JPH07169596A - Accelerating tube having permanent magnet - Google Patents

Abstract

PURPOSE:To facilitate changeover between the conditions os presence and absence of a magnetic field to an in an accelerating tube. CONSTITUTION:Magnetic poles 22 and 22' are arranged opposite to each other around an accelerating tube, and two first circular arc-shaped permanent magnets 30 and 30' are symmetrically arranged to the central axis of these magnetic poles. These magnets are composed of permanent magnets 26 to 29 magnetized in illustrated polarity, magnetic pole and yoke members 21 and 21' and yoke parts 23 and 23'. Two second circular arc-shaped permanent magnets 31 and 31' are rotatably arranged around the magnetic poles 22 and 22' and the first circular arc-shaped permanent magnets 30 and 30', and these magnets 31 and 31' are installed on a return yoke 32, and the surfaces on the magnetic pole side and the return yoke side are magnetized in illustrated polarity. When the second permanent magnets 31 and 31' are situated in an illustrated position, magnetic fluxes of the respective permanent magnets pass through the inside of the accelerating tube, and after they rotate the second permanent magnets by 180 deg., all magnetic fluxes of the respective permanent magnets pass through the return yoke 32, and do not pass through the accelerating tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accelerating tube for accelerating ions and electrons, and when a magnetic field acting to suppress electron loading in the accelerating tube during ion acceleration accelerates electrons, The present invention relates to an accelerating tube with a permanent magnet that does not act on.

[0002]

2. Description of the Related Art In a megavoltage (MV) class high voltage accelerating tube, an ion beam deflecting portion due to a magnetic field is provided at a required portion of the accelerating tube in order to prevent electron loading. For example, as shown in FIG. 3, 3M with about 70 acceleration stages
In the case of the class V accelerating tube 1, the magnet devices 2, 3, 4 serving as magnetic field sources are provided at the accelerating stages around the 50th stage, the 30th stage, the 20th stage, and the 10th stage, counting from the ground side. 5 is attached.

FIG. 4 shows the most ion beam in the acceleration tube 1.
FIG. 6 is a cross-sectional view of an accelerating tube portion to which a magnet device 2 located on the introduction side of the magnet is attached. The permanent magnets 8, 9, 10, 11, 12, 13 are attached by using a binding band 14 made of an insulator, and both ends of each permanent magnet are magnetized to the polarities shown in the figure. A yoke iron piece 15 is inserted between the permanent magnets 8 and 9, 9 and 10, 11 and 12, 12 and 13 to reduce the magnetic resistance of the magnetic circuit, and the magnets 8 and 11 and the magnet 1 are provided.
An iron piece 16 that also functions as a magnetic pole is provided between 0 and 13, and magnetic force lines are generated from the facing N pole portions of the permanent magnets 10 and 13 toward the facing S pole portions of the magnets 8 and 11. A magnetic field H is formed in the beam path in the acceleration tube from the bottom to the top. Therefore, when the positive ion beam travels from the front to the back of the figure, the magnetic field deflects the beam to the right.

The magnet devices 3, 4 and 5 are arranged in a state in which the magnet device 2 is rotated by exactly 180 °, and the positive ion beam is deflected to the left side opposite to the magnet device 2. Therefore, the positive ion beam introduced into the accelerating tube 1 is largely deflected by the magnetic field of the magnet device 2 in a state where it is not sufficiently accelerated, and is gradually corrected to a regular trajectory by the magnetic field of the magnet devices 3 to 5. is doing.

[0005]

In some cases, the accelerating tube of the ion accelerator is used as an electron beam accelerating means, and when the frequency of electron acceleration is low, it is not necessary to provide a separate ion accelerator and electron accelerator. It has been used since. The ion accelerator may be either a single stage accelerator or a tandem accelerator.For example, in the case of a tandem accelerator, an electron generation source is arranged at the entrance of the high energy side accelerating tube for accelerating the positive ion beam, and the acceleration voltage is also increased. The electron beam is accelerated by switching the polarity of.

