JP2021156583A - Optical fiber type radiation monitor and application method thereof - Google Patents

Abstract

To provide an optical fiber type radiation monitor that suppresses attenuation of the intensity of light transmitted to a photoelectric converter, does not reduce monitoring sensitivity, and measures a radiation dose with high accuracy.SOLUTION: The optical fiber type radiation monitor comprises: a sensor 10 that generates photons depending on a radiation dose incident on the sensor; an optical fiber that transmits photons; a photoelectric converter that converts photons into electrical signals; a counting device that counts the electric signal converted by the photoelectric converter and outputs a count value of the electric signal; a light emitting unit that irradiates the sensor with laser light via the optical fiber; a light emission timing control unit that controls the laser light irradiation timing of the laser light emitted by the light emitting unit and outputs a laser light irradiation timing signal; a correction device that creates correction data based on the laser light irradiation timing signal and the count value of the electric signal, performs correction processing based on the count value of the electric signal and the correction data, and calculates the radiation dose or radiation dose rate; and a display device that displays the radiation dose or the radiation dose rate.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical fiber radiation monitor and a method of using the same.

Radiation monitors are indispensable measuring devices in applications such as nuclear power plants, medical radiological examinations and radiation therapy. In these applications, ionization chambers with good stability and reproducibility are widely used for measuring radiation dose.

In particular, when measuring the amount of radiation in a patient during radiotherapy, it is important that the sensor is minimally invasive, and a sensor that does not require miniaturization of the sensor or application of voltage is important. Further, even when measuring the radiation amount in the harsh environment of a nuclear power plant, it is important to have a sensor that does not require miniaturization of the sensor or application of voltage due to restrictions on the measurement location.

In recent years, instead of ionization chambers, semiconductor detectors, which are relatively easy to miniaturize, have been used for measuring radiation levels. However, even if it is a semiconductor detector, there is a limit to miniaturization including the signal processing system, and the semiconductor detector needs to apply a voltage.

Therefore, an optical fiber type radiation monitor has been developed in which a scintillator element is used as a sensor, photons generated from the scintillator element are transmitted by an optical fiber, and the radiation amount is measured remotely. In the optical fiber type radiation monitor, the sensor can be miniaturized and it is not necessary to apply a voltage to the sensor. As described above, the optical fiber type radiation monitor is also suitable for measuring the radiation amount in the patient's body at the time of radiotherapy or for measuring the radiation amount in the harsh environment of the nuclear power plant.

On the other hand, when using an optical fiber type radiation monitor to measure the radiation amount inside the patient during radiotherapy or when measuring the radiation amount in the harsh environment of a nuclear power plant, high-precision measurement is required. At the same time, correction is required in consideration of deterioration of the sensor, and periodic calibration is required.

As a background technique in this technical field, there is Japanese Patent Application Laid-Open No. 2018-36204 (Patent Document 1). Patent Document 1 describes a radiation detection unit having a radiation detection element that generates light having a predetermined wavelength, a light emitting unit that generates light having a wavelength different from the predetermined wavelength, and a light emitting unit that transmits light having a predetermined wavelength. A wavelength selection unit that blocks light with a wavelength different from the light of the same wavelength, an optical fiber that transmits light, an optical detection unit that converts light transmitted through the wavelength selection unit into an electric pulse, and an electric pulse count rate A radiation monitor having a counting device for counting and an analysis display device for determining at least the presence or absence of deterioration of the light emitting unit based on the counting rate and the light intensity of the light emitting unit is described (see summary).

Japanese Unexamined Patent Publication No. 2018-36204

Patent Document 1 describes a radiation detection unit that generates light having a predetermined wavelength, a light emitting unit that generates light having a wavelength different from that of a predetermined wavelength, and a light emitting unit that transmits light having a predetermined wavelength and having a predetermined wavelength. An optical fiber type radiation monitor having a wavelength selection unit (optical filter) that blocks light of different wavelengths is described. That is, in the optical fiber type radiation monitor described in Patent Document 1, an optical filter is installed in the light transmission path.

However, Patent Document 1 describes the possibility that by installing an optical filter in an optical transmission line, the intensity of light transmitted to the optical detection unit (photoelectric converter) is attenuated and the monitoring sensitivity is reduced. Not listed.

