Two Dimensional Position Sensitive Detector

Oriented polymers will no longer show a symmetric scattering pattern. For such systems a two dimensional detector is necessary. A commercial data aquisition system (Westinghouse), based on a Vidicon tube, is shown in Fig. 32. The video signal 

Monitor Remote control cabinet Video recorder 

At present up to 128 video frames can be digitized and further processed with the image analyzing system CA-1. 

Typical pictures obtained during the conversion of smectic polypropylene into the a-phase are shown in Fig. 33. 

The response of the detector to an incident flux of photons is shown in Fig. 34. Only one line of the video frame was analyzed. This allows a comparison with the linear detector (3.4.1), Evidently the Gd202S-scintillator is appropriate for weak scattering and the ZnS-scintillator for stronger scattering events. No saturation was observed for the latter scintillator up to 2.1 10 counts s which is a considerable improvement over the linear detector. 

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The photolysis of aromatic species with tetranitromethane in perfluoro alcohol solvent has been studied, in which the radical cations were observed by EPR spectroscopy.284 Photo-stimulated reaction of 1- and 2-haloadamantanes and 1,2- and 1,3-dihaloadamantanes with various carbanionic nucleophiles afforded products rationalized through an SrnI mechanism.285 286 Photolysis of the cycloadduct formed between a functionalized derivative of C6o and diazomethane has been shown to afford a pah of ling-opened structures (125) and (126) via a proposed biradical intermediate (127) (Scheme 19). The UV-photolytic fragments of /-butyl iodide (T and /-Bu ) have been ionized by resonance-enhanced multiphoton ionization for TOF mass spectro-metric analysis.287 A two-dimensional position-sensitive detector provided angular distribution and translational energy data. 

In addition to the standard discussion of the materials studied, and processing and analytical techniques employed for this work, a rather lengthy presentation on two-dimensional position sensitive detectors for SALS will be presented. A review of prior work performed by other researchers will be discussed, as well as the particulars of the detector developed for this study. Finally, a comparison between the detector presented here, and those developed previously will be made. 

GAB 78] GABRIEL A., DAUVERGNE F., ROSENBAUM C., Linear, circular and two dimensional position sensitive detectors , Nucl. Instrum. Meth., vol. 152, p. 191-194,1978. 

The area detector is an electronic device for measuring many diffracted intensities at one time. It is a two-dimensional, position-sensitive detector that records the intensity of a Bragg reflection (diffracted beam) and its precise direction (as a location on the detector) it acts like an electronic substitute for film. This detection device is now used extensively for crystals of biological macromolecules. Such a detector may involve a multiwire proportional counter coupled to an electronic device or a television imaging system both devices permit a recording of the data in a computer-readable form. Alternatively, imaging plates may be used. These have phosphorescent material layered on them and store information on the extent of X-ray exposure until scanned bv a laser, when the intensity and location of the light then emitted is recorded. 

Various multiwire proportional counters (MWPC) have been designed for use as two-dimensional position-sensitive detectors. An example of such a design is illustrated in Figure 2.17. Here a plane of fine, equally spaced parallel wires functions... 

In comparison with film cameras, diffractometers are roughly a factor of 10 more costly. They are still more expen.sive if the point counter is replaced by a one- or two-dimensional position-sensitive detector. The data acquisition time is, however, shortened by a factor of 50-100, or even more, depending on the geometry of the crystal lattice measured. 

Fig. 6. Principle of pinhole SANS a neutron beam entering the instrument from the left is the subject of monochromation (done by the velocity selector), coUimation over a variable distance (achieved by using a set of adaptive system of apertures), scattering on the sample and detection on a two-dimensional position sensitive detector over long distances airning for detecting neutrons at small scattering angles the SANS instruments are very long.

Some measurements were performed using an X-ray source with rotating anode and a pinhole collimation [5]. The rest of the measurements were carried out using the synchrotron radiation generated at the beamline A2 of HASYLAB in Hamburg, Germany. The intensity was measured by means of one- and two-dimensional position-sensitive detectors, respectively. 

Small Angle X-ray Scattering (SAXS). SAXS experiments were made with the Bruker Anton-Paar instrument, which included a Rigaku RU-300 rotating anode (Cu Ka radiation 1 = 0.154 nm) and a two dimensional position-sensitive detector. The sample-to-detector distance used was 64.5 cm, and the samples were 1 mm thick compression molded disks. 

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