Reflective Echelle Spectrograph (RES) for MAST
A
RES is a high dispersion spectrograph to measure the velocity and magnetic fields
(in combination with the proposed polarimeter) in two different spectral lines
which have different formation heights in the solar atmosphere i.e. in
the photosphere and chromosphere respectively. RES will be installed at the
back end of the proposed 50 cm aperture Multi Application Solar Telescope (MAST)
at the lake site of the Udaipur Solar Observatory.
The main goal of the RES is to study the dynamics of small scale features on the
sun for which one needs to measure the velocity flows of the order of
0.5 km/s and small-scale magnetic flux in the photosphere and the chromosphere.
This requires that a large wavelength range be covered for spectroscopy
and high dispersion be achieved. We propose to develop an all-reflective
Echelle spectrograph in a Littrow configuration for simultaneous measurements
in the photosphere and chromosphere. The spectral range of the RES will be
chosen such that it covers a pair of photosphere/chromosphere spectral lines,
for example 6173/8542 A pair is being considered, to yield a high linear
dispersion. This pair of lines is also magnetically sensitive. Thus, the
RES will be used in combination with the polarimeter to simultaneous measure
the small scale magnetic fields in the photosphere and the chromospheric heights.