Therefore, the present invention provides an optical fiber type radiation monitor and a usage method that suppresses attenuation of the intensity of light transmitted to the photoelectric converter, does not reduce the monitoring sensitivity, and measures the radiation amount with high accuracy. do.

In order to solve the above-mentioned problems, in the optical fiber type radiation monitor of the present invention, a sensor that generates photons depending on the amount of incident radiation, an optical fiber that transmits photons generated by the sensor, and an optical fiber transmit the signal. The photoelectric converter that converts the photons to be converted into an electric signal, the counting device that counts the electric signal converted by the photoelectric converter and outputs the counted value of the electric signal, and the sensor are irradiated with laser light via an optical fiber. The light emitting unit, the light emitting timing control unit that controls the laser light irradiation timing of the laser light emitted by the light emitting unit, and outputs the laser light irradiation timing signal, and the light emitting timing control unit that receives the laser light irradiation timing signal output by the light emitting timing control unit. When receiving the count value of the electric signal output by the counting device, creating correction data based on the laser beam irradiation timing signal and the count value of the electric signal, and measuring the radiation amount, the count value of the electric signal is used. It is characterized by having a correction device that performs correction processing based on the correction data and calculates a radiation amount or a dose rate of radiation, and a display device that displays the radiation amount or the dose rate of radiation.

Further, in order to solve the above-mentioned problems, the method of using the optical fiber type radiation monitor of the present invention includes a generation step of generating photons depending on the radiation amount of the incident radiation in the sensor and a sensor in the optical fiber. A transmission process for transmitting photons generated by A counting step that outputs the count value of an electric signal, an irradiation step that irradiates a sensor with laser light via an optical fiber at the light emitting unit, and a laser of laser light that the light emitting unit irradiates at the light emitting timing control unit. When the light irradiation timing is controlled and the laser light irradiation timing signal is output, and the correction device receives the laser light irradiation timing signal output by the light emission timing control unit and the sensor light emission is attenuated after the laser light is irradiated. The creation process of creating correction data based on the number of photons to be counted, and when measuring the radiation dose, the correction device performs correction processing based on the count value of the electric signal and the correction data. It is characterized by having a calculation step of calculating a radiation amount or a dose rate of radiation.

According to the present invention, there is provided an optical fiber type radiation monitor and a method of using it, which suppresses attenuation of the intensity of light transmitted to a photoelectric converter, does not reduce monitoring sensitivity, and measures radiation amount with high accuracy. can do.

Issues, configurations, and effects other than those described above will be clarified by the explanation of the examples below.

It is explanatory drawing explaining the structure of the radiation monitor 1 described in Example 1. FIG. It is a conceptual diagram explaining the generation process of the photon by the radiation incident on the sensor 10 described in Example 1. FIG. It is explanatory drawing explaining the relationship between the dose rate of radiation and the photon count rate described in Example 1. FIG. It is explanatory drawing explaining the relationship between the photon count rate and the electric pulse count rate described in Example 1. FIG. It is explanatory drawing explaining the relationship between the intensity of the laser beam and the number of photons described in Example 1. FIG. It is a time chart explaining the laser light irradiation timing, the sensor light emission and the attenuation measurement which describe in Example 1. FIG. It is explanatory drawing explaining the structure of the radiation monitor 2 described in Example 2. FIG.

Hereinafter, examples of the present invention will be described with reference to the drawings. The substantially same or similar configurations are designated by the same reference numerals, and when the explanations are duplicated, the explanations may be omitted.

First, the configuration of the radiation monitor 1 described in the first embodiment will be described.

FIG. 1 is an explanatory diagram illustrating the configuration of the radiation monitor 1 described in the first embodiment.

The radiation monitor 1 described in the first embodiment is an optical fiber type radiation monitor (hereinafter referred to as “radiation monitor”).

The radiation monitor 1 includes a sensor 10, an optical fiber 20, a photoelectric converter 30, a counting device 40, a light emitting unit 50, a light emitting timing control unit 60, a correction device 70, and a display device 80.

