Zurich Imaging Stokes polarimeters I and II


We present the design of the Zurich Imaging Stokes Polarimeters (ZIMPOL) I and II along with the first measurements and scientific observations. ZIMPOL I which was developed for precision solar vector polarimetry, uses two piezoelastic modulators and CCD arrays that have every other row covered with an opaque mask. During exposure the charges are shifted back and forth between covered and light-sensitive rows in synchrony with the modulation. In this way Stokes I and one of Q, U, or V can be recorded. Since the charge shifting is performed at frequencies well above the seeing frequencies and both polarization states are measured with the same pixel, highly sensitive and accurate polarization and information can be recorded. ZIMPOL II will record simultaneous images of all four Stokes parameters with a single CCD detector chip. A micro-lens array collects all of the photons and directs them to the unmasked pixel rows. This provides three storage rows for each set of four rows. The efficiency for simultaneous recording of all four Stokes parameters is six times that of ZIMPOL I.