NIMPOL: an imaging polarimeter for the mid-infrared

Abstract

We have built an imaging polarimeter for use at mid-infrared wavelengths, i.e. N band or 8 - 13 micron. The detecting element is a 128 x 128 element Si: Ga Focal Plane Array, supplied by Amber Engineering, USA. The polarimeter itself provides diffraction limited images on a 4-m class telescope and has a field of view of about 32 arcsec of sky with 0.25 arcsec pixels. We describe the optical design, control electronics, observing modes and detector sensitivities. Also presented are some observational results to demonstrate the power of this new imaging polarimetric system.