JPS6259799B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to a target device, particularly a target of a particle accelerator such as a medical cyclotron.
This invention relates to a target device for producing short-lived radioisotopes such as ¹¹ C, ¹³ N, ¹⁵ O, etc.

To produce radioisotopes using a cyclotron, the target material is sealed in a metal target box under a high pressure of several atmospheres in order to improve the efficiency of the nuclear reaction, and the material is placed over the beam entrance window facing the acceleration box of the target box. Accelerated particles were applied to the elements of the target material through the target oil to cause a nuclear reaction.

However, when such nuclear reactions produce isotopes of highly chemically corrosive elements in the gaseous state such as ¹⁸ F, the parts of the target box that come into contact with the gaseous elements, especially the beam entrance window of the target box, are The target oil used was susceptible to corrosion. In addition, there is a drawback in that when the target oil is made thicker, the energy of the incident beam is significantly reduced. On the other hand, if the thickness of the foil is made thinner in order to reduce the energy loss, its thermal conductivity will decrease, and the target foil will become thermally unstable due to the heat generation due to the energy reduction of the incident beam and the pressure of several atmospheres of target material applied to the foil. and mechanically susceptible to damage. Therefore, target boxes and target oils for producing short-lived radioisotopes such as ¹¹ C, ¹³ N, ¹⁵ O, and ¹⁸ F are sensitive to the state (gas or liquid) of the target substance filled inside and its chemical properties (corrosiveness, etc.). , adsorption properties, etc.), it had to be replaced frequently.

The present invention solves this problem by providing a target device in which the target box and target oil can be easily replaced, and the entire system can be cooled.

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

As shown in the first figure, an insulating tube 11 is slidably fitted into an adapter guide pipe 10 fixed to the main body of the cyclotron.
Stainless steel target guide pipe 1 inside 1
Fix 2. The target guide pipe 12 is restrained to the adapter guide pipe 10 by a pin and a keyway (not shown) so as not to rotate. At the left end of this target guide pipe 12 is a stainless steel acceleration box block 14 fixed to the main body of the cyclotron through a Teflon insulating material 13.
An annular adapter 15 having a conical outer surface that fits tightly into the center hole of the adapter is attached with screws 16.
Note that 17 is a sealing O-ring. A long hole 18 is provided in the center of this adapter 15, and this long hole 18
A foil 19 made of aluminum with a thickness of 20μ is in contact with the outside of the foil 19, and a presser foot 21 having an elongated hole 20 as shown in the second figure is placed on top of the foil 19 with screws 22,
22... to fix it.

As shown in the first figure, a neutron shielding block 23 made of plastic such as polyethylene is slidably fitted into the target guide pipe 12. The end face of the target box 24 is attached to the tip of the shielding block 23 with bolts 25, 25...
Fixed by...

This target box 24 consists of an outer casing 26 having a hollow conical outer surface, and a cylindrical inner casing 28 that forms a target substance chamber 27 that fits inside the outer casing 26. A space 29 through which cooling water flows is formed between them. The rear surface of the conical end 30 formed at the front end of the inner casing 28 is fixed to a flange 31 formed at the front end of the outer casing 26 with bolts 32, and a sealing O-ring 33 is inserted between them.

The adapter 1 is attached to the outside of this conical end 30.
A conical surface 34 is formed which tightly fits on the inner surface of the conical surface 5, and an O-ring 35 for sealing the conical surface 34 is provided between the conical surfaces 34 and 34. At the rear end of the inner housing 28, there are holes 36, 3 for feeding a gaseous target substance into the chamber 27 at approximately 5 atmospheres.
7 is fixed by bolts 39, 39, . . . , and a sealing O-ring 40 is interposed therebetween. This bottom 38 is tightly fitted into the center of the bottom of the outer casing 26 via an O-ring 41, and pipes 42 and 43 communicating with the through holes 36 and 37 are connected to the rear surface thereof.

As shown in Figure 3, this target box 24
The target oil 44 is brought into contact with the open end 30 of the inner casing 28, and the screw 47 of the presser foot 46 has an elongated hole 45 as shown in the third figure.
47... to fix it. The target foil 44 is an aluminum foil having a thickness of 10 to 40 microns, preferably 20 microns. Helium gas cooled with liquid nitrogen is sent into the space between the foil 19 and the target foil 44.

As shown in the first and fourth figures, a ring 50 is fixed to the rear end surface of the target guide pipe 12 with bolts 51, a support ring 52 is fixed to this ring 50 with bolts 53, 53, and furthermore, this support ring 52 The horizontal frame 54 is fixed with screws 55, 55. A threaded barrel 58 having a hexagonal hole 57 into which a handle 56 is fitted is fitted into the center of the horizontal frame 54 so as to rotate but not move back and forth. A housing 60 connected to the threaded shaft 59 is provided with an engaging element 61 that engages with the shielding block 23 in a bayonet manner so as to be rotated by an operating lever 62.

