JP2012021847A - Reader for glass dosimeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reader for glass dosimeter which can be made compact and inexpensive, and can accurately read a dose of radiation emitted on a fluorescence glass element over a wide range.SOLUTION: The reader for glass dosimeter is a device for reading a dose of radiation emitted on a fluorescence glass element 10, and includes an irradiation section 20 for irradiating the element 10 with ultraviolet rays, a fluorescence amount varying section 30, a photomultiplier tube 40, a photon counting section 60, a fluorescence amount control section 70 and a dose calculation section 80. Fluorescence 10a emitted from the element 10 passes through the fluorescence amount varying section 30 to change its fluorescence quantity, and is incident on the photomultiplier tube 40. The photon counting section 60 counts the number of an output pulse obtained by A/D converting the output signal of the photomultiplier tube 40. The fluorescence amount control section 70 controls the amount of fluorescence incident on the photomultiplier tube 40 based on the number of the output pulse. The dose calculation section 80 calculates the dose of the radiation emitted on the element 10 on the basis of the number of the output pulse, the change amount of the fluorescence and the irradiation amount of the ultraviolet rays.

Description

  The present invention relates to a glass dosimeter reader for reading a radiation dose irradiated to a fluorescent glass element based on the intensity of fluorescence emitted from the fluorescent glass element by ultraviolet excitation.

  A fluorescent glass element is widely used as a detection element for measuring radiation exposure dose in the field of handling radiation, such as the nuclear field and the medical field. The fluorescent glass element is made of, for example, phosphate glass containing silver ions. The fluorescent glass element activated by irradiation with radiation emits fluorescence when excited by irradiation with ultraviolet rays having a wavelength of 300 to 400 nm (so-called radiophotoluminescence phenomenon, hereinafter referred to as “RPL phenomenon”). Since this fluorescence intensity is proportional to the radiation dose irradiated to the fluorescent glass element (hereinafter referred to as “irradiated dose”), the irradiated dose can be read by measuring the fluorescence intensity (for example, (See Patent Documents 1 and 2).

  The irradiation dose of the fluorescent glass element is read using a glass dosimeter reading device (hereinafter referred to as “reading device”). A typical reading device includes an excitation light source such as a solid-state laser oscillator, a photomultiplier tube, an analog integration unit, and a dose calculation unit.

  The irradiation dose is read by attaching a fluorescent glass element to a reading device. First, the laser light emitted from the solid-state laser oscillator is passed through an ultraviolet transmission filter to selectively extract ultraviolet rays and irradiate the fluorescent glass element. Then, the fluorescent glass element emits fluorescence having an intensity proportional to the irradiation dose. Subsequently, after the fluorescence emitted from the fluorescent glass element is converted into a current signal using a photomultiplier tube, the analog integration unit obtains the signal amounts at the first and second sampling times having different times.

  Thereafter, the dose calculation unit calculates the fluorescence intensity, and hence the irradiation dose of the fluorescent glass element, from the signal amounts at the first and second sampling times. Here, the fluorescent component emitted from the fluorescent glass element includes a noise component in addition to the component due to the RPL phenomenon. The noise component includes a first noise component having a short decay time constant inherent to the fluorescent glass element (so-called pre-dose component), a second noise component having a short decay time constant emitted from dirt attached to the surface of the glass element, and the like. The third noise component having a long decay time constant whose cause is unknown is included. Therefore, the dose calculation unit uses the difference in the decay time constant of each component to time-resolve the component due to the RPL phenomenon and the noise component, and remove the noise component. Then, the irradiation dose is calculated from the component due to the RPL phenomenon. In this way, the irradiation dose of the fluorescent glass element can be accurately read (for example, see Patent Document 3).

JP 2005-114410 A JP-A-8-220235 JP 59-190681 A

  As described above, a light source with high output energy such as a solid-state laser oscillator is usually used as the excitation light source of the reader. However, since the solid-state laser oscillator is large and expensive, the reader is also large and expensive. Become. Therefore, in order to meet the needs for downsizing and cost reduction of the reading apparatus, it has been proposed to use a light emitting diode (LED) as an excitation light source of the reading apparatus.

  However, light emitting diodes (LEDs) have lower output energy than solid state laser oscillators. Therefore, if the irradiation dose of the fluorescent glass element is small, the fluorescence intensity generated by the RPL phenomenon becomes weak. In such a case, if the output signal from the photomultiplier tube is processed using the analog integration method described above, the S / N ratio becomes small, and the dose calculation unit uses components due to the RPL phenomenon and noise components. Cannot be sufficiently decomposed, and the irradiation dose cannot be calculated with high accuracy. That is, when the analog integration method is used, it is impossible to accurately read a low dose.

