JPH06243821A - Mass spectrograph - Google Patents

Abstract

PURPOSE:To obtain a mass spectrograph of a good accuracy, by preventing the generation of reverse electromotive force, improving the response of the magnetic field, improving the reproducibility of a mas spectrum, preventing the charge-up to the inside of the analizer tube of an ion beam, and preventing the generation of out gas owing to the temperature rise, when the magnetic field is scanned at a high speed. CONSTITUTION:An analizer tube 10 of a nonmagnetic body having a hollow to pass the accelerated ion, and magnetic poles 20 are provided, an opening O for magnetic poles 20 is provided to the analizer tube 10, the magnetic poles 20 are installed to the opening O through a vacuum seal, a surrounding surface 26A to surrounding the magnetic poles 20 is formed by the analizer tube 10, and the surrounding surface is made of an insulator. And the surrounding surface 26A is covered by an earthed conductive plate 26B, and a cutting hole 27 is formed to the conductive plate 26B of the cover to open the closed circuit by the inductive electromotive force depending on the change of magnetic flux of the magnetic poles 20. Furthermore, the discharge tube 10 is composed of a conductor of nonmagnetic body, and a rubber plate 28 is provided to a part of the surrounding surface of the conductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometer, and more particularly to a mass spectrometer suitable for mass analysis and energy analysis of charged particles. In particular, it is used for GC-MS that performs mass spectrometry by scanning a magnetic field at high speed.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. FIG. 4 is a principle diagram of a conventional mass spectrometer, FIG. 5 is a schematic explanatory view of an example of an ion separation unit of the conventional mass spectrometer, and FIG. 6 is a conventional mass spectrometer. It is an exploded view showing an example of an analysis tube.

In FIG. 4, the ion beam 2 accelerated in the ionization chamber 1 is separated in the ion separation unit 3 according to its mass and detected by the ion detection unit 6.
Next, the ion separation unit 3 of the mass spectrometer will be described.

As shown in FIG. 5, the ion separator 3 has an inverted C-shaped electromagnet 7 having a void, and electromagnetic coils 8a and 8b are wound around both ends of the electromagnet 7 facing the void. Opposing magnetic poles N and S are provided in the space, and a high-vacuum analysis tube 10 is arranged between the opposing magnetic poles N and S.

In the conventional mass spectrometer using the electromagnet, the analysis tube 10 has a thin non-magnetic material between the magnetic poles N and S.
For example, a bent stainless steel pipe was used. Since this analysis tube is sandwiched between narrow magnetic poles, the width through which the ion beam 2 passes is further limited, and its transmittance becomes small, resulting in insufficient analysis sensitivity.

If the inner width of the analysis tube 10 is increased in order to improve this drawback, the gap between the magnetic poles N and S becomes large, and the magnetic flux density is lowered, so that a sufficient mass analysis range cannot be obtained. . In the above method, for example, when the magnetic pole interval is 8 mm, the thickness of the analytical tube is 1 mm, the distance between the magnetic pole and the analysis is 1 mm, and the deformation of the analytical tube due to atmospheric pressure is 1 m.
Since there is about m, the inner width through which the ion beam passes is half, 4m.
It becomes m.

Therefore, the magnetic pole 2 as shown in FIG. 6 is further added.
0 and the analysis tube 10 are attached by the vacuum seal groove 23 via the vacuum seal to construct a vacuum container. In this method, all the magnetic pole gaps serve as passages for the ion beam 2, so that a high transmittance of the ion beam 2 can be obtained and a high analytical sensitivity can be obtained. However, even in this method,
There is a drawback in that an error occurs due to the slow change speed of the magnetic field strength due to the change in the frequency of the electromagnetic coil. In addition,
For example, Japanese Patent Publication No.
The technique described in Japanese Patent No. 4 is known.

[0008]

The above-mentioned conventional mass spectrometer has an advantage in that the decrease in the ion beam transmittance is reduced in the technique disclosed in Japanese Patent Publication No. 2-3264, for example. However, there were the following problems. The first problem is that the strength of the magnetic field between the magnetic poles changes due to the change in the frequency of the electromagnetic coil.
That is, the pattern of the mass spectrum changes depending on whether the magnetic field is scanned at a low speed or at a high speed.

