Ion–atom merged-beams measurements

The ion–atom merged-beams apparatus at Oak Ridge National Laboratory measures benchmark total charge-transfer cross sections for a variety of multicharged ions with atomic H from keV/u down to meV/u center-of-mass collision energies. The apparatus has recently been upgraded and moved to the new high voltage platform where a permanent magnet ECR ion source provides intense high-velocity ion beams. Upgrades to the merged-beams apparatus include more accurate beam profiles and a shortened merge path to increase the angular acceptance of the apparatus. An observed factor of four decrease in the angular divergence of the ion beam translates into access to lower collision energies with higher resolution. The higher velocity ion beams will enable charge transfer measurements with heavier ions, and measurements with both H and D at eV/u energies and below to directly observe the isotope effect.