The ionization fraction of helium is determined by the temperature and density of the plasma. At a particular density and temperature , some fraction of helium will be neutral , some fraction will be singly ionized , and some fraction will be doubly ionized . At the same time, the number of electrons per helium nucleus is determined by charge neutrality. You can set with in cgs units ( to see the ionization fraction as temperature varies from 40,000 K to 200,000 K.