Impact of triangularity on power sharing and boundary turbulence in TCV double-null L-mode plasmas

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Suprathermal ions, i.e. ions with energies exceeding those of the bulk plasma, arise in diverse natural and laboratory plasmas ranging from the solar wind to magnetic confinement fusion (MCF) devices. In tokamaks, they are generated by external heating systems and fusion reactions, and a thorough characterization of their dynamics is crucial for safe operation. In tokamaks, the core plasma is separated from the walls by the last closed flux surface (LCFS), which exhibits a null point (X-point) in the poloid

The comparison of simulations of plasma turbulence carried out with the GBS code, employing its latest multi-component plasma–neutral model, against a dedicated set of TCV discharges (TCV-X23) designed to investigate high-density divertor conditions characterised by strongly reduced target heat flux with respect to attached conditions, is presented. The TCV-X23 scenario, based on L-mode plasmas with a long outer divertor leg at low toroidal field, provides a well-diagnosed reference for boundary turbule

In this work, we compare physics-based dynamic exhaust models with frequency response measurements (FRMs) of the global particle dynamics in the Tokamak à Configuration Variable (TCV). The aim is to understand and model the experimental in-vessel dynamic response of plasma and neutrals to deuterium gas puff modulations with three models of varying fidelity: a 0D three chamber model (TCM); DIV1D, which models the edge plasma in 1D, and SOLEDGE3X for 2D-axisymmetric modeling. We find that the dynamic behavior

Negative triangularity (NT) plasmas achieve enhanced confinement without edge localized modes nor the need to exceed the L-H heating power threshold. Removing this H-mode accessibility constraint opens a new region of parameter space: scenarios with low external heating power. Using simple zero dimensional power balance and standard empirical scaling laws for confinement, we analyze the impact of external heating on several different reactor-relevant devices (i.e. SPARC, MANTA, ITER and DEMO). We determine

An integrated numerical system is established to model time-dependent behavior of the neoclassical tearing mode (NTM) in a tokamak which solves the modified Rutherford equation (MRE) by coupling with plasma transport, equilibrium, heating and current drive ...

Generally, the more an underlying terrain deviates from being flat, uniform and homogeneous, the less that classical theories and models of the atmospheric boundary layer hold. At times this leads to high uncertainties in turbulent flux predictions, and at other times the models completely break down. Hence, to better understand, model and subsequently predict surface turbulent exchanges over non-idealized terrain, an important objective of many recent field campaigns has been to investigate the near-surfac

The understanding of the plasma dynamics in the scrape-off layer (SOL) of tokamaks is of crucial importance as we approach the ITER era. In this region, particles and heat coming from the core, through turbulent transport, flow along the magnetic field lines and are exhausted to the vessel. The processes taking place in the SOL govern the performance of the entire device, as they determine the impurity dynamics, the recycling level, the peak heat loads at the vessel, and have an important role in setting th

Negative triangularity tokamak plasmas are subject of an increased interest both in existing experiments and in studies of core physics as well as power handling relevant to the fusion demonstration power reactor. The ideal MHD stability calculations for the negative triangularity plasma extend the investigation of the TCV tokamak beta limits and edge stability to double null shapes, lower aspect ratio and negative shear. In case of the negative triangularity, the 2nd stability access is closed for ballooni

The TORoidal Plasma EXperiment (TORPEX) is a Simple Magnetized Torus (SMT) where open helical magnetic field lines are obtained from the superposition of a small vertical component on the main toroidal field. The SMT configuration features the main driving mechanisms of plasma instabilities characterising the Scrape-Off Layer (SOL) of larger tokamak devices, making TORPEX a very attractive machine to perform fusion oriented studies of plasma turbulence. A new experimental set-up has been recently developed

In the sheath region at the interface between plasmas and solid surfaces, quasi-neutrality and, in the case of magnetized plasmas, drift-ordering are violated. These two assumptions are typically made in plasma fluid models; the presence of a plasma-wall transition region, typical of all bounded systems, hampers therefore their use. This problem can be overcome by introducing a set of boundary conditions (BCs) for fluid models that properly describe the physics of the plasma-wall transition region. While th

To measure the transport of fast ions by various types of waves, complementary experiments are conducted in linear and toroidal magnetic fields in the large plasma device and the toroidal plasma experiment. Lithium sources that are immersed in the plasma p ...

We investigate the redistribution of the neutral beam driven current in the presence of small scale turbulence in the ITER steady-state scenario. Gyrokinetic simulations show that anomalous transport of beam ions can be larger than collisional estimates. T ...

