KR100353047B1 - Real-time small size dosimeter for high dose gamma-ray using Power pMOSFET - Google Patents

Abstract

The present invention relates to a high-level radiation-type γ-ray small-scale dosimeter using a power pMOSFET, and an object thereof is to accumulate a radiation sensor and a high-level range of 100 KRad using a power pMOSFET having linear sensing characteristics for γ-radiation exposure in the range of 1 KRad and 100 KRad. It consists of electronic circuits that are not affected by radiation exposure at all, and provides a radiation exposure measurement dose meter that can prevent failures and malfunctions caused by radiation exposure of devices and equipment used in high radiation areas and predict their lifespan.

The configuration of the present invention comprises a cumulative sensor (1) made of a pMOSFET linearly increases the threshold voltage value in accordance with the radiation dose of the radiation dosimeter for detecting a radiation; In order to measure the threshold voltage of the cumulative sensor 1, the JFET-1 (2) and the JFET-2 which constantly supply the small current generated by the small potential difference generated between the gates to the drain electrode of the Power pMOSFET (1). (3); It is a main point that the circuit is composed of only the variable resistor 4 which adjusts the supplied current according to the type of pMOSFET.

Description

Real-time small size dosimeter for high dose gamma-ray using Power pMOSFET}

The present invention relates to a high-level radioactive γ-ray small-scale dosimeter using a power pMOSFET, and in particular, a radiation accumulation monitoring device for predicting failure and life expectancy due to radiation exposure of primary equipment and high-level radiation environment work equipment in a nuclear power plant. It can also be used for measuring the distribution of cosmic radiation in satellites and spacecrafts, and for research on cosmic radiation shielding.

Equipment and work robots in high-level radiation areas are exposed to serious damages due to radiation exposure, and if exposed above the standard value, malfunctions and failures will occur. In order to prevent this in advance, these devices and devices are monitored in real time by accumulating the radiation values exposed to them, and when the withdrawal of work equipment or replacement of devices and equipment in a high-radiation environment immediately before the threshold is reached, Not only can it be prevented, but vice versa, it can also reduce the economic loss of replacing it before its lifetime.

Since the radioactive lifespan of high-radiation devices and equipment and mobile robots is set to a maximum threshold of 100 KRad, it is necessary to develop a radiation-resistant dosimeter that indicates the accumulated high-level radioactivity up to this range in real time.

However, conventional dosimeters using semiconductors have a low radiation range of 1 KRad or less for the purpose of personal dosimeters, and there is a problem in that manufacturing cost is high using expensive pMOSFETs specially manufactured for radiation detection.

Fig. 2 shows a circuit diagram showing an embodiment of a conventional dosimeter using a pMOSFET, which is composed of a cumulative sensor and an amplifier using a pMOSFET.

However, this general MOS channel is formed in the horizontal direction, only a small current flows horizontally, and such a dosimeter is used in a high level radiation region because a device for making a constant current is made using an amplifier, which is weak to radiation, as shown in FIG. There is a problem that causes a malfunction.

An object of the present invention for solving the above problems is that the electron is not affected at all by the radiation accumulation sensor using the power pMOSFET having a linear sensing characteristic for the γ radiation exposure in the range of 1 KRad and 100 KRad and the high level radiation exposure in the 100 KRad range It consists of a circuit only to provide a dosimetry for radiation exposure measurement that can prevent failures and malfunctions caused by radiation exposure of devices and equipment used in high radiation areas and predict their lifespan.

1 is an internal structure and a circuit diagram of a high radiation gamma ray real-time dosimeter using the Power pMOSFET of the present invention.

2 is a circuit diagram showing an embodiment of a dosimeter using a conventional pMOSFET.

<Description of the symbols for the main parts of the drawings>

(1) Accumulation sensor (2) JFET-1

(3) JFET-2 (4) Variable resistor

When described in detail with reference to the accompanying drawings, the configuration and the operation of the embodiment of the present invention to achieve the object as described above and to perform the task for eliminating the conventional drawbacks.

The high-radiation γ-ray real-time small dosimeter using the present invention power pMOSFET having the structure as shown in FIG. 1 has a radiation accumulation sensor 1 using a power pMOSFET having a linear sensing characteristic with respect to γ-radiation exposure in the range of 1 KRad and 100 KRad. The MOSFET consists of an electronic circuit composed only of a JFET-1 (2) JFET-2 (3) and a variable resistor (4) element that is resistant to radiation, which is not affected by the high level radiation exposure in the 100 KRad range. An abbreviation for Field Effect Transistor (hereinafter referred to as "MOSFET"), a transistor that uses the effect of an electric field to control a passage of current by applying a voltage to a gate electrode electrically insulated by an oxide film, and is widely used in a switching or amplifying circuit. JFET is an abbreviation for Junction Field Effect Transistor (hereinafter referred to as "JFET") and refers to a junction field effect transistor. A function of controlling the amount of current passing by adjusting the intensity of the reverse bias voltage applied to the electrode, and is mainly applied to the amplification of a switch or signal.

As shown in FIG. 1, a general commercially available power pMOSFET, which has never been used previously, can be used as a γ-radiation accumulating sensor 1, and thus it can be realized as a sensor exhibiting an excellent linear value for the cumulative radiation in high-level radiation regions ranging from 1 KRad to 100 KRad. Was done.

Power pMOSFET, a device used as a switch or an amplifier in a large power circuit, can overcome the disadvantages of leakage current and charge accumulation at the interface by forming a channel for flowing current in a vertical direction rather than a horizontal direction like a conventional pMOSFET. It has the advantage of being.

