JPH0534773B2 - - 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 of charged particles or neutral particles using an electric field.

[Technical background of the invention]

Conventionally, particle analyzers analyze the mass or energy of charged particles or neutral particles by injecting a particle beam into an electric or magnetic field and detecting the amount of deflection of each particle. There are known devices that measure . Such a particle analyzer, for example, a neutral particle mass energy analyzer for analyzing the mass and energy of neutral particles such as H and D, is constructed as shown in FIGS. 1 and 2.

That is, in the figure, 1 is a vacuum container,
An input port 3, which is an input port for the neutral particle beam 2, is provided on the side wall of the vacuum container 1. Inside the vacuum container 1, there are a charge exchange cell 4, magnetic poles 5a, 5b, and electrodes 6 corresponding to the orbits of the neutral particles.
a, 6b, and a particle detector 7 are housed therein. 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
Rectangular magnetic pole face 10 whose length is the vertical direction in the figure
By energizing the coils 11a and 11b, which are arranged to face each other with a predetermined gap between them and are wound around the base ends of the magnetic poles 5a and 5b, a magnetic field in a direction perpendicular to the plane of the paper in FIG. 1 is generated. generate. Further, the electrodes 6a, 6b are made of trapezoidal plates whose width increases from the top to the bottom in FIG.
They are arranged parallel to and opposite to the magnetic pole faces 10a and 10b with an interval wider than a predetermined interval between them. One electrode 6a is grounded via the conductive member 12 and the vacuum container 1, and is maintained 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, 15 in the figure is
This 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 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 16. At this time, charged particle beam 1
The beam 6 is shaped into a parallel beam having a predetermined thickness and shape by collimators 8 and 9 provided at both ends of the charge exchange cell 4 and also serving 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.

[Problems with background technology]

By the way, in this type of particle analyzer, as mentioned above, one of the electrodes 6a and 6b is grounded via the vacuum container 1, and the other electrode 6b is kept at a lower potential than the electrode 6a. A potential difference is provided between the two electrodes 6a and 6b to form an electric field for mass spectrometry. Therefore, both the electrodes 6
The potential of the charged particle entrance portion R between a and 6b is lower than the ground potential.

Therefore, when the charged particles are introduced into the electric field region, the charged particles are accelerated by the potential of the entrance portion R, resulting in a measurement error. These problems become more pronounced as the energy of the particles decreases, and as a result, mass spectrometry of low-energy particles is particularly unreliable.

[Purpose of the invention]

The present invention has been made based on the above-mentioned problems, and its purpose is to suppress the influence of the electric field on the particles to be analyzed while reaching the electric field for mass spectrometry, and to It is an object of the present invention to provide a particle analyzer that can perform highly reliable analysis regardless of the level of particle energy.

[Summary of the invention]

The present invention is characterized in that the potential of the particle beam entrance part in the electric field for particle beam analysis formed inside the vacuum vessel is made to be the same potential as the vacuum vessel potential.

〔Effect of the invention〕

According to the present invention, the potential at the particle entrance position in the electric field for mass spectrometry is made equal to the potential of the vacuum container, so that a potential difference is created between the particle entrance part of the electric field and the inner surface of the vacuum container. It never occurs. Therefore, the particles are not accelerated until they are introduced into the electric field, and as a result,
The effect is that highly reliable analysis can be performed regardless of the level of particle energy.

[Embodiments of the invention]

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

3 and 4 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.

This embodiment differs from the conventional example described above in the electrical connection relationship between the electrodes 6a, 6b and the vacuum vessel 1. That is, the electrodes 6a, 6 according to this embodiment
b are both fixed to the vacuum container 1 via insulating members 21 and 22. The vacuum container 1 is grounded, a power source 23 is connected between the vacuum container 1 and the electrode 6a, and a power source 24 is connected between the vacuum container 1 and the electrode 6b. As a result, the electrode 6a is held at a potential higher than the ground potential, and the electrode 6b is held at a potential lower than the ground potential. Then, the voltage of each power source 23, 24 is set to a value corresponding to the distance between the charged particle entrance part R and each electrode 6a, 6b, and thereby the potential of the charged particle entrance part R becomes approximately ground potential. are set to be equal. Therefore, the charged particle entrance portion R and the vacuum container 1 are at approximately the same potential.

With such a configuration, no potential difference is generated between the charged particle entrance portion R and the inner surface of the vacuum container 1, so that the charged particles are not accelerated in the charged particle entrance portion R. Therefore, the speed of a charged particle passing through an electric field is determined by the kinetic energy inherent in the charged particle, allowing accurate mass-energy analysis.

The above embodiment is an example in which the present invention is applied to an energy analysis magnetic field and a mass analysis electric field formed in different regions, but for example, as shown in FIGS. 5 and 6, , magnetic pole 31
Insulating members 32, 33 are provided on each opposing surface of a, 31b.
Even in a particle analyzer in which an electric field region and a magnetic field region are formed between the electrodes 34a and 34b via the
It is possible to apply the present invention.

In this case as well, similarly to the above, the vacuum container 1 is grounded, and the power source 35 is connected between the vacuum container 1 and the electrode 34a, and the power source 36 is connected between the vacuum container 1 and the electrode 34b. . Then, the polarity of each power source is matched so that the electrode 34a has a positive potential and the electrode 34b has a negative potential, and the particle entrance portion R
By setting the voltages of the power supplies 35 and 36 in accordance with the distance between the electrodes 34a and 34b, and thereby making the potential of the particle entrance part R equal to the level of the vacuum vessel 1, The same effect as in the example can be achieved.

Although the present invention has been mainly applied to a mass energy analyzer for neutral particles, it can also be applied to a charged particle analyzer by simply replacing the charge exchange cell 4 with a collimator. It goes without saying that the present invention can also be applied to a particle mass spectrometer in which only an electric field region is provided within a vacuum container.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing a conventional neutral particle mass energy analyzer, and FIG. 2 is a view of the same device cut along the line A-A in FIG. 1 and viewed in the direction of the arrow.
FIG. 3 is a cross-sectional view schematically showing a neutral particle mass energy analyzer according to an embodiment of the present invention, and FIG. 4 is a cross-sectional view of the neutral particle mass energy analyzer according to an embodiment of the present invention. FIG. 5 is a cross-sectional view schematically showing a neutral particle mass energy analyzer according to another embodiment of the present invention, and FIG. 6 is a cross-sectional view of the neutral particle mass energy analyzer according to another embodiment of the present invention. It is a cutaway view seen in the direction of the arrow. 1... Vacuum vessel, 2... Neutral particle beam, 3...
...Injection port, 4...Charge exchange cell, 5a, 5
b, 31a, 31b...magnetic pole, 6a, 6b, 34
a, 34b...electrode, 7...particle detector, 8,9
...Collimator, 10a, 10b...Magnetic pole surface, 1
1a, 11b... Coil, 12... Conductive member,
13, 21, 22, 32, 33...Insulating member, 1
4, 23, 24, 35, 36...power supply, 15...
Exhaust port, 16...Charged particle beam, P...Charge exchange gas, R...Particle incidence part.

Claims (1)

[Claims] 1. An electric field is formed between a pair of electrodes placed opposite each other inside a vacuum container, and the particle beam to be analyzed is deflected by the electric field. By detecting the amount of deflection, the mass of each particle constituting the beam can be determined. In a particle analyzer adapted for analysis, means for holding the pair of electrodes in an insulated state with respect to the vacuum container, and a position midway between the pair of electrodes held by this means. and means for forming an analytical electric field equal to the level of the vacuum vessel.