Overview of lithium injection and flowing liquid lithium results from the US–China collaboration on EAST

Andruczyk, Daniel; Maingi, R.; Hu, Jiansheng; Zuo, Guizhong; Rizkallah, Rabel; Parsons, Matthew; Shone, Andrew; O’Dea, D.; Kapat, Aveek; Szott, Matthew; Stemmley, Steven; Sun, Zhuo; Xu, Wei; Meng, X.C.; Lunsford, R.; Gilson, Erik; Diallo, A.; Tritz, K.

doi:10.1088/1402-4896/ab6ce1

Cited by 10 publications

(8 citation statements)

References 30 publications

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“…Lithium is strongly considered a liquid metal wall candidate, potentially allowing to spread and conduct heat efficiently and safely away [19][20][21]. Studies also predict it to be an effective dissipator in the lithium vapor box divertor [22,23].…”

Section: Introductionmentioning

confidence: 99%

Mitigation of plasma–wall interactions with low-Z powders in DIII-D high confinement plasmas

Effenberg¹,

Bortolon²,

Casali³

et al. 2022

Nucl. Fusion

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Experiments with low-Z powder injection in DIII-D high confinement discharges demonstrated increased divertor dissipation and detachment while maintaining good core energy confinement. Lithium (Li), boron (B), and boron nitride (BN) powders were injected in H‑mode plasmas (Ip=1 MA, Bt=2 T, PNB=6 MW, 〈ne〉=3.6-5.0·1019 m-3) into the upper small-angle slot (SAS) divertor for 2-s intervals at constant rates of 3-204 mg/s. The multi-species BN powders at a rate of 54 mg/s showed the most substantial increase in divertor neutral compression by more than an order of magnitude and lasting detachment with minor degradation of the stored magnetic energy Wmhd by 5%. Rates of 204 mg/s of boron nitride powder further reduce ELM-fluxes on the divertor but also cause a drop in confinement performance by 24% due to the onset of an n=2 tearing mode. The application of powders also showed a substantial improvement of wall conditions manifesting in reduced wall fueling source and intrinsic carbon and oxygen content in response to the cumulative injection of non-recycling materials. The results suggest that low-Z powder injection, including mixed element compounds, is a promising new core-edge compatible technique that simultaneously enables divertor detachment and improves wall conditions during high confinement operation.

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Section: Introductionmentioning

confidence: 99%

Mitigation of plasma–wall interactions with low-Z powders in DIII-D high confinement plasmas

Effenberg¹,

Bortolon²,

Casali³

et al. 2022

Nucl. Fusion

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“…The gettering and low recycling abilities of lithium are well known. Using lithium to control oxygen impurities as well as cold hydrogen coming off walls and PFC surfaces before, during, and after a discharge has been observed in several tokamak devices including NSTX [43][44][45] and EAST [21,46,47]. The complex surface chemistry has also been demonstrated in controlled single-effect in-situ experiments and modeling [39,48].…”

Section: Implications Of Low Recycling Operationmentioning

confidence: 99%

“…This provides the ability to hold a low recycling surface well after a discharge is performed [20], enabling lower amount of lithium needed per discharge. Most recently, a large multi-institutional collaboration between the U.S. and China has conducted research using lithium in various forms to help understand and control long pulse plasmas in EAST [21]. A combination of lithium powder droppers, pellet injectors and a flowing liquid lithium (FLiLi) limiter were used to suppress and control ELMs and demonstrate recycling control.…”

Section: Introductionmentioning

confidence: 99%

First lithium experiments in HIDRA and evidence of helium retention during quasi-steady-state stellarator plasma operations

Andruczyk

Koyn

Allain

et al. 2022

Plasma Phys. Control. Fusion

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Experiments in HIDRA have had operational discharges between tdischarge = 60 – 1000 s using ECRH heating. This means that quasi-steady-state plasma discharges reach conditions to study long-pulse plasma material interactions. The HIDRA-MAT PMI diagnostic is used to place a drop of lithium onto a heated tungsten surface, transfer the sample in-vacuo and expose it in a helium plasma. Helium is of interest as there is an open question to whether lithium will be able to remove helium ash in real fusion devices. It was also observed that the plasma density and temperature increased by over 2.5 times. During lithium evaporation, as significant lithium ionization occurs, there is a 91% drop in the neutral pressure that is injected into the vessel, despite a constant flow of He gas. This is backed up by the fact that the helium neutral light intensity also drops. At one point in the discharge a lithium plasma is created, as indicated by an increase in Li+ emission and a complete reduction in He+ emission, but the electron density jumps from ne = 3×1018 m-3 to over ne = 8×1018 m-3 while the core temperature stays relatively constant between Te = 16 eV – 20 eV. Once the source of lithium is expired, residual Li and Li+ in the plasma maintain a low neutral He background which allows a He plasma to re-establish and be more efficiently heated. Here the density drops down to ne = 2×1018 m-3 and the electron temperature increases from Te = 20 eV to over Te = 50 eV. This is also indicated by the He+ emission re-establishing and having a higher intensity. In this paper we show the results from the first lithium campaign in HIDRA. In the presence of lithium, the helium disappears from the plasma via an as of yet unknown complex relationship that needs to be further studied.

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“…To realize real-time wall conditioning without handling toxic borane gases, a multi-species impurity powder dropper (IPD) [2] was developed in the Princeton Plasma Physics Laboratory, and installed in the ASDEX-upgrade [3], the DIII-D tokamak [4], the EAST [5], the KSTAR [6], the Wendelstein 7-X [7] and the Large Helical Device (LHD) [8]. Its powder feeder uses a piezo-electric actuator to vibrate a trough, to advance horizontally a layer of powder off the end, and to fall into a drop tube and fall directly into the plasma gravitationally.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on boron distribution and transport at plasma-facing components during impurity powder dropping in the Large Helical Device

et al. 2022

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Toward real-time wall conditioning, impurity powder dropping experiments with boron powder were performed in the 22nd experimental campaign of the Large Helical Device (LHD). To examine the deposition and desorption process of boron, we focus on boron hydride (BH) molecules which presumably populate near plasma-facing components. We performed spatially-resolved spectroscopic measurements of emission by boron ions and boron hydride molecules. From the measurement, we found that BH and B+ were concentrated on the divertor viewing chord, which suggest boron deposition in the divertor region. By comparing Hγ emissions with and without boron injection, neutral hydrogen shows uniform reduction in the SOL region, whereas less reduction of neutral hydrogen is confirmed in the divertor region. Although emissions from BH and B+ increased linearly, emissions by B0 and B4+ became constant after the middle of the discharge. Continuous reduction of carbon density in the core plasma was confirmed even after B0 and B4+ became constant. The results may show reduction of hydrogen recycling and facilitation of impurity gettering by boron in the divertor region and thus effective real-time wall conditioning.

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Overview of lithium injection and flowing liquid lithium results from the US–China collaboration on EAST

Cited by 10 publications

References 30 publications

Mitigation of plasma–wall interactions with low-Z powders in DIII-D high confinement plasmas

Mitigation of plasma–wall interactions with low-Z powders in DIII-D high confinement plasmas

First lithium experiments in HIDRA and evidence of helium retention during quasi-steady-state stellarator plasma operations

Experimental study on boron distribution and transport at plasma-facing components during impurity powder dropping in the Large Helical Device

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