The sensor 10 has a radiation emitting element that generates photons (hereinafter referred to as "photons") that depend on (correspond to) the amount of incident radiation. The radiation emitting element generates photons when radiation is incident on it. That is, when radiation is incident, the sensor 10 generates (emissions or fluorescence) photons depending on the radiation amount of the incident radiation.

Then, the radiation amount of the radiation incident on the sensor 10 and the number of photons generated by the sensor 10 (the number of photons) have linearity. That is, the dose rate of the radiation incident on the sensor 10 and the number of photons per unit time generated by the sensor 10 (hereinafter referred to as "photon counting rate") have linearity.

The radiation emitting material used for the radiation emitting element has, for example, a material such as transparent yttrium aluminum garnet (YAG) as a base material, and ytterbium, neodymium, cerium, praseodymium and the like as additives to this material. Has at least one or more rare earth elements.

As described above, when the radiation emitting element has at least one kind of rare earth element, the linearity between the dose rate of the radiation incident on the sensor 10 and the photon counting rate can be further improved. Then, even when radiation having a high dose rate is incident on the radiation monitor 1, the linearity between the radiation dose rate and the photon counting rate can be maintained, and the radiation dose rate can be accurately measured.

Further, the radiation emitting material represented by the general formula (1) may be used for the radiation emitting element.

ATaO ₄ : B ... General formula (1)
In the general formula (1), A and B are rare earth elements having 4f-4f electron transitions, and at least one of Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Tb. It is a rare earth element.

The mass of the additive B added to the radiation emitting material ^{is preferably 1 × 10 -3} to 30% by mass with respect to the total mass of the radiation emitting material. Thereby, the light emission intensity of the sensor 10 can be improved.

In the radiation emitting material represented by the general formula (1), the high-density base material ATaO ₄ and the additive B have a rare earth element having a 4f-4f electron transition, so that the base material ATaO ₄ is imparted by radiation. The energy to be used is used for the excitation energy of the additive B with high efficiency. Thereby, the sensitivity of the sensor 10 can be improved.

The optical fiber 20 connects the sensor 10 and the photoelectric converter 30. The optical fiber 20 transmits the photons generated by the sensor 10 to the photoelectric converter 30. The optical fiber 20 is made of, for example, quartz or plastic.

The photoelectric converter 30 is connected to the sensor 10 via an optical fiber 20. The photoelectric converter 30 converts the transmitted photons into an electric signal (hereinafter referred to as "electric pulse"). The photoelectric converter 30 converts each photon transmitted by the optical fiber 20 into an electric pulse one by one. Then, the photoelectric converter 30 transmits one electric pulse to one photon.

That is, the number of photons generated by the sensor 10 and the number of electric pulses transmitted by the photoelectric converter 30 have linearity. The photon counting rate and the number of electric pulses per unit time transmitted by the photoelectric converter 30 (hereinafter referred to as "electric pulse counting rate") have linearity.

For the photoelectric converter 30, for example, a photomultiplier tube or an avalanche photodiode is used. By using a photomultiplier tube, an avalanche photodiode, or the like in the photoelectric converter 30, the transmitted photons can be converted into amplified electric pulses.

The counting device 40 is connected to the photoelectric converter 30 via a signal line. The counting device 40 counts the transmitted electric pulses. That is, the counting device 40 counts the transmitted electric pulses one by one, and outputs the counting value (the number of electric pulses) of the electric pulses counted by the counting device 40.

When measuring the radiation amount, a sensor 10, an optical fiber 20, a photoelectric converter 30, and a counting device 40 are used, and a preset one-to-one corresponding electric pulse counting value (or electric pulse counting) is used. The radiation amount is measured based on the relationship between the rate) and the radiation amount (or the dose rate of radiation).

On the other hand, when measuring the radiation amount, it is necessary to correct (correction processing) the count value (or the electric pulse count rate) of the electric pulse in consideration of the deterioration of the sensor 10.

In the case of correction, the sensor 10, the optical fiber 20, the photoelectric converter 30, the counting device 40, the light emitting unit 50, the light emitting timing control unit 60, and the correction device 70 are used.

