Shielding of relativistic protons
Artikel i vetenskaplig tidskrift, 2007

Protons are the most abundant element in the galactic cosmic radiation, and the energy spectrum peaks around 1 GeV. Shielding of relativistic protons is therefore a key problem in the radiation protection strategy of crewmembers involved in long-term missions in deep space. Hydrogen ions were accelerated up to 1 GeV at the NASA Space Radiation Laboratory, Brookhaven National Laboratory, New York. The proton beam was also shielded with thick ( about 20 g/cm(2)) blocks of lucite (PMMA) or aluminium ( Al). We found that the dose rate was increased 40-60% by the shielding and decreased as a function of the distance along the axis. Simulations using the General Purpose Particle and Heavy-Ion Transport code System (PHITS) show that the dose increase is mostly caused by secondary protons emitted by the target. The modified radiation Weld after the shield has been characterized for its biological eVectiveness by measuring chromosomal aberrations in human peripheral blood lymphocytes exposed just behind the shield block, or to the direct beam, in the dose range 0.53 Gy. Notwithstanding the increased dose per incident proton, the fraction of aberrant cells at the same dose in the sample position was not significantly modified by the shield. The PHITS code simulations show that, albeit secondary protons are slower than incident nuclei, the LET spectrum is still contained in the low-LET range (< 10 keV/mu m), which explains the approximately unitary value measured for the relative biological effectiveness.

RISK

ABERRATIONS

HUMAN-LYMPHOCYTES

ENERGY IRON IONS

Författare

Antonella Bertucci

Universita degli Studi di Napoli Federico II

Marco Durante

Universita degli Studi di Napoli Federico II

Giancarlo Gialanella

Universita degli Studi di Napoli Federico II

Gianfranco Grossi

Universita degli Studi di Napoli Federico II

Lorenzo Manti

Universita degli Studi di Napoli Federico II

Mariagabriella Pugliese

Universita degli Studi di Napoli Federico II

Paola Scampoli

Universita degli Studi di Napoli Federico II

Davide Mancusi

Chalmers, Teknisk fysik, Nukleär teknik

Lembit Sihver

Chalmers, Teknisk fysik, Nukleär teknik

Adam Rusek

Brookhaven National Laboratory

Radiation and Environmental Biophysics

0301-634X (ISSN) 1432-2099 (eISSN)

Vol. 46 2 107-111

Ämneskategorier

Annan teknik

DOI

10.1007/s00411-006-0088-6