Vidicon systems

These data show that for the image dissector there is excellent agreement between experimental and theoretical resolution and that the resolution of the image dissector system is about twice as good as that of the vidicon system. The deviation of the resolution of the image dissector from theoretical at 7024.05 A may be attributed to curvature of field in the reduced image of the spectral focal plane because the line is near the edge of the photocathode. 

Biuret Reaction. The particular capabilities of the stop-ped-flow vidicon system have been used to help explain some unusual behavior in the biuret reaction. The biuret reaction is the basis for the standard clinical chemistry technique for determining the total protein content of human blood serum (23). It involves a complexation reaction, in alkaline solution, between the cupric ion (Cu2+) and the peptide bonds of the protein. In the standard biuret technique, the reaction is allowed to go to completion and then the absorbance of the copper-protein complex is measured at 55 nm. This technique tends to be rather slow since the reaction, although very rapid over the first few seconds, does not go to completion for at least 20 to 30 minutes. 

Our experience with experiments performed thus far with the vidicon system have shown that it is a powerful tool. The structure of the system allows new types of operations to be easily designed and rapidly implemented, while modifications of... 

The performances of a Vidicon system as an X-ray detector are best demonstrated by Fig, 19 from Shown is the point-spread function as the response to an illumination of the detector, including a ZnS(Ag)-phosphor screen, through a 35 pm pinhole. 

For this test, the target was scanned by the read-out beam in 256 x 256 steps. The full width of the point-spread function (PSF) is 3 pixels, corresponding to 43 TV-line pairs . At FWHM, the width is 1.5 pixels, or 85 TV-line pairs . Thus the 256 pixels in both directions are not at all independent. This result clearly shows the degradation of the imaging performances of a Vidicon system by the scintillation screen. 

Fig. 18. Scheme of LEED experiment with a fluorescent screen, three-grid system, Faraday cup, and Vidicon system. The diffraction spots are observed visually directly or via the camera and a monitor. The beam intensities can be measured using the Faraday cup or a digitized Vidicon system [1]. Reprinted with permission firom M. Schleberger, S. Speller, and W. Heiland, Exp. Meth. in the Phys. Sci. 30,241 (1998), 1998, Academic Press. 

To avoid the limited wavelength coverage associated with one-dimensional systems, several groups have assembled and demonstrated the feasibility of echelle systems employing either a vidicon (99) or an SEC tube (95). To overcome the somewhat limited linear dynamic range characteristics of vidicons, these systems employ random accessing. 

Switch-Board Optics. The preceding discussion has summarized the various approaches which have been taken to achieve a practical spectrometer for SMA. The direct reader, the vidicon detector, and the development of image device/echelle systems... 

Figure 5. Fiber-optic vidicon spectrometer. (1) Nitrous oxide/acetylene flame (2) SIT vidicon detector (3) Fiber-optic input lenses (4) Fiber-optic entrance slit system (5) 0.5-m Czemy-Turner monochromator (6) Optical multichannel analyzer (7) Oscilloscope display.

Wavelength accuracy. In order to evaluate the ability of each system to locate spectral lines, a preliminary wavelength calibration was carred out with the emission spectrum of a mercury pen lamp and then the peak maxima of several atomic lines from an iron hollow cathode lamp were located. The root mean square (RMS) prediction error, which is the difference between the predicted and the observed location of a line, for the vidicon detector system was 1.4 DAC steps. Because it is known from system calibration data that one DAC increment corresponds to 0.0125 mm, the absolute error in position prediction is 0.018 mm. For the image dissector, the RMS prediction error was 7.6 DAC steps, and because one DAC step for this system corresponds to 0.0055 mm, the absolute error in the predicted coordinate is 0.042 mm. The data in Table II represent a comparison of the wavelength position prediction errors for the two detectors. 

Comparisons with other systems. Data presented in Table VI provide a comparison of results obtained with the image dissector with results reported by others with other systems. Results in the second column represent multielement detection limits observed in this work. Results in the third and fourth columns represent detection limits reported for single element determinations with conventional optics and a silicon vidicon (12J and a commercial atomic absorption instrument (33). 

The multielement detection limits with the echelle/image dissector are comparable to, or better than, single element detection limits reported for a silicon vidicon and conventional optics. Detection limits for Cr, Cu, and Mn with the echelle/ image dissector compare favorably with single element data reported for a conventional atomic absorption instrument with a photomultiplier detector, but detection limits obtained here for Ni and Co are higher by factors of 10 or more than for the conventional instrument. The echelle/image dissector system should be adaptable to a so-called flameless atomizer and be subject to the same improvements in sensitivities and detection limits as conventional detector systems. 

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