Analysis of Alfven eigenmode destabilization by energetic particles in Large Helical Device using a Landau-closure model

Energetic particle populations in nuclear fusion experiments can destabilize the Alfven Eigenmodes through inverse Landau damping and couplings with gap modes in the shear Alfven continua. We use the reduced MHD equations to describe the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system, coupled with equations of density and parallel velocity moments for the energetic particles. We add the Landau damping and resonant destabilization effects using a closure relation. We apply the model to study the Alfven mode stability in the inward-shifted configurations of the Large Helical Device (LHD), performing a parametric analysis of the energetic particle beta(beta(f)) in a range of realistic values, the ratios of the energetic particle thermal/Alfven velocities (V-th/V-A0), the magnetic Lundquist numbers (S) and the toroidal modes (n). The n = 1 and n = 2 TAEs are destabilized, although the n = 3 and n = 4 TAEs are weakly perturbed. The most unstable configurations are associated with the density gradients of energetic particles in the plasma core: the TAEs are destabilized, even for small energetic particle populations, if their thermal velocity is lower than 0.4 times the Alfven velocity. The frequency range of MHD bursts measured in the LHD are 50-70 kHz for the n = 1 and 60-80 kHz for the n = 2 TAE, which is consistent with the model predictions.This material is based on work supported both by the U.S. Department of Energy and the Office of Science, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. The research was sponsored in part by the Ministerio de Economia y Competitividad of Spain under project no. ENE2015-68265-P. We also want to acknowledge the LHD group at NIFS for providing us with the VMEC equilibria, and useful interactions with Y. Todo and M. Osakabe

Relation of plasma flow structures to passive particle tracer orbits

The properties of plasma flow topological structures are compared with those of passive tracer particles within a framework of the continuous random walk (CTRW) approach. Vortices may cause some of the trapping of particles, while large scale flows may carry them from vortex to vortex. The results indicate that most of the trappings that are completed during the calculation correspond to tracers trapped on broken filaments, including possible multiple trappings. The probability distribution function of the trapping times is then a function of the filament length, and has a lognormal character, like the distribution of filament lengths

Analysis of Alfven eigenmode destabilization in ITER using a Landau closure model

Alfvén eigenmodes (AE) can be destabilized during ITER discharges driven by neutral beam injection (NBI) energetic particles (EP) and alpha particles. The aim of the present study is to analyze the AE stability of different ITER operation scenarios considering multiple energetic particle species. We use the reduced magneto-hydrodynamic (MHD) equations to describe the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system, coupled with equations of density and parallel velocity moments for the EP species including the effect of the acoustic modes. The AEs driven by the NBI EP and alpha particles are stable in the configurations analyzed, only MHD-like modes with large toroidal couplings are unstable, although both can be destabilized if the EP increases above a threshold. The threshold is two times the model value for the NBI EP and alpha particles in the reverse shear (RS) case, leading to the destabilization of Beta induced AE (BAE) near the magnetic axis with a frequency of kHz and toroidal or elliptical AE (TAE/EAE) in the RS region with a frequency of kHz, respectively. On the other hand, the hybrid and steady state configurations show a threshold 3 times larger with respect to the model for the alpha particle and 40 times for the NBI EP, also destabilizing BAE and TAE between the inner and middle plasma region. In addition, a extended analysis of the RS scenario where the of both alpha particles and NBI EP are above the AE threshold, multiple EP damping effects are also identified as well as optimization trends regarding the resonance properties of the alpha particle and NBI EP with the bulk plasma.This material based on work is partially supported both by the U.S. Department of Energy, Office of Science, under Contract DE-AC05-00OR22725 with UT-Battelle, LLC and U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award No. DE-FC02-04ER54698. DIII-D data shown in this paper can be obtained in digital format by following the links at https://fusion.gat.com/global/D3D_DMP. This research was sponsored in part by the Ministerio of Economia y Competitividad of Spain under project no. ENE2015-68265-P. The authors would like to thanks Y. Todo for fruitful discussions

Modelling Weirs in Two-Dimensional Shallow Water Models

Datos experimentais dispoñibles en: http://doi.org/10.5281/zenodo.5062775[Abstract] 2D models based on the shallow water equations are widely used in river hydraulics. However, these models can present deficiencies in those cases in which their intrinsic hypotheses are not fulfilled. One of these cases is in the presence of weirs. In this work we present an experimental dataset including 194 experiments in nine different weirs. The experimental data are compared to the numerical results obtained with a 2D shallow water model in order to quantify the discrepancies that exist due to the non-fulfillment of the hydrostatic pressure hypotheses. The experimental dataset presented can be used for the validation of other modelling approaches.This study received financial support from the Spanish Ministry of Science, Innovation and Universities (Ministerio de Ciencia Innovacion y Universidades) within the project “VAMONOS: Development of non-hydrostatic models forenvironmental hydraulics. Two-dimensional flow in rivers” (reference CTM2017-85171-C2-2-R).http://doi.org/10.5281/zenodo.506277

Joint assimilation of satellite soil moisture and streamflow data for the hydrological application of a two-dimensional shallow water model

