JP2002071811A - Measuring method and its device by luminescence combined with small x-ray irradiation means for accumulating radiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a luminescence measuring method and a device for the measurement with easy handling and capable of measuring history of a measurement target substance with more accuracy. SOLUTION: This device measuring the history of the measurement target substance by radiation luminescence is characterized by that it has a measurement target substance container carrying means 1 controlling a measurement target substance container SC holding the measurement target substance to move it to an X-ray irradiating position XP and an excitation energy applying position, exciting means 2 and 3 exciting the measurement target substance and causing it to emit luminescence light, a luminescence light measuring means 5 measuring intensity of the emitted luminescence light as an absolute value and having a member shutting out noise due to heat and light from outside, a luminescence light guiding means LG comprising a member 6 transmitting the luminescence light from the measurement target substance to the luminescence light measuring means and shutting out generation of noise due to heat and light from the outside and the exiting means and a luminescence light guiding member 4 transmitting the luminescence light held by the member 6 without diffusing it, and an X-ray irradiator 7 causing a known accumulated age equivalent radiation dose to accumulate on the measurement target substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention repeatedly performs luminescence measurement, accumulation of radiation with a plurality of known doses of X-rays, and measurement of luminescence after the irradiation using the same substance to be measured. The present invention relates to a method and a measuring device for measuring the history of a substance to be measured by measuring accumulated radiation with high accuracy.

[0002]

2. Description of the Related Art Measurement of natural accumulated dose derived from natural radiation is useful for geological and archeological ages and for environmental evaluation such as heat exposure and exploration of uranium and thorium as energy resources. The measurement of the accumulated dose of the artificial radiation dose is indispensable for the management of personal exposure in health physics and the evaluation of the exposure dose in case of radiation accident. Observation of radiation-induced luminescence is based on thermoluminescence (Thermoluminesc
encer, TL), optically stimulated luminescence (OSL) accompanying light irradiation is used. In recent years, based on quartz and feldspar particles extracted from sedimentary strata and calcined archeological sites, luminescence measurement and irradiation of known doses are repeatedly performed without altering the same sample to obtain highly accurate accumulated radiation. Single fraction (Single a
liquot) method has proven to be the best. As described above, in order to perform the repeated measurement and the irradiation of the known amount of radiation, a luminescence measuring device having a radiation source for irradiation is required. This type of commercially available measuring instrument is equipped with an RI radiation source (Sr-Y-90β radiation source) as the known amount of radiation irradiating device. However, due to strict legal regulations on the handling of the RI source, a measuring instrument equipped with the known radiation irradiation device cannot be easily introduced, and the actual handling is extremely nervous.

In addition, the present inventor has pursued the emission mechanism of radiation-induced luminescence from the basics. Among them, natural quartz particles (including trace impurities such as aluminum, the amount of the impurities and the existence form thereof are determined by the production area, There is a difference depending on the thermal history of natural quartz, etc.), and it was found that there was red luminescence. In the measurement of natural minerals, we found that red luminescence was remarkable from volcanic quartz particles in Japan and quartz particles from heated earthenware and old kilns. From these experimental results, it was found that luminescence measurement using red luminescence or the like as a detection wavelength range is useful.

However, many commercially available measuring instruments do not have a means for measuring red luminescence, and the measured luminescence is limited to the blue spectral region. On the other hand, as described above, many of natural and artificial substances to be measured have a history of volcanic activity and firing action, and it is useful to use red luminescence in a long wavelength region as a measuring means. is there.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to measure the accumulated radiation with high accuracy by eliminating the need for the above-mentioned RI source and enabling the measurement of red luminescence. An object of the present invention is to provide a method for measuring the history of a substance and a measuring device for the measuring method. The present inventor has studied a means for measuring a known amount of radiation storage means and red luminescence with a reduced noise in place of an RI source in order to develop the measurement method and a measurement apparatus for realizing the method, That the small-sized X-ray generation means is useful as a known amount of radiation storage means, and that luminescence light guide means for efficiently transmitting luminescence light emitted from the substance to be measured to the luminescence light measurement means is used, and It has been found that the problem can be solved by developing means for efficiently heating and cooling the sample to be measured.

