A5033321228- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Nuclear reactor physics and engineering
- Solar and Space Plasma Dynamics
- Plasma Diagnostics and Applications
- Nuclear Physics and Applications
- Nuclear Engineering Thermal-Hydraulics
- Nuclear Materials and Properties
- High-Energy Particle Collisions Research
- Vacuum and Plasma Arcs
- Atomic and Molecular Physics
- Particle Accelerators and Free-Electron Lasers
- Muon and positron interactions and applications
- Power System Optimization and Stability
- Meteorological Phenomena and Simulations
- Dust and Plasma Wave Phenomena
- Electrostatic Discharge in Electronics
- Blind Source Separation Techniques
- Target Tracking and Data Fusion in Sensor Networks
- Radiation Detection and Scintillator Technologies
- Tropical and Extratropical Cyclones Research
University of Lisbon
2009-2023
Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento
1999-2021
Instituto Superior Técnico
2002-2021
Instituto Politécnico de Lisboa
2021
Royal Military Academy
2020
University of California, San Diego
2019
General Atomics (United States)
2019
University of Wisconsin–Madison
2019
Princeton Plasma Physics Laboratory
2019
Princeton University
2019
In JET, both high density and low-q operation are limited by disruptions. The limit disruptions caused initially impurity radiation. This causes a contraction of the plasma temperature profile leads to an MHD unstable configuration. There is evidence magnetic island formation resulting in minor After several disruptions, major disruption with rapid energy quench occurs. event takes place two stages. first stage there loss from central region. second more drop very low temperature, apparently...
JET underwent a transformation from full carbon-dominated tokamak to fully metallic device with beryllium in the main chamber and tungsten divertor. This material combination is foreseen for activated phase of ITER. The ITER-Like Wall (ILW) experiment at shall demonstrate plasma compatibility walls reduction fuel retention. We report on set experiments (Ip = 2.0 MA, Bt 2.0–2.4 T, δ 0.2–0.4) different confinement conditions global gas balance analysis demonstrating strong long-term retention...
Operation and exploitation of present future Tokamak reactors require advanced scenario modeling in order to optimize engineering parameters the design phase as well physics performance during phase. The simulation scenarios involves simultaneous different regions reactor, characterized by symmetries, predict quantities such particle energy confinement, fusion yield, power deposited on wall, wall load from fast particles. JINTRAC is a system 25 interfaced Tokamak-physics codes for integrated...
High fusion power experiments using DT mixtures in ELM-free H mode and optimized shear regimes JET are reported. A of 16.1 MW has been produced an at 4.2 MA/3.6 T. The transient value the amplification factor was 0.95±0.17, consistent with high nDT(0)τEdiaTi(0) = 8.7 × 1020±20% m-3 s keV, maintained for about half energy confinement time until excessive edge pressure gradients resulted discharge termination by MHD instabilities. ratio DD to powers (from separate but otherwise similar...
The onset of a neoclassical tearing mode (NTM) depends on the existence large enough seed island. It is shown in Joint European Torus that NTMs can be readily destabilized by long-period sawteeth, such as obtained sawtooth stabilization from ion-cyclotron heating or current drive. This has important implications for burning plasma scenarios, alpha particles strongly stabilize sawteeth. also that, adding and drive just outside inversion radius, sawteeth are destabilized, resulting shorter...
The theory of non-linear tearing modes has been extended to include the effects rotation and interaction with a resistive wall. time dependent solution resulting equations shows spatial locking mode similar that observed in tokamak experiments. Time numerical calculations show model can explain qualitative way overall frequency evolution radial magnetic field behaviour on JET.
Persistent rapid up and down frequency chirping modes with a toroidal mode number of zero (n = 0) are observed in the JET tokamak when energetic ions, range several hundred keV, created by high field side ion cyclotron resonance heating. Fokker–Planck calculations demonstrate that heating method enables formation an energetically inverted distribution which supplies free energy for ions to excite related geodesic acoustic mode. The large shifts this attributed phase space structures whose...
In the course of Preliminary Tritium Experiment in JET, where combined deuterium and tritium neutral beam injection generated a DT fusion power 1.7 MW, ion cyclotron emission (ICE) was measured frequency range v ⩽ 180 MHz. The ICE spectra contain superthermal, narrow, equally spaced lines, which correspond to successive harmonics deuterons or alpha particles at outer midplane, close tile last closed flux surface major radius R approximately 4.0 m. Above about 100 MHz lines merge into...
Oscillating MHD modes in JET are often observed to slow down as they grow and generally stop rotating (lock) when the amplitude exceeds a critical value, then continue large amplitudes (r/Bθ ∼ 1%). The mode can early current rise or after perturbations, such pellet injection sawtooth collapse, maintain throughout remainder of discharge. Such quasistationary apparently have profound effects on plasma, including stopping central ion plasma rotation, reducing changing shape sawteeth, flattening...
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...
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....
