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K.Hanada1), N.Yoshida1), T.Honda2), A.Kuzmin1), H.Zushi1), I.Takagi3), T.Shibata4), A.Hatayama4), A.Fujisawa1), K.Nakamura1), H.Idei1), Y.Nagashima1), M.Hasegawa1), T.Onchi1), A.Higashijima1), S.Kawasaki1), H.Nakashima1), O. Watanabe1), O.Mitarai5), A.Fukuyama3), A.Ejiri6), and Y.Takase6)
1) Advanced Fusion Research Center, RIAM, Kyushu Univ., Japan.: 2) Interdisciplinary Graduate School of Engineering Sciences, Kyushu Univ., Japan.:
3) Graduate School of Engineering, Kyoto Univ.: 4) Keio Univ.: 5) School of Industrial Engineering, Tokai Univ.: 6) Graduate School of Frontier Science,
University of Tokyo.
Dynamic retention characteristics in RF driven long duration discharges on QUEST
Presented by K.HanadaRIAM
Kyushu University
What is dynamic retention?
Absor pt ion
Plasm a Induc ed-desor pt ion
Ref lec t ion
Di f fus ion
Desor pt ion
Plasm alayer
Bulklayer
Neut ra l Plasm a
TrappingDet rapping
Per m eat ion
Elementary step Image of diffusion-trap
Hydrogen isotope trapping in trap sites is likely to be long-tern retention and the other is desorbed via dynamic retention process during discharges. It is important to understand fuel circulation.
Permeation
SUS substrateDeposition layer
Trap site
Diffusion
Recombination
Potential
Distance
Desorption
( )( )
exp
exp
D B W
R B W
D E k T
k E k T
� −
� −
Dynamic retention can be monitored by outgassing just after plasma terminationA simple particle balance equation
When a dynamic retention plays a dominant role in fuel circulation, almost of injected fuel hydrogen will release just after plasma termination (~several hundreds second). Ratio between released and injected fuel hydrogen is a good index of how dynamic retention is dominantly working.
inΓnSN
inWΓin
WrΓoutWΓ
p pN τn iN τ
2
(1 )
in n W
in outW W W
in PW CX
P
outW W
nP P
P i
SN
r
N
kC
NdN N
dt
τ
τ τ
Γ = + Γ
Γ = − Γ − Γ
Γ = + Γ
Γ =
= − +
2
outn W
outW W
SN
kC
= Γ
Γ =
Par t ic leDeposi t ion, NW
Plasma particle, Np
NeutralParticle, Nn
Fueling, ΓinPumping, Sp
Ther m al desor p t ion, τW
Plasm a-induc eddesor pt ion, C1
Ref lec t ion , R
Par t ic le load , τp
Ion izat ion, τion
[nm]1000
0
1000
0
[nm
]
[nm]33.0
[nm]1000
0
1000
0
[nm
]
[nm]33.0
AFM
400 600 800 1000
1015
1016
1017
1018
Desorption Rate(/m2s)
Tem perature(K)
SUS316L unexposef SUS316L weak coloring SUS316L heavy coloring W 2012 S/S W-Equ
Particle fluxParticle Energy
Fuel recyclingRecombinationDefect density
Dynamic retention is working in fuel hydrogen circuit including core plasma
Dynamic retention is dominantly working during discharges on metal-dominant wall.
JET carbon wall JET ILW
Long-tern retention strongly depends on plasma-facing materials. Carbon is likely to retain hydrogen isotope chemically and difficult to release in low wall temperature such as 673K. While metal is easy to release it and dynamic retention is dominant in fuel circulation.
T. Loarer et al, Nucl. Fusion 47 (2007) 1112–1120
V. Philipps et al, J. Nucl. Matr. 438 (2013) S1067–1071
Most of stored fuel is desorbed during several tens seconds after the end of the
discharge.7
6
5
4
3
2
1
0
Stored H (x1020
)
76543210
Injected H (x1020
)
180 sec
Limiter IBnull ECR gas
300 sec
90 sec
T. Loarer et al, Nucl. Fusion 47 (2007) 1112–1120
QUEST ASDEX-U
These phenomena are common in devices with dynamic retention dominant wall.
