A very sensitive electro-optical simultaneous ion detection system

Abstract

A fully operational, electro-optical system for simultaneous detection is discussed. This system is applied to the simultaneous detection of mass spectra, obtained by collision-activated dissociation experiments. The detector itself consists of a chevron arrangement of two channel plates, phosphor screen, fibre optics, camera objective and photodiode array. It forms part of an extensive information system, which controls the photodiode array and performs data processing as, for example, background subtraction and correction of the spectrum for spatial sensitivity variations of the detector. The detection system is characterized by a very low noise rate with an average value of about one dark ion per 250 s for each mass peak in the spectrum. The dynamic range of peak heights in a simultaneously detected spectrum can be up to 3.3 × 10 4 at a signal to noise ratio of 1. The reproducibility of peak area measurements is better than 20% over the entire length of the detector. In this paper several characteristics of the detection system and the data processing will be discussed. Attention will be given to variations of the spatial sensitivity and to loss of spatial resolution, both of which may occur in this type of system.