M. Lennholm
A5039266439- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Nuclear reactor physics and engineering
- Plasma Diagnostics and Applications
- Gyrotron and Vacuum Electronics Research
- Nuclear Physics and Applications
- High-Energy Particle Collisions Research
- Solar and Space Plasma Dynamics
- Particle physics theoretical and experimental studies
- Electrostatic Discharge in Electronics
- Particle Accelerators and Free-Electron Lasers
- Power Line Inspection Robots
- Dust and Plasma Wave Phenomena
- Advanced MRI Techniques and Applications
- Nuclear Engineering Thermal-Hydraulics
- Aerospace Engineering and Control Systems
- Real-time simulation and control systems
- IoT-based Smart Home Systems
- Power System Optimization and Stability
- Fire effects on ecosystems
- Electromagnetic Launch and Propulsion Technology
Culham Science Centre
2015-2024
European Commission
2012-2024
Culham Centre for Fusion Energy
2011-2024
United Kingdom Atomic Energy Authority
2021-2024
CEA Cadarache
2000-2023
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2000-2023
Université Libre de Bruxelles
2018
Aalto University
2013
National Agency for New Technologies, Energy and Sustainable Economic Development
2013
Karlsruhe Institute of Technology
2011
Abstract The JET hybrid scenario has been developed from low plasma current carbon wall discharges to the record-breaking Deuterium-Tritium plasmas obtained in 2021 with ITER-like Be/W wall. development started pure Deuterium refinement of current, and toroidal magnetic field choices succeeded solving heat load challenges arising 37 MW injected power ITER like environment, keeping radiation edge core controlled, avoiding MHD instabilities reaching high neutron rates. have re-run Tritium...
Abstract Ion cyclotron resonance frequency (ICRF) heating has been an essential component in the development of high power H-mode scenarios Jet European Torus ITER-like wall (JET-ILW). The ICRF performance was improved by enhancing antenna-plasma coupling with dedicated main chamber gas injection, including preliminary minimization RF-induced plasma-wall interactions, while RF where optimized for core impurity screening terms ion position and minority hydrogen concentration. impact on...
The JET exploitation plan foresees D–T operations in 2020 (DTE2). With respect to the first campaign 1997 (DTE1), when was equipped with a carbon wall, experiments will be conducted presence of beryllium–tungsten ITER-like wall and benefit from an extended improved set diagnostics higher additional heating power (32 MW neutral beam injection + 8 ion cyclotron resonance heating). There are several challenges presented by new wall: general deterioration pedestal confinement; risk heavy...
This paper summarizes the physical principles behind novel three-ion scenarios using radio frequency waves in ion cyclotron range of frequencies (ICRF). We discuss how to transform mode conversion electron heating into a new flexible ICRF technique for and fast-ion generation multi-ion species plasmas. The theoretical section provides practical recipes selecting plasma composition realize scenarios, including two equivalent possibilities choice resonant absorbers that have been identified....
Abstract The work describes the pedestal structure, transport and stability in an effective mass ( A eff ) scan from pure deuterium to tritium plasmas using a type I ELMy H-mode dataset which key parameters that affect behaviour (normalized pressure, ratio of separatrix density density, ion Larmor radius, collisionality rotation) are kept as constant possible. Experimental results show significant increase at top with increasing , modest reduction temperature pressure. variations heights...
Abstract As part the DTE2 campaign in JET tokamak, we conducted a parameter scan T and D-T complementing existing pulses H D. For different main ion masses, type-I ELMy H-modes at fixed plasma current magnetic field can have pedestal pressure varying by factor of 4 total changing from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>β</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">N</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo>...
Abstract In magnetic fusion devices, error field (EF) sources, spurious perturbations, need to be identified and corrected for safe stable (disruption-free) tokamak operation. Within Work Package Tokamak Exploitation RT04, a series of studies have been carried out test the portability novel non-disruptive method, designed tested in DIII-D (Paz-Soldan et al 2022 Nucl. Fusion 62 126007), perform an assessment model-based EF control strategies towards their applicability ITER. this paper,...
Success of the UK’s Spherical Tokamak for Energy Production (STEP) programme requires a robust plasma control system. This system has to guide from initiation burning phase, maintain it there, produce desired fusion power duration and then terminate safely. be done in challenging environment with limited sensors without overloading plasma-facing components. The parameters operational regime STEP prototype will very different tokamaks, which are presently operation. During burn,...
An experiment at the Joint European Torus (JET) has demonstrated clear self-heating of a deuterium-tritium plasma by alpha particles produced in fusion reactions. The heating was identified scanning and neutral beam mixtures together from pure deuterium to nearly tritium 10.5 MW hot ion H mode. At an optimum mixture $(60\ifmmode\pm\else\textpm\fi{}20)%\mathrm{T}$, gain ( ${\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}P}_{\mathrm{fusion}}/{P}_{\mathrm{absorbed}}$) 0.65 showed clearly as...
