Accelerator Seminar

Studies on the reconstruction of the 6D phase space

by Simon Lauber


Here at GSI a prototype cryomodule (Advanced Demonstrator) for the superconducting (SC) continuous wave (CW) Helmholtz Linear Accelerator (HELIAC), previously called CW-Linac, is under construction. A transport line, comprising quadrupole lenses, rebuncher cavities, beam steerers and sufficient beam instrumentation has been built to deliver the beam from the GSI 1.4 MeV/u High Charge Injector (HLI) to the Advanced Demonstrator, which offers a test environment for the Advanced Demonstrator and its SC CW multigap cavities. In order to achieve proper phase space matching to the cavities, the incoming beam must be characterized in detail. During previous comissioning runs, the phase projection of the bunch has been been measured with a non destructive bunch shape monitor (BSM). The BSM offers a sufficient spatial resolution to use it for reconstruction of the bunch shape in the longitudinal phase plane. Therefore, different bunch projections were obtained by altering the voltage of two rebunchers. These measurements were combined with dedicated beam dynamics simulations using the particle tracking code Dynamion. Thus, the longitudinal bunch density distribution at the exit of HLI-IH cavity could be fully characterized by employing a Non-Negative Least Squares algorithm. Independent measurements of the beam profile at the reconstrution location are available for confirmation of the reconstruction results.