JP2004259502A - Microwave discharge light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-efficiency microwave discharge light source device, using a cooling method which reduces a disturbance of electromagnetic field of a microwave, where in particular, the microwave discharge light source uses a high-pressure excimer lamp which radiates a high-power excimer light. <P>SOLUTION: The microwave discharge light source device comprises a discharge vessel filled with an excimer discharge gas at a charged pressure of 10 kPa or higher at room temperature, and a microwave power source, where the discharge vessel is housed in a waveguide and has a straight tube-like conductive member in contact with the discharge vessel itself, the straight tube-like conductive member is placed in a direction perpendicular to the traveling direction of the microwave and perpendicular to the direction of the electric field, and a cooling medium flows through the conductive member. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a microwave discharge light source device using microwave discharge, and more particularly to cooling of a discharge vessel.
[0002]
[Prior art]
Various light source devices using microwave discharge have been disclosed.
He in a lamp vessel of quartz glass in JP-A-7-182910, Ne, filled with mixed gas of Ar and F _2, is passed through the airtight Kovar cooling tube lamp vessel, the water cooling pipe There is disclosed a microwave discharge light source device that emits light in an ultraviolet region to be used after flowing and cooling with water.
[0003]
However, this publication does not describe the gas pressure sealed in the lamp vessel and does not describe the direction of the electric field generated by microwaves. In microwave discharge, uniform discharge does not occur depending on the level of the gas pressure sealed in the discharge vessel. In particular, at a high sealed gas pressure exceeding 10 kPa at room temperature, a string-like discharge occurs in the discharge vessel, and the discharge occurs. There is no idea or problem recognition of how is influenced by the traveling direction of the microwave and the direction of the electric field of the microwave.
[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 formed of metal, and the inner surface thereof is cooled with a cooling liquid.
[0005]
In this publication, 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 filled with an excimer discharge gas such as Xe at room temperature at a fill pressure of 10 kPa or more in order to emit a large amount of excimer light is configured in this publication, the filament traveling in the discharge vessel has a microwave traveling direction. It is presumed that there is a problem that density is generated along the route.
[0006]
As a known example of microwave lighting of a high-pressure excimer lamp, there is Japanese Patent No. 2960829. In this lamp, the discharge vessel is filled with a combination of a rare gas and a halogen. The discharge vessel is arranged in a microwave cavity formed by a gutter-shaped reflector and a metal mesh on the opening side of the reflector. However, air cooling is adopted for cooling the discharge vessel, and high output light emission cannot be expected.
[0007]
In the microwave discharge light source device having a discharge vessel filled with a high-pressure excimer discharge gas, the present inventor has described that a conductive cooling tube such as a metal tube, a microwave traveling direction and a direction of a microwave electric field. The present inventors have found that the arrangement relationship has a great influence on the discharge, and have made intensive studies to realize stable discharge of the microwave discharge light source device. As a result, the present invention has been completed.
[0008]
[Patent Document 1]
Japanese Patent No. 2570373 [Patent Document 2]
Japanese Patent No. 2960829 [Patent Document 3]
Japanese Patent Application Laid-Open No. 7-182910
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a high-efficiency microwave discharge light source device using a cooling method that reduces disturbance of a microwave electromagnetic field, and in particular, encloses a high-pressure excimer discharge gas that emits high-power excimer light. It is an object of the present invention to provide a microwave discharge light source device using a discharge vessel which has been used.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a microwave discharge light source device having a discharge vessel filled with an excimer discharge gas at room temperature at a fill pressure of 10 kPa or more, and a microwave power supply. The container is housed in a waveguide, and has a straight tubular conductive member disposed in contact with the discharge vessel, and the straight tubular conductive member is perpendicular to the microwave traveling direction, and perpendicular to the direction of the electric field. A microwave discharge light source device, wherein the microwave discharge light source device is arranged in the direction, and a cooling medium flows through the conductive member.
[0011]
The invention according to claim 2 is characterized in that 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). Of the present invention.
[0012]
Preferably, the output period (t) satisfies t ≦ 2.5 × 10 ⁻⁵ sec, and the period (L) is a combination of the output period (t) and the stop period (s). Satisfies L ≦ 2 × 10 ⁻⁴ sec and L> t, whereby the microwave discharge light source device according to claim 2 is provided.