In order to extract the exposure radiation value up to 100KRad, the circuit constituting the dosimeter should also have no influence on the radiation, and it is advantageous to use only the minimum components for the small size and light weight.

For this purpose, the constant current circuit required to extract the output voltage (threshold voltage) of the power pMOSFET is optimized by implementing only the JFET-1 (2), JFET-2 (3) and the variable resistor (4) which are very resistant to radiation. The advantages of the JFET used above for radiation to MOSFETs are as follows: In terms of electrical characteristics, MOSFETs and JFETs have similar functions, but MOSFETs are in contact with the gate electrode. While sensitive to the effects of radiation due to the presence of, JFETs without oxide layers are relatively resistant to radiation, which is why OP-amps consisting mainly of MOS are also very vulnerable to radiation. By replacing all of the MOS and op amps consisting of JFETs, the circuit's radiation resistance can be improved by re-implementing the entire function of the circuit.

Hereinafter will be described the operation of the present invention.

When the dosimeter of FIG. 1 is put into a high radiation area, all elements constituting the dosimeter are exposed to radiation.

At this time, since JFET-1 (2), JFET-2 (3) and variable resistor (4) are radiation-resistant devices, there is almost no change in characteristics, but relatively weak power pMOSFETs are physical and electrical characteristics depending on the radiation dose. Will change.

One of these changing characteristics, the pMOSFET threshold voltage, shows a characteristic that the value increases linearly with the radiation exposure.

Therefore, this voltage can be provided to the control panel of the remote robot so that the radiation dose to be exposed can be observed in real time from the remote site.

In order to measure this threshold voltage, a small constant current must be supplied to the drain electrode of the pMOSFET, and this current must be maintained at a constant value without affecting the output voltage of the pMOSFET.

To this end, in FIG. 1, a small current generated due to a small potential difference between the gates of JFET-1 (2) and JFET-2 (3) can be constantly supplied to the power pMOSFET. The variable resistor 4 can be adjusted.

In addition, although the detection radiation of the present invention not only restricts γ-rays but also responds to other radiations, it mainly reacts to gamma rays, and since the working area of the mobile robot mainly emits gamma rays, only the γ-rays are mainly described. It is a matter of course for those with knowledge.

Hereinafter, the difference between the present invention and the prior art will be described.

First, in comparison with the conventional patent Solis State Dosimeter (US, 4,757,202), the present invention implements a dosimeter circuit using only a JFET and a variable resistor, so the radiation dosimeter is a dosimeter for detecting high-level radiation (1 KRad to 100 KRad). It is different from the conventional patent in that it consists only of the element which resists radiation.

In addition, when compared with the conventional patent Direct Reading Dosimeter (US, 4,484,076), the present invention implements a commercially available power pMOSFET as a radiation accumulation sensor, and has a high level using a power pMOSFET having fewer disadvantages than a general MOSFET due to vertical channel formation. It is different from the conventional patent in that it is a radiation dosimeter.

And compared to Graham ENSELL, etc. "Thick Oxide pMOSFET Dosimeter for High Energy Radiation," Nuclear Instruments Methods in Physics Research, 1988, 655-658, a technique in references and journals, In contrast to the radiation dosimeter having a linear characteristic up to 10 KRad per person, the present invention is a high-level radiation dose (˜100 KRad) dosimeter, which uses a general power pMOSFET, and has excellent linearity.

See also J. R. Schwank, S. B. Roeske, etc, "A Dose Rate Independent pMOSFET Dosimeter for space Application," IEEE Transactions on Nuclear Science, Vol. 43, No. 6, compared with 1996, the prior art is a dosimeter using a pMOSFET fabricated for radiation detection, but responds to radiation up to 100KRad region, but the linearity is maintained only up to 20KRad, whereas the present invention is up to 100KRad even if 20KRad or more There is a difference in that linearity is maintained well and commercial devices are implemented as high-level radiation dosimeters without developing expensive devices.

As described above, the present invention does not develop and use a specially manufactured expensive sensor, but uses a commercial power pMOSFET, and economically and vertically forms a channel to flow a large current so that the radiation detection value is excellent linearity up to 100 KRad, which is a high level radiation. It is a dosimeter that has the advantage of being sensed in real time and has the advantage of simply consisting of a strong JFET and variable resistance even when the device constituting the circuit is exposed to radiation.It is a field of high-radiation work, nuclear fuel waste treatment, space radiation environment, nuclear power plant It can be used as a cumulative monitoring device for radiation exposure in order to predict in real time the lifespan of damage caused by radiation exposure of primary equipment and equipment for high-radiation environment work.

Claims (2)

In constructing a dosimeter for detecting radiation, A cumulative sensor 1 made of a p Metal Oxide Semiconductor Field Effect Transistor (pMOSFET), in which a threshold voltage value increases linearly with the radiation dose; In order to measure the threshold voltage of the cumulative sensor 1, a junction field effect transistor (JFET) -1 (1) which constantly supplies a small current generated due to a small potential difference between gates to the drain electrode of the power pMOSFET 1 2) and Junction Field Effect Transistor (JFET) -2 (3); A real-time small dose dosimeter for high-level radiation using a power pMOSFET, characterized in that the circuit is composed of only a variable resistor (4) for adjusting the supplied current according to the type of pMOSFET. The γ-ray real-time compact dosimeter for high level radiation using a power pMOSFET according to claim 1, wherein the pMOSFET uses a commercially available Power pMOSFET having a radiation detection range of 1 to 100 KRad.