[0006]

A first aspect of the present invention is to excite stored radiation of a substance to be measured with external energy from an excitation means and emit near-ultraviolet to near-infrared luminescence. The intensity is measured as an absolute value, and then the substance to be measured is irradiated with X-rays for accumulating a known (approximately equivalent to the accumulation year) radiation dose, and then excited by external energy by the excitation means, and the emission luminescence intensity Is performed at least twice by changing the X-ray irradiation dose,
Calculating the accumulated years of accumulated radiation dose of the substance to be measured from the intensity of luminescence from the sample to be measured and the change in luminescence intensity after X-ray irradiation corresponding to the known accumulated years. This is a method for measuring the history of a sample to be measured by luminescence. Preferably, the external energy from the excitation means is heat and / or visible light to near-infrared light, and the method is a method for measuring the history of a substance to be measured by the radioluminescence. In order to transmit the excited luminescence emitted from the substance to the luminescence measuring means for measuring the intensity of the luminescence, the luminescence light held by the member that blocks noise due to external heat and light is transmitted. A method for measuring a history related to heating of a substance to be measured, elapsed time, and the like by each of the above-described radiation luminescences, wherein the measurement is performed by constraining the transmission within a waveguide to be transmitted.

A second object of the present invention is to provide a substance container holding and moving means for controlling and moving a substance container holding a substance to be measured to an X-ray irradiation position XP and an excitation energy applying position. Exciting means for emitting luminescence light when excited in light tightness, measuring the intensity of the emitted luminescence light as an absolute value, luminescence light measuring means having a member for blocking noise due to external heat and light, A member for transmitting the luminescence light from the substance to be measured to the luminescence light measurement means, for blocking generation of noise due to heat and light from the excitation means and the outside, and a member for diffusing the luminescence light held by the member; A luminescent light guide means comprising a luminescent light guide member for transmitting without causing the X-ray to accumulate a radiation equivalent to a known accumulation year in the substance to be measured in a light-tight manner; A history of the measurement device of a measured substance by radiation luminescence, characterized in that it comprises an illumination device. Preferably, the means for measuring, as an absolute value, the intensity of the luminescence light having a member for blocking noise due to heat and light from the outside is a photomultiplier tube with a tank provided with a cooling means. It is a measurement device of the history of the substance to be measured by the radiation luminescence, more preferably, a member that shuts off heat and optical noise from the excitation means and the outside, and without diffusing the luminescence light held by the member The luminescent light guide means, which comprises a luminescent light guide member for transmission, has a luminescence light intake port and a light output port for transmitting the transmitted luminescence light to the luminescence light measurement means in a member that blocks noise due to heat and light. Characterized by having a luminescent light guide member buried except for It is an apparatus for measuring the history of constant substances, and more preferably, the member that blocks noise due to heat and light is a black elastic member, and the luminescent light guide member is a heat-resistant core-clad rod or fiber. The apparatus for measuring the history of a substance to be measured by each of the above-mentioned radiation luminescence, more preferably, means for thermally exciting the sample to be measured is concentrated to heating to 450 ° C. and rapid air cooling to room temperature after measurement. A ceramic heater configured such that the end faces of the thin plate-shaped ceramics capable of being provided are provided for heating the sample container to be measured, and the multi-stacked end faces are smaller than the bottom area of the sample container. The measurement device of the history of the substance to be measured by each of the radiation luminescence.

[0008] Further, a filter means for cutting the excitation energy from the excitation means is provided between the light emission port side of the luminescence light guide means and the light intake side of the luminescence measurement means. A device for measuring the history of a substance to be measured by each radiation luminescence, and a heat-resistant core-clad rod or fiber constituting a luminescence light guide member has a filter function of cutting excitation energy light from excitation means. The apparatus for measuring the history of a substance to be measured by each of the radiation luminescence.

