Gyrokinetic simulation of dissipative trapped electron mode in tokamak edge

Abstract

The gyrokinetic simulation using the gyrokinetic toroidal code (GTC) is carried out for the dissipative trapped electron mode (DTEM), which is an important source for the electrostatic turbulence in the pedestal of tokamak plasmas. The DTEM instability is identified for the edge plasmas, and its dependence on the wavelength and collisional frequency is obtained by both simulation and theory. It is shown for the first time that the linear gyrokinetic simulation results are fully consistent with that from the analytic theory with edge parameters. This suggests that the GTC code can simulate accurately the DTEM instability in the pedestal. It provides a useful benchmark for verifying gyrokinetic simulation of edge plasmas.

Study on pedestal fluctuations in H-modes without large ELMs during the transition to a detached tungsten divertor in EAST

“…The ECM is a quasi-electrostatic instability, with a high toroidal mode number (n = 15-20) and a typical poloidal wavelength of about 8 cm measured near the low-field-side mid-plane, and a predominantly electrostatic mode together with a very small magnetic component (δB/B P ∼ 10 −4 ) [16]. The GYRO, Bout++ and GTC simulations consistently suggest that the ECM may share the nature of the dissipative trapped electron mode (DTEM) [16,55,56]. The transport capability of the ECM is strong, which can drive close to 0.2-0.4 MW of heat and 2-4 × 10 20 m −2 s −1 particle flux exhaust through the separatrix, as measured by the reciprocating probe arrays [16].…”

Gyrokinetic analysis and simulation of pedestals to identify the culprits for energy losses using ‘fingerprints’

“…Earlier simulations in the literature [8,[15][16][17][18][19][20], and analysis and simulations here, strongly support this expected behavior. Since the modes listed in Table1B may be excited in pedestals of some larger machines of today, and of future (lower velocity shear) devices [18][19][20]42], we will also include ITG/TEM modes [15][16][17][18][19][20][42][43][44][45] in our investigations, both for completeness and for future applications. It must be, however, stressed that these modes are generally suppressed for many pedestal parameters on present tokamaks; in fact, their suppression is what leads to the very formation of the pedestal.…”

Experimental study on low recycling no-ELM high confinement mode in EAST

“…However, recent studies [27] have found that the appearance of MCM can effectively induce the poloidal redistribution of the particle flux deposited on divertor plates, resulting in a peak heat flux reduction by ~20%. ③ Experiments and GYRO/Bout + +/GTC simulations indicate that ECM may be of the nature of DTEM [23,28,29]. However, the nature of MCM is still unclear.…”