Alpha Radiation Visualizer
I started this project with more of an idea of creating a system that would visualize Cherenkov radiation via webcam utilizing a Gamma radiation source and heavy water in some heavy lead shielding to produce the tell tale bursts of blue light. Perhaps hook it up to the LCD window kit system we did and display it on the windowed screen. When I decided to ramp up the project and also was experimenting with other types and sources of radiation for the project I stumbled across a myriad of new ideas for possible systems with some far reaching and profound results. While this write-up is just discussing in detail the implementation of this apparatus for ones personal amusement via screensaver, there are other far reaching possibilities for this system I will discuss later in the article.
“The most absurd and reckless aspirations have sometimes led to extraordinary success.”
–marquis de vauvenargues
As stated in the introduction, this project was an accident. I did not intend to go down the path on which I eventually arrived. But ultimately it’s something I feel much better about publishing on the site as it’s a far safer project. While I am not playing with huge amounts of Gamma radiation in this project, it was the recklessness of that idea that led to this success.
The basic idea behind this project is using the built in CCD in a USB web camera as a medium for alpha radiation to interact with. The result is a visual presentation of pops and streaks of light as the partials interact with individual pixels of the CCD. While this has a very nice effect and makes for a fantastic “screen saver”, there are more practical and important possibilities with this project.
One of the applications I have envisioned for this project is a cheap and easy genuine random number generator. True random numbers in computing are nearly impossible, and successful solutions are very expensive systems based on radioactive decay or atmospheric measurements, for example. Using a small / relatively safe radioactive source and a high res CCD or CMOS sensor and assigning a value to each pixel and perhaps mixing in an algorithm or two with an inexpensive practical PCI card that is capable of generating genuine random numbers. Applications that could greatly benefit from this would be encryption, security applications, Computer AI and the Gambling establishment to name a few.
Check out http://www.vanheusden.com/ved/ for something you can apply now!
The Web Cam:
The heart of this system uses a Logitech quickcam 5000 for the interception of the alpha particles and the display of the results. The quality of this camera I have to point out is very high. The 1.3 megapixel image quality almost made me regret tearing it apart. But then I saw the lady there on the box cover smiling at me just egging me on (I wish she would stop. The project is complete). I would wager that Logitech never expected their camera to be used like this!
Total cost via NewEgg: $60.00
The Project Box:
This project box is a little large I admit. But for 3.00 at Radio Shack I couldn’t pass it up. The project box in this application doesn’t have to be a mid sized mysterious black box; you could actually fit everything back into the original web cam housing with great ease. But having a “mysterious black box” hooked up to your computer has a certain aesthetically pleasing air to it after all.
I know. I know. your first reaction to seeing that I am using copper as shielding is not a good one. You’re thinking “What a dumb ass, you should use lead, not copper!” well your right. and wrong. Alpha particles actually are stopped in their tracks by a mere sheet of paper. So why the shielding at all then? We’re actually shielding the camera from external electrical noise and not necessarily keeping the radiation in. By using copper shielding and connecting it to our common ground on the webcam itself, we are able to reduce the amount of external EMI and have a cleaner overall result. Cost for the shielding: $11.00, and there’s lots left over for other projects.
The Radiation Source:
So where does your somewhat normal run of the mill geek go to pick up there normal every day alpha radiation source? Well The Home Depot, of course! Smoke detectors for some time have had a radioactive source in them. Traditionally they use about 0.2 milligrams of Americium 241. Americium 241 is a synthetic element, and a strong alpha radiation source. Perfect for our application at hand as it is “relatively” safe to handle by a novice. But as it is a radioactive source, and does emit a small amount of gamma radiation it should be handled with care and only by someone educated in handling such materials. Smoke detector: $14.00
The Operation Begins…
This is the core of the system and therefore the first part of the system we get to take apart. The Logitech webcam is one of the best there is on the market, with a flexible shapeable stand that we will have to use in an upcoming project. One word for the wise with this project is to be vary careful with dissecting electronics. Do not disassemble this project with it plugged into your USB ports on your computer. Additionally, all circuit boards contain lead and other potentially dangerous chemicals. Do not eat or handle food while or after handling lead based circuit boards until you have washed your hands.
So here is the webcam disassembled. Removing outer casing, as well as unplugging the mic and photo button on top, you should have as bare bones of a camera as possible for this project. If you are planning on reinstalling the completed project into the camera body I recommend keeping track of all the parts and screws.
