"Advanced control system development for long pulse tokamak operations"
plasma physics,
numerical modeling,
detachment,
control engineering
Publications scientifiques au M2P2
2026
H Yang, N Fedorczak, G Ciraolo, E Serre, H Bufferand, et al.. Dynamical pathway to radiative divertor driven by transient X-point vortex in tokamaks. Physical Review Letters, 2026, ⟨10.1103/b6df-fg97⟩. ⟨hal-05435880v2⟩ Plus de détails...
Recent X-Point Radiator (XPR) experiments in L-mode plasmas of the WEST tokamak show that a stable radiative ring can be sustained above the X-point for approximately 70s, on timescales not limited by intrinsic plasma physics, demonstrating the compatibility of the XPR regime with long-pulse operation and its ability to mitigate divertor heat loads and tungsten contamination while maintaining core performance. Accessing this regime in future reactors, however, requires understanding its rapid formation dynamics. Here, for the first time, time-dependent fluid simulations including magnetic drifts are used to investigate the macroscopic dynamics of the rapid transition from an attached divertor to a stable XPR regime, qualitatively reproducing the experimentally observed millisecond-scale transition sequence. The simulations identify a transient X-point-centered vortex as the key transition-driving mechanism. Arising from the self-organized interplay of anomalous diffusion and drifts, the vortex regulates the entry of cold particles and impurities into the XPR region, increases neutral density and impurity concentration above the X-point without overcooling the edge, and thereby enables access to a stable XPR regime while preventing unstable XPR (known as MARFEs). By mixing cold and hot particles, steepening temperature gradients, and deepening the potential well, the vortex sustains a self-amplifying cycle over several milliseconds before saturating and decaying.
H Yang, N Fedorczak, G Ciraolo, E Serre, H Bufferand, et al.. Dynamical pathway to radiative divertor driven by transient X-point vortex in tokamaks. Physical Review Letters, 2026, ⟨10.1103/b6df-fg97⟩. ⟨hal-05435880v2⟩
G. Gallina, P. Giampa, F. Retière, J. Kroeger, G. Zhang, et al.. Characterization of the Hamamatsu VUV4 MPPCs for nEXO. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2019, 940, pp.371-379. ⟨10.1016/j.nima.2019.05.096⟩. ⟨hal-05443878⟩ Plus de détails...
In this paper we report on the characterization of the Hamamatsu VUV4 (S/N: S13370-6152) Vacuum Ultra-Violet (VUV) sensitive Silicon Photo-Multipliers (SiPMs) as part of the development of a solution for the detection of liquid xenon scintillation light for the nEXO experiment. Various SiPM features, such as: dark noise, gain, correlated avalanches, direct crosstalk and Photon Detection Efficiency (PDE) were measured in a dedicated setup at TRIUMF. SiPMs were characterized in the range 163 K ≤ T ≤ 233 K. At an over voltage of 3.1 ± 0.2 V and at T = 163 K we report a number of Correlated Avalanches (CAs) per pulse in the 1µs interval following the trigger pulse of 0.161±0.005. At the same settings the Dark-Noise (DN) rate is 0.137 ± 0.002 Hz/mm 2 . Both the number of CAs and the DN rate are within nEXO specifications. The PDE of the Hamamatsu VUV4 was measured for two different devices at T = 233 K for a mean wavelength of 189 ± 7 nm. At 3.6 ± 0.2 V and 3.5 ± 0.2 V of over voltage we report a PDE of 13.4 ± 2.6 % and 11 ± 2%, corresponding to a saturation PDE of 14.8 ± 2.8 % and 12.2±2.3%, respectively. Both values are well below the 24 % saturation PDE advertised by Hamamatsu. More generally, the second device tested at 3.5 ± 0.2 V of over voltage is below the nEXO PDE requirement. The first one instead yields a PDE that is marginally close to meeting the nEXO specifications. This suggests that with modest improvements the Hamamatsu VUV4 MP-PCs could be considered as an alternative to the FBK-LF SiPMs for the final design of the nEXO detector.
G. Gallina, P. Giampa, F. Retière, J. Kroeger, G. Zhang, et al.. Characterization of the Hamamatsu VUV4 MPPCs for nEXO. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2019, 940, pp.371-379. ⟨10.1016/j.nima.2019.05.096⟩. ⟨hal-05443878⟩
Journal: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
