Is Your Tape Dispenser Radioactive?

March 11, 2022 by 26 Comments

Do you have anything radioactive in your house? Most people will say no, but they are probably wrong. A host of things ranging from glow-in-the dark timepieces to smoke detectors have some amount of radioactivity. But as [Wheeler Scientific] points out, so do some old Scotch tape dispensers. You can watch the video, below.

The dispenser in question is the C-15 which was very common around offices, military bases, and homes for years. They were made up until the 1980s. You have to wonder why a tape dispenser would be radioactive, and [Wheeler] has the explanation.

When you pull tape from the dispenser, you don’t want the dispenser to slide around the desk, so it needs to be heavy. But no one wants to have a giant dispenser nor do you want to pay for one made from a dense metal. So the plastic dispenser contains a ballast to make it heavier. In the case of the C-15 that ballast is thorium-containing monazite sand. A vintage counter shows the radioactivity which isn’t much, of course, but still way less than the ordinary sand used in newer models. You can also see in the video that the material is paramagnetic.

Monazite used to be a primary source of lanthanides but getting rid of the thorium led to alternate sources in the 1960s although it is still used as an ore for thorium. We know some lenses are radioactive. If you want to search your home for radioactivity and you don’t have a Geiger counter, you don’t need much to build one.

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As apples travel down the conveyor belt, they are scanned using InGaAs and CMOS cameras. The InGaAs camera will show defects beginning to form under the skin that a human eye cannot see; the CMOS camera will show visible defects. (Credit: Hamamatsu)

Shining A Different Light On Reality With Short-Wave Infrared Radiation

February 3, 2022 by 23 Comments

As great as cameras that operate in the visual light spectrum are, they omit a lot of the information that can be gleaned from other wavelengths. There is also the minor issue that visibility is often impacted, such as when it’s raining, or foggy. When this happens, applications such as self-driving cars which rely on this, have a major issue. Through the use of sensors that are sensitive to other wavelengths, we can however avoid many of these issues.

Short-wave infrared radiation (SWIR) is roughly the part of the electromagnetic spectrum between 1.4 μm – 3 μm, or 100 THz – 214 THz. This places it between visible light and microwaves, and above long-wave IR at 20 THz – 37 THz. LWIR is what thermal cameras use, with LWIR also emitted by warm objects, such as the human body.

SWIR is largely unaffected by water in the atmosphere, while also passing through materials that are opaque to visible light. This allowing SWIR to be used for the analysis and inspection of everything from PCBs and fruit to works of art to capture details that are otherwise invisible or very hard to see.

Unfortunately, much like thermal camera sensors, SWIR sensors are rather expensive. Or they were, until quite recently, with the emergence of quantum-dot-based sensors that significantly decrease the costs of these sensors.

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SHERLOC And The Search For Life On Mars

January 27, 2022 by 24 Comments

Humanity has been wondering about whether life exists beyond our little backwater planet for so long that we’ve developed a kind of cultural bias as to how the answer to this central question will be revealed. Most of us probably imagine that NASA or some other space agency will schedule a press conference, an assembled panel of scientific luminaries will announce the findings, and newspapers around the world will blare “WE ARE NOT ALONE!” headlines. We’ve all seen that movie before, so that’s the way it has to be, right?

Probably not. Short of an improbable event like an alien spacecraft landing while a Google Street View car was driving by or receiving an unambiguously intelligent radio message from the stars, the conclusion that life exists now or once did outside our particular gravity well is likely to be reached in a piecewise process, an accretion of evidence built up over a long time until on balance, the only reasonable conclusion is that we are not alone. And that’s exactly what the announcement at the end of last year that the Mars rover Perseverance had discovered evidence of organic molecules in the rocks of Jezero crater was — another piece of the puzzle, and another step toward answering the fundamental question of the uniqueness of life.

Discovering organic molecules on Mars is far from proof that life once existed there. But it’s a step on the way, as well as a great excuse to look into the scientific principles and engineering of the instruments that made this discovery possible — the whimsically named SHERLOC and WATSON.

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An alpha spark detector

Detecting Alpha Particles Using Copper Wire And High Voltage

January 22, 2022 by 14 Comments

If you want to measure radioactivity, nothing really beats a Geiger counter: compact, rugged, and reasonably easy to use, they’re by far the most commonly used tool to detect ionizing radiation. However, several other methods have been used in the past, and while they may not be very practical today, recreating them can make for an interesting experiment.

