Synchrotron radiation
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Synchrotron radiation is electromagnetic radiation, similar to cyclotron radiation, but generated by the acceleration of relativistic electrons (i.e., moving near the speed of light). The radiation typically includes radio, optical, x-rays, and gamma rays. These electrons are accelerated either (a) along a straight line such as in a linear accelerator or across a plasma double layer, or (b) along a circular or helical path by a magnetic field at constant speed, where they experience an acceleration of constant magnitude, but whose vector tip executes a circle, so its direction changes, (c) Decelerating electrons quickly by allowing them to hit a sold metal target, in which case the radiation is also called Bremsstrahlung radiation. (The most technical sense of Bremsstrahlung covers all synchrotron radiation.)
Relativistic electrons moving in a circular or helical path in a magnetic field emit electromagnetic radiation (i.e., photons) in a narrow cone in the forward direction at a tangent to the orbit.
Synchrotron radiation is characterised by:
- High brightness and intensity, often many times more than with x-rays produced in conventional x-ray tubes;
- High collimation, that is, restriction to beams;
- The production of a wide range of energy levels (from several to several thousand electron volts);
- A high level of polarisation;
- Emissions possible in very short pulses (as little as a nanosecond, or a billionth of a second);
- Brilliance of about <math>10^{14}<math>.
As mentioned above, bending electromagnets are usually used to generate the radiation, but to generate stronger radiation, another kind of device, called an insertion device, is sometimes employed. This device is either an undulator or a wiggler. Each is composed of many magnets that have a special repeating row of N and S poles. The difference between an undulator and a wiggler is the intensity of the magnetic field they create.
Synchrotron radiation can be generated by astronomical structures and motions. Synchrotron radiation is also generated by plasma double layers, an electrostatic structure across which there is a potential difference that accelerates ions and electrons in opposite directions.
See also
- Synchrotron light for applications of synchrotron radiation and synchrotron for this type of particle accelerator
External links
- Synchotron radiation (http://ychenie.net)de:Synchrotronstrahlung