An Experiment To Test Radioactive Decay Varying Over Time

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Here’s a hypothesis for you: radioactive decay varies over time, possibly with a yearly cycle. [Panteltje] decided to test this hypothesis, and so far has two year’s worth of data to comb over.

Radioactive decay can be easily detected with a photomultiplier tube, but these tubes are sensitive to magnetic fields and cosmic rays that would easily fly through just about any shielding [Pantelje] could come up with. Instead, the radiation in this setup is detected with simple photo detectors, pressed right up against a tritium-filled glass ampoule, a somewhat common lighting solution for fishing lures, watch faces, and compasses.

The experimental setup records the photo detectors, a temperature sensor, and a voltage reference, recording all the data to an EEPROM once an hour. All the important electronics are stuffed into a heatsinked, insulated, light-proof box, while the control electronics reside on a larger board with battery backup, alarm, indicator LEDs, and an RS232 connection.

After one year, [Pantelje] recorded the data and reset the experiment for another year. There are now two years worth of data available, ready for anyone to analyze. Of course, evidence that radioactive decay changes over the course of a few years would turn just about every scientific discipline on its head, so at the very least [Panteltje] has a great record of the output of tritium lights against the expected half-life.

Improving A Homebrew CT Scanner With Barium

CTscanner

[Peter] has been working on his homebrew CT scanner for a while, and it’s finally become something more than a spinning torus of plywood. He’s managed to image the inside of a few pieces of produce using an off-the-shelf radiation detector and a radioactive barium source

When we last saw [Peter]‘s CT scanner, he had finished the mechanical and electronic part of the Stargate-like device, but the radioactive source was still out of reach. He had initially planned on using either cadmium 109 or barium 133. Both of these presented a few problems for the CT scanner.

The sensor [Peter] is a silicon photodiode high energy particle detector from Radiation Watch this detector was calibrated for cesium with a detection threshold of around 80keV. This just wasn’t sensitive enough to detect 22keV emissions from Cd109, but a small add-on board to the sensor can recalibrate the threshold of the sensor down to the noise floor.

Still, cadmium 109 just wasn’t giving [Peter] the results he wanted, resulting in a switch to barium 133. This was a much hotter source (but still negligible in the grand scheme of radioactivity) that allowed for a much better signal to noise ratio and shorter scans.

With a good source, [Peter] started to acquire some data on the internals of some fruit around his house. It’s still a slow process with very low resolution – the avocado in the pic above has 5mm resolution with an acquisition time of over an hour – but the whole thing works, imaging the internal structure of a bell pepper surprisingly well.

Towards a Low Cost, Desktop CT Scanner

CT

For [Peter Jansen], the most interesting course in grad school was Advanced Brain Imaging; each class was a lecture followed by a trip to the imaging lab where grad students would take turns being holed up in a MRI machine. A few years into his doctorate, [Peter] found himself in a very opportune situation – his local hackerspace just acquired a shiny new laser cutter, he had some free time on his hands, and the dream of creating a medical imaging device was still in the back of his mind. A few weeks later, the beginnings of an open source CT scanner began to take shape.

This isn’t an MRI machine that [Peter] so fondly remembered from grad school. A good thing, that, as superconducting magnets chilled with liquid helium is a little excessive for a desktop unit. Instead, [Peter] is building a CT scanner, a device that takes multiple x-ray ‘slices’ around an axis of rotation. These slices can then be recompiled into a 3D visualization of the inside of any object.

The mechanics of the build are a Stargate-like torus with stepper motor moving back and forth inside the disk. This, combined with the rotation of the disk and moving the bed back and forth allow the imager to position itself anywhere along an object.

For the radioactive detector, [Peter] is using a CCD marketed as a high-energy particle detector by Radiation Watch. Not only does this allow for an easy interface with a microcontroller, it’s also much smaller than big, heavy photomultiplier tubes found in old CT scanners. As for the source, [Peter] is going for very low intensity sources, most likely Barium or Cadmium that will take many minutes to capture a single slice.

The machine operates just above normal background radiation, so while being extremely safe for a desktop CT scanner, it is, however, very slow. This doesn’t bother [Peter], as ‘free’ time on a CT scanner allows for some very interesting, not seen before visualizations, such as a plant growing from a seed, spreading its roots, and breaking the surface as a seedling.

