Speaker
Description
Plasma–material interactions are a key challenge for magnetic confinement fusion and are widely investigated in linear plasma devices. The GyM [1] linear device currently operates at plasma densities of $10^{15}–10^{17}\text{m}^{-3}$, electron temperatures below 15 eV, and ion fluxes up to $10^{21} \text{m}^{-2} \text{s}^{-1}$, representative of tokamak main chamber conditions.
To reach divertor–relevant plasma regimes (densities of about $10^{19}\text{m}^{-3}$ and ion fluxes approaching $10^{23} \text{m}^{-2} \text{s}^{-1}$), GyM is being upgraded to the high–density BiGyM device, featuring helicon–wave plasma generation via two 10 kW birdcage antennas at 13.56 MHz, a revised magnetic configuration, a redesigned vacuum vessel, and new in–situ surface diagnostics.
This contribution presents the plasma modelling activities conducted with SOLPS–ITER[2] to support the upgrade. Parametric simulations assessed the influence of injected power, neutral pressure, magnetic field configuration, and boundary conditions on plasma density and temperature. Different working gases, including helium and argon, were considered to evaluate the plasma performances.
For a representative discharge in helium (B = 20 mT, p = 0.8 Pa, P = 3 kW), predicted electron densities of $(1.5–2.0)\times 10^{19} \text{m}^{-3}$ and electron temperatures of 4–5 eV are obtained along the device axis.
Plasma density and temperature vary by less than 15% across the different magnetic configurations, at a fixed absorbed power density. For refining the spatial distribution of electron heating according to the magnetic configuration, initial work has been carried out to couple SOLPS–ITER simulations with power deposition modelling from helicon sources performed in COMSOL.
The predicted plasma conditions meet the performance targets set for the BiGyM upgrade, confirming that the adopted design choices are well suited to access divertor–relevant regimes and supporting the finalisation of the device construction.
Acknowledgments
This work has been carried out within the framework of Italian National Recovery and Resilience Plan (NRRP), funded by the European Union - NextGenerationEU (Mission 4, Component 2, Investment 3.1 - Area ESFRI Energy - Call for tender No. 3264 of 28-12-2021 of Italian University and Research Ministry (MUR), Project ID IR0000007, MUR Concession Decree No. 243 del 04/08/2022, CUP B53C22003070006, "NEFERTARI").
This work was partly funded by the Swiss National Science Foundation, Grant 200020-204983.
References
[1] A.Uccello et al, Front. Phys. 11:1108175 (2023)
[2] S.Wiesen et al, Journal of Nuclear Materials 463 (2015) 480–484
