Bragg spectrometer

It has been explained (1.15) that the angle 20 must be maintained between a fixed sample and a movable detector in a Bragg spectrometer. The sample being fixed, the collimator near the sample must also be fixed. The detector being movable, the collimator near the detector must obviously move with the detector. 

BRAGG SPECTROMETER. An instrument for the x-ray analysis of crystal structure, in which a homogeneous beam of x-rays is directed on the known face of a crystal, C. and the reflected beam detected in a suitably placed ionization chamber, E. As the crystal is rotated, the angles at which... 

See also Bragg s Law Bragg Spectrometer and Bragg s Rule. 

Table 1. Calculated electromagnetic energies and line widths of the antiprotonic transitions measured with the crystal spectrometer. The energy resolution AEexp of the Bragg spectrometer was determined from narrow transitions of antiprotonic noble gases. Ob stands for the Bragg angle...

Ti(acac)2 was rapidly and quantitatively analyzed by X-ray fluorescence (XRF) spectroscopy. Fe(acac)2 was similarly determined by XRF with correction for Compton scattering. An instrumental geometrical factor and an equivalent wavelength were obtained experimentally, while all the other factors were calculated with the mass absorption coefficients of Fe ". K and XRF spectra of Cr(acac)3 and other Cr compounds were measured with a Bragg spectrometer. The relative intensities of the 3, K 2, K / and K lines with respect to the K line confirm the chemical effect on the intensity... 

D.R Anagnostopoulos, S. Biri, D. Gotta, A. Gruber, P. Indelicato, B. Leoni, H. Fuhrmann, L.M. Simons, L. StmgeUn, A. Wasser, J. Zmeskal, On the characterisation of a Bragg spectrometer with X-rays from an ECR source, Nucl. Instrum. Methods A 545 (2005) 217. 

Ions, in particular protons from a particle accelerator, in the energy range 1 —4 MeV, are used with beam spots 1 pm—10 mm in diameter. a-Particles from some radioactive sources ( " Am) can also be used for excitation. The energy of emitted photons is measured by a wavelength dispersive Bragg spectrometer or by an energy-dispersive spectrometer with semiconductor Si(Li) or Ge(Li) detectors. 

Before the development of semiconductor detectors opened the field of energy-dispersive X-ray spectroscopy in the late nineteen-sixties crystal-spectrometer arrangements were widely used to measure the intensity of emitted X-rays as a function of their wavelength. Such wavelength-dispersive X-ray spectrometers (WDXS) use the reflections of X-rays from a known crystal, which can be described by Bragg s law (see also Sect. 4.3.1.3)... 

The spectrometer is set to the appropriate Bragg angle 0 of the requisite characteristic wavelength, and only these X-rays will reach the detector and be counted. The detector employed is the gas proportional counter, which can operate at much faster count rates than the EDS crystal detector. 

The XAS spectrometer is similar to a UV-visible system in that it consists of a source, a monochromator, and a detector. The most favorable XAS source, synchrotron radiation, is tunable to different wavelengths of desirable high intensity. A laboratory instrument for analysis of solids and concentrated solutions may use a rotating anode source (further described in Section 3.3). The monochromator for X-ray radiation usually consists of silicon single crystals. The crystals can be rotated so that the wavelength ( i) of the X-rays produced depends of the angle of incidence (0) with a Bragg lattice plane of... 

Figure 13.8—Reflecting crystals used in goniometers of dispersive spectrometers and Bragg s relationship. The higher the wavelength to be analysed, the higher the inter-reticular distance must be in the crystal.

FTIR spectra were recorded with an Impact 410 (Nicolet) spectrometer. Powder X-ray diffraction data were obtained on a Siemens D 5005 diffractometer in the Bragg-Brentano geometry arrangement using CuKa radiation. Adsorption isotherms of nitrogen at -196 °C... 

Figure 1. Schematic of a triple-axis inelastic neutron spectrometer. The thermal-ized beam from the reactor is monochromated by Bragg reflection from crystal M. Neutrons that scatter from the sample S are energy analyzed by Bragg reflection from crystal A and enter detector D.

The energy calibration was obtained with Si and S Ka fluorescence X-rays excited by means of an X-ray tube. Because the natural widths of the fluorescence X-rays exceed the experimental resolution at least by a factor of two, the response function of the spectrometer was determined from the narrow antipro-tonic transitions pHe(5g — 4/) and pNe(13p — 12o), lines which are not affected by the strong interaction. For the 1.7 keV Balmer a transition from pH, quartz crystals are the only possible choice for the Bragg crystal. The theoretical limit for the resolution of 180 meV was missed by a factor of 1.7 (Table 1). In the case of pD, a silicon crystal was used because of its higher reflectivity. Here, the theoretical limit for the resolution of 360 meV was reached [21]. 

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