Introduction- The RFX Reversed Field Pinch experiment (a=0.46 m,R = 2 m) has

been so far operated with plasma currents up to 1.2 MA, electron densities in the range 1- 9 1019m-3 and electron temperatures between 200 and 400 eV. The first wall is made of graphite tiles, which cover all over the vessel with a surface of approximately 36 m2. Average particle confiment time is of the order of few milliseconds and in order to sustain the electron densit