Topic : Studies of longitudinal dynamics of Landau cavity in electron storage ring

  

 Scope  

                        In synchrotron light source, the beam lifetime is one of the important beam parameters. In low-emittance storage ring of the third-generation light sources, the beam lifetime is usually dominated by Touschek scattering. In this study, the beam dynamics of the harmonic cavity will be investigated. The parameters of both active and passive operation will be optimized to cancel the slope of RF voltage and lengthen the bunch. The requirement and bunch lengthening effect of harmonic cavity will be estimated using analytical model with active mode operation. In passive operation, the harmonic voltage is generated from the beam itself. The Touschek lifetime increases are estimated for optimum and non-optimum voltage flattening. A tolerance of the operation will be studied in case that there is an imperfection on harmonic voltage via shunt impedance or beam current, and also a shift on detuning angle. Transient beam loading effect generated by the non-uniform filling pattern causes a variation of harmonic phase and reduces the lengthening effect as well as bunch lengthening effect crucially. The transient loading effects have been investigated using developed tracking code for uniform filling cases and a non-uniform filling cases. An increase of synchrotron frequency spread due to nonlinearity of the voltage giving to the bunch will be studied by using tracking simulation. The effect caused by reduction of harmonic voltage generated by lengthened bunch distribution is also estimated by applying iteration method to both analytical model and tracking code simulation.

  

 Supervisor  

                        Dr. Thanapong Phimsen
                        and SLRI researchers