Identity, Belonging and Political Activism in The Sri Lankan Communities in Germany

This research examines the dynamic relationship of Sinhalese and Tamils living in Germany in regards to their home and host country, and seeks to better understand the complexities of their political involvement. The research is based on qualitative research methodologies. The author conducted 30 interviews in Berlin during the period 2006–2008 to inform this research. The research not only provides an overview of the historical contexts of Sri Lanka and Germany, it also links these histories with the processes of outmigration from Sri Lanka and in-migration to Germany. It then continues to analyse the construction of belonging in the context of the Sri Lankan diaspora communities in Berlin. The research examines how far concepts of home, citizenship, nationalism and identity construction shape the sense of belonging of first and second generation Sinhalese and Tamils in Berlin. Finally, it analyses the ways the members of the Sri Lankan diaspora communities engage in economic, political, social, cultural and virtual activities in the home and host country, and how far these activities shape belonging and are politically motivated. The research also considers and studies the gendered nature of belonging and transnational political practices. The research uniquely combines the study of the Tamil diaspora with the study of the Sinhalese diaspora in Berlin. It allows new insights into the complex and multiple constructions of belonging and identity and into the interplay of gender, ethnicity and generations, and it highlights the importance of political activism in the conceptualization of belonging

Structure of Plasma Heating in Gyrokinetic Alfvénic Turbulence

We analyze plasma heating in weakly collisional kinetic Alfv\'en wave (KAW) turbulence using high resolution gyrokinetic simulations spanning the range of scales between the ion and the electron gyroradii. Real space structures that have a higher than average heating rate are shown not to be confined to current sheets. This novel result is at odds with previous studies, which use the electromagnetic work in the local electron fluid frame, i.e. $\mathbf{J} \!\cdot\! (\mathbf{E} + \mathbf{v}_e\times\mathbf{B})$, as a proxy for turbulent dissipation to argue that heating follows the intermittent spatial structure of the electric current. Furthermore, we show that electrons are dominated by parallel heating while the ions prefer the perpendicular heating route. We comment on the implications of the results presented here.Comment: 5 pages, 3 figure

Gyrokinetic GENE simulations of DIII-D near-edge L-mode plasmas

We present gyrokinetic simulations with the GENE code addressing the near-edge region of an L-mode plasma in the DIII-D tokamak. At radial position $\rho=0.80$, simulations with the ion temperature gradient increased by $40\%$ above the nominal value give electron and ion heat fluxes that are in simultaneous agreement with the experiment. This gradient increase is consistent with the combined statistical and systematic uncertainty $\sigma$ of the Charge Exchange Recombination Spectroscopy (CER) measurements at the $1.6 \sigma$ level. Multi-scale simulations are carried out with realistic mass ratio and geometry for the first time in the near-edge. These multi-scale simulations suggest that the highly unstable ion temperature gradient (ITG) modes of the flux-matched ion-scale simulations suppress electron-scale transport, such that ion-scale simulations are sufficient at this location. At radial position $\rho=0.90$, nonlinear simulations show a hybrid state of ITG and trapped electron modes~(TEMs), which was not expected from linear simulations. The nonlinear simulations reproduce the total experimental heat flux with the inclusion of $\mathbf{E} \times \mathbf{B}$ shear effects and an increase in the electron temperature gradient by $\sim 23\%$. This gradient increase is compatible with the combined statistical and systematic uncertainty of the Thomson scattering data at the $1.3 \sigma$ level. These results are consistent with previous findings that gyrokinetic simulations are able to reproduce the experimental heat fluxes by varying input parameters close to their experimental uncertainties, pushing the validation frontier closer to the edge region.Comment: 14 pages, 17 figures, published in Physics of Plasma

Electromagnetic stabilization of tokamak microturbulence in a high-β\beta regime

The impact of electromagnetic stabilization and flow shear stabilization on ITG turbulence is investigated. Analysis of a low-$\beta$ JET L-mode discharge illustrates the relation between ITG stabilization, and proximity to the electromagnetic instability threshold. This threshold is reduced by suprathermal pressure gradients, highlighting the effectiveness of fast ions in ITG stabilization. Extensive linear and nonlinear gyrokinetic simulations are then carried out for the high-$\beta$ JET hybrid discharge 75225, at two separate locations at inner and outer radii. It is found that at the inner radius, nonlinear electromagnetic stabilization is dominant, and is critical for achieving simulated heat fluxes in agreement with the experiment. The enhancement of this effect by suprathermal pressure also remains significant. It is also found that flow shear stabilization is not effective at the inner radii. However, at outer radii the situation is reversed. Electromagnetic stabilization is negligible while the flow shear stabilization is significant. These results constitute the high-$\beta$ generalization of comparable observations found at low-$\beta$ at JET. This is encouraging for the extrapolation of electromagnetic ITG stabilization to future devices. An estimation of the impact of this effect on the ITER hybrid scenario leads to a 20% fusion power improvement.Comment: 10 pages, 13 figures. Paper coupled to invited talk at the 41st EPS conference, Berlin, 201

Electromagnetic stabilization of tokamak microturbulence in a high- β regime

The impact of electromagnetic stabilization and flow shear stabilization on ITG turbulence is investigated. Analysis of a low- β JET L-mode discharge illustrates the relation between ITG stabilization and proximity to the electromagnetic instability threshold. This threshold is reduced by suprathermal pressure gradients, highlighting the effectiveness of fast ions in ITG stabilization. Extensive linear and nonlinear gyrokinetic simulations are then carried out for the high- β JET hybrid discharge 75225, at two separate locations at inner and outer radii. It is found that at the inner radius, nonlinear electromagnetic stabilization is dominant and is critical for achieving simulated heat fluxes in agreement with the experiment. The enhancement of this effect by suprathermal pressure also remains significant. It is also found that flow shear stabilization is not effective at the inner radii. However, at outer radii the situation is reversed. Electromagnetic stabilization is negligible while the flow shear stabilization is significant. These results constitute the high- β generalization of comparable observations found at low- β at JET. This is encouraging for the extrapolation of electromagnetic ITG stabilization to future devices. An estimation of the impact of this effect on the ITER hybrid scenario leads to a 20% fusion power improvement.</p