15th Topical Conference on High Temperature Plasma Diagnostics, 19 a 22 de Abril de 2004, San Diego, USA

	FM-CW Reflectometry Measurments of Plasma Position in ASDEX Upgrade  ELMY-H Mode Regimes
	F. Silva, M. Manso e a Equipa ASDEX Upgrade
	Resumo
	In ITER a set of poloidaly distributed FM-CW reflectometers is proposed for position (plasma-wall gaps) and shape (separatrix position) control during the long flat-top phase of the discharges. We report on the study performed in ASDEX Upgrade, in ELMy H-mode regime (an ITER reference scenario), to assess the quality of such control oriented measurements. Apart from gap measurements we also estimate the position of the plasma separatrix, at the low and high field sides, using a scaling law between the linear average density and the density at separatrix. The degradation of the measurements due to ELM activity is analysed and practical solutions to overcome the problem are discussed. Measurement accuracy is cross-checked with other diagnostics and compared to 1D numerical simulation results. Error bars are established based on the influence of the non probed edge plasma region on profile reconstruction and on different levels of simulated plasma density fluctuations.