Measurement of Beam Size in Intrabeam Scattering Dominated Beams at Various Energies at CesrTA

Abstract

Recent reports from CesrTA have shown measurement and calculation of beam size versus current in CesrTA beams at 2.1 GeV. Here, the effect of changing the energy of Intra- beam Scattering-dominated beams is reported. IBS growth rates have roughly a γ −3 dependence. Measurements at 1.8, 2.1, 2.3, and 2.5 GeV are shown and compared with predictions from IBS theory. x, y , then the total emittance of the bunch can increase. The horizontal dispersion of CesrTA is rather large, with a rms value of 1 m and peaks at about 3 m. The rms Hx is 0.11 m and peaks at about 0.37 m. IBS has been measured to blow up the horizontal emittance to 3 times the single- particle emittance. In such beams, IBS, rather than photon emission, is the dominant source of horizontal emittance. Typical applications of IBS theory give a time rate of change in the beam emittances. In electron storage rings this growth rate competes with radiation damping resulting in new, usually larger, emittances. These larger emittances de- pend on the beam energy, single-bunch current, and machine optics. IBS is relevant in new low emittance colliders and storage rings, some now being commissioned and others in early stages of design (1). Collider luminosity and light source brilliance both depend on beam size. At the few GeV ener- gies targeted by these machines, IBS can dominate the beam size.