JPH0521251Y2 - - Google Patents

Description

[Detailed Description of the Invention] <<Industrial Application Field>> The present invention relates to an improvement of the electrode holding mechanism of a quadrupole mass spectrometer.

<Prior art> A quadrupole mass spectrometer consists of four electrode rods, and by passing an alternating current signal between the pair of electrode rods, the composition is determined by restricting the ions that can pass through the center between the rods. It is a device for analysis. In a quadrupole mass spectrometer, the electrode configuration is simple, but it is important that the central axis of each electrode occupies the vertex of a square with sides of a constant length relative to the electrode radius. have strict dimensional accuracy (for example, the accuracy for the millimeter-order spacing between electrodes)
10 micron order) is required. The electrode rod holding mechanism is very important because its assembly accuracy is directly related to performance.

FIG. 3 is a front view showing a conventional electrode holding mechanism (Japanese Utility Model Publication No. 11280/1983). An electrode holder 31 made of alumina ceramic has a central shaft hole 32 and through holes 3 having circular cross sections arranged at equal intervals on the circumference around the center shaft hole 32.
3, each pole element 34 is inserted into the multi-permeable hole 33 and fixed with each screw 35.

FIG. 4 is a front view showing another conventional electrode holding mechanism (the above-mentioned publication). An electrode holder 41 made of alumina ceramic is formed into a ring shape having a circular through hole 42, and a plurality of poles 43 having a circular cross section and a spacer 44 made of alumina ceramic having a circular cross section.
The through holes 4 are arranged alternately in the circumferential direction.
2 and insert each pole element 43 into the holder 4 with each screw.
It is fixed at 1.

<Problems to be Solved by the Invention> However, the device shown in FIG. 3 does not provide sufficient resolution due to machining errors in the through hole 33, and there is also a risk of mechanical twisting. Moreover, the structure shown in FIG. 4 does not take measures against thermal expansion of the pole element 43, and it is difficult to attach the spacer 44, so its practicality is questionable.

The present invention was developed in order to solve the above problems.It is an electrode holding mechanism for a quadrupole mass spectrometer that is easy to assemble, has little change in electrode spacing due to temperature, and does not require fine adjustment after assembly. The purpose is to realize this.

<Means for Solving the Problems> The electrode holding mechanism of the quadrupole mass spectrometer according to the present invention has at least a surface made of an insulating material on each side of a square between four electrode rods whose surfaces are made of a conductor. two L-angles each having at least a surface made of an insulating material are arranged such that the two arms thereof face each other and sandwich the electrode rod and the spacer, and each of the two opposing arms of the L-angle and the two electrode rods and the spacer between them are penetrated and fixed by a rod whose surface is at least insulating, so that the four electrode rods are arranged so that the central axis of their circular cross section occupies each vertex of the square. It is characterized by

<<Operation>> Since the accuracy of the electrode position is determined by the machining accuracy of the electrode rod, the dimensional accuracy of the spacer, and the perpendicularity accuracy of the L angle, the above objective can be achieved.

"Example" The present invention will be explained in detail below using the drawings.

FIG. 1 is a front view showing an embodiment of an electrode holding mechanism of a quadrupole mass spectrometer according to the present invention, and FIG. 2 is a perspective view of its configuration. 11 to 14 are four electrode rods whose surfaces are at least made of a conductor and arranged so that the center axis of the circular cross section occupies each vertex of the square; 21 to 24 are the square electrodes between these four electrode rods 11 to 14; Spacers 31 and 32 are arranged on each side of the spacer, and at least the surface thereof is made of an insulating material. Two L angles 41 to 44 made of insulators are the L angles 31,
32, two opposing arms, two electrode rods therebetween, and a rod whose at least the surface is an insulating material, passing through the spacer; 5, a spring inserted into the tips of the rods 41 to 44; 6, the rods 41 to 44; 44 is a screw that is tightened and fixed at both ends. L-shaped angle 3
The arm 31a of 1 and the arm 32a of the L-shaped angle 32 are arranged in series, and the electrode rod 11 is penetrated by the rod 42.
12 and spacer 21 and the electrode rods 13 and spacer 23 are sandwiched between them, and the arm 31b of the L-shaped angle 31 and the arm 32b of the L-shaped angle 32 are electrodes that are similarly penetrated by the rod 43. The electrode rods 12, 13 and the spacer 22, which are penetrated by the rods 11, 14 and the spacer 24 and the rod 44, are sandwiched between them. It is preferable to use plate-shaped spacers 21 to 24 from the viewpoint of ease of machining. Rods 41, 42
and bars 43 and 44 pass through different planes so as not to intersect. During assembly, holes are made in the electrode rods 11 to 14, spacers 21 to 24, and L angles 31 and 32 at corresponding positions.

Specific numerical examples are shown below. Generally, when the distance between opposing electrodes is 2r _p , it is recommended for the analyzer configuration that there is a relationship between the electrode radius r _r and the following: r _r =1.1468×r _p (1). If r _p = 10 mm, then from equation (1) r _r = 11.468
mm. Therefore, the thickness t of the spacers 21 to 24 needs to be 7.424 mm. Note that the length of the electrode can be selected as appropriate.

According to the electrode holding mechanism configured as described above, the accuracy of the electrode position is determined by the machining accuracy of the electrode rods 11 to 14, the thickness accuracy of the spacers 21 to 24, and the perpendicularity of the L angles 31 and 32. Among these, it is easy to process the electrode rods 11 to 14 as high-precision cylinders, and the thickness of the spacers 21 to 24 and the L
It is not difficult to realize the right angles of the angles 31 and 32 with high precision. That is, the electrode position can be realized with high precision (on the order of 1 μm).

There are no adjustment points, and assembly is easy.

In addition, if the spacers 21 to 24 are made of ceramic or the like with a small temperature coefficient, even if r _r changes greatly,
Since r _p does not change much, the temperature coefficient of the electrode position can be made small. This is also superior to using metal in that it does not disturb the electric field that is formed.

Furthermore, if the electrodes are formed of ceramic and a conductor is attached to the surface by vapor deposition, sputtering, etc., changes due to temperature can be further reduced.

《Effects of the invention》 As described above, according to the invention, the electrode holding mechanism of a quadrupole mass spectrometer is easy to assemble, has little change in electrode spacing due to temperature, and does not require fine adjustment after assembly. It can be realized with a configuration.

[Brief explanation of the drawing]

Fig. 1 is a front view showing one embodiment of the electrode holding mechanism of the quadrupole mass spectrometer according to the present invention, Fig. 2 is a perspective view of the same, and Figs. 3 and 4 are conventional quadrupole mass spectrometers. FIG. 3 is a front view showing the electrode holding mechanism of the device. 11-14... Electrode rod, 21-24... Spacer, 31, 32... L angle, 31a, 31
b, 32a, 32b...arm, 41-44...stick.

Claims (1)

[Scope of utility model registration request] A spacer whose surface is made of an insulating material is placed on each side of the square between four electrode rods whose surface is made of a conductor at least, and two L-angles whose surfaces are made of an insulating material are arranged with two arms facing each other. the electrode rods and the spacer, and the two opposing arms of the L angle and the two electrode rods and the spacer therebetween are penetrated and fixed by a rod whose surface is at least an insulating material. An electrode holding mechanism for a quadrupole mass spectrometer, characterized in that four electrode rods are arranged so that the central axis of the circular cross section occupies each vertex of the square.