Burning plasmas with 500 MW of fusion power on ITER will rely partially detached divertor operation to keep target heat loads at manageable levels. Such regimes be maintained by a real-time control system using the seeding radiative impurities like nitrogen (N), neon or argon as actuator and one more diagnostic signals sensors. Recently, detachment has been successfully achieved in Type I ELMy H-mode JET-ITER-like wall discharges saturation current (Isat) measurements from Langmuir probes...
Abstract We present an overview of results from a series L–H transition experiments undertaken at JET since the installation ITER-like-wall (JET-ILW), with beryllium wall tiles and tungsten divertor. Tritium, helium deuterium plasmas have been investigated. Initial in tritium show ohmic transitions low density power threshold for ( P LH ) is lower than ones densities, while we still lack contrasted data to provide scaling high densities. In there notable shift which minimum <?CDATA...
Abstract A toroidal Alfvén eigenmode (TAE) has been observed to be driven by alpha particles in a JET deuterium-tritium internal transport barrier plasma. The observation occurred 50 ms after the removal of neutral beam heating (NBI). mode is on magnetics, soft-xray, interferometry and reflectometry measurements. We present detailed stability calculations using similar tool set validated during deuterium only discharges. These strongly support conclusion that TAE, this was destabilized...
The fusion-born alpha particle heating in magnetically confined fusion machines is a high priority subject for studies. self-heating of thermonuclear plasma by particles was observed recent deuterium-tritium (D-T) experiments on the joint European torus. This observation possible conducting so-called "afterglow" where transient yield achieved with neutral beam injection as only external source, and then termination at peak performance. allowed first direct evidence electron plasmas alphas to...
Abstract The recent deuterium–tritium campaign in JET-ILW (DTE2) has provided a unique opportunity to study the isotope dependence of L-H power threshold an ITER-like wall environment (Be and W divertor). Here we present results from dedicated transition experiments at JET-ILW, documenting tritium plasmas, comparing them with matching deuterium hydrogen datasets. From earlier it is known that as plasma isotopic composition changes deuterium, through varying deuterium/hydrogen concentrations,...
Abstract The reference ion cyclotron resonance frequency (ICRF) heating schemes for ITER deuterium–tritium (D-T) plasmas at the full magnetic field of 5.3 T are second harmonic and 3 He minority heating. wave-particle location these coincide central a wave 53 MHz T. Experiments have been carried out in major D-T campaign (DTE2) JET, its prior D campaigns, to integrate ICRF scenarios JET high-performance compare their performance with commonly used hydrogen (H) In 50:50 D:T plasmas, up 35% 5%...
Abstract The dimensionless isotope mass scaling experiment between pure Deuterium and Tritium plasmas with matched <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mi>ρ</mml:mi> <mml:mo>∗</mml:mo> </mml:msup> </mml:math> , <mml:mi>ν</mml:mi> β n q <mml:msub> <mml:mi>T</mml:mi> <mml:mi>e</mml:mi> </mml:msub> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mi>i</mml:mi> has been achieved in JET L-mode dominant electron heating (NBI+ohmic) conditions....
Abstract Building on prior analysis of ASDEX Upgrade (AUG) experiments (Henderson et al 2023 Nucl. Fusion 63 086024), this study compares simple analytical formula predictions for divertor detachment onset and reattachment timescales in JET experiments. Detachment primarily scales with neutral pressure, impurity concentration, power directed to the targets, machine size, integral perpendicular decay length. experiments, focusing seeding mixtures Ne Ar, align predictions. Radiation...
Abstract The fusion reaction between deuterium and tritium, D ( T,n ) 4 He is the main source of energy in future thermonuclear reactors. Alpha-particles -ions) born with an average 3.5 MeV transferring to thermal plasma during their slowing down, should provide self-sustained D–T burn. adequate confinement α -particles essential efficient heating bulk steady burning a reactor plasma. That why fusion-born -particle studies have been priority task second experiments (DTE2) on Joint European...
Abstract JET returned to deuterium-tritium operations in 2023 (DTE3 campaign), approximately two years after DTE2. DTE3 was designed as an extension of JET's 2022-2023 deuterium campaigns, which focused on developing scenarios for ITER and DEMO, integrating in-depth physics understanding control schemes. These were evaluated with mixed D-T fuel, using the only remaining tritium-capable tokamak until its closure 2023. A core-edge-SOL integrated H-mode scenario developed tested D-T, showing...
In order to simultaneously control the current and pressure profiles in high performance tokamak plasmas with internal transport barriers (ITB), a multi-variable model-based technique has been proposed. New algorithms using truncated singular value decomposition (TSVD) of linearized model operator retaining distributed nature system have implemented JET system. Their simplest versions applied density profile reversed shear three heating drive actuators (neutral beam injection, ion cyclotron...
This paper describes a new technique which has been implemented on the JET tokamak to investigate integrated real-time control of several plasma profiles simultaneously (such as current, temperature and pressure) reports results first experimental tests. The are handled through their projection suitable basis functions according Galerkin scheme. Their response three actuators (heating current drive powers injected in plasma) is linearized an experimentally deduced multi-input multi-output...