CS
W blocks
Maintenance hole
Bt 0.25 T at R=0.64 m (CW)PF 4 pairsCS 3 coilsRF systems 2.45GHz 50 kW(CW) 8.2 GHz 400 kW(CW)
VQUEST~12.8 m3SQUEST~26.5 m2Spump~2.7 m3/s
W-PFCs (~ 30 %) in QUEST
Situation of QUEST PFCs until 2014SS
Since 2014 A/W, the hot wall made of W-plasma spray is installed to control wall temperature during discharges.
We successfully obtain long duration discharges with good repr
oducibility.50
40
30
20
10
0
TFC (kA)
4
3
2
1
0
PFC (kA)
3
0
ASDEX G
10
5
0
ASDEX_gauge01_V_ ASDEX_gauge02_V_ ASDEX_torr_ IG1_torr_ DiffPressure_V_ HighSpeedIG_V_
-20-10
01020
Ip_HE (kA)
543210
ne17 (m-3)
Ip_Hall_kA_ density_10^17_m-2_
1000
500-150
0
150 R_hall_mm_HE_ Z_hall_mm_HE
50
0
PC (kW)
1086420
PH (kW)
RFnet_kW_PC RFPH_INJ_kW_
0.25
0.006005004003002001000
Time (sec)
0.04
0.02
0.00
P250_2_V_ AXUV_V_
#27394-0 0 - 620 sec
TFC_kA_ PF17_kA_ PF26_kA_ PF35_1_kA_ PF35_2_kA_ PF4_kA_ MPP_CUR_SIG_kA_
50
40
30
20
10
0
TFC (kA)
4
3
2
1
0PFC (kA)
3
0ASDEX G
10
5
0
ASDEX_gauge01_V_ ASDEX_gauge02_V_ ASDEX_torr_ IG1_torr_ DiffPressure_V_ HighSpeedIG_V_
-20
0
20Ip_HE (kA)
543210
ne17 (m-3)
Ip_Hall_kA_ density_10^17_m-2_
1000
500-150
0
150 R_hall_mm_HE_ Z_hall_mm_HE
50
0
PC (kW)
1086420
PH (kW)
RFnet_kW_PC RFPH_INJ_kW_
0.25
0.006004002000
Time (sec)
0.040.020.00
P250_2_V_ AXUV_V_
#27395-0 0 - 750 sec
TFC_kA_ PF17_kA_ PF26_kA_ PF35_1_kA_ PF35_2_kA_ PF4_kA_ MPP_CUR_SIG_kA_
50
40
30
20
10
0
TFC (kA)
4
3
2
1
0
PFC (kA)
3
0
ASDEX G
10
5
0
ASDEX_gauge01_V_ ASDEX_gauge02_V_ ASDEX_torr_ IG1_torr_ DiffPressure_V_ HighSpeedIG_V_
-20
0
20
Ip_HE (kA)
543210
ne17 (m-3)
Ip_Hall_kA_ density_10^17_m-2_
1000
5000
R_hall_mm_HE_ Z_hall_mm_HE
50
0
PC (kW)
1086420
PH (kW)
RFnet_kW_PC RFPH_INJ_kW_
0.25
0.0010008006004002000
Time (sec)
0.04
0.02
0.00
P250_2_V_ AXUV_V_
#27396-0 0 - 1000 sec
TFC_kA_ PF17_kA_ PF26_kA_ PF35_1_kA_ PF35_2_kA_ PF4_kA_ MPP_CUR_SIG_kA_
#2739410min
#2739512min
#2739613min30s
• Hα signal level was feed-back controlled by regulation of gas fuelling and injected power was kept constant. Consequently plasma current and density could keep a certain level.
