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Figure 7
Schematic drawings of the precession path through the two different configurations for two different neutron trajectories. The rS direction is taken along the y direction (perpendicular to the paper). We consider only the trajectory for αS4 = 0 or π, which means that all ri are in the x direction. (a) In the (++, ++) configuration the path lengths through the first and second precession regions are only equal for trajectories going exactly through the centre of the setup, as illustrated for the lower trajectory. In the higher trajectory the path length through the first precession region becomes shorter, while it becomes longer for the second region, as reflected in equation (23)[link]. (b) In the (+−, −+) configuration the exact value of rS has no effect on the echo. For a certain angle of the trajectory it does not matter if the neutron path is higher or lower, as long as the x components of the radii in the shifters change sign from the first precession region with respect to the second precession region, as reflected in equation (24)[link].

Journal logoJOURNAL OF
APPLIED
CRYSTALLOGRAPHY
ISSN: 1600-5767
Volume 55| Part 5| October 2022| Pages 1072-1084
https://doi.org/10.1107/S1600576722007245
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