Antiproton annihilation physics annihilation physics in the Monte Carlo particle transport code particle transport code SHIELD-HIT12A

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  • Vicki Trier Taasti
  • Helge Knudsen
  • Michael Holzscheiter, Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA
  • Nikolai Sobolevsky, Department of Neutron Research, Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia, Rusland
  • Bjarne Thomsen, Danmark
  • Niels Bassler
The Monte Carlo particle transport code SHIELD-HIT12A is designed to simulate therapeutic beams for cancer radiotherapy with fast ions. SHIELD-HIT12A allows creation of antiproton beam kernels for the treatment planning system TRiP98, but first it must be benchmarked against experimental data. An experimental depth dose curve obtained by the AD-4/ACE collaboration was compared with an earlier version of SHIELD-HIT, but since then inelastic annihilation cross sections for antiprotons have been updated and a more detailed geometric model of the AD-4/ACE experiment was applied.

Furthermore, the Fermi–Teller Z-law, which is implemented by default in SHIELD-HIT12A has been shown not to be a good approximation for the capture probability of negative projectiles by nuclei. We investigate other theories which have been developed, and give a better agreement with experimental findings. The consequence of these updates is tested by comparing simulated data with the antiproton depth dose curve in water.

It is found that the implementation of these new capture probabilities results in an overestimation of the depth dose curve in the Bragg peak. This can be mitigated by scaling the antiproton collision cross sections, which restores the agreement, but some small deviations still remain.

Best agreement is achieved by using the most recent antiproton collision cross sections and the Fermi–Teller Z-law, even if experimental data conclude that the Z-law is inadequately describing annihilation on compounds. We conclude that more experimental cross section data are needed in the lower energy range in order to resolve this contradiction, ideally combined with more rigorous models for annihilation on compounds.
TidsskriftNuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Sider (fra-til)65-71
Antal sider7
StatusUdgivet - 15 mar. 2015


  • antiprotoner, partikelterapi, tværsnit

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