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%.