On-Line Computer Assisted Mass Spectrometry for Geological Research

抄録

Three magnetic sector mass spectrometers have been interfaced with an Interdata Model4computer, which services them on a time sharing basis. Each mass spectrometer is equipped with a digital display at its console. This can be updated by the computer as required by the program instructions, with data selected by the setting of a console selector switch. The system can be operated in various modes. In the simplest mode, the ion current amplitudes are read into the computer at regular intervals, and are returned to the console display after digital filtering. Another mode provides for the storage of filtered data on digital magnetic tape, together with necessary information about scan rate and direction, and amplifier sensitivity. The tape represents a full description of the analysis, which can be processed later on the same or a larger computer. The third mode, as yet only tested for strontium isotope analysis, provides for real time processing of the spectrum. The computed isotope ratios are displayed at the console as the spectrum is scanned, so that the operator can observe the convergence of their averages. If he wishes, he can also observe the present estimates of the standard deviations of the average ratios. The three mass spectrometers may be operated simultaneously in different modes. In addition to data handling functions, the computer may be programmed to control the operating conditions during the analysis. To date, only the scan rate has been controlled in this way. The present paper presents a general description of the system and of its operation.