Daniel Kennedy
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View article: Reducing turbulent transport in tokamaks by combining intrinsic rotation and the low momentum diffusivity regime
Reducing turbulent transport in tokamaks by combining intrinsic rotation and the low momentum diffusivity regime Open
Based on the analysis of a large number of high-fidelity nonlinear gyrokinetic simulations, we propose a novel strategy to improve confinement in spherical tokamak plasmas by combining up-down asymmetric flux surface shaping with the Low M…
Suppression of temperature-gradient-driven turbulence by sheared flows in fusion plasmas Open
Starting from the assumption that saturation of plasma turbulence driven by temperature-gradient instabilities in fusion plasmas is achieved by a local energy cascade between a long-wavelength outer scale, where energy is injected into the…
mHealth Incentivized Adherence Plus Patient Navigation (MIAPP): protocol for a pilot randomized controlled trial to improve linkage and retention on buprenorphine for hospitalized patients with methamphetamine use and opioid use disorder Open
Background Initiation of buprenorphine for treatment of opioid use disorder (OUD) in acute care settings improves access and outcomes, however patients who use methamphetamine are less likely to link to ongoing treatment. We describe the i…
A quasi-linear model of electromagnetic turbulent transport and its application to flux-driven transport predictions for STEP Open
A quasi-linear reduced transport model is developed from a database of high- $\beta$ electromagnetic nonlinear gyrokinetic simulations performed with spherical tokamak for energy production (STEP) relevant parameters. The quasi-linear mode…
The impact of E × B shear on microtearing based transport in spherical tokamaks Open
Electromagnetic microtearing modes (MTMs) have been observed in many different spherical tokamak (ST) regimes. Understanding how these and other electromagnetic modes nonlinearly saturate is likely critical in understanding the confinement…
View article: Land Processes Can Substantially Impact the Mean Climate State
Land Processes Can Substantially Impact the Mean Climate State Open
Terrestrial processes influence the atmosphere by controlling land‐to‐atmosphere fluxes of energy, water, and carbon. Prior research has demonstrated that parameter uncertainty drives uncertainty in land surface fluxes. However, the influe…
View article: Reducing turbulent transport in tokamaks by combining intrinsic rotation and the low momentum diffusivity regime
Reducing turbulent transport in tokamaks by combining intrinsic rotation and the low momentum diffusivity regime Open
Based on the analysis of a large number of high-fidelity nonlinear gyrokinetic simulations, we propose a novel strategy to improve confinement in spherical tokamak plasmas by combining up-down asymmetric flux surface shaping with the Low M…
$E\times B$ shear suppression of microtearing based transport in spherical tokamaks Open
Electromagnetic microtearing modes (MTMs) have been observed in many different spherical tokamak regimes. Understanding how these and other electromagnetic modes nonlinearly saturate is likely critical in understanding the confinement of a…
View article: Physics of the low momentum diffusivity regime in tokamaks and its experimental applicability
Physics of the low momentum diffusivity regime in tokamaks and its experimental applicability Open
Strong $E\times B$ plasma flow shear is beneficial for reducing turbulent transport. However, traditional methods of driving flow shear do not scale well to large devices such as future fusion power plants. In this paper, we use a large nu…
On the importance of parallel magnetic-field fluctuations for electromagnetic instabilities in STEP Open
This paper discusses the importance of parallel perturbations of the magnetic-field in gyrokinetic simulations of electromagnetic instabilities and turbulence at mid-radius in the burning plasma phase of the conceptual high- β , reactor-sc…
Suppression of temperature-gradient-driven turbulence by sheared flows in fusion plasmas Open
Starting from the assumption that saturation of plasma turbulence driven by temperature-gradient instabilities in fusion plasmas is achieved by a local energy cascade between a long-wavelength outer scale, where energy is injected into the…
A quasi-linear model of electromagnetic turbulent transport and its application to flux-driven transport predictions for STEP Open
A quasi-linear reduced transport model is developed from a database of high-$β$ electromagnetic nonlinear gyrokinetic simulations performed with Spherical Tokamak for Energy Production (STEP) relevant parameters. The quasi-linear model is …
On electromagnetic turbulence and transport in STEP Open
In this work, we present first-of-their-kind nonlinear local gyrokinetic (GK) simulations of electromagnetic turbulence at mid-radius in the burning plasma phase of the conceptual high- β , reactor-scale, tight-aspect-ratio tokamak Spheric…
View article: Gaussian process regression models for the properties of micro-tearing modes in spherical tokamaks
Gaussian process regression models for the properties of micro-tearing modes in spherical tokamaks Open
