JP4363059B2 - Microwave discharge light source device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microwave discharge light source device using microwave discharge, and particularly to cooling of the discharge vessel.
[0002]
[Prior art]
Various light source devices using microwave discharge have been disclosed.
In JP-A-7-182910, a mixed gas of He, Ne, Ar and F ₂ is enclosed in a quartz glass lamp vessel, a Kovar cooling tube is passed through the lamp vessel in an airtight manner, and water is poured into the cooling tube. A microwave discharge light source device that emits light in the ultraviolet region that is used after flowing and cooling with water is disclosed.
[0003]
However, in this publication, there is no description about the gas pressure enclosed in the lamp vessel, and there is no description about the direction of the electric field by the microwave. In the microwave discharge, the discharge does not become uniform depending on the height of the gas pressure sealed in the discharge vessel. In particular, when the gas pressure exceeds 10 kPa at room temperature, a filamentous discharge is generated in the discharge vessel. There is no idea or problem recognition of how is affected by the direction of microwave travel and the direction of the microwave electric field.
[0004]
Japanese Patent No. 2570373 discloses a method in which a part of a tube wall of a discharge vessel of a low-pressure mercury lamp that performs microwave discharge is generated with metal and the inner surface thereof is cooled with a cooling liquid.
[0005]
In this publication, it is considered that a part of the tube wall of the discharge vessel is made of metal, and the metal part seems to be perpendicular to the microwave electric field. However, when a high-pressure discharge lamp in which an excimer discharge gas such as Xe is sealed at an ambient pressure of 10 kPa or more to emit a large amount of excimer light is configured as described in this publication, the direction of microwave propagation in the filamentous light emission in the discharge vessel It is speculated that there will be a problem of density.
[0006]
Japanese Patent No. 2960829 is a publicly known example of microwave lighting of a high-pressure excimer lamp. In this lamp, the discharge vessel is filled with a combination of a rare gas and a halogen. And the discharge vessel is arrange | positioned in the microwave cavity comprised from a bowl-shaped reflector and the metal mesh of the opening side of a reflector. However, air cooling is employed for cooling the discharge vessel, and high power emission cannot be expected.
[0007]
In a microwave discharge light source device having a discharge vessel filled with a high-pressure excimer discharge gas, the present inventor has a conductive cooling tube such as a metal tube, a microwave traveling direction, and a microwave electric field direction. The present inventors have completed the present invention as a result of finding out that the arrangement relationship has a great influence on the discharge and intensively researching to realize a stable discharge of the microwave discharge light source device.
[0008]
[Patent Document 1]
Japanese Patent No. 2570373 [Patent Document 2]
Japanese Patent No. 2960829 [Patent Document 3]
JP-A-7-182910 [0009]
[Problems to be solved by the invention]
An object of the present invention is to provide a high-efficiency microwave discharge light source device by using a cooling method with less disturbance of a microwave electromagnetic field, and in particular, encloses a high-pressure excimer discharge gas that performs high-power excimer light emission. An object of the present invention is to provide a microwave discharge light source device using the discharged discharge vessel.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the invention described in claim 1 is directed to a microwave discharge light source device having a discharge vessel in which an excimer discharge gas is sealed at a normal pressure and a sealed pressure of 10 kPa or more, and a microwave power source. The container is accommodated in the waveguide, and has a straight tubular conductive member disposed in contact with the discharge container, and the straight tubular conductive member is perpendicular to the microwave traveling direction and perpendicular to the electric field direction. The microwave is intermittently supplied to the discharge vessel at a predetermined cycle so as to have an output period (t) and a stop period (s), and a cooling medium is caused to flow through the straight tubular conductive member. A microwave discharge light source device is provided.
[0012]
According to a second aspect of the present invention, the output period (t) is t ≦ 2.5 × 10 ⁻⁵ sec, and the cycle (L) is a combination of the output period (t) and the stop period (s). The microwave discharge light source device according to claim 1 , wherein L ≦ 2 × 10 ⁻⁴ sec and L> t.
[0013]
[Action]
In the present invention, a high-efficiency microwave discharge light source device in which a large amount of excimer molecules is generated by setting a high gas pressure of 10 kPa or more under conditions where the original gas for generating excimer molecules is contained in the discharge vessel. Is provided. When the straight tubular conductive member through which the cooling medium flows is arranged in a direction perpendicular to the microwave traveling direction and perpendicular to the direction of the electric field, the microwave electric field in the resonator is less likely to be disturbed, and 10 kPa Even with the above high gas pressure, stable light emission from the discharge vessel can be obtained. Moreover, since it is less likely to radiate the microwave electromagnetic field, the microwave electromagnetic field is efficiently absorbed by the discharge vessel.
[0014]
In particular, excimer molecules have the property of being easily broken when the temperature of the gas during discharge increases, so that cooling is performed by flowing a cooling medium inside the conductive member in contact with the discharge vessel, thereby providing effective cooling. Therefore, it is possible to provide a highly efficient microwave discharge light source device.
