Automated thickness measurement of targets and degraders

With the Fragment Separator (FRS) at the Gesellschaft für Schwerionenphysik, radioactive-heavy-ion beams can be prepared to study the properties of and reactions with relativistic exotic nuclei. The quality of this beam depends crucially on the perfection of the energy degraders, which are necessary for slowing down the heavy ions according to their mass and charge, and therefore, act as variable ion-optical devices. The accuracy of the energy adjustment and the perfection of isotope separation depends on the thickness of the degrader parts as a lateral function. ort on the set-up and testing of an automated target scanner with a positioning accuracy of 2–3 μm and an accuracy in thickness measurement of <1 μm. Simultaneously, the two surfaces of any sample are measured and from the two signals, the local thickness is calculated for variable geometries and sizes fully automatically. The target scanner works purely mechanically, which means that there are no special requirements concerning the properties of the surfaces to be measured. The only restrictions are for very ductile materials and extremely sensitive surfaces.