First evaluation of gamma-ray emission from alpha-boron reactions in the ITER tokamak with a tungsten wall

Abstract Following the change of the first wall material from beryllium to tungsten at ITER, α -particle measurements by gamma-ray spectroscopy based on beryllium as the target of the reaction are no longer viable. An alternative is to exploit reactions based on boron as the target, such as 10 B( α,pγ ) 13 C . In this work we provide a first estimate of the signal from the 10 B( α,pγ ) 13 C reaction expected at each detector of the Radial Gamma-Ray Spectrometers system and the predicted background levels. The calculation method makes use of the ITER scenarios available via the IMAS database, the reaction cross sections and the MCNP code to extract parameters relevant to estimate the background at the detectors. We find that α -particle measurements via the 10 B( α,pγ ) 13 C reaction with 100 ms time resolution, as required for ITER, are not feasible in the 537 MW full fusion power scenario with the present RGRS configuration, because of the neutron-induced background and the resulting detector-rate limitations; measurements with a few-second time resolution may instead be achievable in lower-power scenarios (up to 50 MW) with 10 B concentrations of ∼1% or higher. α -particle measurements would be furthermore possible in D 3 He plasmas optimized for α -particle generation, without limitations on the fusion power that may be achieved in those scenarios; however, these scenarios are not presently considered in ITER's research plan.