1,135 research outputs found
Moderate beta baseline scenario in preparation to D-T operations at JET
No full textIn 2021, JET will operate with a D-T plasma mixture. To achieve high fusion power with a steady performance, two ELMy H-mode scenarios are under development: the baseline scenario, with low βN where good confinement is achieved at high current and the hybrid scenario, at lower current and higher βN, with a shaped current profile. Most of the extrapolations done for baseline plasmas used as reference one of the baseline most performing pulses with a βN ≈ 2.2 which is higher
than usual in typical baseline pulses. In this work we present the results of the predictive simulations done with the JINTRAC suite of codes and the QuaLiKiZ transport model, using as reference a more conventional baseline with q95 ≈ 3 and βN ≈ 1.8. The simulation settings and the transport model have been validated against the experimental results obtained in D-T plasma mixture during DTE1, when JET was equipped with a carbon wall, and against the experimental results obtained in D plasmas both with the C wall and the ITER-like wall (Be/W) installed in 2011. The extrapolations to D-T plasma mixture at high current show that 10 MW of fusion power are achievable in a wide range of experimental conditions, while 15 MW of fusion power could be approached only with full auxiliary
power (40 MW)in particularly pure plasmas
Single-pass absorption simulations in Divertor Tokamak Test scenario
No full textAn analysis of the Ion Cyclotron Resonance Heating (ICRH) propagation and single-pass absorption in DTT (Divertor Tokamak Test facility) heating scenarios has been performed by means of the numerical tool TOMCAT. It allows to study wave propagation and damping as well as mode conversion for a 1D plasma of Maxwellian species and it is based on solving a twelfth-order differential system using the finite-element formalism. This analysis aimed to explore a wider parameter space compared to previous results obtained using TORIC, with the goal of enhancing the understanding of DTT scenarios and confirming the physics inputs to system design. Scenarios of minority heating at 3T and 6T were analyzed, simulating with different plasma species, including varying concentrations of D, 3He, and H, across the frequency range from 45 MHz to 90MHz. Three-ion scenarios for full-field scenarios have been analyzed too, indicating the need for further exploration to determine the plasma and radio frequency (RF) parameters required to achieve significant power absorption by the third ion species. Finally, an approximate evaluation of the ICRH contribution to heat load has been also performed
Semi-analytical derivation of the 2D all-FLR ICRH wave equation as a high-order partial differential equation
No full textFor 1-dimensional applications, Bude's method [Bude et al, Plasma Phys.
Control. Fusion, 63 (2021) 035014] has been shown to be capable of accurately
solving the all-FLR (Finite Larmor Radius) integro-differential wave equation
as a high-order differential equation allowing to represent all physically
relevant (fast, slow and Bernstein) modes upon making a polynomial fit that is
accurate in the relevant part of k-space. The adopted fit is superior to the
Taylor series expansion traditionally adopted to truncate the series of finite
Larmor radius corrections, while the differential rather than
integro-differential approach allows for significant gain in required
computational time when solving the wave equation. The method was originally
proposed and successfully tested in 1D for radio frequency (RF) waves and in
absence of the poloidal field [D. Van Eester & E. Lerche, Nucl. Fusion, 61
(2021) 016024]. In the present paper, the derivation of the extension of that
procedure to 2D and for finite poloidal field - semi-analytically yielding the
coefficients of the relevant high-order partial differential equation - is
discussed in preparation of future numerical application
Scrape-Off Layer opacity to D and T gas puff fuelling in JET baseline scenario
No full textDetermining the particle sources within the separatrix is crucial for understanding the
fuelling efficiency of fusion devices. Particle sources from Neutral Beam Injection (NBI) and pellets
can be confidently assessed through modelling and experimental measurements, whereas those from gas
puff injections remain challenging to determine in present experiments, and often are not measured (e.g.
