Observation of internal transport barrier in ELMy H-mode plasmas on the EAST tokamak

Abstract

The internal transport barrier (ITB) has been obtained in ELMy H-mode plasmas by neutron beam injection and lower hybrid wave heating on the Experimental Advanced Superconducting Tokamak (EAST). The ITB structure has been observed in profiles of ion temperature, electron temperature, and electron density within ρ<0.5. It was also observed that the ITB formation is stepwise. Due to the ITB formation, the confinement quality H 98y2 increases from 1 to 1.1 and the normalized beta, β N , increases from 1.5 to near 2. The fishbone activity observed during the ITB phase suggests the central safety factor q(0)∼1. Transport coefficients are calculated by particle balance and power balance analysis, showing an obvious reduction after the ITB formation.

Saturation of fishbone instability by self-generated zonal flows in tokamak plasmas

“…This strong E × B suppression is consistent with the ITB arising experimentally after fishbone bursts in the DIII-D discharge. It confirms the long suspected role of fishbones in ITB formation [22], fishbone bursts having been observed to precede ITBs in ASDEX [23], MAST [24][25], HL-2A [4] and EAST [26][27] plasmas. Finally, gyrokinetic simulations find that the fishbone-induced EP transport in the ITER scenario is marginal, 2% of the core EPs being redistributed, similar to previous studies on the alpha fishbone in ITER DT scenarios [19].…”

A simple model for internal transport barrier induced by fishbone in tokamak plasmas

“…Upon the flow shear exceeding the critical value given by (2.22), the turbulent fluctuation level reduces to zero and the ion pressure gradient attains the high-confinement state, assisting ITB formation. The transition process shown in figure 3 is stepwise, which coincides with the EAST experiments (Yang et al 2017;Chu et al 2022). Note that in Chu et al (2022), the experimental results showed that the higher NBI heating power leads to the stronger ITB.…”

“…In addition, it has been revealed that fishbone instability is often excited after the ITB formation, and it plays no role in triggering ITB; however, ITBs with fishbone are stronger than without fishbone (He et al 2022). In EAST tokamak, ITB formation is stepwise and always appears after the fishbone instability (Yang et al 2017;Liu et al 2020). It is identified that ITB formation in the ion thermal channel strongly correlates to the excitation of the fishbone (Chu et al 2021;Zhang et al 2022).…”

“…In EAST tokamak, ITB formation is stepwise and always appears after the fishbone instability (Yang et al. 2017; Liu et al. 2020).…”

Transport barrier in 5D gyrokinetic flux-driven simulations

“…Many tokamaks are able to trigger ITBs (e.g. EAST [16], KSTAR [17], JET [18], DIII-D [19] and JT-60U [20]) or ETBs (e.g. DIII-D [21] [22], JFT-2M [23], Alcator C-mod [24], JET [25], ASDEX [13] and ASDEX Upgrade [26] [27], COMPASS [28] and MAST [29]) when a certain power threshold is exceeded.…”