14 Oct. 2009, S. Masuzaki 1/18 Edge Heat Transport in the Helical Divertor Configuration in LHD S....
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![Page 1: 14 Oct. 2009, S. Masuzaki 1/18 Edge Heat Transport in the Helical Divertor Configuration in LHD S. Masuzaki, M. Kobayashi, T. Murase, T. Morisaki, N. Ohyabu,](https://reader035.fdocuments.us/reader035/viewer/2022081603/56649f215503460f94c397f8/html5/thumbnails/1.jpg)
14 Oct. 2009, S. Masuzaki1/18
Edge Heat Transport in the Helical Divertor Configuration
in LHD
S. Masuzaki, M. Kobayashi, T. Murase, T. Morisaki, N. Ohyabu, H. Yamada, A. Komori and LHD Experiment group
National Institute for Fusion Science
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14 Oct. 2009, S. Masuzaki2/18
MOTIVATION
• Understanding of heat and particle transport in edge region is essential for divertor design in fusion reactor.
– Complex field line structure in which stochastic region, islands and laminar region coexist exists in edge region in heliotron-type devices, stellarators and tokamaks with RMP.
– Different mechanism which determines divertor heat and particle flux profiles from poloidal divertor tokamaks may exist.
• In this study, we focus on profiles of heat and particle flux on helical divertor in LHD heliotron.
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14 Oct. 2009, S. Masuzaki3/18
OUTLINE
• Edge magnetic field line structure in LHD
• Relation between the structure and profiles of particle and heat load on divertor
• Transport change with Te rise
• Summary
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14 Oct. 2009, S. Masuzaki4/18
Edge field line structure in LHD
R R R
R
= 0º = 9º = 18º
Rax=3.6m
Rax=3.75m
•Helical divertor SOL has three dimensional structure.
•In the HD SOL, the stochastic region, islands and laminar layer co-exist.
•The fine structure in the HD SOL varies with the operational magnetic structure.
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14 Oct. 2009, S. Masuzaki5/18
Edge field line structure in LHD
R
R
= 0º
Rax=3.6m
Rax=3.75m
1
10
102
103
Lc,
Lk
(m)
1
10
102
103
2.6 2.8 3
Lc,
Lk
(m)
R (m)4.6 4.8 5
R (m)
L c (m
)L c
(m)
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14 Oct. 2009, S. Masuzaki6/18
Divertor leg
‚h‚
b‚q‚
eƒAƒ
“ƒeƒ
i
i• W €” z Ê C‚ q‚ ‚ ‚ R D‚ V‚ T‚ Cƒ À‚ O D‚ R‚ Q“j
i• W €” z Ê C‚ q‚ ‚ ‚ R D‚ V‚ T‚ Cƒ À‚ O“j
100
101
102
103
0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
L c (m
)
X (m)
100
101
102
103
104
L c (m
)
Torus center
- trace CW- trace CCW
Z
Rax=3.5m
Rax=3.6m
Outer of this line, field lines interrupted by divertor plates or first wall within about ten meter
divertor leg
Z (m)
0.4
0.6
0.8
1
1.2
1.4
0.8 0.9 1 1.1 1.2 1.3 1.4
B (
T)
z(m)
BT
BP
Rax=3.9m
In divertor region, poloidal field component is larger than toroidal one
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14 Oct. 2009, S. Masuzaki7/18
Divertor Plate Array
Divertor plate arrays and diagnostics
O utboard Inboard
O utboard
Bottom
Top=0° 36° 72°
LP#1
LP#2LP#3LP#4
LP#5
• Langmuir probes and thermocouples are embedded in divertor plates
• An IR camera observes inboard divertor plates
• 1,700 water cooled graphite tiles
IR camera4.2℃
123.1℃
50
100
Divertor platesPrivat
e region
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14 Oct. 2009, S. Masuzaki8/18
Particle Flux Profiles on a Divetor Plate
101
102
103
104
0
0.01
0.02Rax3.75m
Lc (
m)
Iis
(A)
101
102
103
104
105
0
0.01
0.02
0 20 40 60 80 100 120
Rax3.9m
Lc (
m)
Iis
(A)
probe position (mm)
101
102
103
104
0
0.01
0.02Rax3.5m
Lc (
m)
Iis
(A)
101
102
103
104
0
0.01Rax3.53m
Lc (
m)
Iis
(A)
101
102
103
104
0
0.04
0.08
0 20 40 60 80 100 120
Rax3.6m
Lc (
m)
Iis
(A)
probe position (mm)
=0° 36° 72°
Outboard
InboardOutboard
Bottom
Top
Divertor plate array
Probe array
Inward shifted RaxOutward shifted Rax
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14 Oct. 2009, S. Masuzaki9/18
Heat Flux Profiles on a Divertor Plate
• Heat flux profiles were reconstructed by using temperature rise profiles at the beginning of NB injection. Semi-infinite assumption was applied neglecting three dimensional heat diffusion.
