JPH0358139B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a particle analyzer such as a neutral particle mass energy analyzer or a charged particle energy analyzer.

[Prior art and its problems]

Figures 1 and 2 show a conventional particle analyzer;
Reference numeral 1 denotes a vacuum container, and an entrance port 3, which is an entrance for the neutral particle beam 2, is provided on the side wall of the vacuum container 1. Inside the vacuum container 1, a charge exchange cell 4, magnetic poles 5a, 5b, electrodes 6a, 6b, and a particle detector 7 are accommodated, respectively, corresponding to the orbits of the neutral particles. The charge exchange cell 4 contains therein a charge exchange gas P that ionizes neutral particles, and also serves as an aperture that narrows the particle beam and shapes it into a parallel beam on the incident end side and the exit end side of the particle beam, respectively. Collimators 8 and 9 are provided. The magnetic poles 5a, 5b are provided with rectangular magnetic pole surfaces 10a, 10b whose longitudinal direction is the vertical direction in FIG. By energizing 11a and 11b, a magnetic field in a direction perpendicular to the plane of the paper in FIG. 1 is generated. Further, the electrodes 6a and 6b are made of trapezoidal plates whose width increases from the top to the bottom in FIG. , 10b and facing each other in parallel. Then, one electrode 6b is kept at a negative potential with respect to the other electrode 6a,
As a result, an electric field in the same direction as the magnetic field is formed between the electrodes 6a and 6b. In addition, 1 in the figure
3 is an exhaust port communicating with a pump (not shown) that exhausts the gas Q inside the vacuum container 1.

In the neutral particle mass energy analyzer configured in this way, the neutral particle beam 2 introduced into the vacuum vessel 1 from the entrance port 3 passes through the charge exchange cell 4, thereby The charges are exchanged with the charge exchange gas P and ionized, resulting in a charged particle beam 14. At this time, charged particle beam 1
4 is shaped into a parallel beam of a predetermined thickness and shape by collimators 8 and 9, which are provided at both ends of the charge exchange cell 4 and also serve as apertures.

Charged particle beam 16 passing through charge exchange cell 4
By being introduced into the magnetic field generated by the magnetic poles 5a and 5b, each particle receives a force in a direction perpendicular to the direction of movement of the particle and the direction of the magnetic field, and is deflected by 180° following a circular trajectory. . At this time, the radius of motion of each particle is determined by the kinetic energy of each particle. Therefore, each particle deflected by 180° is introduced into the electric field of the next stage at a position corresponding to its kinetic energy at the end of the magnetic field. Each charged particle moving in the electric field is attracted and deflected in the direction toward the electrode 6b. The amount of deflection of each particle at this time is determined by the mass of each particle.

In this way, each particle is incident on the particle detector 7 at a two-dimensional position determined by the mass and energy of each particle, and the mass and energy of each particle are measured.

By the way, in this type of analyzer, the mass spectrometry electrodes 6a, 6b are installed close to the magnetic poles. In addition, align the mounting positions of detectors for the same particle type,
To facilitate assembly, the distance between the electrode and the detector is made shorter for lower energy regions. The detector is usually housed in a grounded conductive container, and the magnetic pole and vacuum container are also grounded, so an asymmetric electric field is generated between the mass spectrometry electrode 6b, the magnetic pole 5b, and the detector 7, as shown in Figure 3. However, this adversely affects the trajectory of the particles to be analyzed. That is, at the particle incidence part R, an electric field leaks from between the electrodes due to the magnetic poles 5b approaching each other.
Also at the particle emission part S, an electric field leaks out due to the detector 7 being at the same polarity and at ground potential. In this way, the area where the electric field exists expands, so if the particles are excessively deflected or have low energy, the electrode 6b
This caused a problem in the design of the analyzer. Particles that are deflected above the electrode 6b, such as particles 14b and 14c in FIG. There was also the problem that some people were forced to do so.

[Purpose of the invention]

The present invention was made based on these problems, and its purpose is to suppress the asymmetric electric field generated between the electrode and the magnetic pole, and between the electrode and the detector, thereby improving the analyte. To provide a particle analyzer that allows particle trajectories to be easily grasped, makes it possible to measure low-energy particles that have hitherto been impossible to measure, and allows analysis to be performed in a wide range of energy ranges.

