FIRST OBSERVATIONS WITH A NEW IMAGING POLARIMETER

We present first observations of solar polarization with a new imaging polarimetry system that simultaneously records three Stokes component s, I, Q, V or I, U, V, in a single CCD. This instrument is an intermed iate version on the way to ZIMPOL II (Zurich Imaging Stokes Polarimete r II), which will record all four Stokes parameters (Stenflo et al. 19 92). The principle of operation is based on a piezoelastic polarizatio n modulator in combination with a special CCD sensor equipped with a m icrolens array and a mask. This sensor is used as a synchronous demodu lator. The theoretical performance of the instrument is discussed. Lab oratory tests as well as initial solar observations at two different s olar telescopes are presented and analysed to experimentally evaluate the performance. The polarimetric accuracy is better than 10(-4), a no ise level of 2 x 10(-5) has been achieved; the polarimetric efficiency is in agreement with theory.