IRIM - An imaging magnetograph for high-resolution solar observations in the near-infrared

The InfraRed Imaging Magnetograph (IRIM) is an innovative magnetograph system for near-infrared (NIR) observations of the Sun. IRIM will provide high spatial resolution (0.2″ pixel^-1 image scale), high temporal resolution (1-2 minutes), moderate spectral resolution (14.0 pm), and high magnetic sensitivity covering a substantial field-of-view (FOV: 170″ circular). The bandpass of the instrument is reduced in three steps while still providing high transmission: (1) a 4 nm interference filter, (2) a 0.25 nm Lyott-filter, and (3) a 14.0 pm tunable Fabry-Pérot etalon. The innovative NIR Lyot-filter was developed at the New Jersey Institute of Technology (NJIT) and is currently being assembled at Cambridge Research Instruments. It is the first of its kind and provides a large angle of acceptance, thus solving many problems encountered with dual Fabry-Pérot systems. The two-dimensional line profiles will be recorded by a 1024 × 1024 pixel, 14-bit Complex Metal Oxide Semiconductor (CMOS) focal plane array (FPA) manufactured by Rockwell Scientific Imaging, which can obtain images at a rate of 50 frames s^-1. IRIM will utilize the remodelled Coudé-feed of the 65 cm vacuum telescope at the Big Bear Solar Observatory (BBSO) and will benefit from an image stabilization and correction system of independently operating Correlation Tracking (CT) and Adaptive Optics (AO) systems.