Make A Cheap Muon Detector Using Cosmicwatch

A little over a year ago we’d written about a sub $100 muon detector that MIT doctoral candidate [Spencer Axani] and a few others had put together. At the time there was little more than a paper on arxiv.org about it. Now, a few versions later they’ve refined it to the level of a kit with full instructions for making your own under the banner, CosmicWatch including PCB Gerber files for the two surface mount boards you’ll need to assemble.

What’s a muon? The Earth is under constant bombardment from cosmic rays, most of them being nuclei expelled from supernova explosions. As they collide with nuclei in our atmosphere, pions and kaons are produced, and the pions then decay into muons.  These muons are similar to electrons, having a +1 or -1 charge, but with 200 times the mass.

This pion-to-muon decay happens higher than 10 km above the Earth’s surface. But the muons have a lifetime at rest of 2.2 μs. This means that the number of muons peak at around 10 km and decrease as you go down. A jetliner at 30,000 feet will encounter far more muons than will someone at the Earth’s surface where there’s one per cm2 per minute, and the deeper underground you go the fewer still. This makes them useful for inferring altitude and depth.

How does CosmicWatch detect these muons? The working components of the detector consist of a plastic scintillator, a silicon photomultiplier (SiPM), a main circuit board which does signal amplification and peak detection among other things, and an Arduino nano.

As a muon passes through the scintillating material, some of its energy is absorbed and re-emitted as photons. Those photons are detected by the silicon photomultiplier (SiPM) which then outputs an electrical signal that is approximately 0.5 μs wide and 10-100 mV. That’s then amplified by a factor of 6. However, the amplified pulse is too brief for the Arduino nano and so it’s stretched out by the peak detector to roughly 100 μs. The Arduino samples the peak detector’s output and calculates the original pulse’s amplitude.

Their webpage has copious details on where to get the parts, the software and how to make it. However, they do assume you can either find a cheap photomultiplier somewhere or buy it in quantities of over 100 brand new, presumably as part of a school program. That bulk purchase makes the difference between a $50 part and one just over $100. But being skilled hackers we’re sure you can find other ways to save costs, and $150 for a muon detector still isn’t too unreasonable.

Detecting muons seems to have become a thing lately. Not too long ago we reported on a Hackaday prize entry for a detector that uses Russian Geiger–Müller Tubes.

Hackaday Prize Entry : Cosmic Particle Detector Is Citizen Science Disguised As Art

Thanks to CERN and their work in detecting the Higgs Boson using the Large Hadron Collider (LHC), there has been a surge of interest among many to learn more about the basic building blocks of the Universe. CERN could do it due to the immense power of the LHC — capable of reaching a beam energy of almost 14TeV. Compared to this, some cosmic rays have energies as high as 3 × 1020 eV. And these cosmic rays keep raining down on Earth continuously, creating a chain reaction of particles when they interact with atmospheric molecules. By the time many of these particles reach the surface of the earth, they have mutated into “muons”, which can be detected using Geiger–Müller Tubes (GMT).

[Robert Hart] is building an array of individual cosmic ray detectors that can be distributed across a landscape to display how these cosmic rays (particles, technically) arrive as showers of muons. It’s a citizen science project disguised as an art installation.

The heart of each individual device will be a set of three Russian Geiger–Müller Tubes to detect the particles, and an RGB LED that lights up depending on the type of particle detected. There will also be an audio amplifier driving a small 1W speaker to provide some sound effects. A solar panel is used to charge the battery, which will feed the converters that generate the logic and high voltages required for the GMT array. The GMT signals pass through a pulse shaper and then through the logic gates, finally being amplified to drive the LEDs and the audio amplifier. Depending on the direction and order in which the particles pass through the GMT’s, the device will produce a bright flash of one of 4 colors — red, green, blue or white. It also triggers generation one of three musical notes — C, F, G or a combination of all three. The logic section uses coincidence detection, which has worked well for his earlier iterations. A coincidence detector is an AND logic which produces an output when two input events occur sufficiently close to each other in time. He’s experimented with several design versions, before settling on a trio of 555 monostable multivibrators to provide the initial pulse shaping, followed by some AND gates. A neat PCB design brings it all together.

While the prototypes are housed in wooden cases, he’s going to experiment with various enclosure and mounting options to see which works best — bollard lamp posts, spheres, something that hangs on a tree or tripod or is put in the ground like a paving block. Future prototypes and installations may include a software, pulse summing and solid-state detectors. Embedded below is a video of his current version of the detector, but there are several other interesting videos on his project page that are worth looking at. And if this has gotten you interested, check out this CERN brochure — LHC, The guide for a simple explanation of particle physics and information on the LHC.

Continue reading “Hackaday Prize Entry : Cosmic Particle Detector Is Citizen Science Disguised As Art”

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]

Detect Cosmic Rays with Your Smartphone Using CRAYFIS

[Daniel Whiteson and Michael Mulhearn], researchers at the University of California, have come up with a novel method of detecting ultra-high energy cosmic rays (UHECR) using smartphones. UHECR are defined as having energy greater than 1018eV. They are rare and very difficult to detect with current arrays. In order to examine enough air showers to detect UHECR, more surface area is needed. Current arrays, like the Pierre Auger Observatory and AGASA, cannot get much larger without dramatically increasing cost. A similar THP Quarterfinalist project is the construction of a low-cost cosmic ray observatory, where it was mentioned that more detection area is needed in order to obtain enough data to be useful.

[Daniel Whiteson and Michael Mulhearn] and colleagues noted that smartphone cameras with CMOS sensors can detect ionizing radiation, which means they also will pick up muons and high-energy photons from cosmic rays. The ubiquitous presence of smartphones makes their collective detection of air showers and UHECR an intriguing possibility. To make all this happen, [Whiteson and Mulhearn] created a smartphone app called CRAYFIS, short for Cosmic RAYs Found In Smartphones. The app turns an idle smartphone into a cosmic ray detector. When the screen goes to sleep and the camera is face-down, CRAYFIS starts taking data from the camera. If a cosmic ray hits the CMOS sensor, the image data is stored on the smartphone along with the arrival time and the phone’s geolocation. This information is uploaded to a central server via the phone’s WiFi. The user does not have to interact with the app beyond installing it. It’s worth noting that CRAYFIS will only capture when the phone is plugged in, so no worries about dead batteries.

The goal of CRAYFIS is to have a minimum of one million smartphones running the app, with a density of 1000 smartphones per square kilometer. As an incentive, anyone whose smartphone data is used in a future scientific paper will be listed as an author. There are CRAYFIS app versions for Android and iOS platforms according to the site. CRAYFIS is still in beta, so the apps aren’t publicly available. Head over to the site to join up!

[via Science]

Arduino muon detector

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[Sebastian Tomczak] was borrowing a homeade muon detector from his friend, and managed to hook it up to his computer through an Arduino. The detector itself uses 3 fluorescent tubes to detect radiation. Three separate tubes are used in order to filter out terrestrial radiation; cosmic radiation will fall in-line with the tubes and pass through at least two of them, whereas terrestrial radiation will only hit one. There is some basic circuitry to amplify the signal and then perform the OR operation.

[Tomczak]  used an Arduino to take the raw data and feed it into his computer. He then used Max/MSP to analyze the data and filter out background noise, leaving only the cosmic ray data. He didn’t mention what he was going to use the data for, though. Maybe he’ll hook it up to a synthesizer.

Related: Digital Geiger counter

[via @littlebirdceo]