The light emitting unit 50 is, for example, a laser light generator that generates laser light, and is connected to the sensor 10 via an optical fiber 20. Then, the light emitting unit 50 irradiates the sensor 10 with a laser beam via the optical fiber 20. That is, the laser light generated by the light emitting unit 50 is irradiated to the sensor 10, and the sensor 10 is irradiated with the laser light to generate photons depending on the irradiated laser light.

The intensity of the laser beam applied to the sensor 10 and the number of photons have linearity. That is, the intensity of the laser beam applied to the sensor 10 and the photon counting rate have linearity.

Further, the energy of the laser beam needs to be higher than the energy of the photons generated by the sensor 10. That is, the wavelength of the laser beam needs to be shorter than the wavelength of the photons generated by the sensor 10.

The light emitting timing control unit 60 is connected to the light emitting unit 50 via a signal line. The light emitting timing control unit 60 controls the light emitting timing (laser light irradiation timing) in which the light emitting unit 50 generates the laser light, that is, the laser light irradiation timing of the laser light irradiated by the light emitting unit 50, and the light emitting timing signal (laser light). Irradiation timing signal) is output.

The correction device 70 is connected to the light emission timing control unit 60 and the counting device 40 via a signal line. The correction device 70 receives the laser light irradiation timing signal output by the light emission timing control unit 60 from the light emission timing control unit 60, receives the count value of the electric pulse output by the counting device 40 from the counting device 40, and irradiates the laser light. Correction data is created based on the timing and the count value of the electric pulse.

Further, the correction device 70 stores the correction data to be created, and when the correction data to be stored is used to measure the radiation amount, the count value (or electricity) of the electric pulse is taken into consideration in consideration of the deterioration of the sensor 10. Pulse count rate) is corrected.

Further, when measuring the radiation amount, the correction device 70 performs a correction process based on the count value of the electric pulse and the correction data, and calculates the radiation amount (or the radiation dose rate).

The correction device 70 is not particularly limited as long as it can perform arithmetic processing, and a personal computer or the like is used as the correction device 70.

The display device 80 displays the radiation amount (or the dose rate of radiation). Further, the display device 10 displays an abnormality of the sensor 10 or the like.

Next, the process of generating photons due to the radiation incident on the sensor 10 described in Example 1 will be described.

FIG. 2 is a conceptual diagram illustrating a process of photon generation due to radiation incident on the sensor 10 described in the first embodiment.

When the radiation r is incident on the sensor 10, the energy of the radiation r causes the electrons in the ground state (energy level L1) in the sensor 10 to transition to the excited state (energy level L3) having a high energy level (energy level L3). In FIG. 2, see arrow a1). Then, the electrons in the excited state with a high energy level (energy level L3) transition to the excited state with a low energy level (energy level L2) (see arrow b1 in FIG. 2). The sensor 10 generates a photon (p) having an energy corresponding to the difference in energy between the energy level L3 and the energy level L2.

Further, when the sensor 10 is irradiated with the laser light generated by the light emitting unit 50, the electrons of the energy level L1 in the sensor 10 transition to the energy level L3 due to the energy of the laser light (arrows in FIG. 2). See a1). Then, the electron at the energy level L3 transitions to the energy level L2 (see arrow b1 in FIG. 2). The sensor 10 generates a photon (p) having an energy corresponding to the difference in energy between the energy level L3 and the energy level L2.

Next, the relationship between the radiation dose rate and the photon counting rate described in Example 1 will be described.

FIG. 3A is an explanatory diagram illustrating the relationship between the radiation dose rate and the photon counting rate described in Example 1.

As shown in FIG. 3A, the radiation dose rate and the photon counting rate have a linearity (proportional relationship).

Next, the relationship between the photon counting rate and the electric pulse counting rate described in Example 1 will be described.

FIG. 3B is an explanatory diagram illustrating the relationship between the photon counting rate and the electric pulse counting rate described in the first embodiment.

As shown in FIG. 3B, the photon count rate and the electric pulse count rate have a linearity (proportional relationship).

As described above, there is a one-to-pair correspondence between the radiation dose rate and the photon counting rate, and there is a one-to-pair correspondence between the photon counting rate and the electric pulse counting rate. That is, there is a one-to-pair correspondence between the radiation dose rate and the electric pulse count rate. Thereby, the electric pulse count rate can be converted into the radiation dose rate.

