JP3144944U - Shading unit mounted on scintillation detector - Google Patents

Abstract

An object of the present invention is to provide a light-shielding unit that is not easily damaged even when a sharp part of an object to be measured comes into contact with an incident window of the scintillation detector, and a scintillation detector including the light-shielding unit.
An incident window I into which radiation to be measured is incident, a light-shielding film f attached to the incident window I, a scintillator S that emits light by the passage of the radiation, and the light is emitted by collision. A photomultiplier tube P for amplifying photoelectrons is provided, and the light shielding film f is further brought into non-adhering contact with the hard light shielding film F on the incident surface side, and an appropriate hard material is disposed on the incident surface side of the hard light shielding film F. A mesh M consisting of
[Selection] Figure 1

Description

  The present invention measures or detects radiation levels and contamination by radioactive materials to ensure safety in environments where radioactive materials are handled, such as nuclear power plants, nuclear / elementary particle research laboratories, or radiotherapy rooms of medical institutions. The present invention relates to a light shielding film used by being mounted on a scintillation detector.

  In environments where radioactive materials are handled, measurement of radiation doses in the environment has been performed in a timely manner, such as gamma-ray measuring devices for air dose monitoring, gate monitors for monitoring surface contamination with radioactive materials, and hand foot cross monitors. . As a measuring device used for such measurement, a survey meter using a scintillation detector is well known.

  For example, a radiation entrance window in an existing β-ray scintillation survey meter is provided with a light-shielding film made of a very thin film material such as polyester in order to suppress attenuation of β-rays to be measured. The light-shielding film is subjected to aluminum vapor deposition on both the front and back surfaces of the film material, and aims to shield the disturbance light incident on the scintillation detector and reduce its influence. Thereby, the influence of disturbance light can be eliminated by covering the entrance window of the scintillation detector with the light shielding film.

  By the way, since this light shielding film is very thin as described above, a sharp portion of a hard object to be measured such as metal or plastic can be easily damaged just by coming into contact with it. It is hardly effective from the viewpoint of protection. Furthermore, there is a serious adverse effect such that the amount of charged particles and the distribution state of radiation energy cannot be correctly grasped due to erroneous counting caused by the influence of ambient light entering from the damaged part. In order to avoid such a problem, a method of attaching a metal mesh of 5 to 10 mm square on the front surface of the entrance window and protecting the light shielding film is generally taken.

  However, in reality, there are not a few cases where the light shielding film is damaged due to contact with a sharp portion of an article to be measured that has entered through a gap between metal meshes.

  In view of the above-mentioned problems of the prior art, the present invention is easily damaged even when a sharp part of an object to be measured comes into contact with the entrance window of the scintillation detector when measuring contamination caused by radioactive materials. It is an object of the present invention to provide a light-shielding unit having no light and a scintillation detector including the light-shielding unit.

  The configuration of the scintillation detector of the present invention, which has been made for the purpose of solving the above-mentioned problems, includes an incident window into which radiation to be measured is incident, a light-shielding film attached to the incident window, and passing light through the radiation. A scintillator that emits light, and a photomultiplier that amplifies photoelectrons emitted by collision with the light; a hard light-shielding film is further detachably brought into contact with the incident surface side of the light-shielding film; A mesh made of an appropriate hard material is disposed on the incident surface side of the film.

  The hard light shielding film of the scintillation detector of the present invention is made of polyester film, polyethylene film, polyimide film, polypropylene film, para-aramid film, polyphenylene film, nylon film, or fluorine film. It is desirable to do.

  In addition, a high-efficiency reflector can be provided around the inner wall surface of the light guide portion from the scintillator included in the scintillation detector of the present invention to the photomultiplier tube.

  The incident surface side of the scintillator of the scintillation detector of the present invention is preferably a rough surface.

  It is desirable that the scintillator of the scintillation detector of the present invention is configured by forming a flat section substantially the same size as the entrance window.

