Neutron scattering disadvantages

These disadvantages are overcome by the so-called dance-floor principle which is supposed to become the major beamline construction principle of the future. Figure 4.11 shows a dance floor during the construction of the beamline hall at the ANSTO neutron-scattering facility at Lucas Heights near Sydney, Australia. The dance floor is featuring an extremely plane and hard floor surface from granite. Optical components, detectors and sample chambers are mounted on supports with a flat lower surface. While compressed air is blown into the gap between the dance floor and the area of support, components are easily moved and adjusted in the optical beam path. 

Both small angle X-ray (SAXS) cind neutron scattering (SANS) are established techniques and their experimental application is similar. However, limitations on sample size, thickness and containment are much more restricted with X-rays because of absorption of radiation. One problem which can arise with neutrons is the subtraction of the flat incoherent contribution which can be quite large in the case of hydrogenous materials. This disadvantage can be partially offset by the possibility of using isotopic substitution. SANS is particularly powerful because the penetrating power of neutrons makes it possible to study material microstructure in the wet state. Instrumentally, both SAXS and SANS require a source of radiation, collimation system, sample containment and a detection system. 

It was stated in the previous section that usually neutron scattering is used to investigate polymer-polymer interfaces with however the disadvantage of the limited 2-range. If a large -range is required x-rays have to be used. But it turns out that... 

Neutron beams differ from both of these alternatives in that the neutron has no charge and generates no measurable electric field, so the neutron beam is usually not greatly affected by the electron distribution in the sample. Instead, the neutrons are scattered principally by the atomic nuclei. Like x-rays, the neutrons penetrate the interior of the sample. In fact, one of the disadvantages of neutron scattering is that the interaction with the sample is often much weaker than with x-rays, since much of the neutron beam passes through the sample without being scattered at all. 

A particularly serious disadvantage when performing neutron experiments on Eu, Sm, Gd, Np, and Pu compounds is the high absorption of the most abundant isotopes for thermal neutron scattering. The capture cross section, tr p, arises when neutrons are captured by the nucleus, which subsequently emits y-rays. Because of resonance... 

Orientational order in liquid crystals is most effectively studied using molecular probe techniques such as NMR spectroscopy. However, the study of translational order, that is structure, requires diffraction techniques, usually involving X-rays or neutrons. A disadvantage of diffraction is that it does not distinguish between static and dynamic disorder. However, this can be achieved using quasielastic neutron scattering. 

Although, neutron scattering has numerous advantages, it includes some handicaps. The disadvantages of neutron scattering can be summarized as follows ... 

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