When measuring the radiation amount, the electric pulse counting rate is based on the relationship between the radiation dose rate and the photon counting rate (see FIG. 3A) and the relationship between the photon counting rate and the electric pulse counting rate (see FIG. 3B). The relationship between the radiation dose rate and the radiation dose rate is obtained, and the radiation dose is measured based on the relationship between the preset one-to-one electric pulse count rate and the radiation dose rate.

Next, the relationship between the intensity of the laser beam described in Example 1 and the number of photons will be described.

FIG. 3C is an explanatory diagram illustrating the relationship between the intensity of the laser beam described in Example 1 and the number of photons.

As shown in FIG. 3C, the intensity of the laser beam and the number of photons have a linearity (proportional relationship).

When the electric pulse count rate is corrected in consideration of the deterioration of the sensor 10, the following steps (1) to (4) are executed.

(1) First, the sensor 10 without deterioration is irradiated with a laser beam of a predetermined intensity in advance, the number of photons is measured, and the relationship between the intensity of the laser beam and the number of photons is grasped. At this time, the proportional relationship (a) can be grasped by irradiating at least two intensity laser beams (see a in FIG. 3C). Then, this number of photons is converted into a photon count rate.

The proportional relationship (a) is similar to the relationship between the radiation dose rate and the photon counting rate in the sensor 10 without deterioration. Here, the “sensor 10 without deterioration” means the initial state of the sensor 10.

(2) Next, the sensor 10 before measuring the radiation amount is irradiated with a laser beam of a predetermined intensity, the number of photons is measured, and the relationship between the intensity of the laser beam and the number of photons is grasped. At this time, the proportional relationship (b) can be grasped by irradiating at least two intensity laser beams (see b in FIG. 3C). Then, this number of photons is converted into a photon count rate.

(3) Next, the proportional relationship (a) and the proportional relationship (b) are compared. Due to the deterioration of the sensor 10, a difference occurs in the slope (proportional constant) between the proportional relationship (a) and the proportional relationship (b). Similarly, when the number of photons is converted into the photon count rate, a difference occurs in the gradient of the photon count rate with respect to the intensity of the laser beam (hereinafter referred to as “the gradient of the photon count rate”).

That is, the deterioration of the sensor 10 can be grasped by the sensor 10 before measuring the radiation amount as the difference in the slope of the photon count rate.

(4) Finally, the electric pulse count rate is corrected based on the difference in the slope of the photon count rate. The correction data is the difference in the slope of the photon counting rate or the difference in the slope of the electric pulse counting rate converted from the difference in the slope of the photon counting rate.

Then, when measuring the radiation amount, for example, the correction data is integrated with the photon counting rate converted from the measured radiation dose rate, and the electric pulse counting rate is corrected. This makes it possible to measure the radiation amount with high accuracy.

Next, the laser light irradiation timing, the sensor light emission, and the attenuation measurement described in the first embodiment will be described.

FIG. 4 is a time chart illustrating the laser light irradiation timing, sensor light emission, and attenuation measurement described in the first embodiment.

The time chart shown in FIG. 4 shows the laser beam irradiation timing of the laser beam generated by the light emitting unit 50, the sensor emission in which the sensor 10 generates photons when the laser beam is irradiated, and the attenuation controlled by the correction device 70. It shows the relationship with the measurement.

The laser light is irradiated to the sensor 10 in a pulse shape (for example, a pulse width of 1 μs) and periodically (for example, at intervals of several ms) (laser light irradiation timing).

The sensor 10 generates photons when irradiated with laser light (sensor light emission). The number of photons generated by the sensor 10 peaks during irradiation with laser light and attenuates after irradiation with laser light (immediately after light emission). That is, the sensor 10 continues to emit light even after the irradiation of the laser beam. Then, for example, the emission lifetime (fluorescence lifetime) of the sensor 10 is preferably 1 μs or more, and when Nd (neodymium): YAG is used for the radiation emitting element, it is 230 μs.

The correction device 70 counts the number of photons when the sensor emission is attenuated after irradiation with the laser beam (attenuation measurement). By counting the number of photons when the sensor emission is attenuated, the number of photons can be accurately measured without being affected by the reflection of the laser beam, that is, directly affected by the laser beam. Then, the radiation amount can be measured with high accuracy.

