JPH0864179A - Deuterium discharge lamp - Google Patents

Abstract

PURPOSE: To decrease noise in a short wave length region with simple structure by making part of a light taking out part of a cylindrical discharge tube or a light radiating surface flat. CONSTITUTION: A light taking out window 4 in which part of a tube-shaped bulb is made flat is set in a discharge tube container 1 of a deuterium discharge tube. The bulb serving as the discharge tube container 1 is made of ultraviolet- ray transmitting glass, and the end is welded to a stem made of hard glass with coefficient of thermal expansion similar to the ultraviolet-ray transmitting glass to form a sealed container. Several hundreds Pa of deuterium is sealed in the bulb 1. A nickel partition 3 for shielding an electrode part is arranged in the central part of the bulb 1 to separate a cathode chamber from an anode chamber, electrodes and the metal partition are arranged, then a cathode 6 coated with a thermionic material 6 and an anode 7 made of molybdenum are faced on both sides of a discharge limiting small hole 9 of the partition plate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deuterium discharge tube used as an ultraviolet light source for a spectrophotometer, a photodetector for liquid chromatography, and the like, and more particularly to improving the radiance and reducing noise of the deuterium discharge tube. Regarding

[0002]

2. Description of the Related Art Deuterium discharge tubes are described in "Light Source Characteristics and Usage (Mar. 1985, Academic Society Publishing Center), pp. 20 to 30," edited by The Spectroscopical Society of Japan.

As for the appearance of the deuterium discharge tube, as shown in FIG. 4 (a), the bulb 1 has a cylindrical shape and is made of an ultraviolet-transparent glass, and its end face is welded to the stem 12 to form a closed container.
A metal partition wall 2 which surrounds the cathode and the anode and several hundred Pa of deuterium gas or hydrogen gas are enclosed in the tube. Reference numeral 5 indicates a light extraction direction. Reference numeral 13 is an introduction line for supplying electric power to each electrode.

FIG. 4 (b) is a cross-sectional view of the center of the electrode of the deuterium discharge tube. The discharge tube has a structure in which a cathode 6 made of a coil-shaped filament and a flat plate-shaped anode 7 are arranged as electrodes, and a partition plate 3 having a small hole 9 for narrowing discharge is provided in the middle of the cathode and the anode. . The second electrode enclosure is for controlling the discharge path and is a closed metal partition wall shielded by a metal such as nickel. When a DC voltage is applied to the discharge tube having the above structure to cause discharge, deuterium or hydrogen as a gas to be enclosed emits light through a small hole that narrows the discharge path, and emits a strong continuous spectrum in the ultraviolet region. The small hole portion that narrows the discharge path has a structure in which a plate-like recess made of molybdenum is provided and a small hole is provided at the center of the recess. The partition plate having the small holes is formed at the center of the electrode. The bulb 1 of the prior art has a tubular shape, and the light emitted from the small hole portion at the center of the electrode is refracted outward when passing through the concave portion of the tubular bulb, and the emission angle of the light becomes large. Further, the ultraviolet transmissive glass used as a bulb has a reduced transmittance in the ultraviolet region, and particularly in a wavelength region of 200 nm or less, the transmittance is significantly reduced. In order to improve the transmittance, it is desirable to use synthetic quartz as a window material.
Synthetic quartz has approximately twice the transmittance in the wavelength range of 200 nm or less as compared with ultraviolet-transparent glass, but by using synthetic quartz, light in the short wavelength range of 180 nm or less is also transmitted, so that ozone is placed on the optical axis. To generate. 25 ozone
Absorption occurs near 0 nm, which causes noise. Therefore, in order to reduce the noise, the ultraviolet transmitting glass is used. In addition, a tubular valve structure that is inexpensive is common. As described above, the decrease in the transmittance and the increase in the radiation angle due to the refraction of light cause a decrease in the light collection efficiency and the like, resulting in a decrease in the signal intensity of light and an increase in noise. Therefore, in the wavelength range of 200 nm or less, the N / S ratio is extremely lowered, which is a factor of lowering the analysis sensitivity.

