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Paper: The New Solar Telescope in Big Bear: Polarimetry II
Volume: 437, Solar Polarization Workshop 6
Page: 345
Authors: Cao, W.; Ahn, K.; Goode, P. R.; Shumko, S.; Gorceix, N.; Coulter, R.
Abstract: IRIM (Infrared Imaging Magnetograph) is one of the first imaging solar spectro-polarimeters working in the near infrared (NIR). IRIM is being installed and commissioned in the Coudé Lab of the 1.6-meter New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO). This innovative system, which includes a 2.5 nm interference filter, a unique 0.25 nm birefringent Lyot filter, and a Fabry-Pérot etalon, is capable of providing a bandpass as low as 0.01 nm over a field-of-view of 50″ in a telecentric configuration. An NIR waveplate rotates ahead of M3 in the NST as the polarimeter modulator, and ahead of it locates a calibration unit to reduce polarization cross-talk induced by subsequent oblique mirrors. Dual-beam differential polarimetry is employed to minimize seeing-induced spurious polarization. Based on the unique advantages in IR window, the very capable NST with adaptive optics, IRIM will provide unprecedented solar spectro-polarimetry with high Zeeman sensitivity (10–3Ic), high spatial resolution (0.2″), and high cadence (15 s). In this paper, we discuss the design, fabrication, and calibration of IRIM, as well as the results of the first light observations.
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