Tuning and characterisation of Twente Wiggler

For correcting field errors in the Twente wiggler small metal shims were placed on the pole faces. When applied to correct errors in the on-axis field a large increase in the errors in the off-axis field was found. When instead errors in the off-axis field are corrected, the errors in the on-axis field are reduced as well. Only small corrections were locally required to make the errors in the on-axis field acceptable. The focussing strength of the wiggler has been measured in both transverse planes and was found to lead to a slightly elliptical shape for a matched electron beam. Longitudinal phase errors have been measured for the Twente wiggler and are negligible.