Cosmic Ray – Raspberry Pi Geiger Counter

Forums Radio Astronomy Cosmic Ray – Raspberry Pi Geiger Counter


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    Nick Francis

    Newbie here.
    Inspired by the RA section chaps at Astrofest I put together a Gieger Counter using a “cheap” GM tube and Raspberry Pi.
    Leaving the counter on for days I see an average count per minute of 25. The plot attached shows a few hours. There is a noise of a few CPM all time, but then a larger (but not huge) variation over minutes/hours.
    Interested to know if this larger variation is just a ‘random noise’ variation as well, maybe due to electronics or other external factors, or indeed actual cosmic ray events/levels changing during day?
    I realise a GM tube not ideal detector plus a Coincidence setup better, but just interested to know if can infer anything more from the variations and variation profiles, from a cosmic ray point of view with a simple setup like this?

    David Strange

    Hello Nick,

    We recently setup a Muon detector at Norman Lockyer Observatory:

    But I’m not the best person to ask as to what it all means!
    It shows a fairly regular detection rate at present, I guess when we get past the next solar maximum, rates will increase?

    Dr Paul Leyland

    Muons have a rest mass of 106 MeV and are created by collisions in the Earth’s atmosphere. Their half-life is 2.2 microseconds, which is 600 metres at the speed of light. From that you can immediately deduce that any muons you detect are travelling fast enough for relativistic time dilation to be very significant. If one is created in the upper atmosphere, at 60km say, the time dilation needs to be a factor of 10. Their relativistic mass increases by the same fraction, so to create a muon in the centre of mass frame requires 1.06GeV. If an anti-muon is also created, as opposed to an anti- muon neutrino, double the energy budget. Now throw in conservation of momentum; the recoiling nucleus will also carry off a chunk of energy.

    To the best of my knowledge, very few particles in the solar wind have kinetic energies of well over 1 GeV. I would be astounded if there is any noticeable variation with the solar cycle.

    (All figures above rounded.)

    Dr Paul Leyland

    Sorry. An OOM error. 60km/600m is a factor of 100, not 10 as given. It makes my argument even more forceful.

    David Strange

    It looks like powerful CME’s are able to block cosmic rays from striking our atmosphere: From The Forbush Decrease – As solar activity increases, more and more CMEs billow away from the sun, pushing cosmic rays out of the inner solar system. This is one reason we expect cosmic radiation to subside in the years ahead as young Solar Cycle 25 intensifies.So there does appear to be a link with the Solar Cycle?


    Dr Paul Leyland
    Participant is a fascinating paper. A number of periodicities in muon flux are detectable. A strong signal with a periodicity of 125 days is found, along with a diurnal variation and one which correlates well with the temperature of the Earth’s atmosphere. The global magnetic field of the Sun influences the muon intensity and shows up as a 27 day variation.

    However, another variation of about 64 days appeared at two solar maxima (but not all of them). I find this surprising!

    Mr Ian David Sharp

    My years ago, when I was a Physics undergraduate, we were shown this marvellous film (projected on film of course).

    Stephen Cookson

    So should it be 10 GeV, then?



    What a nice little high-voltage supply you have built for your GM tube! A few years ago I built a little muon detector to the MIT design (which seems to have morphed into the Cosmic Watch detector). It uses a silicon photomultiplier and a scintillator block and is controlled by an Arduino Nano. I have attached a picture, just to show off. I always get counts of around 17.5 per minute, a bit less than you do, and not much variation during the day.

    Dr Paul Leyland

    What a nice little high-voltage supply you have built for your GM tube!

    What voltage is required? I ask because I had to replace my fly-zapper recently. The blue-through-UV LEDs had died but the 4kV power supply still works fine. Perhaps it could be re-purposed.

    I am also tempted to build a spark chamber. Lots of fine wires across a cube about 1m in each dimension with each wire being just higher than the breakdown voltage of undisturbed air. Such a beast shows muon tracks very nicely. Elfin safety dictates that the whole be encased in something like Perspex sheets to keep sensitive bodily parts away from the zappy things.


    Sorry, Nick, I can’t do simple arithmetic!
    I typically detect muons at a rate of ~0.058 per sec = 3.5 per min, i.e. at intervals of ~17.5 sec, on average. The plastic scintillator is 25 x 25 x 100 mm.

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