First observations of ELM triggering by injected lithium granules in EAST

Mansfield, D. K.; Roquemore, A. L.; Carroll, Thomas J.; Sun, Zheng; Hu, Jiansheng; Zhang, L.; Liang, Y.; Gong, X.Z.; Li, J.G.; Guo, H.Y.; Zuo, Guizhong; Parks, P.B.; Wu, Wen; Maingi, R.

doi:10.1088/0029-5515/53/11/113023

Cited by 75 publications

(52 citation statements)

References 21 publications

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“…240 It should be also noted that this ELM triggering is also known as the ELM pacing, and other techniques such as the repetitive lithium granular injection and vertical jogs have been successfully developed. 244,245 VII. BOUNDARY PHYSICS…”

Section: -39mentioning

confidence: 98%

“…The system was originally designed as another approach for lithium wall conditioning in NSTX, but its potential for ELM pacing as well was demonstrated on EAST. 244 Solid PFC coatings that result from techniques like lithium evaporation are difficult to extrapolate to long-pulse applications. The availability of lithium only on the PFC surface limits the amount of deuterium it can bind, and any solid PFC is subject to long-term damage in a fusion reactor environment.…”

Section: Plasma Facing Materials and Lithium Researchmentioning

confidence: 99%

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Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ∼ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ∼ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

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Section: -39mentioning

confidence: 98%

Section: Plasma Facing Materials and Lithium Researchmentioning

confidence: 99%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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“…The Lithium Granule injector (LGI) installed at EAST is a modification of a piezoelectric aerosol injector first deployed on NSTX [25] and subsequently tested on EAST [26] is shown in Figure 2. Since its inception, the powder injector has undergone a number of design improvements; principle among these is the ability to change granule size by active chamber selection without having to open the LGI to atmosphere.…”

Section: Injector Descriptionmentioning

confidence: 99%

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

et al. 2018

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The ability of an injected lithium granule to promptly trigger an edge localized mode (ELM) has been established in multiple experiments. By horizontally injecting granules ranging in diameter from 200 microns to 1mm in diameter into the low field side of EAST H-mode discharges we have determined that granules with diameter > 600 microns are successful in triggering ELMs more than 95% of the time. It was also demonstrated that below 600 microns the triggering efficiency decreased roughly with granule size. Granules were radially injected from the outer midplane with velocities ~ 80 m/s into EAST upper single null discharges with an ITER like tungsten monoblock divertor. These granules were individually tracked throughout their injection cycle in order to determine their efficacy at triggering an ELM. For those granules of sufficient size, ELM triggering was a prompt response to granule injection. By simulating the granule injection with an experimentally benchmarked neutral gas shielding (NGS) model, the ablatant mass deposition required to promptly trigger an ELM is calculated and the fractional mass deposition is determined.

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“…A cutaway of the granule injector is shown in Fig. 1, and described in more detail in reference [9]. While the injector has been tested on several different types of impurity granules, the experiments discussed herein are confined to the injection of lithium granules, due to the low atomic number of lithium and the documented beneficial effects of the application of lithium doses in high confinement discharges [10,11].…”

Section: Lithium Granule Injectormentioning

confidence: 99%

Lithium granule ablation and penetration during ELM pacing experiments at DIII-D

Lunsford

Bortolon

Roquemore

et al. 2016

Fusion Engineering and Design

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Available online xxx a b s t r a c t At DIII-D, lithium granules were radially injected into the plasma at the outer midplane to trigger and pace edge localized modes (ELMs). Granules ranging in size from 300 to 1000 microns were horizontally launched into H-mode discharges with velocities near 100 m/s, and granule to granule injection frequencies less than 500 Hz. While the smaller granules were only successful in triggering ELMs approximately 20% of the time, the larger granules regularly demonstrated ELM triggering efficiencies of greater than 80%. A fast visible camera looking along the axis of injection observed the ablation of the lithium granules. The duration of ablation was used as a benchmark for a neutral gas shielding calculation, and approximated the ablation rate and mass deposition location for the various size granules, using measured edge plasma profiles as inputs. This calculation suggests that the low triggering efficiency of the smaller granules is due to the inability of these granules to traverse the steep edge pressure gradient region and reach the top of the pedestal prior to full ablation.Published by Elsevier B.V.

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First observations of ELM triggering by injected lithium granules in EAST

Cited by 75 publications

References 21 publications

Recent progress on spherical torus research

Recent progress on spherical torus research

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

Lithium granule ablation and penetration during ELM pacing experiments at DIII-D

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