Coherent structures in the simple magnetised Thorello plasma C. Riccardi 1 , H.E. Roman 1 , R. Barni 1 , M. Fontanesi 1 1 Dipartimento di Fisica Occhialini, Universita' degli Studi di Milano-Bicocca, p.za della Scienza, 3 I-20216 Milano, Italy The study of turbulence in magnetized plasmas is of great importance due to its link to the practical problem of increasing the quality of plasma confinement. Indeed it is established that anomalous particle transport plays a major role in reducing the confinement in fusion devices [1] and more generally in magnetized plasmas. In the past years a consensus is arising on the role that burst-like structures plays in transport. Such kind of objects has been analysed with different techniques in several different devices, including tokamak SOLs [1-2], stellarators and reverse field pinches [3], simple magnetized tori [4] and linear Q-machine [5]. Here we report on an experimental study of coherent structures in the turbulent regime of the simple magnetized toroidal device Thorello. There a low temperature, high density steady turbulent plasma state can be produced and mantained in a hydrogen low pressure discharge [6]. Turbulence has been studied by means of multiple pin electrostatic probes. A conditional sampling analysis has been performed to detect the spatiotemporal evolution of structures in a poloidal section of the device. The Thorello device produces a hot cathode discharge in a magnetized torus, with a peculiar non-axisymmetric potential well. The plasma is produced in a steady turbulent state with a high level of electrostatic fluctuations (with rms up to 50% of their mean value, shear in the radial electric field and other interesting features [8]). Typical parameters of this very low plasma are T e ~1-4 eV, T i ~0.3 eV, n + ~5 . 10 11 cm -3 at center and decreasing by two order of magnitude in the edge. The Debye length as well as the ion Larmour radius are small everywhere. The electrostatic fluctuations of density and plasma potential are obtained by means of a Langmuir probe array, made up of four tungsten wires. The scanning probe system, developed to study a 3D portion of the plasma, has been used to characterize an area 9x8 cm 2 of the poloidal section in a grid with 323 positions. In order to apply the conditional sampling technique we also put a reference single pin probe at a fixed position in the poloidal section, toroidally apart by 3 cm. Conditional sampling has been performed on the floating potential and ion saturation current time series, requiring that a particular condition is met in the simultaneously acquired reference probe time series (such an event triggers the selection of a fixed time window out of the scanning probe time series [4]). A hundred time windows, about 100 s long, have been acquired and averaged for each 33rd EPS Conference on Plasma Phys. Rome, 19 - 23 June 2006 ECA Vol.30I, P-5.080 (2006)