Designing a Motorised Angular Control for Reflective Grating Monochromator

In this project, a motorized angular control tool for the monochromator had been devised based on a reflecting diffraction grating. A study of the diffraction equation used for the grating-based monochromator was performed. Some of the limits for the angular control had been estimated and compared. An exploration of stepper motor was carried out. Based on the existing resources in the laboratory, a diffracting rotating stage with L=70 mm and R = 100mm, coupled with a precise 5-phase stepper motor of 1000 steps/rev, was sufficient to reach a resolution of 0.003 nm. For the purpose of keeping track of step number while the diffracting grating rotated around the centric vertical axis, a Labview program to control the 5-phase step motor had also been developed. A two-point calibration scheme can be readily adopted with a computerised and motorised interface control written in Labview language.