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Neutrons for Science
1013
1012
1010
109
108
100 Å
Spectrum of the
thermal neutron flux 1011 corresponding to:
1010
1
10
the heavy water the hot source the cold source
Fig. 5.10: Neutron flux from a normal tangential tube (curve 1), the hot source (curve 2), and the cold source (curve 3) as a function of wavelength. The appreciable gains in flux at short wavelengths are seen for the hot source, and the converse for the cold source..
accident82 in 1961 by Peter Höhne and Tasso Springer in Munich, and then developed by Maier-Leibnitz and Tasso Springer. Total internal reflection of neutrons occurs with neutrons, as with light. When there is an interface between a vacuum and a medium which has a refractive index n less than unity there is total reflection of neutrons when the grazing angle of incidence is less
82 During an experiment at Munich a neutron beam was left unprotected over several metres. To avoid people crossing the beam a brass tube was placed around the beam. This led to a great increase in neutron intensity at the far end of the tube. This greatly surprised the scientists, with the exception of Peter Höhne, who was prepar- ing his thesis with Tasso Springer, and had deliberately chosen a brass tube. I learnt this from Peter Armbruster who was also a thesis student (see “Maier-Leibnitz and Neutron Optics”, T. Springer and A. Heidemann, 2002, Neutron News 13, 1, DOI 10.1080/10448630208222873). The exploitation of this phenomenon is due to Tasso Springer and Maier-Leibnitz.
121
neutrons /cm2/s/sr