  Therefore, it is conceivable to use a photon counting method (photon counting method) instead of the analog integration method described above. In reading using the photon counting method, a pulsed electric signal from a photomultiplier tube is subjected to current / voltage conversion (hereinafter referred to as “I / V conversion”) and analog / digital conversion (hereinafter referred to as “A”) in a photon counting unit. / D conversion ”) to obtain output pulses, and count the number of output pulses (hereinafter referred to as“ count value ”) per first sampling time and second sampling time having different times. Then, the dose calculation unit calculates the irradiation dose from the count value.

  Here, FIG. 10 is a graph showing an example of the relationship between the count value and the count omission ratio. From FIG. 10, it can be seen that almost no count omission occurs until the count value reaches 10,000, but when the count value exceeds 10,000, the omission of count increases. When the irradiation dose of the fluorescent glass element is large and the fluorescence intensity is strong, the output pulses are overcrowded and a plurality of output pulses are overlapped. Then, in the photon counting unit, a plurality of overlapping output pulses are counted as one output pulse, and count omission occurs. As a result, the reading amount is calculated lower than the actual irradiation dose in the dose calculation unit. That is, when the photon counting method is used, it is impossible to accurately read a high dose.

  Accordingly, the present invention has been made to solve the above-described problems, enables downsizing and cost reduction, and accurately reads the radiation dose irradiated to the fluorescent glass element over a wide range. An object of the present invention is to provide a glass dosimeter reader capable of performing the above.

  In order to achieve the above object, a glass dosimeter reader according to the present invention is a glass dosimeter reader that reads a radiation dose irradiated on a fluorescent glass element, and includes a light source that emits ultraviolet rays, and the fluorescent glass An irradiation unit that irradiates the element with ultraviolet light, a fluorescence amount variable unit that changes the amount of fluorescence by passing the fluorescence emitted from the fluorescent glass element, and outputs an electrical signal by detecting the fluorescence that has passed through the fluorescence amount variable unit A photoelectric conversion unit, a photon counting unit that counts the number of output pulses obtained by analog / digital conversion of an electrical signal output from the photoelectric conversion unit, a number of output pulses counted by the photon counting unit, and the fluorescence A dose calculation unit that calculates a radiation dose irradiated to the fluorescent glass element based on a change amount of fluorescence in the variable amount unit and an ultraviolet ray irradiated to the fluorescent glass element; and the light Wherein the counting unit is equipped with a fluorescence amount control unit for controlling the amount of fluorescence is made incident by sending a control signal to the fluorescence amount varying section based on the number of output pulses counted in the photoelectric conversion unit.

  ADVANTAGE OF THE INVENTION According to this invention, the glass dosimeter reader which can be reduced in size and cost and can read the radiation dose irradiated to the fluorescent glass element over a wide range with high precision can be provided.

1 is an overall configuration diagram of a glass dosimeter reading device according to a first embodiment of the present invention. It is the fragmentary sectional view showing the schematic structure of the glass dosimeter reading device concerning a 1st embodiment of the present invention. It is the perspective view which showed the fluorescence amount variable part of the glass dosimeter reader which concerns on the 1st Embodiment of this invention. It is a partial block diagram for demonstrating the photon counting part of the glass dosimeter reading device which concerns on the 1st Embodiment of this invention. It is a partial block diagram for demonstrating the fluorescence amount control part and dose calculation part of the glass dosimeter reader which concerns on the 1st Embodiment of this invention. It is a table | surface for demonstrating the glass dosimeter reader which concerns on the 1st Embodiment of this invention, Comprising: The passage window and the transmission which the fluorescence which the fluorescent glass element 10 emitted at the time of the 1st measurement and remeasurement passes are transmitted It is the table | surface which showed the rate. It is a partial block diagram for demonstrating the fluorescence amount control part and dose calculation part of the glass dosimeter reading apparatus which concern on the 2nd Embodiment of this invention. It is the table | surface which showed the correspondence of the count value which the count part of the glass dosimeter reader which concerns on the 2nd Embodiment of this invention counted, and the passage window which a fluorescence amount determination part determines. It is a whole block diagram of the glass dosimeter reading apparatus which concerns on the 3rd Embodiment of this invention. It is the graph which showed the relationship between the count value which the photon counting part of the glass dosimeter reading device counted, and the ratio of count omission.

[First Embodiment]
A glass dosimeter reading apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

  First, an outline of the structure and configuration of the glass dosimeter reading apparatus according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is an overall configuration diagram of a glass dosimeter reading apparatus. FIG. 2 is a partial cross-sectional view showing a schematic structure of the glass dosimeter reading apparatus. FIG. 3 is a perspective view showing a fluorescence amount variable portion of the glass dosimeter reading device.

