Cooling negative-ion beams

Studies have been conducted to determine the feasibility of using the collisional cooling technique as a means of reducing energy spreads and emittances of sputter-generated negative-ion beams. A gas-filled rf-quadrupole ion cooler, equipped with provisions for decelerating ion beams to sufficiently low energies prior to cooling and reaccelerating them to high energies following the cooling process, has been designed and used to cool O− and F− ion beams with initial energy spreads, ΔE>10 eV to final energy spreads, ΔE∼2 eV full width half-maximum. Overall transmission efficiencies of ∼14% for F− beams have been obtained. Experimental results show that electron detachment is the major loss mechanism for negative ions.