JPH0351051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charged particle mass spectrometer in which the number of particles and energy distribution vary over time.

The mass and energy of charged particles are usually analyzed by introducing the particles into an electric or magnetic field and using the fact that the rate at which they are deflected differs depending on their mass and energy.

If the beam condition does not change over time,
As used in commercially available mass spectrometers, it is possible to analyze mass spectra and energy spectra by temporally varying electric and magnetic fields. However, such a method cannot be used in the case of a beam that fluctuates over time, such as particles emitted from discharge plasma or the like. The present invention relates to an analyzer capable of simultaneously measuring the energy spectrum of a charged particle beam in which particles of different masses coexist and the number of particles and energy distribution vary over time.

1, 2, and 3 are examples of conventionally used or proposed analyzers.

Figures 1 and 2 show a 180 degree deflection type analyzer.
Electromagnetic fields are applied to the same area in a superimposed manner.
In the same figure, cells with the same number of charges, such as H ⁺ and D ⁺ ,
The case where two types of particle beams with different mass numbers are incident is shown as a representative example. An electrostatic deflection plate 2 housed in a vacuum container 1 applies an electric field to an electromagnet 3.
A magnetic field is generated by In the figure, the directions are the same. The figure also shows a case where the vacuum vessel itself also serves as the yoke of the electromagnet. The electromagnetic field exists in a region 4 defined by the area of the electrode plate and the area of the magnetic pole plate. H ⁺ incident on this region
In the mixed beam 5 of D + and D ⁺ , the momentum is analyzed in the direction perpendicular to the electromagnetic field according to the difference in the Ranu radii, and the mass is analyzed in the direction of the electromagnetic field due to the electromagnetic deflection difference.

Now, in such a configuration, since mass discrimination is also attempted to be performed between the electromagnetic pole plates, it is inevitably necessary to provide a large gap between the electromagnetic poles. Therefore, an electromagnet is required to have a large magnetomotive force, and an electromagnet is required to have a large magnetomotive force, and the electromagnet becomes large. In addition, as the distance between the electrode plates increases, the effect of disturbance of the electromagnetic field at the edge of the electrode plate, such as a fringe field, increases. In reality, this large effect complicates the analysis of charged particle trajectories and makes it difficult to design an analyzer.

On the other hand, the example shown in FIG. 3 is a method that has been considered in order to reduce the size of the magnet. That is, an attempt is made to reduce the size of the magnet by narrowing the gap between the magnetic poles by taking out the electrodes from between the magnetic poles and by reducing the deflection angle of the beam due to the magnetic field. This method can certainly be said to be an excellent method in principle. That is, in addition to the above-mentioned effects, if a particle detector is placed at the focal point of the beam by utilizing the lens effect of the electromagnet, the momentum resolution can also be improved. However, this method is not practical when considering actual design and manufacturing. The reason is that the magnetic field does not change discontinuously at the ends of the magnetic pole plate, but there is always field disturbance near the ends. On the other hand, the method shown in Figure 3 attempts to conduct analysis using this highly disordered region, and it is extremely difficult to accurately grasp the behavior of charged particles, so it is difficult to accurately grasp the behavior of charged particles. There are many difficulties in trying to increase the resolution.

The present invention has been made in view of these points, and it selects a deflection angle by a magnetic field of 180 degrees, and after being deflected by the magnetic field, passes through an electric field region to perform mass discrimination. Figure 4 shows its configuration. The figure shows an example of analysis of two types of beams, H ⁺ and D ⁺ . This method can be said to have the advantages of the methods shown in FIGS. 1 and 2 and the method shown in FIG. 3. In other words, by extending the electrode plate outside the magnetic pole plate, the gap between the magnetic poles is narrowed, thereby making the magnet smaller and reducing the area in which the magnetic field is disturbed. In addition, by increasing the magnetic field deflection angle to 180 degrees,
The influence of field disturbance at the magnetic pole tip on the particle beam trajectory can be reduced.

In addition, for the synergistic effect of the fringe field of the electric field and magnetic field, by reducing the magnetic pole gap and separating the electromagnetic field regions, the influence on the ion trajectory due to the large fringe field as shown in Figures 1 and 2 can be reduced. is made smaller.

Although the above method compensates for the other drawbacks of FIGS. 1, 2, and 3, the advantages of each method are preserved. For example, in both FIGS. 1 and 4, the magnetic field deflection angle is 180 degrees, and the magnetic field enters and exits perpendicularly. This simplifies work, assembly, and adjustment. Further, by making the electromagnetic field separate, as shown in FIGS. 3 and 4 compared to FIG. 1, not only does assembly become easier, but also a degree of freedom is given to the deflection method using the electric field. For example, as shown in Figure 4, by making the electrode plate into an appropriate shape, it is possible to select the deflection distance of the particles in the direction of the electromagnetic field, and it is possible to arrange the particle detectors in a straight line. .

As described above, by separating the electromagnetic field region and setting the magnetic field deflection angle to 180 degrees, the present invention can simplify the design and manufacture while taking advantage of the advantages of the conventional analysis method.

In the above-described embodiment, there are two types of particles, but the number of types of particles is not limited to two and can be expanded to many types. In addition, in order to make the analyzer more compact, the electromagnet and the vacuum container were integrated, but in this case, the two were separated and
It goes without saying that the magnet may also be of external type as shown in Figure 5.

[Brief explanation of drawings]

Fig. 1 is a top sectional view of a conventional method in which electromagnetic fields are superimposed, Fig. 2 is a side sectional view thereof, and Fig. 3 is a side sectional view showing a method in which the magnetic field deflection angle is reduced and the electromagnetic fields are separated. , FIG. 4 is a top sectional view showing an embodiment of the present invention, FIG. 5 is a side sectional view of FIG. 4, and FIG. 6 is a top sectional view showing another embodiment of the invention. 1...Vacuum container (also serves as an electromagnetic yoke), 2
... Electrostatic deflection plate, 3 ... Electromagnetic pole plate, 4 ... Electric field region, 5 ... Charged particle beam, 6 ... Collimator, 7 ... Output point, 8 ... Particle detector, 9 ... Coil, 10...Magnetic field region, 11...Vacuum container, 1
2...Electromagnet.

Claims (1)

[Claims] 1. In a charged particle mass energy analyzer that injects multiple types of charged particles whose number and energy distribution vary over time into an electromagnetic field and analyzes the mass and energy of the charged particles by the deflection action of the electromagnetic field, A particle detector that simultaneously analyzes the mass and energy of the particles by deflecting the incident charged particles by 180 degrees by the magnetic field, and then passing the electric field having the same or opposite direction to the magnetic field. A charged particle mass energy analyzer characterized in that it is made of a charged particle that is incident on a charged particle.