[Mirko Pavleski] used easily obtainable components to build one such device known as an alpha radiation spark detector. Invented in 1945, a spark detector contains a strong electric field into which discharges are triggered by ionizing radiation. Unlike a Geiger-Müller tube, it uses regular air, which makes it sensitive only to alpha radiation; beta and gamma rays don’t cause enough ionization at ambient pressure. Fortunately, alpha radiation is the main type emitted by the americium tablets found in old smoke detectors, so a usable source shouldn’t be too hard to find.

The construction of this device is very simple: a few thin copper wires are suspended above a round metal can, while a cheap high-voltage source provides a strong electric field between them. Sparks fly from the wires to the can when an alpha source is brought nearby; a series resistor limits the current to ensure the wires don’t overheat and melt.

Although not really practical as a measurement device, the spark detector can nevertheless be used to perform simple experiments with radioactivity. As an example, [Mirko] demonstrates in the video embedded below that alpha particles are stopped by a piece of paper and therefore present no immediate danger to humans. The high voltage present in the device does however, so care must be taken with the detector more than with the radiation source.

We’ve seen several homebrew Geiger counters, some built with plenty of duct tape or with the good old 555 timer. But you can also use photodiodes or even certain types of plastic to visualize ionizing radiation.

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Forget Radio! Transmitting With Neutrons

November 14, 2021 by 50 Comments

Throughout history, people have devised ways to send information across long distances. For centuries we relied on smoke signals, semaphores, and similar physical devices. Electricity changed everything. First the telegraph and then radio transformed communications. Now researchers at the University of Lancaster have demonstrated another way to send wireless data without using electromagnetic radiation. They’ve harnessed fast neutrons from californium-252 and modulated them with information with 100% success.

The setup was interesting. The radioactive material was encased in a cubic meter steel tank filled with water. A pneumatic system can move the material to one edge of the tank which allows fast neutrons to escape. A scintillating detector can pick up the increased neutron activity. It seems like it is akin to using what hams call CW and college professors call OOK (on off keying). You can do that with just about anything you can detect. A flashlight, knocking on wood, or — we suppose — neutrons.

We wondered what the practical application of this might be. The paper suggests that the technique could send data through metal containment structures like those of a nuclear reactor or, perhaps, a spacecraft where you don’t want anything unnecessarily breaching the containment. After all, neutrons cut through things that would stop a conventional radio wave cold.

It seems like you only have to prove you can detect something to make this work — it really doesn’t matter what it is you are detecting. It seems like it would be much harder to do more advanced types of modulation using neutrons. Maybe this is why we don’t hear aliens. They are all Morse code operators with neutron-based telegraphs.

Recreating Ben Franklins kite experiment with a drone

Drone Replaces Kite In Recreation Of Famous Atmospheric Electricity Experiment

October 1, 2021 by 4 Comments

Finally, someone decided to answer the question that nobody was asking: what if [Benjamin Franklin] had had a drone rather than a kite?

Granted, [Jay Bowles] didn’t fly his electricity-harvesting drone during a thunderstorm, but he did manage to reach some of the same conclusions that [Dr. Franklin] did about the nature of atmospheric electricity. His experimental setup was pretty simple: a DJI Mini2 drone with enough payload capacity to haul a length of fine-gauge magnet wire up to around 100 meters above ground level. A collecting electrode made of metal mesh was connected to the wire and suspended below the drone. Some big nails were driven into the soil to complete the circuit between the drone and the ground.

[Jay] went old-school for a detector, using a homemade electroscope to show what kind of static charge was accumulating on the electrode. Version 1 didn’t have enough oomph to do much but deliver a small static shock, but a larger electrode was able to deflect the leaves of an electroscope, power a beer can version of a Franklin bell, and also run a homemade corona motor. [ElectroBOOM] makes a guest appearance in the video below to explain the physics of the setup; curiously, he actually managed to get away without any injuries this time. Continue reading “Drone Replaces Kite In Recreation Of Famous Atmospheric Electricity Experiment” →

Review: What On Earth Is An Electromagnetic Radiation Tester And Why Would I Need One?

April 7, 2021 by 73 Comments

One of the joys of an itinerant existence comes in periodically being reunited with the fruits of various orders that were sent to hackerspaces or friends somewhere along the way. These anonymous parcels from afar hold an assortment of wonders, with the added element of anticipation that comes from forgetting exactly what had been ordered.

So it is with today’s subject, a Mustool MT525 electromagnetic radiation tester. At a cost not far above £10 ($13.70), this was an impulse purchase driven by curiosity; these devices claim to measure both magnetic and electric fields, but what do they really measure? My interest in these matters lies in the direction of radio, but I have never examined such an instrument. Time to subject it to the Hackaday treatment.

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