JP2789821B2 - Charged particle deflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle deflector for achromatically deflecting charged particles, for example.

[0002]

2. Description of the Related Art FIG. 3 shows, for example, The Review of Scientific
Instruments, vol.34, number4, April1963Achromatic
It is a figure showing the conventional charged particle deflection device shown in Magnetic Mirror for Ion Beams II. FIG. 3 (a) shows the trajectory of the charged particles, and FIG. 3 (b) shows a cross-sectional view, wherein 1 is an S pole, 2 is an N pole, 3 is a yoke supporting S pole 1 and N pole 2, 4 Denotes an entrance and exit from which charged particles enter or exit, and 5 denotes charged particles.

Next, the operation will be described. The charged particles 5 incident on the origin O from the entrance / exit port 4 provided in the yoke 3 at the angle α on the xy plane at the angle α are assumed to have no leakage of the magnetic field from the entrance / exit port 4 on the yz plane. A trajectory as shown in the drawing is drawn on the plane, and the plane returns to the origin O again. Further, even if the charged particles 5 having different velocities enter the origin O at an angle α, they return to the origin O again, for example, draw a trajectory like a broken line, and exit at an angle α. As described above, all the charged particles 5 having different energies are emitted similarly if they enter at an angle α. In this case, when α = 40.71 °, the above phenomenon becomes possible. Such a system is said to be achromatic. Each of the magnetic poles 1 and 2 is obtained by dividing a so-called quadrupole electromagnet into halves, and the magnetic field becomes stronger with a fixed magnetic field distribution with the origin O being 0.

However, since the magnetic field actually leaks to the left (−x direction) from the origin O (broken line in FIG. 3C), the trajectory is as shown by the broken line in FIG. Does not return to the origin O, passes through the shifted position, and is no longer achromatic.

[0005]

Since the conventional charged particle deflecting device is configured as described above, there is a problem that a desired deflection cannot be realized due to the influence of the leakage magnetic field.

The present invention has been made to solve the above problems, and has as its object to obtain a charged particle deflecting device capable of canceling the influence of a stray magnetic field and achieving a desired deflection.

[0007]

SUMMARY OF THE INVENTION A charged particle deflector according to the present invention is a charged particle deflecting device which receives light incident at a predetermined angle from an entrance / exit port.
As the charged particle progresses, the magnetic field applied to the charged particle becomes linear
Having a magnetic field space that becomes stronger, the charged particles are deflected in the magnetic field space.
A charged particle deflector that emits light from the input / output port.
Magnetic field generator for generating a magnetic field for reducing the magnetic field at
It is equipped with a device.

[0008]

The magnetic field generator according to the present invention cancels out the magnetic field leaking from the magnetic space to the external space.

[0009]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. FIG.
Are the same as those of the conventional apparatus, 6 is a two-pole electromagnet, 7 is a magnetic pole of the two-pole electromagnet 6, and 9 is an alpha magnet coil.

Next, the operation will be described. As described in the conventional example, the achromatic property is reduced due to the leakage magnetic field from the entrance and exit of the charged particles. Therefore, as shown in FIG. 1, a dipole electromagnet is installed so that a magnetic field perpendicular to the incident direction of the charged particles acts in a direction opposite to the magnetic field formed by the magnetic poles 1 and 2 so as to cancel the leakage magnetic field.

The leakage magnetic field is large near the magnetic field space at the entrance and exit, and becomes smaller as it approaches the external space. Therefore, the shape of the magnetic pole 7 is inclined as shown in FIG. Makes it possible to more efficiently correct the leakage magnetic field. This not only deforms the shape of the magnetic pole 7 but also enables more accurate correction if the strength of the magnetic field is inclined.

Embodiment 2 FIG. In the above embodiment, the input / output port 4 is provided with a dipole electromagnet. However, a correction coil may be attached as shown in FIG. In the figure, 1 to 3 are the same as the conventional device,
Reference numeral 8 denotes a correction coil. In this case, the leakage coil can be canceled out by winding the correction coil 8 as shown in the figure and making it large near the magnetic field space of the entrance / exit opening 4 and becoming smaller as it goes closer to the outside space. 2 above
In one embodiment, the intensity of the magnetic field generated in the entrance / emission port 4 is shown as being inclined. However, the present invention is not limited to this, and any device that cancels the leakage magnetic field may be used.

[0013]

As described above, the charged particle deflecting device according to the present invention can be applied to a charged particle deflecting device which is incident at a predetermined angle from an entrance / exit port.
As the charged particle progresses, the magnetic field applied to the charged particle becomes linear
Having a magnetic field space that becomes stronger, the charged particles are deflected in the magnetic field space.
A charged particle deflector that emits light from the input / output port.
Magnetic field generator for generating a magnetic field for reducing the magnetic field at
It is equipped with a device to prevent leakage of the magnetic field from the entrance and exit.
Charged particles incident on this charged particle device are
It can be chromatically deflected.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a charged particle deflector according to one embodiment of the present invention.

FIG. 2 is a sectional view showing a charged particle deflector according to another embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a conventional charged particle deflection device.

FIG. 4 is an explanatory diagram showing a trajectory of a charged particle in a conventional charged particle deflection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 S pole 2 N pole 3 Yoke 4 Input / output port 5 Charged particle 6 2-pole electromagnet 7 Magnetic pole 8 Correction coil 9 Alpha magnet coil

Claims (1)

(57) [Claims] 1. A load incident at a predetermined angle from an entrance / exit port.
As the charged particle progresses, the magnetic field applied to the charged particle becomes linear
The magnetic field space that becomes stronger in the
Deflection of charged particles that deflect particles and exit from the entrance
In the apparatus, the charged particle deflection apparatus characterized by comprising a magnetic field generator for generating a magnetic field to the magnetic field at the upper entry exit port to 0.