GB767527A - Improvements in or relating to mass spectrometer and electron multiplier arrangements - Google Patents

Abstract

767,527. Electron multipliers: mass spectrometers. BENDIX AVIATION CORPORATION. May 17, 1954 [June 4, 1953], No. 14435/54. Class 39(1). A time-of-flight mass spectrometer incorporates an electron multiplier 106 arranged to receive on its first secondarily emissive plate 104 ion bunches produced by the mass spectrometer 96 and to provide an indication of the times of reception of the various mass-groups of ions in each bunch by the amplified pulses appearing at the output oscilloscope 144 of the multiplier, the multiplier including a control electrode 116 associated with one of the other secondarily emissive plates 108 of the electron multiplier and normally biassed to such a potential relatively to the plate as to limit or prevent the flow of secondary electrons from the plate, and means 132 for supplying the control electrode 116 with positive voltage pulses at times corresponding to the reception of ions of a particular mass number on the first plate 104 of the multiplier. The electrons pursue cycloidal paths between the plates of the multiplier 106 under the combined action of the magnetic field produced by the pole pieces 40 and the electric field between the electrode 100 and the plates of the multiplier. The control electrode 116 is associated with one of the initial plates, preferably the second plate, of the multiplier, and can be in the form of a wire grid. The pulse generating device 132 is arranged to generate pulses at accurately adjustable relative instants, a first one of the pulses being applied to the mass spectrometer 96 for discharging a bunch of ions therefrom towards the first plate 104 of the multiplier, and another pulse being applied to the control electrode 116 with a delay relatively to the first pulse adjusted in accordance with the expected time of flight of the ions having a particular mass number. The construction of the spectrometer unit is substantially as described in Specification 727,683.