CN1021390C - Glow discharge tube for analysis - Google Patents

Abstract

Regarding the glow discharge tube as a sample excitation source for emission spectrum analysis, etc., it is characterized in that the pressure in the anode tube is kept constant due to exhaust through the narrow gap between the insulating tube surrounding the anode tube and the surface of the sample. Glow discharge can be performed between the sample and the sample. Since the insulating tube protrudes toward the sample side than the anode tube, even if sample vapor adheres to the exhaust passage, there is no short circuit between the anode and cathode, enabling efficient analysis.

Description

The present invention relates to a device for analyzing the components contained in materials by glow discharge, in particular to the improvement of glow discharge tubes.

Glow discharge is used as an excitation source for analyzing material composition. The sample is placed on the cathode side to generate a glow discharge between it and the anode. Due to cathode sputtering, the sample substance is scattered in the discharge area and is excited to emit light. The light can be taken out and analyzed by spectroscopy to analyze the material. A glow discharge tube for the above-mentioned emission spectrum analysis is known, for example, in the specification of Japanese Patent No. 760451 (Japanese Patent Publication No. 4921680).

What Fig. 3 shows is the model of the previous glow discharge tube, the anode tube T extends from the hollow anode body A with the light-taking window W in the front to the hollow part of the cathode body K, and the sample S is set and blocked. The hollow part of the cathode body K. The cathode body K and the anode body A are insulated by an insulating plate 1 . Inert discharge gas such as argon enters from the gas supply port IN, and is discharged from the exhaust port 01 opened on the anode body and the exhaust port 02 opened on the cathode body K. In this way, a glow discharge region is formed in the space inside the anode tube T. As shown in FIG. In this discharge area, the sample substance scattered due to cathode sputtering floats in a vapor state and is excited to emit light.

In the existing glow discharge tube, as mentioned above, the anode tube T is inserted into the hollow part of the cathode body K, leaving a gap _G4 , and the sample is placed in the form of a plug at one end of the hollow part, so that A glow discharge region is formed between the sample at the same potential as the cathode body K and the anode tube. In order to maintain normal glow discharge, the discharge gap _G3 between the end surface of the anode tube and the sample should be set according to the specified distance, and at the same time, the center of this discharge area must maintain an appropriate vacuum degree (2 ~ 20Torr). In the region, discharge is performed while forcibly exhausting air from the peripheral part of the anode tube.

In the above-mentioned existing glow discharge tube, the vapor of the sample will adhere to the two sides of the gap G ₃ and G ₄ along with the exhaust gas flow, bridging the anode tube T, the sample S and the cathode body K, which is easy to cause short circuit. In order to prevent such failures, it is necessary to remove the sample S and the cathode body K from the anode body A, and clean the surfaces of the gaps G ₃ and G ₄ several times. For samples with a lot of sputtering such as galvanized steel sheets, the actual Almost every analysis in the past requires a cleaning. Moreover, when assembling the discharge tube after such cleaning, the anode tube T and the cathode body K must not be in contact, so extra care must be taken. This kind of cleaning operation takes 15 minutes, and the real analysis time is 1-3 minutes, but it takes more than 5 times the actual time to complete. For the quality management of the manufacture of electroplated steel sheets, it becomes a big problem when continuous analysis is necessary. obstacles and hindrances. Furthermore, since the dimensions of the gaps G ₃ and G ₄ are changed every time disassembly and assembly work is performed, this causes deterioration in the repeatability of analysis results.

In addition, the gap G ₃ between the sample S and the end face of the anode tube varies somewhat with the material of the sample, the applied voltage, and the purpose of analysis. 0.5mm degree. At the same time, due to the need to maintain an appropriate pressure in the discharge area, the vacuum degree is in the range of 2 to 20 Torr, so the gap _G3 should be as narrow as possible, hoping to have a large exhaust resistance.

