14 research outputs found
Impact of RF waves â fast NBI ions interaction on the fusion performance in JET DTE2 campaign
This work studies the interaction between Radio Frequency (RF) waves used for Ion Cyclotron Resonance Heating (ICRH) and the fast Deuterium (D) and Tritium (T) Neutral Beam Injected (NBI) ions in DT plasma. The focus is on the effect of this interaction, also referred to as synergistic effects, on the fusion performance in the recent JET DTE2 campaign. Experimental data from dedicated pulses at 3.43T/2.3MA heated at (i) 51.4MHz giving central minority H and n=2 D and at (ii) 32.2MHz for central minority 3He and n=2 T resonances were analyzed and conclusions were drawn and supported by modelling of the synergistic effects. TRANSP runs with and without RF kick operator predicted moderate increase, about 10%, in DT rates for the case of RF wave - fast D NBI ions interactions at n=2 harmonic of ion cyclotron resonance and negligible impact by synergistic interaction between fast T NBI ions and RF waves. JETTO modelling gives 29% enhancement of fusion rates due to RF waves â fast D NBI ions interaction and 18% enhancement for fast T NBI ions. Analysis of experimental neutron rates compared to TRANSP predictions without synergistic effects and Magnetic Proton Recoil (MPRu) neutron spectrometer indicate approximately 25-28% enhancement of fusion rates due to RF interaction with fast D ions and approximately 5-8% when RF wave â fast T NBI ions interaction is taking place. Contribution of various heating and fast ion sources have been assessed and discussed.
}This work has been carried out within the framework of the EUROfusion Consortium, funded by the
European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 â
EUROfusion) and from the EPSRC [grant number EP/W006839/1]. To obtain further information on the
data and models underlying this paper please contact [email protected] . Views and opinions
expressed are however those of the author(s) only and do not necessarily reflect those of the European
Union or the European Commission. Neither the European Union nor the European Commission can be
held responsible for them.Peer Reviewed"Article signat per 23 autors/es: Krassimir K Kirov, Clive D Challis, Elena de la Luna, Jacob Eriksson, Daniel Gallart, Jeronimo Garcia, Marina Gorelenkova, Joerg Hobirk, Philippe Jacquet, Athina Kappatou, Yevgen Kazakov, David Keeling, Damian King, Ernesto A Lerche, Costanza F Maggi, Joelle Mailloux, Paola Mantica, Mervi Mantsinen, Mikhail Maslov, Sheena Menmuir, Paula SirĂ©n, Ćœiga Ć tancar and Dirk Van Eester"Postprint (published version
Real-time modelling of fusion plasmas and the consequences of a simplified ion cyclotron resonance heating model
Overview of T and D-T results in JET with ITER-like wall
In 2021 JET exploited its unique capabilities to operate with T and DâT fuel with an ITER-like Be/W wall (JET-ILW). This second major JET DâT campaign (DTE2), after DTE1 in 1997, represented the culmination of a series of JET enhancementsânew fusion diagnostics, new T injection capabilities, refurbishment of the T plant, increased auxiliary heating, in-vessel calibration of 14 MeV neutron yield monitorsâas well as significant advances in plasma theory and modelling in the fusion community. DTE2 was complemented by a sequence of isotope physics campaigns encompassing operation in pure tritium at high T-NBI power. Carefully conducted for safe operation with tritium, the new T and DâT experiments used 1 kg of T (vs 100 g in DTE1), yielding the most fusion reactor relevant DâT plasmas to date and expanding our understanding of isotopes and DâT mixture physics. Furthermore, since the JET T and DTE2 campaigns occurred almost 25 years after the last major DâT tokamak experiment, it was also a strategic goal of the European fusion programme to refresh operational experience of a nuclear tokamak to prepare staff for ITER operation. The key physics results of the JET T and DTE2 experiments, carried out within the EUROfusion JET1 work package, are reported in this paper. Progress in the technological exploitation of JET DâT operations, development and validation of nuclear codes, neutronic tools and techniques for ITER operations carried out by EUROfusion (started within the Horizon 2020 Framework Programme and continuing under the Horizon Europe FP) are reported in (Litaudon et al Nucl. Fusion accepted), while JET experience on T and DâT operations is presented in (King et al Nucl. Fusion submitted)
20 years of research on the Alcator C-Mod tokamak
The object of this review is to summarize the achievements of research on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994) and Marmar, Fusion Sci. Technol. 51, 261 (2007)] and to place that research in the context of the quest for practical fusion energy. C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since it began operation in 1993, contributing data that extends tests of critical physical models into new parameter ranges and into new regimes. Using only high-power radio frequency (RF) waves for heating and current drive with innovative launching structures, C-Mod operates routinely at reactor level power densities and achieves plasma pressures higher than any other toroidal confinement device. