  The lithium chloride aqueous solution has great potential to be the detection
medium of a novel solar neutrino detector. The nuclide \ce{^7 Li} provides a
charged-current interaction channel with a high cross-section for the MeV-scale
solar electron-neutrinos, enabling measurement of the solar neutrino spectrum.
This work measures the optical properties and the light yields of a saturated
lithium chloride solution. After adsorption with activated carbon and
recrystallization, the solution shows little absorption in the sensitive
wavelength range of the bialkali photomultipliers. The attenuation length is
evaluated to reach 50 meters at 430 nm. In addition to being a pure Cherenkov
detector medium, a wavelength shifter, carbostyril 124, is added to the LiCl
aqueous solution. The compatibility and the enhancement of the light yield are
confirmed, enabling the development of a water-based Cherenkov-enhanced
lithium-rich detector.
