Composition of the theoretical reflectivity curve for a Si(660) analyser with 86 mm diameter. (a) Distribution of the shift of the reflected photon energy given by equation (42). (b) Reflectivity for a spherically bent crystal without angular compression computed from Takagi–Taupin equations. (c) Simulated bandwidth curve of the incoming radiation, which in this case has a FWHM of 235 meV. (d) Convolution of the preceding curves. Note that the energy scale in (d) is different from the other graphs.