X-Ray Production--The X-Ray Tube

X-rays are produced when fast moving electrons interact with atoms of a high atomic number target.

Whenever a potential difference is established between the cathode and anode of an x-ray tube the negatively charged electrons move rapidly from cathode to anode. The fancy physics term--potential difference simply means that the kilovolatge selected at the operator's console makes the anode highly positive with respect to the cathode.

Opposites attract---so the electrons at the cathode are strongly attracted to the anode and rush across at a very high velocity as soon as the potential difference is established (when you press the exposure button).

Whenever you select a higher kV the potential difference increases along with the energy of the electrons. This results in higher energy x-rays being produced.



In the video, the waveform diagram at the top of the screen shows how the voltage supply changes as the exposure progresses. The waveform shown is single phase, full wave rectified. The voltage varies in intensity from zero to peak intensity and back to zero in a repeating pattern.

Note that the x-rays produced (shown on the oscilloscope at the bottom of the screen) vary in intensity in a similar pattern to the voltage.

It is very important to understand how the various voltage waveforms (single phase or three phase) affect the quality and quantity of x-rays produced.