However, in this case, as shown in FIGS. 3 and 4, if the magnet devices 2 to 5 for suppressing electron loading are attached to the accelerating tube 1, the accelerating tube is left as it is for the electron beam. It cannot be used as an accelerator. The magnetic flux density acting on the accelerating tube by the magnet devices 2 to 5 is about 20 to 100 gauss, but due to the marked difference in the mass of ions and electrons, the electron beam is significantly deflected even in the presence of a magnetic field of about several gauss. The acceleration tube is useless for electron acceleration.

Therefore, when a positive ion beam accelerating tube is used as an electron accelerating tube, a pressure tank accommodating the accelerating tube is opened, and a hoop for preventing discharge is arranged around the accelerating tube. Temporarily dismantle the insulating column parts, etc. so that work can be performed around the accelerating tube.
Nos. 5 to 5 must be removed, and the magnet device must be reattached when the ions are accelerated again. Usually, the removal and mounting work of such a magnet device took three people and took one day.

An object of the present invention is to provide an accelerating tube with a permanent magnet that can change the presence or absence of a magnetic field by a permanent magnet acting on the accelerating tube in an extremely short time.

[0009]

An accelerating tube with a permanent magnet according to the present invention is provided around the accelerating tube symmetrically with respect to a central axis line between opposing magnetic poles, and each magnetic pole side end is magnetized. Two first arc-shaped permanent magnets, an annular return yoke that surrounds the first arc-shaped permanent magnets, and an inner side of the return yoke. Two second arc-shaped permanent magnets rotatably provided around each of the permanent magnets, each permanent magnet having a magnetic pole surface on which the return yoke side and the first arc-shaped permanent magnet side are magnetized. The magnetic pole surface of the permanent magnet is characterized by comprising second arc-shaped permanent magnets which are magnetized in opposite polarities.

[0010]

The two second rotatable arc-shaped permanent magnets are arranged at the first position where the polarities of the magnetic pole surfaces of the first circular arc-shaped permanent magnet match the polarities of the ends of the first circular arc-shaped permanent magnet. By moving, the magnetic flux of the first and second arc-shaped permanent magnets passes through the acceleration tube. Further, the two second arc-shaped permanent magnets are rotated by 180 ° from the first position, and the polarities of the magnetic pole surfaces on the first arc-shaped permanent magnet side are opposite to the polarities of the ends of the first arc-shaped permanent magnet. When moved to the second position, all the magnetic fluxes of the first and second arc-shaped permanent magnets pass through the return yoke, and no magnetic field is generated in the acceleration tube.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of the magnet device portion, and the same reference numerals as those in FIGS. 3 and 4 denote the same parts. Two magnetic pole and yoke members 21 and 21 'are provided around the insulating ring 7 in the acceleration tube. Each of the magnetic pole / yoke members is formed with a magnet arranging portion 25, 25 ', leaving a magnetic pole 22, 22', a yoke portion 23, 23 'and a coupling portion 24, 24' made of a thin nonmagnetic material. , Arc-shaped permanent magnets 26, 27, 28, 29 each end of which is magnetized in the illustrated polarity are arranged and fixed in each magnet arrangement portion. By arranging the arc-shaped permanent magnets in this way, the magnetic poles 22, 2 facing each other are provided around the acceleration tube.
With respect to the central axis line between 2 ', the arc-shaped permanent magnets 26 and 27,
The magnets 28 and 29 and the yoke portions 23 and 23 'are symmetrically provided to form the two first arc-shaped permanent magnets 30 and 30' whose end portions on the magnetic pole side are magnetized.

These two first arc-shaped permanent magnets 30, 3
0'and the magnetic poles 22 and 22 ', that is, two second arc-shaped permanent magnets that are rotatable around the magnetic pole / yoke members 21 and 21' in which permanent magnets are provided in the magnet arrangement portions 25 and 25 '. The magnets 31 and 31 'are provided so as to face each other,
These magnets are fixed inside the annular return yoke 32. Each of the magnets 31 and 31 'has a magnetic pole surface whose surfaces on the return yoke side and the first arc-shaped permanent magnet side are magnetized in the polarities shown in the figure. The magnetic pole surfaces of the two permanent magnets are magnetized in opposite polarities. It is magnetized.

