Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
  • G01T3/00—Measuring neutron radiation
  • G01T3/06—Measuring neutron radiation with scintillation detectors

Definitions

• the present invention relates to a neutron detector, and more particularly to a neutron detector using a neutron scintillator.
• a neutron detector for detecting neutrons a neutron detector using a neutron scintillator as a neutron detection medium has been known.
• a Li glass scintillator is used as a neutron detection medium.
• the Li glass scintillator responds faster than other scintillators, but it cannot be said that the response speed is high enough for high-intensity neutron flux.
• the neutron detector there is a problem that it is difficult to detect a high intensity neutron flux.
• the conventional neutron detector using a Li glass scintillator has a problem that when a large amount of neutrons are irradiated, the amount of current flowing through the optical sensor increases and the operation becomes unstable.
• Non-Patent Document 1 K. Mizukami et al., Nucl. Instr. Meth. A529 (2004) 31 0
• Non-Patent Document 2 Seto Sato, Ripples (Journal of Neutron Science Society of Japan) Vol. 15— 1 (2005) 78 Disclosure of the Invention
• the present invention has been made in view of the problems of the conventional techniques as described above, and the object of the present invention is to detect neutrons that can detect a high-intensity neutron flux. Is to provide a vessel.
• Another object of the present invention is to provide a neutron detector that does not become unstable when a large amount of neutrons are irradiated.
• an object of the present invention is to provide a neutron detector capable of directly measuring a neutron flux.
• the present invention is configured such that a neutron detector is configured using a neutron scintillator that responds at high speed.
• a neutron detector is configured using a neutron scintillator that responds at high speed.
• a neutron scintillator whose response speed is about two orders of magnitude faster than that of a conventional Li glass scintillator, for example, a single crystal having a composition ratio of Li BO disclosed by the applicant of the present application in JP 2003-183637 A is used.
• a small amount for example, Cu, Cu O, 0.001
• This Cu-added LBO single-crystal neutron scintillator responds to the conventional Li glass scintillator about two orders of magnitude faster, and the amount of luminescence is small. There are advantages such as avoiding current saturation, and when combined with an optical sensor, direct measurement of high-intensity neutron flux is possible.
• the present invention provides a neutron detector using a neutron scintillator as a neutron detection medium, a frame having a plurality of holes formed therein, and a neutron fitted into the holes formed in the frame.
• the scintillator has a photocathode pixel to which the output signal of the neutron scintillator hawk is input, and a photodetection unit that obtains a neutron image based on the output signal from the photocathode pixel.
• the neutron scintillator has a composition ratio of Li
• the neutron scintillator is made of a material obtained by adding a small amount of Cu to a single crystal having a composition ratio of LiBO.
• the present invention is the above-described invention, wherein the light detection unit includes a plurality of the neutron scintillators arranged for one photocathode pixel, and the plurality of the neutron scintillators.
• the output signal is input to the one photocathode pixel, a neutron image is obtained.
• the plurality of neutron scintillators are two neutron scintillators adjacent to each other.
• the light detection unit includes one neutron scintillator for each of the plurality of photocathode pixels, and the one neutron scintillator.
• a neutron image is obtained when an output signal of the hawk is input to the plurality of photocathode pixels.
• FIG. 1 is an exploded perspective view of a conceptual configuration of a first embodiment of a neutron detector according to the present invention.
• FIG. 2 is a circuit configuration diagram of some pixels of the multi-anod photomultiplier tube in the first embodiment of the neutron detector according to the present invention.
• FIG. 3 is a partial plan view of a second embodiment of the neutron detector according to the present invention.
• FIG. 4 is a diagram illustrating a multi-anodic structure in a second embodiment of the neutron detector according to the present invention. It is a circuit block diagram about some pixels of a photomultiplier tube.
• FIG. 1 shows an exploded perspective view of a conceptual configuration of a first embodiment of a neutron detector according to the present invention.
• the neutron detector 10 includes a neutron scintillator section.
• 16 square holes 22a each having a planar shape of 2 mm in length X 2 mm in width are arranged in a two-dimensional matrix along a predetermined direction and orthogonal to the predetermined direction.
• a frame 22 having a total of 256 holes 22a is provided.
• the size of the hole 22a may be set to an appropriate size corresponding to the size of the photocathode pixel 32 (described later) of the multi-anode photomultiplier tube 30.
• the material of the frame 22 is not limited.
• the holes 22a can be easily formed by laser processing or the like.
• all the holes 22a of the frame body 22 are provided with a neutron scintillator 24 formed in a quadrangular prism shape having a size that fits tightly into the hole 22a (see FIG. 1).
• a state in which the neutron scintillator 24 is provided only in a part of the holes 22a is shown, but when the neutron detector 10 is actually used, FIG. Will have neutron scintillators 24 in all 22a.
• the neutron scintillator 24 formed in the shape of a quadrangular prism having a size that fits tightly into the hole 22a can be easily obtained by appropriately cutting a neutron scintillator formed in a plate shape. Can be mass-produced.
• the neutron scintillator 24 for example, it is preferable to use a neutron scintillator having a very short emission time of 1 to 2 nanoseconds when capturing neutrons.
• a neutron scintillator 24 a material obtained by adding a small amount of Cu to a single crystal having a composition ratio of Li BO disclosed by the applicant of the present invention described in JP 2003-183637 A (Li BO: C
