JPH0534774B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a particle analyzer that analyzes the mass or energy of charged or neutral particles using a deflection field.

[Technical background of the invention and its problems]

Traditionally, particle analyzers have been used to analyze the mass or energy of charged particles and neutral particles by injecting a particle beam into a deflection field such as an electric field or a magnetic field, detecting the amount of deflection of each particle, and performing the above-mentioned physical quantity analysis. There are known devices that do this. Such a particle analyzer, for example, a neutral particle mass energy analyzer that analyzes the mass and energy of neutral particles such as H and D, is usually configured as shown in FIGS. 1 and 2. There is. That is, in the figure, 1 is a vacuum container, and an entrance port 3, which is an entrance for a neutral particle beam 2, is provided on the side wall of this vacuum container 1. Inside the vacuum container 1, there are charge exchange cells 4, corresponding to the orbits of the neutral particles,
Magnetic poles 5a, 5b, electrodes 6a, 6b, particle detector 7
are accommodated in each. The charge exchange cell 4 is
Charge exchange gas P that ionizes neutral particles inside
Apertures 8 and 9 are provided on the walls located at the incident end and the exit end of the particle beam to narrow down the particle beam and also serve as parallel collimators. The magnetic poles 5a and 5b are
It has rectangular magnetic pole faces 10a, 10b whose longitudinal direction is the vertical direction in FIG.
10b are arranged opposite to each other with a predetermined interval therebetween.
These magnetic poles 5a and 5b generate a magnetic field in a direction perpendicular to the plane of the paper in FIG. 1 by energizing the coils 11a and 11b wound around them. Further, the electrodes 6a, 6b are made of trapezoidal plates whose width increases from the top to the bottom in FIG. They are arranged opposite to each other in parallel with the surfaces 10a and 10b, and generate an electric field in the same direction as the magnetic field. Note that 12 in the figure is an exhaust port leading to a pump (not shown) that exhausts the gas Q inside the vacuum container 1.

In the neutral particle mass energy analyzer configured as described above, the neutral beam 2 introduced into the vacuum vessel 1 from the entrance port 3 undergoes charge exchange by passing through the charge exchange cell 4. Gas P
The charges are exchanged and ionized to form a charged particle beam 13. At this time, the charged particle beam 13
is shaped into a predetermined thickness and shape by apertures 8 and 9 provided at both ends of the charge exchange cell 4, and is exchanged into a parallel beam.

Charged particle beam 13 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 distributed on a straight line at a position corresponding to the energy at the end of the magnetic field from which each particle is emitted.

Each charged particle that has passed through the magnetic field is transferred to the electrodes 6a and 6b.
By being introduced into the electric field generated by
It is further deflected in the direction of the electric field. 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 detected here.

Incidentally, in such a neutral particle mass energy analyzer, the neutral particle beam 2 entering from the entrance port 3 is shaped into a predetermined thickness of the aperture 8 provided on the entrance side of the charge exchange cell 4. . For this reason, particles that could not enter the charge exchange cell 4 are
The stray particles 14 are scattered within the vacuum container 1 .
When such stray particles 14 have relatively low energy, they are exhausted to the outside from the exhaust port 12 as they are, but when their energy is high, they collide with the particle detector 7 during the scattering process, causing false signals. There was a problem in that it caused

Further, such a problem occurs when light enters the vacuum vessel 1 from a neutral particle source (not shown), and this light is reflected by the aperture and scattered, becoming stray light. It also occurs in cases.

For this reason, conventional particle analyzers of this type inevitably have a problem in that there is a lot of noise caused by the stray particles and stray light, resulting in a lack of measurement reliability.

[Purpose of the invention]

The present invention was developed based on the above circumstances, and its purpose is to absorb the energy of stray particles and stray light generated in a vacuum container, and to prevent noise generation due to this, thereby improving reliability. An object of the present invention is to provide a particle analyzer capable of analyzing particle mass or particle energy with high accuracy.

[Summary of the invention]

The present invention provides a system for absorbing the energy of stray particles and stray light around the path of the particle beam from an entrance port, which is an introduction port for the particle beam into the vacuum vessel, to an aperture housed inside the vacuum vessel. It is characterized by the fact that it has a barrier.

〔Effect of the invention〕

According to the present invention, since a barrier is provided around the path of the particle beam from the input port to the aperture, stray particles and stray light that collide with the aperture and are scattered are further prevented from colliding with the barrier. Energy is consumed. Therefore, these stray particles and stray light do not affect the particle detector, and as a result, analysis performance can be improved. Furthermore, since the above-mentioned effects can be obtained by simply adding a simple element such as a barrier, there is no need to complicate the entire system.

