First Results of ELM Triggering With a Multichamber Lithium Granule Injector Into EAST Discharges

Numerical simulation of Li-pellet injection experiments for ELM-pacing in EAST

“…The density peak goes a little further than the max ablation position along the pellet trajectory but their separation becomes shorter as the target plasma becomes denser and hotter, indicating more ionizations take place. As can be seen from table 2, the lifetimes of injected pellets from simulation are in good agreement with those from experiments [16]. The difference in the lifetime between the simulation and experiments may come from both sides: the ablation model was developed based on a few approximations, and it introduced empirical constants; the diagnostics had many approximations, too.…”

“…A sketch of the lithium granules injector (LGI) on EAST is shown schematically in figure 1(a). The LGI has been developed as a tool for ELM control in EAST and is capable of filtering spherical granules of 0.2 to 1.0 mm by means of a granule hopper [16]. It drops the granules gravitationally along the vertical tube, and then uses an impeller to strike them into the main chamber horizontally from the outer-mid-plane (OMP) at a speed ranging from 30 to 110 m s −1 .…”

“…The maximum frequency can be about 800 Hz for the smallest size granules. Specifications about the experiment setup and operation can be found in [16].…”

“…Besides, advantages of low-Z impurity for improving plasma performance by wall conditioning had been reported in lithium related experiments [12][13][14][15]. Following these pioneering works, many positive results of Li-pellet ELM triggering were then obtained in several important fusion devices, such as EAST [16][17][18], DIII-D [19], ASDEX-U [20] and NSTX-U [21].…”

Injected mass deposition thresholds for lithium granule instigated triggering of edge localized modes on EAST

“…Injection of lithium microgranules into the edge of EAST H-mode discharges has been shown [20] to produce pedestal localized pressure perturbations which can be sufficient to trigger an ELM. Present understanding [21] describes the creation of an ELM as an excursion of the pedestal pressure past a ballooning stability threshold.…”