High-Accuracy Angle Generator for Precision Measurements

A lack of extreme angular metrology accuracy better than 50 nrad is limiting progress in molecular characterization by x-ray diffraction for important industrial fields such as material science and biotechnology. If we want to advance these fields, a high-accuracy angle generator for characterizing the metrology device across its entire measuring range must be a part of the national metrology tool set. At present, no such tool exists at the 50 nrad accuracy level. Using an established calibration technique, we will use an optimized arrangement of the minimum necessary number of angle encoder read heads optimally positioned around a rotary table encoder ring to minimize calibration error propagation. An arrangement that, thus far, has not been realized by any other group. The removal of the graduation errors of the encoder ring has been shown to improve the angular position uncertainty by a factor of approximately 800 and we will compare our results to these prior results. This work will enable us to make additional improvements and extensions for a full realization of a prototype high-accuracy angle generator.