"Deuterium Retention and Plasma Characterization"
Event details
| Date | 03.06.2013 |
| Hour | 10:30 › 11:30 |
| Speaker | Yangyang Zhang - University of Gent, B |
| Location |
CRPP, PPB 019
|
| Category | Conferences - Seminars |
Deuterium-Tritium reaction has the biggest reaction cross section among other fusion reactions. This scenario requires fuel control to be 50% D and 50% T. Retention, however, could break this fuel ratio balance and cause big problem to fuel control system. During tokamak operation, deuterium and tritium could go into first wall materials (mainly divertor region), leading to fuel loss and also the fuel inside of the first wall material could go into main plasma, causing additional fuelling. What more, for safety reason, the tritium inventory in ITER is strictly limited to 700g.
Here presented the deuterium retention study on Plasmatron VISIONI in SCK·CEN, Mol, Belgium. Deuterium (also mixture of nitrogen) plasma is generated through glow discharge, with typical parameters of Te=10eV, f=100V. The tungsten sample is used as the function of plan probe, which is connected to power source of -80V. The typical ion flux is f=1021 ion m-2s-1 and probe temperature is Tp=350˚C. Plasma is in non-thermal state and the ion energy is dominated by Bohms criterian, which is 1/2miv22=eDf+1/2Tee. SEM shows bubbles formed during pure deuterium exposure on the surface of tungsten samples. 5% nitrogen exposure also shows bubbles formed. 1% nitrogen exposure, however, shows a clear decrease of bubbles. The reason may be the relative high sample temperature Tp=350˚C (5% nitrogen exposure has a temperature drop in the end of the exposure despite of the same Tp with 1% exposure). XPS results shows high probe temperature (Tp=350˚C) could prevent tungsten-nitrogen chemical reaction. W-N chemical bunding appears at probe temperature around 250˚C. TDS is undergoing and the result will be included.
Here presented the deuterium retention study on Plasmatron VISIONI in SCK·CEN, Mol, Belgium. Deuterium (also mixture of nitrogen) plasma is generated through glow discharge, with typical parameters of Te=10eV, f=100V. The tungsten sample is used as the function of plan probe, which is connected to power source of -80V. The typical ion flux is f=1021 ion m-2s-1 and probe temperature is Tp=350˚C. Plasma is in non-thermal state and the ion energy is dominated by Bohms criterian, which is 1/2miv22=eDf+1/2Tee. SEM shows bubbles formed during pure deuterium exposure on the surface of tungsten samples. 5% nitrogen exposure also shows bubbles formed. 1% nitrogen exposure, however, shows a clear decrease of bubbles. The reason may be the relative high sample temperature Tp=350˚C (5% nitrogen exposure has a temperature drop in the end of the exposure despite of the same Tp with 1% exposure). XPS results shows high probe temperature (Tp=350˚C) could prevent tungsten-nitrogen chemical reaction. W-N chemical bunding appears at probe temperature around 250˚C. TDS is undergoing and the result will be included.
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