Such a magnet device corresponds to, for example, the magnet devices 3 to 5 in FIG. 3, and the magnet device in FIG. 1 rotated by 180 ° corresponds to the magnet device 2 in FIGS. 3 and 4. To do.

When accelerating a positive ion beam with an accelerating tube,
By rotating the two second arc-shaped permanent magnets 31 and 31 ′ together with the return yoke 32, these magnets are at the positions shown in FIG. 1, and the polarities of the inner magnetic pole surfaces on the side of the first arc-shaped permanent magnets 30 and 30 ′ are At the first position that matches the polarity of the ends of the first arc-shaped permanent magnets 30 and 30 ', as shown in FIG. 2A, the magnetic flux of the first and second arc-shaped permanent magnets is the magnetic pole 22. , 2
Pass through the acceleration tube between 2 '. That is, the first arc-shaped permanent magnet 3
Permanent magnets 26 and 27, and 28 and 29 at 0 and 30 '
Magnetic flux is generated between the magnetic poles 22 and 22 'and the yoke portions 23 and 23'.
The magnetic flux of the second arc-shaped permanent magnets 31, 31 'passes through the magnetic poles 22, 22' and the return yoke 32. Therefore, a magnetic field of 20 to 100 gauss that deflects the positive ion beam is generated in the accelerating tube for suppressing electron loading.

When the accelerating tube is used for accelerating electrons, the second arc-shaped permanent magnets 31, 31 'are placed 180 degrees from the first position in the figure.
It is rotated to move to a second position where the polarity of the magnetic pole surface on the side of the first arc-shaped permanent magnets 30 and 30 'is opposite to the polarity of the end portion of the first arc-shaped permanent magnet. As shown in FIG. 2B, all the magnetic fluxes of the first and second arc-shaped permanent magnets pass through these magnets and the return yoke 32, and no magnetic field is generated in the acceleration tube.

The arc lengths of the yoke portions 23, 23 'provided on the magnetic pole / yoke members 21, 21' in the above-described embodiment should be shortened according to the lengths of the arc-shaped permanent magnets 26-29. The same magnets 26, 27, and 28
Each of 29 and 29, including the yoke portion, may be composed of one magnet. Further, the magnetic pole / yoke members 21 and 21 'may be integrally formed.

[0017]

Since the present invention is constructed as described above, by rotating the second arc-shaped permanent magnet attached to the return yoke 32 by 180 °, a magnetic field is exerted in the accelerating tube, or an action is caused. It is possible to change the presence / absence of the magnetic field inside the accelerating tube easily by opening the pressure tank containing the accelerating tube and removing a part of the hoop. Adjustment can be done in about 30 minutes by one person.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a magnetic flux path.

FIG. 3 is a layout view of magnet devices in the acceleration tube.

FIG. 4 is a configuration diagram of a conventional magnet device unit.

[Explanation of symbols]

 1 Accelerating Tube 6 Accelerating Electrode 7 Insulating Ring 21 Magnetic Pole / Yoke Member 22 Magnetic Pole 23 Yoke Part 26, 27, 28, 29 Arc Permanent Magnet 30, 30 'First Arc Permanent Magnet 31, 31' Second Arc Permanent Magnet 32 Return yoke

Claims (1)

[Claims] 1. A pair of first arc-shaped permanent magnets, which are provided around the acceleration tube symmetrically with respect to a central axis line between opposing magnetic poles, and whose magnetic pole side end portions are magnetized, and these. First
An annular return yoke that surrounds the arc-shaped permanent magnet, and two second arc-shaped permanent magnets that are mounted inside the return yoke so as to face each other and are rotatable around the magnetic pole and the first arc-shaped permanent magnet. Each permanent magnet has a magnetic pole surface magnetized on the return yoke side and the first arc-shaped permanent magnet side, and the magnetic pole surfaces of the two permanent magnets are magnets.
An accelerating tube with a permanent magnet, comprising: a second arc-shaped permanent magnet that is magnetized with opposite polarities.