A5087720124- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Nuclear reactor physics and engineering
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- High-Energy Particle Collisions Research
- Solar and Space Plasma Dynamics
- Plasma Diagnostics and Applications
- Nuclear Engineering Thermal-Hydraulics
- Semiconductor Lasers and Optical Devices
- High-pressure geophysics and materials
- Earthquake Detection and Analysis
- Particle physics theoretical and experimental studies
- Brake Systems and Friction Analysis
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Fiber Optic Sensors
- Fluid Dynamics and Turbulent Flows
- Ion-surface interactions and analysis
- Laser-induced spectroscopy and plasma
- Spectroscopy and Laser Applications
- Nuclear Materials and Properties
- Cold Atom Physics and Bose-Einstein Condensates
- Radiation Therapy and Dosimetry
VTT Technical Research Centre of Finland
2019-2024
Tieto (Finland)
2022
Fusion (United States)
2020-2021
Fusion Academy
2020-2021
Tekes
2005-2016
Aalto University
2010-2012
Culham Centre for Fusion Energy
2010
Experiments were carried out in the JET tokamak to determine critical ion temperature inverse gradient length (R/LTi=R|nablaTi|/Ti) for onset of modes and stiffness Ti profiles with respect deviations from value. Threshold have been compared linear nonlinear predictions gyrokinetic code GS2. Plasmas higher values toroidal rotation show a significant increase R/LTi, which is found be mainly due decrease level. This finding has implications on extrapolation future machines present day results...
New transport experiments on JET indicate that ion stiffness mitigation in the core of a rotating plasma, as described by Mantica et al. [Phys. Rev. Lett. 102, 175002 (2009)] results from combined effect high rotational shear and low magnetic shear. The observations have important implications for understanding improved confinement advanced tokamak scenarios. Simulations using quasilinear fluid gyrofluid models show features mitigation, while nonlinear gyrokinetic simulations do not....
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....
The wall loads due to fusion alphas as well neutral beam injection- and ICRF-generated fast ions were simulated for ITER reference scenario-2 scenario-4 including the effects of ferritic inserts (FIs), test blanket modules (TBMs), 3D with two limiter structures. simulations carried out using Monte Carlo guiding-centre orbit-following code ASCOT. FIs found very effective in ameliorating detrimental toroidal ripple: ion are reduced practically their negligible axisymmetric level. thermonuclear...
JET’s frequency-modulated continuous wave (FMCW) reflectometers have been operating well with the current design since 2005, and density profiles automatically calculated intershot then. However, had long suffered from several shortcomings: poor agreement other diagnostics, sometimes inappropriately moving radially by centimeters, elevated levels of radial jitter, persistent wriggles (strong unphysical oscillations). In this research, techniques are applied to reflectometry data analysis,...
Dedicated experiments on TF ripple effects the performance of tokamak plasmas have been carried out at JET. The was found to a profound effect plasma rotation. central Mach number, M , defined as ratio rotation velocity and thermal velocity, drop function amplitude (δ) from an average value = 0.40–0.55 for operations standard JET δ 0.08% 0.25–0.40 0.5% 0.1–0.3 1%. should be considered when estimating in ITER. With co-current injection neutral beam (NBI), were rotate direction. However,...
Experiments at DIII-D investigated the effects of magnetic error fields similar to those expected from proposed ITER test blanket modules (TBMs) containing ferromagnetic material. Studied were on: plasma rotation and locking, confinement, L–H transition, H-mode pedestal, edge localized modes (ELMs) ELM suppression by resonant perturbations, energetic particle losses, more. The experiments used a purpose-built three-coil mock-up two magnetized TBMs in one equatorial port. largest effect was...
Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has applied separate the diffusive and convective terms. The magnitude of inward pinch depends strongly inverse density gradient length, with an experimental scaling for number being - Rv /χ ϕ = 1.2 R / L n + 1.4. There is no dependence collisionality, whereas seems depend weakly q -profile, decreasing increasing . Prandtl was not found either , collisionality or...
Abstract In the JET DTE2 campaign a new method was successfully tested to detect heating of bulk electrons by α-particles, using dynamic response electron temperature T e modulation ion cyclotron resonance (ICRH). A fundamental deuterium (D) ICRH scheme applied tritium-rich hybrid plasma with D-neutral beam injection (NBI). The i and accelerated deuterons leads modulated α -heating large delay respect other terms. significant phase ∼40° is measured between central , which can only be...
This study employs the established momentum transport analysis at ASDEX Upgrade [Zimmermann et al., Nucl. Fusion 63, 124003 (2023)] to investigate parametric variations of coefficients in core H-mode plasmas. These experimental results are compared a comprehensive database gyrokinetic calculations. Generally, good agreement between predicted and measured diffusive convective is found. The Prandtl numbers correlate most dominantly with magnetically trapped particle fraction. experimentally...
Perturbative experiments have been carried out in the Joint European Torus [Fusion Sci. Technol. 53(4) (2008)] order to identify diffusive and convective components of toroidal momentum transport. The torque source was modulated either by modulating tangential neutral beam power or antiphase normal beams produce a perturbation absence perturbation. resulting periodic rotation velocity modeled using time-dependent transport simulations extract empirical profiles diffusivity pinch. Details...
Detailed experimental studies of ion heat transport have been carried out in JET exploiting the upgrade active charge exchange spectroscopy and availability multi-frequency cyclotron resonance heating with 3He minority. The determination temperature gradient (ITG) threshold stiffness offers unique opportunities for validation well-established theory ITG driven modes. Ion is observed to decrease strongly presence toroidal rotation when magnetic shear sufficiently low. This effect dominant...