  The glass dosimeter reading device according to the present embodiment is a device that reads the radiation dose irradiated to the fluorescent glass element 10. The fluorescent glass element 10 is a detection element for measuring an irradiation dose, and is made of, for example, phosphate glass containing silver ions. The fluorescent glass element 10 activated by irradiation with radiation emits fluorescence 10a when excited by irradiation with ultraviolet light 20a having a wavelength of 300 to 400 nm. The reading device reads the irradiation dose of the fluorescent glass element 10 using a characteristic that the intensity of the fluorescence 10 a emitted from the fluorescent glass element 10 is proportional to the irradiation dose of the fluorescent glass element 10.

  The glass dosimeter reading device according to the present embodiment includes an irradiation unit 20, a fluorescence amount variable unit 30, a photoelectric conversion unit, a controller unit 50, and the like. In the present embodiment, the photoelectric conversion unit is a photomultiplier tube 40.

  The irradiation unit 20 plays a role of irradiating the fluorescent glass element 10 with ultraviolet rays 20a. The irradiation unit 20 includes a light source 22, a power supply 24, a hemispherical lens 26, and an ultraviolet transmission filter 28.

In the present embodiment, the light source 22 is a light emitting diode, for example, and is connected to the power supply 24. The power source 24 is connected to the controller unit 50 via a cable 52 and supplies a constant amount of current to the light source 22 based on a control signal from a fluorescence amount control unit 70 described later. In the present embodiment, the light source 22 emits, for example, 4 kw / m ² of light (pulse width 1 μsec, 20 kPulse / sec) 22 a.

  Light 22 a emitted from the light source 22 passes through the hemispherical lens 26 and is collected. Subsequently, the light 22 a passes through the ultraviolet transmission filter 28, and only the ultraviolet rays 20 a are irradiated on the side surface of the fluorescent glass element 10. The ultraviolet light transmission filter 28 selectively transmits ultraviolet light 20 a having a wavelength of 300 to 400 nm among the light 22 a emitted from the light source 22. As described above, the fluorescent glass element 10 irradiated with radiation emits fluorescence 10a when irradiated with the ultraviolet rays 20a from the irradiation unit 20.

  As illustrated in FIG. 2, the irradiation unit 20 is housed in a rectangular first case 120. The first case 120 includes a bottom plate 122 and an upper lid 124, and the upper lid 124 is attached to the bottom plate 122 so as to be openable and closable.

  As shown in FIG. 2, the bottom plate 122 is formed with a partition wall 126 that partitions the inside of the first case 120 into a first space 120a and a second space 120b. The irradiation unit 20 is housed in the first space 120a. Moreover, the fluorescent glass element 10 is installed in the second space 120b. A slit 126 a is formed in the partition wall 126, and the ultraviolet light 20 a that has passed through the ultraviolet transmission filter 28 passes through the slit 126 a and is irradiated onto the fluorescent glass element 10. The partition 126 plays a role of preventing scattered light in the first space 120 a from entering the fluorescent glass element 10.

  The irradiation dose is read by opening the upper lid 124 and mounting the rectangular plate-shaped fluorescent glass element 10 on the glass element holding portion 122a formed on the second space 120b side of the bottom plate 122, and then closing the upper lid 124. Is called. When the upper lid 124 is closed, the inside of the first case 120 is a dark room.

  When the side surface of the fluorescent glass element 10 is irradiated with the ultraviolet rays 20a, the fluorescent light 10a is emitted from the lower surface side of the fluorescent glass element 10. The fluorescent light 10 a passes through an emission window 122 b formed in the bottom plate 122 and proceeds into a second case 128 provided below the first case 120. Subsequently, the fluorescence 10 a passes through the hemispherical lens 112 to be converted into parallel light, and then passes through the fluorescence amount variable unit 30. The fluorescence 10b that has passed through the fluorescence amount variable unit 30 is redirected by the mirror 114 and then passes through the interference filter 116. Thereafter, the fluorescent light 10 b is collected through the hemispherical lens 118 and is incident on the photomultiplier tube 40. The incident window 128b of the second case 128 is blocked by the ultraviolet light removal filter 110 so that the ultraviolet light 20a in the first case 120 does not enter the second case 128.

  Here, the fluorescence amount variable unit 30 will be described with reference to FIG. The fluorescence amount variable unit 30 plays a role of changing a fluorescence amount incident on the photomultiplier tube 40 (hereinafter referred to as “fluorescence incident amount”) based on a control signal from a fluorescence amount control unit 70 described later. The fluorescence amount variable unit 30 is installed in the second case 128 as shown in FIG. In the present embodiment, as shown in FIG. 3, the fluorescence variable unit 30 includes a fluorescence variable plate 32, a drive device 36, and a shaft 36a.