[0015]
Furthermore, a microwave discharge light source device with higher efficiency is provided by a microwave supply method characterized in that the output period and the stop period are periodic. By providing the stop period, the excimer molecules generated by the discharge are cooled, and a highly efficient microwave discharge light source device is realized.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
A typical example showing an embodiment of the present invention is schematically shown in FIG. FIG. 1 is a conceptual diagram of a microwave discharge light source device as an embodiment. Microwaves (2.45 GHz) are generated by a magnetron 2 and radiated from an antenna 3. In order to operate the magnetron 2, a power source such as a heater power source (not shown) for generating thermionic electrons inside the magnetron 2 and an acceleration power source (not shown) for the generated electrons is required. A microwave power source 1 is attached to the magnetron 2. The microwave radiated from the antenna 3 propagates in the waveguide 4 and is fed to the discharge vessel 5. The waveguide 4 is a JIS standard rectangular waveguide.
[0017]
The discharge vessel 5 is a straight tube having a double tube structure. The outer tube 51 has an outer diameter of 26 mm, the inner tube 52 has an inner diameter of 14 mm, and a longitudinal length of 150 mm. The outer tube 51 is made of synthetic quartz, and is parallel to the long side direction of the waveguide 4 cross section. Stored. A straight tubular copper pipe as the cooling pipe 6 is inserted in close contact with the inner diameter of the inner pipe 52, and the cooling pipe 6 penetrates in the long side direction of the cross section of the waveguide 4 so that water can be supplied from the outside. .
[0018]
The cooling tube 6 and the waveguide 4 are connected so that the microwave does not leak from the waveguide 4. In this embodiment, a copper pipe is used as the cooling pipe 6. However, even if a pipe made of another conductive material is used or a pipe made of a non-conductive material is coated with a conductive material, the cooling effect can be obtained. It goes without saying that it is obtained. The reason for using the conductive material is to enhance the cooling effect and to make it possible to use inexpensive water.
[0019]
A 10 kPa xenon gas is sealed in the discharge vessel 5, xenon excimer molecules are generated by microwave discharge, and a vacuum having a peak wavelength of 172 nm from the xenon excimer molecules contained in a part of light emission from the discharge. Ultraviolet light is emitted.
[0020]
Since the vacuum ultraviolet light is absorbed by oxygen in the atmosphere, the discharge vessel 5 is stored in a storage vessel 7 made of, for example, synthetic quartz that is transparent to microwaves and vacuum ultraviolet light, and the inside of the storage vessel 7 is atmospheric pressure. Filled with about nitrogen gas. For example, a metal mesh 8 is formed on a part of the waveguide 4 and is opaque to the microwave and transparent to the vacuum ultraviolet light. The vacuum ultraviolet light is radiated to the outside through the metal mesh 8. . In order to suppress oxygen absorption of vacuum ultraviolet light as much as possible, the storage container 7 is disposed so as to be in close contact with the metal mesh 8.
[0021]
The center of the discharge vessel 5 is installed at the antinode of the standing wave of the electric field generated in the waveguide 4, that is, the position where the electric field strength is maximum, and is designed to absorb the microwave most efficiently. In general, the discharge vessel 5 is disposed in a resonator formed continuously with the waveguide. However, in this embodiment, the discharge vessel 5 is accommodated in the waveguide 4, so that the waveguide 4 is left as it is. The structure also serves as a resonator.
[0022]
In addition, a reflector (not shown) that can move so that the position of the discharge vessel 5 is the maximum position of the electric field strength is provided, or a matching unit (not shown) so that microwaves are efficiently supplied to the discharge vessel discharge. Or a directional coupler (not shown) may be provided so that the microwave reflected from the discharge vessel 5 does not return to the antenna 3 and destroy the magnetron 2. Measures are taken for the above problems, and illustration and description are omitted here.
[0023]
A state of the microwave electric field propagating in the waveguide 4 and the discharge vessel 5 is shown in FIG. The length of the arrow in the figure indicates the electric field strength. A TE ₁₀ mode electromagnetic field propagates in the JIS standard rectangular waveguide 4, and an electric field parallel to the short side of the cross section of the waveguide 4 propagates.
[0024]
FIG. 3 shows a cross-sectional view taken along the plane AA ′ in FIG. The microwave electric field propagating through the waveguide 4 is divided into two as shown in the figure by a thin cooling pipe 6 arranged to divide the waveguide 4 into two. At this time, since the cooling pipe 6 is arranged perpendicular to the microwave electric field, it is characteristic that the microwave electric field is divided into two without being disturbed.
[0025]
If the perpendicularity of the cooling tube 6 to the microwave electric field is not maintained, a current flows in the cooling tube 6 due to the microwave electric field, causing a current loss. As a result, the power is radiated and a large power loss occurs, and the microwave power is not efficiently absorbed by the discharge vessel 5.
