JP2000243345A - Ion optical system of time-of-flight mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new ion optical system of a time-of-flight mass spectrometer capable of housing a long flight distance in a limited small space with a simple structure obtained by a combination of cylindrical electric fields. SOLUTION: Cylindrical electric fields E1 to E6 with identical shape of rotational angle 60 deg. and identical intensity are generated in a space between inner electrodes 1 to 6 and outer electrodes 1' to 6' being concentric circular cylindrical electrodes. The cylindrical electrodes E1 to E6 are arranged in rotational symmetry at equal intervals of 60 deg. with the axis O as the center to form a regular hexagonal ion orbit. A deflection electric field E0 for making a sample ion generated by an ion source incident toward the ion orbit. A deflection electric field E7 for externally taking sample ions flying in the ion orbit is arranged between the electric fields E1 and E6. An ion is made incident on one cylindrical electric field with a slight angle to a plane orthogonal to the axis O. The ion orbit gradually moves downward in the cylindrical electric field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion optical system of a time-of-flight mass spectrometer (TOFMS).

[0002]

2. Description of the Related Art In a time-of-flight mass spectrometer (TOFMS), based on the fact that sample ions accelerated with a constant acceleration energy have a flight speed according to the mass, the flight time required to fly a certain distance is determined. Measure and determine the mass.

[0003] In a time-of-flight mass spectrometer, higher mass resolving power can be obtained as the flight distance is longer, but if the flight distance is increased, the size of the apparatus cannot be avoided. Therefore, many attempts have been made to achieve a long flight distance while preventing an increase in size.

[0004] One of them is a motorway type device devised by Osaka University.
Ion optics with a flight distance of 27 m could be accommodated (Int. J. Mass Spect. Ion Proc., 66 (1985) 28)
3).

Recently, a multi-turn ion optical system for orbiting the same orbit several times has been proposed (the 46th Annual Meeting of the Mass Spectroscopy Symposium (1998), p.33-
p319-). In this method, the flight distance can be increased by making the ions orbit around the same track-like orbit many times.

[0006]

However, the motorway type device requires a large number of sector electric fields and has a complicated structure.

In addition, the multi-turn ion optical system requires a mechanism for implanting and extracting ions in a circular orbit at a proper timing, and the structure becomes complicated. Further, there is a disadvantage that only a specific ion group can be analyzed. Further, since the orbit is repeatedly made on the same orbit, fast ions and slow ions may be mixed. For this reason, it is considered difficult to analyze an unknown sample having multiple components.

The present invention has been made in view of the above-mentioned points, and has a relatively simple structure and can accommodate a long flight distance in a limited narrow space. It is intended to provide a system.

[0009]

According to a first aspect of the present invention, there is provided an ion optical system for a time-of-flight mass spectrometer having a plurality of cylindrical electric fields through which ions sequentially pass. The plurality of cylindrical electric fields are arranged such that ions emitted from the last cylindrical electric field are re-entered into the cylindrical electric field initially incident, and the ion orbit is inclined with respect to a plane orthogonal to the axis of the cylindrical electric field. It is characterized by being. Further, a second invention is an ion optical system of a time-of-flight mass spectrometer provided with a plurality of cylindrical electric fields through which ions sequentially pass, wherein the plurality of cylindrical electric fields have the same rotational direction and the total number of ions. The rotation angle is 360 °, the ions emitted from the last cylindrical electric field are arranged so as to be incident again on the first incident cylindrical electric field, and the ion orbit is inclined with respect to a plane perpendicular to the axis of the cylindrical electric field. It is characterized by being given.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view showing an embodiment of an ion optical system of a time-of-flight mass spectrometer according to the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. In FIG. 1, E
1 to E6 are cylindrical electric fields having the same shape and the same strength at a rotation angle of 60 °. Each cylindrical electric field E1 to E6 is generated in a space between inner electrodes 1 to 6 which are concentric cylindrical electrodes and outer electrodes 1 'to 6'.

As shown in FIG. 1, the six cylindrical electric fields E1 to E6 are arranged rotationally symmetrically at equal intervals of 60 ° about the axis O, so that a regular hexagonal ion orbit is formed. It is formed.

As shown in FIG. 2, electric fields E1 and E1
6, a deflection electric field E for causing sample ions generated by the ion source to be incident on a regular hexagonal ion orbit.
0 is arranged. Similarly, between the electric fields E1 and E6, there is arranged a deflection electric field E7 for taking out the sample ions flying in the regular hexagonal ion orbit to the outside.

In the above arrangement, the sample ions generated by the ion source fly from top to bottom in parallel with the axis O,
The light enters the deflection electric field E0. Then, the sample ions whose flight direction is bent by about 90 ° by the deflection electric field E0 are incident on the first cylindrical electric field E1, and thereafter, are sequentially turned into the cylindrical electric fields E2, E.
3, E4, E5, and E6, and re-enters the cylindrical electric field E1.

When the sample ions are deflected by the deflection electric field E0 and are incident on the cylindrical electric field E1, if the incident angle is selected so that the ions are incident along a plane perpendicular to the axis O, the trajectory of the sample ions is determined. Is on that plane,
They will orbit the same orbit. This is the same as the multi-turn optical system introduced in the conventional example.

On the other hand, in the present invention, the light is incident on the cylindrical electric field at a slight non-zero angle θ with respect to a plane perpendicular to the axis O. Therefore, as shown in FIG. 2, the ion trajectory gradually moves downward (in the direction of the axis O) in the cylindrical electric field.