at JET). Experimental observations of the baseline pulses performed at JET indicate different behaviours
for deuterium (D) and tritium (T), influenced by the opacity of the Scrape-Off Layer (SOL) and the
diffusion of these elements into the separatrix due to their distinct neutral dynamics. This study
investigates the SOL opacity for different D and T fuelling levels in JET (DTE2) baseline plasmas
through Core-SOL integrated modelling, using the JINTRAC [1] suite of codes equipped with the semiempirical Bohm/gyro-Bohm transport model [2]. The experimental overview of the pulses analysed in
this work can be find in [3]. The simulation settings are briefly presented in section 2, while the
modelling results of a core-SOL coupled simulation for the Deuterium pulse (JPN 96482) and the
Tritium one (JPN 99282) are presented in section 3. The nominal gas rate is then varied to evaluate the
SOL opacity and the gas puff fuelling efficiency to different gas puff levels, at first in steps (Sec. 3) and
then in linear ramps with different ramp velocities (Sec. 4
COREDIV simulations of D and D-T high current-high power Baseline pulses in JET-ITER like wall
No full textThe two best performing pulses of the so called ITER-Baseline scenario (I p = 3.5 MA and P in ≈ 35 MW) of JET-ITER like wall, one in deuterium (D) the other in deuterium-tritium (D-T) plasma are examined and compared in this study. Generally, the D-T Baseline pulses exhibit an electron density level higher than the D pulses and the plasma energy is higher than in the comparable D pulses by up to 20%, reaching about 12 MJ in the pulse studied here. In contrast with the D pulses, the D-T pulses are often characterised by the increase in time of the radiated power in the mantle region (0.70 < ρ < 0.95), which may lead to the loss of the edge localised mode activity when the threshold H-L transition power is approached and to the subsequent plasma disruption due to excessive radiation. In this study we try to identify the physical mechanisms responsible for this behaviour using the available experimental data (principally the total radiated power from the bolometry) and the results of the fluid COREDIV model (1D in the core, 2D in the scrape-off-layer (SOL)), self-consistent with respect to core-SOL and also to main plasma-impurities. In fact, the loss of power caused by impurity radiation affects the temperature profile and finally the power to the divertor plate. The electron density and temperature profiles are numerically reconstructed as well as the radiated power density profiles, indicating no major difference in impurity transport in D and D-T. Indeed, the impurity transport coefficients used in COREDIV to match the experimental radiated power profiles are similar in the two pulses. The computed tungsten sources and densities are lower in the D-T pulse and the divertor impurity retention capability is a little better in the D-T pulse, indicatinga stronger collisional drag force in the SOL. The higher electron density and the broadening of its profile are the main cause of the observed increase of the radiated power in the D-T pulse
Effects of the parallel flow shear on the ITG-driven turbulent transport in tokamak plasmas
No full textThe impact of the parallel flow shear on the tokamak plasma stability and turbulent transport driven by the ion temperature gradient (ITG) modes is analyzed by means of local gyrokinetic numerical analyses. It is shown that the parallel flow shear increases the ITG growth rate in the linear regime, and induces a broadening and shift of the radial spectrum. Then, the different effects of the finite parallel shear on the ITG turbulence characteristics are deeply analyzed in the nonlinear regime. These studies highlight that a reduction of the thermal-ion turbulent heat flux is induced by a complex mechanism involving the nonlinear generation of an enhanced zonal flow activity. Indeed, the turbulent sources of the zonal flows are increased by the introduction of the finite parallel flow shear in the system, beneficially acting on the saturation level of the ITG turbulence. The study has been carried out for the Waltz standard case below the critical threshold of the destabilization of the parallel velocity gradient instability, and then generalized to a selected pulse of a recent JET scenario with substantial toroidal rotation in the edge plasma region. It is, thus, suggested that the investigated complex mechanism triggered by the finite parallel flow shear reducing the ITG turbulent heat fluxes could be complementary to the well-established perpendicular flow shear in a region with sufficiently large plasma toroidal rotation
Impurity behaviour in JET high-current baseline scenario for Deuterium, Tritium and Deuterium-Tritium plasmas
