Radiation measurements in the International Space Station, Columbus module, in 2020-2022 with the LIDAL detector.

The Light Ion Detector for ALTEA (LIDAL) is a new instrument designed to measure flux, energy spectra and Time of Flight of ions in a space habitat. It was installed in the International Space Station (Columbus) on January 19, 2020 and it is still operating. This paper presents the results of LIDAL measurements in the first 17 months of operation (01/2020-05/2022). Particle flux, dose rate, Time of Flight and spectra are presented and studied in the three ISS orthogonal directions and in the different geomagnetic regions (high latitude, low latitude, and South Atlantic Anomaly, SAA). The results are consistent with previous measurements. Dose rates range between 1.8 nGy/s and 2.4 nGy/s, flux between 0.21 particles/(sr cm2 s) and 0.32 particles/(sr cm2 s) as measured across time and directions during the full orbit. These data offer insights concerning the radiation measurements in the ISS and demonstrate the capabilities of LIDAL as a unique tool for the measurement of space radiation in space habitats, also providing novel information relevant to assess radiation risks for astronauts.

A novel algorithm for the calculation of physical and biological irradiation quantities in scanned ion beam therapy: the beamlet superposition approach.

The calculation algorithm of a modern treatment planning system for ion-beam radiotherapy should ideally be able to deal with different ion species (e.g. protons and carbon ions), to provide relative biological effectiveness (RBE) evaluations and to describe different beam lines. In this work we propose a new approach for ion irradiation outcomes computations, the beamlet superposition (BS) model, which satisfies these requirements. This model applies and extends the concepts of previous fluence-weighted pencil-beam algorithms to quantities of radiobiological interest other than dose, i.e. RBE- and LET-related quantities. It describes an ion beam through a beam-line specific, weighted superposition of universal beamlets. The universal physical and radiobiological irradiation effect of the beamlets on a representative set of water-like tissues is evaluated once, coupling the per-track information derived from FLUKA Monte Carlo simulations with the radiobiological effectiveness provided by the microdosimetric kinetic model and the local effect model. Thanks to an extension of the superposition concept, the beamlet irradiation action superposition is applicable for the evaluation of dose, RBE and LET distributions. The weight function for the beamlets superposition is derived from the beam phase space density at the patient entrance. A general beam model commissioning procedure is proposed, which has successfully been tested on the CNAO beam line. The BS model provides the evaluation of different irradiation quantities for different ions, the adaptability permitted by weight functions and the evaluation speed of analitical approaches. Benchmarking plans in simple geometries and clinical plans are shown to demonstrate the model capabilities.

Carbon fragmentation measurements and validation of the Geant4 nuclear reaction models for hadrontherapy.

Nuclear fragmentation measurements are necessary when using heavy-ion beams in hadrontherapy to predict the effects of the ion nuclear interactions within the human body. Moreover, they are also fundamental to validate and improve the Monte Carlo codes for their use in planning tumor treatments. Nowadays, a very limited set of carbon fragmentation cross sections are being measured, and in particular, to our knowledge, no double-differential fragmentation cross sections at intermediate energies are available in the literature. In this work, we have measured the double-differential cross sections and the angular distributions of the secondary fragments produced in the (12)C fragmentation at 62 A MeV on a thin carbon target. The experimental data have been used to benchmark the prediction capability of the Geant4 Monte Carlo code at intermediate energies, where it was never tested before. In particular, we have compared the experimental data with the predictions of two Geant4 nuclear reaction models: the Binary Light Ions Cascade and the Quantum Molecular Dynamic. From the comparison, it has been observed that the Binary Light Ions Cascade approximates the angular distributions of the fragment production cross sections better than the Quantum Molecular Dynamic model. However, the discrepancies observed between the experimental data and the Monte Carlo simulations lead to the conclusion that the prediction capability of both models needs to be improved at intermediate energies.