GB795663A - Electron multiplier - Google Patents

Abstract

795,663. Electron multipliers; mass spectro meters. BENDIX AVIATION CORPORATION. Aug. 5, 1954 [Aug. 10, 1953], No. 22820/54. Class 39(1). An electron multiplier arrangement, which may be used with a time-of-flight mass spectrometer, comprises a series of staggered secondarily emissive plates 16-24, Fig. 1, or 70-86, Fig. 3, a pair of collector electrodes 26, 32, Fig. 1, or 78, 88, Fig. 3, and a grid control electrode 28, Fig. 1, or 80, Fig. 3, so arranged in the path of the secondary electrons recoverable by one of the collector electrodes 26, Fig. 1, or 78, Fig. 3, from its directly associated plate 24, Fig. 1, or 76, Fig. 3, that for one voltage level applied to the control electrode the electrons are allowed to traverse the latter to be collected by the collector electrode 26, Fig. 1, or 78, Fig. 3, so that the flow of electrons through the multiplier is arrested, while for another voltage level applied to the control electrode the latter is not traversed by the electrons which continue their path through the multiplier to the other collector electrode 32, Fig. 1, or 88, Fig. 3. Pole-pieces 56 cause the electrons to follow cycloidal paths between the plates. In the arrangement shown in Fig. 1, the control electrode 28 is normally biassed to a potential preventing electrons passing through it towards the collector electrode 26 to which a cathode oscilloscope 27 is connected. In the arrangement shown in Fig. 3, the control electrode 80 is normally biassed to a potential allowing electrons to pass through it towards the collector electrode 78, a cathode oscilloscope 89 being connected to the other collector electrode 88. The multiplier can be used with a source of ions or time-of-flight mass spectrometer 10 similar to that described in Specification 742,687, the control electrode 28 or 80 being supplied with voltage pulses so timed that the oscilloscope 27 or 89 will indicate only the ion groups of a pre-determined mass number. Specification 727,683 also is referred to.