Deuterium Dynamic Retention and Surface Contamination in ZrDx under Dn+ Bombardment studied by 3He+ NRA and ToF-ERDA

Deuterium (D) and tritium (T) retention in ZrDₓ/ ZrTₓ targets are critical for the stability and lifetime of D-D/D+T neutron generators. Here, D dynamic retention and near-surface contamination in ~2 μm ZrDₓ films on Si substrate were investigated during Dₙ⁺ bombardment using in situ ³He⁺ nuclear reaction analysis (NRA) and complementary time of flight elastic recoil detection (ToF-ERDA) depth profiling. The films were bombarded with 20–30 keV/u D_n⁺ beams and D concentration was monitored by ³He NRA at the University of Lisbon. For a fresh sample, the D concentration first increased by ~10% and then rapidly returned to its initial level in low fluence below 1 × 10¹⁶ D cm⁻². After an overnight interruption, the concentration decreased further, but increased again and reached a new saturation level when re-bombarding. Repeated measurements during 2025–2026 showed that the D concentration variation remained within ~10% under the present conditions. However, a carbon-rich contamination layer was formed by large fluence bombardment under limited vacuum condition. The depth profiles of D, C, and Zr were therefore measured by ToF-ERDA 14.5 MeV ¹²⁷I⁷⁺ ions at the University of Surrey. Comparative depth profiles from the unirradiated region, peripheral zone, and beam-spot center showed strong dependence of the near-surface ²H/Zr ratio on irradiation and ageing history (Fig.1). The aged irradiated region exhibited pronounced D depletion, suggesting that irradiation-induced damage and post-irradiation ageing can promote D release. These results demonstrate that D retention in ZrDₓ is governed not only by implantation-induced D uptake and release, but also by surface contamination and sample history. The growth of a carbon-rich surface layer may modify near-surface D transport and retention, which is directly relevant to the reliability and lifetime assessment of ZrDₓ targets in neutron-generator applications.