The area of high precision solar spectropolarimetry has made great advances in recent years and the Zurich
IMaging POLarimeter (ZIMPOL) systems have played a major role in that. ZIMPOL reaches a polarimetric
accuracy of 10-5 by using fast (kHz) polarization modulation/demodulation of the light beam in combination
with large-area array detectors. A new generation of improved cameras (ZIMPOL-3) are being implemented for
the scientific observations at the solar observatory at Istituto Ricerche Solari Locarno. The new system is based
on a flexible and compact modular design, which easily adapts to new applications. A faster electronics and new
sensors with higher quantum efficency compared to the previous ZIMPOL versions, allow to achieve a better
overall efficency. Future plans include observing campaigns at foremost large telescopes and the exploration of
new technologies (e.g. CMOS).
The 4-m aperture Advanced Technology Solar Telescope (ATST) is the next generation ground based solar telescope. In this paper we provide an overview of the ATST post-focus instrumentation. The majority of ATST instrumentation is located in an instrument Coude lab facility, where a rotating platform provides image de-rotation. A high order adaptive optics system delivers a corrected beam to the Coude lab facility. Alternatively, instruments can be mounted at Nasmyth or a small Gregorian area. For example, instruments for observing the faint corona preferably will be mounted at Nasmyth focus where maximum throughput is achieved. In addition, the Nasmyth focus has minimum telescope polarization and minimum stray light. We describe the set of first generation instruments, which include a Visible-Light Broadband Imager (VLBI), Visible and Near-Infrared (NIR) Spectropolarimeters, Visible and NIR Tunable Filters, a Thermal-Infrared Polarimeter & Spectrometer and a UV-Polarimeter. We also discuss unique and efficient approaches to the ATST instrumentation, which builds on the use of common components such as detector systems, polarimetry packages and various opto-mechanical components.
We present results from a phase A study supported by ESO for a VLT instrument for the search and investigation of extrasolar planets.
The envisaged CHEOPS (CHaracterizing Extrasolar planets by Opto-infrared Polarization and Spectroscopy) instrument consists of an extreme AO system, a spectroscopic integral field unit and an imaging polarimeter. This paper describes the conceptual design of the imaging polarimeter which is based on the ZIMPOL (Zurich IMaging POLarimeter) technique using a fast polarization modulator combined with a demodulating CCD camera. ZIMPOL is capable of detecting polarization signals on the order of p=0.001% as demonstrated in solar applications. We discuss the planned implementation of ZIMPOL within the CHEOPS instrument, in particular the design of the polarization modulator. Further we describe strategies to minimize the instrumental effects and to enhance the overall measuring efficiency in order to achieve the very demanding science goals.
With a new class of imaging polarimeters it is now possible to
eliminate the previous main limiting factors of seeing and gain-table noise in the polarization images to allow spectro-polarimetry with a precision of 5 × 10-6. This has opened the door to a previously unexplored world of polarization phenomena with promising diagnostic possibilities not only for the Sun but also for night-time astronomy. While illustrating examples of what has been achieved,
we present an overview of the new opportunities and quantify the limitations imposed by the photon flux.
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.