JPS5816596B2 - mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mass spectrometer having a plurality of ion focusing points including a focusing point located between two deflection fields installed in series, and particularly to a mass spectrometer having a plurality of ion focusing points near the intermediate focusing point. This invention relates to the structure of an ionic and molecule reaction box to be provided.

An example of the prior art will be explained with reference to FIG.

A ground potential plate 4 with a slit 3 of about 0.25 mm is provided at the focal point of the ion beam 2 which has been deflected and dispersed by the magnetic field 1, and after that a ground plate 4 with a slit 5 of about 0.5 mm is provided. 6, and both slits 3 and 5
A length 2cIIL between which an adjustable voltage 7 can be applied
The ion beam 2 is passed through slits 9 and 10 of about 0 and 5 mm provided at the inlet and outlet of this box, respectively, and the inlet 1 is insulated.
A part of the reaction gas introduced from 1 can enter and exit the reaction box 8.

The reaction gas is exhausted by the exhaust system 12, but the ion beam 13 after passing through the reaction phase becomes a focused beam 16 after being deflected by the electrostatic field between the opposing electrodes 14 and 15, and the ion beam 13 is turned into a focused beam 16, which is placed after the collector slit 17 at the second focusing point. It is detected by the secondary electron multiplier 18.

When some of the ions constituting the ion beams 2, 13 dissociate spontaneously or by collision with gas molecules before entering the electric field between the opposing electrodes 14, 15, they are decelerated (lower energy) by this reaction. ) The ions become another ion beam 16A that runs inside the original ion trajectory.

By lowering the electric field voltage, this beam is returned to its original orbit and can be received by the slit 1γ and the multiplier 18 with the main beam 16 that did not cause any reaction being deflected outward.

Reactant gas is poured from the inlet 11, and the ion beam 13
When measuring ion-molecule reactions by intentionally increasing the frequency of collisions between ions and the gas by increasing the surrounding partial pressure, the ions reacting outside the reaction box 8 will only be decelerated by the reaction. However, inside the reaction box 8, the ions decelerated before the reaction by the voltage 7 between the slits 3 and 9 are accelerated again after the reaction by the same voltage between the slits 10.6, so that the reaction ions outside the box This allows more precise reaction to be performed than in the case without a voltage application type reaction box.

Note that for ions that do not cause a reaction, the deceleration at the entrance of the reaction box and the acceleration at the exit of the reaction box cancel each other out, so it is the same as when there is no reaction box.

In order to measure ion-molecule reactions with high sensitivity, it is necessary to increase the frequency of collisions between ions and molecules, but it is necessary to prevent undesirable ion scattering phenomena and to increase the number of collisions with a small amount of reactant gas and a small exhaust system. In order to measure sensitivity, it is desirable to directly introduce the reaction gas into the reaction chamber and to increase the efficiency of differential pumping to reduce deterioration of the degree of vacuum in the external ion orbit.

The first object of the present invention is to reduce the dimensions of the reaction chamber to about 1 cfn or less, increase the internal pressure to about 103 Torr, and further reduce the external ion orbital region to about 10 Torr.
The aim is to maintain it at around r.

Conventionally, in this type of measurement, of the ions that have caused a collision reaction with a molecule, only those ions that fly in the same direction as the unreacted ions are targeted, and comparative measurements are made with themselves and the unreacted ions. If ions flying in different directions can also be detected and compared, ion-molecule reactions can be measured in more detail.

A second object of the present invention is to connect an insulated reaction box to a DC amplifier to capture and detect ions among the reaction ions that do not fly out of the box.

Furthermore, capturing all the ions incident on an electrode held insulated in the ion path, and measuring the amount of ions by connecting this to a DC amplifier has been well known for a long time as the Faraday collector method.

A third object of the present invention is to allow the reaction box described above to also be used as the Faraday collector by a simple switching operation from the outside.

Therefore, the features of the present invention are as follows.

(1) By providing at least one intermediate box to enclose the reaction box that communicates with the gas introduction tube, one or more intermediate chambers are sequentially provided on the outside, and the analysis tube, which is the outermost vacuum chamber, is evacuated. The intermediate chamber is evacuated by at least one differential exhaust system separate from the system.

(2) Keep the reaction box insulated from other parts of the ground potential, apply a potential to it to distinguish the reaction inside the reaction box from the reaction outside the box, or connect it to a DC amplifier to ionize the reaction products. I was able to capture some of the information.

(3) This reaction box was operated from outside the vacuum to prevent ions entering from the input loss lift from passing through and escaping to the opposite side, making it possible to measure the total amount of incident ions.