This problem is that when the strength of the magnetic field in the analysis tube of a non-magnetic material surrounding the magnetic pole is changed, a counter electromotive force is generated in a direction of canceling the change in the strength of the magnetic field, and the counter electromotive force causes the strength of the magnetic field to change. It is considered that this is because a current flows in a direction that cancels the change in depth. The magnitude of the counter electromotive force differs between when the magnetic field is scanned at a low speed and when the magnetic field is scanned at a high speed, and therefore the magnitude of the current in the direction that cancels the change in the strength of the magnetic field also changes. In particular, even if the analysis tube is made of a non-magnetic material such as aluminum, this phenomenon is remarkable if it is a good electrical conductor.

The second problem is that the ions to be mass-analyzed exist in the analysis tube, so that the ions may fly to the inner wall of the analysis tube and be charged up, disturbing the trajectory of the ion beam. There is. This phenomenon occurs when the analysis tube is made of an insulator as a countermeasure for the first problem. Further, when the analysis tube is made of an insulator, it also serves as a vacuum container, so that outgas is generated due to temperature rise.

The present invention has been made in order to solve the above-mentioned problems of the prior art. The magnetic field generated by the back electromotive force is generated even when the frequency of the electromagnetic coil is changed at high speed and the magnetic field is scanned at high speed. It is a first object of the present invention to provide a mass spectrometer in which the magnetic field response is improved and the reproducibility of the mass spectrum is improved. A second object of the present invention is to prevent charge-up of the ion beam into the analysis tube, the ion beam has an accurate trajectory, and to prevent outgas generation due to temperature rise, which is highly accurate. It is to provide a mass spectrometer.

[0012]

In order to achieve the above-mentioned first object, the structure of the mass spectrometer according to the present invention is a device for mass-analyzing accelerated ions in a magnetic field, which allows accelerated ions to pass therethrough. A nonmagnetic analysis tube having a cavity and a pair of electromagnet magnetic poles are provided, the analysis tube is provided with openings for the magnetic poles, and the magnetic poles are attached to the openings via vacuum seals. An analysis tube is used to form a surrounding surface surrounding each magnetic pole to form a vacuum container, and the surrounding surface surrounding each magnetic pole of the analysis tube is an insulator. The analysis tube is made of an insulating material as a whole.

In order to achieve the above second object,
An apparatus for mass-analyzing accelerated ions in a magnetic field, comprising a non-magnetic substance analysis tube having a cavity through which the accelerated ions pass, and a pair of electromagnet magnetic poles, and the analysis tube has openings for each magnetic pole. The magnetic poles are attached to the openings through a vacuum seal, and a vacuum container is formed by forming a surrounding surface surrounding the magnetic poles by the analysis tube, and a surrounding surface surrounding the magnetic poles of the analysis tube. Is covered with a thin film plate of a conductor grounded, and a part of the thin film cover plate of the conductor is cut so as to open a closed circuit due to an induced electromotive force based on a change in magnetic flux of each magnetic pole. The analysis tube is made of a non-magnetic conductor, and a part of the surrounding surface surrounding the magnetic pole is an insulator vacuum seal.

[0014]

The operation of each of the above technical means is as follows. According to the configuration of the first invention, by surrounding the surrounding surface surrounding each magnetic pole of the analysis tube, that is, the surface in which the counter electromotive force based on the electromagnetic induction due to the change in the magnetic flux of the magnetic pole is induced is an insulator,
Even if the magnetic flux of the magnetic pole changes at high speed, the counter electromotive force is not induced, and the induced current is not generated, thereby improving the reproducibility of the mass spectrum. According to the configuration of the second invention,
Since the surrounding surface surrounding each magnetic pole of the analysis tube is covered with a thin film plate of a conductor grounded, and a part of the thin film cover plate of the conductor is cut, a closed circuit due to an induced electromotive force based on the magnetic flux change of the magnetic pole is formed. The chamber is opened and the ion beam is placed in the analysis tube.
It is possible to prevent ji-up and also to prevent outgassing due to temperature rise.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Each embodiment of the present invention will be described below with reference to FIGS. [Embodiment 1] FIG. 1 is an exploded view of an analysis tube of a mass spectrometer according to an embodiment of the present invention. In FIG. 1, 2 is an ion beam, 10 is an arc-shaped analytical tube, 20 is a magnetic pole, and 21
Is a metal fitting, 22 is a screw, 23 is an O-ring groove for a vacuum seal, 26A is a surrounding surface of an insulator, O is an opening, and C is a central axis of an arc-shaped analytical tube.

