(A) Agilent tuning mix ion current measured as a function of distance from the entrance to the TW SLIM module at a TW speed of 124 m/s, TW amplitude of 30 V, guard bias of 5 V, RF amplitude of 220 Vpp at 650 kHz, and 2.75 mm gap at 4.00 Torr. Error bars represent standard deviations from triplicate measurements. (B) Total ion current (TIC) was measured over 8 h, and the mass spectrum was obtained by being averaged from 0 to 8 h with the above identical conditions.