Properties of vacuum-deposited Li films and impact on plasma performance in TJ-II

Tabarés, F.L.; Tafalla, D.; Ferreira, J. A.; Ochando, M. A.; Medina, F.

doi:10.1016/j.fusengdes.2010.04.026

Cited by 8 publications

(5 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Some studies suggest that edge plasma control is a 'hidden factor' in achieving high plasma performance [30][31][32]. We observed a decrease in the intensity of the H-alpha signal, indicating a decreased neutral density in the edge region.…”

Section: Discussionmentioning

confidence: 51%

Improvement of core heat transport in NBI plasmas of heliotron J using high-intensity gas puffing

Wang,

Kobayashi,

Nagasaki

et al. 2024

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

Controlling the heat transport profile is important for high performance in magnetically confined fusion plasmas. In this study, improved electron heat transport was achieved in neutral beam injection (NBI) plasmas by applying high-intensity gas puffing (HIGP) on a stellarator/heliotron device called Heliotron J. Compared with conventional gas puffing (GP) fueling discharge, a higher and more peaked electron temperature profile was obtained, and the core ion temperature was slightly higher but similarly shaped. Using similar parameters, the electron density profile for HIGP remained similar and differed from that of the ECH-eIBT plasma. Transport analysis using the FIT3D and TR-SNAP codes showed a clear reduction in the electron heat transport coefficient in the plasma core region. However, more detailed experiments are required to understand the mechanisms underlying this improvement fully.

show abstract

Section: Discussionmentioning

confidence: 51%

Improvement of core heat transport in NBI plasmas of heliotron J using high-intensity gas puffing

Wang,

Kobayashi,

Nagasaki

et al. 2024

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…The use of lithium has allowed routine operation with the two neutral beam injectors. Clear transitions to the enhanced confinement mode (H-Mode) and strongly peaked plasma profiles were observed under the lithiumized wall conditions [32].…”

Section: Improved Plasma Confinement and Performance With Lithiummentioning

confidence: 96%

“…An H-mode lasting 6.4 seconds and limited only by the available OH flux consumption was subsequently attained. In TJ-II, application of lithium together with boronization was used to attain clear transitions to the H-mode, which essentially doubled the plasma energy confinement [32].…”

Section: Lithium Influence On H-modementioning

confidence: 99%

Lithium As Plasma Facing Component for Magnetic Fusion Research

Ono¹

2012

View full text Add to dashboard Cite

The use of lithium in magnetic fusion confinement experiments started in the 1990's in order to improve tokamak plasma performance as a low-recycling plasma-facing component (PFC). Lithium is the lightest alkali metal and it is highly chemically reactive with relevant ion species in fusion plasmas including hydrogen, deuterium, tritium, carbon, and oxygen. Because of the reactive properties, lithium can provide strong pumping for those ions. It was indeed a spectacular success in TFTR where a very small amount (~ 0.02 gram) of lithium coating of the PFCs resulted in the fusion power output to improve by nearly a factor of two. The plasma confinement also improved by a factor of two. This success was attributed to the reduced recycling of cold gas surrounding the fusion plasma due to highly reactive lithium on the wall. The plasma confinement and performance improvements have since been confirmed in a large number of fusion devices with various magnetic configurations including CDX-U/LTX (US), CPD (Japan), HT-7 (China), EAST (China), FTU (Italy), NSTX (US), T-10, T-11M (Russia), TJ-II (Spain), and RFX (Italy). Additionally, lithium was shown to broaden the plasma pressure profile in NSTX, which is advantageous in achieving high performance H-mode operation for tokamak reactors. It is also noted that even with significant applications (up to 1,000 grams in NSTX) of lithium on PFCs, very little contamination (< 0.1%) of lithium fraction in main fusion plasma core was observed even during high confinement modes. The lithium therefore appears to be a highly desirable material to be used as a plasma PFC material from the magnetic fusion plasma performance and operational point of view. An exciting development in recent years is the growing realization of lithium as a potential solution to solve the exceptionally challenging need to handle the fusion reactor divertor heat flux, which could reach 60 MW/m 2. By placing the liquid lithium (LL) surface in the path of the main divertor heat flux (divertor strike point), the lithium is evaporated from the surface. The evaporated lithium is quickly ionized by the plasma and the ionized lithium ions can provide a strongly radiative layer of plasma ("radiative mantle"), thus could significantly reduce the heat flux to the divertor strike point surfaces, thus protecting the divertor surface. The protective effects of LL have been observed in many experiments and test stands. As a possible reactor divertor candidate, a closed LL divertor system is described. Finally, it is noted that the lithium applications as a PFC can be quite flexible and broad. The lithium application should be quite compatible with various divertor configurations, and it can be also applied to protecting the presently envisioned tungsten based solid PFC surfaces such as the ones for ITER. Lithium based PFCs therefore have the exciting prospect of providing a cost effective

show abstract

“…The freshly deposited Li coating was intentionally covered by a boron layer with a thickness of some tens of nanometer, and the expected yield reduction by a factor of 10 was observed, but no conclusion could be drawn about any possible threshold change, due to the low values of the Li emission data [21]. Interestingly, very good recycling conditions (R < 20%) were obtained even when the Li layer was buried by boron, thus suggesting an important role of bulk lithium uptake on the improved particle trapping effect.…”

Section: Sputtering By H Plasmas In Tj-iimentioning

confidence: 99%