The picture below shows the Geiger counter prototype for our weather balloon experiment to measure the cosmic radiation in different altitudes: The Geiger counter weighs only 41 g and draw just 10 mA at 5 V. The Geiger tube has a mica window for alpha radiation. To test the Geiger counter we used americium-241 from a dismantled ionization smoke detector. Americium-241 is a so called alpha emitter and has a half-life of 432 years. About one percent of the emitted radioactive energy of ²⁴¹Am is gamma radiation. Geiger counter circuit diagram Test video: