A DC photoionization detection ultraviolet light source

Abstract

The present invention discloses a DC photoionization detection ultraviolet light source, which includes a first lamp body, a second lamp body, a first electrode and a second electrode. A plasma channel is provided at the center of the first electrode. The first electrode is arranged at the upper end of the first lamp body. The first electrode further includes an insertion end, which is arranged at one end of the first electrode close to the first lamp body, and the insertion end abuts against the inner wall of the lower end of the first lamp body. A first through hole is provided on the bottom surface of the first lamp body. One end of the plasma channel communicates with the first through hole through the insertion end. A sealing member is provided at one end of the plasma channel. The second electrode is arranged at the lower end of the first lamp body, and the second lamp body is arranged at the lower end of the second electrode. A second through hole is provided at the center of the second electrode. One end of the second through hole communicates with the first through hole, and the other end of the second through hole communicates with the second lamp body. An ultraviolet lamp window is provided at one end of the second lamp body. The present invention provides a DC photoionization detection ultraviolet light source, which reduces the generation of miscellaneous gas molecules and prolongs the service life of the ultraviolet lamp.

Description

Technical Field

[0001] The present invention relates to the technical field of photoionization detection equipment, and particularly to a DC photoionization detection ultraviolet light source. Background Technique

[0002] Photoionization detection technology has high sensitivity and can detect compounds in the ppb level. Therefore, it has high application value in trace analysis under industrial and laboratory conditions and environmental pollution control. Since the 1970s, some chemical analysis instruments have begun to be equipped with photoionization detectors (PIDs).

[0003] In a photoionization detector, the gas to be measured absorbs photons emitted by an ultraviolet lamp that are higher than the ionization energy of gas molecules, generating ionization. Under the action of an external electric field, charged particles are deflected to form a weak current. The generated weak current is generally converted into a voltage value that can be easily measured by using a large resistor. Since the concentration of the measured gas is linearly related to the photoionization current within a certain range, the concentration of the detected gas can be known by detecting the response value of the photoionization detector, thereby determining whether the measured gas exists or exceeds the standard. The working principle of the photoionization detector structure is as Figure 1 shown.

[0004] Photoionization detectors are currently used in gas chromatographs for analyzing multi-component mixtures and are widely used in gas analyzers for determining air pollution. An important reason for the wide application of photoionization detectors in gas analyzers is that the photon energy emitted by the ultraviolet lamp is sufficient to ionize most air pollutants, while not sufficient to ionize pure air components, and the components of pure air have no effect on the ionization current.

[0005] In the past few decades, the design of the ultraviolet lamps used in photoionization detectors has hardly changed. The German company Heraeus is one of the most famous producers of such ultraviolet lamps. Among them Figure 2 describes the design of a DC ultraviolet lamp produced by Heraeus, which is also a typical design of DC ultraviolet lamps of other manufacturers. This lamp is mainly made of glass. Metal rings 1 and 2 used as electrodes are welded to the glass shell 3. The ultraviolet lamp window 4 is bonded to the lamp body using a high-temperature inorganic adhesive. All DC-type ultraviolet lamps have a tubular structure 5 inside, which serves as a discharge channel. When the ultraviolet lamp is working, due to high-speed moving electrons hitting inert gas molecules, a plasma 6 will be generated in the hollow part of the tubular structure 5. This plasma 6 is the main source of vacuum ultraviolet rays.

[0006] During the operation of the ultraviolet lamp, the plasma 6 interacts with the column of the tubular structure 5, releasing molecules such as O2, CO, CO2, and H2O, which causes the gas composition inside the ultraviolet lamp to gradually change. Since the impact of high-speed electrons on inert gas molecules is the main source of vacuum ultraviolet rays, this will lead to unstable discharge, changes in the radiation spectrum, and a decrease in the vacuum ultraviolet radiation intensity, which means the failure of the ultraviolet lamp. Summary of the Invention

[0007] The purpose of the present invention is to provide a DC photoionization detection ultraviolet light source, which reduces the generation of miscellaneous gas molecules and extends the service life of the ultraviolet lamp.

[0008] The technical solution adopted by a DC photoionization detection ultraviolet light source disclosed by the present invention is as follows:

[0009] A DC photoionization detection ultraviolet light source includes a first lamp body, a second lamp body, a first electrode, and a second electrode. A plasma channel is provided in the center of the first electrode. The first electrode is arranged at the upper end of the first lamp body. The first electrode further includes an insertion end, which is arranged at one end of the first electrode close to the first lamp body, and the insertion end abuts against the inner wall of the lower end of the first lamp body. A first through hole is provided on the bottom surface of the first lamp body. One end of the plasma channel is communicated with the first through hole through the insertion end. A sealing member is provided at one end of the plasma channel. The second electrode is arranged at the lower end of the first lamp body. The second lamp body is arranged at the lower end of the second electrode. A second through hole is provided in the center of the second electrode. One end of the second through hole is communicated with the first through hole, and the other end of the second through hole is communicated with the second lamp body. An ultraviolet lamp window is provided at one end of the second lamp body away from the second electrode.

