Fluctuation measurements with emissive probes in tokamaks *) J. ADAMEK, I. DURAN, M. HRON, J. STOCKEL Institute of Plasma Physics, Association EURATOM/IPP.CR, Prague, Czech Republic P. BALAN, R. SCHRITTWIESER, C. IONITA Department of Ion Physics, University of Innsbruck, Innsbruck, Austria E. MARTINES Consorzio RFX, Associazione EURATOM/ENEA sulla Fusione, Padova, Italy M. TICH~ Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic G. VAN OOST Department of Applied Physics, Ghent University, Gent, Belgium Received 11 September 2002 A new probe head, composed of two electro-emissive probes and two Langmuir probes has been designed to measure edge fluctuations in the CASTOR tokamak. In this con- tribution, only one Langmuir and one electron-emissive probe are used to measure the temperature and potential fluctuations and the phase angle between them. PACS: 52.35.Ra, 52.25.Gj Key words: tokamak, edge plasma, plasma fluctuation, emissive probe 1 Introduction The particle losses at the tokamak edge are governed by the fluctuation induced flux F ~_ (hnhVr)T, which correlates fluctuations of the density 5n and the radial velocity 5yr. The radial particle transport appears due to the 5/~pol x/3tot drift. The poloidal electric field fluctuations 5Epol are usually measured by two Langmuir probes, which are located at the same magnetic surface and spaced poloidally. Then, the poloidal electric field between them is calculated as the difference of their floating potentials divided by their poloidal distance. This approach requires, however, the assumption that fluctuations of the elec- tron temperature are either negligible, or identical. This is because the difference between the floating potential of Langmuir probe Vc and the plasma potential ¢ is kBhTe 5¢ - 5Vc = a - - (1) e *) Presented at 5th Workshop "Role of Electric Fields in Plasma Confinement and Exhaust", Montreux, Switzerland, June 23-24, 2002 Czechoslovak Journal of Physics, Vol. 52 (2002), No. 10 1115