  The fluorescence amount variable plate 32 is formed in a disc shape, and is arranged perpendicular to the optical path of the fluorescence 10 a emitted from the fluorescent glass element 10. Four passage windows (first to fourth passage windows) 32a to 32d are formed in the fluorescence amount variable plate 32 at equal intervals in the circumferential direction. The first to fourth passage windows 32a to 32d are sequentially arranged in the clockwise direction.

  In each of the first to third passage windows 32a to 32c, first to third neutral density filters 34a to 34c for dimming the passing fluorescent light 10a are fitted. The transmittances of the first to third neutral density filters 34a to 34c are about 1/1000, about 1/100, and about 1/10, respectively. Note that a neutral density filter is not fitted in the fourth passage window 32d, and the fluorescent light 10a is allowed to pass through without changing the amount of light.

  The drive device 36 is connected to the fluorescence amount variable plate 32 through a shaft 36a. The drive device 36 rotates the fluorescence variable plate 32 counterclockwise about the axis so that the fluorescence 10a passes through any of the first to fourth passage windows 32a to 32d. The drive device 36 is connected to the controller unit 50 via a cable 54 (not shown in FIG. 2), and rotates the fluorescence amount variable plate 32 based on a control signal from a fluorescence amount control unit 70 described later.

  The photomultiplier tube 40 is a type of phototube that converts light energy into electrical energy using the photoelectric effect, and is a high-sensitivity photodetector having a current amplification (electron multiplication) function. The fluorescence 10a incident on the photomultiplier tube 40 knocks out photoelectrons from the photocathode. The struck photoelectrons are accelerated by the applied voltage, collide with the first dynode, and knock out a plurality of secondary electrons per photoelectron. The knocked-out secondary electrons collide with the second dynode and knock out more secondary electrons. The photomultiplier tube 40 repeats this to multiply the secondary electrons, and takes out the secondary electrons that have reached the anode as a pulse current signal 40a.

  As shown in FIG. 2, the photomultiplier tube 40 is provided adjacent to the second case 128 and below the first case 120. A heat sink 42 for cooling is attached to the side surface of the photomultiplier tube 40.

  The controller unit 50 includes a photon counting unit 60, a fluorescence amount control unit 70, a dose calculation unit 80, a recording unit 90, and a display unit 100.

  The photon counting unit 60 counts the number of output pulses obtained by performing I / V conversion and A / D conversion on the pulse electrical signal 40a output from the photomultiplier tube 40 using a photon counting method. Based on the number of output pulses counted by the photon counting unit 60, the fluorescence amount control unit 70 transmits a control signal to the fluorescence amount variable unit 30 to control the amount of fluorescence incident on the photomultiplier tube 40. The dose calculating unit 80 is based on the number of output pulses counted by the photon counting unit 60, the amount of change in fluorescence in the fluorescence amount varying unit 30, and the amount of ultraviolet light applied to the fluorescent glass element 10. The irradiation dose is calculated. The display unit 100 is, for example, a display, and displays the irradiation dose calculated by the dose calculation unit 80.

  The controller unit 50 is provided below the first case 120 adjacent to the photomultiplier tube 40. The fluorescence amount control unit 70 of the controller unit 50 is connected to the power supply 24 and the driving device 36 via cables 52 and 54.

  Next, the photon counting unit 60 will be described in detail with reference to FIG. FIG. 4 is a partial configuration diagram for explaining a photon counting unit of the glass dosimeter reading device.

  The photon counting unit 60 includes an I / V conversion / amplification unit 62, an A / D conversion unit 64, and a count unit 66.

  The I / V conversion / amplification unit 62 receives the pulse current signal 40a output from the photomultiplier tube 40, and generates and outputs a pulse voltage signal 62a by the I / V conversion circuit and the amplification circuit.

  The A / D conversion unit 64 receives the pulse voltage signal 62a output from the I / V conversion / amplification unit 62, and compares the value of the pulse voltage signal 62a with a predetermined threshold value using a comparison circuit. When the value of the pulse voltage signal 62a is lower than the threshold value, the A / D conversion unit 64 determines that the pulse component is a noise component and outputs “0”. If it is higher, “1” is output as a signal component. In this way, the A / D converter 64 outputs the digital pulse signal 64a.

  The count unit 66 receives the digital pulse signal 64a output from the A / D conversion unit 64, and counts the number of output pulses per unit time included in the digital pulse signal 64a.

