Reduced physics model of the tokamak Scrape-Off-Layer for pulse design

Zhang, X.; Poli, F. M.; Emdee, Eric; Podestà, M.

doi:10.1016/j.nme.2022.101354

Cited by 3 publications

(6 citation statements)

References 23 publications

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“…An important result from the simulations with selfconsistent boundary conditions is the difference from the 'time-slice' simulations in which edge values were prescribed based on results from other devices, cf panels (c) and (d) in figure 15. The computed values of edge temperature through the two-point model [28] are considerably lower than the ≈100 eV initially assumed, e.g. in figure 12.…”

Section: Scenario Evolutionmentioning

confidence: 66%

“…The extension of predictive simulations for T e and T i to the entire discharge, including the current ramp-up and a self-consistent estimate of pedestal parameters, provides more insight on the predicted parameters. It is clear that adding selfconsistent boundary conditions through a reduced scrape-off layer model [28] largely modifies the simulations' outcome, for instance by suggesting more peaked profiles with lower edge temperature than what initially predicted in [7]. Future work will focus on this issue, as well as on the comparison across different thermal transport models to assess the reliability of present numerical tools for scenario predictions.…”

Section: Discussionmentioning

confidence: 92%

“…Finally, simulations that predict both the ramp-up and the flattop phase (section 5.2) evolve the values of density and temperature at the separatrix, based on a two-point Scrape-Off-Layer (SOL) model [28]. The two-point SOL model extends previous work [29,30] to calculate the electron/ion temperature and plasma density in the SOL, given the particle and power fluxes from the core through the LCFS calculated by TRANSP and given recycling coefficients.…”

Section: Transp Code For Scenario Developmentmentioning

confidence: 99%

“…The flat region in temperature observed for 0.8 ⩽ ρ ⩽ 0.9 in figure 11 suggests that edge parameters should actually be lower in the Ohmic case. Examples of more self-consistent predictions through a reduced scrape-off layer model [28] are discussed in section 5.2. The addition of NBI and finite plasma rotation brings T e up to 700 eV on axis.…”

Section: Profile Prediction In the Current Flat-topmentioning

confidence: 99%

“…In this section, examples of whole discharge simulations are discussed. A main difference for these simulations is the inclusion of a selfconsistent model to compute boundary conditions for T e and T i predictions [28], which leads to adjustments in the edge temperature based on the particle and power flux through the separatrix. As shown in the following Sections, resolving the thermal plasma and fast ion dynamic is key for further discharge optimization exercises.…”

Section: Examples Of Discharge Evolution From Ramp-up To Ip Flat-topmentioning

confidence: 99%

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NBI optimization on SMART and implications for scenario development

Podestà,

Cruz-Zabala,

Poli

et al. 2024

Plasma Phys. Control. Fusion

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The SMall Aspect Ratio Tokamak (SMART) under commissioning at the University of Seville, Spain, aims to explore confinement properties and possible advantages in confinement for compact/spherical tokamaks operating at negative vs. positive triangularity. This work explores the benefits of auxiliary heating through Neutral Beam Injection (NBI) for SMART scenarios beyond the initial Ohmic phase of operations, in support of the device’s mission. Expected values of electron and ion temperature achievable with NBI heating are first predicted for the current flat-top phase, including modeling to optimize the NBI injection geometry to maximize NBI absorption and minimize losses for a given equilibrium. Simulations are then extended for a selected case to cover the current ramp-up phase. Differences with results obtained for the flat-top phase indicate the importance of determining the plasma evolution over time, as well as self-consistently determining the edge plasma parameters for reliable time-dependent simulations. Initial simulation results indicate the advantage of auxiliary NBI heating to achieve nearly double values of pressure and stored energy compared to Ohmic discharges, thus significantly increasing the device’s performance. The scenarios developed in this work will also contribute to diagnostic development and optimization for SMART, as well as providing test cases for initial predictions of macro- and micro-instabilities.

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Section: Scenario Evolutionmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 92%

Section: Transp Code For Scenario Developmentmentioning

confidence: 99%

Section: Profile Prediction In the Current Flat-topmentioning

confidence: 99%

Section: Examples Of Discharge Evolution From Ramp-up To Ip Flat-topmentioning

confidence: 99%

See 3 more Smart Citations

NBI optimization on SMART and implications for scenario development

Podestà,

Cruz-Zabala,

Poli

et al. 2024

Plasma Phys. Control. Fusion

Self Cite

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Thermionic emission of a tungsten surface in high heat flux plasma: PIC simulations

Moritz,

Heuraux,

Lemoine

et al. 2023

Physics of Plasmas

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The surface temperature of a tungsten surface facing hot hydrogen plasma is evaluated, thanks to 1d/3v particle-in-cell simulations in floating wall conditions. At each iteration, the plasma heat flux to the cathode is equalized with the outgoing one, which is due to thermionic emission, surface radiation, and heat conduction through the wall. The thermal conductivity is chosen within the range 35–160 W m−1 K−1 in the different simulations in order to take into account the surface condition. A transition from a cold temperature surface to a hot one arises for a critical thermal conductivity, whose value depends on the plasma parameters. This transition is very abrupt and leads to a space charge limited regime where the thermionic current penetrating the plasma has reached its maximal value and is about three times the Bohm current. Changing the initial conditions in the code, more particularly, the timing of electron emission, can lead to a very different final surface temperature. This history effect and the associated hysteresis are evidenced by means of fluid calculations, which are in a good agreement with the simulation results as well as with previous experimental measurements.

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NSTX-U research advancing the physics of spherical tokamaks

Berkery,

Adebayo-Ige,

Al Khawaldeh

et al. 2024

Nucl. Fusion

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The objectives of NSTX-U research are to reinforce the advantages of STs while addressing the challenges. To extend confinement physics of low-A, high beta plasmas to lower collisionality levels, understanding of the transport mechanisms that set confinement performance and pedestal profiles is being advanced through gyrokinetic simulations, reduced model development, and comparison to NSTX experiment, as well as improved simulation of RF heating. To develop stable non-inductive scenarios needed for steady-state operation, various performance-limiting modes of instability were studied, including MHD, tearing modes, and energetic particle instabilities. Predictive tools were developed, covering disruptions, runaway electrons, equilibrium reconstruction, and control tools. To develop power and particle handling techniques to optimize plasma exhaust in high performance scenarios, innovative lithium-based solutions are being developed to handle the very high heat flux levels that the increased heating power and compact geometry of NSTX-U will produce, and will be seen in future STs. Predictive capabilities accounting for plasma phenomena, like edge harmonic oscillations, ELMs, and blobs, are being tested and improved. In these ways, NSTX-U researchers are advancing the physics understanding of ST plasmas to maximize the benefit that will be gained from further NSTX-U experiments and to increase confidence in projections to future devices.

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Reduced physics model of the tokamak Scrape-Off-Layer for pulse design

Cited by 3 publications

References 23 publications

NBI optimization on SMART and implications for scenario development

NBI optimization on SMART and implications for scenario development

Thermionic emission of a tungsten surface in high heat flux plasma: PIC simulations

NSTX-U research advancing the physics of spherical tokamaks

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