  The light-shielding unit of the present invention is a light-shielding unit that is attached to the entrance window of a scintillation detector that receives the radiation to be measured. The light-shielding film attached to the entrance window and the light-shielding film on the incident surface side of the light shielding film The film is detachably abutted and a mesh made of an appropriate hard material is provided on the incident surface side of the hard light-shielding film.

  In the scintillation detector of the present invention, a hard light shielding film is provided in contact with a removable non-adhered state on the incident surface side of the light shielding film, and a mesh is disposed on the incident surface side of the hard light shielding film. Therefore, even if a sharp part of the object to be measured touches the instrument, it is protected by the mesh, and even if there is a part that enters from the gap of this mesh, the hard light-shielding film described above is On the other hand, this is received by the thickness of the light-shielding film, and the lateral force can be released in the lateral direction due to non-adhesion with the light-shielding film, and the damage to the light-shielding film can be avoided well. Even if the hard light-shielding film is damaged, the hard light-shielding film is detachably disposed and can be easily replaced.

  The hard light-shielding film should be made of polyester film, polyethylene film, polyimide film, polypropylene film, para-aramid film, polyphenylene film, nylon film, or fluorine film with a low density. Can be thin, light and durable.

  In addition, if a high-efficiency reflector is installed around the inner wall of the light guide section from the scintillator to the photomultiplier tube, the scintillation light can efficiently reach the photomultiplier tube. Therefore, the accuracy of the measurement result can be maintained even if the radiation to be measured is attenuated.

  Furthermore, if the radiation incident surface side of the scintillator is formed as a rough surface, scintillation light is emitted irregularly and can efficiently reach the photomultiplier tube, and if it is formed thin, β-ray detection is possible. The lower limit can be improved and the sensitivity of γ-rays can be lowered, which is suitable for detecting β-rays. If it is formed approximately the same size as the entrance window, the relative ratio of the background count rate is lowered. be able to.

  Furthermore, the light-shielding unit of the present invention has an effect that the light-shielding unit provided with the hard light-shielding film having the above-described effects can be detachably attached to the scintillation detector and used easily.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a scintillation detector according to the present invention.

  In FIG. 1, reference numeral 1 denotes a scintillation detector of the present invention, which is an incident window I into which radiation to be measured such as β-rays enters, a light-shielding film f attached to the incident window I, and light passing through the radiation. A scintillator S that emits light and a photomultiplier tube P that amplifies photoelectrons emitted by collision with the light are provided.

  The light shielding film f is made of a very thin film material such as a polyester film, and in order to avoid the influence of the pinhole effect, a plurality of the film materials are laminated in this embodiment.

  On the incident surface side of the light shielding film f, a film material having a thickness of about 5 to 10 times that of the light shielding film f is provided as a hard light shielding film F, and further on the incident surface side of the hard light shielding film F. Is provided with a mesh M made of an appropriate hard material for protection. Although it is possible to avoid the sharp portion of the measurement target from coming into contact with the thin light-shielding film f by the mesh M, as described above, the inconvenience still occurred with respect to the protrusion entering from the gap of the mesh M.

  Here, the hard light shielding film F has a sufficient thickness, and can effectively exert a protective function against an impact in a direction perpendicular to the incident window I. Further, since the hard light-shielding film F is not bonded to the light-shielding film f, the light-shielding film f can be prevented from being damaged by escaping it horizontally to the incident window I in the horizontal direction.

  To make the hard light-shielding film F thin, light and strong, any of polyester film, polyethylene film, polyimide film, polypropylene film, para-aramid film, polyphenylene film, nylon film, and fluorine film It is desirable to use these materials.

  If the light shielding unit U including the light shielding film f, the hard light shielding film F, and the mesh M can be detachably attached to the scintillation detector, the above-described effects can be obtained. It can be easily applied to a type scintillation detector.

  Further, with respect to the attenuation of incident radiation due to the arrangement of the hard light shielding film F, the inner wall surface Gw of the light guide portion G from the scintillator S to the photomultiplier tube P is provided with a high efficiency reflector r (not shown). The scintillation light can efficiently reach the photomultiplier tube P.