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14 Oct. 2009, S. Masuzaki10/18
Heat and Particle Deposition Profiles on divertor
6040200
-150
-100
-50
0
50
100
150
Toroidal angle, (°)
Pol
oid
al a
ngle
,
(
。
)
Rax=3.75m
6040200
-150
-100
-50
0
50
100
150 Rax=3.6m
2520151050
red
blue
red
blue
Particle deposition patterns on the HD. (=0)(Calculation results of field lines tracing)
inboard
outboard
outboard
bottom
top
Par
ticle
num
ber
(cal
.)
Nor
mal
ized
tem
pera
ture
ris
e
0
50
100
150
0
1
2Rax=3.6m
0
50
100
150
0
1
2
0 10 20 30 40 50 60 70
Rax=3.75m
Toroidal angle (°)
Profile of normalized temperature rise measured by thermocouples, and particle deposition obtained by field line tracing.
=0° 36° 72°
Outboard
InboardOutboard
Top
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14 Oct. 2009, S. Masuzaki11/18
Change of heat flux profile during discharge (Rax=3.60m)
• Such change of heat flux profile has been observed frequently.• Particle flux profile is also changed.
t=1.2s
t=2.4s
Divertor plate arrays
First wall
0
6
12
101
102
103
104
020406080100120
Pdiv
(MW/m2) Lc (m)
(a)t=2.4-2.6s
t=1.1-1.3s
position (mm)
0
4
8
0
10
20
n e,b
ar (
101
9 m
-3)
PN
BI (
MW
)
(b)
0
200
400
0
1
2
0 1 2 3 4
Te
, L
CF
S (
eV)
n e,
LC
FS (
101
9 m
-3)
time (s)
(c)
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14 Oct. 2009, S. Masuzaki12/18
Application of the 3D edge transport codes : EMC3-EIRENE
Physics standard fluid equations of density, momentum, energy of ion & electron simplified fluid model for impurities (not for present analysis) kinetic model for neutral gas
Geometry
fully 3D for plasma, divertor plates, baffles and wall ergodic or non-ergodic B-field configurations
Numerics
Monte Carlo technique on local field-aligned vectors, piecewise parallel integration for isolation of the small from the large II-transport (/II~10-8) new Reversible Field Line Mapping (RFLM) technique, Finite flux tube coordinates for B-field line interpolation
Coupled self-consistently
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14 Oct. 2009, S. Masuzaki13/18
Reproduce of the profile change using EMC3-EIRENE code
• Blue profile in experiment was reproduced by calculation.• Red profile was not well reproduced. But increasing of diffusion
coefficient flatten the profile in calculation.• Heat load decreases with increase diffusion coefficient.
0
6
12
101
102
103
104
0 20 40 60 80 100 120
Pdiv
(MW/m2) Lc (m)
t=2.4-2.6s
t=1.1-1.3s
position (mm)
0
4
8
101
102
103
0 50 100 150
D=0.2 =0.6D=1, =3D=5, =15
Lc
Pdiv
(MW/m2) Lc(m)
position (mm)
6I
experiment calculation
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14 Oct. 2009, S. Masuzaki14/18
At 10.5U probe position
• Heat load (and particle load) increases with increase of diffusion coefficient at this position.
• Heat and particle transfer from “long” flux tube to laminar region is enhanced.
