Energy deposition in spherical cells from direct and indirect particle hits Ianik Plante1, Floriane Poignant2, Tony C. Slaba3 1KBR, 2400 NASA Parkway, Houston 77058 2National Institute of Aerospace, Hampton, VA 23681 3NASA Langley Research
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Energy deposition in spherical cells from direct and indirect particle hits Ianik Plante1, Floriane Poignant2, Tony C. Slaba3 1KBR, 2400 NASA Parkway, Houston 77058
2National Institute of Aerospace, Hampton, VA 23681
3NASA Langley Research Center, Hampton, VA 23681 NASA Human Research Program Investigators’ Workshop
February 1-2, 2021<br>
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Energy deposition in micrometric targets: simulation set-up Wall-less spherical water targets are used.
Targets are encompassed in the irradiated volume.
The tracks are classified as direct for those which the axis intercepts the target, and indirect for those that do not.
Periodic boundary conditions (PBCs) can be used to mimic delta electrons originating from tracks in neighboring and distant volumes.
Electrons put back in the volume after leaving it are considered indirect hits in all cases, and originating from a different track.
The energy deposited in the target is calculated for each individual track.<br>
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RITRACKS: simulation of volume irradiation Plante I, Cucinotta, F.A. Monte-Carlo Simulation of Ionizing Radiation Tracks. In: Mode, C.J. (Ed.) Applications of Monte Carlo Methods in Biology, Medicine and Other Fields of Science. InTech, Rijeka, Croatia.<br>
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Energy deposition in micrometric targets: results The direct contribution is identical in all cases, regardless of the size of the irradiation volume or presence or absence of PBCs.
The indirect contribution depends on the size of the irradiated volume, and appears to converge to the indirect value given by PBCs.
The total dose is as expected with PBCs, but systematically smaller than expected without PBCs. This is because energetic electrons from distant volume are not taken into account in the simulation, but can reach the target due to their very long range (in the order of mm).<br>
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Energy deposition in micrometric targets: results The direct spectra scale roughly by the target radius and the LET (energy axis) and LET2 (frequency axis).
The indirect spectra scales roughly by the target radius.
Essentially, this work has shown that two different modes of energy deposition (direct and indirect) exist when analyzing the energy deposition spectra in spherical targets.
More on this on the poster “Impact of Radiation quality on microdosimetry calculation” by F. Poignant. Energy deposition per track normalized to the incident dose for different ions and target radii (1 µm, 2 µm, 4 µm and 8 µm). Solid line: direct contributions. Dash line: indirect contributions. Dot line: total contributions. Energy deposition per track normalized to the incident dose, target radii and LET for different ions and target radii (1 µm, 2 µm, 4 µm and 8 µm). Direct contributions. Energy deposition per track normalized to the incident dose and target radii and LET for different ions and target radii (1 µm, 2 µm, 4 µm and 8 µm). Indirect contributions.<br>
