Pedestal formation after L-H transition in ASDEX Upgrade

Abstract

Introduction The H-mode is the foreseen standard scenario for ITER. The initially installed heating power of ITER is expected to be around the H-mode power threshold of the initial H2 or He plasma operation [1]. Therefore, the achievement of a sustained H-mode will be very sensitive to the development of the pedestal for heating powers close to the power threshold (PHeat/PThres ' 1). Figure 1: The plasma and divertor current (a & b), the heating power (c & d), the gas fuelling and the line integrated density (e & f) for both discharges (#25438 & #25440) are shown. Red shaded areas indicate H-mode phases. The ASDEX Upgrade tokamak is well equipped with plasma edge diagnostics, which deliver routinely detailed electron density and temperature measurements with a high spatial and temporal resolution. Within the available heating scenarios, it is even possible to achieve Hmode using electron cyclotron resonance heating (ECRH) only. In contrast to neutral beam heating (NBI), ECRH is not accompanied with a particle source in the confined plasma.