Intermittent transport in the scrape-off layer of the SINP tokamak

Abstract

Plasma structures, localized in the two-dimensional poloidal cross section propagating radially and poloidally, have been detected in the scrape-off layer of the SINP tokamak. Structures with densities both higher and lower than the density of the background plasma are present, with electron temperatures higher and lower, respectively, than that of the background plasma. These are responsible for the large and sporadic bursts of particle flux to the wall, amounting to 30%–40% of the total cross-field flux. These intermittent structures also cause the probability distribution function of the fluctuations to deviate from the Gaussian behavior, especially away from the limiter.

Edge turbulence measurements in toroidal fusion devices

“…Qualitatively similar intermittency in the edge density, potential and/or turbulent transport flux have been seen on many toroidal fusion devices, e.g. the ADITYA tokamak [141], T-10 [142], CASTOR [143,144], DIII-D [137], MAST and Tore-Supra [145], W7-AS and TJ-II [146], TJ-K [92], RFX [91,147], SINP [148] and HT-7 [149]. Generally the skewness is positive in the SOL (i.e.…”

Edge turbulence and SOL transport in tokamaks

“…Work at DIII-D [16] determined that intermittent, ballistic, events in the SOL with amplitudes above 2.5Â of the rms deviation were responsible for much of the turbulent transport [16,37] and this convective flux can cause large radial transport in regions with a shallow gradient and so can deposit particles and energy in unexpected places. Intermittent events are seen on many toroidal devices, such as the ADITYA, T-10, CAS-TOR, DIII-D, MAST and Tore-Supra tokamaks [45][46][47], and nontokamaks such as W7-AS, TJ-II, TJ-K, RFX, SINP and HT-7 [48][49][50][51][52]. The intermittency is due to coherent, long-lived filamentary structures that exist within the turbulence and that have been characterized by using imaging [53][54][55], conditional sampling [16,25,41,45,56] and wavelet analysis [57].…”

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

“…200,202,215 Thus positive density blobs are usually dominant near the outer wall of these devices, and nearly absent inside the last closed flux surface where the skewness is usually close to zero. In some cases the skewness becomes negative farther toward the plasma center, e.g., in DIII-D, 129 ASDEX-U, 169 SINP, 174 HL-2A, 126 T-10, 159 and LAPD, 130 where negative skewness defines lower-than-average density "holes" rather than blobs. In most cases these holes were observed to move radially inward 129,130,159 rather than radially outward.…”

“…197 Both positive and negative blob potentials have been observed, corresponding to positive and negative vortices, along with both monopolar and dipolar potential structures. Two dimensional spatial maps of the vortexlike potential structure of blobs have been made in W7-AS, 119 ADITYA, 172 SINP, 174 TORPEX, 132,204 TJ-K, 184 the Riso Q machine, 226 and THORELLO. 215 The relationship between the observed monopole and/or dipole potential structures and the theory of blobs is discussed in Sec.…”