Evidence of the influence of reflections on the Zeff profile measurements and their mitigation
There is a significant interest in the reconstruction of a Zeff profile to assess the control of the plasma impurities. On Tore Supra (TS) a modified Abel inversion of the visible bremsstrahlung allows to calculate the Zeff profile. Although the total number of viewing lines of the bremsstrahlung diagnostic is small, the method gives acceptable accuracy due to the high poloidal symmetry (circularity) of the TS plasma. It had been noticed that the outer channels were often over-estimated, giving unphysically high Zeff values at the edge of 20 or more. Ideally in the case of a derived parameter like the Zeff, the parameters used in the calculation, such as ne and Te profiles, should be measured in the same toroidal location and the same poloidal plane as the bremsstrahlung. This is not possible due to access problems, and so introduces errors but not on the scale of those observed in the profile reconstruction. The Abel inversion itself, although very sensitive to noise and errors in the measurements, is also unlikely to introduce the observed over-estimation of the outer channels.
Bibliographic Reference: An oral paper given at: 31st EPS Conference on Controlled Fusion and Plasma Physics Organised by: CCLRC Rutherford Appleton Laboratory (GB); EURATOM/UKAEA Fusion Association (GB); Imperial College London Held at: Imperial College London (
Availability: Available from Association EURATOM-CEA, Departement de Recherches sur la Fusion Controlee, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: firstname.lastname@example.org
Record Number: 200417622 / Last updated on: 2004-07-13
Original language: en
Available languages: en