[0013]
[Action]
In the present invention, a large amount of excimer molecules are generated by setting a high gas pressure of 10 kPa or more under the condition that a large amount of the original gas for generating excimer molecules is contained in the discharge vessel, and a high-efficiency microwave discharge light source device 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 in a direction perpendicular to the direction of the electric field, the microwave electric field in the resonator is less disturbed and 10 kPa Even with the above high gas pressure, stable light emission from the discharge vessel can be obtained. Further, since the radiation of the microwave electromagnetic field is reduced, the microwave electromagnetic field is efficiently absorbed by the discharge vessel.
[0014]
In particular, since excimer molecules have a property of being easily broken when the temperature of the gas during discharge increases, effective cooling is performed by cooling by flowing a cooling medium inside the conductive member in contact with the discharge vessel. Thus, a highly efficient microwave discharge light source device can be provided.
[0015]
Further, 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 made periodic. By providing the stop period, a microwave discharge light source device having a period in which excimer molecules generated by discharge are cooled and having high efficiency is realized.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 schematically shows a typical example showing an embodiment of the present invention. FIG. 1 is a conceptual diagram of a microwave discharge light source device according to an embodiment. A microwave (2.45 GHz) is generated by a magnetron 2 and radiated from an antenna 3. In order to operate the magnetron 2, power sources such as a heater power supply (not shown) for generating thermoelectrons inside the magnetron 2 and a power supply for accelerating the generated electrons (not shown) are required. A microwave power supply 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 rectangular waveguide conforming to JIS.
[0017]
The discharge vessel 5 is a straight tube having a double tube structure. The outer tube 51 is made of synthetic quartz having an outer diameter of 26 mm, an inner tube 52 having an inner diameter of 14 mm, and a longitudinal length of 150 mm. Is 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, and has a structure capable of supplying water from the outside. .
[0018]
The cooling pipe 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 for the cooling pipe 6. However, the cooling effect can be obtained by using a pipe made of another conductive material or a pipe made of a non-conductive material coated with a conductive material. Needless to say, it can be obtained. The reason for using the conductive material is to enhance the cooling effect and to enable use of inexpensive water.
[0019]
A xenon gas of 10 kPa 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 included 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, which is transparent to microwaves and vacuum ultraviolet light. About nitrogen gas. For example, a metal mesh 8 which is opaque to microwaves and transparent to vacuum ultraviolet light is formed on a part of the waveguide 4, and the vacuum ultraviolet light is radiated to the outside via 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 substantially in close contact with the metal mesh 8.
[0021]
The center of the discharge vessel 5 is located at the antinode of the standing wave of the electric field generated in the waveguide 4, that is, at the position of the maximum electric field intensity, and is designed to absorb microwaves most efficiently. In general, the discharge vessel 5 is provided in a resonator formed continuously with the waveguide, but in this embodiment, since the discharge vessel 5 fits in the waveguide 4, 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 becomes the maximum position of the electric field strength is provided, or a matching device (not shown) that efficiently supplies microwaves to the discharge vessel discharge. May be provided, or a directional coupler (not shown) may be provided to prevent the microwave reflected from the discharge vessel 5 from returning to the antenna 3 and destroying the magnetron 2. Countermeasures have been taken against the above problems, and illustration and description thereof are omitted here.
[0023]
FIG. 2 shows a state of the microwave electric field propagating in the waveguide 4 and the discharge vessel 5. The length of the arrow in the figure indicates the electric field intensity. The JIS standard rectangular waveguide 4 propagates electromagnetic field of TE ₁₀ mode, an electric field parallel to the short sides of the cross-section of the waveguide 4 propagates.
[0024]
FIG. 3 is a cross-sectional view taken along the line AA ′ in FIG. The microwave electric field propagating in the waveguide 4 is vertically divided into two parts by a thin cooling tube 6 arranged so as to vertically divide the waveguide 4 into two parts. At this time, since the cooling pipe 6 is disposed perpendicular to the microwave electric field, the microwave electric field is bisected with little disturbance.
[0025]
If the cooling pipe 6 does not maintain the perpendicularity to the microwave electric field, a current flows through the cooling pipe 6 due to the microwave electric field, causing a current loss. As a result, a large power loss occurs, and microwave power is not efficiently absorbed by the discharge vessel 5.