0
0.4
0.8
60 80 100 120 140
10.5UD=0.2, =0.6D=1, =3D=5, =15
Pdiv
(MW/m2)
position (mm)calculation
0
0.5
1
0
0.05
0.1
0 1 2 3 4
tota
l Isa
t 6I(
A)
tota
l Isa
t10.5
U(A
)
time (s)
• The ratio of total Isat at 10.5U probe to that at 6I probe increase during the profile change (yellow hatched).
• Consistent with calculation assuming larger D and .
experiment
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14 Oct. 2009, S. Masuzaki15/18
In the case of Rax=3.75m
• Profiles of heat and particle flux are not largely changed by plasma conditions.
• In experiment, ratio of peak heat flux on the divertor to heating power is large for relatively low Te discharges (blue line).
• In calculation, the ratio increase with decreasing of D and .
0
1
2
3
4
0 2 4 6 8 10 12
7Iis
Te
*sin
(
MW
/m2 )
PNBI
-Prad
(MW)
6.5e19m-3
213eV
5.6e19m-3
273eV
7.2e19m-3
203eV
2.8e19m-3
336eV
5.4e19m-3
323eV
3.3e19m-3
373eV2.7e19m-3
390eV2.9e19m-3
383eV
1.9e19m-3
406eV
0
1
2
3
0 20 40 60 80 100 120
7I is
Te*s
in
(M
W/m
2)
position (mm)
Divertor heat flux vs. heating powerNe and Te at LCFS are shown for each symbol
0
4
8
10
100
1000
0 50 100 150
D=0.2, =0.6D=1, =3D=5, =15
Lc(m)
Pdiv
(MW/m2) Lc(m)
position (mm)
6IExp.
Cal.
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14 Oct. 2009, S. Masuzaki16/18
Less collision looks to enhance the heat transfer from long flux tube to laminar region
• Normalized heat flux vs. collision mean free path (1016Te
2/ne) around the last closed flux surface.
• Decreasing of the normalized heat flux suggests that heat transfer from “long” flux tube to laminar region is enhanced.
0
0.2
0.4
0.6
0 20 40 60 80 100
7IisT
e*sin/(P
nbi-P
rad)
collision mean free path (m)
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14 Oct. 2009, S. Masuzaki17/18
Do diffusion coefficients increase with increasing of Te?
Te Isat@[email protected]
Te
Te flattening of heat flux profile@6I
Pdiv@6I
Heating power
Pdiv@6I
Heating powerCalculations with increasing D and
Observations in discharges with Rax=3.75m
Observations in discharges with Rax=3.60m
consistent
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14 Oct. 2009, S. Masuzaki18/18
Summary
• Profiles of heat and particle load on divertor plates are roughly determined by magnetic field line structure.
– Though the edge field line structure is complex, the profiles can be roughly predicted even in the complex e.
• Heat and particle transfer from “long” flux tube to laminar region look to be enhanced with Te rise rather than increasing collisionality.
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14 Oct. 2009, S. Masuzaki19/18
Closed Helical Divertor will be installed (2/10 sections) in 2010
Present divertor Closed divertor
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14 Oct. 2009, S. Masuzaki20/18
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14 Oct. 2009, S. Masuzaki21/18
Edge Te profiles D and were estimated by fitting of
calculation to experimental data
0
100
200
73141
Te (
eV
)
D = 0.125 m2/s0.25 m2/s0.5 m2/s1.0 m2/s
TS
0
100
200
73161
Te (
eV
)
D = 0.25 m2/s0.5 m2/s1.0 m2/s2.0 m2/s
0
100
200
4.5 4.6 4.7 4.8 4.9
73508
Te (
eV
)
R(m)
D = 0.25 m2/s0.5 m2/s1.0 m2/s
Te,LCFS~200eVne,LCFS~1-1.5E19m-3
D = 0.125 - 0.25 m2/s= 0.375 - 0.5 m2/s
Te,LCFS~400eVne,LCFS~1-1.5E19m-3
D = 0.5 – 1.0 m2/s= 1.5 – 3 m2/s
Te,LCFS~200eV
ne,LCFS~6E19m-3
D = 0.25 - 0.5 m2/s= 0.75 – 1.5 m2/s
These results suggest that the cross-field transport coefficients have temperature dependence, and they also depend on density weakly.