Measurements and simulations of electron-cloud-induced tune shifts and emittance growth at CesrTA

Abstract

Extensive measurements of electron-cloud-induced betatron tune shifts and emittance growth are presented for trains of positron and electron bunches at 2.1 and 5.3 GeV at various bunch populations. Measurements using a witness bunch with variable distance from the end of the train and variable bunch population inform the study of cloud decay and the pinch eect. Improved electron cloud buildup modeling using detailed information on photoelectron production properties obtained from recently developed simulations successfully describes the tune shift measurements after determining ring-wide secondary-yield properties of the vacuum chamber by fitting the model to data. Space-charge electric field maps of the cloud from the validated model are then incorporated into a multiparticle tracking simulation of the beam through the lattice with electron cloud elements in the dipoles and field-free regions. The simulations predict emittance growth in agreement with the measurements.