Density peaking in JET—determined by fuelling or transport?

Tala, T.; Nordman, Hans; Salmi, A.; Bourdelle, C.; Citrin, J.; Czarnecka, A.; Eriksson, F.; Fransson, E.; Giroud, C.; Hillesheim, J.C.; Maggi, C. F.; Mantica, P.; Mariani, A.; Maslov, M.; Meneses, L.; Menmuir, S.; Mordijck, S.; Naulin, V.; Oberparleiter, M.; Sips, G.; Tegnered, Daniel; Tsalas, M.; Weisen, H.; Contributors, Jet

doi:10.1088/1741-4326/ab4248

Cited by 30 publications

(54 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, although this kind of ICRH-NBI identity pulse pair cannot be performed in JET high power conditions due to lack of the required ICRH power, the significant role played by the NBI fueling in contributing to density peaking seems very much plausible. There is in fact evidence on that, reported in reference [12] based on density peaking in the JET three-point dimensionless collisionality scan. However, there is also evidence that as the ITG turbulence is less dominant or in other words when TEM dominates, the role of NBI fueling in contributing to density peaking tends to decrease which have been published in references [13,14].…”

Section: Discussionmentioning

confidence: 76%

Role of NBI fuelling in contributing to density peaking between the ICRH and NBI identity plasmas on JET

et al. 2022

Self Cite

View full text Add to dashboard Cite

Density peaking has been studied between an ICRH and NBI identity plasma in JET. The comparison shows that 8MW of NBI heating/fueling increases the density peaking by a factor of two, being R/Ln=0.45 for the ICRH pulse and R/Ln=0.93 for the NBI one averaged radially over ρtor=0.4‒0.8. The dimensionless profiles of q, ρ*, υ*, βn and Ti/Te≈1 were matched within 5% difference except in the central part of the plasma (ρtor<0.3). The difference in the curvature pinch (same q-profile) and thermo-pinch (Ti=Te) between the ICRH and NBI discharges is virtually zero. Both the gyro-kinetic simulations and integrated modelling strongly support the experimental result where the NBI fuelling is the main contributor to the density peaking for this identity pair. It is to be noted here that the integrated modeling does not reproduce the measured electron density profiles, but approximately reproduces the difference in the density profiles between the ICRH and NBI discharge. Based on these modelling results and the analyses, the differences between the two pulses in impurities, fast ions, toroidal rotation and radiation do not cause any such changes in the background transport that would invalidate the experimental result where the NBI fuelling is the main contributor to the density peaking. This result of R/Ln increasing by a factor of 2 per 8MW of NBI power is valid for the ITG dominated low power H-mode plasmas. However, some of the physics processes influencing particle transport, like rotation, turbulence and fast ion content scale with power, and therefore, the simple scaling on the role of the NBI fuelling in JET is not necessarily the same under higher power conditions or in larger devices.

show abstract

Section: Discussionmentioning

confidence: 76%

Role of NBI fuelling in contributing to density peaking between the ICRH and NBI identity plasmas on JET

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…These observations suggest that the conclusions of this work remain valid for reactors. Isotope profiles tied to electron profiles regardless of core isotope source, fast isotope-mixing, and electron density peaking dominated by transport (due to large D e [13]), can all co-exist in a reactor relevant regime. This work directly follows from experimental [18] and theoretical [23] observation of large ion particle transport coefficients for ITG dominated plasmas.…”

Section: Sensitivitiesmentioning

confidence: 99%

First-principles-based multiple-isotope particle transport modelling at JET

et al. 2020

Self Cite

View full text Add to dashboard Cite

Core turbulent particle transport with multiple isotopes can display observable differences in behaviour between the electron and ion particle channels. Experimental observations at JET with mixed H-D plasmas and varying NBI and gas-puff sources [M. Maslov et al., Nucl. Fusion 7 076022 (2018)] inferred source dominated electron peaking, but transport dominated isotope peaking. In this work, we apply the QuaLiKiz quasilinear gyrokinetic transport model within JINTRAC flux-driven integrated modelling, for core transport validation in this multiple-isotope regime. The experiments are successfully reproduced, predicting self consistently j, ne, n Be , Te, T i , ωtor and the isotope composition. As seen in the experiments, both H and D profiles are predicted to be peaked regardless of the core isotope source. An extensive sensitivity study confirmed that this result does not depend on the specific choices made for the boundary conditions and physics settings. While kinetic profiles and electron density peaking did vary depending on the simulation parameters, the isotope ratio remained nearly invariant, and tied to the electron density profile. These findings have positive ramifications for multiple-isotope fuelling, burn control, and helium ash removal.

show abstract

“…Also, it is clear that the density peaking of the deuterium plasma is lower than for the hydrogen plasma, however this could be related to the lower density pedestal leading to increased core beam fuelling. Density peaking due to core sources and transport has been the subject of many studies and the relative contribution remains uncertain, requiring further investigation and more experiments [27], [28], [29] . Modelling has shown that there is a weak effect of isotope mass on density peaking but this was in plasmas without NBI heating, so there was no central source of particles [30].…”

Section: Isotope Exchangementioning

confidence: 99%

Mixed hydrogen-deuterium plasmas on JET ILW

et al. 2020

Self Cite

View full text Add to dashboard Cite

A study of mixed hydrogen-deuterium H-mode plasmas has been carried out in JET-ILW to strengthen the physics basis for extrapolations to JET D-T operation and to support the development of strategies for isotope ratio control in future experiments. Variations of input power, gas fuelling and isotopic mixture were performed in H-mode plasmas of the same magnetic field, plasma current and divertor configuration. The analysis of the energy confinement as a function of isotope mixture reveals that the biggest change is seen in plasmas with small fractions of H or D, in particular when including pure isotope plasmas. To interpret the results correctly, the dependence of the power threshold for access to type-I ELMing H-modes on the isotope mixture must be taken into account. For plasmas with effective mass between 1.2 and 1.8 the plasma thermal stored energy () scales as , which is weaker than that in the ITER physics basis, IPB98 scaling. At fixed stored energy, deuterium-rich plasmas feature higher density pedestals, while the temperature at the pedestal top is lower, showing that at the same gas fuelling rate and power level, the pedestal pressure remains constant with an exchange of density and temperature as the isotope ratio is varied. Isotope control was successfully tested in JET-ILW by changing the isotope ratio throughout a discharge, switching from D to H gas puffing. Several energy confinement times (300 ms) are needed to fully change the isotope ratio during a discharge.

show abstract

Density peaking in JET—determined by fuelling or transport?

Cited by 30 publications

References 37 publications

Role of NBI fuelling in contributing to density peaking between the ICRH and NBI identity plasmas on JET

Role of NBI fuelling in contributing to density peaking between the ICRH and NBI identity plasmas on JET

First-principles-based multiple-isotope particle transport modelling at JET

Mixed hydrogen-deuterium plasmas on JET ILW

Contact Info

Product

Resources

About