In this way, the correction device 70 receives the laser beam irradiation timing signal from the light emission timing control unit 60, receives the count value of the electric pulse from the counting device 40, counts the number of photons at the time of attenuation of the sensor light emission, and obtains the correction data. create. That is, when creating the correction data, the radiation amount can be measured with high accuracy by removing the laser beam or the like that becomes noise and measuring only the sensor emission.

Here, the noise generated by irradiating the laser light is the main wavelength component of the laser light itself, the laser light other than the main wavelength component such as the harmonic component, and the optical fiber 20 due to the laser light being irradiated. It is possible that the light emitted from the laser. An optical fiber type radiation monitor in which an optical filter is installed in an optical transmission path uses a difference in wavelength to remove noise, so that the laser light itself can be removed, but the harmonics of the laser light can be removed. It may not be possible to remove the components and the light emitted from the optical fiber 20.

According to the first embodiment, such noise that could not be removed in the past and that is generated by irradiating the laser beam can be removed and can be corrected with high accuracy.

The correction data can be created online and / or offline.

Further, the timing (measurement timing) for the correction device 70 to count the number of photons at the time of attenuation of the sensor light emission after irradiation with the laser beam is, for example, several ms. The measurement timing is shorter than the laser light irradiation timing interval and longer than the light emission life of the sensor 10. This makes it possible to accurately measure the number of photons.

That is, the measurement timing is a period for measuring the number of photons for creating correction data (correction data collection period).

The correction device 70 measures the number of photons in a preset correction data acquisition period based on the laser beam irradiation timing signal and the pulse width.

As described above, the radiation monitor 1 described in the first embodiment has the following constituent requirements.
-Sensor 10 that generates photons that depend on the amount of incident radiation (generation process)
-The optical fiber 20 that transmits the photons generated by the sensor 10 (transmission process)
・ Photon converter 30 that converts photons transmitted by the optical fiber 20 into electric pulses (conversion step)
-Counting device 40 that counts the electric pulses converted by the photoelectric converter 30 and outputs the counted value of the electric pulses (counting process).
-The light emitting unit 50 that irradiates the sensor 10 with laser light via the optical fiber 20 (irradiation step).
-The laser light irradiation timing of the laser light emitted by the light emitting unit 50 is controlled, and the laser light irradiation timing signal is output (control step). The light emitting timing control unit 60.
-Receives the laser light irradiation timing signal output by the light emission timing control unit 60, receives the count value of the electric pulse output by the counting device 40, and corrects data based on the laser light irradiation timing signal and the count value of the electric pulse. Creation (creation process) Correction device 70
-Display device 80 that displays the radiation amount (or radiation dose rate) (display process)
Then, when measuring the radiation amount, the correction device 70 corrects the electric pulse count rate based on the photon count rate converted from the measured radiation dose rate and the correction data (correction step).

Further, when the correction device 70 creates the correction data, the correction device 70 creates the correction data based on the number of photons counted when the sensor light emission is attenuated after the irradiation of the laser beam (creation step).

Further, when measuring the radiation amount, the correction device 70 performs a correction process based on the count value of the electric pulse and the correction data, and calculates the radiation amount (or the radiation dose rate) (calculation step). ).

As described above, according to the first embodiment, the sensor 10 used for the radiation monitor 1 can be miniaturized, and it is not necessary to apply a voltage to the sensor 10.

Further, according to the first embodiment, the radiation amount can be measured easily and accurately by using the correction data, considering the time-dependent change in the deterioration of the sensor 10, and correcting the electric pulse count rate. ..

Further, according to the first embodiment, the attenuation of the intensity of the light transmitted to the photoelectric converter 30 is suppressed without being affected by the reflection of the laser light, the monitoring sensitivity is not lowered, and the number of photons is increased. It can be measured accurately, and the radiation dose can be measured with high accuracy.

Further, according to the first embodiment, the noise generated by irradiating the laser beam, which could not be removed in the past, can be removed, can be corrected with high accuracy, and radiation can be performed with high accuracy. The amount can be measured.

