JPH0361306B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a quadrupole mass spectrometer tube used in a quadrupole mass spectrometer.

Conventional technology and problems A quadrupole mass spectrometer tube is divided into three parts: an ion source section, a quadrupole electrode section, and an ion detection section.
The assembly accuracy of the quadrupole electrode section has a significant effect on the performance of the analyzer, so the rod electrode spacing must be assembled with an accuracy of several microns or less. Since quadrupole electrode tubes must be electrically insulated from each other, they are often assembled onto a yoke material such as ceramic using screw bolts. Most electrodes are made of stainless steel cylinders, but some are made of molybdenum. This is because the coefficient of thermal expansion of molybdenum is about 1/3 that of stainless steel, which is close to that of ceramic. For this reason, when used repeatedly in a high-temperature atmosphere, etc., accuracy is less likely to deteriorate due to differences in thermal expansion coefficients, and better results can be obtained with molybdenum. However, molybdenum materials have the drawbacks of being very expensive and difficult to process. Recently, aluminum materials have been in the spotlight as ultra-high vacuum materials. This is because aluminum material decays radioactivity very quickly after being activated, is a good conductor of heat, is completely non-magnetic, and when treated with a special surface treatment, releases very little gas. This is because it has the following advantages. For this reason, many vacuum parts and devices such as vacuum chambers, pumps, valves, flanges, gaskets, and gauges have been made of aluminum. However, quadrupole mass spectrometer tubes have not yet been made of aluminum. This is because the coefficient of thermal expansion of aluminum is approximately three times that of stainless steel.
This is because it is difficult to maintain accuracy with repeated baking. Further, the quadrupole rod electrode is firmly fixed to the yoke material with stainless steel screw bolts. Therefore, in order to assemble the rod electrodes at intervals of several microns, in addition to the ultra-precision cutting of the rod electrodes, an ultra-precision assembly jig is required, and assembly requires skill, which reduces the product yield. Unfortunately, the products had become extremely expensive. In addition, in the case of aluminum, it is difficult to make the screws aluminum, so you have to rely on stainless steel screws.However, with conventional assembly methods, it is difficult to firmly fix soft aluminum to the yoke material, and stainless steel screws are difficult to use. Therefore, the difference in coefficient of thermal expansion between different materials made it difficult to maintain accuracy. Quadrupole mass spectrometers are currently in great demand in industry, but for the reasons mentioned above, they have not become as widespread as vacuum gauges.

Objects and Means of the Present Invention The present invention was devised in view of the current situation, and its purpose is to provide a quadrupole rod electrode with a yoke material that determines the spatial position of a precision-machined quadrupole rod electrode. It is made of the same type of metal as the pole rod electrode to eliminate distortion due to the difference in thermal expansion coefficient between the quadrupole electrode part and the yoke material, and the method of attaching the quadrupole rod electrode to the yoke material is an insulated one. We use a complete fitting method using pins and sleeves, without any firm fixation, and allow the expansion and contraction to occur freely depending on the coefficient of thermal expansion.
The purpose is to prevent distortion in the yoke material, pins, etc., and to maintain accuracy even when used in a high-temperature atmosphere. In other words, since it is not tightly fastened and uses a method that allows thermal expansion to escape, it has become possible to manufacture quadrupole analysis tubes even with aluminum, which has a high coefficient of expansion, which had been considered difficult in the past.
In addition, since it is installed by completely fitting, no assembly jig is required as long as the precision of the parts is improved.
Anyone can easily and reliably assemble the product without requiring any skill, and the product yield can be significantly improved. As a result, it is possible to achieve dramatic cost reductions, and the performance of the quadrupole analysis tube is also unprecedented, making it possible to provide groundbreaking inventions that meet the needs of the industrial world. It was made.

Embodiment Hereinafter, the present invention will be explained by way of an embodiment shown in the drawings.

