How to Detect Muons!

Ever heard of a muon? I hadn't either until I stumbled upon this awesome project! Now I can detect and count these cosmic particles from my desktop - and you can too.

Tonic and Energy by Elexive is licensed under a Creative Commons Attribution License

This video is sponsored by XOD.

[joshajohnson]

Who would have thought a video not about concrete could be so interesting!

[michaelwoodhams]

I did my MSc thesis on a cosmic ray detection experiment (the JANZOS array) trying to detect cosmic rays created by supernova SN1987A, which was in the Large Magellanic Cloud, and is the nearest known supernova in several hundred years. We used two different detection techniques: scintillator detectors (like yours) and air Cerenkov detectors. (Your shot of fancy science cosmic ray detection was air Cerenkov, but much more sophisticated that what we had.) Our scintillator array had 76 detectors, each 1m^2 or 0.5m^2, spread over about 150m diameter area.

Although you describe your device as a muon detector, it will detect any charged particle which is able to penetrate the atmosphere from source to your detector, and penetrate the detector itself.

When a very high energy cosmic ray hits the top of the atmosphere, it will interact with an atom to produce several slightly lower energy particles, which in turn interact to produce still more particles, until you have very many particles travelling just short of the speed of light and spread out like a pancake. This is a particle shower. Eventually the particles become low enough energy that interactions with the atmosphere absorb the particles rather than generating new ones, and the shower dies. So it starts small, gets big, the dies away to almost nothing. The big exception is the muons, as they are much more penetrating than the electrons, positrons and gamma rays which make up most of the shower. If you are at low altitude, very few cosmic ray showers will penetrate the atmosphere that far, but the muons that they produce will (and hundreds of metres of rock beyond that.)

Our scintillator detector array used detection timings from the detectors to reconstruct the direction of travel of the particle shower, and hence of the initial cosmic ray.

Muons are so penetrating that a few floors of parking building concrete should have minimal effect on them. (It is a long time since I worked on this, so I might be wrong here.) I expect that the reduction you saw was rather due to shielding from non-muons in the rare cosmic ray showers which penetrated to your level. Also note that when you get a coincidence detection with your two detectors, it might not be a single particle which travelled through both detectors, but a cosmic ray shower where different particles in the same shower triggered the two detectors. You can also get coincident counts from local radioactivity, so long as the particle can penetrate both detectors.

Here are some more experiments for you:
If the coincidence counts are from single particles, as you move your detectors further apart, the detection rate will fall, and the decrease in rate is easily calculable from the geometry of the relative placement of the two scintillators. Conversely, the coincident hit rate due to cosmic ray showers will be independent of the relative location of the two detectors (unless the separation is large compared to the size of the shower, which would be at least tens of metres.) (Your side-by-side-detectors measurement might already be a measurement of cosmic ray showers.) So it should be pretty easy to separate these two effects. (You'll need to think about the length of the time window for coincidence counts. To detect showers, your window needs to be at least as large as the light travel time between your two detectors. If your coincidence time window is something like 1ms, this won't be a problem, but if it is 1ns it could be.) Once you've done this to estimate separate rates for showers and for muons, you can start to experiment with how this changes depending on location:
* At higher altitude, you should see a higher shower rate, but much the same muon rate. Expect a very large difference in shower rate between sea level and a few thousand metres altitude. (Our experiment was, as I recall, at about 1600m altitude.)
* Shielded locations (parking building) should decrease shower rate but have little effect on muon rate
* Local radioactivity rate (which would behave like muons, as it its single particle coincidence) should be very dependent on location, such as whether your detectors are sitting on rock or on a thick layer of dirt. (I'm really not sure if this rate will be significant at all.)
* If you have your two detectors stacked vertically, counts from local radioactivity are likely to be particles coming from below. Try putting a few cm of lead under your detectors and see if it makes a difference.

Did we detect cosmic rays from SN1987A? The Cerenkov detectors gave us a marginal signal (I think it was 3.3 sigma, after correction for multiple testing) for a two day period when other experiments also thought they saw something, but we got nothing significant from the scintillator array.
If I remember correctly, our scintillator array detected about one shower a second, but it had much greater collecting area than your little detector, and it was probably at greater altitude, which has a big effect on shower frequency.

