Alexandre Fil

Alexandre Fil
United Kingdom Atomic Energy Authority, CCFE · Tokamak Science

PhD in Plasma Physics (Disruption modeling) - Diplôme de l'Ecole Normale Supérieure de Paris
Runaway Electron Physicist at UKAEA

About

69
Publications
15,048
Reads
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875
Citations
Introduction
Runaway Electron generation and mitigation in spherical tokamaks, including STEP
Additional affiliations
January 2020 - April 2020
United Kingdom Atomic Energy Authority
Position
  • Pedestal MHD modeller
February 2017 - January 2020
The University of York
Position
  • Research Associate
Description
  • Based at the Culham Centre for Fusion Energy, Abingdon, Oxfordshire.
October 2015 - January 2017
Princeton University
Position
  • Research Associate
Education
September 2012 - September 2015
Aix-Marseille Université
Field of study
  • Plasma Physics
September 2009 - August 2012
September 2006 - August 2012
Sorbonne Université
Field of study
  • Physics - M@ Fusion Science

Publications

Publications (69)
Preprint
Understanding generation and mitigation of runaway electrons in disruptions is important for the safe operation of future tokamaks. In this paper we investigate runaway dynamics in reactor-scale spherical tokamaks. We study both the severity of runaway generation during unmitigated disruptions, as well as the effect that typical mitigation schemes...
Article
Full-text available
MAST-U has recently started operating with a Super-X divertor, designed to increase total flux expansion and neutral trapping, both predicted through simple analytic models and SOLPS calculations to reduce the plasma and impurity density detachment thresholds. In this study, utilising the SOLPS-ITER code, we are quantifying the possible gain allowe...
Article
In nuclear fusion reactors, plasmas are heated to very high temperatures of more than 100 million kelvin and, in so-called tokamaks, they are confined by magnetic fields in the shape of a torus. Light nuclei, such as deuterium and tritium, undergo a fusion reaction that releases energy, making fusion a promising option for a sustainable and clean e...
Article
Alpha particles with energies on the order of megaelectronvolts will be the main source of plasma heating in future magnetic confinement fusion reactors. Instead of heating fuel ions, most of the energy of alpha particles is transferred to electrons in the plasma. Furthermore, alpha particles can also excite Alfvénic instabilities, which were previ...
Preprint
Full-text available
We present the first analysis of the atomic and molecular processes at play during detachment in the MAST-U Super-X divertor using divertor spectroscopy data. Our analysis indicates detachment in the MAST-U Super-X divertor can be separated into four sequential phases: First, the ionisation region detaches from the target at detachment onset leavin...
Preprint
Full-text available
We present the first analysis of the atomic and molecular processes at play during detachment in the MAST-U Super-X divertor using divertor spectroscopy data. Our analysis indicates detachment in the MAST-U Super-X divertor can be separated into four sequential phases: First, the ionisation region detaches from the target at detachment onset leavin...
Article
Full-text available
The tokamak à configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system to address critical issues in preparation for ITER and a fusion power plant. For the 2019–20 campaign its configurational flexibility has been enhanced with the installation of removable divertor gas b...
Preprint
Full-text available
MAST-U has recently started operating with a Super-X divertor, designed to increase total flux expansion and neutral trapping, both predicted through simple analytic models and SOLPS calculations to reduce the plasma and impurity density detachment thresholds. In this study, utilising the SOLPS-ITER code, we are quantifying the possible gain allowe...
Article
Full-text available
A reduction of the pedestal pressure with increasing separatrix density over pedestal density ( n e sep / n e ped ) has been observed in JET. The physics behind this correlation is investigated. The correlation is due to two distinct mechanisms. The increase of n e sep / n e ped till ≈0.4 shifts the pedestal pressure radially outwards, decreasing t...
Preprint
Full-text available
This paper shows experimental results from the TCV tokamak that indicate plasma-molecule interactions involving $D_2^+$ and possibly $D^-$ play an important role as sinks of energy (through hydrogenic radiation as well as dissociation) and particles during divertor detachment if low target temperatures (< 3 eV) are achieved. Both molecular activate...
Presentation
Full-text available
Online poster presentation for the 28th IAEA Fusion Energy Conference on the impact of plasma-atom/molecule interactions on power and particle balance.
Article
Full-text available
JOREK is a massively parallel fully implicit non-linear extended magneto-hydrodynamic (MHD) code for realistic tokamak X-point plasmas. It has become a widely used versatile simulation code for studying large-scale plasma instabilities and their control and is continuously developed in an international community with strong involvements in the Euro...
Preprint
Full-text available
This paper shows experimental results from the TCV tokamak that indicate plasma-molecule interactions involving D2+ and possibly D- play an important role as sinks for energy and particles during divertor detachment if low target temperatures (< 3 eV) are achieved. Both molecular activated recombination (MAR) and ion source loss due to a power limi...
Article
Full-text available
In this work we provide experimental insights into the impact of plasma-molecule interactions on the target ion flux decrease during divertor detachment achieved through a core density ramp in the TCV tokamak. Our improved analysis of the hydrogen Balmer series shows that plasma-molecule processes are strongly contributing to the Balmer series inte...