FIG. 1 is a partially cutaway perspective view of a quadrupole analysis section for explaining the present invention. 1 is an aluminum alloy rod electrode with a diameter of 8.000 mm and a length of 100.0 mm, which has been precision-machined to a mirror finish. At both ends, precision-polished ceramic pins 4 and 5 with a diameter of 4.000 mm are fitted. Holes 9 and 10 with a depth of about 5 mm are drilled. 2 and 3 have a diameter of 32.0 mm and a thickness of 5.0 mm.
Holes 8 and 11 with a diameter of 4.005 mm into which the ceramic pins 4 and 5 are inserted are made of aluminum alloy disk-shaped yoke material of mm.
are opened in each of the disk-like yoke members 2 and 3. These holes 8, 9, 10, 11 are drilled with positional accuracy on the order of microns to correspond to the four rod electrodes 1, and the distance between the centers of the holes facing the centers of the yoke materials 2, 3 is 15,000 mm. It is. Ceramic cloth shears 6 and 7 have an inner diameter of 4.05 mm, an outer diameter of 7.0 mm,
It has a thickness of 1.0 mm and is fitted into ceramic pins 4 and 5 to electrically insulate the quadrupole rod electrode 1 and the disk-shaped yoke members 2 and 3. The other three rod electrodes 1 are assembled in the following manner: hole 8-ceramic pin 4-ceramic cloth 6-hole 9 and hole 10-ceramic cloth 7-ceramic pin 5-hole 11.
are also fitted, and the quadrupole rod electrode 1 and yoke material 2,
3 is integrally structured. Furthermore, the inner diameter of the yoke materials 2 and 3 into which the four rod electrodes 1 are fitted is
It is fitted into an aluminum metal cylindrical case 12 with a diameter of 32.05 mm and a length of about 120 mm. By the way, the above yoke material 2,
3 is made of the same type of metal as the quadrupole rod electrode 1 to prevent distortion due to the difference in thermal expansion coefficient between the quadrupole rod electrode 1 and the yoke materials 2 and 3. There is.

In this way, the four rod electrodes 1 are electrically insulated from each other, and are spaced apart from each other at a constant distance parallel to each other with high accuracy on the order of microns. Therefore, the rod electrode 1 is connected to the ceramic pins 4 and 5.
Not only can the assembled rod electrode 1 and yoke members 2 and 3 rotate freely within the cylindrical case 12,
No twist occurs between the parallel rod electrodes 1.
Furthermore, the vertical expansion and contraction of the rod electrode 1 can be freely changed.

In this way, in the assembly method of the present invention, the four rod electrodes 1, the two yoke materials 2, 3, the eight ceramic pins 4, 5, the eight ceramic washers 6, 7, and the cylindrical case 12 are assembled. Because no excessive force is applied to the quadrupole rod electrode, no distortion occurs.Even if soft aluminum material with a high coefficient of thermal expansion is used for the quadrupole rod electrode 1, and it is used in a high temperature atmosphere, no distortion will occur at all. Therefore, the accuracy of the analysis tube is always maintained at an appropriate level. Furthermore, since the assembly method of this invention is a complete fit-in method, the performance of the quadrupole analysis section is determined only by the finishing accuracy of the parts during cutting, and does not include factors such as the accuracy of the assembly jig and the level of assembly skill. Not possible. Therefore, the yield of the quadrupole analysis unit assembled by the method of the present invention is very high.
If it is made into a product, it will be possible to significantly reduce costs. 13 is an ion exit, and 14 is an ion entrance. In addition, the rod electrode 1, yoke materials 2, 3, ceramic pins 4, 5, ceramic washers 6, 7, pin insertion holes 8, 9, 10, 11,
The dimensions of the cylindrical case 12 and the like can be changed as appropriate during implementation.

FIG. 2 is a cross-sectional view of one embodiment of a full-size quadrupole mass spectrometer tube assembled in accordance with the present invention. In this embodiment, the yoke material 3 is fixed to the outer cylindrical case 12 with threaded bolts 27. However, even in this case, the other yoke material 2
is fitted with only a small gap between it and the support base 26 of the cylindrical case 12, so the quadrupole rod electrode 1 and the yoke material 2 are still free from expansion, contraction and twisting. It is clear that no force is generated. 15 is a hemispherical anode electrode of the ion source; 16 is a hemispherical filament of the ion source;
17 is a hemispherical shield electrode, 18 is an ion extraction electrode, 19 is an ion source insulator, 20 is a lead wire, 2
1 is a suppressor electrode, 22 is an ion collector electrode, 23 is a collector shield electrode, 24 is a vacuum terminal, and 25 is a flange.

Further, in the embodiment shown in FIG. 2, the ceramic pin 4 is constructed in the shape of a pipe. This is a conductor 28 that is used to apply a high frequency voltage to the quadrupole rod electrode 1 through the pipe-shaped ceramic pin 4.The conductor 28 is made of thin and soft aluminum wire or copper wire. , so as not to impede the free movement of the quadrupole rod electrode 1. Therefore, the conductor 28
Since the protrusion is parallel to the axis, there is no need to damage the rod surface, and lathe processing when cutting the rod electrode is also easy, making it possible to provide highly accurate parts.

