Characteristics of the core and edge plasma turbulence in small Tokamaks

A joint experimental work on small tokamak , namely CASTOR of IPP Pragu, Czech Republic (2005), T-10 at PPC, Moscow, Russia (2006), ISTTOK at IST, Lisbon, Portugal (2007) and IR-T1 at PPRC, Tehran, Iran, was organized with the aim to diagonize and characterize the core and the edge plasma turbulence in a tokamak in order to investigate correlations between the occurrence of transport barriers, improved confinement, electric fields and electrostatic turbulence using advanced diagnostics with high spatial and temporal resolution. On CASTOR and ISTTOK, electric fields were generated by biasing an electrode inserted into the edge plasma and an improvement of the global particle confinement induced by the electrode positive biasing has been observed. Geodesic Acoustic Modes were studied using heavy ion beam diagnostics (HIBD) on T-10 and ISTTOK and correlation reflectometry on T-10. ISTTOK is equipped with gallium jet injector and the technical feasibility of gallium jets interacting with plasmas has been investigated in pulsed and AC operation. The effect of internal inductance on plasma position based on toroidal flux loop (diamagnetic loop) and magnetic probe was investigated on IR-T1 tokamak. The first JEs have clearly demonstrated that small tokamaks are suitable for broad international cooperation to conduct dedicated joint research programmes. Other activities within the IAEA CRP on JRUST are also overviewed.