NIM --- A Near Infrared Magnetograph

Details NIM --- A Near Infrared Magnetograph NIM --- A Near Infrared Magnetograph

Dec 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...181.8101r&link_type=abstract

American Astronomical Society, 181st AAS Meeting, #81.01; Bulletin of the American Astronomical Society, Vol. 24, p.1251

Physics

Optics

Scientific paper

\newcommand{\micron}{microns} \newcommand{\kayser}{cm(-1) } \newcommand{\NIM}{NIM} We describe a new instrument for mapping magnetic field strength in the active solar photosphere. \NIM\ is a Stokes spectropolarimeter that exploits the high Zeeman sensitivity of the line Fe I 6388.64 \kayser\ (15648.5 Angstroms, e\:(7D_1) -- 3d(6) 4s 5p\:(7D^) o_1, Lande g = 3.00, chi_e = 5.36 eV) to measure vec {B}. For |B| ga 850 G, the magnitude of the field is derived, without adjustable parameters, from the complete splitting of the Zeeman components. The relative strengths of the Stokes components indicate the direction of the field. The absolute strength of the polarized signal depends on the areal filling factor, inclination, continuum contrast, and line strength of the magnetic flux tubes within the angular resolution element. \NIM\ comprises the following subsystems: precision image scanner liquid crystal polarization modulators and control electronics slit spectrograph transfer and minification optics 128 times 128 InSb infrared array camera computer for data acquisition and user interface \NIM\ builds up a two-dimensional array of polarized spectra by scanning the solar image across the spectrograph slit. The spatial and spectral sampling frequencies are 1.0 arcsec or 0.5 arcsec per pixel (depending on which telescope is used) and 0.025 \kayser\ per pixel. At each slit position, 8 polarization pairs for each Stokes parameter (e.g., +/- V) are acquired at 7 Hz, averaged, and recorded in FITS format. A 128 times 128 arcsec(2) map is acquired in about 20 minutes. \NIM\ is available to NSO visiting observers at the McMath-Pierce Telescope on Kitt Peak.

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