Self-attenuation

The extension of XRD from small samples to extended objects requires two main modifications of Eq. 10 to account for the self-attenuation of X-rays within the object and also to describe the component of scatter signal that suffers more than one interaction within the object. 

Overwater, R.M.W., Bode, P., De Goeij, J.J.M., 1993. Gamma-ray spectroscopy of voluminous sources. Corrections for source geometry and self-attenuation. Nucl. Instrum. Methods A324, 209-218. 

The question of improving fire-resistance of aromatic polyesters is paid more attention last time. Polymeric materials can be classified on criterion of combustibility noncombustible, hard-to-bum and combustible. Aromatic polyesters enter the combustible group of polymers self-attenuating when taken out of fire. 

The most acceptable ways of modification of aromatic polyesters aimed to get self-attenuating materials of improved resistance to aggressive media are the condensation of polymers from halogen-containing monomers. 

The articles from polysulfone possess self-attenuating properties, caused by the nature of polymer but not of the additives. The values of oxygen index for polysulfone lie in the range of 34-38%. Apparently, aromatic polysulfones damp down owing to the formation of carbonized layer, becoming porous protective cover, on their surfaces. The probable is the explanation according to which the inert gas is released from the polymer [8]. 

XPS is surface-sensitive due to the mean free path A of the photoelectrons within a specimen which is in the range of several nanometers. Their inelastic losses lead to an exponential attenuation of the signal with depth. Thus only those electrons that originate at a depth not larger then 3 A may contribute to the signal. The intensity 7 of a component i with a particle concentration AT of a thin layer follows Eq. (1-45) with an exponential self attenuating factor which approaches 1 for a large thicknesses. ... 

Figure 2 Self attenuation of Pb gamma emission by lead-rich gas pipe dust...

Hi. Sensitivity. Sensitivity in PET is defined as the capability of detecting the true coincidences (solid line. Fig. 11) with a given amount of radioactivity. Sensitivity has traditionally been measured with a phantom of diameter d = 20 cm, filled with a uniform activity concentration p (/u.Ci/cm ) (1/LrCi = 37,000 disintegrations per second). By considering several factors, including the activity in the field of view, the self-attenuation of y rays within the phantom, the solid angle subtended by the detector array, and the detection efficiency of the array, an empirical formula for sensitivity measure is derived and given by... 

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