A coronal mass ejection and magnetic cloud containing an unusually large en
hancement of He+ was observed in the solar wind by the plasma and magnetic
field instruments on the Advanced Composition Explorer (ACE) spacecraft on
May 2-4, 1998. The He+/He++ ratio during this event exceeded 0.5% for a per
iod of more than 24 hours, and reached values as high as 100%. The high He/He++ ratio indicates the presence of prominence material, and in fact a di
sappearing filament and prominence were observed at the Sun in association
with this event. The prolonged observation of He+ indicates that prominence
material extended through much of this CME, the first such observation in
a CME in the solar wind.