Novel experimental approach to uncover the nature of cosmic-ray deuterium

Studying the isotopic composition of cosmic ray (CR) provides crucial insights into the galactic environment and helps improve existing propagation models. Special attention is given to the secondary-to-primary ratios of light isotopic components in CR, as these measurements can offer complementary data compared to traditional secondary-to-primary ratios like $\mathrm{B}/\mathrm{C}$. Recently, a precision measurement of the deuterium (D) abundance in CR in the 2--21 GV rigidity range provided by the AMS02 experiment unexpectedly detected an excess of D with respect to its expected secondary nature, opening the field for new measurements at high rigidity to determine how the spectrum evolves and whether there is confirmation of a primary or primary plus secondary origin. While there are theoretical models that attempt to explain this excess, the experimental uncertainties on D production cross sections and on CR propagation models remain significant, and only new and precise measurements can dissipate existing doubts. In this work, we review the current experimental scenario, and we propose a dedicated experiment that is able to extend the D abundance measurement up to $100\text{ }\text{ }\mathrm{GeV}/\mathrm{nucl}$ without the need of a magnetic spectrometer, using a multiple-scattering-based technique for the measurement of particle momentum. The expected performance of the proposed detector is assessed through a dedicated simulation using the geant4 package, and its role in the current particle physics scenario is discussed.