JPH0439640B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a beam current distribution homogenizing magnet device used, for example, in neutron damage tests of fusion reactor materials, fast breeder reactor materials, or creep tests under light ion irradiation of other materials. .

As a simulation of neutron damage to reactor materials for fusion reactors and fast breeder reactors, creep tests under irradiation using light ions ejected from a cyclotron have been conducted.

In this irradiation creep test, the sample is irradiated with a light ion beam at a constant temperature and under a constant load, and the sample is not irradiated with a light ion beam (thermal creep only).
The aim is to obtain the creep characteristics under light ion irradiation by detecting the difference in the creep rate of the sample. This material creep property is
Since it is most sensitive to temperature, temperature control of the sample is important. In this test, the temperature is controlled by detecting the wavelength of infrared rays emitted from the center of the sample, determining the sample temperature from its temperature characteristics, and feeding this back to the sample heating power source. However, the beam current distribution of the light ion beam taken out from the cyclotron becomes a Gaussian distribution due to the focusing action of the group of quadrupole electromagnets in the beam transport system. When a sample is irradiated with a light ion beam having such a Gaussian distribution, the temperature near the center of the sample increases compared to the temperature at the edges of the sample. Therefore, the heating applied to the sample is controlled to be smaller than it actually is, and the average temperature of the sample is lower than in the case of only thermal creep, so that the creep caused by light ion irradiation appears to be smaller. For this reason, precise creep tests under light ion irradiation are difficult when the beam current distribution is Gaussian.

In the creep test under light ion irradiation, the irradiation beam current distribution is required to be uniform on the irradiated sample surface.

The present invention achieves this object by providing a beam current uniformizing magnet device that converts a Gaussian beam current distribution taken out from an accelerator and transported by a beam transport system into a trapezoidal beam current distribution. be.

That is, in the present invention, the first
A magnet and a second magnet are arranged in two positions, front and rear, and the positions of the magnetic pole pieces of the front and rear magnets are shifted from each other in the beam current distribution direction, and the magnetic field is distributed in the area of each magnetic pole piece. The magnetic poles of the front and rear magnets are opposite to each other, and the polarities of their magnetic fields are opposite to each other. The force acting on the remaining half of the beam is made to have divergence near the peak at the beam center and convergence near the beam end, and the subsequent magnet causes the force acting on the remaining half of the beam to become divergent near the peak at the beam center and converge near the beam end. The front and rear magnets each have a peak diverging pole piece that deflects the peak half of the beam toward the respective ends, and an end-clamping pole piece that deflects the beam end toward the center, respectively. A beam current distribution uniformizing magnet device is characterized in that the beam current distribution is made uniform.

That is, in the embodiment of the present invention, the magnets are arranged in two stages, front and rear, in the beam traveling direction, and each magnet has two sets of pole pieces, a yoke, and a yoke.
It consists of an excitation coil, a return yoke, a position adjustment mechanism, etc., and the positions of the magnetic pole pieces of the front and rear magnets are shifted from each other in the beam current distribution direction, and the magnetic field is The magnetic poles of the magnets in the front and rear stages are opposite to each other, and the polarities of their magnetic fields are opposite to each other. The beam has divergence near the beam and convergence near the edge.

In the present invention, a permanent magnet may be used instead of an electromagnet, and the present invention is not limited to simply testing materials. Of course, it can also be applied to breakage prevention, etc.

An embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in the first diagram, the acceleration box 1 of the cyclotron
A beam 2 of emitted vertically elongated light ions is guided to a target 4 through a vertically elongated rectangular duct 3 made of a non-magnetic material such as aluminum as shown in the second figure. Assume that a sample loaded in the vertical direction is placed on the target 4 for performing a creep test under light ion irradiation, for example. Note that 5 in FIG. 2 is a support frame surrounding the duct 3.

As shown in Figures 2 to 4, first and second electromagnetic coils 10, 10, 11, 11 are sequentially provided on both sides of the duct 3 in two stages, front and rear, in the direction of movement of the beam 2. and second electromagnetic coil 1
0, 10, 11, and 11 are fixed to the support frame 5, and direct current flows in opposite directions to each other. 2nd to 4th
In the figure, only the first electromagnetic coil 10 at the front stage is shown, but the second electromagnetic coils 10 and 11 at the rear stage have exactly the same structure, and these electromagnetic coils 10 and 11 are spaced apart in the front and rear direction so that their magnetic fields do not interfere with each other. let

As shown in the third diagram, the first electromagnetic coil 1
Dovetail grooves 14, 1 extending in the vertical direction are provided on the surfaces of the yokes 13, 13 at the center of the yokes 13, 10 facing the duct 3.
4 are formed by rails 15, 15, respectively, and these dovetail grooves 14, 14 are provided with upper and lower magnetic pole pieces 16, respectively.
16, 17, and 17 are fitted together to move up and down.

The upper and lower magnetic pole pieces 16, 16, 17, and 17 are connected to the lower and upper ends of the upper and lower adjusting rods 18, 18, 19, and 19 to rotate, respectively, and are restrained at the upper and lower ends. Adjustment rod 18, 18, 1
Numerals 9 and 19 are screwed into fixing nuts 20, 20, 21, and 21 fixed to the yokes 13 and 13, respectively, and their upper and lower protruding ends are square shaft portions 2 for engaging rotary tools.
2, 22, 23, 23 are formed.

