spaceSpace and Physics

Graduate Student Designs $100 Pocket-Sized Muon Detector


Robin Andrews

Science & Policy Writer

The new muon detector - for the low, low price of $100! Katarzyna Frankiewicz/National Center of Nuclear Research in Warsaw/MIT

The muon is a rather funky little subatomic particle. It’s very similar to the electron, but it’s got a much greater mass – and it’s often found escaping particle accelerators or collisions between cosmic rays and our atmosphere. Recently, they’ve been used to discover hidden voids within Egypt’s famous pyramids.

All in all, they’re extremely useful, and they can tell us a lot about the universe and the world around us. In order to do this, though, we need muon detectors, and a team at MIT have just made a pocket-sized one that costs just $100.


This is no small feat. Muons are incredibly unstable, and despite the fact that they’re everywhere around us right now, they exist only for a fraction of a second. Only extremely high-tech detectors have been able to accurately pick them up to date, but a graduate student at MIT’s Department of Physics clearly had other ideas.

Students, after all, need to detect muons too, not just any fancy schmancy research fellow or astrophysics professor. That’s why Spencer Axani and his team have set up CosmicWatch, a website that details how to build a muon detector of your own for that unfathomably low price.

So what’s actually inside this miraculous, MacGyver-esque device? A little warning: You may need some basic electrical engineering experience to build your device, but considering that the team’s schematics have helped supply nearly 100 detectors to college and high school students up and down the country and even around the world, you know they can’t be too terrifying.

Katarzyna Frankiewicz/National Center of Nuclear Research in Warsaw/MIT

Generally speaking, the device is made of various printed circuit boards, screws, wires, and other common electronic items. It runs on a simple python program, a basic computer code language. Somehow, when it’s all put together, all it needs to run is a USB connection.


One of the key components is a scintillator slab, a material that exhibits luminescence when excited by ionizing radiation. Every time a muon hits the device, it generates a small current, which the scintillator slab then amplifies so that the onboard programming registers its existence.

Muons only exist for a few microseconds, and they interact with dense matter - which makes them particularly difficult to detect. GiroScience/Shutterstock

A full list of instructions can be found here. Details of the device can also be found in the American Journal of Physics, where the design for the prototype was first espoused.

Muons are interrupted by dense matter, which is why the best place to detect them is high up. That’s why some have already been sent skywards on weather balloons to test their accuracy – and the CosmicWatch site encourages people to “climb a mountain” with one of them.

“For now I like to take these detectors in my briefcase and measure the muon rate when I'm travelling,” Axani said, rather nonchalantly, in a statement.


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