Blob properties in full-turbulence simulations of the TCV scrape-off layer

Abstract

To investigate blob properties in the tokamak scrape-off layer (SOL), we perform dedicated numerical nonlinear simulations of plasma turbulence in the SOL of a TCV discharge using the Global Braginskii Solver code. A blob detection technique is used for the first time in a threedimensional (3D) full-turbulence simulation to track the motion of the filaments in the SOL. The specific size, density amplitude and radial velocity of the blobs are computed, with the typical values being 7.4 s r , n 0.33 e and c 0.016 s , respectively. The analysis of blob structure in the parallel direction shows that the blobs are partially detached from the limiter. The cross correlation analysis shows how the blobs are born all along the entire field line, not being generated primarily on the low field side SOL and expanding towards the limiter. The blob radial velocity agrees well with the inertial branch of the existing scaling law. The radial particle and heat fluxes given by blobs are shown to be responsible of up to 100% and 70% of the turbulent particle and heat flux in the far SOL, respectively. The results of a second simulation with a 40 times higher resistivity are also discussed.

A drift-kinetic analytical model for scrape-off layer plasma dynamics at arbitrary collisionality

“…For example, for a typical JET discharge (Erents et al 2000;Liang et al 2007;Xu et al 2009) with the SOL parameters B T = 2.5 T, T e ∼ T i ∼ 20 eV, n e ≃ 10 19 m −3 , and k ⊥ ∼ 1 cm −1 , we obtain ǫ ν ∼ 0.016 and ǫ ∼ 0.0182. For a medium-size tokamak such as TCV (Rossel et al 2012;Nespoli et al 2017), estimating B T = 1.5 T, T e ∼ T i ∼ 40 eV, n e ≃ 6 × 10 18 , and k ⊥ ∼ 1 cm −1 , we obtain ǫ ν ∼ 6.2 × 10 −3 and ǫ ∼ 0.043. Finally, for small-size tokamaks such as ISTTOK (Silva et al 2011;Jorge et al 2016), with B T = 0.5 T, T e ∼ T i ∼ 20 eV, n e ≃ 0.8 × 10 18 , and k ⊥ ∼ 1 cm −1 , we obtain ǫ ν ∼ 0.0072 and ǫ ∼ 0.091.…”

Isotope effect on blob-statistics in gyrofluid simulations of scrape-off layer turbulence

“…Further studies, not making smallness assumpations on the relative amplitude of perturbations compared to the background should be executed, preferably through a full-f 3D gyrofluid (or gyrokinetic) computational model in order to check the statistical dependency of blob properties [12,26,47,48].…”

Blob velocity scaling in diverted tokamaks: A comparison between theory and simulation

“…Considering a selfconsistent simulation of a TCV discharge in a limited configuration, in Ref. 25, a pattern-recognition algorithm for blob tracking showed good agreement of the blob velocity with the theoretical scalings.…”

“…30 In the present work, we extend the use of the pattern recognition algorithm introduced in Ref. 25 to analyse the blob motion in a full SOL turbulent simulation in a double-null configuration. The simulation is carried out with the GBS code.…”