• neutron scintillator Cu-added LBO single crystal neutron scintillator
• FIG. 2 shows a circuit configuration diagram for some pixels of the multi-anode photomultiplier tube 30.
• the multi-anode photomultiplier tube 30 includes a photocathode pixel 32 disposed in a one-to-one correspondence with each of the neutron scintillators 24, and an amplifier circuit that amplifies an output signal from the photocathode pixel 32. 34, a discriminator circuit 36 for digitizing the output signal from the amplifier circuit 34, and a counting circuit 38 for counting the signals that have passed through the discriminator circuit 36 to obtain a neutron image. ing.
• the neutron scintillator 24 when the neutron is incident on the neutron scintillator 24, the neutron scintillator 24 emits fluorescence. The light enters the cell 32 and a signal is output from the photocathode pixel 32.
• the output signal from the photocathode pixel 32 is amplified by an amplifier circuit 34 and then input to a discriminator circuit 36 for digitization.
• the position of the neutron scintillator 24 is determined by the frame 22, and the light shielding function is achieved by the frame 22, so that the accuracy of neutron detection can be improved.
• the neutron detector 10 may be configured so that each of the neutron scintillators 24 and each of the photocathode pixels 32 have a one-to-one correspondence!
• FIG. 3 illustrates a neutron detector with improved noise removal capability as a second embodiment of the neutron detector according to the present invention, with reference to FIG. 3 and FIG.
• the meson detector 100 according to the second embodiment of the meson detector of the present invention has a one-to-one correspondence between each of the meson scintillators 24 and each of the photocathode pixels 32.
• each of the neutron scintillators 24 and each of the photocathode pixels 32 are arranged in half so as to shift the positions of the two adjacent photocathode pixels.
• One neutron scintillator 24 is arranged for 32.
• the multi-pixel type multi-anode photomultiplier tube 130 serving as a photodetection unit having a position resolution is connected to the discriminator circuit 36.
• the Cu-added LBO single crystal neutral scintillator that can be used as the neutron scintillator 24 is characterized by a high-speed response and a small amount of light.
• a high-speed response is essential to achieve a high count rate.However, if the amount of light is too large, the output signal from the photocathode pixel 32 becomes too large under a high count rate. The entire circuit including pixel 32 becomes unstable.
• the position of the neutron scintillator 24 is used as described above with reference to FIGS. 3 and 4 in order to improve the SZN ratio using the coincidence method. And the position of the photocathode pixel 32 are shifted by half, so that the output of one neutron scintillator 24 is input to two adjacent photocathode pixels 3 2.
• the multi-anode photomultiplier tube 130 is provided with an AND circuit 132 that observes coincidence (simultaneous measurement) of the photocathode pixel 32 adjacent to the rear stage of the discriminator circuit 36.
• the counting circuit performs neutron detection counting, and a force signal is output only to one of the two adjacent photocathode pixels 32. If this is the case, it will be judged as noise and neutron detection will not be counted.
• the neutron scintillator that can be used as the force neutron scintillator 24 using the Cu-added LBO single crystal neutron scintillator as the neutron scintillator 24 is not limited to this. If it has high-speed response, it can be made of other materials. For example, Cu A single crystal having a composition ratio of Li BO that is not added can be used.
• the position of the neutron scintillator 24 and the position of the photocathode pixel 32 are shifted by half, and the output of one neutron scintillator 24 is input to two adjacent photocathode pixels 32.
• the force is not limited to this. That is, the output of one neutron scintillator 24 is arranged in the shape of a rice field so that the neutron scintillator 24 is arranged only in the center of the photocathode pixel 32 arranged in the shape of a square.
• the output of one neutron scintillator 24 may be input to a plurality of photocathode pixels 32, such as to be inputted to four photocathode pixels 32 adjacent to each other!
• the positional relationship between the position of the neutron scintillator 24 and the photocathode pixel 32 may be reversed.
• one photocathode pixel 32 may be arranged for two adjacent neutron scintillators 24.
• the neutron scintillator 24 and the photocathode pixel 32 have a square shape as a planar shape, which is of course not limited to this, and may be a round shape.
• the force for forming the 256 holes 22a in the frame body 22 is not limited to this, and the number of the holes 22a is appropriately determined according to the design. Should be set.
• the size of the hole 22a having a square shape in the plan view is 2 mm in length X 2 mm in width.
• the size is not limited to this. Should be set appropriately according to the design!
• the frame body 22 is formed of a resin material or the like.
• the material of the frame body 22 is not limited to this, and the surface of the metal is coated with resin. Such materials can be used as appropriate.
• the shape of the frame body 22 is not limited to a rigid body that can stand alone, and may not be self-supporting, for example, a film-like shape.
• the present invention can directly measure a high-intensity neutron flux, it can be used mainly as a beam monitor in neutron experiment facilities around the world, and can also be used as a neutron radiograph.
• the direct measurement of neutron flux is one of the measurement methods required in the J-PAR C neutron experimental facility that is currently being promoted as a national project, and in the neutron experimental facility using a small accelerator that can be expected to progress in the future.
• a direct measurement is possible.

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• 2006
  • 2006-01-06 JP JP2006001164A patent/JP2007183149A/ja active Pending
  • 2006-12-29 WO PCT/JP2006/326293 patent/WO2007077939A1/ja not_active Ceased

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