Machinery

How to make a radiation dosimeter with your own hands: 3 basic schemes

October 1, 2019

Measurement of the level of radioactive background is carried out using a special device - a dosimeter. It can be purchased at a specialty store, but home craftsmen will be attracted by another option - to make a dosimeter with your own hands. Household modification can be assembled in several variations, example, from improvised means or with installation of the SBM-20 counter.

Possibilities of the self-made device

Naturally, a professional or multifunction dosimeter will be quite difficult to assemble. Household portable or individual devices register beta or gamma radiation. The radiometer is designed to study specific objects and read the level of radionuclides. In fact, a dosimeter and a radiometer are two different devices, but household versions often combine the former, and the second. Fine terminology only plays a role for professionals, therefore, even combined models are called in general - a dosimeter.

Selecting one of the proposed schemes for assembly, the user will get a simple device with low sensitivity. The benefit of such a device is still there: it is able to record critical doses of radiation, this will indicate a real threat to human health. Though, that the self-made device at times concedes to any household dosimeter from shop, it can be used to protect one's own life.

Tips

Before, how to choose one of the assembly schemes, read the general recommendations for the manufacture of the device.

  1. For the device of own assembly choose 400 volt counters, if the converter is designed for 500 volt, then you need to adjust the feedback circuit setting. Suppose you choose a different configuration of zener diodes and neon lamps, looking, what dosimeter scheme is used in the manufacture.
  2. The output voltage of the stabilizer is reconciled with the voltmeter with the input resistance from 10 Mom. It is important to check, that it is actually equal to 400 volt, charged capacitors are potentially dangerous to humans, despite the low power.
  3. Near the meter in the case are several small holes for the penetration of beta radiation. Access to high voltage circuits must be excluded, this must be taken into account, when installing the device in the case.
  4. The scheme of the measuring unit is selected on the basis of the input voltage of the converter. Connection of knot is carried out strictly at the disconnected food and the discharged accumulative condenser.
  5. At a natural radiation background the self-made dosimeter will give out approximately 30 — 35 signals for 60 seconds. Exceeding the rate indicates high ionic radiation.

Scheme №1 - elementary

To design a detector to detect beta and gamma radiation "quickly and easily", this option is best suited. What you need to design:

  • plastic bottle, or rather - a neck with a lid;
  • can without lid with trimmed edges;
  • ordinary tester;
  • a piece of steel and copper wire;
  • transistor kp302a or any KP303.

To assemble, you need to cut the neck from the bottle in this way, so that it fits tightly into the can. Narrow is best, high bank, as from condensed milk. Two holes are made in the plastic lid, where to insert the steel wire. One of its edges is bent with a loop in the form of the letter "C", to hold it securely by the lid, the other end of the steel rod should not touch the jars. After the lid is tightened.

The leg of the gate KP302a is screwed to the loop of steel wire, and tester terminals are connected to the drain and leak. You need to wrap copper wire around the jars and fasten one end to the black terminal. The whimsical and short-lived field-effect transistor can be replaced, example, connect several others according to Darlington's scheme, the main thing is that the total gain should be equal to 9000.

The self-made dosimeter is ready, but it needs to be calibrated. To do this, use a laboratory radiation source, usually, it indicates the unit of its ionic radiation.

Scheme No. 2 - installation of the meter

For, to assemble the dosimeter with your hands, the usual SBM-20 counter will approach - it should be bought in specialized shop of radio components. An anode - a thin wire - passes through the sealed cathode tube along the axis. The interior space is filled with gas at low pressure, which creates the optimal environment for electrical breakdown.

Voltage SBM-20 is close 300 — 500 V, it must be configured as follows, to exclude arbitrary breakdown. When a radioactive particle enters, it ionizes the gas in the tube, creating a large number of ions and electrons between the cathode and anode. In a similar way, the counter works for each particle.

It is important to know! Any meter will be suitable for the self-made device, designed for 400 volt, but SBM-20 is the most suitable, you can buy the popular STS-5, but it is less durable.

The dosimeter circuit has two blocks: indicator and network rectifier, which are collected in plastic boxes and connected by a connector. The power supply is connected to the mains for a short period of time. The capacitor is charged to voltage 600 W is the power source of the device.

The unit is disconnected from the mains and from the indicator, and high-impedance telephones are connected to the connector contacts. The capacitor should be of good quality, this will extend the operating time of the dosimeter. The self-made device can function during 20 minutes and more.

Technical features:

  • the rectifier resistor is optimally matched with power dissipation up to 2 W;
  • capacitors can be ceramic or paper, with the appropriate voltage;
  • you can choose any counter;
  • eliminate the possibility of hands touching the resistor contacts

Natural radiation background will be recorded as rare signals in phones, lack of sounds means, that there is no food.

Scheme No. 3 with two-wire detector

You can design a homemade dosimeter with a two-wire detector, this requires a plastic container, through capacitor, three resistors and a single-channel damper.

The damper itself reduces the amplitude of oscillations and is installed behind the detector, directly next to the bushing capacitor, which measures the dose. Only resonant rectifiers are suitable for this design, but expanders are practically not used. The device will be more sensitive to radiation, but will require more time to compile.

There are other schemes, how to make a dosimeter yourself. Amateurs have developed and tested many variations, but most of them are based on schemes, described above.