Since the cylindrical electric field has no converging effect in the y direction (the direction of the cylindrical axis), the sample ions injected into the cylindrical electric field E1 descend along the ion trajectory so as to descend the spiral staircase. After five rounds, the beam enters a deflection electric field E7 provided in accordance with the height of the ion trajectory after five rounds between the cylindrical electric fields E1 and E6, and is extracted in the direction of the axis O. The extracted sample ions are detected by an ion detector (not shown).

If a beam as parallel as possible is used as incident ions, the spread in the y direction can be suppressed to about several mm even if the flight distance is set to 3 m, for example. Therefore, if .theta. Is selected so that the pitch shifted in the axial direction for each revolution is about 5 to 6 mm, ions traveling on adjacent orbits will not be mixed.

As described above, according to the present invention, a plurality of cylindrical electric fields are arranged so that the total rotation angle becomes 360 ° and the ions can orbit a plurality of times, and the ions are inclined with respect to a plane perpendicular to the axis of the cylinder. Into the cylindrical electric field, the ion trajectory can be shifted for each revolution in the direction of the cylindrical axis. Therefore, it is possible to realize a long ion trajectory in which the ions do not fly in the same trajectory and do not intersect in a limited space. Further, since the trajectory for implanting ions and the trajectory for extracting ions are separated from each other, there is no need to measure the timing of implantation and extraction, and the structure for implantation and extraction is simplified.

Table 1 shows that, in the ion optical system shown in FIG. 1, the radius of rotation of the cylindrical electric fields E1 to E6 was 5 cm, and the length of a straight orbit between the electric fields was 5 cm. Aberration coefficients (x) x), (x, a), (x) d) representing the convergence in the x direction for each revolution, and the time convergence, obtained by calculation for the case where ions are extracted from between E5 and E5 Are shown as (t┃x), (t┃a), and (t┃d). Table 1 Orbit (x┃x) (x┃a) (x┃d) (t┃x) (t┃a) (t┃d) Flight distance After one lap -0.12 0.74 0.56 1.43 0.45 -0.90 60cm After two laps -1.14 0.36 1.07 1.75 1.33 -0.96 120cm After 3 laps -1.28 -0.31 1.14 0.70 1.95 -0.34 180cm After 4 laps -0.41 -0.73 0.71 -0.90 1.83 0.55 240cm 4 + 4/6 After lap 0.92 0.58 0.04 0.15 0.01 0.09 280cm Table The aberration coefficients after 4 + 4/6 rotations in Example 1 are all extremely small, indicating that the ion optical system of the time-of-flight mass spectrometer has excellent convergence in the x direction and time convergence.
Also, in a space of only 20cm in diameter, 2m without any intersection
The above flight distance can be obtained.

The number of turns of the ions can be arbitrarily set by appropriately selecting the length (height) of the cylindrical electric field in the axial direction and the orbital pitch of the ion orbit. In addition, if the inclination angle θ at the time of implantation can be adjusted, it is possible to change the number of turns of the ions before reaching the extraction position even if the extraction structure is fixed.

The present invention can be modified without being limited to the above-described embodiment. For example, it is preferable to arrange an earth plate between the orbits in order to surely separate the orbits which are shifted by the orbit in the linear orbit portion between the cylindrical electric fields. It is also possible to arrange an aperture lens (Einzel lens) on at least one of the linear trajectories, and use this lens to converge in the y direction.

Further, in the above embodiment, six cylindrical electric fields having a rotation angle of 60 ° are arranged rotationally symmetrically. However, the present invention is not limited to this, and a plurality of cylindrical electric fields are arranged so that the total rotation angle becomes 360 ° and the circuit can rotate. Just combine them.

The structure for implanting ions into and out of the orbital orbits is not limited to the above embodiment, but may be modified. For example, a hole for implantation may be made in one of the outer electrodes for producing a cylindrical electric field, and ions may be implanted from this hole so as to be on the ion orbit.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an ion optical system of a time-of-flight mass spectrometer according to the present invention.

FIG. 2 is a diagram showing an AA cross section of the ion optical system of FIG. 1;

[Explanation of symbols]

 E1-E6: cylindrical electric field E0: deflection electric field for driving E7: deflection electric field for extraction 1-6: inner electrode 1'-6 ': outer electrode

Claims (3)

[Claims] 1. An ion optical system of a time-of-flight mass spectrometer having a plurality of cylindrical electric fields through which ions sequentially pass, wherein the plurality of cylindrical electric fields are firstly irradiated by ions emitted from the last cylindrical electric field. An ion optical system for a time-of-flight mass spectrometer, wherein the ion optics are arranged so as to be incident again on the cylindrical electric field, and the ion trajectory is inclined with respect to a plane orthogonal to the axis of the cylindrical electric field. 2. An ion optical system of a time-of-flight mass spectrometer having a plurality of cylindrical electric fields through which ions sequentially pass, wherein the plurality of cylindrical electric fields have the same rotation direction and a total rotation angle of 360. °, the ions emitted from the last cylindrical electric field are arranged so as to re-enter the first incident cylindrical electric field, and the ion trajectory is inclined with respect to a plane perpendicular to the axis of the cylindrical electric field. An ion optics system for a time-of-flight mass spectrometer. 3. The time-of-flight mass spectrometer according to claim 2, wherein the cylindrical electric field is composed of six cylindrical electric fields having the same rotation angle and rotation radius, and is arranged rotationally symmetrically. Ion optics.