In the structure of the existing discharge tube, since the gap _G3 is stipulated according to the discharge gap, in order to increase the exhaust resistance of the discharge area and maintain the desired vacuum degree, the exhaust guide of the peripheral part of the anode tube The passage _G4 is made narrow and long. As a result, as described above, the adhesion of the evaporated product of the sample became the cause of the short circuit.

The object of the present invention is to eliminate the above-mentioned disadvantages of existing glow discharge tubes. In the present invention, an insulating tube is installed around the anode tube. The edge of the insulating tube protrudes toward the sample side than the anode tube, and a gap is formed between the insulating tube and the sample surface to form a discharge gap. Narrow exhaust passage, this gap acts as a resistance to exhaust airflow. The anode tube has an inner edge portion than the insulating tube surrounding it, and a glow discharge is generated between the anode tube and the sample. Therefore, even if the vapor of the sample substance adheres to both sides of the gap with the exhausted airflow, the bridge There will be no electrical short circuit.

Fig. 1 shows an embodiment (sectional view) of a glow discharge tube for emission spectrum analysis according to the present invention. Fig. 2 shows another embodiment (sectional view) of the glow discharge tube of the present invention. Fig. 3 is a schematic view showing a conventional glow discharge tube for emission spectrum analysis.

The present invention will be described in detail below according to the accompanying drawings. Fig. 1 is an example of implementation of a glow discharge tube for luminescence spectrum analysis used in the present invention. In FIG. 1 , the anode tube 2 connected to the anode body 1 is surrounded by an insulating tube 8 , and the edge portion of the insulating tube 8 protrudes toward the sample 4 side more than the anode tube 2 . The sample 4 is pressed and supported on the jacket part 3 through the conductive sample holder 5 and the elastic sample pressing plate 6, and is opposite to the end edge of the anode tube. The jacket part 3 is an insulating member, and the conductor 9 is embedded in the part facing the gap _G2 (exhaust guide passage). 14,15,16 are fixed bolts, and 17,18,19 are sealing rings that cut off the outside air. The positive voltage is supplied to the anode tube 2 through the anode body 1 , and the negative voltage is supplied to the sample 4 through the sample holder 5 . For example, sample 4 is a plated steel sheet and a steel sheet with analysis objects such as semiconductors. The discharge gas (argon) enters from the air inlet 10, and exhausts to the vacuum pump from the exhaust ports 11 and 12.

As described above, in the structure of the conventional glow discharge tube, the exhaust resistance to the discharge region is determined by the gap between the tip of the anode tube and the surface of the sample, that is, the set discharge gap. One of the characteristics of the present invention is that the exhaust resistance to the discharge area can be set separately from the discharge gap. In other words, since the anode tube 2 can be discharged independently, the distance to the sample 4 can be set to about 0.3 to 0.5 mm according to the analysis object and target, so that no short circuit due to the adhesion of the sample substance will occur. . On the other hand, since the resistance to the exhaust gas flow can be applied by the insulating tube 8, the gap G1 between the edge portion of the insulating tube 8 and the sample ₄ is narrower than the discharge gap _G0 by about 0.2mm. In this implementation example, the insulating tube 8 is a tube with a thickness of 2mm. To maintain an appropriate pressure in the discharge area, the very necessary exhaust resistance can be given by the gap _G1 . In FIG. 1 , the insulating tube 8 is fixed on the anode tube 2 with threads, and can move slightly in the axial direction. 24 represents a screw joint part.

In the above embodiment of FIG. 1, the inside of the anode tube and 2 maintains the most suitable pressure for glow discharge, and the same cathode sputtering occurs in the circular part of the sample 4 opposite to the anode tube 2. The generated sample vapor is discharged through the gaps G ₁ and G ₂ , and even if it adheres to the surrounding surfaces of the gaps G ₁ and G ₂ to form a bridge, the anode and cathode will not be short-circuited and will not affect the measurement light. Since the bridging occurs only on a part of the gap, it does not cause venting failure and the analysis can be carried out contiguously. In addition, a part not shown in the figure is provided inside the anode body 1, the jacket part 3, and the sample holder 5, and is used for cooling water passages. Furthermore, if adopt the form that the anode tube is installed inside the insulating tube. The shape of the outer surface can also be different from that of FIG. 1 .

