JPH04262298A - Charged particle deflection device - Google Patents

Abstract

PURPOSE:To realize desired deflection by providing a magnetic field generator to generate a magnetic field for canceling the leakage magnetic field out of the magnetic space, at the inlet and outlet where charged particles come in and go out. CONSTITUTION:As achromatism lowers due to the leak magnetic field out of the inlet and outlet of charged particles, two polar magnets 6 are placed in the opposite direction to the magnetic field formed by magnetic poles 1, 2 to cancel the leakage magnetic field and to work the magnetic field perpendicularly to the incidence direction of the charged particles. Thus by inclining the shape of a magnetic pole 7 and strengthening the magnetic field more near the magnetic field space, the leakage magnetic field is corrected more efficiently. If the magnitude of the magnetic field is inclined, more accurate correction is possible. Therefore, the effect of leakage magnetic field is eliminated to attain desired deflection.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art FIG. 3 shows, for example, The Review o
f Scientific Instruments,
vol. 34, number 4, April 1963
■Achromatic Magnetic Mirror
1 is a diagram showing a conventional charged particle deflection device shown in "or for Ion Beams". FIG. 3(a) shows the trajectory of the charged particles, and FIG. 3(b) shows a cross-sectional view. In the figure, 1 is the S pole, 2 is the N pole, 3 is the yoke that supports the S pole 1 and the N pole 2,
Reference numeral 4 indicates an input/output port through which charged particles enter or exit, and 5 indicates a charged particle.

Next, the operation will be explained. Assuming that there is no leakage of the magnetic field from the entrance/exit port 4 on the y-z plane, the charged particle 5 that enters the origin O from the entrance/exit port 4 provided in the yoke 3 at an angle α on the x-y plane It returns to the origin O again by drawing a trajectory on the plane as shown in the figure. Furthermore, even if the charged particles 5 having different velocities are incident on the origin O at an angle α, they return to the origin O again, drawing a trajectory as indicated by a broken line, for example, and are emitted at an angle α. If the charged particles 5 having different energies are incident at an angle α, they will all be emitted in the same way. In this case, when α=40.71°, the above phenomenon becomes possible. Such a system is called achromatic. The magnetic poles 1 and 2 are generally called quadrupole electromagnets divided in half, and the magnetic field becomes stronger with a constant magnetic field envelope with the origin O as 0.

However, in reality, the magnetic field is on the left side from the origin O (
-x direction) (dashed line in Figure 3(c)), the charged particle 5 does not return to the origin O, but passes through the shifted position, and is achromatic. It will no longer be.

[0005]

Since the conventional charged particle deflection device is constructed as described above, there is a problem in that desired deflection cannot be achieved due to the influence of leakage magnetic fields.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a charged particle deflection device that can cancel out the influence of leakage magnetic fields and realize desired deflection.

[0007]

[Means for Solving the Problems] A charged particle deflection device according to the present invention is provided with a magnetic field generating device that generates a magnetic field that cancels a leakage magnetic field from a magnetic space at an entrance/exit port through which charged particles enter or exit. It is something.

[0008]

[Operation] The magnetic field generator according to the present invention cancels the magnetic field leaking from the magnetic space to the outside space.

[0009]

[Example] Example 1. An embodiment of the present invention will be described below with reference to the drawings. Figure 1
1 to 3 are the same as the conventional device, 6 is a dipole electromagnet, 7 is a magnetic pole of the dipole electromagnet 6, and 9 is an alpha magnet coil.

Next, the operation will be explained. As explained in the conventional example, the achromaticity is degraded due to the leakage magnetic field from the entrance/exit port of charged particles. Therefore, in order to cancel out this leakage magnetic field, a two-pole electromagnet is installed, as shown in FIG. 1, so that a magnetic field acts in the direction opposite to the magnetic field formed by the magnetic poles 1 and 2 and perpendicular to the direction of incidence of the charged particles.

Furthermore, since the leakage magnetic field is large near the magnetic field space of the entrance/exit port and becomes smaller as it approaches the outside space, the shape of the magnetic pole 7 is tilted as shown in FIG. By making it stronger, the leakage magnetic field can be corrected more efficiently. This not only changes the shape of the magnetic pole 7, but also enables more accurate correction if the strength of the magnetic field is inclined.

Example 2. In the above embodiment, the entrance/exit port 4 is equipped with a bipolar electromagnet, but a correction coil may be attached as shown in FIG. In the figure, 1 to 3 are the same as the conventional device,
8 is a correction coil. In this case, the leakage magnetic field can be canceled by winding the correction coil 8 as shown in the figure so that it is large near the magnetic field space of the entrance/exit port 4 and becomes smaller as it approaches the outside space. Above 2
In the two embodiments, the strength of the magnetic field generated at the entrance/exit port 4 is inclined, but the present invention is not limited to this, and any magnetic field that cancels the leakage magnetic field may be used.

[0013]

As described above, according to the present invention, a magnetic field generator is provided at the entrance/exit port through which charged particles enter or exit, which generates a magnetic field that cancels the leakage magnetic field from the magnetic space. The desired deflection can be achieved by eliminating the influence of

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a charged particle deflection device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a charged particle deflection device showing 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 trajectories of charged particles in a conventional charged particle deflection device.

[Explanation of symbols]

1 S pole 2 N pole 3 York 4 Input/output port 5 Charged particles 6　Dipolar electromagnet 7 Magnetic pole 8 Correction coil 9 Alpha magnet coil

Claims (1)

[Claims] Claims: 1. A magnetic space for deflecting charged particles, and a magnetic field for canceling leakage magnetic fields from the magnetic space at an entrance/exit port provided between the magnetic space and an external space, through which the charged particles enter or exit. A charged particle deflection device comprising a magnetic field generator for generating a magnetic field.