JP7186192B2 - Fiber optic radiation monitor and method of use - Google Patents

Description

The present invention relates to fiber optic radiation monitors and methods of use thereof.

A radiation monitor is an essential measuring device in applications such as nuclear power plants, medical radiological examinations, and radiotherapy. In these applications, ionization chambers are widely used for measuring radiation dose because of their good stability and reproducibility.

In particular, when measuring the radiation dose inside a patient's body during radiotherapy, it is important to be minimally invasive, and sensors that do not need to be miniaturized and that do not require the application of voltage are important. Also, when measuring the radiation dose in the harsh environment of a nuclear power plant, it is important to have a sensor that is small and that does not require the 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 to measure radiation dose. However, even with a semiconductor detector, there is a limit to miniaturization when including a signal processing system, and a semiconductor detector requires the application of a voltage.

Therefore, an optical fiber type radiation monitor has been developed which uses a scintillator element as a sensor, transmits photons generated from the scintillator element through an optical fiber, and measures the radiation dose remotely. The optical fiber type radiation monitor allows the sensor to be miniaturized and does not require application of voltage to the sensor. Thus, the optical fiber radiation monitor is suitable for measuring the radiation dose inside the patient's body during radiation therapy and for measuring the radiation dose under the harsh environment of a nuclear power plant.

On the other hand, high-precision measurement is required when using an optical fiber radiation monitor to measure the radiation dose inside a patient's body during radiation therapy or in the harsh environment of a nuclear power plant. As well as sensor degradation, correction is required and periodic calibration is required.

Japanese Patent Application Laid-Open No. 2018-36204 (Patent Document 1) is a background art of this technical field. In Patent Document 1, a radiation detection unit having a radiation detection element that generates light of a predetermined wavelength, a light emission unit that generates light of a wavelength different from the predetermined wavelength, a wavelength selector that cuts off light with a wavelength different from the wavelength of light, an optical fiber that transmits light, a photodetector that converts the light that has passed through the wavelength selector into electrical pulses, and a counting rate of electrical pulses A radiation monitor is described having a counting device that counts and an analytical display device that determines at least the presence or absence of degradation of the light emitter based on the count rate and light intensity of the light emitter (see abstract).

JP 2018-36204 A

Patent Document 1 discloses a radiation detection unit that generates light of a predetermined wavelength, a light emission unit that generates light of a wavelength different from the predetermined wavelength, a light of the predetermined wavelength, and a light of the predetermined wavelength. A fiber optic radiation monitor is described that has a wavelength selective section (optical filter) that blocks light of different wavelengths. In other words, the optical fiber type radiation monitor described in Patent Document 1 has an optical filter installed in the optical transmission line.

However, Patent Literature 1 describes the possibility that the installation of an optical filter in the light transmission path reduces the intensity of the light transmitted to the photodetector (photoelectric converter), thereby reducing the sensitivity of monitoring. Not listed.

Therefore, the present invention provides an optical fiber type radiation monitor that suppresses the attenuation of the intensity of light transmitted to a photoelectric converter, does not lower the sensitivity of monitoring, and measures the radiation dose with high precision, and a method of using it. do.

In order to solve the above-described problems, the optical fiber type radiation monitor of the present invention includes a sensor that generates photons depending on the dose of incident radiation, an optical fiber that transmits the photons generated by the sensor, and an optical fiber that transmits the photons. A photoelectric converter that converts the photons into electrical signals, a counting device that counts the electrical signals converted by the photoelectric converters and outputs the counted value of the electrical signals, and a sensor that is irradiated with a laser beam through an optical fiber. a light emitting unit that emits light, a light emitting 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, and receives the laser light irradiation timing signal output by the light emitting timing control unit, Receive the count value of the electrical signal output by the counter, create correction data based on the laser beam irradiation timing signal and the count value of the electrical signal, and when measuring the radiation dose, use the count value of the electrical signal and the count value of the electrical signal. and a correction device that performs correction processing based on correction data and calculates a radiation dose or a radiation dose rate, and a display device that displays the radiation dose or the radiation dose rate.

