Neutron shadowing

CPs are slowed down in matter and are all stopped at depth, called the range, being 0.1 to 1 mm. As a consequence the beam intensity is hardly reduced, in contrast to neutron shadowing. Moreover, the induced activity is not related to the mass of the analyte, but to its mass fraction. So standardization (calibration) is very different from NAA. 

Fig. 1.3 Relaxation map of polyisoprene results from dielectric spectroscopy (inverse of maximum loss frequency/w// symbols), rheological shift factors (solid line) [7], and neutron scattering pair correlation ((r(Q=1.44 A )) empty square) [8] and self correlation ((t(Q=0.88 A" )) empty circle) [9],methyl group rotation (empty triangle) [10]. The shadowed area indicates the time scales corresponding to the so-called fast dynamics [11]...

Self-shadowing and resonance capture effects. The use of small samples and standards so that the neutron flux is not appreciably attenuated between the exterior and interior of the irradiation unit is to be desired. When large samples are used or appreciable high cross section material is present in the matrix, it is important that the standard be prepared with a matrix physically and chemically similar to that of the sample. 

The majority of the analytical techniques used for determining elements in cosmetic samples require the dissolution and dilution of samples in an appropriate solvent, with some exceptions such as X-ray fluorescence spectrometry or neutron activation analysis (NAA) which allow, in the case of solid samples, direct measurement. For example, iron and zinc have been determined in compact eye-shadow, face-powder, and rouge by NAA without prior treatment of samples. 

Rod shadow Is an effect in which the repositioning of one control rod changes the reactivity worth of adjacent rods or causes a change in power level indication on neutron detectors when power level has remained constant. Rod shadow is caused by flux redistributions within the core as a result of rod motion. 

Figure 7.6 Rod Shadow Between Control Rods and a Neutron Detector...

The reactor is a helium/xenon (Me/Xe) gas-cooled, fast neutron spectrum, fission reactor with an approximately 1 MWt uranium heat source directly coupled to a gas Brayton energy conversion equipment The reactor requires a radiation shield to provide a shadow volume of diminished radiation to the rest of the Spaceship. The radiation shield concept is an elliptical cone which produces this shadow with half-angles of 12" and 6°, All major elements of the spacecraift and Mission Modules will be located within this shielded area... 

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