CC-Pol — The Canaricam Polarimetry Module

We present details of CC-Pol — the CanariCam Polarimetry Module. CC-Pol will offer diffraction limited imaging polarimetry in the N window. The feasibility of offering imaging polarimetry in the Q window and spectropolarimetry over the range from 8 to 25 μm are currently being studied. CC-Pol will incorporate a system of rotating half wave plates optimised to each spectral window and a Wollaston prism to present a dual beam image. Dual beam polarimeters offer the maximum accuracy and throughput and allow good science data to be taken even in non-photometric conditions. CC-Pol will be one of the very few mid-infrared polarimeters available on the new generation of large telescopes. We describe its design, capabilities, calibration and operation and discuss some of the fields in which we expect the instrument to make a decisive contribution to new and exciting science with the GTC. In particular, we show that the diffraction limited capability is of enormous importance for extended sources such as AGNs, where a polarised point source is diluted by a non-polarised extended emission.