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing componentsâapproaches subsequently adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated the critical role of cross-field transport in divertor operation, edge flows and the tokamak density limit. C-Mod developed the I-mode and the Enhanced Dα H-mode regimes, which have high performance without large edge localized modes and with pedestal transport self-regulated by short-wavelength electromagnetic waves. C-Mod has carried out pioneering studies of intrinsic rotation and demonstrated that self-generated flow shear can be strong enough in some cases to significantly modify transport. C-Mod made the first quantitative link between the pedestal temperature and the H-mode's performance, showing that the observed self-similar temperature profiles were consistent with critical-gradient-length theories and followed up with quantitative tests of nonlinear gyrokinetic models. RF research highlights include direct experimental observation of ion cyclotron range of frequency (ICRF) mode-conversion, ICRF flow drive, demonstration of lower-hybrid current drive at ITER-like densities and fields and, using a set of novel diagnostics, extensive validation of advanced RF codes. Disruption studies on C-Mod provided the first observation of non-axisymmetric halo currents and non-axisymmetric radiation in mitigated disruptions. A summary of important achievements and discoveries are included.United States. Dept. of Energy (Cooperative Agreement DE-FC02-99ER54512)United States. Dept. of Energy (Cooperative Agreement DE-FG03-94ER-54241)United States. Dept. of Energy (Cooperative Agreement DE-AC02-78ET- 51013)United States. Dept. of Energy (Cooperative Agreement DE-AC02-09CH11466)United States. Dept. of Energy (Cooperative Agreement DE-FG02-95ER54309)United States. Dept. of Energy (Cooperative Agreement DE-AC02-05CH11231)United States. Dept. of Energy (Cooperative Agreement DE-AC52-07NA27344)United States. Dept. of Energy (Cooperative Agreement DE-FG02- 97ER54392)United States. Dept. of Energy (Cooperative Agreement DE-SC00-02060
Mode Conversion Current Drive Experiments on Alcator C-Mod
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 189-197).In tokamak plasmas with multiple ion species, fast magnetosonic waves (FW) in the Ion Cyclotron Range of Frequency can mode convert to shorter wavelength modes at the Ion-Ion hybrid layer, leading to localized electron heating and current drive. Due to k1l upshifts associated with the poloidal magnetic field, only small net driven currents were predicted from mode converted Ion Bernstein Waves (IBW). As studied first by Perkins, and later confirmed experimentally with Phase Contrast Imaging measurements on Alcator C-Mod, poloidal field effects can also lead to mode conversion to Ion Cyclotron Waves (MCICW), on the low field side of the mode conversion layer. In this thesis, mode conversion current drive in the ICW-dominated regime is studied numerically and through experiments on Alcator C-Mod. Solving a dispersion relation for the mode converted waves in a slab geometry relevant to tokamak equilibria and in the finite Larmor radius limit, we find that mode conversion to Ion Cyclotron Waves is ubiquitous to high temperature conventional tokamaks, as a result of the central value for the safety factor qo 1. MCICWs are identified as kinetically modified Ion Cyclotron Waves in the regime w/kllVthe < 1. Full wave simulations with the TORIC code predict net currents can be driven by MCICW as a result of up-down asymmetries in the mode conversion process. Initial estimates with the Ehst-Karney parametrization indicated up to -- 100 kA could be driven for 3 MW input power in C-Mod plasmas. More accurate calculations, consistent with the polarization of MCICWs, were carried out by importing a quasilinear diffusion operator build from the TORIC fields in the Fokker-Planck code DKE, and predicted lower current drive efficiencies by a factor of 2.(cont.) The TFTR discharges in 1996 where net MCCD currents were inferred experimentally from loop voltage differences were simulated with TORIC, which indicates mode conversion to ICW can account for the driven currents. Similar loop voltage experiments in D(3He) plasmas were attempted on Alcator C-Mod, but did not yield conclusive current drive measurements. The lack of control over Zeff in C-Mod, which is illustrative of ICRF operation in tokamaks with metallic walls, makes reaching optimal plasma conditions for MCCD difficult, and limits the range of parameters in which MCCD can be useful as a net current drive tool in C-Mod. Solving the current diffusion equation in the cylindrical limit and with sawtooth reconnection models, the large sawtooth oscillations in C-Mod plasmas were also found to complicate current relaxation and hinder the loop voltage analysis for small central driven currents inside the q = 1 surface. In separate experiments on Alcator C-Mod, sawtooth period changes were used to infer localized MCCD near the q = 1 surface. The mode conversion layer was swept outward through the q = 1 surface in D(3He) plasmas, and the sawtooth period was found to vary from 3 to 12 ms, which is consistent wih localized current drive and TORIC predictions. A similar evolution was found in heating and co-current drive phasing, which suggests net currents are driven with a symmetric antenna spectrum, as predicted by TORIC as a result of asymmetries in the mode conversion process. Simulations of the sawtooth cycle with the Porcelli trigger model indicate that TORIC currents can account for the sawtooth period evolution in heating phasing.(cont.) Based on simulations of the saw-tooth cycle with the Porcelli trigger model, localized electron heating, which could also explain the experimental results, was found not to be dominant compared to the current drive effect. The experimental results demonstrate that, while not optimal, MCCD can be used for sawtooth control.by Alexandre Parisot.Ph.D