The effect of misalignment errors in optical elements of VUV polarimeter

We have designed a Vacuum Ultra Violet polarimeter for Indian Synchrotron Radiation Source Indus-1. This polarimeter will be installed on a toroidal grating monochromator-based beamline. Polarimeter consists of four-mirror phase retarder and three-mirror linear polarizer. Three-mirror linear polarizer has glancing angles of incidence 23°, 46° and 23°, working in 200–1100 Å wavelength region, with linear polarizence greater than 90%. Detailed ray-tracing analysis was carried out to find the effect of various misalignment errors in each of the optical element of the polarimeter. It is found that misalignment errors in optical element of the polarimeter affect only the beam spot position and do not affect the spot size, polarization state and photon flux of outgoing beam, substantially. Accuracies in the linear and angular positions of optical elements in phase retarder and linear polarizer must be very precise to perform ellipsometric experiments. Tolerance limit for various misalignment errors has been obtained. Required accuracy in angular position around X-axis is more than that required in angular position around Z-axis.