Tests of the demodulating CCDs for the SPHERE / ZIMPOL imaging polarimeter

摘要

The imaging polarimeter ZIMPOL is one of three focal plane instruments of the SPHERE / VLT planet finder. ZIMPOLmeasures the linear polarization based on a fast modulation – demodulation principle using a charge-shifting techniqueon a masked CCD for separating the photons with opposite polarization direction. This paper describes the on-chipdemodulation and the different detector read-out modes which are implemented for the ZIMPOL polarimeter. Testresults are presented which allow an evaluation of the performance of the ZIMPOL CCD detectors. The achievablepolarization efficiency is close to expectation and the charge trap correction with the two-phase demodulation modeworks well. Other detector effects like bias level variations and read-out patterns can be corrected in the data reductionprocess. The tests demonstrate that the demodulating CCDs fulfill the requirements for the SPHERE project.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.