• Neutral pressure in rear side of divertor plate was gradually increasing and other signals seem not to change so much.
10
Heat load can be removed in SSO on QUEST
Rf power=40 kW
Particle recycling
Heat load on PFCs
3 min in IBN@ 40 kW with cooling the limiters and for 107 s @ 100 kW in SN-Lim. These were demonstrated without using recycling FB control.
Divertor Limiter
PFC Temp. is constant
Dynamic retention is dominant in QUEST exp. and required fuelling rate is gradually decreasing with plasma dura
tion.Inject H2
Evacuate H2
• 70% of injected hydrogen was retained in plasma facing wall just before the termination of the discharge and required fuelling rate is gradually decreasing and finally no fueling before the plasma termination (several 100 s) was observed.
• Outgassing just after plasma termination (~600s) indicates that dynamic retention is dominant.
(wall inventory)
Wall Saturation
Wall saturation was observed in higher wall temperature and was not decided by the number of wall retained hydr
ogen.
• Wall inventory is estimated by the difference between injected and evacuated hydrogen.
• A wall saturation was observed in only TW=373 K and lower TW could provide the higher number of wall retained hydrogen.
Wall temp. dependence of supplied hydrogen to keep the same Hα signal level.
Ha level:0.15
• Wall temp. has a significant impact in wall pumping rate.
• This clearly shows the property of dynamic retention is strongly affected by the wall temperature.
The Hα level has an impact to time-evolution of wall storing H.
Lower Hα level is likely to provide faster wall-saturation.
Many microscopic observations can support the model validation.2012AW-P16-WEMo(RC)
20nm
Substrate(Mo)
Deposition1
32
0.0 0.2 0.4 0.6 0.8 1.0
0.1
1
10
100
Intensity
Sputtering Tim e (s)
Fe Cr Ni C O W H M o Cu Si
2012AW
C
Fe Mo
Ni
CrO
W
Si
HCu
13 2
TEM Collaborated with Prof. Yoshida
Collaborated with Prof. Ohya
4x1020
3
2
1
0
Stored D (D/m2 )
300250200150100500
Time (min)
450
400
350
300
holder temperature (K)
Plasma irradiation
GD-OES
NRACollaborated with Prof. Takagi
1x1018
0
Desorption rate (m-2
s-1)
600550500450400350300
Temperature(K)
D2 Gauss Fitting peak_target Calculation
D2 ion implantation & TDS
QUEST wall model based on a simple diffusion-trap model.
Absor pt ion
Plasm a Induc ed-desor pt ion
Ref lec t ion
Di f fus ion
Desor pt ion
Plasm alayer
Bulklayer
Neut ra l Plasm a
TrappingDet rapping
Per m eat ion
To be published JNM.
( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )( ) ( ) ( ) ( ) ( )( ) ( ) ( ) ( ) ( )
( ) ( )
( )
( )max
2
2
0
0
, , , ,, , , , ,
,, , , ,
,, , , ,
,0,
,0
,
W W TA TBA TA B TB
TAA W A A TA
TBB W B B TB
WW
x
W
x x
C x t C x t C x t C x tD G x t k C x t G x t k C x t G x t
t x t tC x t
C x t F x t k C x t G x tt
C x tC x t F x t k C x t G x t
t
C x tkC t
x
C x t
x
G x t G e
β
β
=
=
−
� � � ��= + − − − −� � � � ��
��= −� ��
� �= −� ��
� �=� ��
��� =� ��
= ( ) 2 2
00
0
00
0
( , )1 ( , )
( , )
0 ( , )
( , )1 ( , )
( , )
0 ( , )
D Wx x x
TATA TA
TAA
TA TA
TBTB TB
TBB
TB TB
C x tC x t C
CF x t
C x t C
C x tC x t C
CF x t
C x t C
−
� − <�= �� ��� − <�= �� ��
QUEST wall model• All the model parameters except thickness of r
e-deposition layer are decided by D2+ ion implantation and TDS.
