An efficient ion funnel operating at 100 mbar background pressure

摘要

The results obtained for the 100 hPa ion funnel (300 V_(pp) at 10 MHz, 50 % ion transmission, m/z = 100) can be scaled to other pressures and electrode distances. The following assumptions are made: The flow velocity is constant. The frequency increases linearly with pressure keeping the damping of the electrostatic field by diffusion constant. The breakdown voltages are calculated using the equations of Burm [2]. Comparing the breakdown voltage and the required voltage amplitude shows that the constructed 100 mbar ion funnel with 0.25 mm electrode distance is operating close to the breakdown limit. If the electrode distance can be reduced to approximately 25 μm, e.g. using a planar ion funnel [3] even an operation at atmospheric pressure becomes possible (cf. Fig. 7). However, the estimated driving power is in the order of 1 kW.