Emittance measurement of multi-species ion beam produced via two-step charge exchange process in a Li vapor cell

A Li vapor cell has successfully converted a He+ ion beam to a He- ion beam by double charge exchange reaction. Emittance of the He+ ion beam and that of the He- beam were independently measured to study emittance growth during the passage of the charge exchange cell. Each component was seperated by electrostatic deflection after passing through a beam shaping slit. The result had shown that the emittance of the He+ ion beam was not changed by the passage of the charge exchange cell, while the emittance of the He- ion beam had increased even with the presence of focusing electric field produced by He+ ions. The emittance of the He- ion beam had increased up to twice as large as that of the incident He+ beam. The normalized emittance of the He- at the beam energy of 10-20 keV, which is an optimum energy range for charge exchange efficiency, was estimated to be 0.07-0.09 mm-mrad. (author)