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DIY X-ray MachineThe other day I thought "wouldn't it be cool if I could make an X-ray machine for reverse engineering PCBs, etc". So I looked around and found an ancient Scientific American article. It seems that all one needs to produce X-rays is an HV supply and an evacuated tube containing a cold electron-emitting cathode and some kind of target anode. The guy in the article initially used a thermionic valve with some (all?) of its pins connected to the HV supply. The magnesium getter coating on the inside of the glass was used as the target, with some tin foil on the outside of the glass to sort of ground. It worked quite well. The article suggests that magnesium is important in some way, but does not supply any details. The guy got better results with a tube he had made at a local glass blower! It featured a molybdenum cathode and the same magnesium coating technology used in the valve. How the hell he evacuated it, or got hold of any molybdenum I have no idea. Of course this was 1960s America, where people could actually buy stuff and do things; not nanny-state UK, 2007 where you require a special license to buy toilet cleaner. The article is pretty vague - it doesn't even tell you the voltage required! Looking at the radiograph of the feeler gauge makes a convincing case for reverse engineering multilayer PCBs. Image processing to separate n layers of grey can't be that difficult. Then I stopped thinking about X-rays for a while, and did some real work. Then I saw an article on make about a guy making a cool lamp with nice dimmed bulbs with interesting filaments - something I've been thinking about since I saw a previous one. He used bulbs from a site I'd looked at when I got thinking about it the first time, so again I started browsing their more unusual bulbs. I saw this one and again I was thinking of X-rays. The inside is coated in aluminium. Will that work like magnesium? The two elements are pretty similar! Will the argon mess things up? What's the pressure in a light bulb? Do the electrons need a direct path anyway? How the hell does any of this X-ray business work?! No time to think about it now, but I am having difficulty retraining the urge to make an HV supply from an old microwave and connect various tube-related devices to it!
Submitted by jeff on Mon, 04/16/2007 - 17:31. categories [ ]
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bought'n x-ray tubes
you need pretty high vacuum to get any x-rays. they are generated when electrons are rapidly decelerated from high speed; the frequency is proportional to the atomic mass of the target (usually tungsten) and the velocity. and there just isnt enough time to get up to speed if they're running into air molecules. a light bulb won't work. however, some regular vacuum tubes such as from old TV's will give off x-rays when overdriven, but since its sorta hard to find them these days you can buy them from here: http://unitednuclear.com/xray.htm
he also sells zinc sulfide and other phosphorescent powder, which you might be able to use to make a phosphorescent screen, and then photograph that with a digital camera instead of messing with film.
uh, good luck.
Don't
Hi!
Don't do it. Please *really* understand what you are gonna do before trying to build and x-ray machine: x-rays are dangerous, you WILL need some sort of isolation (Pb?) chamber where you will put your X-ray machine and stuff, and, off course, you need to control the power of the thing because if it is too high, you can cause damage to yourself, or your future descendants (if you decide to have them).
Please, don't mess with high energy radiation unless you really understand it.
Regarts.
Chicken and egg
It's my firm belief that the only way I can *really* understand something is to build it!
I'm aware of the safety issues, however, and in the unlikely event of my actually getting round to building an X-ray machine I'll be very careful.
Thanks for your concern.
Jeff