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract:] Data assimilation (DA) in physically-based hydrodynamic models is conditioned by the difference in temporal and spatial scales of the observed data and the resolution of the model itself. In order to use remote sensing data in small-scale hydrodynamic modelling, it is necessary to explore innovative DA methods that can lead to a more plausible representation of the spatial variability of the parameters and processes involved. In the present study, satellite-derived soil moisture and in situ-observed streamflow data were jointly assimilated into a high-resolution hydrological-hydrodynamic model based on the Iber software, using the Tempered Particle Filter (TPF) for the dual estimation of model state variables and parameters. Twelve storm events occurring in a 199 km2 catchment located in NW Spain were used for testing the proposed approach. A 3-step procedure was followed: (1) sensitivity analysis of the model parameters; (2) joint assimilation of soil moisture and discharge data to estimate correlations between observations and model parameters; (3) joint assimilation of soil moisture and discharge data using an initial set of particles and parameter standard deviations derived from prior information. The numerical model correctly reproduces the observed data, with an average Nash-Sutcliffe efficiency (NSE) value of 0.74 over the 12 events when the prior information is used. The approach described is shown to be most efficient with storm events that produce isolated peak discharges.The authors acknowledge the support of Augas de Galicia and the Galicia Meteorological Agency (Metogalicia). Gonzalo García-Alén acknowledge the support of the INDITEX-UDC 2021 and 2022 Predoctoral Grants. The research reported herein was funded by the Luxembourg National Research Fund through the CASCADE (grant no. C17/SR/11682050) Project. Funding for open access charge: Universidade da Coruña/CISUG.National Research Fund of Luxembourg; C17/SR/1168205

Topological structures of the resistive pressure gradient turbulence with averaged poloidal flow

When a significant averaged poloidal flow is generated by the resistive pressure-gradient-driven turbulence the topological properties of the flow structures can change in some radial regions where the shear flow is large. We have applied the topological analysis approach that we have developed (2013 J. Phys. A: Math. Theor. 46 375501) to this situation and found that in addition to the filamentary vortex structures there are deformed toroidal structures that seem to act as transport barriers. Analysis of all these structures is presented here.This research was sponsored by DGICYT (Dirección General de Investigación Científica y Técnica) of Spain under Project No. ENE2012-38620-C02-02. One of us (B.A.C) also gratefully acknowledges the support from a 'Cátedra de Excelencia' from Universidad Carlos III and Banco de Santander

Topological characterization of flow structures in resistive pressure-gradient-driven turbulence

9 pages, 13 figures.-- PACS nrs.: 52.35.Ra, 52.65.Kj, 47.27.−i.-- ArXiv pre-print available at: http://arxiv.org/abs/0811.3548Visualization of turbulent flows is a powerful tool to help understand the turbulence dynamics and induced transport. However, it does not provide a quantitative description of the observed structures. In this paper, an approach to characterize quantitatively the topology of the flows is given. The technique, which can be applied to any type of turbulence dynamics, is illustrated through the example of resistive ballooning instabilities.One of us (B.A.C.) is grateful to the Asociación EURATOM-CIEMAT for providing travel expenses. Part of this work is supported by the DGI (Dirección General de Investigación) of Spain under Project No. ENE2006-15244-C03-01 and by Grant No. CM-UC3M (Comunidad de Madrid—Universidad Carlos III) Project No. CCG07-UC3M/ESP-3407.Publicad

Three-dimensional linear peeling-ballooning theory in magnetic fusion devices

Ideal magnetohydrodynamics theory is extended to fully 3D magnetic configurations to investigate the linear stability of intermediate to high n peeling-ballooning modes, with n the toroidal mode number. These are thought to be important for the behavior of edge localized modes and for the limit of the size of the pedestal that governs the high confinement H-mode. The end point of the derivation is a set of coupled second order ordinary differential equations with appropriate boundary conditions that minimize the perturbed energy and that can be solved to find the growth rate of the perturbations. This theory allows of the evaluation of 3D effects on edge plasma stability in tokamaks such as those associated with the toroidal ripple due to the finite number of toroidal field coils, the application of external 3D fields for elm control, local modification of the magnetic field in the vicinity of ferromagnetic components such as the test blanket modules in ITER, etc.This research was sponsored in part by DGICYT (Dirección General de Investigaciones Científicas y Tecnológicas) of Spain under Project No. ENE2012-38620-C02-02 and also in part by Comunidad de Madrid Project No. S2009/ENE-1679.Publicad

Topological characterization of the transition from laminar regime to fully developed turbulence in the resistive pressure-gradient-driven turbulence model

11 pages, 20 figures.-- PACS nrs.: 52.35.Ra, 52.65.Kj, 47.27.−i.For the resistive pressure-gradient-driven turbulence model, the transition from laminar regime to fully developed turbulence is not simple and goes through several phases. For low values of the plasma parameter β, a single quasicoherent structure forms. As β increases, several of these structures may emerge and in turn take the dominant role. Finally, at high β, fully developed turbulence with a broad spectrum is established. A suitable characterization of this transition can be given in terms of topological properties of the flow. Here, we analyze these properties that provide an understanding of the turbulence-induced transport and give a measure of the breaking of the homogeneity of the turbulence. To this end, an approach is developed that allows discriminating between topological properties of plasma turbulence flows that are relevant to the transport dynamics and the ones that are not. This is done using computational homology tools and leads to a faster convergence of numerical results for a fixed level of resolution than previously presented in Phys. Rev. E 78, 066402 (2008).Part of this research was sponsored by the Dirección General de Investigación of Spain under Project No. ENE2006-15244-C03-01. One of us (BAC) is grateful for the "Cátedra de Excelencia" from Universidad Carlos III and Banco Santander. The authors thankfully acknowledge the computer resources, technical expertise and assistance provided by the Barcelona Supercomputing Center—Centro Nacional de Supercomputación (http:// www.bsc.es).Publicad