In the analysis tube of the mass spectrometer according to the first embodiment of the present invention shown in FIG. 1, the analysis tube 10 is made of an insulating material, has an arc shape, and has a central axis C, The cross section is a rectangular cylinder. An opening O is provided on each of the upper surface and the lower surface of the arc-shaped portion of the analysis tube 10, and a pair of magnetic poles 20 are arranged so as to cover the opening O, respectively. Each of the magnetic poles 20 has an extended edge portion 20A in the vertical and horizontal directions with respect to the opening O.
Is fixedly supported on the analysis tube 10 by a screw 22 via a press fitting 21. Here, an O-ring groove 23 for vacuum seal is provided on the contact surface of the analysis tube 10 with the magnetic pole 20, and a high degree of vacuum is maintained through the O-ring.

Each facing surface of each magnetic pole 20 has a convex portion 20B projecting into the opening O on the opposite side thereof. The convex portion 20B extends in the direction of the central axis C and its center. A taper structure is formed on the side surface of the trapezoid so that the cross section in any direction perpendicular to the axis C has a trapezoidal shape. The surfaces of the convex portions 20B facing each other are formed at the same height as the facing upper surface and lower surface of the analysis tube 10, respectively. As a result, the portion of the analysis tube 10 where the magnetic pole 20 is arranged and the portion of the analysis tube 10 where the magnetic pole 20 is not arranged have the same vertical width of the passage of the ion beam 2, and the analysis is performed. The side surface of the tube 10 surrounds the side surface of the convex portion 20B of the magnetic pole 20 and forms the surrounding surface 26A of the insulator.

Next, the function of this embodiment will be described. Magnetic pole 2
An electromagnetic coil (not shown) is wound around 0, and by energizing this coil, a magnetic field is generated through the electrode stone yoke. Generally, when the frequency of the voltage applied to the electromagnetic coil increases and the magnetic field is scanned at high speed, the analysis tube 1
Although the counter electromotive force is generated on the surrounding surface 26A of 0, the induction current of the counter electromotive force does not flow on the surrounding surface 26A because the analysis tube 10 is an insulator. Thereby, the magnetic field can be stabilized.

[Embodiment 2] Next, an embodiment of the second invention will be described. FIG. 2 is an exploded view of an analysis tube of a mass spectrometer according to another embodiment of the present invention. In FIG. 2, in the figure,
Since the same reference numerals as those in FIG. 1 are the same parts, detailed description will be omitted. Only new symbols will be described. 26B is an analysis tube 10
A conductive plate is provided along the surrounding surface of the conductive plate, and 27 is a cut hole provided in a part of the conductive plate 26B. The structure of the analysis tube 10 is almost the same as that of [Example 1].

In the present embodiment, a thin conductive plate 26B is installed along the surrounding surface of the analysis tube 10, and the conductive plate 26B is installed.
A cutting opening 27 is provided in a part of the upper part. The ion beam 2 exists inside the analysis tube 10, and the inner wall of the ion beam 2 may be charged by the ion beam 2 and disturb the trajectory of the ion beam 2. Thin conductive plate 26B along the surrounding surface
However, the charging by the ion beam 2 is prevented, and the cutting opening 27 prevents the formation of an electrically closed loop based on the counter electromotive force generated by scanning the magnetic field at high speed.

