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Aachen PK 2003 – scientific programme

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P: Plasmaphysik

P 1: Plasma Wall Interaction

P 1.6: Talk

Monday, March 17, 2003, 17:25–17:45, FO1

Modulated Supersonic Helium Beam for the Measurement of Electron Temperature and Density Fluctuations — •Uron Kruezi, U. Samm, O. Schmitz, B. Schweer, and B. Unterberg — Institut für Plasmaphysik, FZ Jülich, EURATOM-Association, TEC, 52425 Jülich, Germany

A supersonic helium beam diagnostic has been developed for measurements of electron temperature and density fluctuations in the boundary plasma of the tokamak TEXTOR.
For the measurement of the expected fluctuation wavenumber spectra up to kr=3mm−1 a sufficient spatial resolution in radial direction is needed. A small beam width of about Δp=10mm in poloidal direction is necessary to avoid a significant influence of the poloidal components of the fluctuation. Furthermore a sufficient high signal to noise ratio for the expected frequency range up to ν=250kHz is required. These requirements have been fulfilled by the respective following measures: (i) The injection system has been located at its nearest position with respect to the observation volume. The technical constraints (pump efficiency, temperature) at TEXTOR allow a distance of 350mm with a beam divergence of ±1. (ii) The helium-pre-pressure has been raised up to 70bar. As a consequence only a pulse duration up to 100ms is possible without disturbance of the supersonic beam. This diagnostic setup allows for the typical range of plasma parameters 10eV<Te<200eV, 1018 m−3<ne<2·1019 m−3 and with a spatial and temporal resolution of Δ r≃2mm and t≥2 µ s the measurement of relative fluctuation amplitudes for the electron temperature and density down to 1%.

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