# Rogério JorgeInstituto Superior Técnico

Rogério Jorge

PhD

## About

34

Publications

1,457

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251

Citations

Introduction

Additional affiliations

March 2019 - May 2021

January 2015 - February 2019

January 2015 - February 2019

Education

September 2012 - October 2014

September 2010 - August 2013

## Publications

Publications (34)

The dynamics of electron-plasma waves is described at arbitrary collisionality by considering the full Coulomb collision operator. The description is based on a Hermite–Laguerre decomposition of the velocity dependence of the electron distribution function. The damping rate, frequency and eigenmode spectrum of electron-plasma waves are found as fun...

A numerically efficient framework that takes into account the effect of the Coulomb collision operator at arbitrary collisionalities is introduced. Such a model is based on the expansion of the distribution function on a Hermite-Laguerre polynomial basis to study the effects of collisions on magnetized plasma instabilities at arbitrary mean-free pa...

A full-F drift-kinetic model to describe the plasma dynamics in the scrape-off layer region of tokamak devices at arbitrary collisionality is derived. Our formulation is based on a gyroaveraged Lagrangian description of the charged particle motion, and the corresponding drift-kinetic Boltzmann equation that includes a full Coulomb collision operato...

The properties of plasma turbulence in a poloidally limited scrape-off layer (SOL) are addressed, with focus on ISTTOK, a large aspect ratio tokamak with a circular cross section. Theoretical investigations based on the drift-reduced Braginskii equations are carried out through linear calculations and non-linear simulations, in two- and three-dimen...

We perform a thorough study of greybody factors for minimally-coupled scalar fields propagating on the background of rotating black holes (BHs) in higher (odd) dimensions with all angular momenta set equal. For this special case, the solution enjoys an enhanced symmetry, which translates into the advantageous feature of being cohomogeneity-1, i.e.,...

A single-field-period quasi-isodynamic stellarator configuration is presented. This configuration, which resembles a twisted strip, is obtained by the method of direct construction, that is, it is found via an expansion in the distance from the magnetic axis. Its discovery, however, relied on an additional step involving numerical optimization, per...

The derivation and numerical implementation of a linearized version of the gyrokinetic (GK) Coulomb collision operator (Jorge et al. , J. Plasma Phys. , vol. 85, 2019, 905850604) and of the widely used linearized GK Sugama collision operator (Sugama et al. , Phys. Plasmas , vol. 16, 2009, 112503) is reported. An approach based on a Hermite–Laguerre...

The derivation and numerical implementation of a linearized version of the gyrokinetic (GK) Coulomb collision operator (Jorge R. et al., J. Plasma Phys. 85, 905850604 (2019)) and of the widely-used linearized GK Sugama collision operator (Sugama H. et al., Phys. Plasmas 16, 112503 (2009)) is reported. An approach based on a Hermite-Laguerre moment...

The stability of the ion-temperature gradient mode in quasisymmetric stellarators is assessed. This is performed using a set of analytical estimates together with linear gyrokinetic simulations. The peak growth rates, their corresponding real frequencies and wave-vectors are identified. A comparison is made between a first-order near-axis expansion...

Fluid models used to study the edge plasma region need to be benchmarked against similar conditions given that models can strongly differ in complexity and therefore the results they produce. Via this validation study undertaken through the framework of EUROfusion Enabling Research, four state-of-the art models - GBS, Hermes/BOUT++, HESEL and TOKAM...

The design of turbulence optimized stellarators has so far relied on three-dimensional equilibrium codes such as VMEC in order to find the minimum of a given objective function. In this work, we propose a complimentary approach based on the near-axis expansion to compute the geometry parameters of neoclassicaly optimized stellarators used in turbul...

A simplified analytical form of the on-axis magnetic well and Mercier's criterion for interchange instabilities for arbitrary three-dimensional magnetic field geometries is derived. For this purpose, a near-axis expansion based on a direct coordinate approach is used by expressing the toroidal magnetic flux in terms of powers of the radial distance...

A simplified analytical form of the on-axis magnetic well in Mercier's criterion for pressure-driven instabilities is derived for stellarators in both vacuum and MHD equilibrium. An analytical result allows for a better understanding and more efficient search of the parameter space for stellarator design. The derivation uses a direct coordinate app...

direct construction of analytical MHD equilibrium using an expansion in the powers of the distance to the magnetic axis is carried out. The approach developed here makes use of a set of orthogonal coordinates related to the geometry of the axis first derived by Mercier [1]. This reduces the MHD system of equations from a three-dimensional to a one-...

