In our age of man-made disasters, it is necessary to protect ourselves from their consequences in the form of radioactive contamination. And for this, ionizing radiation must be detected. Therefore, in the absence of industrial devices, any radio amateur can try to make a Geiger counter with his own hands.
What is a Geiger counter?
To measure the radioactive background, scientists and engineers have developed devices - Geiger counters. As a sensor for alpha, beta and gamma radiation, a sealed gas discharge tube filled with a mixture of inert gases is used, named after the inventors of the Geiger-Muller counter. But professional devices are not easily accessible to the modern layman and are quite expensive.
Several varieties of such structures have been developed. DIY Geiger counter from a neon lamp can make even the most unprepared stalker for survival in a post-apocalyptic world.
Varieties of improvised designsGeiger counters
The Geiger counter has been developed and manufactured by many amateur designers with their own hands. There are many design options. The most common home-made development schemes are known:
- Radiometer, using a fluorescent or neon starter as a beta and gamma sensor.
- A simple homemade radiation indicator based on the STS-5 sensor.
- The simplest dosimeter with a sensor SBM-20.
- Small-sized radiation indicator based on SBT-9 sensor.
- Indicator of ionizing radiation based on a sensor from a semiconductor device - a diode.
- The simplest radiation indicator with a homemade discharger made from a PET bottle and a can.
Advantages and disadvantages of designs
The designs of self-made dosimeters and radiation indicators using sensors SBM-20, STS-5, SBT-9 are quite simple and have high sensitivity. But they have a very important drawback - they are industrial sensors of ionizing radiation, which are difficult to access and expensive to buy.
A radiation indicator with a semiconductor device sensor is cheap, but due to the non-linearity of semiconductor characteristics, it is difficult to set up, sensitive to changes in temperature and supply voltage.
The device with a homemade sensor from a PET bottle is extremely simple, but requires a circuit with a field effect transistor, which is not always available to a DIYer. In addition, field-effect transistors are prone to breakdown under strongradiation.
The most affordable are designs with starter-based sensors from faulty fluorescent or neon lamps. The disadvantages of a sensor from a starter, like a neon lamp, include sensitivity to changes in temperature and supply voltage, the need to shield the sensor from light and electromagnetic radiation. The advantages include the ease of making and setting up a Geiger counter with your own hands.
Scheme of a radiation indicator with a neon lamp as a sensor
Making a Geiger counter with your own hands should begin by studying the circuit diagram of the device. This circuit uses a neon bulb as a gamma and beta sensor.
Let's consider the circuit diagram.
Diode D1 is used to rectify alternating current. To provide a constant voltage of 100 V, a stabilization circuit based on a zener diode D2 was used. The parameters of the resistor R1 are dependent on the supply voltage Vac and are calculated using the formula
R1=(Vac-100V)/(5mA).
Variable resistance R2 sets the voltage on the neon bulb slightly below the ignition voltage. The neon lamp in the standby mode should not be lit. When radioactive particles fly through a glass bulb, the inert gas ionizes and the lamp flashes.
At the moment the lamp flashes, a voltage drop will occur on the resistance R3, and a neon lamp willvoltage, less than holding voltage. There will be no current flow on the lamp until it is ignited by an ionizing particle. At the moment of a short current flow through the lamp, a loud click will sound in the loudspeaker. After assembling a Geiger counter with your own hands from a neon lamp, you can start setting it up.
Setting up and calibrating the Geiger counter
The developed model of the post-apocalyptic Geiger counter is easy to set up with your own hands. With a variable resistance R2, the device is put into standby mode, on the verge of triggering a sensor from a neon lamp. Further, for the experiment, a dusty rag approaches the indicator of radioactivity and the sensitivity of the device is adjusted by the regulating resistor R2. Since the dust is full of radioactive isotopes, the neon indicator of radioactivity should flash periodically when properly adjusted, the speaker head should make chirping sounds and clicks.
For a more accurate calibration of the device, you must use an available radiation source. It can be a toggle switch from military radio equipment with a luminous radioactive phosphor applied to it. Calibration is carried out using an exemplary standard dosimeter. The frequency of operation of a homemade Geiger counter is adjusted to the frequency of counting the radiation level of an industrial dosimeter. For calibration, a standard radiation source, which is usually equipped with a military dosimeter, can also be used.
Materials and tools for assembling a Geiger counter
When assembling a Geiger counter with your own hands, materialsany available to a radio amateur can be used. The main thing is that the ratings of the radio components correspond to the above diagram. It is necessary to correctly select a neon lamp as a sensor so that the ignition voltage approximately corresponds to 100 V. In this case, radio components can be both imported and domestic. The parameters of the parts must be selected using the reference literature.
It is important to note that in the given circuit diagram, an alternating supply voltage from the mains Vac \u003d 220 V is used according to a transformerless circuit, and this is dangerous for electric shock to the body. To prevent electrical injury, the body of the device should be made of electrically insulating material. For this purpose, plexiglass, getinax, fiberglass, polystyrene, and other laminates are suitable.
When assembling a Geiger counter with your own hands, the most diverse tool is used:
- A 60W electric soldering iron is required for soldering radio components.
- Hacksaw is widely used for cutting foil fiberglass, in the manufacture of printed circuit boards. It is used for cutting and cutting plastic body parts.
- The electric drill is used for drilling holes in the printed circuit board, assembling the case on the corners.
- Tweezers are essential for working with small parts when soldering and mounting an electrical circuit.
- Side cutters are recommended for cutting protruding leads of radio components.
- For the commissioning of the device, an elementary tester is absolutely necessary, with which you will needtake voltage measurements at test points, as well as other electrical parameters.
- For an autonomous power supply of a truly post-apocalyptic Geiger counter, it is advisable to connect a 4.5-9 V battery, for which use any simple voltage converter circuit up to 220 V AC.
Safety must be followed when working with electricity and radioactive materials.
