Which detector circuit should I use ?

mode circuit(s) detector alignment comments

muon-flux circuit #1 and #2 above each other circuit #2 does work in "flux-mode",
but circuit #1 is preferred

air-shower circuit #2 side by side

UPDATE 27-MAY-2008:
Oh well, the directional circuit below will not work. A website user, Markus, informed me that the propagation delay of the 74123 is about 30ns, but if the detectors are spaced just 5cm, the flight time of a muon is just 0.16ns. So Q of IC1 goes high after the muon pulse signal is already gone again at input #2.
So do not try this circuit unless you have large detectors which you can space more than 2 meters away. So you would have a muon flight time of >6ns and this can be managed with high speed logic.

UPDATE 03-JUN-2005:
If you want to use the cosmic ray telecope to measure the continous muon flux, place the two detectors above each other. You can use circuit #2 too, but circuit #1 is the preferred detector in the "flux-mode".
NOTE: Circuit #1 is just a draft - it has neither been built nor tested yet!

Retriggerable Directional Coincidence Detector

Directional coincidence detector electronics for the muon detector

Circuit #1 © by Joseph DiVerdi xtrsystems.com and Hannes Mayer cosmicrays.org
This circuit detects the direction of the muon - only if a muon flys thru detector #1 first (the upper detector) and then thru detector #2 (the lower detector) it produces a pulse on the output Q2. This reduces false detection due local radioactivity by 50%, since false detections which occur first in detector #2 and then in detector #1 are not detected.

Different scenarios:
Case #1: Muon strikes detector #1 first and then detector #2. The pulse from detector #1 triggers the 74LS123 mono-flop (Q1) and if there is a pulse from detector #2 within the time of the mono-flop, Q2 goes to high. Q2 is reset to low by the falling edge of the pulse of detector #2.
Case #2: This is the opposite of case #1. The pulse from detector #2 arrives earlier than the pulse from detector #1 and doesn't produce a pulse on the output Q2.
Case #3 and #4: This are special cases of #2 and #1 - the detector pulses overlap.
Case #5: This is the retrigger case - if a second pulse from detector #1 is received before or at the time of the pulse from detector #2, the mono-flop is retriggered and the result is two correctly detected muons on the output Q2.

UPDATE 29-APR-2006:
See the commissioning page for further details!

UPDATE 19-JUN-2004:
The version of the circuit from the SciAm article was removed in favor of this excellent circuit designed by Joseph DiVerdi of xtrsystems.com. If you run the two flat detectors in "air-shower-mode", this is the circuit you want to use. "Air-shower-mode" means that the detectors are placed side by side, so if an air shower occurs, many muons will rain down and if two muons strike the detector simultaneously, one count is registered.

Electronics for the Cosmic Particle Muon Counter

The other electronics, besides the high voltage power supply, is extremely simple.

There are 2 input stages for signal forming, 2 LM555 timer IC's wired as mono-flop in order to stretch the short pulses from the detectors. The NAND gate (pin 4,5,6 of the 4011) compares the signals of the 2 detectors and if both arrive simultaneously, the output goes low and we have counted one muon.

The schematic shows 2 geiger tubes, but this circuit can be used unchanged for the flat homebrew detectors aswell. The values for R and C are subject to experimentation. The longer the time constant T the higher is the probability for false positive detections.

UPDATE 04-MAR-2004:
High voltage supply for the detectors and spike detection circuit

High voltage supply for the detectors and spike detection circuit

There is a much better solution for measuring the voltage spikes, which does not divide the high voltage as in the circuit of SciAm and offers protection to the further circuitry.

The high-voltage supply is connected to the anode of the detectors via a resistor in the MOhm range - the ground-plates of the detectors are connected to ground via a resistor in the kOhm range. So if there is an avalanche in the detector, the current flowing thru it will produce a nice low voltage spike in R1.
R2 and the zener-diode is optional.

Last-Modified: Tue, 27 May 2008 21:10:22 GMT

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Electronics for the Cosmic Ray Muon Detector

Be very careful when handling high voltages!cosmicrays.org cannot be held liable for damage of any sort!

Be very careful when handling high voltages!
cosmicrays.org cannot be held liable for damage of any sort!