  Specifically, the count unit 66 is for 5 μsec from 2 μsec to 7 μsec after light emission from the light source 22 (hereinafter referred to as “first sampling time”) and for 5 μsec from 40 μsec to 45 μsec after light emission from the light source 22 (hereinafter, “ The number of output pulses in “second sampling time”) is counted. In the present embodiment, the light source 22 emits light 20000 times and the fluorescent glass element 10 emits 20000 times per measurement. Then, the count unit 66 receives 20000 digital pulse signals 64a and integrates the number of output pulses for 20000 times. That is, the count unit 66 counts the number of output pulses accumulated in the first sampling time (hereinafter referred to as “first count value”) and the number of output pulses accumulated in the second sampling time (hereinafter referred to as “first count value”). 2) ”). The count unit 66 outputs count value data 66a including the first count value and the second count value.

  Here, when the photon counting method is used for processing the output signal from the photomultiplier tube 40, as described above, if the fluorescence intensity is strong and the number of photons detected at the sampling time is extremely large, the count leakage occurs. End up. On the other hand, if the fluorescence intensity is weak and the number of photons detected at the sampling time is extremely small, the variation in the count value becomes large.

  Therefore, the fluorescence amount control unit 70 of the glass dosimeter reader according to the present embodiment feedback controls the amount of fluorescence incident on the photomultiplier tube 40 in order to keep the count value within an appropriate range. The fluorescence amount control unit 70 will be described in detail with reference to FIGS. 5 and 6. FIG. 5 is a partial configuration diagram for explaining a fluorescence amount control unit and a dose calculation unit of the glass dosimeter reader. FIG. 6 is a table showing the passage window and the transmittance through which the fluorescence emitted from the fluorescent glass element 10 passes during the first measurement and the remeasurement.

  The fluorescence amount control unit 70 includes a data transmission unit 72, a remeasurement necessity determination unit 74, a fluorescence amount determination unit 76, and a control signal output unit 78.

  The data transmission unit 72 receives the count value data 66 a output from the count unit 66 and transmits the count value data 66 a to the remeasurement necessity determination unit 74 and the dose calculation unit 80.

  The re-measurement necessity determination unit 74 receives the count value data 66a and determines whether the count value is within a predetermined range (for example, 1000 or more). In the present embodiment, the remeasurement necessity determination unit 74 determines whether or not the first count value is 1000 or more. The remeasurement necessity determination unit 74 outputs a calculation instruction signal 74a to the dose calculation unit 80 when the count value is 1000 or more.

  On the other hand, when the count value is less than 1000, the remeasurement necessity determination unit 74 outputs a remeasurement instruction signal 74b to the fluorescence amount determination unit 76.

  When the fluorescence amount determining unit 76 receives the remeasurement instruction signal 74b, the fluorescent light 10a emitted from the fluorescent glass element 10 is passed through any of the first to fourth passage windows 32a to 32d. Information (hereinafter referred to as “passage window data”) 76a is read from the recording unit 90, and a passage window having a larger transmittance than the passage window is determined. Then, the fluorescence amount determining unit 76 outputs the passing window data 76a including the determined passing window information to the recording unit 90 and the control signal output unit 78. The recording unit 90 stores the passage window data 76a.

  When receiving the passing window data 76a, the control signal output unit 78 outputs the control signal 78a to the driving device 36 via the cable 54. The driving device 36 that has received the control signal 78a counterclockwise around the fluorescence variable plate 32 so that the fluorescence 10a emitted from the fluorescent glass element 10 passes through the passage window determined by the fluorescence determination unit 76. Rotate by 45 °. At the same time, the control signal output unit 78 outputs a control signal 78 a to the power supply 24 via the cable 52. The power supply 24 that has received the control signal 78a supplies a constant amount of current to the light source 22 after the fluorescence amount variable plate 32 rotates, and causes the light source 22 to emit light again.

  In the present embodiment, as shown in FIG. 6, during the first measurement (initial setting), the fluorescence variable plate 32 has the fluorescence 10a emitted from the fluorescent glass element 10 passing through the first passage window 32a. Aligned to pass. That is, the fluorescent light 10 a emitted from the fluorescent glass element 10 passes through the first light shielding filter 34 a, is reduced to about 1/1000 light amount, and enters the photomultiplier tube 40. When the re-measurement necessity determination unit 74 determines that the count value is less than 1000, the fluorescence amount variable plate 32 has the second fluorescence 10a emitted from the fluorescent glass element 10 by the drive device 36. It rotates so that it may pass through the passage window 32b.

  Thereafter, the light source 22 emits light again, and the second measurement is started. At the time of the second measurement, the fluorescence 10a emitted from the fluorescent glass element 10 passes through the second light shielding filter 34b, is reduced to about 1/100, and enters the photomultiplier tube 40. . Therefore, the amount of fluorescence incident on the photomultiplier tube 40 at the time of the second measurement is 10 times the amount of fluorescence incident on the photomultiplier tube 40 at the time of the first measurement. As a result, the count value at the time of the second measurement is approximately 10 times the count value at the time of the first measurement. Then, the re-measurement necessity determination unit 74 determines again whether or not the count value at the time of the second measurement is 1000 or more.

