JP2918554B2 - Electric field type separator for charged particle beam - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam application device, and more particularly to an electric and magnetic field generator suitable for energy separation and mass separation.

[Conventional technology]

Electric field (E) for energy separation and mass separation of charged particle beam
A so-called ExB type separator in which the magnetic field (B) is orthogonal to the magnetic field (B) is used. In order to increase the sensitivity of the ExB type separator, the distribution of E and B needs to be as similar as possible to the traveling direction of the charged particle beam.

As shown in FIG. 3 (a), a conventional ExB type separator has an electrode 2 for generating an electric field and a coil 3 for generating a magnetic field inside a vacuum.
And its magnetic pole 7 were placed outside the vacuum [Journal
Of Bakium Science Technology, B3 , pp. 50-53 (J. Vac. Sci. Technol., B3 (1985) pp. 50-5
3)] In such a configuration, since the magnetic pole interval is larger than the electrode interval, there is a disadvantage that the distribution of B and the distribution of E cannot be made similar as shown in FIG. 3 (b).

The ExB type separator is also disclosed in Japanese Patent Application Laid-Open No. 60-47358.

[Problems to be solved by the invention]

The problem to be solved by the present invention is to configure electrodes and coils so that the distributions of E and B are as similar as possible. This is for the following reason.

The E and B of the ExB type separator are applied perpendicularly to the traveling direction of the charged particle beam so that E / 2V = (e / 2mV) ^1/2 B (1) is always satisfied. There is a need. Here, V: acceleration voltage, e / m: charge / mass. In this case, a charged particle beam having desired energy and mass always passes on the optical axis. This is the most significant feature of the ExB type separator. When this condition is broken, the charged particle beam passes through a place farther from the optical axis and receives higher-order aberrations, which causes a reduction in separation sensitivity. Therefore, (1)
The equation, ie, the distribution of E and B, must be as similar as possible.

[Means for solving the problem]

In order to make the distributions of E and B as similar as possible, it is easiest to make them as uniform as possible. For this purpose, the electrode for generating an electric field may have a sufficiently longer electrode length than between the electrodes, and the coil for generating a magnetic field may have a sufficiently longer coil length than the coil diameter. By doing so, the portion of the uniform distribution becomes longer, and naturally becomes closer to a similar shape. Even in this case, a non-uniform portion called a fringing field occurs on the end face of the electrode or the coil, and it is difficult to make a similar shape up to this portion as it is. Although this part is essentially unavoidable, the effect can be reduced if the fringing field is made as small as possible by using electrodes and magnetic poles for shielding electric and magnetic fields.

 The present invention has been made based on the above idea.

[Action]

It is needless to say that if the electrode length is sufficiently longer than the distance between the electrodes or the coil length is sufficiently longer than the coil diameter, the uniform portion of the electric and magnetic field distribution becomes longer. On the other hand, if the entire ExB separator is shielded with a conductive magnetic material and only a hole is made in the portion where the charged particle beam passes, the electric and magnetic fields are bound inside this shield member by this shielding effect. Fringing field is reduced. In particular, if the shield member is made of a conductive magnetic material, the shielding effects of the electric field and the magnetic field become equal, and the fringing field tends to be similar to the similar shape.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 (a) is a cross-sectional view of the entire configuration, and FIG. 1 (b) is an external view in which the coil portion is easily seen. Cylindrical insulator 1
The electrode 2 is formed inside (for example, ceramics), and the coil 3 is formed close to the outside. A voltage is applied to the electrode 2, an electric field E is applied, and a current is applied to the coil 3 to generate a magnetic field B, thereby forming an ExB type separator. In order to shield the electric field and the magnetic field, the cylindrical insulator is surrounded by a conductive member 4 made of a magnetic material. Of course, this member has a hole 5 so that a charged particle beam can pass through. By this shielding member, an electric field or a magnetic field is confined in the inside, and more uniformity can be obtained.