Fast beam-ion losses were studied in DIII-D the presence of a scaled mock-up two test blanket modules (TBM) for ITER. Heating protective tiles on front TBM surface was found when neutral beams injected and fields engaged. The fast-ion core confinement not significantly affected. Different orbit-following codes predict formation hot spot arising from beam ions deposited near edge plasma. are good agreement with each other total power at spot, predicting an increase decreasing separation...
Energy and pitch angle resolved measurements of highly energetic (megaelectronvolt (MeV) range) suprathermal ions ejected from the plasma through interaction with fishbone oscillations are presented. The obtained a 2D scintillator probe diagnostic installed on JET, which is designed to detect lost only above certain energy threshold ( E min,D ∼ 200 keV). In case reported here identified as fast protons had been accelerated high energies by ICRF minority heating. (∼0.5–4 MeV) approximately...
The effect of a neutral density background on the toroidal angular momentum and kinetic energy profiles has been investigated in JET. Under equivalent conditions but with increasing gas fuelling during flat top phase, it observed that both edge rotation temperature decrease. increase electron was not sufficient to compensate loss such confinement times are significantly reduced. localized mode behaviour is be affected by increased influx. A simple 1.5D fluid model used qualitative capture...
A broad survey of the experimental database neutral beam heated plasmas in JET tokamak has established theoretically expected ubiquity, rotating plasmas, a convective transport mechanism which its origin vertical particle drift resulting from Coriolis force. This inward convection, or pinch, leads to toroidal angular momentum and is characterized by pinch numbers RV /χ ϕ , rise near unity at r / ≈ 0.25 around 5 0.85. Linear gyrokinetic calculations number Prandtl χ i are good agreement with...
Abstract Strike-point sweeping, a technique often used to spread heat loads on divertor targets, was employed in JET experiments for the first time generate an edge-localized modulated particle source investigating plasma fuelling and transport edge region. This approach motivated by possibility of achieving higher modulation frequencies than those available from traditional gas puff at JET. Higher would enable collection more information electron density response source. Various sweeping...
A synthetic diagnostic model for the simulation of energy and pitch angle resolved measurements fast ion losses obtained by 2D scintillation-type detectors is presented subsequently tested on a JET discharge with fishbones (previously documented in Perez von Thun et al 2010 Nucl. Fusion 50 084009 ). The simulated distributions at detector are found to be excellent agreement measurements. simulations further suggest that nearly all take place early growth phase fishbone cycle, reach their...
Abstract A broad survey of the experimental database neutral beam heated baseline H-modes and hybrid scenarios in JET tokamak has established ubiquity non-diffusive momentum transport mechanisms rotating plasmas. As a result their presence, normalized angular frequency gradient R ∇ ω / is higher than expected from diffusion alone, by about unity core ( r ∼ 0.3), rising to near 5 close edge, where its contribution total comparable associated with diffusive flux. The magnitude parameter...
Abstract The impact of fishbone oscillations onto a confined fast-ion population is simulated for JET plasma and benchmarked against experiment quantitatively with the help neutron rate measurements. transient drops in volume integrated emission are found to be mainly caused by spatial redistribution (neutral beam injected) rather than loss. simulations yield quadratic dependence drop on amplitude. It that able correctly reproduce magnitude experimentally observed within factor 2....
The effects of toroidal field (TF) ripple on the edge pedestal characteristics were examined in TF scan experiments at plasma current I p 1.1 MA JET and JT-60U. amplitude δ R was defined as a value averaged over existing wells separatrix outer midplane. By installation ferritic inserts (FIs), reduced from 1% to 0.6% 3.2T (0.5% 2.2 T) In JET, varied 0.08% by feeding different currents odd even set coils out 32 coils. pressure ped similar for cases before after FIs Similarly, no clear...
New experiments in the low-torque ITER Q = 10 scenario on DIII-D demonstrate that n 1 magnetic fields from a single row of ex-vessel control coils enable operation at performance metrics presence applied non-axisymmetric test blanket module (TBM) mock-up coil. With compensation, below ITER-equivalent injected torque is successful three times equivalent toroidal field ripple for pair TBMs one equatorial port, whereas uncompensated TBM leads to rotation collapse, loss H-mode and plasma current...
Abstract A dimensionless parameter dependence study of intrinsic torque has been performed on a database H- and I-mode plasmas from the Alcator C-Mod tokamak. The was determined by comparing angular momentum density profiles just before after L–H L–I transitions. found to scale as <?CDATA ${\beta }_{N}^{ 1.5}\enspace {\rho }_{{\ast}}^{-1.0}\enspace {\nu }_{{\ast}}^{0.1}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msubsup> <mml:mrow>...
Abstract Advanced momentum transport analysis is used to study matched hydrogen (H) and deuterium (D) plasmas in the core of ASDEX Upgrade. The aim validate gyrokinetic theory assess a possible isotope dependence. methodology extracts diffusion, convection, intrinsic torque as function time from experiments employing neutral beam injection (NBI) modulation. H D plasma scenarios with comparable ion heat fluxes, NBI torque, electron densities, several dimensionless parameters were designed...
Understanding the physics of internal transport barriers (ITBs) is a crucial issue in developing ITER relevant advanced tokamak scenarios. To gain new information on ITBs, RF power modulation experiments, mainly devoted to study electron heat through have been performed JET tokamak. The main results reported [1]. present paper describes detail data analysis and numerical modelling work carried out for interpretation experiments. ITBs located negative shear region behave as localized...