Detectors scattering

Fig. 2. The layout of synchrotron X-ray small angle scattering measiurements. The optical system selects X-rays with a narrow band-width from the continous wavelength distribution of synchrotron radiation. Intensity of the primary>beam at the sample lo is monitored by an ion chamber. ly is the transmitted beam, and, I(s), the scattered intensity is recorded with a position sensitive detector. Scattering patterns of fibres are presented as Log (sl(s)) vs s plots where s = 2 sin 0/X is the scattering vector. 26 is the scattering angle and X is the wavelength.

The carrier mobility is determined mainly by impurity scattering at the low temperatures of extrinsic photoconductor operation. Furthermore, in the relatively uncompensated Si of most interest for detectors, scattering by the neutral majority dopant atoms will dominate. It can be shown that the neutral impurity scattering mobility is given in Si by [4.65]... 

A second divergence slit Urtrits the in-plane divergence of the beam. The diffracted beam can also pass through a second Soller slit or monoehrorrtator before striking the detector. Scatter slits may be used to reduee baekgrourrd. 

The sensitivity curves are plots of maximum achieved sensitivity as a function of thickness of the object for a given focal spot size and source to detector distance. The best attainable sensitivity in image intensifier systems is a function of tube voltage, current, scattered radiation and the screen gamma. As a first step, stainless steel plates with thicknesses ranging from 5 mm-30 mm in steps of 5 mm were chosen. These plates had a length of 950 mm and width of 280 mm. The plate is positioned very close and at the center to the LI. tube. The extraneous... 

Figure Bl.10.7. Electron impact ionization coincidence experiment. The experiment consists of a source of incident electrons, a target gas sample and two electron detectors, one for the scattered electron, the other for the ejected electron. The detectors are coimected tlirough preamplifiers to the inputs (start and stop) of a time-to-amplitiide converter (TAC). The output of the TAC goes to a pulse-height-analyser (PHA) and then to a nuiltichaimel analyser (MCA) or computer.

Figure Bl.10.11. Electron impact double ionization triple coincidence experiment. Shown are the source of electrons, target gas, tluee electron detectors, one for the scattered electron and one for each of the ejected...

In SEM and STEM, all detectors record the electron current signal of tire selected interacting electrons (elastic scattering, secondary electrons) in real time. Such detectors can be designed as simple metal-plate detectors, such as the elastic dark-field detector in STEM, or as electron-sensitive PMT. For a rigorous discussion of SEM detectors see [3],... 

Figure Bl.17.3. STEM detectors (a) conventional bright and dark-field detectors, electrons are detected according to their different scattering angles, all other positional infonnation is lost (b) positional detector as developed by Haider and coworkers (Haider etal 1994).

In TOF-SARS [9], a low-keV, monoenergetic, mass-selected, pulsed noble gas ion beam is focused onto a sample surface. The velocity distributions of scattered and recoiled particles are measured by standard TOF methods. A chaimel electron multiplier is used to detect fast (>800 eV) neutrals and ions. This type of detector has a small acceptance solid angle. A fixed angle is used between the pulsed ion beam and detector directions with respect to the sample as shown in figure Bl.23.4. The sample has to be rotated to measure ion scattering... 

Figure Bl.23.4. Schematic diagram of TOE scattermg and recoiling spectrometry (TOF-SARS) illustrating the plane of scattering fonned by the ion beam, sample and detector. TOE spectra (a) are collected with fixed...

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