Energy Acceptance in Electron Storage Rings

[dgonnella89]

I'm working on a research project involving calculations about various aspects of electron storage rings and have come across the term energy acceptance or energy aperture. Could someone explain to me what is meant by this term? It is used in a lot of literature but I haven't been able to find a good definition.

Thanks!

 

[Bob S]

Electron accelerators and storage rings are usually above 1 or 2 GeV. They are usually used for synchrotron radiation sources, external electron beams, or sometimes colliding beams. There are several facilities in the U. S.; Brookhaven, Argonne. Jefferson, Lawrence Berkeley, Cornell, Madison, to name a few. In addition to the longitudinal energy, the beams have transverse energy. This comes about because the electrons in the bunches, often about 1 nanoCoulomb (nC), are all mutually repelled by Coulomb forces, and therefore oscillate back and forth transversely, focused by the quadrupoles (strong focusing). The transverse aperture of the machine has an aperture limit, called the acceptance. The beam has a transverse size, called the emittance (units = mm-mrad). If the transverse emittance exceeds the acceptance, electrons are lost (hit the aperture). Similarly, in the longitudinal (energy) coordinate, electrons oscillate back and forth in the stable RF "bucket", and if the longitudinal emittance (units=eV-sec) exceeds the longitudinal acceptance, they are lost. Electrons continuously radiate away lots of energy (synchrotron radiation) and need to replace that energy every turn in RF cavities. An electron with above average energy takes longer to go around the ring ("above transition") and gets less acceleration the next time around (phase stability).
Bob S

 

[sir-pinski]

Energy acceptance, also known as energy aperture, is a crucial concept in electron storage rings. It refers to the range of energies that an electron beam can have and still remain stable in the storage ring. In other words, it is the maximum deviation from the ideal energy that the beam can have without experiencing significant loss of intensity or stability.

The energy acceptance of a storage ring is determined by various factors, such as the design of the magnets that guide the electron beam, the strength of the magnetic field, and the focusing and defocusing effects of the beam itself. A larger energy acceptance allows for a wider range of electron energies to be stored in the ring, which is important for many applications such as particle physics experiments or synchrotron radiation sources.

In order to maintain a stable beam, the energy acceptance must be carefully controlled and optimized. This is often achieved through precise tuning of the magnets and other parameters in the storage ring. Additionally, external systems, such as radio frequency cavities, can be used to compensate for any energy deviations and maintain the stability of the beam.

Overall, understanding and controlling energy acceptance is crucial for the successful operation of electron storage rings and is a key aspect of research in this field. I hope this explanation helps clarify the concept for your research project.