A $100 DIY muon tomographer
22 comments
·February 27, 2025alnwlsn
It's things like this that remind me there's always a little more to discover. I've built a number of those SBM20 geiger counters but I've never come across this muon detector design before. Seems to be a pretty well known design:
* https://www.hackster.io/jdpetrey/muon-detector-23bb72 * https://www.madexp.it/2024/11/19/muon-and-geiger-counter/ * https://iopscience.iop.org/article/10.1088/0031-9120/50/3/31...
Pro tip - not all the SBM-20 tubes on Ebay are created equal! Some sellers will happily sell you tubes that are shorted, open, or just don't work. The better ones test their tubes.
edgarmm
My good friend convinced another friend to do this for a "small" uni project. They showed it worked to a very impressed professor, only to shortly after discover (and not reveal to the professor) that it was disconnected and they were just seeing noise.
He passed away a few months after, but this sparked a smile in me.
ptero
This is common in early stage research. And, should the students reveal the error to the professor, the reaction should have been along the lines "thank you for the update! It was a great idea. Ideas can at first appear to work due to luck or a methodology error, then fail. This is normal. Great job self-discovering the failure. Keep trying ideas, this is how the research is done!"
But it is important to eventually do more rigorous checks before going for a public announcement. See Robert Wood's debunking of N-rays for what happens when one does not.
spwa4
Well, I have 2 experiences of discovering this to be the case in others' setups (one that they reported noise instead of results, or maybe even went further. They reported a massive success, and yes, better "results" than I did. They were always reporting zero + some noise as opposed to measurement + noise. Given that it was always reporting zero I might be convinced this was a mistake rather than cheating, but ... they certainly didn't correct anything. Their method just didn't work, so they measured small values, which made the noise on their sensor actually close to the correct value (they "corrected" negative values by ignoring the minus sign). Another was a case of dissolved metals suddenly appearing out of nowhere in test tubes, changing the results (where only 3 people, not including me, but including the professor) has access to them) and in one case I was ignored, in the other case punished (essentially fired).
dekhn
I would say much of my career in science consisted of getting results, showing them to smarter people, and being told I was just looking at noise.
(most of the time, that was true)
bloopernova
When I have the time, I'd like to build an antenna to try to pick up the hydrogen line from space.
Just that simple thing is so strange to me, that with a handful of components you can listen to the cosmos. I really wish science classes would have included that sort of thing.
semi-extrinsic
FYI, an antenna for the 21 cm line can be extremely low effort:
https://spaceaustralia.com/news/diy-radio-telescope-sees-fir...
xnx
> that with a handful of components you can listen to the cosmos
Tuning an analog radio or TV between stations also accomplishes this in a more abstract way.
tocs3
Could tuning several analog radio receivers between station be used in some sort of synthetic aperture telescope?
Y_Y
Sounds a bit like Lofar. Stick a few hundred antennas into a field, collect all the raw data, and then do some herculean signal processing and you end up with a fantastic radio telescope that you can "point" retrospectively, e.g. to look at something that just happened in the gamma, before it happened (on a scale of seconds).
dekhn
yes, but in an inefficient way, similar to how large clusters with ECC are weak cosmic ray detectors.
tocs3
My new favorite sciencey DIY site. It reminds me of the early Popular Mechanics and Scientific American projects. Now all I need is lots more time (or less responsibility). These are the sorts of things that should be available in middle and high schools everywhere.
edit: Adding a link to a page with a list of projects on the site.
IrishJourno
I'm the editor of Spectrum's "Hands On" DIY column: thank you so much! The general goal is to have projects that can be done in a weekend or three for less than roughly $300 and which point to something interesting beyond just the build itself. A lot of credit has to go to David Schneider who is the author of this piece, and has contributed many of Spectrum's citizen science projects.
BTW, If you want to see just the DIY projects instead of all our DIY-related coverage (which can include e.g. interviews or news articles) another handy link is:
bee_rider
Worth noting that IEEE is the professional society for electrical engineers. Spectrum seems to be their kind of pop-sci outreach magazine. But, being under IEEE’s umbrella makes it quite special, pop-sci magazines are always pulled toward the bombastic and over-dramatic. Spectrum, because of their origins in a research/professional EE society seems to remain more… grounded.
ajb
This is pretty cool.
The title here is incorrect; this is not tomography (and the OP doesn't claim it is). The article mentions tomography but what's happening here is individual measurements.
Tomography is also pretty cool, although the math is pretty painful (Terry Tao has papers on it)
tocs3
I saw a wonderful demonstration of a supper simple interactive tomographic reconstruction (in a web page explaining what a CAT scan is). I cannot find it anywhere now. It produced pretty good results with the simple algorithm and was easily understood. It just drew stripes across the reconstruction image of the value of the average measurement of each row of the sample image and then rotated both images and did it again (maybe someone can explain it better).
speedylight
This may be a stupid question, but is this thing emitting anything or is it simply a passive detector? I’m mainly worried about any potential health risks.
misnome
It uses the muons that you are naturally being bombarded with!
alnwlsn
The most dangerous thing about this is that the geiger tubes run at about 400V, backed by a small capacitor. If you touch it, it will feel about like getting hit by a bug zapper.
Apart from that, yes, they are passive detectors.
pnemonic
Could this be of consequence to, say, a treasure hunting operation? Perhaps in the North Atlantic?
oaththrowaway
A treasure hunt? On Oak Island? Could it be...?
This might be the easiest "particle physics without a particle accelerator" experiments you can do. This is your accelerator:
https://en.wikipedia.org/wiki/Air_shower_(physics)
And the muons produce two pulses in your detector, one when they are scattered to a stop and another when they decay. By measuring the time between the pulses you can fit the probability distribution and determine the half life of the mupn which is about 2.2 microseconds [1] And of course you can take measurements over time, at different altitudes and in different positions. If it wasn't for relativistic time dilation, muons would mostly decay high up in the atmosphere and not reach the ground.
This was one of the most popular experiments in the Physics 510 lab, which was the only class you had to take to get a Physics PhD at Cornell because it was so easy. It's also popular for high school physics for the same reason.
[1] https://en.wikipedia.org/wiki/Muon