Dirt Cheap Muon Detector Puts Particle Physics Within DIY Reach

Subatomic physics is pretty neat stuff, but not generally considered within the reach of the home-gamer. With cavernous labs filled with racks of expensive gears and miles-wide accelerators, playing with the subatomic menagerie has been firmly in the hands of the pros for pretty much as long as the field has been in existence. But that could change with this sub-$100 DIY muon detector.

[Spencer Axani] has been fiddling with the idea of a tiny muon detector since his undergrad days. Now as an MIT doctoral candidate, he’s making that dream a reality. Muons are particles that are similar to electrons but more massive and less likely to be affected by electromagnetic fields. Muons rain down on the Earth’s surface at the rate of 10,000 per square meter every minute after being created by cosmic rays interacting with the atmosphere and are capable of penetrating deep into the planet. [Spencer]’s detector is purposely kept as low-budget as possible, using cheap plastic scintillators and solid-state photomultipliers hooked up to an Arduino. The whole project is as much STEM outreach as it is a serious scientific effort; the online paper (PDF link) stresses the mechanical and electronics skills needed to complete the build. At the $100 price point, this build is well within the means of most high school STEM programs and allows for a large, distributed array of muon detectors that has the potential for some exciting science.

We’ve covered quite a few subatomic detection projects before, from the aforementioned large-scale builds to more modest efforts. But we like this project because it has the potential to inspire a lot of citizen scientists.

Thanks for the tip, [deralchemist]

31 thoughts on “Dirt Cheap Muon Detector Puts Particle Physics Within DIY Reach

    1. … Maybe. CRAYFIS is an interesting idea, but camera sensors are so ungodly small that really, your active area is pathetically tiny. These guys are around ~25 square cm, which is huge compared to that single smartphone.

      Using an Arduino is really a mistake for this in my mind, though – the thing screams out for using an ESP8266, a cellphone battery and standalone firmware to make large arrays of them trivial.

      1. You would never have had that great idea if it wasn’t for a researcher using an Arduino. For someone new to electronics, an ESP8266 is several difficulty levels higher. Arduino helped create a cheap prototype, that is now ready to be refined. That is the opposite of a mistake, this is an ideal use case for an Arduino.

      1. So you are saying that muons only come to earth tangentially to the surface ? I don’t think so. I do not see anything logically wrong with turning the device on its side and using it to extremely slowly analyse density. By moving it in two dimensions, extremely slowly, along the inside of one external wall of your house.

  1. It would seem that the <$100 price is a little of a misnomer.
    The $100 price can be reached, only if someone purchases 100 C-Series 60035-SMT SensL SiPM at a time, and passes the savings to 99 others.
    "At the time of writing this paper, the unit price of a bulk purchase of 100 SiPMs was below $50/SiPM."
    See page 5 of https://arxiv.org/pdf/1606.01196v3.pdf.

    Sounds like an opportunity.

  2. The detectors are not directional, so heavy (very heavy) shielding of proper design would be required to make it work in a directional manner. The device requires careful pulse amplitude discrimination to eliminate false signals from photons, and proper shielding to eliminate other charged particle detection. To properly discriminate muons in this manner, two or more detectors would be required with coincidence detection as Dave said.

    1. A muon is going to dump a huge amount of energy into this detector. Even though SiPMT has a pathetic active area compared to a regular old vacuum PMT, it will still see 100s of photo-electrons worth of signal. I bet even without any additional gain and with a proper threshold you can be reasonably sure that you are only counting muons. It can be easily verified if you compare your measured rate to the nominal muon flux for your elevation. If you really want to make this cheap, use two Geiger tubes on top of each other and look for coincidence.

  3. You are very welcome :)
    I stumbled upon this nice article on symmetriemagazin.com while I searched for pictures, which I could use for a scientific poster. The website symmetriemagazin.com is well detailed and explains particle physics with ease, it is worth to have a greater look at it ;)

  4. Given the economy of scale when purchasing parts in quantity, perhaps someone will do what the QRP Guys are doing for ham radio kits:

    “QRPGuys is an organization of hams that offers budget and unique ham radio kits. Our specialty will be low cost, high enjoyment kits for the builder that can be assembled in an evening or two. The criteria for our kit designs, are items that are unique in some way, combine features not normally seen, low in cost, and provide satisfaction in completion.”


    Sell a kit for this muon detector with all the parts that can’t be scrounged up locally. That could apply to many of the projects that appear on Hack a Day.

    –Mike Perry KE7NV/4

    1. The biggest problems I see with parts is the SiPM and the Scintillator. The rest can be easely sourced by using aluminium enclosures that seal well. Something like aluminium weatherproof enclosures.

      Maybe offer two at reduced price with an aluminium plate in between for the people that want to do coincidence detection.

  5. Would it be possible to “fake” a SiPM with a bunch of PiN photodiodes like the BPW34 and resistors. The architecture of the SiPM resembles this but as they are all on a single die, the matching is very good. You would need to buy the BPW34 in bulk and match them by dark current at a set bias.

    10 BPW34 cost 5USD from ebay.

    This seems like a interesting project but the SiPM seems to hard to get at decent prices. Has anybody found a vendor that sells single devices?

  6. I played a lot with a similar design before at university, it’s a lot of fun indeed! If it has dual scintillator plates or even better triple ones it can be put a different angles for example to see the direction dependence of the charge particles generated in the atmosphere. It works since the decay time of the particles is such that the difference in path length through the atmosphere is measurable.

    A lot of fun can be had by analyzing the data at different angles, heights, over time…etc. Gives you a lot more information than one might have thought a otherwise very simple instrument. I really recommend the interested to build one, there are several designs out there available if one google a bit.

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