[Peter] still has some work to do on his desktop CT scanner, but once the stepper motor and sensor board are complete, he should be well on his way towards scanning carrots, apples, and just about everything else around his house.

A think-tank solution for monitoring radioactive water storge tanks

SONY DSC

When we hear reports of radioactive water leaking into the ocean from the [Fukushima Dai-Ichi] plant in Japan we literally have to keep ourselves from grinding our teeth. Surly the world contains enough brain power to overcome these hazards. Instead of letting it gnaw at him, [Akiba] is directing his skills at one solution that could help with the issue. There are a number of storage tanks on site which hold radioactive water and are prone to leaking. After hearing that they are checked manually each day, with no automated level monitoring, he got to work. Above is the wireless non-contact tank level sensor rig he built to test out his idea.

A couple of things made this a quick project for him. First off, he just happened to have a MaxSonar MB7389 waterproof sonar sensor on hand. Think of this as a really fancy PING sensor that is water tight and can measure distance up to five meters. [Akiba's] assumption is that the tanks have a hatch at the top into which this sensor would be positioned. The box next to it contains a Freakduino of his own design which includes hardware for wireless communications at 900 MHz. This is the same hardware he used for that wireless toilet monitor.

We really like seeing hacker solutions to environmental problems. A prime example is some of the cleanup hacks we saw around the time of the BP Gulf of Mexico oil spill.

 

Geiger counter tells you if your dishes are radioactive

geiger-counter-build

[Henrik] really turned out a nice little Geiger counter board based on a cold war era Geiger tube.

It works in much the same way as other projects along the same lines. It does run on batteries if needed, which is no small feat since the tube wants high voltage to operate correctly. And the video after the break shows it spitting out readings to a terminal window when connected to a computer via USB.

But what really caught our eye is the radioactive source material he used for testing. Since he didn’t have anything on hand he had to order something, and ended up going with a couple shards from a dinner plate. A radioactive dinner plate to exact and it’s a brand name you’ve probably heard of before. Red Fiesta Ware apparently used to be radioactive. It’s even mentioned in the intro to the Wikipedia article. Go figure!

One other thing we noticed was [Henrik's] method of interfacing his multimeter with a breadboard. One of the project photos shows the probe with thin wire wrapped around the tip. We assume this is to make it easy to plug into the breadboard.

Despite this little digression away from the main project we did really enjoy learning about his build. And you can see him showing it off in the clip after the break.

[Read more...]

Cheap spark detector for alpha particles

[JAC_101] wrote in to let us know that the Truely Mad Scientist’s LVL1 Splinter Group just built a simple Alpha Particle detector.  The detector is a high voltage DC spark gap that is triggered by ionizing radiation. Making one of these detectors involves gutting a cold cathode power supply for some high voltage AC, then bumping that source up to crazy high voltage DC with a Cockcroft-Walton generator.  Once the spark gap distance is carefully adjusted it will light up brilliantly with the introduction of a radioactive source, we are told. There are no videos, or even pictures of the thing running, but we found this one that is pretty darn cool. Maybe all that spark-gap related RF killed their camera or something, their page at least promises videos soon.

In the mean time check out Truely Mad Scientist’s LVL1 Splinter Group’s ionizing cloud chamber for more radioactive fun.

An actively cooled cloud chamber

This cloud chamber is designed to keep the environment friendly for observing ionizing radiation. The group over at the LVL1 Hackerspace put it together and posted everything you need to know to try it out for yourself.

A cloud chamber uses a layer of alcohol vapor as a visual indicator of ionizing particles. As the name suggests, this vapor looks much like a cloud and the particles rip though it like tiny bullets. You can’t see the particles, but the turbulence they cause in the vapor is quite visible. Check out the .GIF example linked at the very bottom of their writeup.

The chamber itself uses a Peltier cooler and a CPU heat sink. The mounting and insulation system is brilliant and we think it’s the most reliable way we’ve seen of putting one of these together. Just remember that you need a radioactive source inside the chamber or you’ll be waiting a long time to see any particles. They’re using a test source here, but we saw a cloud chamber at our own local Hackerspace that used thoriated tungsten welding rods which are slightly radioactive.

[Thanks JAC_101]