Hartmut Zohm

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First experiments with nonaxisymmetric magnetic perturbations, toroidal mode number n=2, produced by newly installed in-vessel saddle coils in the ASDEX Upgrade tokamak show significant reduction of plasma energy loss and peak divertor power load associated with type-I edge localized modes (ELMs) in high-confinement mode plasmas. ELM mitigation is observed(More)
Electron Cyclotron Resonance Heating (ECRH) systems for next step large fusion-devices operate at a Continuous Wave (CW) power well beyond 10 MW generated by a large number of gyrotrons with typically 1 MW power per unit. The combination of the power of two (or more) gyrotrons and switching of the power between different launchers for different physics(More)
Time-resolved energy and pitch angle measurements of fast-ion losses correlated in frequency and phase with high-frequency magnetohydrodynamic perturbations have been obtained for the first time in a magnetic fusion device and are presented here. A detailed analysis of fast-ion losses due to toroidal Alfvén eigenmodes has revealed the existence of a new(More)
Remote experiment system with high network security has been developed in JT-60U. The remote experiment system is produced by personal authentication with a digital certificate and encryption of communication data to protect the JT-60U supervisory control system against illegal access. Remote experiment in JT-60U has been successfully demonstrated from(More)
The efficiency of generating a helical current in magnetic islands for the purpose of suppression of neoclassical tearing modes (NTMs) by electron cyclotron current drive (ECCD) is studied experimentally in the ASDEX Upgrade tokamak. It is found that the efficiency of generating helical current by continuous current drive in a rotating island drops(More)
ASDEX Upgrade was operated with fully W-covered wall in 2007 and 2008. Stationary H-modes at the ITER target values and improved H-modes with H up to 1.2 were run without any boronisation. The boundary conditions set by the full W-wall (high enough ELM frequency, high enough central heating and low enough power density arriving at the target plates) require(More)
A scintillator based detector for fast-ion losses has been designed and installed on the ASDEX upgrade (AUG) tokamak [A. Herrmann and O. Gruber, Fusion Sci. Technol. 44, 569 (2003)]. The detector resolves in time the energy and pitch angle of fast-ion losses induced by magnetohydrodynamics (MHD) fluctuations. The use of a novel scintillator material with a(More)
INTRODUCTION Standard operation in a future fusion reactor will aim to establish a high core density in order to harvest a maximum of output power. In addition, a high separatrix density is essential for achieving the necessary detached divertor scenario [1]. Therefore, in the ITER project and in European DEMO studies [2], core fuelling to planned target(More)
The ITER ECH system, is an in kind procurement consisting of power supplies, gyrotrons, transmission lines and launchers supplied by five parties (EU, IN, JA, RF and US). Each of these subsystems have to interface not only between themselves but also with the ITER auxiliary and control systems. The management of interfaces is therefore essential for the(More)
The orbit loss current is calculated for the ASDEX Upgrade geometry using the 5D (3D in configuration space and 2D in velocity space) Monte Carlo code ASCOT. The balance between the obtained current and the analytical estimate of the return current shows an L–H transition for the normalized collision frequency ν∗i ≈ 1 as expected from analytic theory. The(More)