Further, in order to solve the above-described 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 dose of incident radiation in the sensor; A transmission step of transmitting the photons generated by the photoelectric converter, a conversion step of converting the photons transmitted by the optical fiber into an electrical signal, and a counting device, counting the electrical signal converted by the photoelectric converter, A counting step of outputting the count value of the electrical signal, an irradiation step of irradiating the sensor with a laser beam through an optical fiber in the light emitting unit, and a laser of the laser light emitted by the light emitting unit in the light emission timing control unit A control step of controlling the light irradiation timing and outputting a laser light irradiation timing signal, and a correction device receiving the laser light irradiation timing signal output by the light emission timing control unit, and when the sensor light emission decays after the laser light irradiation. A creation step of creating correction data based on the number of photons counted, and in the case of measuring the radiation dose, a correction device performs correction processing based on the count value of the electrical signal and the correction data, and a calculation step of calculating a radiation dose or a radiation dose rate.

According to the present invention, there is provided an optical fiber type radiation monitor capable of suppressing attenuation of the intensity of light transmitted to a photoelectric converter and measuring radiation dose with high precision without lowering the sensitivity of monitoring, and a method of use thereof. can do.

Problems, configurations, and effects other than those described above will be clarified by the description of the embodiments below.

1 is an explanatory diagram for explaining the configuration of a radiation monitor 1 described in Example 1; FIG. 4 is a conceptual diagram illustrating the process of photon generation by radiation incident on the sensor 10 described in Example 1. FIG. 4 is an explanatory diagram illustrating the relationship between the radiation dose rate and the photon count rate described in Example 1. FIG. 4 is an explanatory diagram illustrating the relationship between the photon count rate and the electrical pulse count rate described in Example 1. FIG. 4 is an explanatory diagram for explaining the relationship between the intensity of laser light and the number of photons described in Example 1. FIG. 4 is a time chart for explaining laser light irradiation timing, sensor light emission, and attenuation measurement described in Example 1. FIG. FIG. 10 is an explanatory diagram for explaining the configuration of a radiation monitor 2 described in Example 2;

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that substantially the same or similar configurations are denoted by the same reference numerals, and the description may be omitted if the description is redundant.

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

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

The radiation monitor 1 described in Example 1 is an optical fiber radiation monitor (hereinafter referred to as "radiation monitor").

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

The sensor 10 has a radiation emitting element that produces photons (hereinafter "photons") that depend on (correspond to) the dose of the incident radiation. A radiation light-emitting element generates photons when radiation is incident thereon. That is, when radiation is incident on the sensor 10, the sensor 10 generates (emits or fluoresces) photons depending on the dose of the incident radiation.

The amount of 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 radiation incident on the sensor 10 and the number of photons per unit time generated by the sensor 10 (hereinafter referred to as "photon count rate") have linearity.

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

By including at least one or more rare earth elements in the radiation emitting element in this way, the linearity between the dose rate of the radiation incident on the sensor 10 and the photon count rate can be further improved. Even when radiation with a high dose rate is incident on the radiation monitor 1, the linearity between the dose rate of radiation and the photon count rate can be maintained, and the dose rate of radiation can be accurately measured.

A radiation-emitting material represented by general formula (1) may also be used in the radiation-emitting device.

ATaO ₄ :B General formula (1)
In the general formula (1), A and B are rare earth elements having a 4f-4f electronic transition, and at least one of Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Tb. 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 emission intensity of the sensor 10 can be improved.

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

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

The photoelectric converter 30 connects with the sensor 10 via the optical fiber 20 . The photoelectric converter 30 converts the transmitted photons into electrical signals (hereinafter referred to as "electrical pulses"). The photoelectric converter 30 converts each individual photon transmitted by the optical fiber 20 into individual electrical pulses. Then, the photoelectric converter 30 emits one electric pulse for one photon.

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

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

The counting device 40 is connected to the photoelectric converter 30 via a signal line. A counting device 40 counts the emitted electrical pulses. In other words, the counting device 40 counts the electric pulses that are transmitted one by one, and outputs the count value (the number of electric pulses) of the electric pulses counted by the counting device 40 .

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

On the other hand, when measuring the radiation dose, the deterioration of the sensor 10 must be taken into consideration and the electric pulse count value (or the electric pulse counting rate) must be corrected (correction processing).

For correction, the sensor 10, the optical fiber 20, the photoelectric converter 30, the counting device 40, the light emitting section 50, the light emission timing control section 60, and the correcting device 70 are used.

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

The intensity of the laser light irradiated to the sensor 10 and the number of photons have linearity. In other words, the intensity of the laser light with which the sensor 10 is irradiated and the photon count rate have linearity.

Also, the energy of the laser light must be higher than the energy of the photons generated by the sensor 10 . In other words, the wavelength of the laser light should be shorter than the wavelength of photons generated by the sensor 10 .