No full textTo support future ITER operation, experimental campaigns at the Joint European Torus (JET) with an ITER-like wall (tungsten divertor and beryllium main chamber) in pure deuterium (D), tritium (T) and Deuterium-Tritium (D-T) were performed. One of the most important challenges in recent years was the development of two main scenarios that investigated different approaches to achieve the high fusion power as well as good plasma confinement (Garzotti et al., 2023). The first one, so-called baseline scenario is relying on high plasma current (Ip≈3.5 MA), normalized beta βN < 2 and safety factor q95 ≈ 3 (Garzotti et al., 2023). On the other hand, the second one, so-called Hybrid scenario is operating at lower plasma current (flat-top Ip ≤ 2.6 MA) and density with respect to the baseline, higher normalized beta βN > 2 and safety factor q95 ≈ 4.8 (Hobirk et al., 2023). In this paper we focus on the impurity behaviour analysis for the baseline discharges at Ip = 3.5 MA and BT = 3.3 T with D, T and DT plasmas, in which the gas and power waveform were optimized to achieve the best possible performance. In particular, we study the impact of total heating power (Ptot + Palpha), flat-top gas flow and ELM (edge localized modes) frequency on mid-Z (Nickel (Ni), Copper (Cu)) and high-Z (Tungsten (W)) impurities. In addition, we compared the two best performing pulses of the baseline scenario (Ip = 3.5MA, BT = 3.3 T and Pin ≈ 35 MW) in D and DT in order to identify the causes responsible for the increase in radiation during the DT pulse, which led to an early plasma termination. All presented results rely on the data collected by the VUV as well as the bolometry system. Detailed analysis indicates that in the baseline scenario, higher radiation, which is most likely due to the tungsten (W), is observed for T and DT plasmas in comparison to D. Moreover, for the two best performing baseline pulses, tomographic reconstructions show that the radiated power density is mainly emitted from the low field side (LFS) of the plasma and W does not accumulate in the plasma center (Telesca et al., 2024)
Approximate zero-one laws and sharpness of the percolation transition in a class of models including two-dimensional Ising percolation
No full textInterpretative TRANSP analysis of JET baseline scenario: performance dependence on kinetic plasma parameters
No full textThe baseline scenario stands out as one of the most promising plasma states suitable for high- performance DT operation. This work focuses on the JET D-T baseline scenario (Ip = 3.0 M A, q95 = 3, βN < 2) from the DTE2 campaign, held in 2021, and the more recent 2023 DTE3. One of the main operational differences between the two campaigns is the choice of beam fuels and net power use: the DTE3 campaign employs pure Deuterium beams with ~29 MW, whereas the DTE2 uses a 50-50 DT beam mix with ~24 MW. This distinction impacts not only the particle source but also the beam penetration and the plasma heating. To assess the scenario performance, an extensive interpretive modeling effort has been performed with TRANSP, comparing the numerical results against key indicators, such as neutron yield, stored energy, fast ion population and radiation profile. Starting from a DTE2 reference, simulations were performed changing the beam gas to pure D and scanning the injection energy. It results that a 20% reduction of the injection energy is needed to achieve a deposition similar to DTE2. On this DTE2 reference and its DTE3 counterpart, the dependence of various plasma parameters has been explored: Zeff was varied within the experimental error bars, and different impurity mixes were explored. In particular, for the DTE3 pulse the numerical neutron rate results larger than the experimental one, and only a fair agreement can be recovered by invoking a large dilution (higher Zeff and/or light impurity). The fast particle population was characterized in relation to the MHD activity, assuming an effective anomalous fast ion diffusivity. With this analysis, we try to assess the impact on the performance due to the differences between DTE2 and DTE3 in the setup of the experiments (e.g. NBI) and the experimental conditions (e.g. impurity mix composition)
Recent advances on ion cyclotron resonance heating scenarios for Divertor Tokamak Test facility
No full textAn analysis of the Ion Cyclotron Resonance Heating (ICRH) propagation and single-pass absorption in DTT (Divertor Tokamak Test facility) [1] heating scenarios has been performed by TOMCAT 1D full-wave kinetic wave equation code [2]. This analysis aimed to explore a wider parameter space compared to previous studies [3,4], with the goal of enhancing the understanding of DTT. Minority heating schemes at 3T and 6T were analyzed, simulating with different plasma species, including varying concentrations of D, 3He, and H, across the frequency range from 50 MHz to 90MHz. A very promising reduced-field configuration will be presented. Furthermore, three-ion heating schemes for full-field configurations were investigated, building on the findings from [5], leading to the identification of an efficient scenario. An analysis with TORIC [6] was subsequently carried out, providing positive feedback on the results obtained with TOMCAT
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