Absolute angular positioning in ultrahigh vacuum

Commercially available angular resolvers, which are routinely used in machine tools and robotics, are modified and adapted to be used under ultrahigh‐vacuum (UHV) conditions. They provide straightforward and reliable measurements of angular positions for any kind of UHV sample manipulators. The corresponding absolute reproducibility is on the order of 0.005°, whereas the relative resolution is better than 0.001°, as demonstrated by high‐resolution helium‐reflectivity measurements. The mechanical setup and possible applications are discussed.