JPH01232700A - Electromagnet for charged particle device - Google Patents

Abstract

PURPOSE:To prevent effects of the past excitation history at a low cost by providing a detachable magnetic body for bypassing magnetic flux in a gap forming a magnetic circuit in series with an electromagnet iron core so as to eliminate a remaining magnetic field in the gap to zero. CONSTITUTION:A magnetic body 4 is provided in a gap of an electromagnet consisting of an iron core 2 having an excitation coil 3 applied for bypassing a magnetic flux. By detaching the magnetic body 4 while excitation of the electromagnet, a need of deflecting charged particles is eliminated, and if an exciting power source for the electromagnet is disconnected, a remaining magnetic field is produced by hysteresis phenomenon of the iron core 2. By inserting the magnetic body 4 into the gap then, remaining magnetic flux passes the magnetic body 4 to eliminate the remaining magnetic field in the gap to zero. Effects of hysteresis phenomenon of the iron core can thus be eliminated at a low cost without providing a power source for demagnetizing separately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electromagnet for a particle transport device, and more particularly to an electromagnet for a particle transport device that is provided with means for demagnetizing the electromagnet.

[Conventional technology]

Figure 6 shows, for example, "Physical Experiments (Sixth Edition)" published by Sanseido,
(November 25, 1982) This is a case where the demagnetization method shown on page 254 is applied to an electromagnet, and in the figure (1
) is the demagnetizing power supply, and (2) is the iron core of the electromagnet, forming an S air circuit in series with the gap. (3) is an excitation coil.

With the above configuration, an alternating current is applied to the excitation coil (3) by the demagnetizing power supply (1). The amplitude at this time is gradually attenuated from a value larger than the maximum value used, as shown in Figure 7 (1), until it reaches a final level. This makes the magnetic field zero.

[The problem that the invention aims to solve]

In conventional electromagnets for particle transporting devices such as those described above, the power supply equipment for supplying an alternating current with a considerably large period is required to demagnetize the electromagnet and eliminate the influence of eddy current flowing through the iron core. It is necessary separately. Furthermore, such power supply equipment is not only quite large-scale but also difficult to control at high speed, making it not very practical for medical charged particle devices and the like.

If the demagnetization of the electromagnet is incomplete, the trajectory of the charged particles will be deflected by the residual magnetic field in the magnet gap even though the electromagnet is not excited, and the charged particles will not move on the intended trajectory. Another problem was that the deflection angle of the orbit depended on the past excitation history due to the hysteresis phenomenon of the electromagnet core.

This invention was made in order to solve the above-mentioned problems, and is a charged particle device that makes it possible to eliminate the influence of the hysteresis phenomenon of the iron core by reducing the residual magnetic field in the electromagnet gap to zero without using a demagnetizing power source. The purpose is to obtain an electromagnet for use.

[Means to solve the problem]

The electromagnet for a charged particle device according to the present invention includes a removable magnetic body that bypasses magnetic flux in a gap forming a magnetic circuit in series with the electromagnet core.

[For production]

In this invention, the magnetic flux passing through the gap of the electromagnet passes through the inside of the magnetic flux bypassing magnetic body attached to the gap portion, thereby reducing the residual magnetic field in the gap to zero.

〔Example〕

FIG. 1 shows a first embodiment of the invention, in which a removable magnetic body (4) bypasses the magnetic flux in the gap of the electromagnet.
is provided.

In addition, the same reference numerals as in FIG. 6 indicate the same parts.

With the above configuration, the magnetic body (4) that bypasses the magnetic flux in the gap is removed while the electromagnet is excited. Next, there is no need to deflect the charged particles, and the excitation power to the electromagnet is turned off. In this case, a residual magnetic field is generated in the gap due to the hysteresis phenomenon of the electromagnet core (2). here,
If the magnetic body (4) is inserted into the gap and the magnetic flux in the gap is made to pass through the magnetic body (4), the magnetic flux passing through the gap disappears and the residual magnetic field in the gap becomes zero.

FIG. 2 shows a second embodiment, in which a linear magnetic body (4) is attached to the side of the gap, and the same effect is obtained.

FIG. 3 shows a third embodiment, in which a U-shaped magnetic body (4) is attached to the side of the gap, and the same effect is achieved.

FIG. 4 shows a fourth embodiment, in which a pair of U-shaped magnetic bodies (
4) are installed in the gap facing each other and have the same effect.

The above has been explained using a two-pole electromagnet as an example, but as a fifth embodiment, as shown in FIG. Similar effects can be obtained by doing this. The same applies to multipole electromagnets with four or more poles.

〔Effect of the invention〕

As described above, according to the present invention, the residual magnetic field in the gap becomes zero by allowing the magnetic flux to pass through the magnetic material that bypasses the magnetic flux in the gap of the electromagnet without using a demagnetizing power source. As a result, the device can be made at low cost, and the past excitation of electromagnets is possible! It has the effect of not being affected by ¥ history.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of the main part of the first embodiment of this invention, and the second
4 to 4 are side sectional views of the main parts of the second to fourth embodiments, respectively, FIG. 5 is a side sectional view of the fifth embodiment, and FIG. 6 is a side sectional view of the main parts of a conventional charged particle device. 7 are current waveform diagrams for explaining the operation of the device shown in FIG. 6. (2)...Electromagnetic core, (3)...Exciting coil, (4)
... S-type body. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] An electromagnet for a charged particle device, which is detachably equipped with a magnetic body that bypasses the magnetic flux in the electromagnet gap, zeroes out the residual magnetic field in the electromagnet gap, and eliminates the influence of a hysteresis phenomenon in an iron core.