Large Mechanical Rotating Platform

 The rotational platform was designed for use at Spring8 to allow for the rotation of the beamline components following a diamond monochromator to maintain system alignment over the range of beam energies. A 5-phase stepper motor drives the platform with an effective open loop resolution of .002 degrees through a chain drive. A rotary encoder can be used both as a digital readout of the position and to close the positioning loop for a system accuracy of up to .0005 degrees. The machine base is composed of polymer concrete with mounting surfaces ground to +/-20µm and combined with high precision crossed linear recirculating bearing rails to give the total system straightness of trajectory of +/- 50µm over the 36 degree arc.