I have recently built a little particle accelerator, which is not as complicated as it seems.
My purpose was to accelerate electrons and collide them with a dense target in order to produce bremsstrahlung radiation. This is usually done using a heated filament and a positively charged metal plate in a vacuum.
Many different cheap X-rays tubes can be found on the Internet, but I tried building one myself.
I used a light bulb, an old grayscale CRT monitor, and some aluminum foil.
Read more about it in my article: Particle accelerator