Scaling of wakefield effects in recirculating linacs

Expressions for the induced energy spread and emittance degradation of a single bunch due to the longitudinal and transverse impedance of RF cavities at the end of a linac structure are presented. Scaling of the formulae with RF frequency is derived. Scaling of the threshold current for the multibunch, multipass beam breakup (BBU) instability in recirculating linacs with accelerator and beam parameters is also derived.