Profile studies, line

Crystallinity and disorder are important structural parameters for understanding relationships between structure and physical properties. Flaws and distortions are the main features that limit the ultimate properties of textile fibers. Some of these crazes, cracks and voids are revealed under the electron microscope, either on the surface or in cross sections stained with heavy metals (J, 2). However, these staining techniques (that reveal the main morphological features) make it much more difficult to determine the degree of distortion of the crystalline fraction. Theoretically, line profile studies permit separation of effects due to crystalline size from those due to structural distortions. However, the lack of peaks in semicrystalline fiber x-ray patterns hinders that approach. 

Currently available software enables the accumulation of spectra from an arbitrary number of laser shots with an arbitrary number of successive repetitions. This mode of operation is specially suitable for depth profile analysis. By way of example, in order to determine two components in a depth profiling study, a series of pulses are accumulated by maintaining a constant laser fluence. The experimentally measured intensities of the lines selected for the two elements are normalized to their maximum values to account for the difference in oscillator strength of the lines. Such values are then normalized to the sum of the intensities of both elements. Normalization to the combined intensities is equivalent to normalization to the ablated mass. This procedure is unsuitable for the lower layers of a sandwich close to the substrate, for which normalization should also include the line intensity for the substrate element. 

Figure 10 Possible absorption profiles obtained from experiments with isolated perfused lung or absorption profiles obtained after proper deconvolution from inhalation studies. Lines present drugs with different absorption rates. Circles = fast, squares = intermediate, and hexagons = slow absorption rates. 

The above discussion is presented merely to give an idea of the types of EUV detectors and their applications in use on present fusion plasma experiments. It is by no means an exhaustive list of possibilities. Indeed, several different detectors are in use or being planned in future experiments. Resistive anode encoders will probably see more use in fusion experiments as they become commercially available. However, the low count rates available ( 10 to 10 sec-1) will result in these detectors being used mostly for line profile studies (e.g., ion temperature measurements via Doppler broadening measurements). Intensified CCD arrays (back-illuminated or otherwise), vidicon or CID systems, lens-coupled intensifiers, and anode detectors have all seen some use on tokamak experiments or are planned for the near future, but have not been widely used as yet. However, in terms of availability, pixel format, dynamic range, insensitivity to magnetic fields, compact package, and moderate cost, the IPDA remains the most versatile multichannel EUV detector for plasma spectroscopy. 

Figure 4 Phase diagram for CO2 including typical ocean temperature profile (solid line). Reprinted from Brewer PG, Peltzer E, Aya I, et al. (2004) Small scale field study of an ocean CO2 plume. Journal of Oceanography 60(4) 751.

To achieve the desired accuracy in X-ray energies, from the spectra collected in the different experiments, one needs to know precisely the line shape produced by the spectrometer. This line shape can be used to fit the experimental spectra. An extra difficulty comes from the two-dimensional nature of the spectra. Theoretical line shapes are produced by the following procedure crystal diffraction profiles at the studied line energy are obtained from the XOP code [18] a complete Monte-Carlo simulation is then made, using this diffraction profile and all geometrical informations from fhe insfrument. The CCD detector is positioned perpendicular to the optical axis of fhe spectrometer. There is thus only one place on the detector (the intersection of fhe optical axis and of the detector) located at the focal disfance. Away from fhis point, lines are slightly defocused. Once obtained, the... 

The imaginary part has a Lorentzian profile of halfwidth centred at exact resonance. This Lorentzian line shape comes from the assumed form for the damping terms, and more realistic models should be used in Equation [14] when studying line shapes. The spectral shape is the same as for spontaneous Raman lines. The real part of is multiplied by the detuning, and shows a dispersive line shape. depends on the population difference, instead of just the population of the initial state as does spontaneous Raman. This dependence can lead to saturation whenever appreciable population is transferred to the excited level. 

To apply the corrective measures to limit the Ferranti effect it is essential to first study its over voltage (OV) status at the far end of the line. Consider the earlier system TZ of 400 kV 50 Hz and draw a voltage profile as illustrated in Figure 24.17, for the voltages worked out as in equation (24.7), at different lengths of the line. The voltages, for the sake of simplicity, are also shown in Table 24.4. 

By integration of the loeal slopes, we have reconstructed the micro-mirror surface. An example is shown in Fig.4, along the line indicated by an arrow on the slope map. The surface deformations do not exceed 1 nm along the studied profile. Although surface shapes vary from mirror to mirror, deformations in the nanometer range demonstrate the remarkable quality of this device. 

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