[HN Gopher] A $100 DIY muon tomographer
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A $100 DIY muon tomographer
Author : Luc
Score : 198 points
Date : 2025-02-27 15:55 UTC (7 hours ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| tocs3 wrote:
| 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.
|
| https://spectrum.ieee.org/topic/diy/
| bee_rider wrote:
| 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.
| IrishJourno wrote:
| 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:
|
| https://spectrum.ieee.org/type/hands-on/
| bloopernova wrote:
| 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.
| xnx wrote:
| > 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 wrote:
| Could tuning several analog radio receivers between station
| be used in some sort of synthetic aperture telescope?
| Y_Y wrote:
| 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).
|
| https://www.astron.nl/telescopes/lofar/
| dekhn wrote:
| yes, but in an inefficient way, similar to how large
| clusters with ECC are weak cosmic ray detectors.
| semi-extrinsic wrote:
| FYI, an antenna for the 21 cm line can be extremely low effort:
|
| https://spaceaustralia.com/news/diy-radio-telescope-sees-fir...
| IrishJourno wrote:
| You're in luck! David Schneider, the author of this piece, also
| built a $150 hydrogen line antenna for us, based on a TV tuner
| SDR:
|
| https://spectrum.ieee.org/track-the-movement-of-the-milky-wa...
|
| :)
| alnwlsn wrote:
| 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.
| gsf_emergency_2 wrote:
| The cosmic watch detector is cheaper, more reliable (due to
| above shenanigans), and uses only 1 piece of plastic
| scintillator.
|
| It might take more work though. They don't say it but I believe
| you should try to see if other scintillator materials work.
| (Including PET,PSU,PES).
|
| http://cosmicwatch.lns.mit.edu/
| edgarmm wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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)
| ajb wrote:
| 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 wrote:
| 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).
| kxyvr wrote:
| True. That said, I'll also mention that tomography is a very
| rich, interesting field that's still open to new innovations. I
| work in the area and unfortunately needed to pass on a muon
| tomography contract some years ago. By the way, you may know
| this, but the following is for the broader audience.
|
| ---
|
| If anyone is interested, the book Parameter Estimation and
| Inverse Problems by Aster, Borchers, and Thurber give an easy
| introduction to simple tomography problems in their book.
| Example 1.12 in their second edition has a very basic setup.
| More broadly, tomography intersects with an area of study
| called PDE constrained optimization. Commonly, tomography
| problems are setup as a large optimization problem where the
| difference between experimental data and the output of a
| simulation are minimized. Generally, the simulation is
| parameterized on the material properties of whatever is under
| study and are the optimization variables. The idea is that
| whatever material property that produces a simulation that
| matches the experimental data is probably what's there. This
| material property could be something simple like density or
| something more complicated like a full elasticity tensor.
|
| What makes this difficult, is that most good simulations come
| from a system of differential equations, which are infinite
| dimensional and not suitable for running directly in an
| optimization algorithm. As such, care must be taken into
| discretizing the system carefully, so that the optimization
| tool produces something reasonable and physical. Words you'll
| see are things like discretize-then-optimize or optimize-then-
| discretize. Generally speaking, the whole system works very,
| very poorly if one just takes an existing simulator and slaps
| an optimizer on it. Care must be taken to do it right.
|
| As far as the optimizer, the scale is pretty huge. It's common
| to see hundreds of millions of variables if not more. In
| addition, the models normally need to be bounded, so there are
| inequalities that must be respected. For example, if something
| like a density isn't bounded to be positive (which is
| physical), then the simulator itself may diverge (a simulator
| here may be something like a Runge-Kutta method.)
|
| Anyway, it's a big combination of numerical PDEs, optimization,
| HPC, and other tools just to get a chance to run something.
| Something like the detector in the article is very cool because
| it may be a realistic way to get data to test against for super
| cheap.
| speedylight wrote:
| 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 wrote:
| It uses the muons that you are naturally being bombarded with!
| alnwlsn wrote:
| 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.
| simne wrote:
| You may be extremely lucky, but these detectors come from
| everywhere, even could be from exactly some nuclear facility
| like Chernobyl, so contaminated with radioactive dust.
|
| But, for Russian electronics exists good rule - handle in
| gloves and wipe with alcohol before use (sure than properly
| utilize used swabs). So you will clear all dust from surface,
| and if you will not used to suck or crunch radio components you
| are in safety as from my own experience these detectors are
| really durable.
| exabrial wrote:
| > is this thing emitting anything
|
| In the most pedantic sense, yes: electrons, magnetic fields,
| infrared light, etc. It's not designed to, nor is it likely to,
| emit any sort of ionizing radiation
|
| > simply a passive detector
|
| Yes, it is a passive detector
|
| > I'm mainly worried about any potential health risks
|
| You are bombarded with radiation constantly. If you've flown on
| a plane, you are exposed to several times ionizing radiation
| levels that you experience on the ground. If you've stepped
| outside and witnessed a lightning storm you have exposed
| yourself to high energy gamma rays and neutrons. If you've ever
| eaten a banana, spent the night in a strangers bed, strayed
| near clay river beds, entered a basement of a house, or stepped
| outside in sunlight you have exposed yourself to substantial
| increase of ionizing radiation compared to baseline.
|
| Humans brains have an extraordinarily hard team comprehending
| logarithmic scales. "Safe" radiation exposure isn't "None", as
| that's pretty much impossible. Your body has also long ago
| evolved to deal with these problems and can easily handle 100x
| times what occurs naturally at the ground without even a single
| health effect.
|
| If you want zero exposure, the only real option is to move to
| an undersea bubble thousands of feet below the sea, but even
| seawater contains radioactive ions from the metal salts
| dissolved in it.
| pnemonic wrote:
| Could this be of consequence to, say, a treasure hunting
| operation? Perhaps in the North Atlantic?
| oaththrowaway wrote:
| A treasure hunt? On Oak Island? Could it be...?
| jasongill wrote:
| Is it a Spanish galleon? Or, perhaps, the Knights Templar?
| PaulHoule wrote:
| 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
| magicalhippo wrote:
| I've wanted to make such a thing, but that got me thinking about
| a 6 tube design, three tubes on each layer in a # pattern, to get
| some angular resolution.
|
| It also got me down the path of making a scintillation detector.
| However I've yet to find a hardware store source of scintillating
| material.
|
| I kinda wanted something that didn't rely on a one-off source
| like asking my local uni for some scraps.
| natnatenathan wrote:
| Tomography or tombography :)
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