Segmented charge detectors

L. Ebdon, M. Foulkes and K. O Hanlon, Optimised simultaneous multielement analysis of environmental slurry samples by inductively coupled plasma atomic emission spectrometry using a segmented array charge-coupled device detector. Anal. Chim. Acta, 311, 1995, 123-134. 

S. Euan, H. Pang and R. S. Houk, Application of generalized standard additions method to inductively coupled plasma atomic emission spectroscopy with an echelle spectrometer and segmented-array charge-coupled detectors, Spectrochim. Acta, Part B, 50(8), 1995, 791-801. 

Mermet, J.M. and Ivaldi, J.C. (1993) Real time internal standardisation for ICP-AES using custom segmented array charge coupled device detector, Journal of Analytical Atomic Spectrometry, 8, pp795-801. 

The primary drawback to air-segmented systems is the bubble. These air bubbles are compressible, thereby creating pulsations in the flowing stream. In addition, for most detectors, the air bubble must be removed before the sample passes through the detection cell. In addition, the precision of bubble size has been difficult to control. This variation in bubble size adds to the irreproducibility of the system. If electrochemical or other static sensitive detectors are used, the segmented system, which builds up static charge, will present severe problems... 

For a pre-set number of consecutive pulses, the shutter will always open at the same time tj after triggering and for the same duration tg to allow a small slice (denoted by the hatched area under the decay curve in Hgure 5) of the detector s output signal to enter the recorder. There it is used to charge a capacitor, whose charge increases with each repetition of the pulse. If enough pulses are sampled in this way, random noise in the measured decay segment... 

After the APCI or ESI processes have been run, the analyte is focused by means of octapoles and lenses and fed into the mass filter, such as, for example, an ion trap. In this segment, the solvent has been completely separated, leaving the ions isolated in the ion trap. After separation on the basis of their mass to charge ratio, the ions are accelerated to the detector (electron multiplier). Figure 4.3 provides a schematic representation of a mass spectrometer with ESI sprayhead and ion trap and liquid chromatography apparatus. 

Other requirements of a general nature are that any particle identification system must not compromise either charged particle or photon resolution, that detector elements must be radiation hard to a level not previously encountered in e e detectors, and that detector elements and data acquisition systems must cope with unprecedentedly high rates. A valuable improvement in overall efficiency can be obtained by finely segmenting the magnet flux return to allow the identification of low momentum muons. 

---