As shown in FIG. 5, the upper magnetic pole pieces 16, 16 of the first electromagnetic coil 10 are magnetic poles for peak dispersion, and are positioned slightly above the central peak of the beam 2 and opposite to each other, and the lower magnetic pole piece 17 , 17 are magnetic poles for end alignment, and are positioned opposite to the lower end of the beam 2. a magnetic pole piece 24 under the second electromagnetic coil 11;
24 is a magnetic pole for peak dispersion, which is positioned slightly below the peak at the center of the beam 2 and opposed to it; upper magnetic pole pieces 25, 25 are magnetic poles for edge alignment, and are positioned so as to oppose the upper end of the beam 2. to be located.

Next, the operation of this device will be explained.

The beam 2 of light ions ejected from the acceleration box 1 of the cyclotron is band-shaped, and is represented by curves a in Figures 5, 6, and 8.
As shown in , the intensity has a Gaussian distribution in the vertical direction, and the intensity distribution is strong near the center and becomes weaker toward the upper and lower peripheries.

When this beam 2 passes between the magnetic pole pieces 16 and 17 of the first electromagnetic coil 10, the magnetic field _h1 acts on a partial region of the beam 2 as shown in FIG.
Apply upward force as shown by the arrows in the figure to the upper and lower ends of the peak. Therefore, the magnetic field of the upper pole piece 16 deflects the upper half of the peak of the beam 2 upward, thereby dispersing the peak, and the magnetic field of the lower pole piece 17 deflects the lower end of the beam 2 upward. The beam at the bottom is centered. Therefore, the intensity distribution of beam 2 becomes as shown by curve b in FIG.

Next, when the beam 2 passes between the magnetic pole pieces 24 and 25 of the second electromagnetic coil 11, a magnetic field as shown in FIG.
h ₂ acts on a partial region of beam 2, and its magnetic field h ₂
Since the direction of is opposite to the direction of the magnetic field _h1 ,
Apply a downward force to the lower half and upper end of the peak, as shown by the dotted arrows in the figure. Therefore the lower pole piece 2
4 deflects the lower half of the peak of beam 2 downward, dispersing the peak, and also dispersing the upper pole piece 2.
The upper end of the beam 2 is deflected downward by the magnetic field 5, so that the upper end beam is centered. Therefore, the intensity distribution of the beam 2 becomes a flat trapezoidal distribution as shown by the curve c shown in the fifth and eighth figures.

Therefore, the current distribution in the load direction (creep direction) of the irradiated sample in the beam 2 can be corrected from a Gaussian distribution to a trapezoidal distribution.

As described above, according to the present invention, due to the difference in the position of the magnetic pole pieces of the magnets in the front and rear stages, the beam is
Through the latter-stage magnet, a force is applied that causes the beam to become divergent near the peak at the center of the beam and convergent near the ends of the beam, thereby changing the Gaussian beam current distribution to a trapezoidal beam current distribution. Therefore, in material loading tests, the sample can be irradiated with a light ion beam with a trapezoidal beam current distribution in the loading direction, so the temperature distribution of the sample in the loading direction is uniform, making it possible to control the temperature at the center of the sample. With this method, the temperature of the entire sample can be accurately controlled, and the creep characteristics of the material under beam irradiation can be precisely measured.This will greatly contribute to the development of reactor materials for fusion reactors and fast breeder reactors.

[Brief explanation of drawings]

Fig. 1 is a plan view of a cyclotron to which the present invention is applied, Fig. 2 is an end view taken along the line A--A in Fig. 1, Fig. 3 is a plan view of Fig. 1, and Fig. 4 is Fig. 3 B.
-A side view as seen from line B, Figure 5A is a side view explanatory diagram showing the relationship between the magnetic poles of the beam, Figure 5B is a top view explanatory diagram of the same, and Figure 6 is the first electromagnetic coil portion thereof. FIG. 7 is an explanatory diagram showing the relationship between the magnetic field and the beam intensity distribution in the second electromagnetic coil portion, and FIG.
The figure is a graph showing the intensity distribution of the beam according to the present invention. 2... Beam, 10, 11... First and second magnets, 16, 24... Magnetic pole piece, 17, 25... Magnetic pole piece.

Claims (1)

[Claims] 1. A first magnet and a second magnet are arranged in two stages, front and rear, in the beam traveling direction, and the positions of the magnetic pole pieces of the front and rear magnets are shifted from each other in the beam current distribution direction, The magnetic field is partially high only in the area of each magnetic pole piece, and the magnetic poles of the front and rear magnets are in opposite directions, so the polarity of their magnetic fields is opposite to each other. The force acting on one half of the beam is diverging near the peak at the beam center and convergent near the beam end, and the subsequent magnet is designed so that the force acting on the other half of the beam is diverging near the peak at the beam center. , focusing near the ends of the beam, so that these front and rear magnets each have a peak divergent pole piece that deflects half of the peak of the beam toward the ends, respectively. 1. A beam current distribution equalizing magnet device, characterized in that it comprises magnetic pole pieces for end-approaching, each of which is deflected toward the center.