Results from the first measurements of a core plasma poloidal rotation velocity (upsilontheta) across internal transport barriers (ITB) on JET are presented. The spatial and temporal evolution ITB can be followed along with upsilontheta radial profiles, providing very clear link between location steepest region ion temperature gradient localized spin-up upsilontheta. an order magnitude higher than neoclassical predictions for thermal particles in region, contrary to close agreement found...
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...
The stationary edge localized mode (ELM)-free 'Quiescent H-mode' (QH-mode) regime, obtained with counter neutral beam injection, is studied in ASDEX Upgrade and Joint European Torus. QH-mode plasmas have high pedestal core ion temperatures together good High-confinement (H-mode). ELMs are replaced by continuous MHD oscillations, the 'edge harmonic oscillation' (EHO) 'high frequency oscillation'. Stationarity of particle impurity densities linked to occurrence these modes. EHO location...
Impurity injection in the JET ELMy H-mode regime has produced high-confinement, quasi-steady-state plasmas with densities close to Greenwald density. However, at large Ar densities, a sudden loss of confinement is observed. A possible correlation between and observed MHD phenomena, both core edge plasma, was considered. The degradation coincided impurity profile peaking following disappearance sawtooth activity. In addition, density analysis confirmed that central modes prevented peaking....
Dedicated experiments to generate energetic D ions and fusion-born alpha particles were performed at the Joint European Torus (JET) with ITER-like wall (ILW). Using 3-ion radio frequency (RF) heating scenario, deuterium from neutral beam injection (NBI) accelerated in core of mixed plasmas higher energies ion cyclotron resonance (ICRF) waves, turn leading a core-localized source particles. The fast-ion distribution RF-accelerated D-NBI was controlled by varying ICRF NBI power ( 4–6 MW, 3–20...
During auxiliary heating experiments in JET, periodic bursts of MHD oscillations resembling 'fishbones' have been observed the signals several diagnostics. The repetition times 10–40 ms and oscillation frequencies ranging from 1 kHz to more than 20 kHz. While amplitude these increases at high poloidal toroidal beta, they are also plasmas with modest values beta. Moreover, occur discharges either neutral beam injection or ion cyclotron resonance heating, which is consistent idea that due an...
An overview is given of the experimental method, analysis technique and results for trace tritium experiments conducted on JET tokamak in 2003. Observations associated with events such as sawtooth collapses, neo-classical tearing modes edge localized are described. Tritium transport seen to approach levels plasma core at high density low q(95), barrier region internal (ITB) discharges. remains well above all other cases. The correlation measured diffusion coefficient convection velocity...
Observations of bulk plasma rotation in radio frequency (RF) heated JET discharges are reported. This study is concentrated on RF L-mode plasmas. In particular, the toroidal profiles plasmas by ion cyclotron resonance (ICRF) waves and lower hybrid (LH) have been analysed. It first time that with LH measured dedicated discharges. found outer region co-current direction irrespective heating scenario. An interesting feature profile appears to be hollow many at low current, but a current itself...
The effect of small deviations from a Maxwellian equilibrium on turbulent momentum transport in tokamak plasmas is considered. These non-Maxwellian features, arising diamagnetic effects, introduce strong dependence the radial flux co-current toroidal angular collisionality: As plasma goes nearly collisionless to weakly collisional, reverses direction radially inward outward. This indicates collisionality-dependent transition peaked hollow rotation profiles, consistent with experimental...
This paper summarizes the operational experience of ion cyclotron resonant frequency (ICRF) ITER-like antenna on JET aiming at substantially increasing power density in range requirements for ITER combined with load resiliency. An in-depth description its commissioning, aspects and achieved performances is presented.
In Hybrid plasma operation in JET with its ITER-like wall (JET-ILW) it is found that n>1 tearing activity can significantly enhance the rate of on-axis peaking tungsten impurities, which turn degrades discharge performance. Core n=1 instabilities be beneficial removing impurities from core (e.g. sawteeth or fishbones), but conversely also degrade confinement (particularly combination simultaneous n=3 activity). The nature MHD discharges, both previous Carbon and subsequent JET-ILW, surveyed...
Dedicated experiments were conducted in mixed H-D plasmas JET to demonstrate the efficiency of 3-ion ICRF scheme for plasma heating, relying on injected fast NBI ions as resonant ion species.Strong core localization RF power deposition close vicinity ion-ion hybrid layer was achieved, resulting an efficient generation energetic D ions, strong enhancement neutron rate and observation Alfvénic modes.A consistent physical picture that emerged from a range fast-ion measurements at JET, including...
A new deuterium-tritium experimental, DTE2, campaign has been conducted at the Joint European Torus (JET) between August 2021 and late December 2021. Motivated by significant enhancements in past decade JET, such as ITER-like wall enhanced auxiliary heating power, achieved a fusion energy world record performed broad range of fundamental experiments to inform ITER physics scenarios operations. New capabilities area product measurements nuclear diagnostics were available result long...