[0009]

DETAILED DESCRIPTION OF THE INVENTION This will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes an X-ray irradiation position X
P, a substance-to-be-measured container holding / moving means for controlling (by a step programmed in the control device) to move to the excitation energy applying position EP, which has a turntable shape here, and has 16 substance to be measured (referred to as a sample). In some cases) can be simultaneously placed and measured. The number that can be simultaneously arranged and measured in the substance-to-be-measured container holding and moving means can be appropriately increased or decreased. The substance-to-be-measured container holding / moving means 1 is preferably arranged in an inert gas, for example, a nitrogen gas stream so that the substance to be measured is not subjected to thermal oxidation. Devices that are affected by light, such as a turntable, are light-tightly arranged in a box having an opening for X-ray irradiation and for transmitting luminescence from a substance to be measured.
The shape of the substance to be measured may be a particle shape or a tablet shape. At the excitation energy applying position EP, the substance to be measured container SC (also referred to as a sample container) containing the substance to be measured is measured by the heating means 2 composed of a cluster heater in order to thermally excite it. The material is heated intensively while floating from the substance container holding and moving means 1. As a result, the moving means is heated, so that "noise" (such as black body radiation) can be prevented from being applied to the red luminescence measuring means by black body radiation. It is preferable to provide a device (fan, not shown) for blowing cooling gas near the heating means so as to realize rapid cooling of the substance to be measured. Reference numeral 3 denotes a case where light, for example, a blue laser (semiconductor laser) is used as the excitation means. The irradiation energy is approximately 5 mW / cm ² per substance to be measured, and can be adjusted by changing the distance between the substance to be measured and the semiconductor laser holder and the value of the operating current.

The luminescent light emitted from the substance to be measured is embedded in a member 6 (for example, a member made of a heat-resistant black rubber material, neoprene (registered trademark), a heat-resistant silicon rubber, etc.) for blocking heat and optical noise. The luminescent light guide member LG (light guide means 4) is guided to the light intake of the luminescence measuring means 5. By using such a light guide member, the heat insulating effect, the handleability, and the light transmittance can be reduced as compared with the case where a conventional vacuum cell type quartz window having a high transmittance for light in the ultraviolet to infrared ranges is used. The transmission efficiency was remarkably improved (about 30 times or more). 7
Is an X-ray irradiator that irradiates a substance to be measured with a known amount of X-rays and accumulates a known amount of accumulated radiation. Although it is functionally an alternative to the conventional RI source, it is difficult to handle. From then it will be a remarkable improvement. As output, 10-50W
(Watts) may be small. The most improved apparatus of the present invention is a combination of each of the above-mentioned characteristic means and apparatuses. In particular, the use of a small X-ray generator as a means for accumulating a known amount of radiation in a sample, the luminescence, Light is guided to the luminescence light measuring means 5 by the luminescence light guide member LG buried in the member 6 that blocks heat and light noise, so that the influence of the heat on the measuring instrument can be removed. In addition, a remarkable effect can be obtained in that the inconvenience that the luminescence light when transmitting the luminescence light from the substance to be measured to the luminescence light measuring device is attenuated by diffusion or the like can be eliminated.

Further, in the apparatus according to the present invention, as means for thermally exciting the substance to be measured, the substance is concentrated to a temperature of 450 ° C. without protruding from the bottom area of the substance to be measured and quickly to room temperature after the measurement. For example, as the heating means 2, the end face of the thin plate-shaped ceramic is multiply stacked so as to be provided for heating the sample container to be measured, and the multiply stacked end face becomes smaller than the bottom area of the sample container. By using a ceramic heater (referred to as a cluster heater) configured as described above and combining with cooling by a fan, concentrated heating and rapid cooling of a substance to be measured can be performed. For example, a specific configuration of the ceramic heater is to stack four (32 W) plate heaters each having a capacity of 32 W (120 W), use the end surfaces of the heaters for heating, and further form a tip of the ceramic heater with a metal having good heat conductivity, such as a brass or silver plate The heating surface is made smaller than the container bottom area of the substance to be measured, and blackbody radiation is suppressed. The output is 100 ±
It is about 30 W, and the temperature can be raised at a constant speed up to 450 ° C. Further, a biotite-made brim-shaped material MB is attached (for example, by bonding) to the periphery of the container body SM of the substance to be measured (for example, by bonding) so that the black body radiation light from the heating member reaches the luminescence measuring means. Is preventing.

Reference numeral 8 denotes a device for controlling the measuring device.
Reference numeral 9 denotes a temperature control device, and reference numeral 10 denotes a device for controlling voltage and current of electroluminescence.

