H. Arnichand
A5068252787- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Superconducting Materials and Applications
- High-Energy Particle Collisions Research
- Nuclear Physics and Applications
- Atomic and Molecular Physics
- Wind and Air Flow Studies
- Laser-Matter Interactions and Applications
- Solar and Space Plasma Dynamics
- Nuclear reactor physics and engineering
- Particle Accelerators and Free-Electron Lasers
École Polytechnique Fédérale de Lausanne
2019-2025
Royal Military Academy
2020
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2011-2017
CEA Cadarache
2011-2017
Institut de Recherche sur la Fusion par Confinement Magnétique
2015
The 2014–2016 JET results are reviewed in the light of their significance for optimising ITER research plan active and non-active operation. More than 60 h plasma operation with first wall materials successfully took place since its installation 2011. New multi-machine scaling type I-ELM divertor energy flux density to is supported by principle modelling. relevant disruption experiments modelling reported a set three mitigation valves mimicking setup. Insights L–H power threshold Deuterium...
Abstract The tokamak à configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system address critical issues in preparation for ITER a fusion power plant. For the 2019–20 campaign configurational flexibility has been enhanced with installation of removable divertor gas baffles, diagnostic capabilities an extensive set upgrades new dual frequency gyrotrons. baffles reduce coupling between main chamber allow detailed...
This letter reports on quasi-coherent (QC) modes observed in fluctuation spectra from Tore Supra and TEXTOR reflectometers. QC have characteristics between coherent broad-band fluctuations as they oscillate around a given frequency but wide spectrum. They are ballooned at the LFS midplane appear usually ranging 30 to 120 kHz. In ohmic plasmas both tokamaks, detected only linear confinement (LOC) regime disappear saturated (SOC) regime. Linear simulations predict that LOC SOC regimes...
Abstract The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, exploratory plasmas driven by theoretical insight, exploiting device’s unique shaping capabilities. Disruption avoidance real-time locked mode prevention or unlocking with electron-cyclotron resonance heating (ECRH) was thoroughly documented, using magnetic radiation triggers. Runaway generation high- Z noble-gas injection runaway dissipation...
Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle role plasma fueling shape for onset small ELM regimes. On both devices, regimes with high confinement are achieved if only two conditions fulfilled at same time. Firstly, density separatrix must be large enough (), leading pressure profile flattening separatrix, which stabilizes type-I ELMs. Secondly, magnetic configuration close double null (DN), reduction shear in...
Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat particle loads on wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research ASDEX Upgrade (AUG), MAST TCV. This multi-machine approach within EU-MST, covering wide parameter range, instrumental progress in field, as ITER DEMO core/pedestal SOL parameters are not achievable simultaneously present day devices. A two prong adopted. On one...
Ion temperature gradient (ITG) and trapped electron modes (TEM) are two important micro-instabilities in the plasma core region of fusion devices (). They usually coexist same range spatial scale (around ), which makes their discrimination difficult. To investigate them, one can perform gyrokinetic simulations, transport analysis phase velocity estimations. In Tore Supra, identification is made possible due to measured frequency fluctuation spectra. Indeed, turbulent spectra generally...
Quasi-coherent (QC) modes have been reported for more than 10 years in reflectometry fluctuations spectra the core region of fusion plasmas. They characteristics in-between coherent and broadband as they oscillate at a marked frequency but wide spectrum. This work presents further evidences link recently established between QC trapped electron (TEM) instabilities (Arnichand et al 2014 Nucl. Fusion 54 123017). In cyclotron resonance heated discharges Tore Supra, an enhancement amplitude is...
This work reports developments of the incoherent TS diagnostic capabilities in Tokamak à Configuration Variable (TCV). Their goals are to (i) diagnose TCV divertor region, and (ii) provide Te ne profiles plasma bulk real-time. These two new implemented within framework a upgrade that will insert baffles lower region. 20 spectrometers being installed access electron temperatures down ~1 eV, for densities above ~1.5×1019m−3 They measure Thomson light scattered along vertical propagation path...
The ultrafast sweep reflectometry technique is used to investigate plasma turbulence on Tore Supra.Thanks the X-mode polarization, density and fluctuations over whole tokamak radius, from far scrape-off layer (SOL) core can be measured.Cross-correlation analysis applied all signal components estimate fluctuation correlation length radial profile.The decreases centre last closed flux surface grows again into SOL.
The effect of plasma density on toroidal rotation was examined in ramp-up experiments at a current 1 MA and magnetic field 3.6 T Tore Supra ohmic discharges. Experimental measurements have shown that the amplitude is reduced all radii when increasing density, although it remains counter-current direction. Neoclassical predictions including ripple-induced friction are qualitative agreement with such observations. However, core (r/a < 0.5) accelerates nl ~ 3 × 1019 m−2 breaks again above 3.5...
The paper reports on the first measurements of long-range correlations along field lines in center ohmic plasmas at TEXTOR. are performed with correlation reflectometry. For time poloidal, toroidal and radial extension quasi-coherent modes simultaneously investigated using reflectometry two poloidally toroidally separated positions. experiments also allow local determination velocity from a combination delay estimation safety factor same instrument. investigates whether turbulence which kind...
In order to better study conventional and alternative divertor configurations, the TCV Tokamak was recently upgraded. In-vessel graphite baffles were installed in chamber delimit a separate from core that required enhanced diagnostic capabilities. To date, TCV's Thomson scattering provided electron temperature density profiles of hot pedestal plasma with an array 96 polychromators. new region, upgrade added 20 polychromators specifically diagnose relatively cold region. New 4-channel...
The observation of distinct peaks in tokamak core reflectometry measurements - named quasi-coherent-modes (QCMs) are identified as a signature Trapped-Electron-Mode (TEM) turbulence [H. Arnichand et al. 2016 Plasma Phys. Control. Fusion 58 014037]. This phenomenon is investigated with detailed linear and nonlinear gyrokinetic simulations using the \gene code. A Tore-Supra density scan studied, which traverses through Linear (LOC) to Saturated (SOC) Ohmic Confinement transition. LOC SOC...
The possibility of performing electron density and temperature measurements in a high power helicon plasma is crucial issue the framework AWAKE (Advanced WAKefield Experiment) project, which demonstrates acceleration particles using $\text{GeV}~\text{m}^{-1}$ electric fields plasmas. For AWAKE, currently envisaged as candidate source due to its capability for low ion temperature, production an elongated column. A diagnostic accurately determine regimes would be valuable supporting tool....
This paper reports on a simulation of reflectometry measurement in Tore Supra ohmic discharges, for which the experimental observations as well gyrokinetic non-linear computations predict modification turbulence spectrum between linear (LOC) and saturated confinement (SOC) regimes. Synthetic simulations coupling full-wave with data are carried out. allows direct comparison predictions observations. The synthetic diagnostic results found good agreement findings; particular, they reproduce...
This paper develops a global model based on non-local properties of fractional derivatives for fusion plasmas. The results confirm that transport in the largest device i.e. JET, is better predicted. expected to provide an insight proper kinetic description plasmas, and improve accuracy predictions.
Abstract The beams of fast runaway electrons (RE), which are often produced during tokamak discharges, particularly dangerous and can induce serious damages the vacuum vessel internal components machine. proper diagnostics RE is essential for controlling discharge, e.g., by early mitigation disruptions potentially beams. usually based on measurements radiation emitted either these electrons, or as a result their interactions with plasma and/or walls. Such recorded means probes placed outside...