  In this way, the fluorescence amount control unit 70 switches the passage windows through which the fluorescence 10a emitted from the fluorescent glass element 10 passes in the order of the first to fourth passage windows 32a to 32d until the count value reaches 1000 or more. Then, the amount of fluorescence incident on the photomultiplier tube 40 is gradually increased to perform repeated measurement.

  Next, the dose calculation unit 80 will be described in detail with reference to FIG.

  When receiving the calculation instruction signal 74 a output from the remeasurement necessity determination unit 74, the dose calculation unit 80 reads the passage window data 76 a from the recording unit 90. The dose calculation unit 80 obtains the transmittance of the passage window through which the fluorescent light 10 a emitted from the fluorescent glass element 10 has passed from the information on the passage window included in the passage window data 76 a read from the recording unit 90.

  On the other hand, the dose calculation unit 80 removes the output pulses due to the noise component, and obtains the number of output pulses due to the RPL phenomenon. Specifically, the dose calculation unit 80 uses the fact that the decay time constants of the component due to the RPL phenomenon and the noise component are different from each other, and temporally resolves the component due to the RPL phenomenon and the noise component to remove the noise component. Specifically, the dose calculation unit 80 subtracts the second count value from the first count value, removes the output pulse due to the noise component, and integrates the number of output pulses due to the RPL phenomenon (that is, , Count value after noise removal).

  Subsequently, the dose calculation unit 80 multiplies the count value after noise removal by the reciprocal of the transmittance of the passing window to calculate the count value when the fluorescence amount variable unit 30 has not dimmed. For example, when the fluorescent light 10a emitted from the fluorescent glass element 10 passes through the third passage window 32c, the count value after noise removal is multiplied by 10. Thereafter, the irradiation dose is calculated using the count value and the irradiation amount of the ultraviolet rays 20a.

  The dose calculation unit 80 outputs dose data 80a including the calculated irradiation dose to the display unit 100. The display unit 100 receives the dose data 80a and displays the irradiation dose.

  The effect of the glass dosimeter reading device according to this embodiment will be described.

  According to the present embodiment, since the photon counting method is used for processing the output signal from the photomultiplier tube 40, the output energy of a light emitting diode or the like is used instead of a light source having a high output energy such as a large and expensive solid-state laser oscillator. A low light source 22 can be employed. As a result, the glass dosimeter reader can be reduced in size and cost.

  Further, according to the present embodiment, when the irradiation dose of the fluorescent glass element 10 is small and the fluorescence intensity is weak, the fluorescence amount control unit 70 increases the photoelectrons so that the count value falls within an appropriate range (for example, 1000 or more). Feedback control of the amount of fluorescence incident on the double tube 40 is performed. Then, the irradiation dose is calculated based on the count value falling within the appropriate range. Therefore, it is possible to accurately read a low dose.

  Furthermore, according to the present embodiment, the fluorescence amount control unit 70 gradually increases the amount of fluorescence incident on the photomultiplier tube 40 each time remeasurement is performed. Therefore, the light receiving surface of the photomultiplier tube 40 is not easily damaged. Further, since the count value gradually increases from a small value, the count omission is less likely to occur. Therefore, it is possible to accurately read a high dose.

  As described above, the glass dosimeter reader according to the present embodiment is small and inexpensive, and can accurately read the irradiated dose over a wide range.

[Second Embodiment]
A glass dosimeter reading apparatus according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a partial configuration diagram for explaining the fluorescence amount control unit and the dose calculation unit of the glass dosimeter reader. FIG. 8 is a table showing a correspondence relationship between the count value counted by the counting unit of the glass dosimeter reading device and the passing window determined by the fluorescence amount determining unit. In addition, this embodiment is a modification of 1st Embodiment, Comprising: The same code | symbol is attached | subjected to the same part or similar part as 1st Embodiment, and duplication description is abbreviate | omitted.

  In the present embodiment, at the time of the first measurement (initial setting), the fluorescence amount variable plate 32 is aligned so that the fluorescence 10a emitted from the fluorescent glass element 10 passes through the third passage window 32c. Yes.

  The data transmission unit 72 receives the count value data 66a output from the count unit 66, and transmits the count value data 66a to the remeasurement necessity determination unit 74, the fluorescence amount determination unit 76, and the dose calculation unit 80.

