Instructables

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.



PREFACE:
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.


 
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kfoxley5 months ago

This is a really interesting instructable. As a radiologic technologist, though, I have a problem with your explanation of the physics behind "hard" and "soft" xray. X-rays do not reflect. They can, at times, and at low energies, "scatter" due to the way they interact with the electrons (or protons/neutrons) in the atoms they hit. Low energy x-ray is more susceptible to scatter because it is more likely to attenuate in the subject being radiographed.

A radiograph is essentially a shadow. Things that are white are that way because the x-ray has attenuated in that particularly dense subject material: bone, barium, dental fillings, and to a lesser extent, soft tissue, etc. Things that are black are so because the x-ray has passed through and made it to the imaging plate (whether digital or film) Xray passes easily through air and fat, this is why your lungs appear black (with some markings) air bubbles in your stomach will appear when you're standing for your chest xray, etc.

So it is essentially not a matter of your low-output x-ray being 'absorbed' by the subject, but rather that your source is powerful enough to project the photons through your subject matter and onto the film, thereby leaving the indelible mark of its shadow in your silver halide.

The risk of using this sort of device for medical imaging (which would not be legal or safe!) is that your x-ray photons would indeed be absorbed, and in their attenuation, be far more dangerous to your bodily cells than regular, high-power medical imaging. Absorbed x-ray photons essentially equate to 'dose'.

It's best to think of it in terms of a shotgun blast into ballistics gel- a very low-powder load (as this would be) would have much of the shot stuck in the gel, where it can do damage. A high-powder load (as with medical imaging) would pass through, and given the specific application is precisely calibrated to achieve the best image possible while still giving the patient the smallest possible 'dose' of radiation. I hope this has helped. For further information, auntminnie.com is a great resource, as well as any books by Stuart Bushong and Carlton-Adler.

SpectrHz (author)  kfoxley5 months ago

Hi! thank you very much for the comment, it is very in depth and excellent information!

I will be the first to admit I do not know everything and have a lot to learn, as for the hard and soft explanation I took that from someone else, and it is certainly not a good one, however you have given me more insight. I am certainly not going to use this for medical imaging, as since it is not a point source, and would be rather difficult to use, if not impossible (nor am I interested). I'm not totally sure if these x-rays are of a high enough energy to light my cassette... I will keep improving this, it isn't finished, after all.

-SpectrHz

rimar20008 months ago

Very interesting!

SpectrHz (author)  rimar20008 months ago

Thank you :)