• Ion deposition profile is calculated by TRIM code using GD-OES component measurement.
• Recombination coefficient may be confirmed by the NRA experiment.
• Thickness of re-deposition layer will be decided with the colorimetric technique.
Need many measurements with microscopic observation.
It is difficult to apply plasma experiments in various devices.
To simplify the model, we assume
We try to propose a simple model to apply many of wall behaviors in various devices.
To confirm applicability of the model, we execute
Hα signal is roughly proportional to ionization rate in the wide range of Te and ne.
19
nH~1016m-3, nH2=1017m-3
Red line 10eV
Green line 50eV
ne dependence Te dependence
• Hα signal is a good index for monitoring ionization rate in the wide range of ne (1x1017-1019) and Te (5-50eV).
• Hα level control with a feedback manner could provide controlled ionization flux during long duration discharges.
Provided by Dr. Shibata in Keio Univ.
• In the CR model calculation, production rate of CX neutral is also proportional to intensity of Hα signal. This indicates that in-flux to the wall can be controlled by Hα level.
• The CX rate is approximately half of the ionization rate and plays important role in fuel circulation.
1. Hydrogen ions losing from the core plasma
2. Neutral Hydrogen atoms produced by CXIn steady state condition,
Ionization rate = loss rate of plasma ions
Te=50eV
Ionization rate = Wall injected ion rate
IHα
The control of Hα signal in the QUEST plasmas gives constant in-flux to the plasma faci
ng wall.
inWΓ
nP P
P i
NdN N
dt τ τ= − +
Hα feedback level dependence of NW
Time-derivative NW
IHα[a.u.]
Wall temperature dependence can be reconstructed by the simple model with different k.
1.4x1021
1.2
1.0
0.8
0.6
0.4
0.2
0.0Wall-Stored H
600sec4002000Time (sec)
#27395@373K #26906@300K
1.0x1021
0.8
0.6
0.4
0.2
0.0
Injected H2
6004002000
Time (sec)
SN27395@373K SN26906@300K
Wall stored fuel
Evacuated fuel
Effect of trapping
• The same k is well-fitting.
• The estimated Γin are reasonable in the fitting.
• In the range of higher NW, effect of trapping appears.
k=1.6x10-23 Γin
The experimental data with various Γin can directly derive the simple model.
The effect of trapping reconstructs asymptotical behavior to wall-saturation
kt:Rate of trappingNtmax:The number of trap siteNt = The number of trapping hydrgenIt should be noted that de-
trapping does not take into consideration.
Red:kt=0.001Blue:kt=0.002Htmax=2x1021
Nw+Ntd(
Nw
+N
t)/d
tWall-saturation
The estimated time constant in various devices.
• We assume the same value of recombination coeffcient, k0=1.6x10-37m4/s.
Device QUEST JET ITER DEMO
Thickness 0.1µm 1µm 10µm 100µm
Flux(m-2s-1)
3x1017 1x1020 1x1021 1x1021
Time(s) 150 250 800 8000
We have to measure the thickness of deposition layer and the recombination rate.
Summary
• Hydrogen (H) recycling and wall pumping properties during long duration discharges on a dynamic retention dominant wall are investigated on QUEST
• The H storing capability in the plasma-facing wall has a significant relation to intensity of Hα radiation and wall temperature experimentally, and is reconstructed well by a simple balance equation based on a surface-recombination limiting model applied to a re-deposition layer.
• A typical time constant representing wall saturation on dynamic retention dominant wall is provided by the balance equation, and is significantly longer than all the other global time constants such as energy confinement time and current diffusion time.
Plasma driven permeation probeMembrane= PdCuThickness = 20 micronTemp = 573K
Direct measurement of Retention flux Gas puff at every 40sec
GDP at 2Pa => Ku,Kd,DNumerical fitting NRA+PDP =>Ku,Kd
Where, K recombination coeff., D diffusion coef.
