TRANSPORT ANALYSIS OF RF DRIFT-VELOCITY FILTER EMPLOYING CROSSED DC-ELECTRIC-FIELD AND AC-ELECTRIC-FIELD FOR ION SWARM EXPERIMENTS

The operational characteristics of the RF drift-velocity filter develo ped recently by us to separate a mixture of gaseous ions are examined theoretically. The solutions of the appropriate transport equations pr ovide an analytical formula for the transmission efficiency of the fil ter in terms of the mobility and diffusion coefficient of the ions, th e electric field strength, the RF frequency and the filter dimension. Using the experimental transport data for Li+/Xe and Cs+/Xe, the formu la was tested and we find that it adequately accounts for the degree o f ion separation achieved by the filter at high gas pressures. The var iation of the profiles of the arrival time spectra for Li+, Na+ and Cs + ions in CO2, obtained by our drift-tube experiments, also supports t his analysis.