Lawrence Berkeley National Laboratory

In next generation high repetition rate FELs, beam energy loss due to resistive wall wakefields will produce significant amount of heat. The heat load for a superconducting undulator (operating at low temperature), must be removed and will be expensive to remove. In this paper, we study this effect in an undulator proposed for a Next Generation Light Source (NGLS) at LBNL. We benchmark our calculations with measurements at the LCLS and carry out detailed parameter studies using beam from a start-to-end simulation. Our preliminarym results suggest that the heat load in the undulator is about 2 W/m or lower with an aperture size of 6 mm for nominal NGLS preliminary design parameters.