The light emission timing control section 60 is connected to the light emission section 50 via a signal line. The light emission timing control unit 60 controls the light emission timing (laser light irradiation timing) at which the light emitting unit 50 generates laser light, that is, the laser light irradiation timing of the laser light emitted by the light emitting unit 50, and outputs a light emission timing signal (laser light irradiation timing signal).

The correction device 70 is connected to the light emission timing control section 60 and the counting device 40 via signal lines. 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 electrical pulse output by the counting device 40 from the counting device 40, and performs laser light irradiation. Correction data is generated based on the timing and the electrical pulse count.

In addition, the correction device 70 stores the correction data to be created, uses the stored correction data, and when measuring the radiation dose, considers the deterioration of the sensor 10, the count value of the electric pulse (or the electric pulse count rate).

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

Note that 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, for example.

The display device 80 displays the radiation dose (or radiation dose rate). The display device 10 also displays an abnormality of the sensor 10 and the like.

Next, the process of generating photons by radiation incident on the sensor 10 described in the first embodiment will be described.

FIG. 2 is a conceptual diagram illustrating the process of photon generation by 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 electrons in the ground state (energy level L1) in the sensor 10 to transition to an excited state (energy level L3) with a higher energy level ( See arrow a1 in FIG. 2). Then, electrons in a high energy level excited state (energy level L3) transition to a low energy level excited state (energy level L2) (see arrow b1 in FIG. 2). The sensor 10 generates photons (p) having an energy corresponding to the energy difference 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 energy of the laser light causes electrons at the energy level L1 in the sensor 10 to transition to the energy level L3 (indicated by the arrow in FIG. 2). a1). Electrons at the energy level L3 transition to the energy level L2 (see arrow b1 in FIG. 2). The sensor 10 generates photons (p) having an energy corresponding to the energy difference between the energy level L3 and the energy level L2.

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

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

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

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

3B is an explanatory diagram illustrating the relationship between the photon count rate and the electrical pulse count rate described in Example 1. FIG.

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

Thus, there is a one-to-one correspondence between the radiation dose rate and the photon count rate, and a one-to-one correspondence between the photon count rate and the electrical pulse count rate. In other words, there is also a one-to-one correspondence between the dose rate of radiation and the electrical pulse count rate. Thereby, the electrical pulse count rate can be converted into the radiation dose rate.

Then, when measuring the radiation dose, from the relationship between the radiation dose rate and the photon count rate (see FIG. 3A) and the relationship between the photon count rate and the electrical pulse count rate (see FIG. 3B), the electrical pulse count rate and the radiation dose rate, and the radiation dose is measured based on the preset one-to-one relationship between the electric pulse counting rate and the radiation dose rate.

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

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

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

When the electrical pulse counting rate is to be corrected in consideration of deterioration of the sensor 10, the following steps (1) to (4) are performed.

(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 laser beams of at least two intensities (see a in FIG. 3C). Then, the number of photons is converted into a photon count rate.

This proportional relationship (a) is the same as the relationship between the radiation dose rate and the photon count rate in the sensor 10 without deterioration. Here, "the sensor 10 without deterioration" means the initial state of the sensor 10. FIG.

(2) Next, the sensor 10 before measuring the radiation dose 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 laser beams of at least two intensities (see b in FIG. 3C). Then, the number of photons is converted into a photon count rate.

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

In other words, deterioration of the sensor 10 can be grasped as a difference in slope of the photon count rate before the radiation dose is measured.

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

Then, when measuring the radiation dose, for example, the photon count rate converted from the dose rate of the radiation to be measured is multiplied by the correction data to correct the electric pulse count rate. Thereby, the radiation dose can be measured with high accuracy.

Next, laser light irradiation timing, sensor light emission, and attenuation measurement described in Example 1 will be described.

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

The laser light is applied to the sensor 10 in a pulsed manner (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 by being irradiated with laser light (sensor emission). The number of photons generated by the sensor 10 peaks during laser light irradiation, and attenuates after laser light irradiation (immediately after light emission). That is, the sensor 10 continues to emit light even after being irradiated with the laser light. For example, the emission lifetime (fluorescence lifetime) of the sensor 10 is preferably 1 μs or longer, and is 230 μs when Nd (neodymium):YAG is used as the radiation emitting element.

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

In this manner, the correction device 70 receives the laser light irradiation timing signal from the light emission timing control unit 60, receives the count value of the electric pulse from the counter device 40, counts the number of photons when the sensor light emission is attenuated, and generates correction data. create. In other words, when generating correction data, the radiation dose can be measured with high accuracy by removing noise such as laser light and measuring only sensor light emission.