A four-dimensional plasma model able to describe the scrape-off layer region of tokamak devices at arbitrary collisionality is derived in the drift-reduced limit. The basis of the model is provided by a drift-kinetic equation that retains the full nonlinear Coulomb collision operator and describes arbitrarily far from equilibrium distribution funct...

We have recently demonstrated that by expanding in small distance from the magnetic axis compared with the major radius, stellarator shapes with low neoclassical transport can be generated efficiently. To extend the utility of this new design approach, here we evaluate measures of magnetohydrodynamic interchange stability within the same expansion....

The design of turbulence optimized stellarators has so far relied on three-dimensional equilibrium codes such as VMEC in order to find the minimum of a given objective function. In this work, we propose a complimentary approach based on the near-axis expansion to compute the geometry parameters of neoclassicaly optimized stellarators used in turbul...

We have recently demonstrated that by expanding in small distance from the magnetic axis compared to the major radius, stellarator shapes with low neoclassical transport can be generated efficiently. To extend the utility of this new design approach, here we evaluate measures of magnetohydrodynamic interchange stability within the same expansion. I...

A gyrokinetic model is presented that can properly describe large and small amplitude electromagnetic fluctuations occurring on scale lengths ranging from the electron Larmor radius to the equilibrium perpendicular pressure gradient scale length, and the arbitrarily large deviations from thermal equilibrium that are present in the plasma periphery...

Optimized stellarator configurations and their analytical properties are obtained using a near-axis expansion approach. Such configurations are associated with good confinement as the guiding center particle trajectories and neoclassical transport are isomorphic to those in a tokamak. This makes them appealing as fusion reactor candidates. Using a...

A direct construction of equilibrium magnetic fields with toroidal topology at arbitrary order in the distance from the magnetic axis is carried out, yielding an analytical framework able to explore the landscape of possible magnetic flux surfaces in the vicinity of the axis. This framework can provide meaningful analytical insight into the charact...

A gyrokinetic Coulomb collision operator is derived, which is particularly useful to describe the plasma dynamics at the periphery region of magnetic confinement fusion devices. The derived operator is able to describe collisions occurring in distribution functions arbitrarily far from equilibrium with variations on spatial scales at and below the...

A direct construction of equilibrium magnetic fields with toroidal topology at arbitrary order in the distance from the magnetic axis is carried out, yielding an analytical framework able to explore the landscape of possible magnetic flux surfaces in the vicinity of the axis. This framework can provide meaningful analytical insight on the character...

A gyrokinetic Coulomb collision operator is derived, which is particularly useful to describe the plasma dynamics at the periphery region of magnetic confinement fusion devices. The derived operator is able to describe collisions occurring in distribution functions arbitrarily far from equilibrium with variations on spatial scales at and below the...

A gyrokinetic model is presented that can properly describe strong flows, large and small amplitude electromagnetic fluctuations occurring on scale lengths ranging from the electron Larmor radius to the equilibrium perpendicular pressure gradient scale length, and large deviations from thermal equilibrium. The formulation of the gyrokinetic model i...

Ray propagation in weakly turbulent media is described by means of a quasilinear (QL) approach in which the dispersion relation and the ray equations are expanded up to, and including, second-order terms in the medium and ray fluctuations, leading to equations for the ensemble-averaged ray and its root-mean-square (rms) spreading. An important feat...

We present recent developments of GBS, a simulation code used to evolve plasma turbulence in the edge of fusion devices. GBS solves a set of 3D fluid equations, the Poisson and the Ampere equation, and a kinetic equation for the neutral atoms. Investigations carried out with GBS have significantly advanced our understanding of the plasma dynamics a...

We perform a thorough study of greybody factors for minimally-coupled scalar
fields propagating on the background of rotating black holes in higher (odd)
dimensions with all angular momenta set equal. For this special case, the
solution enjoys an enhanced symmetry, which translates into the advantageous
feature of being cohomogeneity-1, i.e., these...

Understanding Scrape-off Layer SOL (Scrape-off Layer) turbulence is crucial for the success of the entire fusion by magnetic confinement program. SOL dynam-ics determines the overall confinement and performance of future tokamaks (such as ITER), governs the heat load on the vessel wall, regulates the impurity dynamics, the plasma refueling and the...

We explore various aspects of supersymmetric black hole partition functions
in four-dimensional toroidally compactified heterotic string theory. These
functions suffer from divergences owing to the hyperbolic nature of the charge
lattice in this theory, which prevents them from having well-defined modular
transformation properties. In order to rect...