| 摘要 |
1,173,137. Mass spectrometers. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 10 May, 1967 [17 May, 1966], No. 21826/66. Heading H1D. In a mass spectrometer the total effective exposure of a photographic plate or other integrating ion-detector is synthesized from two or more successive individual exposures, the succession of individual exposures being terminated automatically at a predetermined number or when the charge laid down on the detector reaches a predetermined value, the individual exposures preferably being of equal duration in time. The charge is monitored on a collector having a slit through which about half of the ions will pass when the beam is in focus in front of the photographic plate, the collector being connected to a capacitor storage circuit which automatically terminates the succession of exposures. This is effected by control of a relay for disconnecting a pulse amplifier controlling the operation of an ion beam chopper which, as shown, comprises a deflector slit 2 defined by the parallel flanges 4, 6 of two halfplates 8, 10. Half-plate 10 and further upstream and downstream plates 16 and 22 are earthed while a deflecting potential is applied to the half-plate 8 to allow the ion beam periodically to pass through the system. Halfplate 8 may be periodically varied between zero and a positive potential to repeatedly switch the beam into the slit 2 or made alternately positive and negative to repeatedly sweep the beam across the slit 2, preferably at a constant rate. The ion source of the spectrometer is of the spark type preferably of the type disclosed in Specification 21825/66. The ion beam chopper assembly shown is preferably located immediately after the ion source and before the electrostatic analyser. |
