X ray production

X-ray production

Unit 20 strand 1 (P2)

X-rays were first discovered in 1895 by the German physicist William Roentgen, when using a Crookes tube

He called them ‘x’ rays, ‘x’ for ‘unknown’.

The first x-ray photograph: Roentgen’s wife Bertha’s hand

X-rays are produced when high-speed electrons hit a metal target. In medical x-rays this is usually tungsten. X-rays are electromagnetic radiation of high frequencies (1017-1020 Hz) Electrons are produced by thermionic emission. They are accelerated across the vacuum tube towards the positive (anode) target. The electrons strike the target and lose about 99% of their energy in low-energy collisions with the target atoms – this heats up the target. The remainder of the energy reappears as x-ray radiation. Overheating is prevented by using a rotating anode and circulating oil. Copper is used for the anode mountings.