Validation of the response function of the WENDI-2 detector with high-energy quasi-monoenergetic neutron beams for proton therapy centers

May 18, 2016, 2:45 PM
8h 15m





In proton therapy, proton beams with energies up to typically 230 MeV are used to treat cancerous tumours very efficiently while sparing surrounding healthy tissues as much as possible. Due to nuclear interactions of the proton beams with matter, mainly inside the cyclotron, the beam line, the treatment nozzle and the patient, secondary neutrons with energies up to 230 MeV are unfortunately produced, as well as photons up to ~10 MeV. In shielding studies for proton therapy facilities, the neutron total ambient dose equivalent H(10) component is often evaluated using the Monte Carlo codes MCNPX or FLUKA. Recent benchmark simulations performed with GEANT4 have shown that this code would also be a suitable tool for the shielding studies of proton therapy centres. The experimental validation of such shielding studies requires the use of a detector with a good sensitivity for neutrons ranging from thermal energies up to 230 MeV, such as for example the extended-range neutron rem meter WENDI-2, developed in the 1990s by R.H. Olsher and nowadays commercialized by Thermo Scientific. Although the response function of the WENDI-2 detector is not ideal, it is rather well-balanced with respect to the ICRP74 fluence-to-H(10) conversion function. However to have an accurate H*(10) measurement, the WENDI-2 detector response function needs to be validated with quasi-monoenergetic neutron beams at high energies. This paper presents the measurements performed with a WENDI-2 detector in high-energy quasi-monoenergetic neutron beams at the Theodor Svedberg Laboratory (Uppsala, Sweden). The results are compared to similar measurements of Olsher et al. as well as to MCNPX and GEANT4 simulations.

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