We have investigated the effect of different ion cyclotron resonance frequency (ICRF) heating schemes, of error field modes, of the plasma shape and edge magnetic shear, and of the ion delB drift direction on the stability of Alfven eigenmodes (AEs). The use of multi-frequency or 2nd harmonic minority ICRF heating at high plasma density gives rise to a lower fast ion pressure gradient in the plasma core and to a reduced mode activity in the Alfven frequency range. Externally excited low-amplitude error fiel

The particle confinement in a magnetized plasma torus with superimposed vertical magnetic field is modeled and measured experimentally. The formation of an equilibrium characterized by a parallel plasma current canceling out the grad B and curvature drifts is described using a two-fluid model. Characteristic response frequencies and relaxation rates are calculated. The predictions for the particle confinement time as a function of the vertical magnetic field are verified in a systematic experimental study o

In small area capacitive reactors, the rf and dc components of the plasma potential can be assumed to be uniform over all the plasma bulk because of the low plasma resistivity. In large area reactors, however, the rf plasma potential can vary over a long range across the reactor due to rf current flow and the nonzero plasma impedance. A perturbation in rf plasma potential, due to electrode edge asymmetry or the boundary of a dielectric substrate, propagates along the resistive plasma between capacitive shea

In the scope of the study of low-frequency electrostatic microinstabilities in tokamak plasmas, attention has been focused on the effect of trapped ions. The ballooning transform has been applied to the gyrokinetic equation, for the case of a large aspect ratio plasma with circular magnetic surfaces. A new eigenvalue code has been developed to solve the resulting integral equation, for the case of adiabatic electrons and full ion dynamics, thus taking into account both circulating and trapped ions. The goal

A solution to the full two-dimensional eigenvalue problem of electrostatic microinstabilities in a tokamak plasma is presented in the framework of gyrokinetic theory. The approach is the generalization of methods previously developed for a cylindrical system [S. Brunner and J. Vaclavik, Phys. Plasmas 5, 365 (1998)]. By solving the spectral problem in a special Fourier space adapted to the curved geometry, orbit width as well as Larmor radius can be kept to all orders. For a first numerical implementation, a

We have investigated the topological modification of an equilibrium with nested magnetic flux surfaces computed with the free boundary variational moments equilibrium code (VMEC) subject to an applied magnetic field perturbation. Magnetic field lines are traced in the domain interior to the plasma-vacuum interface either in the coordinates of the VMEC (s, u, v) or using canonical coordinates (psi, theta*, v) that allow a Hamiltonian description of the magnetic field lines. The perturbation models the effect

The stability of the vertical position control system in TCV is analysed using two different plasma models, a deformable plasma model (DPM) and a rigid plasma model (RPM). The open loop growth rates and closed loop stability are computed, as functions of various plasma parameters, for both models. It is found that the difference between the open loop growth rates predicted by the two models depends significantly on plasma elongation and triangularity. Growth rates are also computed using the NOVA-W code, an

During plasma excitation by high power Alfven waves at TCA, signals at harmonics of the generator frequency are observed in the plasma scrape-off layer. In this paper, experimental investigations of the sheath effect and the excitation efficiency and dispersion properties of the harmonics are reported. The results indicate that the harmonics arise, either directly or indirectly, through the driven Alfven waves and not through the sheath effect at the exciting antenna. The RF ion saturation current is observ

Impact of triangularity on power sharing and boundary turbulence in TCV double-null L-mode plasmas

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Fast ion transport in complex magnetic field configurations in TORPEX

Power exhaust and detachment with varying outer leg length using turbulence simulations and experiments designed for validation

A multi-model system-identification comparison with the global particle dynamics in TCV

On the feasibility of Ohmically heated negative triangularity tokamak power plants

Modeling of neoclassical tearing mode stabilization by electron cyclotron heating and current drive in tokamak plasmas

Counter-Gradient, Co-Gradient and ‘Surface-Layer' Momentum Fluxes in Nocturnal Slope Flows over Steep Alpine Terrain

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Stability limits for tokamak plasma with negative triangularity

Study of plasma fluctuations in new closed flux-surface configurations of the TORPEX experiment

The role of the sheath in magnetized plasma fluid turbulence

Measurements of interactions between waves and energetic ions in basic plasma experiments

Numerical modelling of electromagnetic turbulent transport of energetic ions in burning plasmas

Alfven mode stability and wave-particle interaction in the JET tokamak: prospects for scenario development and control schemes in burning plasma experiments

Effects of a vertical magnetic field on particle confinement in a magnetized plasma torus

Nonuniform radio-frequency plasma potential due to edge asymmetry in large-area radio-frequency reactors

Applicability of the ballooning transform to trapped ion modes

Global approach to the spectral problem of microinstabilities in tokamak plasmas using a gyrokinetic model

Topologic study of a magnetic perturbation in a 3D free boundary plasma equilibrium

Stability analysis of the vertical position control loop in TCV using rigid and deformable plasma models

An Experimental-Study of the Harmonics Generated During Alfven-Wave Heating at Tca