Since the entire surface of the gap _G2 (exhaust guide passage) is an insulator, the voltage between the cathode and anode fluctuates unstablely, which deteriorates the analysis accuracy. Therefore, the conductor 9 is embedded in the jacket part 3 in FIG. 1 . For the same reason, when ions are attached to the surface forming the gap _G2 , since the attached surface is an insulator, the charge exists locally, the potential distribution becomes uneven, and a discharge occurs. Due to this discharge, the voltage between the anode and the cathode is affected. But owing to having conductor 9 electric potential distribution homogeneous one, can prevent above-mentioned voltage variation, moreover, conductor 9 is not directly connected with anode and cathode.

Fig. 2 is another implementation example of the present invention. Fig. 2 is also the same as Fig. 1, and it is a glow discharge tube for emission spectrum analysis, and the same parts as Fig. 1 are denoted by the same symbols. The difference from FIG. 1 is that the outer casing part 21 of the pressing sample 4 is a conductive member, and is installed on the anode body 1 by insulating connecting bolts through an insulating plate 22 . The negative voltage is supplied to the sample 4 through the casing part 21, and the casing part 21 and the sample 4 constitute a cathode. However, a negative voltage may also be supplied to the sample 4 from the sample holder 5 . The implementation example of this FIG. 2 also has the same effect as the example of FIG. 1 .

In the above-mentioned Fig. 1 and Fig. 2, even if there is a bridging caused by the adhesion of the sample substance in the gap _G2 (exhaust guide passage), no electrical short circuit occurs, so the glow discharge tube is assembled at one time. , in the future for a long period of time (almost permanently) it is not necessary to disassemble and clean the two sides of the exhaust guide passage _G2 for continuous use. In addition, since no electrical short circuit occurs even if a bridging occurs in the gap _G1 , only the air pressure in the anode tube is considered to be most suitable for the glow discharge, and the _G1 gap is adjusted. Actually, the insulator 8 and the anode tube 2 are screwed together, and the interval of _G1 can also be adjusted.

Another effect of the present invention is that even if the sample is deformed toward the anode tube due to atmospheric pressure, the support function of the insulating tube 8 prevents an electrical short circuit. Therefore, even if it is a thin material, there is no need to worry about a short circuit, and it can be analyzed, which greatly improves the practicality.

The above is an example in which it is used for the analysis of the emission spectrum, but the present invention is not limited to the analysis of the emission spectrum, for example, mass analysis is also applicable. In the case of mass analysis, shorten the anode body and anode tube, remove the generated sample ions, and apply an electromagnetic field to the The mass analyzer import for .

As mentioned above, the glow discharge tube of the present invention is suitable as an excitation source for samples such as emission spectrum analysis and mass analysis, and is also suitable for analysis devices for analyzing various material components such as plated steel sheets and semiconductor flakes.

Claims (3)

1, glow-discharge tube for analysis is characterized in that:

Ora terminalis part in relative anode tube, between across the regulation discharging gap, be configured to constitute the test portion of negative electrode, the outside by anode tube ora terminalis part, in the glow discharge tube of discharging gap part exhaust, at anode tube peripheral unit insulated tube, an end of this insulated tube is more side-prominent to test portion one than the ora terminalis part of sun level pipe, makes the exhaust channel of region of discharge between anode one negative electrode narrower than above-mentioned discharging gap in fact; And have the overcoat part, be used for and anode tube on form the exhaust path of navigation between the insulated tube outer surface adorned, raise solidating in predetermined gap simultaneously and decide test portion.

2, glow-discharge tube for analysis according to claim 2, above-mentioned overcoat partly are to have and anode and all unconnected electric conductor insulating component of negative electrode with the embedding of exhaust path of navigation contact portion.

3, glow-discharge tube for analysis according to claim 1, the insulated tube of its anode tube peripheral unit are to be fixed on the anode tube with screw thread, make it in the axial direction can minute movement.

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