Study of the neutron dose equivalent at the HIRFL deep tumor therapy terminal

TL;DR

This study measures and simulates neutron dose equivalents at a heavy ion therapy facility, showing that neutron doses from fragmentation are negligible, aiding radiation protection and shielding design.

Contribution

It provides experimental measurements and FLUKA simulations of neutron dose equivalents in deep tumor therapy, confirming the negligible impact of fragmentation neutrons.

Findings

Neutron dose from fragmentation reactions is negligible.

Experimental data agrees well with FLUKA simulations.

Results inform radiation protection and shielding design.

Abstract

The secondary neutron fields at the deep tumor therapy terminal at HIRFL (Heavy Ion Research Facility in Lanzhou) were investigated. The distributions of neutron ambient dose equivalent were measured with a FHT762 Wendi-II neutron ambient dose equivalent meter as the 12C ions with energies of 165, 207, 270, and 350 MeV/u bombarded on thick tissue-like targets. The thickness of targets used in experiments is larger than the range of the carbon ions. The neutron spectra and dose equivalent is simulated by using FLUKA code, and the results agree well with the experimental data. The experiment results showed that the neutron dose produced by fragmentation reactions in tissue can be neglected in carbon-ion therapy, even considering their enhanced biological effectiveness. These results are also valuable for radiation protection, especially in the shielding design of high energy heavy ion medical machines.