JPH0641981B2 - Radiation dose measuring device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation dose measuring device such as a pocket dosimeter or a portable survey meter, which is small in size and used on the body.

2. Description of the Related Art Conventionally, in a dose dosimeter such as a pocket dosimeter or a pocket alarm, a GM tube or an ionization chamber type sensor has been used, and it has been impossible to measure the type of radiation exposed and energy. .

Problems to be Solved by the Invention Although only the exposure dose value has been measured in the measurement of a personal dosimeter or a surveimeter, the exposure environmental management is advanced. There is an increasing demand for measurement of the type of radiation and energy in exposure. The present invention is an apparatus for measuring the average energy of exposure radiation in a small sensor for a personal dosimeter, and using the measured value to notify energy information of exposure radiation and various controls which have been difficult in the past. Is provided.

Means for solving the problem A sensor that outputs a pulse wave height distribution corresponding to the energy of incident radiation is used, and a plurality of pulse wave height discriminators each connected to this are used. Means for calculating the ratio of the number of output pulses is provided, and the average energy of the detected radiation is obtained from the calculated value.

During operation dosimetry, the secondary electron equilibrium state including scattered radiation is measured, so the pulse wave high output of the radiation detected by a small sensor for high-energy radiation is especially high. At the same time as the electron output, a large number of secondary electron signals generated outside the sensor are also included.
The energy distribution of the signal is determined by the material and shape of the sensor and the surrounding material corresponding to the incident radiation. The wave height distribution is a distribution in which the irradiated radiation energy is the maximum energy and the signal due to Compton scattering increases as the energy becomes lower. For this reason, for example, when pulse height discrimination is performed by a two-stage discriminator of high level and low level, a response corresponding to the irradiated radiation energy is performed at each level. This effect is used in the present invention to obtain the irradiated radiation energy value, rather than the ratio of the high level output to the low level output.

Embodiments The present invention can be applied to a proportional counter, a pulse detector by a combination of a scintillator and a photodetector, and a dose measuring instrument and a dose rate measuring instrument using a semiconductor sensor by the pulse detection method. In recent years, semiconductor sensors based on the pulse detection method have been developed for personal dosimeters and have excellent linearity from low dose rates to high dose rates. Si, GaAs, CdTe, etc. have been put to practical use as sensors that do not require cooling, and the present invention can be applied.

FIG. 1 shows an example of implementation of the present invention. The pulse output from the sensor 1 is amplified by the amplifier 2 and the pulse heights are discriminated by the plurality of discriminators 3. In the present embodiment, the number of discriminators 3 is two, but the more discriminators 3 are used, the more complicated the measurement becomes possible though it becomes complicated. The pulse height discriminated output is sent to the next stage for dose display and at the divider 5 a high level output n
Calculate and output the ratio of ₁ to the low level output n ₂ . These circuit configurations are analog circuits, digital circuits,
It can also be carried out by a micro computer. Various calculation timings can be applied for a fixed time and a fixed dose. Figure 4 shows a CdTe semiconductor sensor with a shape of 1 x 1 x 0.3 mm and a Pb shield of 0.8 t (thickness 0.8 mm) added to the periphery, and the output is about 10 KeV and about 150 KeV. It shows low and high discreet characteristics when separated by discreet voltage. In this way, 150 KeV-10M
It can be seen that it shows a measurable response up to eV. By changing the high discreet level to lower energy, 100
It is possible to measure energy below KeV.

FIGS. 2 and 3 show an embodiment of using the output from the calculator 5 illustrated in FIG.

In FIG. 2, a comparator 6 is added to the output of the divider 5 of FIG. In this embodiment, it is possible to partition the information for the output signal in a particular energy range. For example, when the dose is high in high energy radiation, the value of n ₁ / n ₂ increases even if the dose value is the same.
Therefore, if it is desired to prohibit entry to such a case, it is possible to set the value of the comparator 6 in advance. It is likewise possible with low-energy radiation. Further, since the change in energy distribution can be discriminated from the deviation from the predetermined value, it is possible to detect an abnormal situation during a fixed work.

In FIG. 3, a circuit 7 for outputting a constant k corresponding to the force of the division 5 in FIG. 1 is added. The output k-dose measurement value from the circuit 7 is multiplied or divided. In this embodiment, the energy response characteristics of the dosimeter can be adjusted freely, so that the X-ray display, REM display, etc. can be freely performed.

Further, although the present invention can be applied to a sensor material having a low atomic number such as silicon, it is possible to correct the response characteristics depending on the sensor material and the shape, and thus it is conventionally said that it is unsuitable for dosimetry. It is also possible to use sensors of high atomic number materials such as gallium arsenide, cadmium telluride, and mercuric iodide. On the contrary, a high atomic number material will improve the energy separation performance.

The present invention is also applicable to survey meters and area monitors, and enables inexpensive and highly accurate measurement.

Effect of the Invention It becomes possible to evaluate the energy of a small and lightweight personal dosimeter, improve the accuracy of safety management, and reduce the cost of the personal dosimeter.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the radiation dose measuring apparatus which is the basis of the present invention, and FIGS. 2 and 3 are block diagrams showing the configuration of another embodiment of the present invention, and FIG. Is a graph showing the energy response characteristics of the low discretization and the high discretization of the embodiment shown in FIG. 1, and FIG. 5 is a graph showing an example of the pulse output wave height distribution from the semiconductor sensor. 1 ... Sensor, amplifier, 3 ... Pulse wave height discriminator, 5 ...
… Differential calculator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Tsutsui 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-57-29976 (JP, A)

Claims (3)

[Claims] 1. A sensor which outputs a pulse wave height distribution corresponding to the energy of incident radiation is used, and a plurality of pulse wave height discriminators respectively connected to the sensor are used, and the number of output pulses from this pulse wave height discriminator is used. A radiation dose measuring apparatus having means for calculating a ratio of 2. The radiation dose measuring device according to claim 1, wherein the sensor is a semiconductor sensor. 3. The radiation dose measuring device according to claim 2, wherein the semiconductor sensor material is any one of silicon, gallicum arsenide, cadmium telluride, and mercuric iodide. .