The 8–10 μm Wide-band Imaging System for AIMS

Abstract

We present the design, implementation, and performance validation of the 8-10 μm Wide-band Imaging System developed for the Accurate Infrared Magnetic Field Measurements of the Sun (AIMS) telescope. This system addresses the significant challenges in solar mid-infrared observations, including weak signal levels, intense environmental thermal background, and high detector noise. The system employs a cryogenic optical design with ZnS/ZnSe transmissive re-imaging configuration, a Chinese-made 256×256 HgCdTe infrared focal plane array operating at ≤80 K, and comprehensive stray light suppression measures including cold stops and vacuum encapsulation. Key performance parameters include a field of view of Φ384″ (6.4′), spatial resolution of 3″ (diffraction-limited), temporal resolution of 20 ms, and operation at two filter bands centered at 8.5 μm and 9.0 μm (FWHM 0.5 μm). Laboratory tests demonstrate the system achieves diffraction-limited imaging quality with RMS spot size smaller than the Airy disk diameter across the entire field of view. The system reliably achieves data acquisition rates of 80 frames per second for 256×256 images, exceeding the design requirement of 50 fps. Preliminary on-sky observations at the Lenghu site successfully captured solar active regions and flare events, confirming the system's capability for studying rapid evolutionary processes in the solar atmosphere. This instrument represents the first dedicated regular observational facility for the 8-10 μm band internationally, filling a critical gap in solar mid-infrared astronomy.