Report on Single and Multiple Intrabeam Scattering Measurements in IOTA Ring in Fermilab

Abstract

The study of single and multiple intrabeam scattering was carried out in the IOTA ring at Fermilab. The report discusses the results of the measurements and outlines still unresolved problems

Measurements of undulator radiation power noise and comparison with $\textit{ab initio}$ calculations

“…Additional negative effects include the errors in the light focusing optics, calibration errors of the SLMs, and possible Twiss beta-function errors. The SLMs at locations with larger beta-functions (M4L, M1L) provide estimates for y that agree better with the theoretical predictions [42] at lower beam currents, and with the emittance estimates presented below in this paper. Nevertheless, we cannot state that the SLMs could provide a reliable estimate for y during our experiment.…”

“…Typically, the combined population of the remaining 3 buckets was no more than a few percent. At the beam currents studied in our experiment (1-3 mA), the beam lifetime is determined solely by Touschek scattering [42,44]. In general, the momentum acceptance is a function of the position along the ring.…”

“…In addition, we made an independent estimate of the vertical emittance y of the flat beam based on the beam lifetime, see Appendix D for details. At the beam current of 2.66 mA, the beam lifetime is solely determined by Touschek scattering [37,42,44]. The Touschek lifetime is a function of beam emittances and bunch length.…”

Transverse beam emittance measurement by undulator radiation power noise

“…In the first case, we consider a strongly coupled [27,28] transverse focusing optics in IOTA, which was specifically designed to keep the two mode emittances equal 1 = 2 = . This was empirically confirmed to be true with a few percent precision.…”

“…The vertical emittance y of the flat beam in IOTA could also be estimated from the measured beam lifetime |I/( dI/dt )|, assuming that it is determined solely by Touschek scattering [32], which is a good approximation at beam currents I > ∼ 0.5 mA [28]. In storage rings, the Touschek lifetime is determined by the effective momentum acceptance δ (eff) acc [33], which is smaller than or equal to the rf bucket half-height, δ rf = 2.8 × 10 −3 in IOTA.…”