Presentation
Full-text available
Invited talk at the PSI 2020 conference on an experimental investigation on the impact of plasma-molecule interactions on detachment using spectroscopy data from the TCV tokamak. We find that during detachment the Halpha emission increases strongly beyond expectations of atomic interactions, indicative of plasma-molecule interactions (particularly...
Article
Full-text available
Detachment, an important mechanism for reducing target heat deposition, is achieved through reductions in power, particle and momentum; which are induced through plasma–atom and plasma–molecule interactions. Experimental research in how those reactions precisely contribute to detachment is limited. Both plasma–atom as well as plasma–molecule intera...
Preprint
Full-text available
JOREK is a massively parallel fully implicit non-linear extended MHD code for realistic tokamak X-point plasmas. It is a widely used versatile code for studying large-scale plasma instabilities and their control and is continuously developed in an international community with strong involvements in European fusion research. This article gives a com...
Preprint
Full-text available
Detachment, an important mechanism for reducing target heat deposition,is achieved through reductions in power, particle and momentum; which are induced through plasma-atom and plasma-molecule interactions. Experimental research in how those reactions precisely contribute to detachment is limited. In this work, we investigate a new spectroscopic te...
Preprint
Full-text available
In this work we provide experimental insights into the impact of plasma-molecule interactions on the target ion flux decrease during divertor detachment achieved through a core density ramp in the TCV tokamak. Our improved analysis of the hydrogen Balmer series shows that plasma-molecule processes are strongly contributing to the Balmer series inte...
Article
The high heat fluxes to the divertor during edge localised mode (ELM) instabilities have to be reduced for a sustainable future tokamak reactor. A solution to reduce the heat fluxes could be the Super-X divertor, which will be tested on MAST-U. ELM simulations for MAST-U Super-X tokamak plasmas have been obtained, using JOREK. A factor 10 decrease...
Article
Total flux expansion, a divertor magnetic topology design choice embodied in the Super-X divertor, is predicted through simple analytic models and SOLPS calculations to reduce the plasma and impurity density detachment thresholds as the outer divertor separatrix leg position and the strike-point major radius, Rt, are increased. However, those predi...
Poster
Full-text available
Poster on experimental inference of ion sources/ion sinks and power losses due to atomic and molecular reactions in the TCV divertor. The main conclusions are that: - The inclusion of these reactions in plasma-modelling codes may be limited, which is important for extrapolating to DEMO - Plasma-molecule interactions can result in: 1) Significant...
Article
Full-text available
The physics of divertor detachment is determined by divertor power, particle and momentum balance. This work provides a novel analysis technique of the Balmer line series to obtain a full particle/power balance measurement of the divertor. This supplies new information to understand what controls the divertor target ion flux during detachment. Ato...
Preprint
Total flux expansion, a divertor magnetic topology design choice embodied in the Super-X divertor, is predicted through simple analytic models and SOLPS calculations to reduce the plasma and impurity density detachment thresholds as the outer divertor separatrix position, Rt, is increased. However, those predictions are contradicted by recent TCV e...
Article
Results from two different sets of JET experiments are presented. In experiments in which toroidicity-induced Alfven eigenmodes (TAEs) localized at different radial locations had the same frequencies and toroidal mode numbers, the occurrence of enhanced losses after the excitation of TAEs in the core of the plasma was observed. On the contrary, enh...
Conference Paper
Full-text available
The process of divertor detachment, whereby heat and particle fluxes to divertor surfaces are strongly reduced, is required to reduce heat loading and erosion in a magnetic fusion reactor. In previous research [1], we have provided a full interpretation of particle/power balance in the TCV divertor using spectroscopic techniques assuming atomic rea...
Article
Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the pla...
Article
Full-text available
Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the pla...
Article
The mega amp spherical tokamak (MAST) was a low aspect ratio device (R/a = 0.85/0.65 ∼ 1.3) with similar poloidal cross-section to other medium-size tokamaks. The physics programme concentrates on addressing key physics issues for the operation of ITER, design of DEMO and future spherical tokamaks by utilising high resolution diagnostic measurement...
Preprint
The process of divertor detachment, whereby particle fluxes to divertor surfaces are strongly reduced, is required to reduce heat loading and erosion in a magnetic fusion reactor. The ions reaching the target during divertor detachment are primarily generated in the divertor (ion source), which costs energy. In addition, there can be additional ion...
Article
Full-text available
The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, to exploratory plasmas driven by theoretical insight, exploiting the device's unique shaping capabilities. Disruption avoidance by real-time locked mode prevention or unlocking with electron-cyclotron resonance hea...
Poster
Full-text available
