Coolidge Tube
Every hospital X-ray machine is a descendant of the Coolidge tube. This simulation shows electrons boiling off a heated filament, accelerating across a large potential difference and slamming into a tungsten target to produce X-rays.
How to use this simulation
- Change the filament current to control beam intensity
- Set the accelerating voltage to control X-ray energy
- Choose different target materials
What to look for
- Filament current governs how many X-rays are produced, not how energetic they are
- Accelerating voltage sets the maximum photon energy
- The vast majority of the input energy ends up as heat in the target
The physics behind it
The heated filament releases electrons by thermionic emission, and a potential difference of tens of kilovolts accelerates them to kinetic energy eV. Striking the target, they decelerate abruptly and radiate X-rays. Efficiency is low — over 99% of the energy becomes heat, which is why the tungsten anode is angled and rotated to spread the load.