Study of lithium influx, radiation, transport and influence on plasma parameters in the T-10 tokamak

Abstract

An investigation of lithium influx to plasma, radiation, transport, and its influence on plasma parameters is carried out using spectroscopy and transport modeling methods. The lithium source in the discharge of the T-10 tokamak is a moving Li-limiter based on a tungsten capillary-pore system (CPS). A strong dependence is found between the Li influx to plasma on the distance between the Li-limiter and plasma current boundary in the scrape-off layer (SOL) region. It is shown that if the Li-limiter is located on the radius of the chamber wall (r≈40 cm), lithium influx to plasma is at a low level with a value ∼2•10 18 s −1 and the Li nuclei concentration in the plasma does not exceed ∼0.5% of electron density n e with the effective charge value Z eff ≈1.2. If the Lilimiter is moved to the current radius (a L =30 cm), lithium influx to plasma reaches ∼3•10 20 s −1 , which leads to a formation of lithium plasma with the density limit of • » n 0.5 e Gw (the Greenwald density limit) with a Z eff value of ≈2.9 and ≈10% of the remaining deuteron density. In this case, the lithium radiation losses power estimated in Li-plasma is extremely low and does not exceed ≈15% of ohmic power. All obtained results are interpreted using transport models. Changing the lithization level of the chamber walls can significantly reduce the level of C, O, and W impurities and greatly affect the Z eff values. The dependencies of energy confinement times in the electron and ion components on the value of the averaged electron density are investigated in regimes with significantly varying Z eff values. The paper presents the computational analysis of the lithium radiation power at the plasma periphery and in the SOL as a function of boundary conditions, transport characteristics, and confinement times of lithium ions.

Modeling the vapor shielding of a liquid lithium divertor target using SOLPS 4.3 code

“…T-15MD is a medium-sized tokamak with a major radius R = 1.48 m, a minor radius a = 0.67 m, and copper coils providing the toroidal magnetic field. At full power, the project presumes up to 24 MW of auxiliary heating power and a pulse duration of approximately 10 s. Following the successful series of lithium limiter experiments conducted on the T-10 tokamak [15], similar experiments with either a lithium emitter-collector system or a lithium divertor target are being considered for the T-15MD research program [16].…”

Impact of T i/T e ratio on ion transport based on EAST H-mode plasmas

“…Therefore, electron heat transport in plasmas with different T i /T e ratios is essential for the study of magnetic confinement fusion. So far, the research of electron heat transport has been performed on many tokamak and stellarator devices (NSTX [3], ASDEX Upgrade [4][5][6][7][8], DIII-D [9][10][11], JT-60U [12], JET [13][14][15][16][17], W7-X [18,19], T-10 [20][21][22], TJ-II [23]). Experimentally, ion temperature (T i ) clamping occurring at T i ~ 1.5 keV independent of the magnetic configuration has been already reported in both ASDEX Upgrade (L-mode) and W7-X electron-heated plasmas [18,19], which is mainly due to the lack of direct ion heating (ion heating through equipartition only) and the high levels of turbulent heat transport.…”

Evidence of vapor shielding effect on heat flux loaded on flowing liquid lithium limiter in EAST

“…Currently, most liquid metal research is focused on lithium (Li) [4,6,7], tin (Sn) [8,9], and Li-Sn [10]. Investigations with liquid Li were performed in many tokamaks, such as T-10M [6], T-11M [3], T-15 [11], FTU [12], EAST [13][14][15][16] and on linear plasma sources [4].…”

“…Currently, most liquid metal research is focused on lithium (Li) [4,6,7], tin (Sn) [8,9], and Li-Sn [10]. Investigations with liquid Li were performed in many tokamaks, such as T-10M [6], T-11M [3], T-15 [11], FTU [12], EAST [13][14][15][16] and on linear plasma sources [4]. The effect of liquid metal vapour shielding on the reduction of the plasma heat load to the liquid metal target was investigated in the laboratory.…”