The Imaging Magnetograph Experiment (IMaX)

IMaX is an imaging vector magnetograph observing Doppler shifts and polarization in the Zeeman-sensitive photospheric spectral line of neutral iron at 525.02 nm. Images are taken in up to twelve wavelength bands. The instrument provides fast cadence, high-spatial resolution, two-dimensional maps of the magnetic vector, the line-of-sight velocity and continuum intensity. It has a field-of-view of 50×50 arcsec2, which is the largest of all instruments on SUNRISE . A tunable LiNbO3 solid-state Fabry-Perot etalon is used in double pass, thus minimizing mass and power consumption and relaxing the requirements on passband stability. Since the free spectral range of such a system is quite small, a narrowband interference filter (FWHM 0.1 nm) is used in addition. Both prefilter and etalon are thermally stabilized. Imaging is done with two synchronized 1k×1k CCD cameras in orthogonal polarization states. Two nematic liquid crystal retarders modulate the incoming polarization. Four switching states are needed for full Stokes vector polarimetry,while two-states are sufficient for longitudinal magnetometry (circular polarization).

The IMaX instrument
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