Figure 5
(a) Integrated number of photons as a function of knife-edge position (slit system) at a photon energy of E = 13.6 keV (40-bunch mode) on a semi-logarithmic scale. Two different primary X-ray intensities (I ≃ 5 × 108 photons s−1 and I ≃ 1.6 × 103 photons s−1) have been applied for the measurements presented in the inset; the intrinsic linearity of the QAPD manifests is validated from the perfect overlay of the resulting scans. (b) Autocorrelation coefficient of the pulse-wise sampled intensity waveform I(t). The peak at τ = 0 is omitted. Two characteristic and prominent oscillations at f1 ≃ 35Hz and f2 ≃ 245 Hz are observed and can be attributed to mechanical vibrations of the monochromator crystals induced by the cryogenic pumping. |