Cross-section detector

The electron capture detector is the result of a series of developments which were initiated in 1951 by D. J. Pompeo and J. W. Otvos (14) of the Shell Company s development laboratory in California. The device they invented was a beta-ray ionization cross-section detector (Section 5.8). Deal et al. (15) at the Shell laboratory in California and Boer (16) in Amsterdam modified the detector, used originally to monitor effluents of a large scale plant process, for applications in GC. From the limited success of the detector. Lovelock (17) produced the beta-ray argon detector in 1958 (Section 5.8). This modification substituted argon as the carrier gas and placed a potential of 1000 V across the electrodes. Argon passing between the electrodes absorbed radiation and formed a metastable species with energy (11.6 eV) sufficient to ionize most substances. Proposed mechanisms for this process are ... 

The type of detector to be employed determines the nature of the carrier gas which may be used. Argon is used with the argon ionization detector. Helium is used with flame-ionization, thermal conductivity, thermionic emission, and cross-section detectors. Hydrogen may be used in thermal conductivity detectors to give maximum sensitivity. Probably the commonest and cheapest carrier gas is nitrogen, which can be used with flame-ionization, electron capture, thermal conductivity, and cross-section detectors. Argon-methane mixtures may be used with electron capture detectors. 

The INTROS Flaw Detector is able to inspect ropes moving through the magnetic head at speed 0...2 m/s. Limit of sensitivity to wire brake is 1% of the rope meatallic cross-section area, the LMA measure accuracy is not less than 2%. 

In case of some samples besides the cross sectional CT-slice also a projectional image is of interest. In these cases the test mode Digital Radiography (DR) is applied. In the DR-mode the object is not turned, but scanned horizontally and vertically. Again the very high dynamic of the detector and the mechanical accuracy of the complete system are of large benefit to the image quality. 

In situ measurement of the concentration of radioactive tracers in the different phases requires that the phases are separated and arranged according to density difference over the measurement cross section in a horizontal pipe. In general, the measurements are performed with two spectral gamma radiation detectors placed on top and bottom of the pipe respectively. 

In the case, where all 3 phases are present, the detector measurements reveal the amounts of tracers in each phase and the position of the boundaries between the phases The cross section area of each phase is calculated fi-om the latter. From this the tracer concentrations and hence the volume flows of the 3 phases are calculated. 

Let the rate of the event under study be R. It will be proportional to the cross section for the process under study, a, the incident electron current, Iq, the target density, n, the length of the target viewed by the detectors,, the solid angles subtended by the detectors, Aoi and A012 the efficiency of the detectors, and... 

For the background, each of the rates, andi 2> will be proportional to the source fimction, the cross sections for single electron production and the properties of the individual detectors. 

By inserting a semiconductor x-ray detector into the analysis chamber, one can measure particle induced x-rays. The cross section for particle induced x-ray emission (PIXE) is much greater than that for Rutherford backscattering and PIXE is a fast and convenient method for measuring the identity of atomic species within... 

At low energies the abstraction process dominates and at higher energies the exchange mechanism becomes more important. The cross-sections for the two processes crossing at 10 eV. The END calculations yield absolute cross-sections that show the same trend as the experimentally determined relative cross-sections for the two processes. The theory predicts that a substantial fraction of the abstraction product NHjD, which are excited above the dissociation threshold for an N—H bond actually dissociates to NH2D" + H or NH3 during the almost 50-ps travel from the collision chamber to the detector, and thus affects the measured relative cross-sections of the two processes. 

Eig. 17. Cross-sectional schematic of a microbolometer photodetector. Micromachining is used to constmct small, very low mass detectors. The dimension... 

The detected yield is a function of the concentration of the element being profiled, the resonance cross section, the detector efficiency, and dE/dx. To be specific. 

Figure 2 Cross section versus incident proton energy for the (p, cx) N reaction, with a beam-detector angie of 165°. ...

Fig. 4.6. Cross section of the front end of an SSD (solid-state detector), here Gold contact with a grooved Si(Li) crystal. Crystal and preamplifier are connected with a cooled copper rod and shielded by a case with an end cap and Be window [4.21, 4.29].

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