Description
Radial correlation reflectometry analysis of tritium-rich and hybrid JET plasmas
A. Figueiredo$^1$, M. Maslov$^2$, C.D. Challis$^2$, C. Giroud$^2$, J. Hobirk$^3$, A. Kappatou$^3$, D.B. King$^2$, E. Lerche$^4$, JET contributors$^5$, and the EUROfusion Tokamak Exploitation Team$^6$
$^1$ IPFN, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
$^3$ UKAEA, Culham Campus, Abingdon OX143DB, United Kingdom
$^3$ Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
$^4$ Laboratory for Plasma Physics, ERM/KMS, B-1000 Brussels, Belgium
$^5$ See the author list of C.F. Maggi et al 2024 Nucl. Fusion 64 https://doi.org/10.1088/1741-4326/ad3e16
$^6$ See the author list of N. Vianello et al 2026 Nucl. Fusion in press https://doi.org/10.1088/1741-4326/ae71ec
Experimental evidence indicates that the presence of internal transport barriers (ITBs) significantly influences tungsten transport, particularly in tritium-rich regimes, which are complementary to 50/50 deuterium/tritium plasma mixture scenarios and were instrumental in achieving the record fusion power output during the 2023 JET D-T campaign.
A qualitative analysis of radial correlation reflectometry (RCR) data is presented, focusing primarily on the two most recent JET D-T campaigns, to provide insight into the behavior of turbulence in high-performance tritium-rich pulses and related hybrid discharges, with emphasis on the role of ITBs and their connection to tungsten accumulation.
The timing of the heating power is the same for all discharges included in the analysis, and density fluctuations were measured using the same reflectometer configuration, allowing for a consistent comparison across pulses. The dataset is characterized by high measurement quality, with strong coherence between the two microwave channels that systematically decreases with increasing separation of their cutoff layers. The probing beams access the plasma core and reach the foot of the ITB, frequently extending beyond in the hybrid pulses.
The analysis is carried out examining spectral characteristics such as the presence of quasi-coherent modes, the coherent reflection of the microwave beams, and RCR radial correlation lengths. The observations are consistent with a reduction of turbulence in the ITB region, especially for the best-performing discharges. Furthermore, the results indicate that, in tritium-rich pulses, a higher ion cyclotron resonance heating power is associated with a less pronounced turbulence increase at the termination of the ITB.
References
[1] M. Maslov et al Nucl. Fusion 63 (2023) 112002
[2] J. Hobirk et al Nucl. Fusion 63 (2023) 112001
[3] C.F. Maggi et al Nucl. Fusion 64 (2024) 112012
[4] A. Kappatou et al Plasma Phys. Control. Fusion 67 (2025) 045039
[5] A. Figueiredo et al Rev. Sci. Instrum. 79 (2008) 10F107