[0010] As a preferred solution, the first electrode and the second electrode are made of tungsten alloy material, and the tungsten content of the tungsten alloy material is greater than 20%.

[0011] As a preferred solution, the sealing member, the first electrode, the first lamp body, the second electrode, the second lamp body, and the ultraviolet lamp window are all bonded with high-temperature inorganic adhesives.

[0012] As a preferred solution, a first boss is provided on one side of the first electrode close to the first lamp body, and the first boss is embedded in the first lamp body.

[0013] As a preferred solution, a second boss is provided at one end of the first lamp body close to the second electrode, and a groove is provided on the second electrode corresponding to the second boss, and the second boss is snapped into the groove.

[0014] The beneficial effects of a DC photoionization detection ultraviolet light source disclosed by the present invention are as follows: By arranging a first electrode and a second electrode at both ends of a first lamp body, a plasma channel is opened in the center of the first electrode. When the first electrode and the second electrode start to work, the first lamp body serves as a discharge channel, and plasma is generated in the plasma channel in the center of the first electrode. The plasma is then discharged through the insertion end into the first through hole, and then flows through the first through hole into the second through hole of the second electrode, enters the second lamp body through the second electrode, and finally emits stable ultraviolet light through the ultraviolet lamp window at one end of the second lamp body for gas detection. Through the above structure, when the first electrode and the second electrode are working, the plasma generated inside the first electrode has a relatively small contact area with the first lamp body, and the plasma only contacts the inner wall of the bottom through hole of the first lamp body, thereby reducing the generation of stray gas molecules compared with the traditional design scheme and extending the service life of the ultraviolet lamp. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the working principle diagram of the structure of a photoionization detector.

[0016] Figure 2 is the structural schematic diagram of a DC ultraviolet lamp of Heraeus Group.

[0017] Figure 3 is the structural schematic diagram of a DC photoionization detection ultraviolet light source of the present invention.

[0018] Figure 4 is the cross-sectional view of a DC photoionization detection ultraviolet light source of the present invention.

[0019] Figure 5 is the exploded view of a DC photoionization detection ultraviolet light source of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The present invention will be further described and explained below in conjunction with specific embodiments and the accompanying drawings of the specification:

[0021] Please refer to Figure 3 、 Figure 4 and Figure 5 , a DC photoionization detection ultraviolet light source, comprising a first lamp body 10, a second lamp body 11, a first electrode 12 and a second electrode 13. A plasma channel 121 is opened in the center of the first electrode 12. The first electrode 12 is arranged at the upper end of the first lamp body 10. The first electrode 12 further includes an insertion end 122. The insertion end 122 is arranged at one end of the first electrode 12 close to the first lamp body 10, and the insertion end 122 abuts against the inner wall of the lower end of the first lamp body 10. A first through hole 101 is opened on the bottom surface of the first lamp body 10. One end of the plasma channel 121 is communicated with the first through hole 101 through the insertion end 122, and a sealing member 14 is arranged at one end of the plasma channel 121.

[0022] The second electrode 13 is disposed at the lower end of the first lamp body 10, the second lamp body 11 is disposed at the lower end of the second electrode 13, a second through hole 131 is formed in the center of the second electrode 13, one end of the second through hole 131 communicates with the first through hole 101, the other end of the second through hole 131 communicates with the second lamp body 11, and an ultraviolet lamp window 15 is provided at one end of the second lamp body 11 away from the second electrode 13.

[0023] By disposing the first electrode 12 and the second electrode 13 at both ends of the first lamp body 10, a plasma channel 121 is formed in the center of the first electrode 12. When the first electrode 12 and the second electrode 13 start to work, the first lamp body 10 serves as a discharge channel, and the plasma is generated in the plasma channel 121 in the center of the first electrode 12. The plasma is then discharged into the first through hole 101 through the insertion end 122, and then flows through the first through hole 101 into the second through hole 131 of the second electrode 13, enters the second lamp body 11 through the second electrode 13, and finally emits stable ultraviolet light through the ultraviolet lamp window 15 at one end of the second lamp body 11 for gas detection.

[0024] With the above structure, when the first electrode 12 and the second electrode 13 are working, the plasma generated inside the first electrode 12 has a smaller contact surface with the first lamp body 10, and the plasma only contacts the inner wall of the bottom through hole of the first lamp body 10, thereby reducing the generation of stray gas molecules compared with the traditional design scheme and prolonging the service life of the ultraviolet lamp.