[Embodiments of the invention]

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

FIG. 3 shows an embodiment in which the present invention is applied to a neutral particle mass energy analyzer, and the same parts as in FIG. 1 are designated by the same reference numerals. Therefore, a detailed explanation of the overlapping parts will be omitted.

This embodiment differs from conventional analyzers in that a cylindrical body 2 is provided to cover the passage of the neutral particle beam 2 between the entrance port 3 in the vacuum vessel 1 and the charge exchange cell 4.
The reason is that 0 is set. The peripheral wall of the cylindrical body 20 is provided with holes 21 and 22 for exhausting the gas inside the cylindrical body 20 to the outside through the vacuum container 1.
is provided.

With such a configuration, a part of the neutral particles 2 or light that enters the inside of the cylindrical body 20 from the input port 3 is reflected and scattered inside the cylindrical body 20, and the energy thereof is eventually attenuated. do. The neutral particles floating inside the cylindrical body 20 are exhausted to the outside through the vacuum container 1 to the exhaust port 12.

Therefore, stray particles and stray light do not collide with the particle detector 7 in a high-energy state, so that highly reliable neutral particle mass energy analysis can be performed with less noise. Moreover, in this case, the above-mentioned effect can be obtained with only a simple configuration in which the cylindrical body 20 is provided between the entrance port 3 and the charge exchange cell 4, so the overall analyzer does not become complicated. As a result, the above-mentioned effect can be obtained.

Note that the present invention is not limited to the above embodiments. For example, as shown in FIG. 4, without using the cylindrical body 20 as a barrier for stray particles and stray light,
A plurality of annular bodies 25 having a large diameter on the side of the entrance port 3 and a small diameter on the side of the charge exchange cell 4 are provided in the traveling direction of the neutral particle beam 2 so as to surround the passage of the neutral particle beam 2. It's okay.

In this way, the air permeability between the space between the input port 3 and the charge exchange cell 4 and the inside of the vacuum container 1 is high, so that the suspended particles whose energy has been deactivated on the inner surface of the annular body 25 can be efficiently removed. , can be exhausted to the outside of the vacuum container 1.

Further, as shown in FIG. 5, a cylindrical body 30 is provided between the input port 3 and the charge exchange cell 4, and the inside and outside of this cylindrical body 30 are shut off, so that the gas inside the cylindrical body 30 is transferred to the input port. Alternatively, the air may be exhausted from an exhaust port 31 provided at 3.

In this case, approximately half of the gas flowing out from the charge exchange cell 4 can be exhausted through the path from the cylindrical body 30 to the input port 3 to the exhaust port 31, and the vacuum vessel 1
Almost no extra particles are allowed to flow into the interior. Therefore, the pressure near the particle detector 7 can be stabilized, allowing more reliable analysis.

Although the above example is an example in which the present invention is applied to a neutral particle mass energy analyzer equipped with a charge exchange cell 4, the present invention can also be applied to a charged particle mass energy analyzer equipped only with an aperture that also serves as a collimator. can be applied. It goes without saying that the present invention can also be applied to a particle energy analyzer in which only a magnetic field is formed in a vacuum container and a particle mass analyzer in which only an electric field is formed in a vacuum container.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view showing a conventional neutral particle mass energy analyzer, and Figure 2 is a cross-sectional view of the neutral particle mass energy analyzer taken along line A-A in Figure 1 and viewed from the direction of the arrow. 3 is a schematic sectional view showing a neutral particle mass energy analyzer according to one embodiment of the present invention, and FIGS. 4 and 5 are schematic cross-sectional views showing a neutral particle mass energy analyzer according to another embodiment of the present invention FIG. 1 is a cross-sectional view of a particle mass energy analyzer. 1... Vacuum vessel, 2... Neutral particle beam, 3...
...Injection port, 4...Charge exchange cell, 5a, 5b
...Magnetic pole, 6a, 6b... Electrode, 7... Particle detector, 8, 9... Aperture, 11a, 11b...
Coil, 12, 31... Exhaust port, 13... Charged particle beam, 14... Stray particles, 20, 30... Cylindrical body, 25... Annular body, P... Charge exchange gas.

Claims (1)

[Claims] 1. In a particle analyzer in which an aperture is provided between a particle entrance port and a particle deflection field, and the aperture narrows down a particle beam traveling toward the particle deflection field, A particle analyzer, characterized in that a barrier is provided around the path of the particle beam to the aperture. 2. The particle analyzer according to claim 1, wherein the aperture also serves as a wall of a charged particle exchange cell.