  The remeasurement necessity determination unit 74 receives the count value data 66a and determines whether or not the first count value is within a predetermined range (for example, 1000 or more and less than 10,000). The re-measurement necessity determination unit 74 outputs a calculation instruction signal 74a to the dose calculation unit 80 when the count value is within 1000 or more and less than 10,000.

  On the other hand, the re-measurement necessity determination unit 74 outputs a re-measurement instruction signal 74b to the fluorescence amount determination unit 76 when the first count value is not within 1000 or more and less than 10,000. When receiving the remeasurement instruction signal 74b, the fluorescence amount determination unit 76 receives the count value data 66a based on the correspondence relationship between the count value shown in FIG. 8 and the passage window through which the fluorescence 10a emitted from the fluorescent glass element 10 passes. A passing window corresponding to the count value included in is selected.

  For example, when the count value at the time of the first measurement is 500, the fluorescence amount determination unit 76 determines the passing window through which the fluorescence 10a emitted from the fluorescent glass element 10 passes is the fourth passing window 32d. To do. As a result, the amount of fluorescence incident on the photomultiplier tube 40 at the time of the second measurement is increased compared to the amount of fluorescence incident on the photomultiplier tube 40 at the time of the first measurement, and the count value is also increased. To increase. When the count value at the time of the first measurement is 12000, the passage window through which the fluorescence 10a emitted from the fluorescent glass element 10 passes is determined as the second passage window 32b. As a result, the amount of fluorescence incident on the photomultiplier tube 40 at the time of the second measurement is smaller than the amount of fluorescence incident on the photomultiplier tube 40 at the time of the first measurement, and the count value is also reduced. Decrease.

  According to this embodiment, the irradiation dose is calculated by bringing the count value close to the appropriate range by one feedback control. Therefore, according to the present embodiment, it is possible to shorten the irradiation dose reading time as compared with the first embodiment.

[Third Embodiment]
A glass dosimeter measuring apparatus according to a third embodiment of the present invention will be described with reference to FIG. FIG. 9 is an overall configuration diagram of the glass dosimeter measuring apparatus. In addition, this embodiment is a modification of 1st Embodiment, Comprising: The same code | symbol is attached | subjected to the same part or similar part as 1st Embodiment, and duplication description is abbreviate | omitted.

  In the present embodiment, the fluorescence amount variable unit 30 includes a liquid crystal shutter 38. The liquid crystal shutter 38 is installed on the optical path of the fluorescent light 10a emitted from the fluorescent glass element 10, and is connected to the fluorescent light amount control unit 70 via a cable. The liquid crystal shutter 38 changes the amount of transmitted fluorescence 10 a, that is, the amount of fluorescence incident on the photomultiplier tube 40, based on a control signal from the fluorescence amount control unit 70.

  According to this embodiment, unlike the first embodiment in which the amount of fluorescence incident on the photomultiplier tube 40 is discretely changed, the amount of fluorescence incident on the photomultiplier tube 40 can be continuously changed. .

[Other Embodiments]
The above embodiments are merely examples, and the present invention is not limited to these. In the above embodiment, a light emitting diode is used as the light source 22, but a laser diode may be used. In the above embodiment, the photomultiplier tube 40 is used as the photoelectric conversion unit, but an avalanche photodiode (APD) may be used. Furthermore, the photon counting unit 60, the fluorescence amount control unit 70, and the dose calculation unit 80 may be configured by one or more computers.

  In the above embodiment, the re-measurement necessity determination unit 74 determines whether or not the first count value is within the appropriate range, but whether or not the second count value is within the appropriate range. You may judge.

  In the above embodiment, the noise component removal process is performed by the dose calculation unit 80, but may be performed by the count unit 66. That is, the count unit 66 performs a noise component removal process, and generates count value data 66a including the integrated number of output pulses (that is, the count value after noise removal) caused by the RPL phenomenon. Then, the remeasurement necessity determination unit 74 may determine whether the count value after noise removal is within an appropriate range.

  Further, as the hemispherical lenses 26 and 112 used for condensing and collimating, an aspherical lens or a spherical lens may be used as long as collimated light can be obtained. Similarly, for the hemispherical lens 118, an aspherical lens, a spherical lens, or an optical fiber cable may be used. In the first and second embodiments, four passage windows 32a to 32c are formed on the fluorescence amount variable plate 32, but five or more passage windows are formed to further increase the reading range. You can also.

