Detector photographic plate

Mattauch-Herzog geometry, which simultaneously focuses all resolved masses onto one plane, allowing the integrating properties of an ion-sensitive emulsion to be used as the detector. Although electrical detection with an electron multiplier can be applied, the ion-sensitive emulsion-coated glass photographic plate is the most common method of detection and will be described in this article. 

The effect of an absorbed x-ray quantum on a photographic plate is visible as metallic silver after the plate has been developed and fixed. The number of quanta absorbed help to determine the amount of this metallic silver, and the development process performs somewhat the same function as amplification in a gas-filled detector (2.5). 

The comprehensive investigation by Eddy and Laby5 may serve as the classic example of what can be accomplished with electron excitation and a photographic plate as detector. Their results on a copper-zinc alloy are particularly remarkable for the high precision attained. To be sure, this case is among the most favorable that can be imagined. 

Laby21 demonstrated in 1930, with a photographic plate as detector, that copper or iron in zinc could be detected in concentrations approaching 1 part per million by weight. To be sure, he used electron excitation so that absorption effects were minimized (7.10). By contrast, attempts made in the authors laboratory to estimate alkaline-earth metals in brines were unsuccessful, primarily because of the high absorption effects that accompanied x-ray excitation. The use of dilution with a relatively transparent solvent can sometimes reduce or eliminate absorption effects (7.8), but this procedure will fail if the element to be determined is present at too low a concentration in the presence of another substance (the salt in brine in the example cited) primarily responsible for the absorption effect. A case in which dilution is helpful in connection with the absorption effect of the. element sought is that of tetraethyllead fluid in gasoline (7.13). 

The following general observations apply to both kinds of problems. The scale of operations is fixed by the necessity of comparing adjacent sections of tissue only microns in width, which makes it advisable to use the photographic plate as detector, in order that the necessary measurements of x-ray intensity can be made on greatly enlarged areas. Inas-... 

Information density (storage density) Da = Ma / a Dv = Mv/v bit/cm2 bit/cm3 Static detectors, e.g., photographic plate a, v spatial storage unit... 

Once ions have been produced and analysed they must be detected. Indeed, the detector is the final part of a mass spectrometer. At the start of MS, detectors were composed of a fluorescent screen or a photographic plate the modem instruments are equipped with detectors able to transform the signal produced by the ion beam into an electric current that is transmitted to the data system. 

A recent modification of mass spectrometric technique involves the use of a spark source. A spark is struck by means of a high voltage between two rods of the material under examination. Under this drastic treatment many substances decompose completely into their elements and give positive ions. The ion detector is usually a photographic plate which shows a line mass spectrum. A number of exposures are taken for each sample and a quantitative estimate of the presence of an element in the sample can be made from the exposure time. 

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