scintillator

10 Articles

2025 One Hertz Challenge: Timekeeping At One Becquerel

August 18, 2025 by 23 Comments

The Becquerel (Bq) is an SI unit of radioactivity: one becquerel is equivalent to one radioactive decay per second. That absolutely does not make it equivalent to one hertz — the random nature of radioactive decay means you’ll never get one pulse every second — but it does make it interesting. [mihai.cuciuc] certainly thought so, when he endeavored to create a clock that would tick at one becquerel.

The result is an interesting version of a Vetinari Clock, first conceived of by [Terry Pratchett] in his Discworld books. In the books, the irregular tick of the clock is used by Lord Vetinari as a form of psychological torture. For some reason, imposing this torture on ourselves has long been popular amongst hackers.

Without an impractical amount of shielding, any one-becquerel source would be swamped by background radiation, so [mihai] had to get creative. Luckily, he is the creator of the Pomelo gamma-ray spectroscope, which allowed him to be discriminating. He’s using an Am-241 source, but just looking for the characteristic 59.5 KeV gamma rays was not going to cut it at such a low count rate. Instead he’s using two of the Pomelo solid-state scintillation as a coincidence detector, with one tuned for the Am-241’s alpha emissions. When both detectors go off simultaneously, that counts as an event and triggers the clock to tick.

How he got exactly one becquerel of activity is a clever hack, too. The Am-241 source he has is far more active than one decay per second, but by varying the distance from the gamma detector he was able to cut down to one detection per second using the inverse square law and the shielding provided by Earth’s atmosphere. The result is a time signal that is a stable one hertz… if averaged over a long enough period. For now, anyway. As the Am-241 decays away, its activity decreases, and [mihai] admits the clock loses about 0.4 seconds per day.

While we won’t be giving the prize for accuracy in this contest, we are sure Lord Vetinari would be proud. The Geiger-counter sound effect you can hear in the demo video embedded below is great touch. It absolutely increases the psychic damage this cursed object inflicts.

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To See Within: Detecting X-Rays

April 23, 2025 by 19 Comments

It’s amazing how quickly medical science made radiography one of its main diagnostic tools. Medicine had barely emerged from its Dark Age of bloodletting and the four humours when X-rays were discovered, and the realization that the internal structure of our bodies could cast shadows of this mysterious “X-Light” opened up diagnostic possibilities that went far beyond the educated guesswork and exploratory surgery doctors had relied on for centuries.

The problem is, X-rays are one of those things that you can’t see, feel, or smell, at least mostly; X-rays cause visible artifacts in some people’s eyes, and the pencil-thin beam of a CT scanner can create a distinct smell of ozone when it passes through the nasal cavity — ask me how I know. But to be diagnostically useful, the varying intensities created by X-rays passing through living tissue need to be translated into an image. We’ve already looked at how X-rays are produced, so now it’s time to take a look at how X-rays are detected and turned into medical miracles.

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Catching The BOAT: Gamma-Ray Bursts And The Brightest Of All Time

September 18, 2024 by 12 Comments

Down here at the bottom of our ocean of air, it’s easy to get complacent about the hazards our universe presents. We feel safe from the dangers of the vacuum of space, where radiation sizzles and rocks whizz around. In the same way that a catfish doesn’t much care what’s going on above the surface of his pond, so too are we content that our atmosphere will deflect, absorb, or incinerate just about anything that space throws our way.

Or will it? We all know that there are things out there in the solar system that are more than capable of wiping us out, and every day holds a non-zero chance that we’ll take the same ride the dinosaurs took 65 million years ago. But if that’s not enough to get you going, now we have to worry about gamma-ray bursts, searing blasts of energy crossing half the universe to arrive here and dump unimaginable amounts of energy on us, enough to not only be measurable by sensitive instruments in space but also to effect systems here on the ground, and in some cases, to physically alter our atmosphere.

Gamma-ray bursts are equal parts fascinating physics and terrifying science fiction. Here’s a look at the science behind them and the engineering that goes into detecting and studying them.

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Visualizing Ionizing Radiation With DIY Plastic Scintillators

January 12, 2021 by 16 Comments

Although most types of radiation are invisible, except for the visible part of the EM spectrum, there are many ways that we can make various types of radiation visible. One of these methods is called ‘scintillation’, which can be used to make ionizing radiation visible. Recently [Lukas Springer] demonstrated how to make scintillators out of what is essentially plastic: bisphenol-A (E45, ‘epoxy’) resin with hardener and other additives.

