Tangential phase-contrast imaging for fluctuation measurements in JT–60SA: a conceptual study

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In this work, we extend our previous studies (Singh et al 2023, Nucl. Fusion 63, 086029; Singh et al 2024, Nucl. Fusion 64, 106005) by performing global δf electromagnetic gyrokinetic simulations including collisions using the ORB5 particle-in-cell (PIC) code, spanning the plasma from magnetic axis to separatrix. The analysis focuses on ion temperature gradient (ITG) and trapped electron mode (TEM) turbulence in both linear and nonlinear regimes for experimentally relevant profiles and parameters of the ADI

The EC Upper Launcher (UL) and Ex-vessel waveguide (EW) are integral components of the ITER Electron Cyclotron (EC) system [1], which plays a key role in achieving and maintaining the high temperatures required for nuclear fusion within the tokamak, providing plasma heating and current drive, and magnetohydrodynamics (MHD) stabilization, which are crucial for ITER’s operational success. The EC system is increasingly becoming the reference mechanism for plasma heating in both present and future devices. Nota

Screening of high-Z (W) impurities from the confined plasma by the temperature gradient at the plasma periphery of fusion-grade H-mode plasmas was demonstrated for the first time in JET with the Be/W wall (Field et al 2023 Nucl. Fusion 63 016028). Additional experiments have been performed in JET during 2023, including in deuterium-tritium (DT) during the DTE3 campaign, to further optimise the impurity screening in such plasmas, as well as our bolometric measurements of the W impurity fluxes between and dur

Since the discovery of two-dimensional magnetic materials in 2017, an uncharted territory has opened within the field of spintronics, drawing intense interest from both experimental and computational research. From a computational perspective, studying magnetic materials requires addressing several challenges: achieving accurate simulations of localized electrons, identifying the ground state magnetic ordering, determining the parameters of effective Hamiltonians, such as Hubbard parameters or exchange inte

At the intersection of computational imaging and biomedical optics, this thesis applies physics-based modeling and computational methods to solve inverse problems in optical imaging. We focus on three representative imaging modalities where we push the limits of imaging depth and spatial resolution: optical projection tomography (OPT); photoacoustic imaging (PAI); and single-molecule localization microscopy (SMLM). OPT and PAI overcome the diffusion limit to enable greater imaging depths, while SMLM breaks

This thesis presents a study on the statistical characterization and predictability of plasma discharges in the TCV tokamak, based on time-dependent transport simulations performed with the ASTRA code. The work combines physical modeling, numerical implementation, and nonlinear time-series analysis to bridge the gap between transport simulations and the dynamical complexity of experimentally observed plasma behavior.

Motivated by the recent observation of a uniform vector chirality (UVC) magnetic order in the maple-leaf lattice (MLL) realization

\mathrm{Ho_3ScO_6}

via powder neutron scattering experiments, we investigate the classical antiferromagnetic Heisenberg model on the maple-leaf lattice. The MLL features three symmetry-inequivalent nearest-neighbor couplings,

J_d

J_t

, and

J_h

. Previous studies, primarily focused on the case where

J_t = J_h

, identified a staggered vector chirality (SVC) order. Extendin

Research into mesoscopic magnetic systems, which incorporate magnetic elements with dimensions ranging from a few nm up to a few 10s of micrometer, has been spurred on by the developments in their fabrication, characterisation, and control. Electron beam and optical lithography are key methods for their fabrication because they can be used to create tailor- made planar arrangements of elements or more complex layered structures. These can be further transformed into high quality three-dimensional mesoscale

A novel first-principles self-consistent model that couples plasma and neutral atom physics suitable for the simulation of turbulent plasma behaviour in the tokamak edge region has been developed and implemented in the GBS code. While the plasma is modelled by the drift-reduced two fluid Braginskii equations, a kinetic model is used for the neutrals, valid in short and in long mean free path scenarios. The model includes ionization, charge-exchange, recombination, and elastic collisional processes. The mode

The effect of the limiter position on the scrape-off layer (SOL) width, radial electric field and intrinsic flows is investigated via global, three-dimensional turbulence simulations in four different limiter configurations. The limiter position affects the SOL dynamics in a number of ways, for example by changing the effective connection length or by modifying the unstable modes present in the system. The simulations show that the SOL width is much smaller and less poloidally asymmetric when the plasma is

A detailed study of the operational capabilities of the W7-X/1MW gyrotron operated at 126GHz/TE26,7 is presented. This study is associated with the foreseen upgrade of TCV in which it is planned to add to the present EC system 3MW of additional RF power bringing the total EC-power to 7.5MW. This study is extended to a possible operation of the gyrotron at the ITER relevant frequency of 168GHz in the TE35,9 mode without implementing any further modification neither in the gyrotron nor in the gyrotron superco

In the search of a fusion reactor using magnetic confinement of toroidal plasmas, many important plasma performance parameters directly depend on the shape of the plasma cross-section. The unique shaping capability of the TCV tokamak ("Tokamak à Configuration Variable") has been exploited to study different aspects of tokamak transport and stability, in which the plasma shape may play a role. This presentation will focus on the effects of plasma shape on transport. The TCV tokamak has produced a host of phy