FIG. 2 is a cross-sectional view of the vicinity of the ion-molecule reaction phase including the ion orbital plane in one embodiment of the present invention, and FIG. 3 is a cross-sectional view of FIG. 2 along the ion orbit at right angles thereto.

The innermost reaction box 8 has a cylindrical shape coaxial with the reaction gas introduction pipe 11, and has three slits in its cylindrical wall, namely an inlet slit 9, an outlet slit 10, and a third anti-slit 19 at positions at right angles to each other. It is set in.

The outer cylindrical first intermediate box 20 is provided with inlet and outlet loss lifts 21, 22 along the ion trajectory.

The reaction box 8 and the intermediate box 20 form a first intermediate chamber, and the intermediate chamber is exhausted by a first exhaust system 23.

Further outside the first intermediate box 20 is a rectangular second intermediate box 24.
There are slits 3 and 5 that constitute the entrance and exit of ions.
are hat-shaped plates 4 each forming a part of the second intermediate outer box.
, 6, and the second intermediate box 24 and the first intermediate box 20 form a second intermediate chamber.

The second intermediate chamber is evacuated by a second exhaust system 25.

Outside the second intermediate box 24 is an analysis tube or vacuum chamber 26 that houses the main part of the ion trajectory, and is evacuated by the third exhaust system 12.

Overall, the slits 3, 21, 9, 10, and 225 are arranged in a straight line in this order, and the width of the slit 9 is as narrow as possible without interfering with the ion beam passing through the intermediate focusing point inside the innermost reaction box 8. , 10 is approximately 0.41n
m, slit 21.22 is approximately 0.5 mm, slit 3.5
The gas inlet pipe 11 is rotatably supported by an insulated bearing 28 having an airtight O-ring 27, and the lower central shaft 29 of the reaction box 8 is rotatably supported by an insulated bearing 30. It is constructed so that it can be rotated in 90° increments by a rotation lever mechanism 31 with a click stop similar to that of an inch-inch, and in the state shown, a variable voltage 7 is applied between the reaction box 8 and the surroundings (ground potential) through a contact 32. can be applied (state A).

When the reaction box 8 is rotated 90 degrees from this state A, the ion beam 2 entering from the slit 19 is captured by the wall of the box without penetrating, and at the same time the lever mechanism 31 is moved to the contact point 33.
is connected to a DC amplifier 35 via a fixed voltage power supply (battery) 34 of about 10 V for suppressing secondary electrons, and its output is supplied to a recording or indicating meter 36 (state B).

When the reaction box 8 is further rotated by 90 degrees, it assumes the beam penetration position again, but in this state, variable voltage is not applied as in the previous penetration state A, but as in the case of all incident ion trapping state B.
It is connected to an amplifier 35 via a battery 34 (state C).

When further rotated by 90°, the reaction box 8 again has the same function as in the incident all ion trapping state B, and the orientation of the inlet slit is 180° opposite to that in state B (state D).
.

When performing an ion-molecule reaction measurement as described as an example of the prior art, the ion penetration position in state A is used.

Highly efficient multi-stage differential pumping allows the density of reactant gas molecules inside the reaction box 8 to be maintained at 100 to 1000 times that outside the box, so even if the dimensions of the reaction box are reduced to ICrfL or less. It becomes possible to cause sufficient ionic and molecule reactions.

If the dimensions of the reaction chamber 8 are large, the positions of collision reactions with ions will be dispersed and dispersed, and this will cause a shift in the imaging position in the collector portion.As a result, the peak position will not be clearly displayed, and the peak shape will vary. However, according to the present invention, the dimensions of the reaction box can be reduced and the reaction positions can be concentrated, thereby improving the above-mentioned drawback.

Furthermore, since the density of the reaction gas in the reaction chamber can be increased, the ionic and molecular reactions are enhanced and emphasized, making it possible not only to perform highly sensitive measurements, but also to significantly reduce the amount of reaction gas used. .

If the intermediate focusing point of ions is located inside the reaction box 8, the dimensions of each slit can be reduced, so that the efficiency of differential pumping and the aforementioned effects based thereon are further enhanced.

When the intermediate focusing point is placed on the central axis of the reaction box 8, the above-mentioned effects are maximized.

Furthermore, by using the ion penetration position in state C, in addition to measuring reactive ions using the final stage detector, it is possible to directly capture and detect reactive ions that do not escape outside the reaction chamber.

Furthermore, when recording a spectrum at an intermediate focusing point by sweeping the magnetic field in the previous stage, or when performing ion optical adjustment while monitoring the beam focusing situation only by the magnetic field, if all ion trapping positions in state B are used, It can also be used as a Faraday collector for all ions at the intermediate focusing point.