The member 6 for blocking heat and optical noise may be made of any material that has heat resistance and low thermal conductivity and does not transmit the measured luminescence light, and is used for forming a protective layer of a commercially available optical rod or optical fiber. It is possible to use a heat-resistant black material. The member that blocks heat and optical noise includes a light absorbing layer that prevents optical noise and a heat insulating layer that blocks heat.
It may have a layered structure. The luminescent light guide member LG preferably uses a multi-component glass that transmits near ultraviolet to near infrared. However, since the luminescence light to be measured only needs to be transmitted, the light transmittance of the material constituting the light guide member may be different between, for example, those measuring red luminescence and those measuring blue luminescence. Further, in order to prevent noise caused by the excitation means, noise in the noise wavelength region from the excitation means is cut off instead of the filter 11 (FIG. 1) disposed between the luminescence light guide member and the luminescence light measurement means. It can also have a filtering effect. The shape of the light guide may be a rod type or a fiber array type.
In addition, the arrangement of the light guide in the member 6 that blocks heat and optical noise can also be arranged in an array. Further, the arrangement of the luminescence light taking-in side and the taking-out side to the luminescence measuring means may be changed in relation to the structure of the luminescence detecting means (for example, an array structure).

The luminescence measuring means 5 having a member for shutting off external heat and optical noise includes cooling means,
For example, a photomultiplier tube with Peltier cooling means is used.
Examples of such materials include those having sensitivity from near ultraviolet to near infrared using a multi-alkali (composition of Na-K-Sb-Cs) as a photocathode (R-64, manufactured by Hamamatsu Photonics KK).
9) High sensitivity in near-ultraviolet to blue region using bi-alkali (Sb-Rb-Cs composition) (Hamamatsu Photonics Co., Ltd.)
A photomultiplier tube having a photocathode of R-585) can be used. To measure the absolute value means to measure as the number of photons (photon meter).

The measurement principle of the present invention will be described for the case of estimating the years of radiation accumulation. The horizontal axis in FIG. 2 indicates the passage of the year. The vertical axis indicates the accumulated radiation dose (emission intensity) unit is the integrated count (the number of photons), and correlates with the natural radiation accumulation years and the X-ray irradiation time. R-649 manufactured by Hamamatsu Photonics KK was used as the photomultiplier tube. Therefore, the luminescence intensity of the substance to be measured at the time of observation, and the luminescence intensity after irradiating a known amount of X-rays thereto, are measured, and from the relationship between the X-ray irradiation amount (corresponding to the irradiation time) and the intensity, By estimating the number of years of radiation accumulation of the luminescence intensity at the time of the measurement, it is possible to estimate the time when the accumulated radiation release event occurs, for example, the time of a volcanic eruption. In addition, unlike FIG. 2 described above, the amount of radiation exposure (eg, at a nuclear facility) due to the incident, and the amount of exposure to the substance to be measured (exposure history) that are irradiated with X-rays are estimated instead of natural accumulation. can do. FIG. 4 shows a standard calibration curve of the correlation between the X-ray irradiation dose and the intensity of red thermoluminescence.

[0016]

