Pion Production Data needed for Space Radiation

Abstract

A recent discovery concerning the importance of hadron production in space radiation is that pions can contribute up to twenty percent of the dose from galactic cosmic ray interactions (S. Aghara, S. Blattnig, J. Norbury, R. Singleterry, Nuclear Instruments and Methods, Vol. 267, 2009Vol. 267, , p. 1115. Although the contribution for dose equivalent will be smaller, the dose contribution could be important for fluence based radiation models. Pion production cross sections will be an essential ingredient to such models, and it is of interest to investigate the adequacy of the pion production experimental data base for energies relevant to space radiation. The pion production threshold in nucleon -nucleon reactions is at 280 MeV and, in an interesting accident of nature, this lies near the peak of the galactic cosmic ray proton spectrum. Therefore, pion production data are needed from threshold up to energies around 50 GeV/nucleon, where the galactic cosmic ray fluence is of decreasing importance. Total and differential cross section data for pion production in this energy range will be reviewed. The availability and accuracy of theoretical models will also be discussed. It will be shown that there are a significant lack of data in this important energy range and that theoretical models still need improvement.

MCNPX simulation of proton dose distributions in a water phantom

“…Although it was simulated, the pion contributed no fluence for proton secondary particles in the therapeutic energy range because the pion production threshold in nucleon-nucleon reactions is at 280 MeV. [20] Figure 3 shows the energy deposition curves of different particles obtained from MCNPX for 160 MeV protons in a water phantom. Although the fluences of neutrons and photons were only one order smaller than that of protons, their contributed dose was about 0.1-1% of the proton dose.…”