Figure 2
Radiation dose modelling. (a) Pixel-based numerical modelling of the sample-absorbed dose under conventional flow conditions at a flux of 5 × 1012 photons s−1. Note that the absorbed dose in the longitudinal (i.e. along the beam) direction is dominated by flow-field effects, while the absorbed dose in the lateral (i.e. perpendicular to the beam) direction is dominated by the Gaussian beam profile. The absorbed dose varies by several orders of magnitude from the front to the middle of the capillary, reflecting the increased time in the beam for material in the low-flow regions. (b) Calculated sample-absorbed radiation dose in the coflow measurement, using a total flow of 1.0 µl s−1 and a fractional sample-flow rate (FSFR) of 0.33 at 5 × 1012 photons s−1, indicating a much more uniform and lower absorbed dose restricted to the central portion of the capillary. The arrows indicate the beam direction. |