heater to replenish the amount that would be lost in the thyratron body over a long period of time.

The medium of the heat exchanger is not limited to water, but liquid nitrogen can also be used. By flowing liquid nitrogen, hydrogen gas can be cooled more efficiently.

In the present invention, hydrogen gas was supplied by passing through a heated palladium tube as shown in FIG. 3, but it is also possible to use other materials.

In the embodiment described above, the Pirani gauge is housed inside the container 61, but it is also possible to move the Pirani gauge independently to another part.

If the Pirani gauge is installed near the hydrogen gas outlet from the thyratron body, it will be possible to detect a pressure closer to the pressure in the thyratron body, allowing for more accurate monitoring.

(Effects of the Invention) As explained in detail above, the thyratron according to the present invention connects the thyratron main body, the gas circulator, and the heat exchanger in series to form a hydrogen gas circulation cooling means to cool the hydrogen gas. It's Nishide.

This allows the temperature of the hydrogen gas inside the tube to be kept low, making it possible to maintain a high firing voltage of the thyratron.

Therefore, large-capacity switching becomes possible, and a high-output excimer laser device or the like can be realized.

In addition, the present invention automatically supplies hydrogen from the hydrogen gas supply device to compensate for hydrogen gas loss due to adsorption or leakage during discharge, so it is possible to always maintain an optimal hydrogen gas state. can.

Since conventional thyratrons had limited internal capacity, only small-capacity hydrogen gas reservoirs could be used. Since the thyratron according to the present invention has a hydrogen gas supply device placed outside the main body, this limitation is eliminated and a large capacity device can be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating an embodiment of a thyratron according to the present invention. FIG. 2 is a sectional view showing an embodiment of a gas circulator used in a thyratron according to the present invention. FIG. 3 is a sectional view showing an embodiment of the hydrogen gas supply device used in the thyratron of the present invention. FIG. 4 is a perspective view showing an embodiment of the heat exchanger used in the thyratron of the present invention. FIG. 5 is a sectional view of a conventional thyratron. FIG. 6 is a circuit diagram showing a typical discharge circuit of a conventional excimer laser. FIG. 7 is a graph showing the relationship between the hydrogen gas pressure of the thyratron and the discharge starting voltage. 40...Gas circulator 41...Sirocco fan 42...Gas circulator container 43.44...Metal tube 45...Flange 47...Rotating shaft 48...Bolt and nut 49... ... Ring-shaped magnet 50 ... Magnetic fluid 51, 52 ... Pulley 53 ... Belt 54 ... Motor 60 ... Hydrogen gas supply device 61 ... Quartz glass container 62 ... Hydrogen Gas outlet port 63...Partition wall 65...Pirani gauge sensor section (tungsten coil) 66...Palladium metal tube 67...First chamber 68...Second chamber 69...
・Heater wire 70...Valve 80...Heat exchanger 81...Airtight container 82.83...Hydrogen gas pipe 84...Copper plate 85...Steel pipe 86.87...Cooling water pipe 101.・Thyratron body

Claims (5)

[Claims] (1) A thyratron main body that has an anode, a grid, and a thermionic emission cathode and is filled with hydrogen gas, a gas circulator, and a heat exchanger, and the thyratron main body, the gas circulator, and the heat exchanger are connected in series. 1. A thyratron comprising: a connecting means forming a circulating cooling means for hydrogen gas; and a hydrogen gas supply device connected to the circulating cooling means. (2) The hydrogen gas supply device is connected to a first chamber containing hydrogen gas for supply, and a palladium metal that has hydrogen permeability at high temperatures and is connected to the circulation cooling means. It consists of a second chamber that is adjacent to each other with a plate in between, a Pirani gauge that detects the hydrogen concentration on the circulating cooling means side, and a heating element that controls the temperature of the palladium metal plate based on the output of the Pirani gauge. A thyratron according to claim 1. (3) The thyratron according to claim 2, wherein the Pirani gauge is arranged at a position to measure hydrogen gas flowing out from the thyratron. (4) The thyratron according to claim 1, wherein the hydrogen gas supply device releases an appropriate amount of hydrogen occluded in titanium by heating. (5) The thyratron according to claim 1, wherein the heat exchanger is disposed immediately upstream of the thyratron main body.