BIGFOOT (LC)
ShalikaSingh - 22:35, Thursday 16 November 2023 (3350)
LC1 fast axis tuning

[Shalika, Marc]

The ellipticity after BS was ~0.31° and we weren't able to tune it to 0° and simultaneously keep azimuth after BS at 0°. The tuning was being done by Polarizer and HWP+QWP before BS. We finally decided to remove the polarizer. The tuning of ellipticity and azimuth after BS was then done using HWP and QWP (before BS) to have 0° in both ellipticity and azimuth of the light after BS, i.e. linearly polarized light was ensured. 

Now, we had to recheck if our LC's fast axis was in the required position. (The misalignments could have risen from various factors especially, months of non operational temperature control in tama and not using the system)

The final position of LC would be updated in upcoming elogs.