Improvements in or relating to mass spectrometers

965,020. Mass spectrometers. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. May 20, 1963 [May 29, 1962], No. 20582/62. Heading H1D. A device for the simultaneous measurement of the intensities of two ion beams 4, 5, separated in a mass spectrometer consists of two target electrodes, only one of which 1 is shown, positioned on either side of a partition 3 and behind beam entry slits 16, 17, the ion beams being accelerated on to the target electrodes to release secondary electrons and a magnet 35 being provided to deflect the secondary electrons in opposite directions to fall on phosphor windows 10, 11, which are backed by photomultipliers 12, 13. The phosphor windows are surrounded by soft iron tubular shields 31, 32 and the photomultipliers are provided with magnetic shielding 18. Silicone oil is provided between the phosphor windows and the multipliers and a thin aluminium layer is deposited on each of the phosphor windows. The covers 19, 37 for the target electrode leads are filled with oil. Pumping holes 28 are provided in the wall 6 containing the beam entry slits 16, 17.