Improvement of the spatial resolution of the TCV Thomson scattering system has permitted measurements of the pedestal height and gradient of electron density and temperature profiles near the plasma boundary during ELMy H-mode. Measured profiles were fitted by a modified TANH function and characterized by pedestal height, width and gradient scale length. Taking advantage of an extended quasi-stationary phase with reproducible edge localized modes (ELMs), random sampling was used to reconstruct the time evolution during a typical ELM cycle. The measurements clearly reveal the influence of the ELM event on the edge profiles and have permitted quantification of the associated energy and particle losses. The experimental data, collected from a series of reproducible shots have provided the basis for an MHD stability analysis using the KINX code. The results confirm the type-III identification of the ELMs observed in ohmically heated H-mode plasmas in TCV.
Introduction to the ELMs special issue