Speaker
Description
Following the end of the operations of the Joint European Torus (JET) and the recent development of a new baseline for ITER, future tokamaks will be based on a high Z first wall material and will no longer use beryllium. New developments in fast ion generation scenarios and neutron and gamma-ray diagnostics are necessary to provide both the instruments and the knowledge base required in preparation of experiments at these devices. In this contribution, we present the first numerical and experimental results of a mid-term program aimed at advancing fast-ion scenarios for α particle generation and the related diagnostics, mostly in view of JT-60SA and ITER operations.
On the experimental side, scenarios for α particle production based on the 3He(d,p)α or the 11B(p,α)2α reactions are being designed and first exploratory tests have been made at the ASDEX Upgrade tokamak. To this end, we have developed a new compact neutron spectrometer, named COSMONAUT+, based on a LaCl3(Ce) scintillator. The instrument has successfully measured, for the first time at ASDEX Upgrade, the neutron spectrum from the acceleration of fast deuterium ions by third harmonic radio-frequency heating. This is a necessary step to demonstrate the generation of α particles from D+3He fusion in forthcoming experiments in D-3He plasmas. A gamma-ray spectrometer has also been installed to enable gamma-ray emission measurements from fast-ion reactions without beryllium in next step experiments.
On the numerical side, we have evaluated the velocity-space and orbit-space sensitivity of boron-based gamma-ray spectroscopy using the 10B(α, pγ)13C reaction, which is one of the options for α particle measurements in tungsten first wall devices with boron injection. Despite a lower signal when compared with the 9Be(α, nγ)12C reaction used at JET, the three emission peaks of 10B(α, pγ)13C offer a selective sensitivity to super- and sub-Alfvénic velocities, with a contribution coming mostly from particles on trapped and potato orbits, for the case of radial lines of sight. This is a unique feature of 10B(α, pγ)13C, which was not available by 9Be(α, nγ)12C, and may be exploited for α particle studies in low neutron yield scenarios and in preparation of high-power deuterium-tritium experiments.