SAIP2026

Modelling and validation of neutron detector response functions up to 140 MeV using Geant4

7 Jul 2026, 09:30

20m

Lecture Hall GH2 (University of the Western Cape)

Oral Presentation Track B - Nuclear, Particle and Radiation Physics Nuclear, Particle and Radiation Physics -1

Speaker

Mr Miles Kidson (University of Cape Town)

Description

Cosmic radiation, composed of Galactic Cosmic Rays, Solar Energetic Particles, and their associated secondary particles, represents a recognized radiation risk to space missions, satellites, and air travel. Secondary neutrons, with characteristic spectral features in the MeV and 100 MeV range [1,2], are produced by cosmic ray interactions with atmospheric and spacecraft materials [3]. A compact spectrometry system based on plastic scintillators, silicon photomultipliers, and spectrum unfolding is under development for use at aviation altitudes and in space. Reliable spectrum measurements with the device require well-characterised detector response functions across the full energy range of interest. While these can be simulated below 20 MeV, higher energies typically require experimental validation due to known limitations in nuclear models and data.

We present progress towards characterising a prototype high-energy spectrometer presently under development for dosimetry of secondary neutrons and gamma rays produced by cosmic rays. Below 20 MeV, two simulation techniques are validated against measured response functions: the standard Geant4 scintillation package; and a direct conversion between deposited energy and light output. In this energy range, Geant4 uses a data-driven approach, but above 20 MeV it relies on models with limited supporting measurements. We also assess the validity of extending this approach to higher energies using quasi-monoenergetic neutron response functions between 30–140 MeV measured at iThemba LABS, a high-energy neutron facility in Cape Town [4]. By supplementing measured detector response functions with validated simulated data, the energy resolution of unfolded neutron spectra can be improved where access to reference neutron facilities is limited.

[1] P. Goldhagen, J. Clem, J. Wilson, Radiat. Prot. Dosim. 110 (2004) 387.
[2] M.B. Smith et al., Radiat. Prot. Dosim. 168 (2015) 154–166.
[3] K. Copeland, Radiat. Prot. Dosim. 175 (2017) 419.
[4] M. Mosconi et al., Radiat. Meas. 45 (2010) 1342–1345.

Presentation materials

88_Miles_Kidson.pdf