Here, the noise generated by irradiating the laser light includes the main wavelength component itself of the laser light, the laser light other than the main wavelength component such as harmonic components, and the noise caused by the irradiation of the laser light. and the like. An optical fiber radiation monitor that installs an optical filter in the light transmission line uses the difference in wavelength to remove noise. In some cases, it may not be possible to remove components, light emission from the optical fiber 20, and the like.

According to the first embodiment, it is possible to remove noise generated by irradiating laser light, which could not be removed conventionally, and to correct it with high accuracy.

Note that the correction data can be created online and/or offline.

Further, the timing (measurement timing) at which the correction device 70 counts the number of photons at the time of attenuation of sensor light emission after laser light irradiation is, for example, several milliseconds. 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 during a preset correction data collection period based on the laser light irradiation timing signal and the pulse width.

Thus, the radiation monitor 1 described in Example 1 has the following configuration requirements.
a sensor 10 that generates photons that are dependent on the dose of the incident radiation (generation step);
- An optical fiber 20 that transmits photons generated by the sensor 10 (transmission step)
A photoelectric converter 30 that converts photons transmitted by the optical fiber 20 into electric pulses (conversion step)
A counting device 40 that counts the electrical pulses converted by the photoelectric converter 30 and outputs the counted value of the electrical pulses (counting step)
A light emitting unit 50 that irradiates the sensor 10 with laser light through the optical fiber 20 (irradiation step)
A light emission timing control unit 60 that controls the laser light irradiation timing of the laser light emitted by the light emitting unit 50 and outputs a laser light irradiation timing signal (control step)
Receiving the laser beam irradiation timing signal output by the light emission timing control unit 60, receiving the count value of the electrical pulses output by the counting device 40, and generating correction data based on the laser beam irradiation timing signal and the count value of the electrical pulses. Correction device 70 to be created (creation process)
Display device 80 for displaying radiation dose (or radiation dose rate) (display step)
When measuring the radiation dose, the correction device 70 corrects the electrical pulse count rate based on the correction data and the photon count rate converted from the measured radiation dose rate (correction step).

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

In addition, when measuring the radiation dose, the correction device 70 performs correction processing based on the count value of the electric pulse and the correction data, and calculates the radiation dose (or radiation dose rate) (calculation step ).

As described above, according to the first embodiment, the size of the sensor 10 used in the radiation monitor 1 can be reduced, and application of voltage to the sensor 10 becomes unnecessary.

Further, according to the first embodiment, the radiation dose can be easily and accurately measured by correcting the electric pulse counting rate by using the correction data, taking into consideration the deterioration of the sensor 10 over time. .

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 beam, the monitoring sensitivity is not lowered, and the number of photons is reduced. Accurate measurement is possible, and the radiation dose can be measured with high accuracy.

Furthermore, according to the first embodiment, noise generated by irradiating laser light, which could not be removed in the past, can be removed, corrected with high accuracy, and can be corrected with high accuracy. Quantity can be measured.

Further, according to the first embodiment, deterioration of the sensor 10 can be prevented even when measuring the radiation dose in the patient's body during radiotherapy or when measuring the radiation dose in a severe environment or narrow space of a nuclear power plant. can be considered and used appropriately.

Further, 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 in a medical institution or a research institution, and the range of application is greatly expanded.

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

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

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

Shutter 90 connects with sensor 10 via optical fiber 20 . Also, the shutter 90 is connected to the photoelectric converter 30 via the optical fiber 20 . In other words, the shutter 90 is installed in the photon transmission line before the photoelectric converter 30 . The shutter 90 opens and closes to allow the photons generated by the sensor 10 to pass through or block the photons generated by the sensor 10 (opening/closing process).

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

During the correction data collection period, the shutter 90 is opened under the control of the light emission timing control section 60 and transmits photons to the photoelectric converter 30 . When measuring the radiation dose, the shutter 90 is opened and photons pass through (measurement step). Then, similarly to the first embodiment, correction data is created.

Thus, in addition to the radiation monitor 1 described in the first embodiment, the radiation monitor 2 described in the second embodiment is installed before the photoelectric converter 30, and the laser light irradiation timing signal output by the light emission timing control unit 60 is , and has a shutter 90 that opens and closes the transmission path of photons generated by the sensor 10 . In addition, the shutter 90 opens when the sensor light emission is attenuated after the irradiation of the laser light.

