Electronics > Projects, Designs, and Technical Stuff
Homemade X-Ray Machine: Liftoff
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james_s:
I wouldn't worry about it, most of the stuff you'll find is 80s or later which is not going to have PCB oil. Even if it's an old one that does, it's not going to hurt anything as long as you leave it alone. The problem with PCBs is that they are extremely stable compounds that don't break down when they get in the ground so they end up in water supplies. It's not particularly dangerous stuff to handle but you don't want it in your food or water so disposal can be an issue.

Whatever the case just don't take the head apart, the oil filled ones are messy, the SF6 (gas) filled ones you'll let the gas out if you open the head. Either way the transformer will flash over if you try to run it in air. Also don't try to run one directly off the line, usually you need about 80V on the primary for full tube voltage and something similar on the filament. If you temporarily remove the aluminum filter from the output you can adjust the filament voltage by eye, it should glow about like a low wattage incandescent lamp, white hot, not the dull orange of most thermionic filaments. This is because an xray filament is pure tungsten.
AutogolazzoJr:
Is there any way to make the pictures sharper? any new form of imaging? The problem with the tube is that the x-rays diverge at a very wide angle. Prehaps moving the x ray source or thing being imaged a bit, and only having a small part of the object imaged? Kind of like a raster scan? Maybe there is a way to focus the x-rays? Thanks.
SilverSolder:

To sharpen the image - maybe try making a "pin hole camera" for X-rays?   Place the tube behind a lead plate with a small hole in it?

The idea is to make the X-ray source more like a point source, not a laser beam.
Wolfram:
You have to figure out where your lack of sharpness comes from. If you use a rectifier as an x-ray source then the x-rays will be coming from a broad area, leading to significant geometric unsharpness. To get the best possible results, place your imaged object as close to the screen as possible, and place the source as far away as practical. A pinhole to reduce the apparent source size as suggested by SilverSolder would also work. Both of these methods will of course also reduce your light yield, so you will be limited by camera noise and overheating of the tube. As suggested by James, a dental x-ray tube will yield superior results, I've attached some sample images taken with a dental x-ray tube on film and cassette screen.
james_s:
Sharpness is a combination of anode spot size and anode to subject distance. You can't do anything about the spot size as that's part of the tube design but you can move the tube further away. You will gain sharpness at the expense of needing longer exposure times.

There are other factors too, the grain of the phosphor screen, mammo screens have finer grain but they require longer exposures or more power. If you are imaging the screen with a camera that could be your limiting factor too.
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