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. 2012 Feb 2;117:61–79. doi: 10.6028/jres.117.002

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Fig. 3 — (Top) Monitor count rate versus energy for the PG(002) monochromator, using double focusing (red), compared with the monochromator flat horizontally and (variable) vertical focusing (green), and with vertical focusing and collimation of open-50 before and after the monochromator. Note that the primary gain in the intensity with double-focusing is the removal of the Söller collimation; then the advantage of using energy focusing is the improvement of the energy resolution. For comparison, the monitor rate for the old BT-2 TAS spectrometer (yellow) has been scaled by the measured flux at 14.7 meV (where the fixed vertical focus was optimized for BT-2); BT-9 had a similar flux. BT-7 provides more neutrons that also fully illuminate the sample over a wider range of incident energies, while the double focusing mode is seen to provide a dramatic gain in neutron intensity by relaxing the wave vector resolution of the instrument. (Bottom) Monitor rate using the Cu(220) monochromator system for various conditions as indicated. Neutron energies above 500 meV are available, but of course the flux drops off quickly at such high energies as shown in the inset.