Further, according to the first embodiment, even when the radiation amount in the patient's body at the time of radiotherapy is measured, or when the radiation amount is measured in a harsh environment of a nuclear power plant or in a narrow area, the deterioration of the sensor 10 is caused. In consideration, it can be preferably used.

Then, according to the first embodiment, since the sensitivity of the radiation monitor 1 is improved, it can be used in a low dose field such as an area monitor of a medical institution or a research institution, and the applicable range is greatly expanded.

Next, the configuration of the radiation monitor 2 described in the second embodiment will be described.

FIG. 5 is an explanatory diagram illustrating the configuration of the radiation monitor 2 described in the second embodiment.

The radiation monitor 2 described in the second embodiment is different from the radiation monitor 1 described in the first embodiment in that it has a shutter 90.

The shutter 90 is connected to the sensor 10 via an optical fiber 20. Further, the shutter 90 is connected to the photoelectric converter 30 via the optical fiber 20. That is, the shutter 90 is installed in the photon transmission line in front of the photoelectric converter 30. The shutter 90 opens and closes to allow the photons generated by the sensor 10 to pass through, or to block the photons generated by the sensor 10 (opening and closing step).

Further, the shutter 90 is connected to the light emission timing control unit 60 via a signal line. The light emission timing control unit 60 controls the opening / closing timing of the shutter 90. The light emitting timing control unit 60 controls the laser light irradiation timing of the laser light emitted by the light emitting unit 50, and also controls the opening / closing timing of the shutter 90. That is, the light emitting timing control unit 60 controls the shutter 90 and the light emitting unit 50 in synchronization. The light emission timing control unit 60 controls the shutter 90 to open at the same time when the irradiation of the laser beam is completed.

The shutter 90 opens under the control of the light emission timing control unit 60 during the correction data acquisition period, and transmits photons to the photoelectric converter 30. Also when measuring the radiation amount, the shutter 90 opens and the photons pass through (measurement step). Then, the correction data is created in the same manner as in the first embodiment.

As described above, the radiation monitor 2 described in the second embodiment is installed in front of the photoelectric converter 30 in addition to the radiation monitor 1 described in the first embodiment, and the laser light irradiation timing signal output by the light emission timing control unit 60 is output. Has a shutter 90 that opens and closes the photon transmission path where the sensor 10 is generated. The shutter 90 opens when the sensor light emission is attenuated after the laser light is irradiated.

Then, the correction device 70 receives the count value of the electric pulse output by the counting device 40, and creates correction data based on the count value of the electric pulse (creation step). When creating correction data, the correction device 70 creates correction data based on the number of photons counted when the shutter 90 is open (creation step). Further, when measuring the radiation amount, the correction device 70 performs a correction process based on the count value of the electric pulse and the correction data, and calculates the radiation amount (or the radiation dose rate) (calculation step). ).

That is, when creating correction data, the shutter 90 closes when the sensor emits light, opens when the sensor emission is attenuated after irradiation with the laser light, removes the laser light which becomes noise, and measures only the sensor emission. The amount of radiation can be measured with high accuracy.

As a result, the number of photons can be accurately measured without being affected by the reflection of the laser beam, that is, without being directly affected by the laser beam. Then, the radiation amount can be measured with high accuracy.

Regarding other configurations and functions of each configuration, the radiation monitor 2 described in the second embodiment is basically the same as the radiation monitor 1 described in the first embodiment. Further, in Example 2, the same effect as in Example 1 can be obtained.

Further, in the second embodiment, the light emitting timing control unit 60 controls the shutter 90 and the light emitting unit 50 in synchronization, so that the correction device 70 does not need to control the correction data acquisition period.

The present invention is not limited to the above-described examples, and includes various modifications. For example, the above-described embodiment has been specifically described in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations.

It is also possible to replace a part of the configuration of one embodiment with a part of the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete a part of the configuration of each embodiment, add a part of the other configuration, and replace it with a part of the other configuration.