In addition, when replacing the ion source and final stage detector located at both ends of the ion trajectory and using it as an electric field-leading type ion optical system, it is possible to simply operate from the outside without reinstalling the intermediate detector. Can be used as a Faraday collector for all ions.

In the embodiment shown and explained above, a method was explained in which three inlets are connected to independent exhaust systems 23, 25, and 12 for differential exhaust, but two of these exhaust systems, for example 23 and 25, are It is also possible to perform common exhaust with one exhaust system.

Furthermore, in the embodiment described above, the changeover switch mechanism 31 for connecting the reaction box to the variable voltage power supply 7 or to the DC amplifier 35 via the fixed voltage power supply 34 is synchronized with the rotation of the reaction box 8 itself. Although it is designed to be operated by the switch, it is also possible to switch this separately.

Furthermore, in order to switch between the ion penetration position and the total ion trapping position of the reaction box 8, it is also possible to move the entire reaction phase in the length direction of the slit to create a state where there is only an inlet and no outlet; It is also possible to trap all ions by covering the output loss lift for ion penetration without moving it.

Therefore, it is possible to make the reaction gas introduction pipe and the reaction box coaxially rotatable, to make the reaction box cylindrical, or to provide the third slit 19 at a position of 90 degrees with respect to the inlet and outlet slits 9.10. is not an absolute condition either.

Furthermore, when the reaction box is used as a Faraday collector, a fixed voltage may be applied to a separate slit electrode provided between the ground slit and the Faraday collector. It can be omitted in this case.

In principle, it is possible to share a fixed voltage power supply and a variable voltage power supply, and in practice, there is also a method of providing this power supply on the output side (low impedance side) of the amplifier.

Although the above description has been made regarding a dual-focusing mass spectrometer in which a magnetic field precedes the spectrometer, it can also be applied to an apparatus in which an electric field precedes, and generally any ion optical system having a plurality of deflection fields.

According to the present invention, a detector that also serves as an ion-molecule reaction phase is placed at the intermediate focusing point of a dual-focusing mass spectrometer or similar device, which not only enables more precise measurement of ion-molecule reactions, but also enables single-focus mass spectrometry. This has the effect of making analysis and adjustment using the ion optical system convenient, and significantly improving the usability and versatility of the device.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a conventional mass spectrometer, FIG. 2 is a cross-sectional view of a mass spectrometer according to an embodiment of the present invention near the intermediate focusing point, and FIG. 3 is a diagram similar to the line II-I in FIG. FIG. 2...Incoming ion beam, 3.21, 9...
... Input loss lift, 5, 22, 10 ... Output loss lift, 8 ... Reaction box, 11 ... Reaction gas introduction pipe, 12゜23.25 ... ...exhaust system,
19...3rd slit, 20...1st
Intermediate box, 24...Second intermediate box, 26...
・Analysis tube, 35...DC amplifier.

Claims (1)

[Scope of Claims] 1. An ion optical system including an analysis tube through which an ion beam passes, two deflection fields installed in series within the analysis tube and having an ion beam focusing point in the middle; A reaction box arranged on the path of the ion beam and provided with an inlet and an exit loss lift that do not obstruct the ion path, a reaction gas introduction pipe that supplies a reaction gas to the reaction box, and a reaction box surrounding the reaction box. an intermediate box arranged with a slit that forms at least one intermediate chamber between the analysis tube and the reaction box and does not obstruct the ion passage;
A mass spectrometer comprising a plurality of evacuation systems for differentially evacuation of the intermediate chamber and the analysis tube in multiple stages. Claim 1, characterized in that by applying the voltage, a reaction within the reaction box and a reaction at a ground potential portion outside the reaction box can be distinguished by a subsequent detector.
Our mass spectrometer. 3. The mass spectrometer according to claim 1, wherein the reaction box is insulated and connected to the input of a DC amplifier, thereby operating as a detector that captures ions generated by ion-molecule reactions. Device. 4. Claim 3, characterized in that by switching the insulated reaction box to a state where it has an entrance slit but no exit slit, it can be operated as a dedicated detector for the ion beam that has passed through the front deflection field. Mass spectrometer as described. 5. The reaction box is insulated and provided with a third slit, the reaction box is configured to be rotatable from outside the vacuum, and a voltage is applied between the reaction box and the ground potential intermediate chamber in conjunction with the rotation, or The mass spectrometer according to claim 1, characterized in that the connection of the reaction box to the DC amplifier input is switched. 6. Claims 1 to 5, characterized in that a reaction box is arranged surrounding the focal point of the ion beam.
2. The mass spectrometer according to any of the above.