DESCRIPTION OF SYMBOLS 10 ... Fluorescent glass element, 10a, 10b ... Fluorescence, 20 ... Irradiation part, 20a ... Ultraviolet light, 22 ... Light source, 24 ... Power supply, 26 ... Hemispherical lens, 28 ... Ultraviolet transmission filter, 30 ... Fluorescence amount variable part, 32a-32d DESCRIPTION OF SYMBOLS 1st-4th passage window, 34a-34c ... 1st-3rd neutral density filter, 36 ... Drive apparatus, 36a ... Shaft, 38 ... Liquid crystal shutter, 40 ... Photomultiplier tube, 40a ... Pulse current signal , 42 ... heat sink, 50 ... controller unit, 52, 54 ... cable, 60 ... photon counting unit, 62 ... I / V conversion / amplification unit, 62a ... pulse voltage signal, 64 ... A / D conversion unit, 64a ... digital pulse Signal: 66 ... Count unit, 66a ... Count value data, 70 ... Fluorescence amount control unit, 72 ... Data transmission unit, 74 ... Remeasurement necessity determination unit, 74a ... Calculation instruction signal, 74b ... Recount Instruction signal 76... Fluorescence amount determining unit 76 a .. passing window data 78... Control signal output unit 78 a... Control signal 80... Dose calculating unit 80 a. ... UV removal filter, 112 ... Hemispherical lens, 114 ... Mirror, 116 ... Interference filter, 118 ... Hemispherical lens, 120 ... First case, 120a ... First space in the first case, 120b ... Second in the first case Space 122, first case bottom plate 122 a glass element holding portion 122 b exit window 124 first case top cover 126 partition 126 a slit 128 128 second case 128 a entrance window

Claims (12)

A glass dosimeter reader for reading a radiation dose irradiated to a fluorescent glass element,
An illumination unit that includes a light source that emits ultraviolet light, and irradiates the fluorescent glass element with ultraviolet light;
A fluorescence amount variable section that changes the fluorescence amount by passing the fluorescence emitted by the fluorescent glass element;
A photoelectric conversion unit that detects fluorescence that has passed through the fluorescence amount variable unit and outputs an electrical signal; and
A photon counter that counts the number of output pulses obtained by analog / digital conversion of the electrical signal output by the photoelectric converter;
The radiation dose applied to the fluorescent glass element is calculated based on the number of output pulses counted by the photon counting unit, the amount of change in fluorescence in the fluorescence amount variable unit, and the amount of ultraviolet light applied to the fluorescent glass element. A dose calculator;
A fluorescence amount control unit that controls the amount of fluorescence that is incident on the photoelectric conversion unit by transmitting a control signal to the fluorescence amount variable unit based on the number of output pulses counted by the photon counting unit;
A glass dosimeter reading device comprising:   2. The glass according to claim 1, wherein the fluorescence amount control unit controls the amount of fluorescence incident on the photoelectric conversion unit so that the number of output pulses counted by the photon counting unit falls within a predetermined range. Dosimeter reader.   3. The fluorescence amount control unit according to claim 2, wherein the fluorescence amount control unit increases the amount of fluorescence incident on the photoelectric conversion unit when the number of output pulses counted by the photon counting unit is a predetermined value or less. Glass dosimeter reader.   The said fluorescence amount control part reduces the fluorescence amount made to enter into the said photoelectric conversion part, when the number of the output pulses which the said photon counting part counted is more than predetermined value, The Claim 2 or 3 characterized by the above-mentioned. The glass dosimeter reading device described.   5. The fluorescence amount control unit repeatedly controls the amount of fluorescence incident on the photoelectric conversion unit until the number of output pulses counted by the photon counting unit falls within a predetermined range. The glass dosimeter reader according to claim 1.   The fluorescence amount control unit determines whether the number of output pulses counted by the photon counting unit belongs to one of a plurality of different ranges, and enters the photoelectric conversion unit according to the belonging range The glass dosimeter reading device according to any one of claims 2 to 4, wherein the amount of fluorescence to be controlled is controlled.   The fluorescence amount varying unit includes a neutral density filter, and changes the amount of fluorescence incident on the photoelectric conversion unit by allowing the fluorescence emitted from the fluorescent glass element to pass through the neutral density filter. The glass dosimeter reader according to any one of 1 to 6.   2. The fluorescent light amount changing unit includes a liquid crystal shutter, and changes the fluorescent light amount incident on the photoelectric conversion unit by allowing the fluorescent light emitted from the fluorescent glass element to pass through the liquid crystal shutter. The glass dosimeter reader according to claim 6.   The glass dosimeter reading device according to any one of claims 1 to 8, wherein the light source is a light emitting diode.   The glass dosimeter reading device according to any one of claims 1 to 8, wherein the light source is a laser diode.   The glass dosimeter reading device according to any one of claims 1 to 10, wherein the photoelectric conversion unit is a photomultiplier tube.   The glass photoelectric dosimeter reading device according to any one of claims 1 to 10, wherein the photoelectric conversion unit is an avalanche photodiode.

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