Zeff profiles measured by visible and soft x‐ray bremsstrahlung arrays in TFTR (abstract)a)

The Zeff profiles from the tangential array of visible bremsstrahlung (VB) emission (5235 A) have shown several interesting features in TFTR. The observed Zeff profile was flat during the ohmic phase and hollow during the neutral‐beam heating phase. In order to crosscheck the measured Zeff profiles from the VB array, a poloidal array which measures bremsstrahlung emission in the soft x‐ray region has been analyzed. The analysis of array measurements in the two different spectral regions was performed on the same geometry determined from the Abel inversion of the electron density (interferometry). The two independent measurements of Zeff profiles have been consistent with each other for most of the discharges in TFTR. However, in a discharge where the two measurements are inconsistent, the Zeff profile deduced from the VB array indicates some degree of problems. In this paper, the detailed analysis of the bremsstrahlung array (both poloidal and tangential) measurements is presented. Particularly, the effec...