In this work the physics leading to the decrease of the TCV tokamak divertor ion flux, or ‘roll-over’, is experimentally explored through characterization of the location, magnitude and role of the various divertor ion sinks and sources including a complete measure of particle and power balance. Profiles of divertor ionisation rates and hydrogenic...
Preprint
Full-text available
The process of divertor detachment, whereby heat and particle fluxes to divertor surfaces are strongly reduced, is required to reduce heat loading and erosion in a magnetic fusion reactor. In this paper the physics leading to the decrease of the TCV tokamak divertor ion flux, or 'roll-over', is experimentally explored through characterization of th...
Article
Using SOLPS-ITER, we model a TCV conventional divertor discharge density ramp to understand the role of various processes in the loss of target ion current. We find that recombination is not a strong contributor to the rollover of the target ion current at detachment. In contrast, the divertor ion source appears to play a central role in magnitude...
Article
Full-text available
The 2014–2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to...
Article
The ASDEX Upgrade (AUG) programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. Since 2015, AUG is equipped with a new pair of 3-strap ICRF antennas, which were designed for a reduction of tungsten release during ICRF op...
Article
Full-text available
Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat and particle loads on the wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade (AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide parameter ran...
Article
In this paper, we present simulations of pedestal control by lithium granule injection (LGI) in NSTX. A model for small granule ablation has been implemented in the M3D-C1 code (Jardin et al 2012 Comput. Sci. Discovery 5 014002), allowing the simulation of realistic lithium granule injections. 2D and 3D simulations of Li injections in NSTX H-mode p...
Article
Full-text available
In this paper we present initial simulations of pedestal control by Lithium Granule Injection (LGI) in NSTX. A model for small granule ablation has been implemented in the M3D-C1 code [1], allowing the simulation of realistic Lithium granule injections. 2D simulations in NSTX L-mode and H-mode plasmas are done and the effect of granule size, inject...
Article
3D non-linear MHD simulations of a D 2 massive gas injection (MGI) triggered disruption in JET with the JOREK code provide results which are qualitatively consistent with experimental observations and shed light on the physics at play. In particular, it is observed that the gas destabilizes a large m/n = 2/1 tearing mode, with the island O-point co...
Article
A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the...
Poster
Full-text available
Modeling of ELM-pacing by lithium granule injection with M3D-C1
Conference Paper
Recently, the JET disruption mitigation system has been augmented with new disruption mitigation valve making the disruption mitigation system (DMS) of JET very close to the future ITER setup. Experiments have focussed on optimizing the operating parameters of the DMV in JET plasmas and studying the disruption asymmetries. It is found that each DMV...
Conference Paper
Full-text available
In this paper we present initial simulations of pedestal control by Lithium Granule Injection (LGI) in NSTX. A model for small granule ablation has been implemented in the M3D-C1 code [1], allowing the simulation of realistic Lithium granule injections. 2D simulations in NSTX L-mode and H-mode plasmas are done and the effect of granule size, inject...
Article
Edge Localized Modes(ELMs) rotating precursors were reported few milliseconds before an ELM crash in several tokamak experiments. Also, the reversal of the filaments rotation at the ELM crash is commonly observed. In this article, we present a mathematical model that reproduces the rotation of the ELM precursors as well as the reversal of the filam...
Article
Full-text available
Disruptions are a major operational concern for next generation tokamaks, including ITER. They may generate excessive heat loads on plasma facing components, large electromagnetic forces in the machine structures and several MA of multi-MeV runaway electrons. A more complete understanding of the runaway generation processes and methods to suppress...
Conference Paper
Runaway electrons have been created using injections of high-Z noble gases at JET. Their features are close to runaways created in the same way the carbon wall. Runaway beam suppression was achieved with massive gas injection only if fired before the beginning of the current quench. Injections of up to 4300 Pa.m3 on an already accelerated runaway b...
Article
Full-text available
JOREK 3D non-linear MHD simulations of a D 2 Massive Gas Injection (MGI) triggered disruption in JET are presented and compared in detail to experimental data. The MGI creates an overdensity that rapidly expands in the direction parallel to the magnetic field. It also causes the growth of magnetic islands ( m / n = 2 / 1 and 3/2 mainly) and seeds...
Article
The full dynamics of a multi-edge-localized-mode (ELM) cycle is modeled for the first time in realistic tokamak X-point geometry with the nonlinear reduced MHD code jorek. The diamagnetic rotation is found to be instrumental to stabilize the plasma after an ELM crash and to model the cyclic reconstruction and collapse of the plasma pressure profile...
Article
The dynamics of a multi-edge localized mode (ELM) cycle as well as the ELM mitigation by resonant magnetic perturbations (RMPs) are modeled in realistic tokamak X-point geometry with the non-linear reduced MHD code JOREK. The diamagnetic rotation is found to be a key parameter enabling us to reproduce the cyclical dynamics of the plasma relaxations...