[Summary of the invention]

The present invention is a particle analyzer configured such that an auxiliary electrode is placed at the entrance/exit part of the mass spectrometry electrode to suppress the fringe field of the mass spectrometry electrode.

〔Effect of the invention〕

According to the present invention, since the asymmetric electric field generated between the mass spectrometry electrode and the magnetic pole and between the same electrode and the detector is suppressed, excessive deflection of the trajectory of the particle to be analyzed can cause low-energy particles to Collision between the electrodes can be prevented. Therefore, it is possible to design a simple analyzer that does not require consideration of an irregular electric field, and the energy range that can be analyzed is expanded.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained based on illustrated embodiments.

4 and 5 show an embodiment in which the present invention is applied to a neutral particle mass energy analyzer, and the same parts as in FIGS. 1 and 2 are designated by the same reference numerals. Therefore, a detailed explanation of the overlapping parts will be omitted.

The difference between this embodiment and the conventional example described above is that an auxiliary electrode 16, a new auxiliary electrode, and a
It is at the point where 17a and 17b were installed. In Figure 6,
Details of the electrodes are shown. The auxiliary electrode 16 installed on the particle incidence side R of the mass spectrometry electrodes 6a, 6b suppresses the electric field leaking from the mass spectrometry electrodes 6a, 6b,
Similarly, the particle exit side S of the mass spectrometry electrodes 6a, 6b
The auxiliary electrodes 17a and 17b installed in the auxiliary electrodes 17a and 17b suppress the electric field leaking from the electrodes, and both prevent the electric field area from expanding. By confining the electric field region between the mass spectrometry electrodes in this way, excessive deflection of the particles to be analyzed can be prevented. Further, the auxiliary electrode 17b suppresses the electric field generated between the detector 7 and the mass spectrometry electrode 6b, and prevents the particles 14b and 14c passing therebetween from being excessively deflected.

In the example given here, all the auxiliary electrodes are grounded, but depending on the usage conditions of the analyzer, a potential may be applied to the detector or the magnetic pole, so if necessary, apply a potential to the auxiliary electrodes and It may be used under conditions that maximize its effectiveness. In that case, the number of auxiliary electrodes can also be selected as required.

Although the present invention has been mainly applied to a neutral particle mass energy analyzer, it can also be applied to a charged particle analyzer by simply replacing the charge exchange cell 4 with a collimator. At this time, it goes without saying that in the case of negative ions or electrons, the direction of the applied magnetic field or electric field is reversed.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view schematically showing a conventional neutral particle mass energy analyzer, Fig. 2 is a cross-sectional view of the same device taken along line A-A in Fig. 1 and viewed in the direction of the arrow; Figure 3 is an explanatory diagram for explaining the fringe field of the electrode for mass spectrometry, Figure 4 is a cross-sectional view schematically showing a neutral particle mass energy analyzer according to an embodiment of the present invention, and Figure 5 is a diagram illustrating the same. FIG. 4 is a sectional view taken along the line BB and seen in the direction of the arrow, and FIG. 6 is an explanatory diagram schematically showing the electrode arrangement of the device. 1... Vacuum vessel, 2... Neutral particle beam, 3...
...Injection port, 4...Charge exchange cell, 5a, 5b
...Magnetic pole, 6a, 6b...Mass spectrometry electrode, 7...
...Particle detector, 8,9...Collimator, 10a,
10b...Magnetic pole surface, 11a, 11b...Coil,
12... Electrode support material, 13... Exhaust port, 14,1
4a, 14b, 14c...Charged particle beam, 15
...Electric force lines, 16, 17a, 17b...Auxiliary electrode, P...Charge exchange gas, Q...Exhaust gas, R
...Particle entrance section, S...Particle exit section.

Claims (1)

[Claims] 1. After the particles are deflected by a magnetic field, an electric field having the same direction or the opposite direction as the magnetic field is passed through the particles, and the particles after this passage are detected by a detector to determine the mass of the particles. 1. A particle analyzer for analyzing particles and energy, characterized in that the particle analyzer is equipped with an auxiliary electrode for suppressing an irregular electric field that is generated around the electrode that generates the electric field and disturbs the trajectory of the particles. 2. The particle analyzer according to claim 1, wherein the auxiliary electrode is provided between the electrode that generates the electric field and the magnetic pole that generates the magnetic field. 3. The particle analyzer according to claim 1, wherein the auxiliary electrode is provided between the electrode that generates the electric field and the detector that detects the particles.