We'd have loved to have had dedicated muon detectors (basically more scinillator detectors but buried under a few metres of rock) as part of our array. Showers initiated by hadrons (protons and antiprotons) produce lots of muons, the approx 1% of showers initiated by gamma rays or electrons/positrons do not. Because magnetic fields bend the paths of hadrons, the direction of the shower doesn't indicate the direction to the cosmic ray source. If we could have distinguished between hadron initiated showers and gamma/lepton ray initiated showers, it would have improved our signal (gamma ray initiated showers) to noise (anything-else initiated showers) enormously.

[PracticalEngineeringChannel]

This project was designed with funding from the MIT Physics Department to encourage students to pursue careers in science and engineering. I want to help further the educational aspect of what Spencer and his team are doing by giving these detectors (and my leftover spare parts) away. If you are an educator and interested in having a desktop muon detector for your classroom or if you'd like to build one as a class project, shoot me an email at the address in my channel’s “about” page and we’ll give these devices a happy home.

Edit: The detectors and spare parts have been spoken for!

[oootoob]

Muon detection was used to discover a new hidden chamber in the great pyramid at Giza in 2017 and it is touted as a new approach to 'seeing' inside large dense objects like volcanoes, a technique called muography

[aarondcmedia]

Certainly easier than buying a mine and filling it with heavy water and light detectors!

The enclosures and overall look of the product is very professional. Good stuff.

[feynstein]

A video about a civil engineer using electronic equipment to do particle physics, sponsored by Zod from Superman. I think we just broke reality.

[vernonbrechin]

Thanks for your venture into subatomic particle detection, processing and readouts. That circuit board was beautifully designed with descriptive labeling.

I spent much of my career at the SLAC research facility, as an electronic technician working with particle detectors and beam position monitors.

[verdatum]

When I was like 5 years old, my father explained to me how cosmic rays are constantly shooting through my body all day long. And there was nothing I could do to stop it. Engineers make for trepadatious parents.

[_Matyro_]

With increasing size of the szintillator you can quite reduce the necessary measure time. Currently we implement a similar device with a big very thin woven szintillator. This will be put on a drone / weather balloon to measure rate and direction depending on the height. In this case the experiment focused on undergraduate physic students to build this. Additional we will use one of the STM32 boards for its much higher performance and efficiency.

[b.hagedash]

It would be interesting if you set this up at the bottom of an alcohol cloud chamber, being able to see the transit of the particle and then gauge whether it's always picked up by the detector.

[HebaruSan]

Fun fact, those muons don't last long enough on their own to make it through the atmosphere, but they're moving so close to the speed of light that their lifetimes get a boost thanks to time dilation a la special relativity.

[chesthairascot]

Awesome video- I'm a bit tempted to build an array of those myself.

If I can offer some constructive criticism on soldering- It helps to apply heat to the part and board pad at the same time, then introduce the solder after they're both warm. When done this way, the solder will quickly wick to both. It also shortens the amount of time you have to work with the solder, so you can get the joint done correctly before the flux burns off (which makes the solder unworkable.)

You'll also want to make sure that you're touching the solder to the pad and part, and not the iron. Touching it to the iron will burn off the flux before it can do its job.

[nwmancuso]

You can find void space in volcanoes and pyramids using muons and your last experiment touched on that. If you had more detectors you could even graph empty spaces with enough data points. Thanks for the video!

[mlxp]

This is one of the most wholesome science/engineering channels on YouTube, right up there with SmarterEveryDay

[amyshaw]

omg, even at the start of this video, i can tell this is going to be cool. we have just been covering subatomic particles and their relatives in physics, all the hadrons, leptons, bosons and mesons. its so cool, and i need this in my life now

[guilemaigre]

I'm a 3rd year physic student, and this year we exactly that experiment for our Lab lesson. Expect we used 80's or maybe even 70's gear and old NIM logic module. It was pretty fun.
And with all the data you mesured, you should be able to make a exponential fit to mesure directly the life time of the Muon.

[thekinginyellow]

Built one of these in my senior year of college. Had a much larger scintillator, and much more primitive electronics. Mind you this was nigh on to thirty years ago. Worked pretty well. Came up with Muon lifetimes that matched within 0.1% of the expected result

[zapityzapzap]

Something you may enjoy, software defined radios. Can gather radio system capacity (loading) data with them, spectral analysts, see how reinforced concrete affects signal, track ADS-B…all sorts of fun stuff.

[catavar]

I usually come here for the concrete, but this reminds me of my time as a grad student working on a cosmic ray air shower array (I moved on to work on stellar astrophysics since). This is a really cool gadget and now that I know about it, I might get one for my office.

[blevenzon]

I’m so thrilled to have stumbled on your channel. I just binge watched all the videos. Amazing and fascinating stuff thank you so so much