[0025] The first lamp body 10 and the second lamp body 11 are made of ceramic or glass, the ultraviolet lamp window 15 is made of MgF2 crystal, and the plugging member 14 is made of glass.

[0026] In the above solution, the first electrode 12 and the second electrode 13 are made of tungsten alloy material, and the tungsten content of the tungsten alloy material is greater than 20%. The first electrode 12 and the second electrode 13 are processed and manufactured by tungsten alloy, and the second electrode 13 can also form a second vacuum ultraviolet light emission source in addition to the plasma.

[0027] The first ionization energy of tungsten atoms is 770 kJ·mol-1, and the second ionization energy is 1700 kJ·mol-1. When the ultraviolet lamp is working, the tungsten atoms on the surface of the second electrode 13 will be ionized by high-speed electrons and high-energy ultraviolet photons. After that, a part of the tungsten ions will transition from the second ionization state back to the first ionization state, and at the same time, a photon will be released.

[0028] The energy E of this photon = 1700 - 770 = 930 kJ·mol-1

[0029] 1 ev / atom = 96.15384615384615 KJ / mol

[0030] E = 930 / 96.15384615384615 ≈ 9.7eV

[0031] Therefore, the photon energy released when tungsten ions transition from the second ionization state back to the first ionization state is close to 10 eV. In this case, the side of the second electrode 13 close to the ultraviolet lamp window 15 will become a stable vacuum ultraviolet light source. Even after the inert gas in the first lamp body 10 is contaminated by miscellaneous gases, the second electrode 13 can stably emit ultraviolet light around 10 eV, and the higher the purity of the tungsten alloy and the fewer the impurities contained, the fewer the corresponding impurity gases generated.

[0032] The plugging member 14, the first electrode 12, the first lamp body 10, the second electrode 13, the second lamp body 11, and the ultraviolet lamp window 15 are all bonded with a high-temperature inorganic adhesive. Through the plugging member 14 and the ultraviolet lamp window 15, the first lamp body 10 and the second lamp body 11 form a sealed structure to reduce the interference of external gases on the inside.

[0033] And a first boss 123 is provided on the side of the first electrode 12 close to the first lamp body 10. The first boss 123 is embedded in the first lamp body 10, which is convenient for assembling the ultraviolet lamp. When assembling, the first boss 123 can be snapped into the inside of the first lamp body 10, enabling the first electrode 12 to be better positioned and installed.

[0034] Similarly, a second boss 102 is provided at one end of the first lamp body 10 close to the second electrode 13. The second electrode 13 is provided with a groove 132 corresponding to the second boss 102. The second boss 102 is snapped into the groove 132. When assembling the first lamp body 10 and the second electrode 13, the second boss 102 can also be snapped into the groove 132 of the second electrode 13 to achieve better positioning and fixing.

[0035] The present invention provides a DC photoionization detection ultraviolet light source.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A DC photoionization detection ultraviolet light source, characterized in that, it includes a first lamp body, a second lamp body, a first electrode and a second electrode. A plasma channel is provided at the center of the first electrode. The first electrode is arranged at the upper end of the first lamp body. The first electrode further includes an insertion end which is arranged at one end of the first electrode close to the first lamp body, and the insertion end abuts against the inner wall of the lower end of the first lamp body. A first through hole is provided on the bottom surface of the first lamp body. One end of the plasma channel is communicated with the first through hole through the insertion end. A plugging member is provided at one end of the plasma channel. The second electrode is arranged at the lower end of the first lamp body. The second lamp body is arranged at the lower end of the second electrode. A second through hole is provided at the center of the second electrode. One end of the second through hole is communicated with the first through hole, and the other end of the second through hole is communicated with the second lamp body. An ultraviolet lamp window is provided at one end of the second lamp body away from the second electrode. The plugging member, the first electrode, the first lamp body, the second electrode, the second lamp body and the ultraviolet lamp window are all bonded by a high-temperature inorganic adhesive. A sealing structure is formed between the first lamp body and the second lamp body through the plugging member and the ultraviolet lamp window to reduce the interference of external gas on the inside.

2. The DC photoionization detection ultraviolet light source according to claim 1, characterized in that, the first electrode and the second electrode are made of a tungsten alloy material, and the tungsten content of the tungsten alloy material is greater than 20%.

3. The DC photoionization detection ultraviolet light source according to claim 1, characterized in that a first boss is provided on one side of the first electrode close to the first lamp body, and the first boss is embedded in the first lamp body.

4. The DC photoionization detection ultraviolet light source according to claim 1, characterized in that, a second boss is provided at one end of the first lamp body close to the second electrode, a groove is provided on the second electrode corresponding to the second boss, and the second boss is snapped into the groove.

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