Basics of X-ray physics
X-ray production
X-rays are produced within the X-ray machine, also known as an X-ray tube. No external radioactive material is involved.
Key points
- X-rays are formed as required in an X-ray tube
- X-rays are produced by interaction of accelerated electrons with tungsten nuclei within the tube anode
The X-ray tube
A small increase in the filament voltage (1) results in a large increase in tube current (2), which accelerates high speed electrons from the very high temperature filament negative cathode (3) within a vacuum and towards a positive tungsten target anode (4). This anode rotates to dissipate heat generated. X-rays are generated within the tungsten anode and an X-ray beam (5) is directed towards the patient.
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X-rays are generated via interactions of the accelerated electrons with electrons of tungsten nuclei within the tube cathode.
X-ray generation
When a high energy electron (1) collides with an inner shell electron (2) both are ejected from the tungsten atom leaving a 'hole' in the inner layer. This is filled by an outer shell electron (3) with a loss of energy emitted as an X-ray photon (4).