Coincidence Detector for the Geiger SCR Detector

With this circuit you can expand the "Geiger Detector with LED, SCR without low voltage supply" to a muon telescope. In order to detect muons, you need 2 of the SCR detectors and connect those to this coincidence detector. The 2 SCR's of the Geiger-Müller stages are also shown in this schematic. The 2 inputs of the coincidence detector are wired to the anodes of the SCR's (thyristors). Due the similar design as the SCR stages, the whole system is still Cockroft-Walton voltage multiplier (used as power supply which connects directly to mains) safe in respect to current consumption.

If a muon passes thru both Geiger tubes, both SCR's (T1, T2) fire and put the diodes D1 and D2 to ground. This results in a current thru the transistors Q1 and Q2, which allow discharging of capacitor C1 over R3 and the muon LED. The LED flashes. If only one Geiger tube fires, only one transistor is switched on and the LED doesn't light, because the other transistor blocks. When both SCR's T1 and T2 block again, also Q1 and Q2 block and the capacitor C1 is charged again over R1. The voltage over C1 cannot exceed 10 volts, because of the voltage divider with R1 and R2.

Regular coincidence detectors have some sort of pulse widening, but we do not need this here, because pulse widening already happens in the first stages with the SCR's.

Formulae:

Be very careful when handling high voltages!
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