  The relative abundance of deuterium (D) in the solar atmosphere is not known.
D is not only destroyed in stars, it is also synthesized in the atmospheres of
active stars (Prodanovic & Fields 2003). In several cases, production of D in
the sun has been detected when solar flares occur, using both energetic
particle measurements (Anglin 1975) and by detection of 2.223 MeV gamma rays
emitted by D (Terekhov et al. 1996; Shih et al. 2009). We describe a project to
measure the abundance of deuterium in the solar wind, and to monitor its
evolution during a several-year period. The instrument consists of two grids, a
tritium target, and semiconductor particle detectors. The grids, which are
hemispherical and concentric, accelerate the incident solar wind ions using a
potential difference on the order of ~80 to 100 kV and concentrate the ions on
the tritium target. A fraction of the solar wind deuterons thus accelerated
interact with the target to produce 3.6 MeV alpha particles, some of which are
recorded by adjacent semiconductor detectors. A similar instrument was
successfully tested in space in 1975 in order to observe positive auroral ions
in a hydrogen aurora.