EXAMPLES Example 1 A white mineral originating in volcanic ash from Omachi, Nagano Prefecture was ground and treated with hydrofluoric acid (48%) at room temperature for 60 minutes. This treatment dissolves and removes feldspar. The insoluble portion was separated to obtain a white quartz powder sample (preferably further purified using a specific gravity ore separation method). This is placed in a dish-shaped container made of metal, for example, aluminum, as a substance to be measured, and set in a hole for holding a substance to be measured container of a turntable constituting the means for holding and moving the substance to be measured container shown in FIG.
As the heater, four 32 W plate heaters are laminated (120 heaters).
W) was prepared by covering a brass plate to which a temperature sensor was attached on the processed product. FIG. 5 shows 30 gamma radiation (5 Gy (gray), 1 Gy = 100 rad) with a known amount of gamma radiation and an X-ray generator 7 (50 watts) in the device of the invention.
The magnitude of red thermoluminescence after irradiation for 60 seconds, 90 seconds, and 120 seconds is shown. FIG. 4 shows a standard calibration curve of the correlation between the X-ray irradiation dose and the intensity of red thermoluminescence. FIG. 4 shows a standard calibration curve of the correlation between the X-ray irradiation dose and the red thermoluminescence intensity obtained from FIG. FIG. 6 shows an attenuation curve of photoexcited luminescence (0SL) in the 380 nm region obtained by irradiating the same substance to be measured with a blue LED (semiconductor laser, emission peak value is 470 nm). The characteristics of the decay curve decay exponentially, while increasing in proportion to the effect of naturally accumulated radiation on the quartz particles, so that the integrated photoexcited luminescence intensity within a certain time can be used to determine the thermoluminescence method (FIGS. 2 and 3). 4) Similarly, the history of the quartz particles can be obtained using the dose calibration curve. In order to prevent interference from feldspar coexisting with quartz particles, it is desirable to irradiate the quartz particles in advance with infrared rays for about 10 hours after separation to eliminate photoexcited luminescence derived from feldspar (R60 in FIG. 6).
Is a glass filter in the red region showing 50% transmittance at a wavelength of 600 nm, and can select and irradiate an infrared region with a pseudo-sun light source. ). By the way, in the case where a vacuum quartz window having a high transmittance for light from the ultraviolet region to the infrared region is conventionally used instead of the luminescence light transmission means, the transmission amount of the luminescence light is small. The luminescence curves corresponding to FIG. 5 and FIG. 6 by the line irradiation could not be created especially in the low radiation dose region.

Example 2 A disk-shaped flake sample (diameter 9.4 mm, 1 mm thick) was prepared from Imari porcelain Imari pieces from the Edo period, and the results of experiments for estimating the accumulated natural radiation dose and estimating the age are described. The measurement method is the same as the condition in Example 1 by repeating the processing of the substance to be measured, the measurement of red luminescence light, and the accumulation of a known amount of radiation by X-ray irradiation, to obtain a curve corresponding to FIG. 7) was drawn, and a 21 Gy accumulated natural radiation dose (accumulated temperature range of 260-310 ° C.) and a young age of 270 could be evaluated for the substance to be measured.

Example 3 Quartz particles were extracted and measured from the Jomon-style earthenware pieces obtained from the upper and lower layers sandwiching the known volcanic ash layer in the same manner as in Example 1, and corresponded to FIGS. 2 and 4. Figure 8 was drawn and the age was estimated by red luminescence. The age values of Jomon pottery pieces from the layers above and below the volcanic ash layer for 5000 years were evaluated in 3800 and 5700 +/- 1700 years, and showed results that were in harmony with the age values of the volcanic ash layer.

[0019]

As described above, by combining a small-sized X-ray apparatus and a thermal infrared luminescence light measuring apparatus, it is simpler and safer than one using a conventional RI-ray source. Further, it is possible to measure a substance to be measured having a thermal history only by using heat or photoexcited luminescence light. Further, by using the luminescent light guide member of the present invention, an excellent effect that it is possible to measure weaker luminescent light is provided.

[Brief description of the drawings]

FIG. 1 shows one embodiment of the luminescence measuring device of the present invention.

FIG. 2 is a diagram illustrating the principle of measurement according to the present invention.

Fig. 3 Metal container of the substance to be measured, fitted with a biotite brim

FIG. 4 Correlation between X-ray dose and red thermoluminescence

Fig. 5 Correlation between the characteristics of X-ray irradiation and thermally excited red luminescence of quartz in Omachi volcanic ore.

6 is a diagram showing attenuation characteristics of near-ultraviolet luminescence light by optical excitation (blue laser) of the substance to be measured in FIG. 5;

FIG. 7: Evaluation of natural accumulated dose using red luminescence (RTL) dose response curve [Measurement of a disk-shaped tablet sample from Imari porcelain pieces]

FIG. 8: Red thermoluminescence (RTL) emission curve (I) and irradiation dose response curve (II) of quartz particles extracted from Jomon pottery

[Explanation of symbols]

REFERENCE SIGNS LIST 1 substance-to-be-measured container holding and moving means 2 heating means (cluster heater) 3 light excitation means 4 luminescence light guide member 5 luminescence light measurement means 6 member for shutting off generation of noise due to heat and light 7
Radiation accumulation X-ray irradiation device 8 Luminescence measurement device control device 9 Thermal excitation power control device 10 Optical excitation power device 11 Optical filter SM Container main body MB Bomb made of biotite

