Figure 9
The changes in I/D (including detector quantum efficiency), normalized to the value at 12.4 keV, as a function of beam energy for cubic crystals of different sizes of (a) 1 µm, (b) 2 µm and (c) 5 µm (specified lengths are of one crystal dimension). The dose is calculated using Monte Carlo simulations including the probability of photoelectron escape from the crystal and also photoelectron entry from the surrounding material. I is calculated from equations (2) and (3). All heavy atoms (Z > 8) have been removed from the crystal and the surroundings to prevent absorption edges obscuring the results. For all crystal sizes the beam is matched to the size of the crystal, so the irradiated surrounding material in the beam path is in front and behind the crystal. The detector quantum efficiencies used are for the detector with the highest values for that Einc. This is 450 µm silicon for Einc ≤ 9.3 keV, 1000 µm for 9.3 keV < Einc ≤ 20 keV, and 750 µm CdTe for Einc > 20 keV. |