The spectrum shown in Figure 3 is a mass spectrometry spectrum of alcohol vapor obtained by the quadrupole mass spectrometer tube shown in Figure 2.
The number indicates the mass number, and the height indicates its strength. As is clear from this figure, each spectrum is approximately symmetrical and has an ideal shape with a slight bulge at the top, indicating extremely high resolution. The total sensitivity of the entire spectrum is 3×10 ^-3 A/3 without using a secondary electron multiplier.
torr, and has a sensitivity that is about an order of magnitude higher than conventional analysis tubes.

The fact that we were able to provide such a high-sensitivity, high-resolution quadrupole mass spectrometer tube is due to the effectiveness of the present invention, which employs an assembly method that involves complete fitting.

In the embodiment shown here, the four rod electrodes 1 and the yoke materials 2 and 3 are insulated and connected and assembled using ceramic pins 4 and 5, but the assembly method by fitting is limited to this pin method. Rather, as shown in FIG. 4, at least one end of each of the four rod electrodes 30 is machined to be thinner than the rod diameter, and insulating sleeves 31 and 32 made of ceramic or the like are covered with the yoke material 29. It may be fitted into a hole, or as shown in FIG. 5, the yoke material 33 itself may be made of an insulating material such as ceramic, and the rod electrode 30 may be fitted into a hole drilled therein.

Since the quadrupole mass spectrometer tube according to the present invention is constructed as described above, the attachment of the quadrupole rod electrode to the yoke material is not as firm as in conventional ones, and therefore, due to the coefficient of thermal expansion. If the quadrupole rod electrode expands or contracts, it can be released by allowing the expansion or contraction to occur freely, so it is possible to reliably prevent distortion from occurring in the quadrupole rod electrode, yoke material, pins, etc. , it is possible to maintain accuracy even when used in a high temperature atmosphere. This also makes it possible to manufacture quadrupole analysis tubes using aluminum, which until now has been technically difficult to maintain accuracy through repeated baking due to its large coefficient of thermal expansion. The characteristics of aluminum include that the decay of radioactivity after activation is very fast, it is a good conductor of heat and is completely non-magnetic, and by applying surface treatment, the amount of released gas can be significantly reduced. It is possible to obtain a quadrupole mass spectrometer tube with high sensitivity and high resolution while being fully usable and having a simple structure. Furthermore, since the quadrupole rod electrode is completely fitted into the yoke material, as long as the precision of the parts is improved, there is no need for special assembly jigs, and anyone can easily assemble it without any skill. Moreover, it becomes possible to assemble the product reliably, and the yield of the product can be significantly improved. As a result, it is possible to dramatically reduce costs, and the performance as a quadrupole analysis tube is also unprecedented, making it possible to provide screen-like inventions that meet the needs of the industrial world. It is something.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway exploded perspective view of a quadrupole analysis section according to the present invention, FIG. 2 is a side sectional view of the entire quadrupole mass spectrometer tube equipped with the present invention, and FIG. 3 is an analysis tube of the present invention. The above mass spectrogram, FIGS. 4 and 5 are side sectional views showing other examples, respectively. 1 is a quadrupole rod electrode, 2 and 3 are yoke materials,
4 and 5 are ceramic pins, 6 and 7 are ceramic cushions, 8, 9, 10, and 11 are holes for pin insertion, and 12 is a cylindrical case.

Claims (1)

[Claims] 1. In a quadrupole mass spectrometer tube in which four rod electrodes are arranged parallel to each other at a constant distance by a yoke material and are electrically insulated, the quadrupole A quadrupole mass characterized in that the spatial position of the quadrupole rod electrode is determined by fitting at least one end of the rod electrode into the yoke material directly or with an electrically insulating material interposed therebetween and giving a certain degree of freedom. analysis tube. 2. The quadrupole mass spectrometer tube according to claim 1, wherein the two degrees of freedom are the degrees of freedom for rotation of the quadrupole rod electrode in the circumferential direction. Claim 1 characterized in that the degree of freedom is the degree of freedom for expansion and contraction of the quadrupole rod electrode.
Quadrupole mass spectrometry tube as described in section. 4. The quadrupole mass spectrometer tube according to claim 1, wherein the four degrees of freedom are the degrees of freedom for rotation and expansion/contraction of the quadrupole rod electrode. 5. The quadrupole mass spectrometer tube according to claim 1, wherein the yoke material is made of the same type of metal as the quadrupole rod electrode.