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PHYS01200804001 Sohrab Abbas - Homi Bhabha National Institute

PHYS01200804001 Sohrab Abbas - Homi Bhabha National Institute

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Fig.40 1 st sub-arcsec neutron collimation: observed (data points) and calculated (curve) rocking<br />

curves (cf. inset) for prism diffractions of the monochromator (A=172 o and θ S =50.1 o ) and the<br />

optimal analyser.<br />

agreement with the theoretical prediction (smooth curve), with a peak of ~ 10.1 neutrons/s. This is<br />

the best instrumental resolution recorded to date. The monochromator prism diffraction peaks are<br />

about 4 times as narrow as the monochromator Bragg reflection rocking curve, both being recorded<br />

by the analyser prism diffraction, albeit having 6.5 times as weak peak intensity. In comparison<br />

with the Bragg-Bragg curve on the other hand, they are 5 times as narrow, but with about 46.3<br />

times as weak peak intensity. The deconvolution of the observed rocking curve from the analyser<br />

acceptance curve yields an FWHM ~ 0.58 arcsec for the beam delivered by the monochromator.<br />

This constitutes the tightest neutron collimation attained to date [152].<br />

77

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