[0005]

In order to improve the N / S ratio of 200 nm or less in the deuterium discharge tube according to the above-mentioned prior art, it is necessary to improve the radiance and to improve the radiance of the ultraviolet-transparent glass used as the light emission window. A method of reducing the plate thickness and a method of narrowing the radiation angle of light can be considered. To improve the radiance, there is a method of increasing the discharge current. However, the above method causes a short life and causes problems due to temperature rise. Also, it is an effective means to reduce the thickness of the UV transparent glass that becomes the window, but it is 0.3 m due to the glass strength.
About m is necessary, and the improvement in transmittance is several%. Therefore, an object of the present invention is to obtain a deuterium discharge tube with high radiance and low noise by eliminating the spread of the radiation angle when the light emitted in the narrowed portion of the discharge tube passes through the glass surface. .

[0006]

The above object is to provide a metal partition wall which surrounds a cathode and an anode coated with an electron emission material in a tube filled with deuterium or hydrogen and forms a discharge path from the cathode to the anode. In the deuterium discharge tube in which a partition plate having a small hole for narrowing the discharge path is provided in a part of the metal partition, by making the light emitting part, which is a part of the discharge tube container, flat. The expansion of the radiation angle that occurs when the emitted light passes through the glass can be prevented, and the above object can be achieved.

[0007]

FIG. 3 is a cross sectional view of the central portion of the electrode of the deuterium discharge tube of the present invention. In the figure, 1 indicates a bulb of a discharge tube container,
A part of the direction of extracting light is made flat, and the end of the discharge tube is welded to the stem to form a closed container, and the electrode part and deuterium gas are enclosed in the container. In the electrode portion, an electron emitting substance is applied to a filament made of a tungsten wire forming the cathode 6. There is a partition plate 3 which is a flat plate electrode made of molybdenum or the like for the anode 7, and a small hole 9 for narrowing the discharge is provided between the cathode and the anode. The small hole for discharge constriction has a diameter of 1 mm, and a recess is provided around the small hole to give directivity. The electrode is shielded by a metal partition wall 2 having a structure in which the electrode is covered with a metal plate such as nickel.

When a direct current voltage is applied between the cathode and the anode of the deuterium discharge tube having the above structure to cause discharge, deuterium gas emits light in each small hole portion, and a continuous spectrum strong in the ultraviolet region can be obtained. Since the emitted light is emitted from the flat portion provided on the bulb of the container, refraction occurring when passing through is small and the emission angle is not widened, so that the light collection efficiency is improved.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a transverse cross-sectional view showing a central portion of an electrode of a deuterium discharge tube showing a first embodiment of the present invention. The structure near the electrodes of the deuterium discharge tube is as described in the prior art. Reference numeral 1 denotes a discharge tube container, which is provided with a light extraction window 4 in which a cylindrical bulb is partially flat. The bulb serving as the discharge tube container is made of ultraviolet-transparent glass, and the end portion forms a sealed container welded to the stem made of hard glass having a thermal expansion coefficient similar to that of the same kind. A lead wire and an introduction wire for assembling the electrode are embedded in the stem. Reference numeral 2 is a metal partition wall surrounding the electrodes. 5 is a light extraction direction. The valve 1 is filled with several hundred Pa of deuterium gas. At the center of the bulb 1, a metal partition wall 3 that shields the electrode portion is made of a nickel plate, separates the cathode chamber and the anode chamber, and the metal partition wall 2 is sandwiched by a partition wall plate 3 made of nickel. A triple coil of a filament made of molybdenum such as BaO, SrO, CaO or the like coated on the filament, and a flat anode 7 made of molybdenum. Small hole 9
They are placed opposite to each other.

The member 8 for forming the small holes 9 provided in the partition plate is made of molybdenum and is fixed to the partition plate made of nickel by welding. The diameter of the small hole is 1 mm, and a depression is provided around the small hole to give the directivity of light. Further, in order to force the positive discharge column to pass through the discharge constriction, the anode chamber was provided with metal lids on the top and bottom, and the inside of the anode chamber was sealed.

Reference numeral 4 indicates a light extraction portion, and a flat ultraviolet transmission glass is used. This is because the light emitted from the discharge constriction portion is extracted from the plane portion.