Spherical tokamaks have many desirable features that make them an attractive choice for a future fusion power plant. Power-plant viability is intrinsically related to plasma heat and particle confinement, and this is often determined by th…
View article: Electromagnetic gyrokinetic instabilities in STEP
Electromagnetic gyrokinetic instabilities in STEP Open
We present herein the results of a linear gyrokinetic analysis of electromagnetic microinstabilites in the conceptual high reactor-scale, tight-aspect-ratio tokamak Spherical Tokamak for Energy Production, https://step.ukaea.uk . We examin…
View article: Gaussian Process Regression models for the properties of micro-tearing modes in spherical tokamak
Gaussian Process Regression models for the properties of micro-tearing modes in spherical tokamak Open
Spherical tokamaks (STs) have many desirable features that make them an attractive choice for a future fusion power plant. Power plant viability is intrinsically related to plasma heat and particle confinement and this is often determined …
Gyrokinetic applications in electron–positron and non-neutral plasmas Open
In this paper, we summarize our recent work on gyrokinetic applications in electron–positron and non-neutral plasma. The electrostatic stability of electron–positron plasmas was investigated in dipole and slab geometries, with and without …
Nonlinear microtearing modes in MAST and their stochastic layer formation Open
First nonlinear gyrokinetic simulations of microtearing modes in the core of a MAST case are performed on two surfaces of the high-collisionality discharge used in Valovič et al (2011 Nucl. Fusion 51 073045) to obtain the favorable energy …
On electromagnetic turbulence and transport in STEP Open
In this work, we present first-of-their-kind nonlinear local gyrokinetic simulations of electromagnetic turbulence at mid-radius in the burning plasma phase of the conceptual high-$β$, reactor-scale, tight-aspect-ratio tokamak STEP (Spheri…
View article: Electromagnetic gyrokinetic instabilities in STEP
Electromagnetic gyrokinetic instabilities in STEP Open
We present herein the results of a linear gyrokinetic analysis of electromagnetic microinstabilites in the conceptual high-$β$, reactor-scale, tight-aspect-ratio tokamak STEP (Spherical Tokamak for Energy Production, https://step.ukaea.uk)…
Nonlinear microtearing modes in MAST and their stochastic layer formation Open
First nonlinear gyrokinetic simulations of microtearing modes in the core of a MAST case are performed on two surfaces of the high-collisionality discharge used in Valovič et al. Nucl. Fusion 51.7 (2011) to obtain the favorable energy conf…
Therapeutic Inertia in Prescribing Biologics for Patients with Moderate-to-Severe Asthma: Workshop Summary Open
Moderate-to-severe asthma represents about a quarter of the nearly 10% of Americans diagnosed with asthma. Many patients with moderate-to-severe asthma have uncontrolled symptoms that lead to exacerbations requiring oral corticosteroids. T…
Coulomb collisions in strongly anisotropic plasmas I. Cyclotron cooling in electron–ion plasmas Open
The behaviour of a collisional plasma that is optically thin to cyclotron radiation is considered, and the distribution functions accessible to it on the various time scales in the system are calculated. Particular attention is paid to the…
Coulomb collisions in strongly anisotropic plasmas II. Cyclotron cooling in laboratory pair plasmas Open
The behaviour of a strongly magnetised collisional electron–positron plasma that is optically thin to cyclotron radiation is considered, and the distribution functions accessible to it on the various timescales in the system are calculated…
View article: A new frontier in laboratory physics: magnetized electron–positron plasmas
A new frontier in laboratory physics: magnetized electron–positron plasmas Open
We describe here efforts to create and study magnetized electron–positron pair plasmas, the existence of which in astrophysical environments is well-established. Laboratory incarnations of such systems are becoming ever more possible due t…
The turbulent dynamics of Jupiter’s and Saturn’s weather layers: order out of chaos? Open
The weather layers of the gas giant planets, Jupiter and Saturn, comprise the shallow atmospheric layers that are influenced energetically by a combination of incoming solar radiation and localised latent heating of condensates, as well as…
Baroclinic and barotropic instabilities in planetary atmospheres: energetics, equilibration and adjustment Open
Baroclinic and barotropic instabilities are well known as the mechanisms responsible for the production of the dominant energy-containing eddies in the atmospheres of Earth and several other planets, as well as Earth's oceans. Here we cons…
Linear gyrokinetics of electron–positron plasmas in closed field-line systems Open
Linear gyrokinetic simulations of magnetically confined electron–positron plasmas are performed for the first time in the geometry and parameter regimes likely to be relevant for upcoming laboratory experiments. In such plasmas, the densit…
Baroclinic and barotropic instabilities in planetary atmospheres - energetics,equilibration and adjustment Open
Baroclinic and barotropic instabilities, are well known as the mechanisms responsible for the production of the dominant energy-containing eddies in the atmospheres of the Earth and several other planets, as well as the Earth's oceans. Her…