For example, the inner diameter of the cylindrical insulator 1 is r, the outer diameter is R, and the length is
L, when the hole diameter of the shielding member 4 is d, R / r ≦ 1.5, L
When / r ≧ 5 and d / r ≦ 0.5, a uniform electric or magnetic field can be formed with a length of 0.8 L or more. As shown in FIG. 1 (c), E and B are almost similar in shape. become.

FIG. 2 is a sectional view showing another embodiment. The outside of the cylindrical insulator 1 and the inside of the shield member 4 are spheroidal. With such a shape, the fringing field can be made extremely small, and almost uniform distribution can be obtained. In this case, what is important is to make the inside of the shielding member 4 spheroidal, and the outer shape of the cylindrical insulator 1 is made to facilitate the formation of the coil 3 (omitted in FIG. 2). It is not an essential problem.

Although some examples have been described above, the point of the present invention is,
In order to make the electrode diameter and the coil diameter as equal as possible, an electrode for generating an electric field is formed inside a thin-walled cylindrical insulator, and a coil for generating a magnetic field is formed outside of the thin cylindrical insulator. In this case, this effect naturally occurs. In addition, by using a member for shielding electric and magnetic fields,
This effect is enhanced. Therefore, the present invention is not limited to this embodiment as long as it has such a configuration.

[Effects of the Invention] As described above, according to the present invention, a uniform electric field and magnetic field can be obtained as compared with the conventional method, and the distribution becomes similar, so that the energy separation and the mass separation of the charged particle beam can be improved. There is an effect that can be performed on performance. In addition, since it is possible to reduce the size, not only can everything be arranged in a vacuum, but also there is an effect that a large separation sensitivity can be obtained with low power.

[Brief description of the drawings]

FIG. 1 (a) is a perspective view including a vertical cross section of an ExB separator showing one embodiment of the present invention, FIG. 1 (b) is an external view of an excluding a shielding electromagnetic pole, and FIG. 1 (c). FIG. 2 is a distribution diagram of the electric and magnetic fields, FIG. 2 is a perspective view including a longitudinal section of an ExB separator having a spheroidal inside of a shield member according to another embodiment of the present invention, and FIG. FIG. 3A is a perspective view including a longitudinal section of the ExB filter, and FIG. 3B is a distribution diagram of an electric field and a magnetic field. 1 ... cylindrical insulator, 2 ... electrode, 3 ... coil, 4 ...
... conductive magnetic material for shielding, 5 ... hole for passing charged particle beam, 6 ... pipe for vacuum, 7 ... magnetic pole.

Claims (5)

(57) [Claims] An electric field magnetic field separator for a charged particle beam in which an electric field and a magnetic field are made to act on a charged particle beam in a direction perpendicular to each other, wherein a coil for generating the magnetic field and an electrode for generating the electric field are provided. An electric field type separator for a charged particle beam, comprising a shield member made of a conductive magnetic material having an opening for allowing the charged particle beam to pass therethrough. 2. A charged particle beam electric field magnetic field type separator for causing an electric field and a magnetic field to act on a charged particle beam at right angles, wherein a coil for generating the magnetic field and an electrode for generating the electric field are provided. A shield member made of a conductive magnetic material having an opening for passing the charged particle beam is provided on an outer periphery of the coil and the electrode and provided on an insulating member having a space for passing the charged particle beam. An electric field type separator for a charged particle beam, comprising: 3. An electrode for generating an electric field, a coil for generating a magnetic field, and an insulating member having a space for passing a charged particle beam, wherein the electrode is provided inside the insulating member. , The coil is integrally formed on the outside, and a shielding member made of a conductive magnetic material having an opening for passing the charged particle beam is provided on the outer periphery of the coil. Characteristic electric field type separator for charged particle beam. 4. The electric field type separator for a charged particle beam according to claim 2, wherein the insulating member is a thin cylindrical insulating member. 5. An apparatus for applying a charged particle beam, comprising the electric field magnetic field separator for a charged particle beam according to claim 1.