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Spectra detectors

Instrument control. The main requirement for a control system is the ability to acquire X-ray fluorescence spectra (detector acquisition on, off, save, clear) in coordination with a scanning routine manipulating the sample stage and monochromator energy. [Pg.436]

The fringes contrasts are subject to degradation resulting from dissymmetry in the interferometer. The optical fields to be mixed are characterized by a broadband spectrum so that differential dispersion may induce a variation of the differential phase over the spectrum. Detectors are sensitive to the superposition of the different spectral contributions. If differential dispersion shifts the fringes patterns for the different frequency, the global interferogramme is blurred and the contrast decreases. Fig. 5 shows corresponding experimental results. [Pg.295]

Fig. 15. Basic equipment for measuring a nuclear inelastic scattering spectrum. Detector 1 measures the intensity of the incoherent nuclear forward scattering, which proceeds both elastically and inelas-tically detector 2 measures only the intensity of the coherent nuclear forward scattering, which proceeds elastically. Figure according to Ruffer and Chumakov (224). Fig. 15. Basic equipment for measuring a nuclear inelastic scattering spectrum. Detector 1 measures the intensity of the incoherent nuclear forward scattering, which proceeds both elastically and inelas-tically detector 2 measures only the intensity of the coherent nuclear forward scattering, which proceeds elastically. Figure according to Ruffer and Chumakov (224).
The experiments that have been performed are standard. Critical configurations have been determined for many different compositions. Reactivity coefficients have been determined by period measurements or by use of control rods calibrated by period measurements. Reactivity worths have also been determined analysis of the response to oscillator and rod drop experiments. Rossl-o measurements have been made on a number of assemblies to determine the ratio (rf the effective delayed neutron fractlqn to the prompt neutron lifetime and thus indirect to give information on the neutron spectrum. Detector responses, both as a function of detector material and as a function of position, have been made to determine data relevant to power distributions, bucklings, reflector savings, and neutron spectra. Spectrum measurements have been made by use of ehiulslon plates. [Pg.87]

Figure 9. Schematic of the electron-optical arrangement designed by Coxon et al. [15] for the production of energy-resolved two-dimensional images in XPS a) Spherical mu-inetal chamber b) Lens 1 c) Objective aperture d) Field aperture e) Lens 2 f) Lens 3 g) 180 Hemispherical analyzer h) Hole i) Spectrum detector 1 j) Lens 5 k) Image detector 2... Figure 9. Schematic of the electron-optical arrangement designed by Coxon et al. [15] for the production of energy-resolved two-dimensional images in XPS a) Spherical mu-inetal chamber b) Lens 1 c) Objective aperture d) Field aperture e) Lens 2 f) Lens 3 g) 180 Hemispherical analyzer h) Hole i) Spectrum detector 1 j) Lens 5 k) Image detector 2...
In terms of relative practical sensitivity, the Mass Spectrum Detector (MSD) in the scanning mode is approximately 10 times better than the Infrared Detector (IRD). Thus, a mass spectrum on a level of 1 ng requires 10 ng for an IR spectrum if the compound is a strong absorber. [Pg.378]

The first requirement is a source of infrared radiation that emits all frequencies of the spectral range being studied. This polychromatic beam is analyzed by a monochromator, formerly a system of prisms, today diffraction gratings. The movement of the monochromator causes the spectrum from the source to scan across an exit slit onto the detector. This kind of spectrometer in which the range of wavelengths is swept as a function of time and monochromator movement is called the dispersive type. [Pg.57]

Sandborg, M. and G. Alm-Carlsson, Influence of x-ray energy spectrum, contrasting detail and detector on the signal-to-noise ratio (SNR) and detective quantum efficiency (DQE) in projection radiography. Phys. Med. Biol., 1992. 37(6) p. 1245-1263. [Pg.215]

A connnon teclmique used to enliance the signal-to-noise ratio for weak modes is to inject a local oscillator field polarized parallel to the RIKE field at the detector. This local oscillator field is derived from the probe laser and will add coherently to the RIKE field [96]. The relative phase of the local oscillator and the RIKE field is an important parameter in describing the optical heterodyne detected (OHD)-RIKES spectrum. If the local oscillator at the detector is in phase with the probe wave, the heterodyne mtensity is proportional to... [Pg.1208]

A connnon approach has been to measure the equilibrium constant, K, for these reactions as a fiinction of temperature with the use of a variable temperature high pressure ion source (see section (Bl.7.2)1. The ion concentrations are approximated by their abundance in the mass spectrum, while the neutral concentrations are known from the sample mlet pressure. A van t Hoff plot of In K versus /T should yield a straight Ime with slope equal to the reaction enthalpy (figure B1.7.11). Combining the PA with a value for basicityG at one temperature yields a value for A.S for the half-reaction involving addition of a proton to a species. While quadnipoles have been tire instruments of choice for many of these studies, other mass spectrometers can act as suitable detectors [19, 20]. [Pg.1343]

Time-of-flight mass spectrometers have been used as detectors in a wider variety of experiments tlian any other mass spectrometer. This is especially true of spectroscopic applications, many of which are discussed in this encyclopedia. Unlike the other instruments described in this chapter, the TOP mass spectrometer is usually used for one purpose, to acquire the mass spectrum of a compound. They caimot generally be used for the kinds of ion-molecule chemistry discussed in this chapter, or structural characterization experiments such as collision-induced dissociation. Plowever, they are easily used as detectors for spectroscopic applications such as multi-photoionization (for the spectroscopy of molecular excited states) [38], zero kinetic energy electron spectroscopy [39] (ZEKE, for the precise measurement of ionization energies) and comcidence measurements (such as photoelectron-photoion coincidence spectroscopy [40] for the measurement of ion fragmentation breakdown diagrams). [Pg.1354]

Figure Bl.10.8. Time spectrum ftom a double coincidence experiment. Tln-ough the use of a delay in the lines of one of the detectors, signals that occur at the same instant in botii detectors are shifted to tlie middle of the time spectrum. Note the unifonn background upon which the true comcidence signal is superimposed. In order to decrease the statistical uncertainty in the detemiination of the true coincidence rate, the background is sampled over a time Aig that is much larger than the width of the true coincidence signal. Ax. Figure Bl.10.8. Time spectrum ftom a double coincidence experiment. Tln-ough the use of a delay in the lines of one of the detectors, signals that occur at the same instant in botii detectors are shifted to tlie middle of the time spectrum. Note the unifonn background upon which the true comcidence signal is superimposed. In order to decrease the statistical uncertainty in the detemiination of the true coincidence rate, the background is sampled over a time Aig that is much larger than the width of the true coincidence signal. Ax.
Referring to figure BLIP. 7 consider electrons from the event under study as well as from other events all arriving at the two detectors. The electrons from the event under study are correlated in time and result in a peak in the time spectrum centred approximately at the delay time. There is also a background level due to events that bear no fixed time relation to each other. If the average rate of tlie background events in each detector is R and i 2> then the rate that two such events will be recorded within time Ax is given by i g, where... [Pg.1429]

In contrast to IR and NMR spectroscopy, the principle of mass spectrometry (MS) is based on decomposition and reactions of organic molecules on theii way from the ion source to the detector. Consequently, structure-MS correlation is basically a matter of relating reactions to the signals in a mass spectrum. The chemical structure information contained in mass spectra is difficult to extract because of the complicated relationships between MS data and chemical structures. The aim of spectra evaluation can be either the identification of a compound or the interpretation of spectral data in order to elucidate the chemical structure [78-80],... [Pg.534]


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