  Furthermore, if the radiation incident surface side Sw of the scintillator S is formed into a rough surface, the scintillation light can efficiently reach the photomultiplier tube. Further, if the thickness of the scintillation S is made thin, the lower limit of detection of β rays can be improved and the sensitivity of γ rays can be lowered, so that it is particularly suitable for application to a detector of β rays. Moreover, if the cross-sectional shapes of the entrance window I and the scintillation S are formed to be approximately the same size, the relative ratio of the background count rate, which is noise during detection, can be lowered.

  The present invention is as described above. A harder light-shielding film is provided in contact with the light-shielding film in a non-adhered state, and a mesh is disposed on the light-incident surface of the hard light-shielding film. Therefore, even if a sharp part of the object to be measured touches the instrument, it is protected by the mesh, and even if there is a part that enters from the gap of this mesh, the hard light-shielding film described above is On the other hand, this is received by the thickness of the light-shielding film, and the impact received in the lateral direction due to non-adhesion with the light-shielding film can be released in the lateral direction, and damage to the light-shielding film can be avoided well, Hard light-shielding films are low-density polyester film, polyethylene film, polyimide film, polypropylene film, para-aramid film, polyphenylene film, nylon film. If the material is either Rum or Fluorine film, it can be made thin, light and strong, and a high-efficiency reflector is provided around the inner wall of the light guide from the scintillator to the photomultiplier tube. If this is done, the scintillation light can efficiently reach the photomultiplier tube, so the accuracy of the measurement results can be maintained even if the radiation to be measured is attenuated by adding a hard light-shielding film. If the surface side is formed into a rough surface, scintillation light is emitted irregularly and can efficiently reach the photomultiplier tube, and if the thickness is reduced, the lower limit of detection of β rays can be improved. In addition, the sensitivity of γ-rays can be lowered and it is suitable for detection of β-rays, and if it is formed approximately the same size as the entrance window, the relative ratio of the background count rate can be lowered. Furthermore, the light-shielding unit of the present invention has the effect that the light-shielding unit having the hard light-shielding film having the above-described effects can be easily used by being detachably attached to the scintillation detector. It is extremely useful when applied to scintillation detectors.

Sectional drawing which shows an example of the scintillation detector which concerns on this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Scintillation detector I Incident window G Light guide Gw Inner wall surface S Scintillator Sw Incident surface U Light-shielding unit f Light-shielding film F Hard light-shielding film M Mesh P Photomultiplier tube

Claims (6)

An incident window through which the radiation to be measured is incident;
A light-shielding film attached to the incident window;
A scintillator that emits light by the passage of the radiation;
A photomultiplier tube that amplifies photoelectrons emitted by collision with the light,
A hard light-shielding film is further detachably brought into contact with the incident surface side of the light-shielding film, and
A scintillation detector, wherein a mesh made of an appropriate hard material is disposed on the incident surface side of the hard light-shielding film.   The scintillation according to claim 1, wherein the hard light-shielding film is made of any one of a polyester film, a polyethylene film, a polyimide film, a polypropylene film, a para-aramid film, a polyphenylene film, a nylon film, and a fluorine film. Detector.   The scintillation detector according to claim 1 or 2, wherein a high-efficiency reflector is provided around an inner wall surface of a light guide portion from the scintillator to the photomultiplier tube.   The scintillation detector according to claim 1, wherein an incident surface side of the scintillator is a rough surface.   The scintillation detector according to any one of claims 1 to 4, wherein the scintillator has a flat cross section substantially the same size as the incident window.   A light-shielding unit that is attached to the entrance window of a scintillation detector through which the radiation to be measured enters. A light-shielding film attached to the entrance window, and a hard light-shielding film that can be attached to and detached from the entrance surface side of the light-shielding film A light shielding unit comprising a mesh made of a suitable hard material on the incident surface side of the hard light shielding film.

Images