After passing analysing magnet, carbon ions of different mass move along different trajectories. In the drift tube, 13C+ and 12C+ ions are collected and their electric currents are measured. The 14C+ ions freely pass into electrostatic analyser.
At the trajectories of 12C+ and 13C+ ions, Faraday cups are placed, whch collect and measure electric charge brought by the ions. As the beams project in short pulses (see “beam sequencer “), electric current for each pulse is determined separately. Typical currents in the pulses are 30 microamps and 300 nanoamps for 12C and 13C, respectively.