  A sounding-rocket program called the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP) is proposed to be launched in the summer of 2014.
CLASP will observe the solar chromosphere in Ly-alpha (121.567 nm), aiming to
detect the linear polarization signal produced by scattering processes and the
Hanle effect for the first time. The polarimeter of CLASP consists of a
rotating half-waveplate, a beam splitter, and a polarization analyzer.
Magnesium Fluoride (MgF2) is used for these optical components, because MgF2
exhibits birefringent property and high transparency at ultraviolet wavelength.
