Michigan State University

Meridian Instruments, Inc.

Lawrence W Janow

John F Holland

Christie G Enke

Michael R Davenport

An integrating transient recorder for time array detection of ions within an ion source extraction. The arrival times of all ions having various mass-to-charge ratios are calculated and integrating or peak detecting circuitry is activated just prior to the calculated time of arrival of each ion, and then only for a time duration in accordance with a predetermined data collection time window sufficient to enable each ion mass value to be completely measured. An analog-to-digital converter converts the area or peak analog signal for each ion into a corresponding digital signal and outputs the digital signals to a plurality of FIFO buffers. The FIFO buffers are read out for each successive transient by a digital signal processor and summed over a predetermined number of sequential transients in a mass locked registry creating a file of ion intensities versus mass-to-charge ratio of all ions detected. In a preferred embodiment the apparatus includes a mass defect detector which compares the actual arrival time of the ions with the calculated anticipated time of arrival and applies appropriate time delays from a selected one of a plurality of delta-mass tables. This causes the area or peak detection circuity to be turned on either slightly prior to or subsequent to the calculated times of arrival of each of the ions to thus cause each of the ions to be received clearly and completely within each data collection window. Preferred embodiments include combinations of analog or digital peak or area capture and analog or digital successive summations.

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Seattle, WA, United States of America

Lawrence W Janow