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // G01N 21/62 G01N 21/62 A

Claims (10)

[Claims] 1. Excitation of stored radiation of a substance to be measured by external energy from an excitation means (2 or 3), and the intensity of near-ultraviolet to near-infrared luminescence emitted by the excitation is defined as an absolute value. X-ray irradiation for accumulating a known (equivalent to a storage year) radiation dose on the substance to be measured is followed by excitation with external energy by the excitation means and measurement of the intensity of the emitted luminescence. The irradiation dose is changed at least twice, and the accumulated radiation dose of the substance to be measured is determined based on the luminescence intensity from the substance to be measured and the change in the luminescence intensity after X-ray irradiation corresponding to the known accumulation years. A method for measuring the history of a substance to be measured by radioluminescence, which comprises calculating the number of years of storage. 2. The method according to claim 1, wherein the external energy from the excitation means is heat and / or visible light to near-infrared light. 3. The transmission of the excited luminescence emitted from the substance to be measured to the luminescence measuring means for measuring the intensity of the luminescence is held by a member that blocks noise due to external heat and light. The method for measuring the history of a substance to be measured by radiation luminescence according to claim 1 or 2, wherein the luminescence light is constrained and transmitted in a waveguide for transmitting the luminescence light. 4. A substance to be measured container S for holding a substance to be measured.
A substance container holding and moving means 1 for controlling and moving C to an X-ray irradiation position XP and an excitation energy applying position; an excitation means (2, 3) for exciting the substance to be measured in light tightness and emitting luminescence light ), A luminescence light measuring means 5 having a member for blocking the noise due to heat and light from the outside, which measures the intensity of the emitted luminescence light as an absolute value, and converts the luminescence light from the substance to be measured to the luminescence. A member 6 for transmitting the light to the light measuring means, blocking the generation of noise due to heat and light from the excitation means and the outside, and a luminescent light guide member 4 for transmitting the luminescent light held by the member without diffusing. A luminescent light guide means LG, and an X-ray irradiating device 7 for accumulating a radiation equivalent to a known accumulation year in light-tight on the substance to be measured. The history of the measuring device of the substance to be measured by the luminescence. 5. A photomultiplier tube with a cooling means provided with a means for measuring the intensity of luminescence light having a member for blocking noise due to heat and light from the outside as an absolute value. The apparatus for measuring the history of a substance to be measured by radiation luminescence according to claim 4. 6. A luminescence light guide means comprising: an excitation means, a member for blocking heat and light noise from the outside, and a luminescence light guide member for transmitting the luminescence light held by said member without diffusing. Having a luminescence light guide member buried in a member that blocks noise due to heat and light, except for a luminescence light intake port and a light extraction port that transmits the transmitted luminescence light to the luminescence light measurement means. The apparatus for measuring the history of a substance to be measured by radiation luminescence according to claim 4 or 5, wherein: 7. The member for blocking noise due to heat and light is a black elastic member, and the luminescent light guide member is a heat-resistant core-clad rod or fiber. 7. An apparatus for measuring the history of a substance to be measured by radioluminescence according to 6. 8. An end face of a thin plate-shaped ceramic capable of heating to 450 ° C. and rapidly cooling to room temperature after measurement by concentrating means for thermally exciting the sample to be measured is provided for heating the sample container to be measured. 8. A ceramic heater according to claim 4, 5, 6 or 7, wherein the ceramic heater is a multi-layered ceramic heater having a multi-layered end face smaller than the bottom area of the sample container. Measurement device for the history of the substance to be measured. 9. A filter means for cutting excitation energy from the excitation means between the light emission port side of the luminescence light guide means and the light intake side of the luminescence measurement means. Item 4, 5, 6, 7 or 8
3. A measuring device for a history of a substance to be measured by radioluminescence described in 4. 10. The heat-resistant core-cladding rod or fiber constituting the luminescence light guide member has a filter function of cutting off excitation energy light from the excitation means. For measuring the history of the substance to be measured by means of radioluminescence.