NIFS-853

FULL TEXT (PDF, 570 KB)


Author(s):

S. Kado et al.

Title:

Dynamics of the Pedestal Structure in the Edge Transport Barrier in CHS

Date of publication:

Oct. 2006

Key words:

21 IAEA Fusion Energy Conference , EX/P8-1

Abstract:

The dynamic behavior of the edge pedestal in the edge transport barrier (ETB) formation discharge (H-mode) [Okamura S. et al., J. Plasma Fusion Res. 79 (2003) 977] in the compact helical system (CHS) is investigated. Edge Harmonic Oscillations (EHOs) having a fundamental frequency of 2-4.5 kHz, depending on the magnetic configuration, and their second harmonic are observed when the density gradient of the pedestal reaches a certain threshold. There are two groups of so-called EHOs in the CHS. One is located in the edge region where the iota = 1 surface exists, and the other is in the core region (although we also call it EHO in this paper) around the half radius where the iota = 0.5 surface exists. The magnetic probe signal is revealed to reflect the latter mode, showing the poloidal mode number of 2, while that for the edge BES channel is 1. The density build-up saturates simultaneously with the increase of EHOs in the edge BES channel, which suggests that to a considerable extent the mode increases the particle transport.

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