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The Helium beam diagnostic is an active spectroscopic method to measure electron temperatures and densities with good spatial and temporal resolution. The method can be applied in the temperature range 10eV to several hundreds of electron volts, the density range is from 10(18)m(-3) to several 10(19)m(-3). The method is based on the comparison of measured line intensity ratios with the results of collisional radiative model. In this work, experimental aspects and the methods for the interpretation of the line intensities are investigated.

For the optimization of the spatial resolution, an optimized beam source has been developed and put into operation at the Jülich tokamak TEXTOR-94. The supersonic helium beam has a small beam divergence of ±1 degree, and an almost mono-energetic velocity.

The accuracy of the collisional radiative model has been significantly increased using the most accurate atomic data currently available and by regarding all the excited helium states with principal quantum number n³5. Measurements at TEXTOR-94 prove that the accuracy increased significantly. ly.

Additional information

Authors: BRIX M, Forschungszentrum Jülich (DE)
Bibliographic Reference: Article: Measurement of Electron Temperature and Density in the Boundary plasma of a Tokamak with a Helium Beam Diagnostic, (1998)
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