Compensate for undesirable flight time dispersion of ions

A method for filling a filling volume with ions of different mass and the same energy from a remote storage device, characterized in that the ions are taken from the storage reservoir at the same time or in the order of lighter to heavier ions, whereupon the light ions requires the heavier ions with the same energy fly that subsequently the flight order of ions of different masses by a mass-proportional acceleration is reversed and that the ions are caused by a mass-proportional braking back to their original, and substantially all ion same kinetic energy after the reversal of the flight sequence, and substantially simultaneously in the Filling volume occur.