Speaker
Description
Recent deuterium-tritium (D-T) experiments at JET have uncovered a range of new phenomena involving alpha-particles and energetic ions in the plasma [1-3]. Understanding and controlling alpha particles is an important task for ITER, given its goal to achieve Q = 10 in plasmas with a full-tungsten first wall and divertor. Key challenges include developing diagnostics to measure alpha particles in plasmas without beryllium impurities, investigating the effects of alpha particles and fast-ion-driven instabilities on thermal confinement, understanding alpha redistribution in the presence of sawteeth and other plasma instabilities [4], etc.
Following the stop of plasma operations at JET, there is currently no magnetic confinement device capable of D-T plasma operations. This talk will highlight the use of mixed D-$^3$He plasmas as an alternative source of alpha particles with birth energies of ~3.6 MeV, offering a promising way to address gaps in alpha-particle physics research without using tritium in fusion devices. We will begin by summarizing the alpha-physics results from the dedicated D-$^3$He plasma experiments at JET [5, 6], where ICRF and NBI heating were applied to generate high-energy deuterons (the D-$^3$He fusion reaction cross-section peaks at deuterium energies of ~450 keV). The resulting alpha production rate reached approximately 1-2x10$^{16}$ s$^{-1}$, a level sufficient for gamma-ray spectroscopy measurements of alpha particles and observation of plasma instabilities driven by fusion-born alphas [7].
JT-60SA, the world's largest superconducting tokamak currently in operation, will play a crucial role in supporting ITER and DEMO. Equipped with a powerful negative NBI system capable of delivering deuterons with energies up to 500 keV, JT-60SA is ideally suited for alpha-particle experiments in D-$^3$He plasmas. This talk will present the design of a dedicated scenario for alpha-particle generation in JT-60SA. Extensive ASCOT modeling has been conducted to assess the spatial and energy characteristics of fusion-born alphas and to optimize their production rate. Our modeling results predict an alpha production rate of 2-3x10$^{16}$ s$^{-1}$, which can be achieved with the high-power N-NBI system at moderate $^3$He concentrations (10-15%), surpassing the alpha production rate observed in D-$^3$He plasmas at JET.
This presentation will highlight how recent findings from JET and upcoming fast-ion experiments at JT-60SA can contribute to the ITER rebaseline, particularly in the areas of fast-ion physics and alpha-particle behavior [8].
[1] S.E. Sharapov et al., Nucl. Fusion 63, 112007 (2023)
[2] M.J. Mantsinen et al., Nucl. Fusion 63, 112015 (2023)
[3] J. Garcia, Ye.O. Kazakov et al., Nature Communications 15, 7846 (2024)
[4] A. Bierwage et al., Nature Communications 13, 3941 (2022)
[5] Ye.O. Kazakov et al., Phys. Plasmas 28, 020501(2021)
[6] Ye.O. Kazakov et al., AIP Conf. Proc. 2984, 020001 (2023)
[7] V.G. Kiptily, Ye.O. Kazakov et al., Plasma Phys. Control. Fusion 64, 064001 (2022)
[8] A. Loarte et al., 'The new ITER Baseline, Research Plan and Open R&D issues' (2024)
| Presentation type | Oral |
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