Light-scattering detectors elastic

The foundation for the development of these techniques is built on investigations into photon migration processes [2, 9]. Subsequent, detailed examination by Everall et al. [10, 11] demonstrated that the inelastically scattered (Raman) component decays substantially more slowly than its elastically scattered counterpart (i.e. the laser light) due to the regeneration of the Raman signal from the laser component. Discrimination between diffusely scattered photons and the ballistic and snake components is achieved by gating the detector in the temporal or spatial domain. 

Because RBS is rather insensitive to light elements and unable to detect hydrogen, one can make use of the complementary technique Elastic Recoil Detection (ERD) when sensitivity for light elements is required. In this case, recoiled particles are detected instead of the back scattered particles. The incident beam usually consists of heavier ions, e.g. 2 Si (4He is sufficient when one is interested in H and D only), and a stopper foil prevents backscattered particles from entering the detector, whereas the lighter recoiled particles are transmitted [32]. 

The most recent measurements of this kind are those of Walt and Beyster. These authors used a collimated beam of 4.1 Mev neutrons produced in the H (i, n) He reaction and measured the elastic scattering of the neutrons produced from targets placed in the neutron beam. Their detector consisted of a number of spherical plastic scintillators separated from each other by quartz plates and placed at the end of a light guide. This method of detection, first described by McCrary, Taylor, and Bonner, by limiting the size of each detecting unit,... 

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