Vidicon detectors

The observations of the lithium resonance line at x6708.8 A were carried out with a SIT vidicon detector attached to the coudi spectrometer of the 1.5 m telescope of the Tartu Astrophysical Observatory. The sample of stars observed consists of 70 K0 - K5 and 75 MO - M4 giants. A set of spectra of K giants with different strengths of lithium resonance doublet is shown in Fig. 1. 

Princeton Applied Research. "OMA Vidicon Detectors" PAR Princeton, N.J., 1978. 

Figure 1. Diode structure and principles of operation of the silicon vidicon detector...

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. 

As with any detector, the vidicon detector has a number of limitations, many of which have not yet been thoroughly explored. To facilitate the characterization of the detector and the determination and minimization of its limitations, we wanted to place a large number of the vidicon scanning parameters under computer control. 

Before any instrument can be used with confidence its operating characteristics must be well understood. The exceptional versatility of the vidicon rapid scanning stopped-flow system allowed a large variety of characterization experiments to be easily performed. A few of the more important experiments designed to help characterize the vidicon detector will be presented before the actual application of the instrument is discussed. 

Resolution. The resolution of the vidicon spectrophotometer is limited by the vidicon detector. The resolution of the... 

Lag seriously degrades the response time of the vidicon detector and, therefore, it is the feature which most severely limits the applicability of vidicon detectors to fast kinetics. Lag measure-... 

Vidicon Detector Systems. It was obvious to many workers that the use of a television camera tube as the light detector would offer a number of advantages over the photomultiplier tube. The viewing of the image in real time would aid in aligning the optical system and also in decision making during an experiment. 

When the commercial OMA (Model 1205, Princeton Applied Research Corporation, Princeton, NJ) became available, we recognized its potential as a replacement for the photomultiplier detector. The vidicon detector surface was divided into 500 channels, the image could be seen on a cathode ray tube (CRT) monitor in real time, the intensity profile was available in digital form, the profile could be time-averaged for any desired number of video scans, and the final profile was stored in internal memory for transfer to an external output device. Not only had a considerable amount of work gone into its development and the verification of performance, but its potential for use for a variety of physical techniques would ensure the construction of enough units to support further development of the system. Moreover the need for low-light-level detectors for other purposes would lead to further improvements in detector devices. 

Other reports deal with individual elements, such as Ni [1, 86, 87] or Fe [11,84]. The efficiency [71—73] of flame methods (AAS) has been compared with flameless techniques (NFAAS) (Table 6). Because of their significance there have been attempts to determine the elements P [38] and S [78] directly with AAS. This, however, requires a device which can measure ultraviolet lines (ca. 180 nm) with sufficient sensitivity. Good results can also be achieved by gas chromatographic separation and successive AAS determination [92] and simultaneous multielement analysis with a Vidicon-detector has been tried [68] because the speed with which the information is gained can be very important in practice. Some work [39, 53] reports on the problem of molecular bands which can appear when working with... 

Fig. 34. Response of a Vidicon detector to an incident flux of X-rays. The integrated flux of scanline is correlated with the output of the Vidicon for two different scintillators...

The stretch induced transformation of initially unoriented orthorhombic polyethylene (Vestolen A) into the monoclinic modification was studied by Heise, Riekel and Stach for stretching velocities down to 0.26 mm s"T The coexistence of both modifications and the formation of two domains of monoclinic material was established by the Vidicon detector. 

The sensitivity of a vidicon detector over its area is subject to nonuniformities of the scintillator screen, the photocathode, and the target. A typical result of a sensitivity test is shown in Fig. 19b from K It is very stable and therefore the data can be corrected in a reliable way. 

An early example of surface Raman without field enhancement is shown in Figure 13.7. This measurement predated the development of CCD detectors and represents a major achievement in terms of sensitivity (12). The adsorption of nitrobenzene on a well-defined nickel surface was carried out in UHV then Raman scattering was observed with a single spectrograph and an intensified Vidicon detector. Unenhanced spectra were obtained from 7.5 x lO molecules cm of nitrobenzene (1.1 x 10 " mol cm ), corresponding to a submonolayer. Examples of surface Raman spectroscopy with resonance enhancement include monolayers of phthalocyanines on gold (17) and ordered graphite (18), and multilayers of metalloporphyrins (19). 

Coupling an SIT vidicon detector with an on-line computer for detector control, experiment synchronization, data acquisition and data processing results in a powerful and flexible detection system. The flexibility results from the... 

OLESIK AND WALTERS Silicon-Intensified Target Vidicon Detector... 

The most obvious limitation of vidicon detectors is the small detector area. Typically, the SIT vidicon detector area is 12.5 by 12.5 mm. However, the useful detector area may be further limited by distortion which is most severe near the edges of the detector, as will be discussed below. If a polychromator with a dispersion of 0.83 nm/mm is used, a wavelength range of 10 nm can be monitored when the full width of the vidicon is used. 

Blooming limits the resolution obtainable with vidicon detectors. For example, if an atomic line with a 0.02 nm line width is observed through a polychromator with 0.83 nm/mm... 

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