Vermes
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It is a detector which allows you to detect alpha particles in the air at atmospheric pressure. It consists of two parallel electrodes: one in the form of metal sheet and the second made of thin wires. This kind of detector can be used for measuring the activity of radioactive elements in alpha range.
How it works:
During the operation of the detector, high pressure is applied to the electrodes (a little under the breakdown voltage). Active area of the detector is near the wire electrodes. Alpha particles passing through the area cause a sufficiently large number of free charges to come to avalanche (electrical) breakdown. As a result, the alpha particle leaves a trace in the detector in the form of a spark, which is audible and visible by the naked eye.
Construction of the power supply– electronic part:
Regulated power supply should provide about 4-5kV at the output. Current efficiency of the power supply should be large enough so that it can keep the current coming from the corona discharge. The power supply uses converter CCFL (about 1kV at the output) at the input of which there is a regulated voltage stabilizer (LM317). Voltage from the converter is increased by a four-stage power multiplier. The whole is powered from 12V. Construction with linear stabilizer is very simple. Large current (0,6A) passes through the stabilizer, so the device requires a heat sink. It is better to use a decreasing pulse stabilizer. Diodes operating in the voltage multiplier should be quick enough and withstand high barrier voltages of at least 1,5kV. It can be „GP02-20”.
Detector:
The most important thing is the diameter of wires. They should be very thin, otherwise the device will not work at all. This design uses tungsten wires with a diameter of about 0,1mm. Another important factor is the smoothness of construction, lack of bends of the wire or scratches on the plate. That facilitates greatly the voltage regulation.
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