Intrabeam Scattering Analysis of Measurements at KEK's ATF Damping Ring

Abstract

We derive a simple relation for estimating the relative emittance growth in x and y due to intrabeam scattering (IBS) in electron storage rings. We show that IBS calculations for the ATF damping ring, when using the formalism of Bjorken-Mtingwa, a modified formalism of Piwinski (where η 2 /β has been replaced by H), or a simple high-energy approximate formula all give results that agree well. Comparing theory, including the effect of potential well bunch lengthening, with a complete set of ATF steady-state beam size vs. current measurements we find reasonably good agreement for energy spread and horizontal emittance. The measured vertical emittance, however, is larger than theory in both offset (zero current emittance) and slope (emittance change with current). The slope error indicates measurement error and/or additional current-dependent physics at the ATF; the offset error, that the assumed Coulomb log is correct to within a factor of 1.75.

Intrabeam Scattering in the NLC Main Damping Rings

“…For gaussian bunches, the factor f CL = 1. However, IBS populates the tails of the bunch distribution, and this leads to a reduction in the growth rates of the core emittances; this may be represented by a reduction in the factor f CL to a value as low as 0.5 [5].…”

“…We used a potential well factor f pw of 7×10 -11 . We assume that the vertical emittance is dominated by betatron coupling, and the growth in vertical emittance is therefore simply given by (5).…”

“…We again assume that the vertical emittance is dominated by betatron coupling, so that the vertical emittance is given by (5). This will be the case if the rms vertical dispersion is corrected to around 1.5 mm or better.…”

Bunch characteristics evolution for lepton and hadron rings under the influence of the intra-beam scattering effect

“…Later, Bjorken and Mtingwa (BM) [38] used a different approach to describe the effect, taking into account the strong focusing effect. The Modified Piwinski (MP) method [39] that includes the strong focusing effect, was developed by Bane. Some approximations of these theories are the high energy one by Bane (Bane) [39] and the completely integrated modified Piwinski (CIMP) [40].…”

“…The Modified Piwinski (MP) method [39] that includes the strong focusing effect, was developed by Bane. Some approximations of these theories are the high energy one by Bane (Bane) [39] and the completely integrated modified Piwinski (CIMP) [40]. These approximations are valid under certain conditions.…”