DISCLAIMER!!!: This project can be EXTREMELY dangerous if you do not know what you are doing, in the case of this system, the x-rays are really the least of the problem, assuming you have something to protect yourself with. However a flyback transformer can give you a nasty shock that could even kill you in some cases. The X-ray emission from this project is not dangerous if you understand the physics and protect yourself from it. Regardless, shielding is a necessity. I am NOT responsible for any damages to people or property if you attempt this.
This is an Instructable covering the first part of a project I have wanted to do for some time now. After watching various videos and studying up on how x-rays were produced and interacted with the world around them, I decided I would very much like to experiment with them, as I have a well vested interest in high energy physics and electronics. I did not wish to spend many hundreds of dollars or possibly thousands on a real x-ray setup, as I wanted to experiment now and wished to see if I could produce them cheaply, reliably, and repeatably with parts I already had or could very easily acquire.
As for background, X-rays are very high energy photons produced when an accelerated electron strikes something and returns to its ground state. So to produce them, you must accelerate electrons to an appropriate energy to release an x-ray. This energy is measured in electron volts, or eV. There are also two categories of x-rays that we will associate with; Soft x-rays, and hard x-rays. "Soft" or "Low energy" x-rays are produced at around 800 eV to 5 KeV, while so called "Hard" or "high energy" x-rays are produced at energies greater that 5 KeV, upwards to 100 KeV. Soft x-rays are produced by this project, and are unable to penetrate objects as well as hard x-rays, and are often absorbed in air or your object of study. Therefore they are not typically used for imaging, due to scattering and absorption. Hard x-rays can be absorbed or pass through different materials, and their different rates of attenuation can show images when projected at a screen sensitive to x-rays. Essentially like shining a light on something and creating a shadow, materials that attenuate hard x-rays more readily will show up white, as x-rays have not penetrated through that material and made it to your imager, Whilst when hard x-rays do penetrate through, they hit your imager and leave no shadow. The x-rays produced by this system will typically be absorbed in air or water due to their relatively low energy, and are not useful for imaging, however you can still measure these x-rays, and I will speak more of this in the other part of this project, the detector.
*soft x-rays can be considered much more dangerous due to their higher rates of absorption, so care must be taken, and shielding worn or placed between you and the emitter.*
So came the first component; the tube. I am an avid collector of different valves and interesting vacuum or gas filled electron tubes. It so happened that I had a High voltage beam triode, which when operated in a cold cathode configuration, meaning the cathode was not boiling off electrons due to thermionic emission, I could accelerate electrons to an appropriate High energy for x-ray production.
My source is a High voltage beam triode from RCA, The 6BK4C 6EL4A. This tube is very well suited for this since it has; 1. A physically far apart Anode and Cathode, this will prevent arc out and degradation. 2. A well documented datasheet that states its level that it produces X-rays at. 3. It is robust, and simple.
There is one drawback to this particular tube, and that is that it is a revised version of a previous tube. It is a revision equipped with leaded glass to reduce x-ray emission. Nevertheless the stated production rate is somewhere in the neighbourhood of 2 rads per hour. The leaded glass will not prove to be a terrible hindrance, as the tube is quite active.