A gear 63 having an L-shaped cross section is fitted to the rear outer periphery of the target guide pipe 12 for rotation, and a pinion 64 fitted to the ring 52 for rotation is meshed with this gear 63. A hexagonal hole 65 into which the handle 56 is fitted is provided on the rear surface. A screw ring 67 made of an insulator made of Bakelite is fixed to the vertical flange of the gear 63 with bolts 68, and a spiral 66 extending in the circumferential direction provided on the outer peripheral surface of the screw ring 67 is connected to the rear of the adapter guide pipe 10. The target guide pipe 12 is screwed into the spiral provided on the inner peripheral surface, and the front surface thereof is a target guide pipe 12.
It comes into contact with a flange 69 provided at the rear of the flange 69.

Next, the operation of this device will be explained. The gaseous target substance is contained in the pipes 42, 43 and through holes 36, 37.
The target box 24 is supplied into the chamber 27 through the target box 24.

On the other hand, when the handle 56 is fitted into the hexagonal hole 65 and the pinion 64 is rotated, the gear 63 and the screw ring 67 are rotated, and the screw ring 67 moves forward due to the spiral 66, moving the flange 69 of the target guide pipe 12 forward. Press and slide the insulating tube 11 to tightly fit the adapter 15 into the acceleration box block 14. In addition, the handle 56 is fitted into the hexagonal hole 57 and the screw tube 58
When rotated, the screw shaft 59 moves forward, and the engager 61,
Target box 2 via shielding block 23
4 advances and fits the conical surface 34 of its conical end 30 tightly into the adapter 15.

A cooling device (not shown) supplies cooling water to the space 29 and helium gas cooled with liquid nitrogen to the space between the foil 19 and the target foil 44 at a pressure of about 2 atmospheres, and the target box 24 and the foil 19. Target oil 4
Cool 4.

In this way, when charged particles such as protons and deutrons are accelerated in the acceleration box and the particle beam is made incident on the foil 19, the particle beam reaches the target foil 44.
The light enters the target box 24 through the rays, causes a nuclear reaction in the target substance therein, and produces an isotope such as ¹⁸ F.

In the above device, the target guide pipe 12
is electrically insulated from the adapter guide pipe 10 by an insulating tube 11, the acceleration box block 14 is electrically insulated from the cyclotron body by an insulating material 13, and the rear part of the target guide pipe 12 is electrically insulated from the adapter guide pipe 10 by an insulating screw ring 67. ing. Therefore, the total amount of beam incident on the target box can be electrically measured.

Furthermore, since there is a shielding block 23 made of plastic behind the target box 24, leakage of neutrons to the outside can be prevented.

In the above device, if the handle 56 is used to rotate the pinion 64 and the screw ring 67 in the opposite direction, and the spiral 66 of the screw ring 67 is removed from the adapter guide pipe 10, the insulating tube 11, target guide pipe 12, and adapter 15 can be connected to the adapter. It can be removed by pulling it out from the guide pipe 10. Further, when the engaging element 61 is rotated by the operation lever 62 to operate backward and removed from the shielding block 23, the shielding block 23 and the target box 24 can freely slide inside the target guide pipe 12. Therefore, the oil 19 of the adapter 15, the target oil 44, the target box 24, the O-rings 17, 35, etc. can be easily replaced.
Further, by removing the bolts 32 of the target box 24, it can be disassembled into the outer casing 26 and the inner casing 28, and each part can be cleaned.

As described above, in the present invention, the adapter that fits tightly into the acceleration box block and the target box that fits tightly into the adapter are provided to slide into the adapter guide pipe and the target guide pipe, respectively, so that the adapter's oil and The target box and target oil can be easily replaced, and the target box has a space for cooling water circulation, and helium gas cooled with liquid nitrogen is sent between the adapter oil and the target oil. Therefore, all parts of the beam that generate heat can be cooled, and in particular, the pressure of helium gas acts on the target oil in the opposite direction to the pressure on the target material, so its thermal and mechanical stress is relaxed. This can prevent the damage.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing an outline of the target of a cyclotron to which the present invention is applied, and Figure 2 is the same as Figure 1.
FIG. 3 is a sectional view taken along line AA, FIG. 3 is a sectional view taken along line BB, and FIG. 4 is a right end view of FIG. 1 with the handle removed. 10...Adapter guide pipe, 11...Insulation tube, 12...Target guide pipe, 1
4...Acceleration box block, 15...Adapter, 18
... hole, 19 ... oil, 23 ... shielding block, 27 ... chamber, 24 ... target box,
29... Space, 30... Open end, 44... Target oil.

Claims (1)

[Claims] 1. An insulating tube and a target guide pipe are slidably fitted into the adapter guide pipe fixed to the main body of the cyclotron, and an adapter that tightly fits into the acceleration box block is attached to this target guide pipe. A foil is removably fixed in the hole, a shielding block made of plastic is slidably fitted into the target guide pipe, and a target box having a chamber for supplying a target substance is fixed to the shielding block. This target box is provided with a space for the circulation of cooling water, and its end is tightly fitted into the inner surface of the adapter, and a target oil is removably fixed to the open end of the target box. A target device characterized in that helium gas cooled with liquid nitrogen is sent between target oils.