5.3 Formation of Deposited Layers Made of Eroded Materials
87
(a)
(c)
(a) (b) (c) (d)
(a) DV-b
(b) DM-a:
(c) DM-c
(d) DV-d
(d)
(b)
1
10
100
0
5
10
15
20
25
PSL intensity [arb unit]
PSL intensity [arb unit]
Distance from front [mm]
e-folding length: 3mm
1
10
100
0
5
10
15
20
25
PSL intensity [arb unit]
Distance from front [mm]
e-folding length: 3mm
1
10
100
PSL intensity [arb unit]
e-folding length: 3mm
1
10
100
PSL intensity [arb unit]
e-folding length: 3mm
Fig. 5.12 Photo images and T profiles of toroidal sides of divertor tiles of JT-60U. Thickness
profiles along lines from the entrance to the bottom of the gap show the same exponential decay of
3 mm caused by prompt deposition of C eroded at the front surface
bottom could be higher than that at the entrance. Since chemical sputtering of C by
H has no threshold energy, higher hydrogen pressure could re-erode once deposited
C. Accordingly, the bottom of the narrow gap tended to be eroded and the wider gap
deposited corresponding to possible higher pressure in the latter. It should also be
noted that deposition appeared even behind the tile, i.e. at the interspace between the
tile backside and SS base, which were too narrow for escaping re-erode hydrocarbons.
Thus, deposition profiles in the shadowed area and remote area are quite dependent
on geometries of the areas so that it is hard to describe the general picture of carbon
transport (erosion and deposition) in tokamaks.
In the remote area, the line-of-sight deposition was clearly observed behind the
divertor in JT-60U as shown in Fig. 5.15 in which photographs of materials probes
are set at the respective location behind the W-shaped divertor and exposed to plasma
[15]. Only the probes of ➀–➃ which were set at the line of sight from the plasma
show C deposition and the others remained shiny. Thus, C deposition at the remote
area is limited to those areas on the line of sight from the plasma and their further
transport is prohibited because of no or very thin plasma there. Although JT-60U was
operated with PFM around 420 K, the temperature of non-plasma-facing surfaces was
87
(a)
(c)
(a) (b) (c) (d)
(a) DV-b
(b) DM-a:
(c) DM-c
(d) DV-d
(d)
(b)
1
10
100
0
5
10
15
20
25
PSL intensity [arb unit]
PSL intensity [arb unit]
Distance from front [mm]
e-folding length: 3mm
1
10
100
0
5
10
15
20
25
PSL intensity [arb unit]
Distance from front [mm]
e-folding length: 3mm
1
10
100
PSL intensity [arb unit]
e-folding length: 3mm
1
10
100
PSL intensity [arb unit]
e-folding length: 3mm
Fig. 5.12 Photo images and T profiles of toroidal sides of divertor tiles of JT-60U. Thickness
profiles along lines from the entrance to the bottom of the gap show the same exponential decay of
3 mm caused by prompt deposition of C eroded at the front surface
bottom could be higher than that at the entrance. Since chemical sputtering of C by
H has no threshold energy, higher hydrogen pressure could re-erode once deposited
C. Accordingly, the bottom of the narrow gap tended to be eroded and the wider gap
deposited corresponding to possible higher pressure in the latter. It should also be
noted that deposition appeared even behind the tile, i.e. at the interspace between the
tile backside and SS base, which were too narrow for escaping re-erode hydrocarbons.
Thus, deposition profiles in the shadowed area and remote area are quite dependent
on geometries of the areas so that it is hard to describe the general picture of carbon
transport (erosion and deposition) in tokamaks.
In the remote area, the line-of-sight deposition was clearly observed behind the
divertor in JT-60U as shown in Fig. 5.15 in which photographs of materials probes
are set at the respective location behind the W-shaped divertor and exposed to plasma
[15]. Only the probes of ➀–➃ which were set at the line of sight from the plasma
show C deposition and the others remained shiny. Thus, C deposition at the remote
area is limited to those areas on the line of sight from the plasma and their further
transport is prohibited because of no or very thin plasma there. Although JT-60U was
operated with PFM around 420 K, the temperature of non-plasma-facing surfaces was