At high plasma current operation, the edge of RFX-mod reversed field pinch device is characterized by a magnetic topology which is spontaneously threedimensional, with a magnetic deformation characterized by a n = -7 modulation. This peculiaredge topology influences the main properties of the plasma edge, giving them a spatial modulation with the same periodicity. The spatial modulation of the plasma-wall interaction (PWI) hasbeen characterized, measuring the influxes of the main gas and of various impurities in differenttoroidal locations of the torus, showing that the PWI footprint follows the magnetic field one. Usingmeasurements located in different poloidal positions it is also possible to show that the PWI has a clear m=1 component. PWI is then correlated with the spatial behaviour of the electron density, temperature and with their gradients measured at the edge with the thermal helium beam diagnostic; all these quantities are modulated with the same periodicity of the magnetic field. Then, the influence of the spatial modulation of these gradients on the high frequency turbulent fluctuations and blobs is shown, allowing to study the effect of the 3D edge magnetic topology on particle transport. The strong analogies with the similar edge magnetictopology obtained in Tokamak RMP experiments make the results here described quite general , proving the beneficial effects of cross-device comparison of similar physical problems.
Interaction between plasma edge properties and 3D magnetic fields
M Agostini;P Scarin;G Spizzo;N Vianello;L Carraro;
2013
Abstract
At high plasma current operation, the edge of RFX-mod reversed field pinch device is characterized by a magnetic topology which is spontaneously threedimensional, with a magnetic deformation characterized by a n = -7 modulation. This peculiaredge topology influences the main properties of the plasma edge, giving them a spatial modulation with the same periodicity. The spatial modulation of the plasma-wall interaction (PWI) hasbeen characterized, measuring the influxes of the main gas and of various impurities in differenttoroidal locations of the torus, showing that the PWI footprint follows the magnetic field one. Usingmeasurements located in different poloidal positions it is also possible to show that the PWI has a clear m=1 component. PWI is then correlated with the spatial behaviour of the electron density, temperature and with their gradients measured at the edge with the thermal helium beam diagnostic; all these quantities are modulated with the same periodicity of the magnetic field. Then, the influence of the spatial modulation of these gradients on the high frequency turbulent fluctuations and blobs is shown, allowing to study the effect of the 3D edge magnetic topology on particle transport. The strong analogies with the similar edge magnetictopology obtained in Tokamak RMP experiments make the results here described quite general , proving the beneficial effects of cross-device comparison of similar physical problems.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
