Impact of divertor closure on power exhaust in Negative Triangularity in TCV

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The ITER high-frequency (HF) magnetic diagnostic system has to provide essential measurements of MHD instabilities with vertical bar delta B-MEAS/B-POL vertical bar similar to 10(-4) (similar to 1 G) for frequencies up to 2 MHz to resolve toroidal mode numbers (n) in the range vertical bar n vertical bar = 10 to vertical bar n vertical bar = 50. A review of the measurement requirements for HF MHD instabilities in ITER was initiated during the TW4 work-program and led to significant interest for physics and

The main goal of this experiment is studying how blob propagation can be affected by an electrode grid in the case of an toroidal geometry with open field lines. Studies in this field are meant to better understand blob propagation in the SOLs of magnetic fusion devices and to develop more appropriate devices for controlling heat and particle fluxes. From the analysis of this specific experiment, we can conclude that blob trajectories seem to be influenced by voltage biasing on the electrode grid via the in

The impact of the bootstrap current (BC) has become an important issue in the modeling of quasi-symmetric stellarator devices. Magnetohydrodynamic equilibria have been calculated with self-consistent BC in the collisionless l/nu regime for characteristic quasi-symmetric configurations: a three-period quasi-axisymmetric and a four-period quasi-helically symmetric stellarator. The relationship between magnetic geometry and BC is shown along with its effect on the equilibrium when beta is increased. The releva

A pair of toroidally localized in-vessel antennas in Alcator C-Mod were used to excite and detect stable toroidal Alfven eigenmode (TAE) resonances in the frequency range of 400-500 kHz. By ramping the toroidal field, the plasma TAE frequency was swept through the constant antenna excitation frequency to find a resonance and the width of the resonance was measured to determine the effective damping rate of the mode. The toroidal field and density at the resonances were observed to scale as B-T proportional

A set of seven twin slit cameras, each containing two 20-element linear absolute extreme ultraviolet photodiode arrays, has been installed on the Tokamak a Configuration Variable. One array in each camera will operate as a bolometer and the second as a Lyman-alpha (L-alpha) emission monitor for estimating the recycled neutral flux. The camera configuration was optimized by simulations of tomographic reconstructions of the expected L-alpha emission. The diagnostic will provide spatial and temporal resolution

Electrostatic microinstabilities in ion internal barrier (ITB) and H-mode discharges of the ASDEX Upgrade tokamak [O. Gruber, R. Arslanbekov, C. Atanasiu , Nucl. Fusion 41, 1369 (2001)] have been investigated with a full radius gyrokinetic code. The code models linear stability and includes the effect of an equilibrium radial electric field and trapped electrons. In order to simulate plasmas in experimental conditions [k(perpendicular to)rho(L)similar toO(1)], the long wavelength approximation in the quasin

A view of recent experimental results and progress in the characterization of the statistical properties of edge turbulence in fusion plasmas is given. The study of the dynamical interplay between fluctuations in gradients, turbulent transport and radial electric fields has shown that these parameters are strongly coupled both in tokamak and stellarator plasmas. The size of turbulent events increases when the plasma deviates from the average density gradient. The radial velocity of fluctuations is of the or

Though helium plasmas are one option for the low activation phase of ITER, little effort has thus far been devoted to studying them in a large, diverted tokamak. A recent campaign on JET has therefore sought to address some of the important questions related to helium operation (He concentrations near 90%) in single null configuruations, particularly with regard to edge and divertor physics. This contribution compiles a selection of results from these experiments, in which, in each case, discharges have bee

A campaign of pure helium discharges in the JET tokamak equipped with the MarkIIGB divertor has been performed. This paper describes some of the experimental observations of divertor detachment obtained in L-mode density ramp He discharges and presents a selection of results from the application of B2.5-Eirene code modelling to a JET He plasma. Detachment is very different from that observed in equivalent D discharges. Particle fluxes remain attached up to higher densities and, with decreasing input power,

This paper shows the importance and feasibility of real-time tomography in fusion experiments for the example of soft X-ray (SXR) position measurements. The requirement of non-magnetic real-time diagnostics in low frequencies for ITER is discussed. This is illustrated by recent results of rapid tomographic inversion of SXR measurements on tokamak TCV. Comparison with the magnetic reconstruction data has not only shown the valuable resolution capabilities of both techniques, but also revealed a slight depend

Interaction of waves in the ion cyclotron range of frequencies (ICRF) with a plasma has a number of key properties that make them attractive beyond pure heating. First, the waves can interact resonantly with either the plasma ions or electrons. In the case of ion cyclotron damping, a small number of resonant ions are often accelerated to high energies. These ions, apart from heating the bulk plasma via Coulomb collisions, can increase fusion reactivity, affect plasma stability and drive current. They have a

The large physical size of the JET tokamak, its heating systems and diagnostics, and its capability to operate with full deuterium-tritium (D-T) plasmas, including high-power tritium neutral beam injection (NBI), give it unique possibilities in fast particle research in fusion plasmas. These have already been used to generate significant (2-3 MW level) power in fusion a-particles in the 1997 D-T campaign. Recent JET experiments have concentrated on two important scenarios of relevance to next-step tokamak d

Impact of divertor closure on power exhaust in Negative Triangularity in TCV

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Assessment of the ITER high-frequency magnetic diagnostic set

Experimental study of the effect of a biased electrode grid attached to a limiter on plasma blob propagation in a toroidal confinement device using an ultrafast camera

Bootstrap current and quasi-symmetry in reactor-size stellarators

Initial active MHD spectroscopy experiments exciting stable Alfven eigenmodes in Alcator C-Mod

AXUV bolometer and Lyman-alpha camera systems on the TCV tokamak

Simulations of global electrostatic microinstabilities in ASDEX Upgrade discharges

Statistical properties of turbulence: a new approach to characterize transport in fusion plasmas

Comparing scrape-off layer and divertor physics in JET pure He and D discharges

Divertor detachment during pure helium plasmas in JET

Present and perspective roles of soft X-ray tomography in tokamak plasma position measurements

Application of ICRF waves in tokamaks beyond heating

Overview of results and possibilities for fast particle research on JET