The EMIS PARSIFAL was designed to purify very small quantities of radioactive isotopes. Yields are therefore an important component of the separations. The ionization is done in a thermoionization source or a plasma source, according to the physical properties of the concerned elements. For rare earth elements (REE), hydroxides are electrodeposited on a tantalum wire; for thermoionization, the wire is introduced in a tungsten crucible whose depth is linked to the boiling point of the element. Samples weigh between 0.2 and 0.9 mg. The crucible, heated at 3050°C by electron bombardment, gives REE yields from 20 to 40% and usually 50% for europium. The total beam intensity is about 5 × 10 -6 A and separations last from 2 to 20 hours until the whole sample is consumed.