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Photoplate detector

The photoplate detector is one of the oldest types of MS detectors (Fig. 2.21a). J.J. Thompson used photoplates to record mass spectra [4], Photoplates were for a [Pg.65]


Figure 2.21. Schematic of (a) a photoplate detector (b) a Faraday cup (c) a discrete-dynode electron multiplier (EM) of Venetian blind type and (d) a continuous dynode EM. Parts (c) and (d) reprinted from A. Westman-Brinkmalm and G. Brinkmalm (2002). In Mass Spectrometry and Hyphenated Techniques in Neuropeptide Research, J. Silberring and R. Ekman (eds.) New York John Wiley Sons, 47-105. With permission of John Wiley Sons, Inc. Figure 2.21. Schematic of (a) a photoplate detector (b) a Faraday cup (c) a discrete-dynode electron multiplier (EM) of Venetian blind type and (d) a continuous dynode EM. Parts (c) and (d) reprinted from A. Westman-Brinkmalm and G. Brinkmalm (2002). In Mass Spectrometry and Hyphenated Techniques in Neuropeptide Research, J. Silberring and R. Ekman (eds.) New York John Wiley Sons, 47-105. With permission of John Wiley Sons, Inc.
Unlike the photoplate, the Faraday detector (or Faraday cup) is still very much in use today. The main reasons for its lasting popularity are accuracy, reliability, and mgged construction. The simplest form of Faraday detector is a metal (conductive) cup that collects charged particles and is electrically connected to an instrument that measures the produced current (Fig. 2.21b). Faraday cups are not particularly sensitive and the signal produced must in most applications be significantly amplified. An important application for Faraday detectors is precise measurements of ratios of stable isotopes [278]. See, for example, Section 2.2.7 and Chapter 11 for examples of applications and methods in which Faraday detectors are utilized. [Pg.67]

Focal plane detectors are used primarily to detect ions separated in space by, for example, magnetic sector analyzers (see Section 2.2.2). The objective of an ideal focal plane detector is to simultaneously record the location of every ion in the spectrum. In many ways the photoplate (see Section 2.3.1) is the original focal plane detector, but it has today been more or less replaced with designs that rely on EM detectors (see Section 2.3.3). A common arrangement is to allow the spatially disperse ion beams simultaneously to impinge on an MCP (see Section 2.3.3.2). The secondary electrons generated by the ion impacts then strike a one- or two-dimensional array of metal strips and the current from the individual electrodes is recorded. A tutorial on the fundamentals of focal plane detectors is found in Reference 283. Reference 284 provides a relatively recent review of MS detector-array technology. [Pg.69]

The microchannel plate detector can, however, also work with a metal anode that gathers the stream of secondary electrons at every channel exit. To avoid any confusion, the term array detector is preferably used to describe a microchannel plate where every microchannel remains as an individual ion-detecting element. This array detector acts as electronic photoplates. Indeed, it resembles that of a photographic plate ions with different m/z ratios reach different spots and may be counted at the same time during the analysis. The advantage of array detectors is that analyser scanning is not necessary and therefore sensitivity is improved because simultaneous detection of ions implies that more ions are collected, and this greater efficiency leads to lower limits of detection than for other detectors. [Pg.180]

Another electro-optical ion detector, which is called the electro-optical array detector, allows the simultaneous measurement of ions spatially separated along the focal plane of the mass spectrometer. It combines the microchannel plate and Daly detector. The ions are converted in a microchannel plate into electrons that are amplified. The released secondary electrons finally strike a phosphorescent screen that emits photons. These photons are then detected with a photodiode array or CCD detector. This array detector acts as electronic photoplates. [Pg.182]

Photoplates, films and photo multipliers are used as detectors. Normally, gratings are used at low orders (m < 4) and they have a small grating constant (1/3600 mm < a < 1/300 mm). The different orders can be separated by using special photomultipliers. For instance, with a solar-blind photomultiplier only radiation with a wavelength below 330 nm can be detected. This allows separation of the 1st order radiation at 400 nm from the 2nd order radiation at 200 nm. This can, for example, be applied in polychromators to double the practical resolution. [Pg.59]

MicroChannel plate detectors can also be used. When using a phosphor, the detector can be coupled with photodiode arrays or charge coupled devices, which are known from optical atomic spectrometry, and it becomes possible to detect ions of different masses simultaneously as in the case of photoplate detection. [Pg.82]

A dispersive magnetic sector mass analyzer does not use a flight tube with a hxed radius. Since all ions with the same kinetic energy but different values of m/z will follow paths with different radii, advantage can be taken of this. The ions will emerge from the magnetic held at different positions and can be detected with a position-sensitive detector such as a photoplate or an array detector. Examples of dispersive magnetic sector systems are shown in Fig. 9.16(c) and (d). [Pg.634]

Change of radius, r Not possible with a fixed detector, although special applications such as accmate isotope ratio measurements use two or more fixed detectors. This method was used historically with photoplate detection, and has been revived with mi-crochannel plate photodiode array detectors this can improve signal-to-noise ratio as all the ions of interest can be monitored simultaneously and hence continuously. [Pg.2840]

Figure 9.18 Early mass spectrometer designs, (a) Aston, 1919 (b) Dempster, 1918 (c) Mattauch-Herzog, 1935 (d) Bainbridge, 1933. In each case, B signifies the magnetic fieid. Spectrometers (c) and (d) are dispersive mass spectrometers (c) the Mattauch-Herzog design is aiso a doubie-sector instrument, using an electric sector before the magnetic field. Modern versions of these spectrometers are still in use, with the photoplate replaced by one of the modern detectors discussed subsequently. Figure 9.18 Early mass spectrometer designs, (a) Aston, 1919 (b) Dempster, 1918 (c) Mattauch-Herzog, 1935 (d) Bainbridge, 1933. In each case, B signifies the magnetic fieid. Spectrometers (c) and (d) are dispersive mass spectrometers (c) the Mattauch-Herzog design is aiso a doubie-sector instrument, using an electric sector before the magnetic field. Modern versions of these spectrometers are still in use, with the photoplate replaced by one of the modern detectors discussed subsequently.
Figure 4.105 Comparison of the quantum efficiencies of CCD detectors, photoplates and photomultipliers... Figure 4.105 Comparison of the quantum efficiencies of CCD detectors, photoplates and photomultipliers...

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Detectors photoplate detector

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