JPH0442788Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical Field of the Invention] The present invention relates to a reference glass used in a fluorescent glass dosimeter that measures radiation exposure dose, and in particular, to evaluate the reliability of the intensity of fluorescent radiophotoluminescence for comparing the exposure dose. This invention relates to an improved reference glass for fluorescent glass dosimeters. [Technical background of the invention and its problems] Fluorescent glass dosimeters generally use a phosphate glass containing silver ions (hereinafter referred to as silver activated phosphate glass) as a detector; When an acid salt glass body is exposed to radiation, a fluorescent center is generated within the glass body, and when excited by ultraviolet rays, an orange fluorescent radiophotoluminescence is generated. Since this fluorescence intensity is proportional to the amount of radiation exposure, the amount of radiation exposure can be determined by measuring the fluorescence intensity. This radiation dose measurement is carried out by passing light from an ultraviolet excitation light source, such as a mercury lamp, through an optical filter to block light of a predetermined wavelength or more, and then transmitting the transmitted ultraviolet rays to a rectangular parallelepiped-shaped silver activated phosphate glass body. Inject it perpendicularly to the side. Fluorescence emitted from a silver-activated phosphate glass body by ultraviolet excitation is extracted in a direction perpendicular to the incident light beam, and the transmitted light is filtered to block light outside a predetermined wavelength range, and the transmitted light is converted by a photomultiplier tube. Fluorescence is obtained from the output signal. Measure the intensity and determine the exposure dose. In this measurement, a fluorescence standard glass that generates a certain amount of fluorescence is used as a reference glass, and the amount of radiation to which the silver activated phosphate glass body is exposed is determined by comparing the measurement with the reference fluorescence amount of the reference glass. It is something. Generally, the measurement range of a fluorescent glass dosimeter is 10 mR to 10 ³ R (X-Ray), but the reference glass is selected to have a fluorescence amount close to that of the sample to be measured. Traditionally, reference glasses contain Mn ²⁺ ions, Sm ³⁺ ions
A fluorescent glass body containing any one type of Nd ³⁺ ion, or a silver activated phosphate glass body irradiated with a standard radiation dose within the measurement range is used. However, fluorescent glass dosimeters using these reference glasses have the following drawbacks. When a fluorescent glass body containing any one of Mn ²⁺ ions, Sm ³⁺ ions, Nd ³⁺ ions, etc. is used as a reference glass, the temperature coefficient of the fluorescence intensity is similar to that of the radiophotoluminescence of silver-activated phosphate glass. Since the temperature coefficient is different from the temperature coefficient of the tsensence, the measurement must be always performed at a constant room temperature, or the temperature must be corrected based on the room temperature at the time of measurement, which causes measurement errors. In addition, in fluorescent glass dosimeters that adopt the pulse measurement method described in Japanese Patent Publication No. 47-51919 and Japanese Patent Publication No. 50-38352, the fluorescence decay time of the reference glass is the same as that of silver activated phosphoric acid exposed to radiation. Because it is shorter than the fluorescence decay time of salt glass,
The delayed observation time for observing fluorescence due to radiation exposure of the silver activated phosphate glass body does not allow sensitive fluorescence measurements and accurate verification of dose values. If a silver activated phosphate glass body irradiated with a standard radiation dose of less than 10R is used as a reference glass, the drawbacks mentioned above will be resolved, but the silver activated phosphate glass body
Exposure to 100mR of natural radiation causes a change in the amount of fluorescence over time, which causes measurement errors in low-dose measurements. [Purpose of the invention] This invention was made in consideration of the above circumstances.
An object of the present invention is to provide a reference glass for a fluorescent glass dosimeter that improves the reliability of the intensity of fluorescent radiophotoluminescence for comparing the radiation exposure dose. [Summary of the invention] In order to achieve the above-mentioned purpose, the present invention uses a reference glass made of silver-activated phosphate glass that has been exposed to radiation of 10R or more, and partially covers the fluorescence detection surface with metal, plastic, etc. By coating, the intensity of the fluorescent radiophotoluminescence of the reference glass can be adjusted as desired. The reference glass that has been exposed to radiation of 10R or more has a change in fluorescence level of less than 1% per year, even considering exposure to natural radiation, and is therefore suitable for practical use. The present invention reduces the amount of fluorescence emitted by the glass itself by coating a part of the fluorescence detection surface of the rectangular parallelepiped reference glass, excluding the entrance and exit surfaces of the excitation ultraviolet rays, with metal or plastic. This allows it to be used as a reference glass for low-dose measurements. Furthermore, since the amount of fluorescence can be arbitrarily adjusted by changing the covered area of this reference glass, one reference glass can be used to measure radiation doses over a wide range. [Embodiments of the invention] The details of the invention will be explained with reference to illustrated embodiments. The reference glass 2 attached to the holder 1 is made of silver activated phosphate glass (Tokuko Showa) with a composition of 60% by weight of aluminum metaphosphate, 20% by weight of sodium metaphosphate, 20% by weight of sodium orthophosphate, and 0.3% by weight of silver metaphosphate. It is made of glass (described in Japanese Patent No. 50-10333) and polished into a rectangular parallelepiped shape of 15 x 12 x 3.5 ^mm3 . The excitation ultraviolet beam 3 enters the reference glass 2 from above and exits downward.
The fluorescence generated at this time is detected from the direction of the arrow, but by covering a part of the fluorescence detection surface 4 with a mask 5 made of metal, for example, a copper plate,
It is designed to reduce the amount of fluorescence. Therefore, by adjusting the area of the fluorescence detection surface 4 covered by the mask 5, an arbitrary amount of fluorescence can be obtained from the reference glass 2. Next, using a fluorescent glass dosimeter (described in Japanese Patent Publication No. 50-38352) that uses pulsed light from a nitrogen gas laser as the excitation ultraviolet light, ⁶⁰ Coγ rays are applied to the reference glass at 10 ³ R and 3×10 ⁴ The following table shows the results of an investigation of the amount of fluorescence generated by irradiating R and varying the area of the mask covering the fluorescence detection surface. The mask area is the ratio of the reference glass to the fluorescence detection surface.

[Effect of idea]

As described above, the present invention is a reference glass made of silver-activated phosphate glass that has been exposed to radiation of 10R or more, and a part of the fluorescence detection surface is coated with metal or plastic to generate fluorescent radiophotoluminescence. Since the intensity of the radiation can be adjusted arbitrarily, it can be used as a reference glass for measuring not only low doses but also a wide range of radiation doses. In addition, there is no difference between this reference glass and the glass to be measured in terms of temperature coefficient of fluorescence intensity and fluorescence decay time.
Accurate verification is possible and has the effect of greatly contributing to improving the measurement accuracy of fluorescent glass dosimeters.

[Brief explanation of the drawing]

The drawing is a perspective view showing an embodiment of the present invention. 2... Reference glass, 4... Fluorescence detection surface, 5...
mask.

Claims (1)

[Scope of utility model registration request] In reference glass used in fluorescent glass dosimeters that measure radiation exposure doses, the fluorescence detection surface of the reference glass made of silver-activated phosphate glass that has been exposed to radiation of 10R (X-ray) or more is partially covered. A reference glass for a fluorescent glass dosimeter, characterized in that the intensity of the fluorescent radiophotoluminescence can be arbitrarily adjusted.