Filters balanced

The background of a diffraction pattern obtained with a diffractometer may be reduced by means of a single-channel pulse-height analyzer, as mentioned in Sec. 7-9. An even better method is to use a crystal monochromator in the diffracted beam. Balanced filters present still another option. 

Note also that balanced filters will not exclude Compton scattering, which differs in wavelength by only 0.05 A or less from the wavelength of the diffracted beam (Eq. 4-3) and which will therefore generally fall inside the pass band. And if the radiation forming the diffracted beam is, for example, Cu Aix, then neither a monochromating crystal nor balanced filters will exclude diffusely scattered Cu Kci caused, for example, by thermal vibration of the atoms. 

The proper filter, inserted between sample and counter, can prevent much unwanted radiation from reaching the counter. For example, in the analysis of brasses (Cu-Zn alloys), a Ni filter will pass much of the Cu Koc radiation and absorb most of the Zn Koi. Selective filtration is most effective when the wavelengths to be separated are close together or widely apart, because, in either case, a filter can be chosen with quite different absorption coefficients for the two wavelengths. Balanced filters (Sec. 7-13) have also been used. 

Figure 14.8. Balanced filters for isolating Sn Ka radiation. The transmission and absorption filters are made of silver and palladium, respectively.

Figure 4.39 The principle of balanced filters. The difference in transmission between the copper and nickel filters is in the cross-hatched energy window between the K absorption edges of nickel and coppier. (Reprinted by courtesy of EG G ORTEC.)... 

X-ray measurements were carried out on a Rigaku Denki diffractometer with an X-ray generator D-IOC. The monochro-matization of Cu-Ka radiation was achieved by a Ross balanced filter. The intensity was counted for a fixed time of 100s by a scintilation counter and pulse height analyzer over a scattering angle from 1—150 at interval of 0.1 . After... 

A diagram of the small-angle x-ray scattering apparatus is shown in Figure 16.1. The x-ray source is a tube with a water-cooled copper anode, usually using a Kratky camera for measurement. The tube is operated at, for example, 30 kV direct current (dc) and a current of, for example, 80 mA. The total flux incident on the sample is approximately 10 photons/s. Monochromatization was achieved with balanced filter of nickel and cobalt foil which isolate the CuKa line. The x-ray wavelength (the most frequently used CuKa line) is 1.54 A. 

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