The essential principle of operation behind a scintillator is its sensitivity to ionizing radiation, along with the tendency to absorb the energy and re-emit it in the form of light, i.e. luminescence. This is akin to the luminescence of LEDs, except that in their case the underlying principle is that of electro-luminescence. In the case of a plastic scintillator, the scintillating material is suspended in the solid polymer matrix base.

As [Lukas] points out, plastic scintillators are hardly ideal when it comes to their sensitivity to ionizing radiation, but they compensate for this by being easy to shape and produce, while being very durable. For this experiment, he used regular epoxy as the scintillator matrix, p-Terphenyl as primary scintillator and Coumarin 102 as the wavelength shifter. These three compounds act as a reaction chain, with the matrix absorbing the radiation and transferring it to the primary scintillator, which in turns emits the energy as light.

As the primary scintillator tends to radiate in the deep UV part of the EM spectrum, a wavelength shifter (i.e. secondary scintillator) which ‘shifts’ the emitted UV radiation into the visible part of the spectrum.

After producing a batch of plastic scintillators following the above recipe, [Lukas] irradiated them with gamma radiation, and found them to perform worse than some already not remarkable Russian PS-based scintillators. [Lukas’s] guess is that the matrix may be absorbing the primary scintillator’s output, or a mismatch between the primary and second scintillator.

While tricky to get right, it does seem like a fun hobby if one has some interesting in chemistry. [Lukas] (@GigaBecquerel on Twitter) provides a basic recipe as well as many other compounds to use for the primary and secondary scintillator, as well as the matrix compound. Enough to get started with.

Towards A 3D-Printed Neutrino Detector

June 30, 2020 by 7 Comments

Additive manufacturing techniques like fused deposition modeling, aka 3D printing, are often used for rapid prototyping. Another advantage is that it can create shapes that are too complex to be made with traditional manufacturing like CNC milling. Now, 3D printing has even found its way into particle physics as an international collaboration led by a group from CERN is developing a new plastic scintillator production technique that involves additive manufacturing.

A scintillator is a fluorescent material that can be used for particle detection through the flashes of light created by ionizing radiation. Plastic scintillators can be made by adding luminophores to a transparent polymer such as polystyrene and are usually produced by conventional techniques like injection molding.

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Hackaday Podcast 035: LED Cubes Taking Over, Ada Vanquishes C Bugs, Rad Monitoring Is Hot, And 3D Printing Goes Full 3D

September 13, 2019 by No comments

Hackaday Editors Mike Szczys and Elliot Williams get caught up on the most interesting hacks of the past week. On this episode we take a deep dive into radiation-monitor projects, both Geiger tube and scintillator based, as well as LED cube projects that pack pixels onto six PCBs with parts counts reaching into the tens of thousands. In the 3D printing world we want non-planar printing to be the next big thing. Padauk microcontrollers are small, cheap, and do things in really interesting ways if you don’t mind embracing the ecosystem. And what’s the best way to read a water meter with a microcontroller?

Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

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DIY Scintillation Detector Is Mighty Sensitive

July 19, 2019 by 24 Comments

Geiger counters are a popular hacker project, and may yet prove useful if and when the nuclear apocalypse comes to pass. They’re not the only technology out there for detecting radiation however. Scintillation detectors are an alternative method of getting the job done, and [Alex Lungu] has built one of his own.

Scintillation detectors have several benefits over the more common Geiger-Muller counter. They work by employing crystals which emit light, or scintillate, in the presence of ionizing radiation. This light is then passed to a photomultiplier tube, which emits a cascade of electrons in response. This signal represents the level of radioactivity detected. They can be much more sensitive to small amounts of radiation, and are more sensitive to gamma radiation than Geiger-Muller tubes. However, they’re typically considered harder to use and more expensive to build.

[Alex]’s build uses a 2-inch sodium iodide scintillator, in combination with a cheap photomultiplier tube he scored at a flea market for a song. [Jim Williams]’s High Voltage, Low Noise power supply is used to run the tube, and it’s all wrapped up in a tidy 3D printed enclosure. Output is via BNC connectors on the rear of the device.

Testing shows that the design works, and is significantly more sensitive than [Alex]’s Geiger-Muller counter, as expected. If you’re interested in measuring small amounts of radiation accurately, this could be the build for you. We’ve seen this technology used to do gamma ray spectroscopy too.

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