When a deuterium discharge tube of the above structure is preheated by passing a current through the filament which is the cathode, a DC voltage is applied between the negative and positive electrodes to cause discharge of deuterium gas,
The positive column 10 is generated in the small hole portion that narrows the discharge path. The positive column generated in the small hole emits a strong continuous spectrum in the ultraviolet region.

FIG. 2 shows a second embodiment. The electrode structure is the same as that of the first embodiment, but the structure is such that a flat window 11 for extracting light is provided in the bulb 1 which constitutes the closed container. The bulb is a deuterium discharge tube having a structure made of hard glass, and a flat UV transparent glass is used for the light extraction window.

FIG. 3 is a diagram showing the relationship between the thickness of the window material and the noise at 195 nm in the deuterium discharge tube of the present invention and the prior art deuterium discharge tube. As shown in the figure, it is almost proportional to the thickness of the window material, and the noise increases as the thickness increases. This is due to a decrease in radiance due to a decrease in transmittance. Therefore, the thinner the window material is, the less noise the deuterium discharge tube can be obtained. When the window materials are compared with the same thickness, the deuterium discharge tube of the present invention has a noise level of about half that of the prior art.

With the deuterium discharge tube having the above-mentioned simple structure, light can be obtained with a narrow emission angle without widening the emission angle due to the refraction when passing through the glass, unlike the light emitted from the conventional concave glass. Therefore, high luminance can be obtained in a short wavelength region of 200 nm or less, and a deuterium discharge tube with low noise can be obtained.

[0016]

The deuterium discharge tube of the present invention has a simple structure, as shown in FIG.
2 becomes noise, and by using the deuterium discharge tube of the present invention, there is an effect of further improving the analysis sensitivity of the liquid chromatograph and the analysis device that performs analysis by absorption of light.

[Brief description of drawings]

FIG. 1 is a transverse cross-sectional view of a central portion of an electrode of a deuterium discharge tube showing a first embodiment.

FIG. 2 is a cross-sectional view of an electrode center portion of a deuterium discharge tube showing a second embodiment.

FIG. 3 shows noise characteristics of a deuterium discharge tube in a short wavelength region.

FIG. 4 is an external view showing a conventional example of a deuterium discharge tube and a cross-sectional view of the center of an electrode.

[Explanation of symbols]

1 ... Bulb, 2 ... Electrode enclosure, 3 ... Partition plate, 4 ... Light extraction window, 5 ... Light extraction direction, 6 ... Cathode, 7 ... Anode, 8 ...
Small hole member, 9 ... Small hole, 10 ... Sunlight column, 11 ... Projecting window,
12 ... Stem, 13 ... Introduction line.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Ichikawa 888 Fujibashi, Ome-shi, Tokyo Hitachi Ltd. Living Equipment Division

Claims (5)

[Claims] 1. A tube filled with deuterium or hydrogen gas,
Surrounding the cathode and the anode coated with an electron emitting material, providing a metal partition wall forming a discharge path from the cathode to the anode,
In a deuterium discharge tube in which a small hole for narrowing the discharge path is provided in a part of the metal partition, ultraviolet ray transmissive glass or hard glass is used for the cylindrical discharge tube container, and a part of the light extraction part is used. Alternatively, a deuterium discharge tube characterized by a container structure having a flat light emitting surface. 2. The deuterium according to claim 1, wherein the discharge tube container is provided with a portion projecting forward in the vicinity of the light emission, and has a container structure having a flat light emission window made of ultraviolet-transparent glass at the tip. Discharge tube. 3. The deuterium discharge tube according to claim 1, wherein the discharge tube container has a structure in which an ultraviolet transparent glass is used in a part of the vicinity of light emission. 4. The deuterium discharge tube according to claim 1, wherein the flat plate thickness of the portion of the ultraviolet transmitting glass which becomes the light emitting window is 1 mm or less. 5. A photodetector for a liquid chromatograph or a spectrophotometer, characterized by using as a light source a deuterium discharge tube having a structure comprising a container provided with the plane portion.