Multi channel plate detector

Figure 30.13 Schematic view of the set-up for the LD-REMPI-TOFMS experiments. MCP Multi channel plate detector. The inset (top of the figure) shows the internal parts of the system and the interaction with the two laser beams.

Fig. 1.35 Multi-channel plate multiplier. Each hole corresponds to a single channel detector.

Complete MCP s can be stacked to provide even higher gains. For response in the vacuum ultra-violet spectral region (50-200 nm) a SSANACON, self-scanned anode array with microchannel plate electron multiplier, has been used (36). This involves photoelectron multiplication through two MOP S, collection of the electrons directly on aluminum anodes and readout with standard diode array circuitry. In cases where analyte concentrations are well above conventional detection limits, multi-element analysis with multi-channel detectors by atomic emission has been demonstrated to be quite feasible (37). Spectral source profiling has also been done with photodiode arrays (27.29.31). In molecular spectrometry, imaging type detectors have been used in spectrophotometry, spectrofluometry and chemiluminescence (23.24.26.33). These detectors are often employed to monitor the output from an HPLC or GC (13.38.39.40). 

Automatically takes care of shot-to-shot fluctuations in energy therefore fewer shots are needed for averaged data. Also the data are much more readily interpreted. Lower light sensitivity (can be enhanced with the use of multi-channel in-tensifier plates. With the intensifier plate in front of the detector near photoncounting capability may be achieved.) Somewhat more difficult than PMTs or PDs to use due to increased complexity and extra necessary hardware Near photon-counting capability Very easy to use and align Comparatively lower cost Large quantities of accumulated data are needed in order to obtain comparable information of an OMCD. Also data are not as readily interpreted. 

There has been renewed interest in the method, mainly due to the availability of improved Nd YAG laser systems. In addition, different types of detectors, such as microchannel plates coupled to photodiodes and CCDs, in combination with multi-channel analyzers make it possible for an analytical line and an internal standard line to be recorded simultaneously, by which the analytical precision can be considerably improved. By optimizing the ablation conditions and the spectral observation, detection limits obtained using the laser plume as a source for atomic emission spectrometry are in the 50-100 pg/g range and RSDs are in the region of 1% as shown by the determination of Si and Mg in low-alloyed steels [255, 259]. This necessitates the use of slightly reduced pressure, so that the atom vapor cloud is no longer optically very dense and the background emission intensities become lower. In the case of laser ablation of brass samples at normal pressure and direct... 

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