Intrabeam scattering (IBS) is an effect in accelerator physics where collisions between particles couple the beam emittance in all three dimensions.
In proton accelerators, intrabeam scattering causes the beam to grow slowly over a period of several hours.
In circular lepton accelerators, intrabeam scattering is counteracted by radiation damping, resulting in a new equilibrium beam emittance with a relaxation time on the order of milliseconds.
Intrabeam scattering creates an inverse relationship between the smallness of the beam and the number of particles it contains, therefore limiting luminosity.
The two principal methods for calculating the effects of intrabeam scattering were done by Anton Piwinski in 1974[1] and James Bjorken and Sekazi Mtingwa in 1983.
This means that its effects diminish with increasing beam energy.
Other ways of mitigating IBS effects are the use of wigglers, and reducing beam intensity.
Transverse intrabeam scattering rates are sensitive to dispersion.
Intrabeam scattering is closely related to the Touschek effect.
The Touschek effect is a lifetime based on intrabeam collisions that result in both particles being ejected from the beam.
The betatron growth rates for intrabeam scattering are defined as, The following is general to all bunched beams, where
are the momentum spread, horizontal, and vertical are the betatron growth times.
One may also the express conservation of energy in IBS in terms of the Piwinski invariant where
Intrabeam scattering is an important effect in the proposed "ultimate storage ring" light sources and lepton damping rings for International Linear Collider (ILC) and Compact Linear Collider (CLIC).
Experimental studies aimed at understanding intrabeam scattering in beams similar to those used in these types of machines have been conducted at KEK,[6] CesrTA,[7] and elsewhere.