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

In other words, when creating correction data, the shutter 90 closes when the sensor emits light, opens when the sensor emission is attenuated after irradiation with laser light, removes noise such as the laser light, and measures only the sensor light emission. Radiation dose 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 dose can be measured with high accuracy.

In addition, the radiation monitor 2 described in the second embodiment is basically the same as the radiation monitor 1 described in the first embodiment with respect to other configurations and functions of each configuration. Further, the second embodiment can obtain the same effect as the first embodiment.

Furthermore, in the second embodiment, the light emission timing control unit 60 synchronously controls the shutter 90 and the light emission unit 50, thereby eliminating the need for the correction device 70 to control the correction data collection period.

In addition, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments are specifically described in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described.

Also, part of the configuration of one embodiment can be replaced with part of the configuration of another embodiment. Also, the configuration of another embodiment can be added to the configuration of one embodiment. Also, a part of the configuration of each embodiment can be deleted, a part of another configuration can be added, and a part of another configuration can be substituted.

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 produces photons that are dependent on the dose of the 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;
a counting device that counts the electrical signal converted by the photoelectric converter and outputs a count value of the electrical signal;
a light emitting unit that irradiates the sensor with a laser beam through 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;
Receiving the laser light irradiation timing signal output by the light emission timing control unit, receiving the count value of the electrical signal output by the counting device, and performing correction based on the laser light irradiation timing signal and the count value of the electrical signal a correction device that, when creating data and measuring the radiation dose, performs correction processing based on the count value of the electrical signal and the correction data, and calculates the radiation dose or the radiation dose rate;
a display device that displays the radiation dose or the dose rate of the radiation;
A fiber optic radiation monitor, comprising: A fiber optic radiation monitor according to claim 1,
An optical fiber type radiation monitor, wherein the sensor uses transparent yttrium aluminum garnet as a base material, and at least one rare earth element selected from ytterbium, neodymium, cerium, and praseodymium as an additive. . A fiber optic radiation monitor according to claim 1,
The sensor is ATaO ₄ :B (A and B are at least one rare earth element selected from Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Tb). fiber optic radiation monitor. An optical fiber type radiation monitor according to claim 1 or claim 3,
An optical fiber type radiation monitor, wherein the sensor has a fluorescence lifetime of 1 μs or more. An optical fiber type radiation monitor according to claim 1 or claim 4,
The optical fiber type optical correction device, wherein, when creating the correction data, the correction device creates the correction data based on the number of photons counted at the time of attenuation of the sensor emission after the irradiation of the laser light. Radiation monitor. a sensor that produces photons that are dependent on the dose of the 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;
a counting device that counts the electrical signal converted by the photoelectric converter and outputs a count value of the electrical signal;
a light emitting unit that irradiates the sensor with a laser beam through 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 for receiving a laser light irradiation timing signal output from the light emission timing control unit and opening and closing a transmission path of photons generated by the sensor;
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 dose, the count value of the electric signal and the correction data A correction device that performs correction processing based on and calculates the radiation dose or radiation dose rate,
a display device that displays the radiation dose or the dose rate of the radiation;
A fiber optic radiation monitor, comprising: A fiber optic radiation monitor according to claim 6,
The optical fiber type radiation monitor, wherein the shutter opens when the sensor light emission is attenuated after irradiation with the laser light. A fiber optic radiation monitor according to claim 7,
A fiber optic radiation monitor, wherein the correction device, when creating the correction data, creates the correction data based on the number of photons counted when the shutter is open. generating photons at the sensor that are dependent on the dose of the incident radiation;
a transmission step of transmitting the photons generated by the sensor through an optical fiber;
a conversion step of converting the photons transmitted by the optical fiber into an electrical signal with a photoelectric converter;
a counting step of counting the electrical signal converted by the photoelectric converter and outputting a count value of the electrical signal with a counting device;
an irradiation step of irradiating the sensor with a laser beam through the optical fiber in a light emitting unit;
a control step of controlling the laser light irradiation timing of the laser light emitted by the light emitting unit and outputting a laser light irradiation timing signal by the light emission timing control unit;
a creation step of receiving the laser light irradiation timing signal output by the light emission timing control unit in the correction device and creating correction data based on the number of photons counted when the sensor light emission is attenuated after the laser light irradiation;
When measuring the radiation dose, a correction device performs correction processing based on the count value of the electrical signal and the correction data, and a calculation step of calculating the radiation dose or the radiation dose rate;
A method of using a fiber optic radiation monitor, comprising:

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