[0026]
When microwave power 200 W is radiated from the antenna 3 and when the cooling pipe 6 is not inserted, the surface temperature of the discharge vessel 5 measured by the 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 pipe 6 was inserted and water was flowed at 1 liter / min, the surface temperature of the discharge vessel 5 was 200 ° C., and the vacuum ultraviolet light intensity was 6 mW / cm ^2, which was an improvement effect. According to the above-described method, it is possible to provide a liquid cooling method with less disturbance of the microwave electromagnetic field, and to provide a microwave discharge light source device using highly efficient excimer light emission.
[0027]
It is known that higher gas pressure is more efficient for obtaining excimer molecular luminescence. However, as the gas pressure increases, it becomes difficult to generate and maintain a discharge, and the difficulty is more remarkable in a microwave system that supplies energy to a discharge by electromagnetic waves. For example, a discharge cross section of a xenon excimer lamp in which xenon gas of 20 kPa is sealed 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 the discharge is formed only in the vicinity of the discharge vessel 5. A similar phenomenon occurs in both the incident wave and the reflected wave, and a local discharge is formed at two places on the microwave incident side and the reflection side of the discharge vessel 5 as shown in FIG.
[0029]
However, at this time, if the microwave is supplied so that the output period and the stop period periodically change, the microwave does not enter the inside of the discharge vessel 5 and the discharge is not maintained immediately, and as shown in FIG. The discharge is maintained in the vicinity of the conductive cooling pipe 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 significant improvement was seen. The results as 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 cycle (L) obtained by combining the microwave output period (t) and the stop period (s), and the horizontal axis represents the microwave output period. 7 is a plot of vacuum ultraviolet light intensity when microwaves are intermittently supplied at a predetermined cycle so as to have an output period (t) and a stop period (s) with respect to intensity. The numerical value at each point indicates a relative value when the vacuum ultraviolet light intensity at the time of steady continuous microwave supply is 1.0.
[0032]
The shaded area in the drawing, 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 condition, the intensity of the vacuum ultraviolet light of the xenon excimer is improved by more than 50% compared to the intensity at the time of the continuous continuous microwave supply. An improvement exceeding 50% has a large energy saving effect.
[0033]
【The invention's effect】
As described above, by arranging the tubular conductive cooling pipe substantially perpendicular to the microwave electric field applied to the discharge vessel, it is possible to cool the microwave electric field without disturbing the same, thereby providing a highly efficient microwave. A wave discharge light source device has been provided.
[0034]
In particular, in a microwave discharge light source device using emission light from an excimer molecule having a high gas pressure, it is more efficient to supply a microwave with a stop period without constantly supplying the microwave.
[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 a waveguide and in a discharge vessel according to an embodiment of the present invention.
FIG. 3 is a sectional view taken along line AA ′ of FIG. 2;
FIG. 4 shows a state of discharge of a microwave discharge light source device in which a conductive cooling pipe is passed through a central portion of a discharge vessel at a high gas pressure.
FIG. 5 shows a state of discharge of the microwave discharge light source device when microwaves are supplied such that the output period and the stop period change periodically.
FIG. 6 is a diagram showing a vacuum ultraviolet light intensity ratio at the time of periodic modulation with respect to a case where microwaves are constantly supplied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Microwave power supply 2 Magnetron 3 Antenna 4 Waveguide 5 Discharge vessel 51 Outer pipe 52 Inner pipe 6 Cooling pipe 7 Storage vessel 8 Metal mesh

Claims (3)

In a microwave discharge light source device having a discharge vessel filled with an excimer discharge gas at a filling pressure of 10 kPa or more at room temperature and a microwave power supply,
The discharge vessel is housed in a waveguide and has a straight tubular conductive member disposed in contact with the discharge vessel, and the straight tubular conductive member is perpendicular to the microwave traveling direction and in the direction of the electric field. A microwave discharge light source device arranged in a vertical direction, wherein a cooling medium flows in the straight tubular conductive member. The microwave discharge light source device according to claim 1, wherein 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). 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. 3. The microwave discharge light source device according to claim 2, wherein L> t.

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