ION TRAJECTORY CALCULATIONS FOR A QUADRUPOLE-ION-TRAP REFLECTRON-TIME-OF-FLIGHT HYBRID INSTRUMENT - EFFECTS OF THE INITIAL RF-PHASE AND THETRAPPING TIME ON AN ION BUNCH PRODUCED FROM A MOLECULAR-BEAM

SIMION calculations are compared with experimental observations of ion bunch parameters such as average kinetic energy, time-of-flight, and mass resolution as a function of the storage time and the initial phas e in the quadrupole ion trap of a trap-reflectron hybrid instrument (T RAPTOF). It is shown that the proper choice of pr frequency and inital phase results in favourable experimental conditions even without the use of a buffer gas inside the trap, Synchronization of all events in the instrument relative to the RF trapping field is the most important prerequisite.