[Embodiment 3] Further, another embodiment of the second invention will be described. FIG. 3 is an exploded view of an analysis tube of a mass spectrometer according to still another embodiment of the present invention. In FIG. 3, the same reference numerals as those in FIG. 1 denote the same parts, and thus detailed description thereof will be omitted. Only new symbols will be described. Reference numeral 28 denotes an insulating rubber plate inserted between the cut openings 27. The structure of the analysis tube 10 is almost the same as in [Example 1] and [Example 2].

In the present embodiment, the analysis tube 10 is made of a good conductor and a non-magnetic metal, and a cutting opening 27 is provided in a part of the surrounding surface of the analysis tube 10, and the cutting opening 27 is provided between the cutting openings 27. A rubber plate 28 made of an insulating material is inserted to serve as a vacuum seal, to prevent electrification by an ion beam, and electrically based on a counter electromotive force generated by the cutting hole 27 scanning a magnetic field at high speed. Prevent the formation of closed loops.

[0023]

As described in detail above, according to the present invention, firstly, the frequency of the electromagnetic coil changes greatly, and even when the magnetic field is scanned at high speed, the generation of the magnetic field due to the back electromotive force is generated. It is possible to provide a mass spectrometer in which the magnetic field response is improved and the reproducibility of the mass spectrum is improved. Secondly, the ion beam is prevented from charging up into the analysis tube, the ion beam has a precise trajectory, and outgas due to temperature rise is prevented from being generated, providing a highly accurate mass spectrometer. can do.

[Brief description of drawings]

FIG. 1 is an exploded view of an analysis tube of a mass spectrometer according to an embodiment of the present invention.

FIG. 2 is an exploded view of an analysis tube of a mass spectrometer according to another embodiment of the present invention.

FIG. 3 is an exploded view of an analysis tube of a mass spectrometer according to still another embodiment of the present invention.

FIG. 4 is a principle diagram of a conventional mass spectrometer.

FIG. 5 is a schematic explanatory view of an example of an ion separation unit of a conventional mass spectrometer.

FIG. 6 is an exploded view showing an example of an analysis tube of a conventional mass spectrometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ion source 2 ion beam 3 electromagnet 6 detector 7 yoke 8a, b coil 10 arc-shaped analysis tube 20 magnetic pole 20A magnetic pole extended edge 20B magnetic pole convex portion 21 pressing member 22 screw 23 vacuum seal O-ring groove for use 26A Surrounding surface of insulator 26B Conductive plate 27 Cutting port 28 Rubber plate O opening C Central axis of arc-shaped analytical tube

Claims (4)

[Claims] 1. An apparatus for mass-accelerating accelerated ions in a magnetic field, comprising a non-magnetic substance analysis tube having a cavity through which the accelerated ions pass, and a pair of electromagnet magnetic poles. Is provided with an opening for attaching each magnetic pole, the magnetic pole is attached to the opening via a vacuum seal, and the analysis tube forms a surrounding surface surrounding each magnetic pole to form a vacuum container. In the mass spectrometer, the surrounding surface surrounding each of the magnetic poles of the analysis tube is formed of an insulator. 2. The mass spectrometer according to claim 1, wherein the analysis tube is made of an insulating material. 3. An apparatus for mass-accelerating accelerated ions in a magnetic field, comprising a non-magnetic substance analysis tube having a cavity through which the accelerated ions pass and a pair of electromagnet magnetic poles. Is provided with an opening for each magnetic pole, the magnetic pole is attached to the opening via a vacuum seal, and a surrounding surface surrounding each magnetic pole is formed by the analysis tube to form a vacuum container. In the analyzer, the surrounding surface surrounding each magnetic pole of the analysis tube is covered with a thin film plate of a grounded conductor, and a part of the covering plate is closed by an induced electromotive force based on the magnetic flux change of each magnetic pole. A mass spectroscope having a cutting section for opening a circuit. 4. The analysis tube is characterized in that the material thereof is made of a non-magnetic conductor and a part of the surrounding surface surrounding the magnetic pole is made of an insulating vacuum seal. Mass spectrometer.