[0026]
When microwave power 200W is radiated from the antenna 3 and the cooling tube 6 is not inserted, the surface temperature of the discharge vessel 5 measured with a radiation thermometer is 260 ° C and the vacuum ultraviolet light intensity measured near the metal mesh 8 Is 3 mW / cm ² . On the other hand, when the cooling tube 6 was inserted and water of 1 liter / min was flowed, the surface temperature of the discharge vessel 5 was 200 ° C., and the vacuum ultraviolet light intensity was 6 mW / cm ^2, and an improvement effect was obtained. With the above method, it is possible to provide a liquid cooling method with less disturbance of the microwave electromagnetic field, and it is possible to provide a microwave discharge light source device that uses highly efficient excimer light radiation.
[0027]
It is known that higher gas pressure is more efficient for obtaining excimer molecular light emission. However, when the gas pressure increases, it becomes difficult to generate and maintain the discharge, and the difficulty becomes more prominent in the microwave system that supplies energy to the discharge by electromagnetic waves. For example, a discharge cross section of a xenon excimer lamp filled with 20 kPa of xenon gas is as shown in FIG. The upward arrow in the figure indicates the microwave electric field.
[0028]
The microwave incident from the outside of the discharge vessel 5 forms a discharge immediately after entering the inside of the discharge vessel 5, but the discharge does not spread due to the high gas pressure, and a discharge is formed only in the vicinity of the discharge vessel 5. The same phenomenon occurs in both the incident wave and the reflected wave, and local discharge is formed at two locations on the microwave incident side and the reflection side of the discharge vessel 5 as shown in FIG.
[0029]
However, if the microwave is supplied so that the output period and the stop period periodically change at this time, the discharge is not maintained immediately after the microwave enters the inside of the discharge container 5, and the discharge container as shown in FIG. Discharge is maintained in the vicinity of the conductive cooling tube 6 having the highest electric field strength.
[0030]
For example microwave output period 3μ seconds, by the supply was 20μ sec stop period, the intensity of the vacuum ultraviolet light of the xenon excimer from 6 mW / cm ² at the time of steady continuous microwave supply to 10 mW / cm ² And a great improvement was seen. The results shown in FIG. 6 were obtained by summarizing the vacuum ultraviolet light intensity ratio with respect to the steady supply of microwaves using the microwave output period and the stop period as parameters.
[0031]
In FIG. 6, the vertical axis represents the period (L) of the microwave output period (t) and the stop period (s), and the horizontal axis represents the microwave output period. It is a plot of the vacuum ultraviolet light intensity when the microwave is intermittently supplied at a predetermined period so as to have an output period (t) and a stop period (s). The numerical value of each point shows a relative value when the vacuum ultraviolet light intensity at the time of steady continuous microwave supply is 1.0.
[0032]
The hatched area in the figure, that is, the area where (t) is t ≦ 2.5 × 10 ⁻⁵ sec and the period (L) is L ≦ 2 × 10 ⁻⁴ sec and L> t. Under the microwave supply conditions, the intensity of the vacuum ultraviolet light of xenon excimer is improved by more than 50% compared to the intensity at the time of steady continuous microwave supply. Improvements exceeding 50% have a significant energy saving effect.
[0033]
【The invention's effect】
As described above, by disposing the tubular conductive cooling tube substantially perpendicular to the microwave electric field irradiated to the discharge vessel, it becomes possible to cool the microwave electric field without disturbing it, and a high-efficiency microwave A wave discharge light source device was provided.
[0034]
In particular, in a microwave discharge light source device that uses emitted light from excimer molecules having a high gas pressure, it is possible to achieve higher efficiency by providing a stop period without supplying the microwave constantly.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an embodiment of the present invention.
FIG. 2 is a conceptual diagram of a microwave electric field distribution propagating in the waveguide and in the discharge vessel in the embodiment of the present invention.
FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG.
FIG. 4 is a state of discharge of a microwave discharge light source device in which a conductive cooling tube is passed through the center of a discharge vessel at a high gas pressure.
FIG. 5 shows a discharge state of the microwave discharge light source device when microwaves are supplied so that the output period and the stop period periodically change.
FIG. 6 is a diagram showing a vacuum ultraviolet light intensity ratio at the time of periodic modulation with respect to the time of steady microwave supply.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Microwave power supply 2 Magnetron 3 Antenna 4 Waveguide 5 Discharge vessel 51 Outer tube 52 Inner tube 6 Cooling tube 7 Storage container 8 Metal mesh

Claims (2)

In a microwave discharge light source device having a discharge vessel in which excimer discharge gas is sealed at a sealed pressure of 10 kPa or more at room temperature and a microwave power source,
The discharge vessel is accommodated in a waveguide, and has a straight tubular conductive member disposed in contact with the discharge vessel. The straight tubular conductive member is perpendicular to the microwave traveling direction and in the direction of the electric field. It is arranged in a vertical direction, the microwave is intermittently supplied to the discharge vessel at a predetermined cycle so as to have an output period (t) and a stop period (s), and a cooling medium is caused to flow through the straight tubular conductive member. A microwave discharge light source device. The output period (t) is t ≦ 2.5 × 10 ⁻⁵ sec, and the cycle (L) of the output period (t) and the stop period (s) is L ≦ 2 × 10 ⁻⁴ sec. The microwave discharge light source device according to claim 1 , wherein L> t.

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