All tokamak experiments using ECCD require setting of the beam elliptical polarization for proper coupling to the plasma. This is done either in the matching optics unit (MOU) at the output of the gyrotron, or in a couple of miter bends of the transmission line. Similarly, oblique ECE receivers require selection of the correct elliptical polarization to provide localized measurements. For the TCV tokamak at the CRPP, gyrotron and oblique-ECE polarizers are characterized during either high- or low- power tes

The existence of a critical pressure gradient needed to drive the interchange instability is experimentally demonstrated in the simple magnetized torus TORoidal Plasma EXperiment [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)]. This gradient is reached during a scan in the neutral gas pressure pn. Around a critical value for pn, depending on the magnetic configuration and on the injected rf power, a small increase in the neutral gas pressure triggers a transition in the plasma behavior. The pressure pro

We present applications of a recently developed method, the singular value decomposition inversion (SVD-I), for inverting line integrated multichannel interferometer measurements in fusion devices. The method expands the local electron density profiles into a limited series of orthogonal basis functions formed from the singular value decomposition of Thomson scattering measurements, which are obtained at much lower frequencies than the interferometer data. Because these basis functions are formed from a loc

Electron cyclotron current drive (ECCD) is an important prospective tool for tailoring the current profile in nextstep devices. To fill the remaining gaps between ECCD theory and experiment, especially in the efficiency and localization of current drive, a better understanding of the physics of suprathermal electrons appears necessary. In TCV the fast electron population is diagnosed by a multichordal, spectrometric hard x-ray camera and by a highfield side electron cyclotron emission radiometer. The main m

Localized direct electron heating (EH) by mode-converted (MC) ion cyclotron range of frequencies (ICRF) waves in D(H) tokamak plasmas has been clearly observed for the first time in Alcator C-Mod. Both on- and off-axis (high field side) mode conversion EH (MCEH) have been observed. The MCEH profile was obtained from a break-in-slope analysis of electron temperature signals in the presence of radio frequency shut-off. The temperature was measured by a 32-channel high spatial resolution (less than or equal to

Localized electron heating and current drive, like those produced by electron cyclotron heating (ECH) systems, are powerful tools for controlling the sawtooth period. They allow the direct modification of the plasma parameters which determine the sawtooth stability. In this paper we report a set of new experimental results obtained in the TokamakConfiguration Variable (TCV) and a set of related simulations obtained applying a sawtooth period model in a transport code. The TCV device, equipped with a very fl

A new understanding of edge localized modes (ELMs) in tokamak discharges is emerging (Snyder P B et al 2002 Phys. Plasmas 9 2037), in which the ELM is an essentially ideal magnetohydrodynamic (MHD) instability and the ELM severity is determined by the radial width of the linearly unstable MHD kink modes. A detailed, comparative study of the penetration into the core of the respective linear instabilities in a standard DIII-D ELMing, high confinement mode (H-mode) discharge, with that for two relatively high

The infrared (IR) absorption of a biological system can potentially report on fundamentally important microchemical properties. For example, molecular IR profiles are known to change during increases in metabolic flux, protein phosphorylation, or proteolytic cleavage. However, practical implementation of intracellular IR imaging has been problematic because the diffraction limit of conventional infrared microscopy results in low spatial resolution. We have overcome this limitation by using an IR spectroscop

Tangential phase-contrast imaging for fluctuation measurements in JT–60SA: a conceptual study

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Electromagnetic gyrokinetic simulation of drift wave turbulence in ADITYA-U with collisions

The design of the EC Upper Launcher and Ex-vessel waveguide systems for ITER

Optimised 'hybrid' Scenario H-mode Plasmas for W Radiation Control in Jet with the Be/w Wall

Two-dimensional magnetic materials from first principles

Physics-based modeling and inverse problems in optical imaging

Statistical Analysis of Plasma Discharge Predictability in Transport Simulations of TCV Experiments

Chiral crossroads in Ho3ScO6 : Competing interactions on the maple-leaf lattice

Mesoscopic magnetic systems: From fundamental properties to devices

Interaction of neutral atoms and plasma turbulence in the tokamak edge region

Effect of the limiter position on the scrape-off layer width, radial electric field and intrinsic flows

Design studies of the dual-frequency operation of the W7-X/140GHz/1MW gyrotron at 126GHz for TCV and 168GHz for ITER

Physics Insight from Plasma Shaping of TCV Tokamak Plasmas - focus on Electron Heat Transport

Polarization Issues with High Power Injection and Low Power Emission in Fusion Experiments

Observation of a critical pressure gradient for the stabilization of interchange modes in simple magnetized toroidal plasmas

Application of the singular value decomposition method for inversion of interferometer measurements in fusion plasmas

Electron cyclotron current drive and suprathermal electron dynamics in the TCV tokamak

Ion cyclotron range of frequencies mode conversion electron heating in deuterium-hydrogen plasmas in the Alcator C-Mod tokamak

Effects of localized electron heating and current drive on the sawtooth period

Edge localized modes in DIII-D high performance discharges

Chemically resolved imaging of biological cells and thin films by infrared scanning near-field optical microscopy