NSTX plasma operation with a Liquid Lithium Divertor

Kugel, H.; Allain, Jean Paul; Bell, M.G.; Bell, R.E.; Diallo, A.; Ellis, R.; Gerhardt, S. P.; Heim, B.; Jaworski, M. A.; Kaita, R.; Kallman, J.; Kaye, S. M.; LeBlanc, B.P.; Maingi, R.; McLean, A.G.; Ménard, J.; Mueller, D.; Nygren, R.E.; Ono, M.; Paul, S. F.; Raman, R.; Roquemore, A. L.; Sabbagh, S.A.; Schneider, H.; Skinner, C.H.; Soukhanovskii, V.; Taylor, Chase N.; Timberlake, J.; Viola, M.; Zakharov, L.

doi:10.1016/j.fusengdes.2011.07.010

Cited by 77 publications

(41 citation statements)

References 18 publications

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“…For example, the fueling required to achieve and maintain stable discharges was comparable to what was needed when graphite PFCs were coated with solid lithium. 295,300 There is also no significant change in the confinement time over the run year over during which NSTX plasmas were exposed to the LLD, as shown in Fig. 98.…”

Section: -46mentioning

confidence: 93%

“…Plasmas 22, 040501 (2015) 0.25 mm stainless steel liner was braised to 2.2 cm copper. 295 The heat loads to the NSTX divertor were considerably higher compared to LTX PFCs, so the thickness of the liner was greatly reduced to insure that the thermal response was determined by the copper. The stainless steel surface was plasma-sprayed with molybdenum (Mo) create a 0.17 mmthick layer with 45% porosity.…”

Section: -46mentioning

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: -46mentioning

confidence: 93%

Section: -46mentioning

confidence: 99%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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“…It should be noted that more than one ion species is present in the NSTX plasma and these exhibit some complex behavior, though the total electron content remained constant. The interested reader is referred to the associated paper on the LLD performance [31].…”

Section: Resultsmentioning

confidence: 99%

“…It is described in detail in refs. [5] and [31]. The Langmuir probe array used for this study is situated in between toroidal segments of the LLD and has been described elsewhere as well [7,8].…”

Section: Apparatus and Approachmentioning

confidence: 99%

Modification Of The Electron Energy Distribution Function During Lithium Experiments On The National Spherical Torus Experiment

Jaworski¹,

Gray²,

Kaita³

et al. 2011

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The National Spherical Torus Experiment (NSTX) has recently studied the use of a liquid lithium divertor (LLD). Divertor Langmuir probes have also been installed for making measurements of the local plasma conditions. A non-local probe interpretation method is used to supplement the classical probe interpretation and obtain measurements of the electron energy distribution function (EEDF) which show the occurrence of a hot-electron component. Analysis is made of two discharges within a sequence that exhibited changes in plasma fueling efficiency. It is found that the local electron temperature increases and that this increase is most strongly correlated with the energy contained within the hot-electron population. Preliminary in- scrape-off layer (SOL) plasma. The decrease in plasma fueling efficiency, increase in local temperature, and increase in hot-electron fraction are all consistent with an absorbing surface intercepting the SOL plasma.

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“…However, to overcome problems such as temperature dependent chemical sputtering, radiation enhanced sublimation, and other thermophysical properties associated with traditional PFCs, namely, graphite and beryllium, lithium has also become an attractive candidate, not only due to its low-Z and good thermophysical properties but also due to its ability to absorb impinging species, which can lead to a high temperature/low density or "low-recycling" regime. 11 Lithium almost completely absorbs impinging protons (and other hydrogen isotopes) which is associated with the formation of lithium hydride. This feature results in near zero recycling of the plasma on the lithium surface when practically no hydrogen comes back from the surface into the plasma (assuming lithium is not saturated with hydrogen).…”

Section: Introductionmentioning

confidence: 99%

Influence of plasma surface interactions on tokamak startup

Goswami¹

2013

Physics of Plasmas

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The startup phase of a tokamak is a complex phenomenon involving burnthrough of the low-Z impurities and rampup of I p , the plasma current. The design considerations of a tokamak are closely connected with the startup modeling. Plasma evolution is analysed using a zero-dimensional model. The particle and energy balance is considered of two subclasses of plasmas which are penetrable by neutral gas, together with another component, neutrals trapped in the wall. The first subclass includes plasmas being penetrated by slow neutrals of ($few eV) temperature. The second includes plasmas being penetrated only by fast neutrals having a temperature comparable to that of the ions. The impact of impurities on energy balance is considered through their generation by ion induced desorption of adsorbed oxygen on the first wall and physical and chemical sputtering of carbon. The paper demonstrates self-consistently that the evolution of initial phase of the discharge is intimately linked to the condition of the plasma facing components (PFCs) and the resultant plasma surface interactions. V C 2013 AIP Publishing LLC. [http://dx.

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NSTX plasma operation with a Liquid Lithium Divertor

Cited by 77 publications

References 18 publications

Recent progress on spherical torus research

Recent progress on spherical torus research

Modification Of The Electron Energy Distribution Function During Lithium Experiments On The National Spherical Torus Experiment

Influence of plasma surface interactions on tokamak startup

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