JPS5812705B2 - Shitsuryoubun Sekikei - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention analyzes multicomponent gases simultaneously using multiple ion collectors.

This paper relates to the ion optical system of a so-called multi-collector mass spectrometer.

Conventionally, many types of magnetic field end faces of this type of mass spectrometer have been used, for example, a circular magnetic field in which both the entrance surface and the exit surface are circularly convex, as shown in Figure 1a, or a linear magnetic field, as shown in Figure 1b. Fan-shaped magnetic fields have been used.

In both figures, 1 is an ion entrance slit, 2 is an ion beam, 3 is an ion collector, 4 is an exit slit (collector slit), and 5 is a magnetic field.

In such a conventional ion optical system, the aberration on each collector slit is particularly large in the case of the circular magnetic field shown in Figure 1a, and in the case of the fan-shaped field shown in Figure 1b, the convergence point of each ion with a different mass number is The curvature of the connecting convergence curve is relatively large, making it difficult to move the collector, and the determination of the positions of the ion source and a large number of collectors is complicated.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide an ion optical system for a multi-collector mass spectrometer for simultaneous analysis of multi-component gases, which has good overall focusing and imaging characteristics. That is.

In order to achieve the above object, in the ion optical system of the present invention, the shape of the magnetic field end face at the point of ion incidence into the magnetic field is circular concave, and the shape at the exit point is the same for all separated ions with the same radius of curvature. It is composed of a circular convex surface with a center of curvature, and furthermore, ions are made obliquely incident on the circular concave magnetic field end face at the ion input point, and all separated ions are emitted perpendicularly to the circular convex magnetic field end face at the ion exit point. Configure.

As a result, the ions enter toward the center of curvature 0 of the circular convex magnetic field end face (output end face) as shown in Figure 2, are deflected and separated in the magnetic field, and then radially away from the magnetic field so as to diverge from point 0. It will be emitted to

According to this method, the magnitude of the aberration in the slit width direction on the imaging plane of the emitted ions is determined by the radius of curvature r of the concave magnetic field end surface (incidence end surface) shown in FIG. 2 under certain conditions on the light source side. The optimal r, ψ that is a function of the oblique incidence angle ψ and minimizes the aberration for ejected ions of a certain mass number.
The aberration in this case is sufficiently small compared to that in the optical system of the conventional method (for example, the method using a circular magnetic field shown in FIG. 1a).

Therefore, good convergence characteristics can be obtained by selecting an appropriate combination of r and ψ depending on the mass number range used.

The convergence property in the length direction of the collector slit, so-called steric convergence property, is mainly a function of ψ, and the overall convergence property including the width direction of the slit is determined by selecting an appropriate r, ψ depending on the mass number range used. By selecting a combination of , e can be significantly improved by selecting a combination of charge numbers.

At the same time, according to this method, all ions are deflected to diverge from point 0 as described above, so in the case of a fan-shaped magnetic field, only the distance l from point 0 to the convergence point and the ion beam deflection angle θ are used. The position of the imaging point can be determined more easily than in the case of a fan-shaped magnetic field. The range of mass numbers that can be approximated by a straight line increases, and the imaging characteristics are improved.

The present invention will be explained in more detail below using examples.

The optical system of the present invention is small (curvature radius of the output circular convex surface -5Q)
An embodiment of the ion optical system when applied to a mass spectrometer for simultaneous analysis of multi-component gases targeting the low mass region (M/e-4 to 50) will be described with reference to FIG.

In FIG. 2, when an ion beam 2 that enters through an entrance slit 1 is made to enter a magnetic field 5 toward the center of curvature 0 of the exit end face, the ions are deflected at a deflection angle θ as if they were diverged from point 0. It converges on the collector slit 4 at a distance l from .

Here, the radius of curvature r of the circular concave surface of the magnetic field at the ion incidence point is r, 31 mm, the oblique incidence angle ψ is ψ -24°,
Aberration Xa in the slit width direction and mass number M/ considering the influence of the edge magnetic field when the magnetic flux density and ion accelerating voltage are set so that the deflection angle θ becomes θ - 90° at M/e=31.
Figures 3a and 3b show the relationship between the slit width direction magnification MX, the slit length direction magnification My, and the mass number M/e under the same light source side conditions. This is shown in comparison with the original conventional case of a vertically incident circular magnetic field.

Here, the light source (ion source) is a linear light source with a length of 2 mr,
The ion beam divergence angles in the horizontal and vertical directions of the entrance slit are both 0.002 rad1.
%.

For Xa, the conventional incident end flux is significantly improved over M/e=4 to 50, and as a result, both resolution and brightness are greatly increased.

Also, the distance from the ion incidence slit to the magnetic field end face is 80
The relationship between 1, θ, and mass number when mr is shown in Figure 4, and from this it is easy to determine the collector position corresponding to any mass number (for example, He, H20, 02, etc. in Figure 2).
CO2) can be determined.

The shape of the convergence curve for M/e = 4 to 44 in this case is shown in FIG. 5 in comparison with the case of normal incidence in a 900 sector magnetic field (the case of FIG. 1b). The range of mass numbers that can be measured with one collector translation increases.

If the present invention is implemented as explained above, in a certain mass number range used, aberrations are small, 3D convergence is achieved,
It has convenience in handling multiple collectors.

It is possible to provide a multi-collector mass spectrometer for simultaneous analysis of multi-component gases that has good convergence and imaging conditions.

[Brief explanation of the drawing]

Figures 1a and b show an example of a conventionally used mass spectrometer for simultaneous analysis of multi-component gases, Figure 2 shows an ion optical system of a mass spectrometer according to the present invention, and Figure 3 i. and b are diagrams showing the relationship between aberration and mass number and the relationship between image magnification and mass number when the present invention is implemented, respectively, in comparison with the conventional method, and Figure 4 is when the present invention is implemented FIG. 5 is a diagram showing the relationship between the collector position and the mass number in FIG. In the figure, 1 is the ion incidence slit, 2 is the ion beam, 3 is the collector, 4 is the collector slit 5 is the magnetic field, r is the radius of curvature of the circular concave entrance end surface, ψ is the ion oblique incidence angle, and ■ is the circular convex surface. The distance from the center of curvature 0 of the exit end face to the collector slit, θ is the ion deflection angle, Xa
is the aberration size in the width direction of the collector slit, Mx,
My represents the image magnification in the width direction and longitudinal direction of the collector slit, M represents the mass in atomic mass units, and e represents the electric charge.

Claims (1)

[Claims] 1. In a mass spectrometer that analyzes multi-component gases by arranging multiple ion collectors simultaneously, the shape of the end face of the magnetic field that separates ions, the angle of exit of the ions relative to the end face of the magnetic field, and the angle of exit of the ions at the ion incidence point are determined by a circular concave surface and an oblique incidence, respectively. A mass spectrometer characterized in that the emission point has a circular convex surface having the same radius of curvature and the same center of curvature for all separated ions, and vertical emission.