Abstract Details

Name: Shrish Shrish
Affiliation: National Institute of Science Education and Research
Conference ID: ASI2020_515
Title : Modeling geometrical and intensity distortions for WALOP polarimeter.
Authors and Co-Authors : Shrish
Abstract Type : Poster
Abstract Category : Instrumentation and Techniques
Abstract : Cold dust grains align such that the shorter axis is along the direction of galactic magnetic field. This causes polarized (along a longer axis) emission (black body) also in the range of cosmic microwave background (CMB), eventually contaminating primordial CMB B-mode polarization data. We need to know the galactic magnetic field for modeling decorrelations of dust emission for a different frequency. Starlights are intrinsically unpolarized but when transmitted through dust clouds, get selectively polarized along a shorter axis of grains (directly leading us to direction of magnetic field). The under-construction WALOP polarimeter of the PASIPHAE project is an ambitious step toward getting polarization mapping of the sky. We plan to measure star light polarization in the optical region. Every optical instrument is anisotropic to some extent that introduces further polarization. The measurement of polarization has evolved into a separate challenge, as we are dealing with a very low degree of polarization (≤ 0.2%). I am working on methods for accounting for the instrumental polarization and correcting starlight polarization. A major part of my work involves high precision photometry on wide-field CCD. I am required to model PSFs with CCD coordinates to facilitate photometry with an accuracy of less than 0.1%. My work also addresses modeling and correcting spatial distortion introduced by WALOP. For now, I am working on data from ZEMAX simulation of WALOP(due to Siddharth Maharana) and in a near future will be working on data from assembled WALOP.