Collisional cooling of negative ion beams

Investigations have been conducted to determine the feasibility of using collisional cooling for reducing the energy spreads and, consequently, the emittances of negative-ion beams. We have designed a gas-filled RF-quadrupole ion cooler equipped with provisions for retarding energetic negative ion beams to energies below thresholds for electron detachment at injection and for reacceleration to high energies after the cooling process. The device has been used to cool O^- and F^- ion beams with initial energy spreads, ΔE >10 eV to final energy spreads, ΔE ~2 eV FWHM. 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