Here is a close-up of the camera board and lens. The lenses is basically a plastic housing screwed onto the board. The CCD the camera uses is actually surface mounted on the board and the plastic housing helps to protect it from dust and other contaminants. The lens is a variable focus lens and can be turned left and right to adjust focus (done at the factory).
By turning the lens counterclockwise you can actually unscrew it from the board assembly. In side the lens there is a lens that filters out infrared light that fills the majority of the lens body. If you press on the clear lens lightly it will pop the lenses out of the body making room for our radioactive components. Trash the lenses as they are not needed for this project.
Next up is the disassembly of the smoke detector to obtain our alpha source. We purchased the cheapest smoke detector we could find at our local hardware store. Now there are some smoke detectors that do not use radioactive components. The cheap detectors come in a paper box that can be opened. On the back side of the smoke detector you will find printed information if it contains americium as well as amounts.
Using a flathead screwdriver, depress the tabs on the back of the detector to remove the cover. Inside you will see a lot of empty space and a circuit board with a large metal housing on it.
Carefully remove the circuit board from the rest of the plastic housing. Our next step is to remove the metal housing from the circuit board for disassembly. To do this you could take the time to de-solder it and bend the metal tab, etc. I opted for the faster method as on this unit the solder tabs are close to the edges of the board. Using a good pair of wire cutters I simply cut through the board and metal flanges in one simple stroke.
With the metal housing removed the inner components are wedged into place. Using a flat head screwdriver pop the internals out of the housing. The tab at the bottom of this image contains a small circular metal item with an indented center. The center is the component that emits the alpha radiation, do not disassemble this. Just remove this from the tab.
Here is a close up of the metal wafer. In the center of the wafer in the small indent there is a small amount of the americium. The material around this acts as shielding and we not only want to keep it for that reason, but also for the added ease of mounting it into the lens. (Insert joke about glowing little green men here.)
Step one on the assembly is uniting the components finally. Here we have the wafer and the lens body side by side. You can see the wafer will seat perfectly inside the lens body.
Using a drop or two of superglue, secure the wafer inside the lens body. Take great care to make sure you get it as level as possible so you don’t have any dead spots on your ccd. Do not install until the glue is completely dry.
Screw the lens body back into the circuit board. Here, I have to also point out one other thing: The seal around the bottom of the lens mounting bracket and the circuit board is not very good. In fact it stinks. Usually this is not an issue. But this board has a green surface mounted LED on it on the right side there. This produces enough light that it seeps through the crack between the mount and the board making it impossible for the ccd to show the alpha particle interactions. To address this problem, I just smashed the LED, but I suppose if you wanted to be clever, as this LED does indicate status of the system being on, you could de-solder it, solder on some new leads, and then mount an LED on the box somewhere.
Another trip to our home improvement store resulted in this nice copper sheeting. This is used on roofs as flashing… but we will be using it for shielding. As stated before, this is not necessarily to shield against radiation leakage, but more to shield against EMI. Line the inside of the project box with the copper foil and attach some leads to it.
Place the camera into the case using some wire cutters to make a small notch in the side of the box for the wire to come out through. Using some electrical tape, wrap the camera board up to prevent any possible problems with it touching the shielding. Using some hot glue, secure the board in place making sure said board is not in contact with the shielding.
Finally close up the project box with the provided screws. This would be a good time to start thinking of strange things to stencil on the outside of the box. Connect this back to your computer to make sure it worked. I recommend using a hub inline between the computer and the mysterious black box for the test connection, as a short or bad ground can severely damage a computer. Using a hub inline will prevent this at the possible expense of the hub.
As you can see from this write up this is a simple project to construct. We assembled an additional version below of this project using a PCI USB card for further development as an internal project. O verall, I think this project was a resounding success. While I don’t plan on playing with radioactive materials as a common pastime, it’s still a good time with lots of potential applications.
Video of the project in action.
Here is a video clip of the system in action. We converted it to this animated Gif to conserve bandwidth and in doing so lost about 60% of the total interacts by losing most of the dimmer interactions. But it’s still cool. If you look closely you will be able to see the white flashes that are one pixel in size, as well as faint blue streaks. Iwill try to get a higher quality vid soon.
This project goes together so easily that I just couldn’t help taking a few minutes to order a USB card off Newegg. Basically, this is just a PCI USB card. We shortened the length of the USB cord to 1″ and mounted the camera to the USB card with some hot glue. I picked the card due to its “L” shape, which gives a natural place for the camera to sit while not taking space in other slots. We applied a layer of copper sheeting and grounded it to the screw on the card bracket to insure a good strong ground. Finally we coated everything we added with a thin layer of silicon to protect it from accidentally touching something else in the computer.