1, 2 ... Radiation monitor 10 ... Sensor 20 ... Optical fiber 30 ... Photoelectric converter 40 ... Counting device 50 ... Light emitting unit 60 ... Light emitting timing control unit 70 ... Correction device 80 ... Display device 90 ... Shutter

Claims (9)

A sensor that generates photons that depend on the amount of incident radiation,
An optical fiber that transmits photons generated by the sensor,
A photoelectric converter that converts photons transmitted by the optical fiber into electrical signals, and
A counting device that counts the electric signal converted by the photoelectric converter and outputs the counted value of the electric signal.
A light emitting unit that irradiates the sensor with laser light via the optical fiber,
A light emission timing control unit that controls the laser light irradiation timing of the laser light emitted by the light emitting unit and outputs a laser light irradiation timing signal.
The laser light irradiation timing signal output by the light emission timing control unit is received, the count value of the electric signal output by the counting device is received, and correction is made based on the laser light irradiation timing signal and the count value of the electric signal. When data is created and the radiation amount is measured, a correction device that performs correction processing based on the count value of the electric signal and the correction data and calculates the radiation amount or the dose rate of radiation, and a correction device.
A display device that displays the radiation amount or the dose rate of the radiation,
An optical fiber type radiation monitor characterized by having. The optical fiber type radiation monitor according to claim 1.
The sensor is an optical fiber radiation monitor characterized in that transparent yttrium aluminum garnet is used as a base material and at least one rare earth element such as ytterbium, neodymium, cerium, and praseodymium is used as an additive. .. The optical fiber type radiation monitor according to claim 1.
The sensor is characterized by being ATaO ₄ : B (A and B are at least one rare earth element of Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Tb). Fiber optic radiation monitor. The optical fiber type radiation monitor according to claim 1 or 3.
The sensor is an optical fiber type radiation monitor characterized by having a fluorescence lifetime of 1 μs or more. The optical fiber type radiation monitor according to claim 1 or 4.
When creating the correction data, the correction device is an optical fiber type that creates the correction data based on the number of photons counted when the sensor emission is attenuated after irradiation with the laser beam. Radiation monitor. A sensor that generates photons that depend on the amount of incident radiation,
An optical fiber that transmits photons generated by the sensor,
A photoelectric converter that converts photons transmitted by the optical fiber into electrical signals, and
A counting device that counts the electric signal converted by the photoelectric converter and outputs the counted value of the electric signal.
A light emitting unit that irradiates the sensor with laser light via the optical fiber,
A light emission timing control unit that controls the laser light irradiation timing of the laser light emitted by the light emitting unit and outputs a laser light irradiation timing signal.
A shutter installed in front of the photoelectric converter, which receives a laser beam irradiation timing signal output by the light emission timing control unit and opens and closes a photon transmission path generated by the sensor.
When receiving the count value of the electric signal output by the counting device, creating correction data based on the count value of the electric signal, and measuring the radiation amount, the count value of the electric signal and the correction data A correction device that performs correction processing based on the above and calculates the radiation amount or radiation dose rate, and
A display device that displays the radiation amount or the dose rate of the radiation,
An optical fiber type radiation monitor characterized by having. The optical fiber type radiation monitor according to claim 6.
The shutter is an optical fiber type radiation monitor that opens when the sensor emission is attenuated after irradiation with laser light. The optical fiber type radiation monitor according to claim 7.
When creating the correction data, the correction device is an optical fiber type radiation monitor that creates the correction data based on the number of photons counted when the shutter is open. A generation process that generates photons that depend on the amount of incident radiation at the sensor,
A transmission process for transmitting photons generated by the sensor on an optical fiber, and
A conversion step of converting photons transmitted by the optical fiber into an electric signal with a photoelectric converter, and
A counting step of counting the electric signal converted by the photoelectric converter and outputting the counted value of the electric signal by the counting device.
An irradiation step of irradiating the sensor with laser light via the optical fiber at the light emitting unit,
A control step in which the light emitting timing control unit controls the laser light irradiation timing of the laser light emitted by the light emitting unit and outputs a laser light irradiation timing signal.
The correction device receives the laser light irradiation timing signal output by the light emission timing control unit, and creates correction data based on the number of photons counted when the sensor light emission is attenuated after the laser light is irradiated.
When measuring the radiation amount, the correction device performs a correction process based on the count value of the electric signal and the correction data, and calculates the radiation amount or the radiation dose rate.
How to use an optical fiber radiation monitor, characterized by having.

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