Bremsstrahlung is electromagnetic radiation (as are X-rays and gamma rays) produced by the acceleration or deceleration of moving charged particles, such as electrons or positive ions. The word ‘bremsstrahlung’ is German and literally means ‘braking radiation’. Bremsstrahlung is produced when, for example, a high energy electron (or beta particle) is slowed down in matter by the interaction between the electric field of the electron and that of the atomic electrons and nuclei in the matter. The resulting bremsstrahlung has a continuous energy spectrum between zero and the electron’s initial kinetic energy.
The existence of bremsstrahlung leads to problems in shielding sources of high energy beta particles. It is possible to determine the thickness of the shield necessary to stop all beta particles of a particular energy. The bremsstrahlung produced however, being electromagnetic radiation, can travel much further than the initial electron which produced it. It will be attenuated in an exponential manner and cannot be stopped completely by extra shielding; but it can be reduced to an acceptable level by an appropriate thickness.
Bremsstrahlung is also known as ‘synchrotron radiation’ when it is produced by the acceleration of charged particles in a particle accelerator. Some particle accelerators are constructed specifically as sources of synchrotron radiation.