The double focusing monochromator on MACS helps the instrument make the most of the PeeWee cold source by focusing the cold neutrons on the sample for increased flux or on the detectors for enhanced resolution.
The monochromator was built fifteen years ago and uses a collection of 32 motors to position HOPG crystals for energy focusing in the scattering plane and sagittal focusing out of that plane. When the system was originally built, each motor had an independent motor controller whose communications were bussed together using the RS485 electrical standard. That constellation of motors was managed by a large Labview application which calculated motor angles for the desired energy and focusing mode. As the motor controllers used in the apparatus are obsolete and the supervisory application has some demonstrable inefficiencies which compromise instrument performance, we elected to adapt its control electronics to use the NCNR facility standard VIPER motor control application.
The new NICE instrument control system manages focusing of the DFM along with all other motions on the instrument. It provides a live cartoon representation of the entire instrument which updates live as it moves. This features a detailed, accurate, representation of DFM showing every motor's position, providing limit and positional information on mouse-over and showing top-down, focused blade projections/shadows.