PHYS01200804001 Sohrab Abbas - Homi Bhabha National Institute

currently available, the interference pattern is analysed with an ‘analyser’ crystal by monitoring the
intensity of waves emanating from it. The numerous configurations like BB, LL, BBB, LBBL and
LLL, have been tested and operated since last 37 years [1,4,86-88,121-130]. Here the letters L and
B stand for Laue and Bragg cases respectively. Though each configuration has its own merits and
demerits, the LLL symmetric IFM, due primarily to its versatility and size, has been employed in
our experiment (Chapter 5). Large neutron IFM inevitably permits larger path separations between
the coherent wave amplitudes allowing high precision studies of materials properties e.g., neutron
coherent scattering length determination.
In the configuration represented in Fig.7, the contributions of waves in the paths I and II to the O
and H waves emanating from the analyser slab can, by a repetitive application of Eqs.(38a-38b), be
Fig.7 Operating principle of a symmetric LLL IFM.
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