A.Kuzumin in this meeting
x
H2
),(),(
),0(),0(
2
2
0
2
2
tlxCKtlx
tCKx
CDtx
x
CD
t
C
Hrdpdp
Hrux
inc
HH
H
===Γ
+∂
∂−==Γ
∂∂=
∂∂
=
Global particle balance
A.Kuzumin in this meeting
Equations for particle balance expression
( ) ( )
( )
( ) ( )
( )
(1 ) 1 (1 ) 1
1 (1 ) 1
1 1
1
W W nW in out in g in out rec
ng rec
in
W Wout out
rec Win n
W nout rec
n n n
ion cx
NR r r R
NR r R
Rr r N
Nr R
N N N
τ
τ
τ
τ
τ τ τ
Γ = Γ − Γ = Γ − = − Γ − Γ = − −
− = − −Γ
Γ Γ= =− Γ −
Γ = −
= +
Can microscopic observations predict fuel circulation in plasma devises?
100nm
depo
t=70nm
100nm
depo
t=8nmCollaborated with Prof. Yoshida
Heavily colored region
Slightly colored region
SUS316L plate for fixing of
magnetic probe
400 600 800 1000
1015
1016
1017
1018
Desorption Rate(/m2s)
Tem perature(K)
SUS316L unexposef SUS316L weak coloring SUS316L heavy coloring W 2012 S/S W-Equ
============= ( ==== )== : ======= Hα ======== ( ======== )
============= ( ==== )========= : =====
31
• Hα ================================• =================================• =================== .
=======================0.175:4x1018H/s,0.2:5.2x1018,0.25:7.6x1018k=1.6x10-23
Image of a diffusion and trap model
Move fast
SUS substrateDeposition layer
Trap site
Diffusion
Recombination
Potential
Distance
Deposition profile was decided by TRIM calculation based on TEM & GD-OES measurement
2012AW-P16-WEMo(RC)
20nm
Substrate(Mo)
Deposition1
32
0.0 0.2 0.4 0.6 0.8 1.0
0.1
1
10
100
Intensity
Sputtering Tim e (s)
Fe Cr Ni C O W H M o Cu Si
2012AW
C
Fe Mo
Ni
CrO
W
Si
HCu
13 2
TRIM CalculationTEM & GD-OES
500eV D
0 20 40 60 80 100
0
1x105
2x105
3x105
4x105
5x105
0.5keV-D 1.0keV-D 2.0keV-D
D Ions
Depth (nm)
Distribution of Injected D in Deposition of QUEST
Material: 31C-19O-33Fe-17W
( ) ( ) 2 2
0, D Wx x xG x t G e− −=
Hydrogen recycling can be reconstructed in long duration plasma on QUEST
5x1020
0
NH
2
1
0
Rg
2010
0
Ip (kA)
4003002001000Time (sec)
1
0H
α (a.u.)(b)
#24693 (a)
1.0
0.8
0.6
0.4
0.2
0.0
Rrec
300250200150100500
Time (sec)
1.0
0.8
0.6
0.4
Rrec
(#24693)20nm 50nm
100nm
8x1019
6
4
2
0
Stored H (H/m2 )
300250200150100500Time (sec)
1x1018
D/m2
5x1017
D/m2
2x1017
D/m2
1x1017
D/m2
JNM K.Hanada, et al. 2015
Global particle balance
Wall Stored H X 0.5
TMP, =======(Spump=2.7m3/s)
===== = ======== + ==========
======
Γfuel: ======= Γab: ======Γpump: ====== Γrec: =======Γwall ======= ref: ===
Simplified QUEST-wall model can reconstruct the particle flux depen
dence.
Simplified QUEST wall model
100 nm
80 nm
100 nm
100 nm
100 nm
80 nm
SOL plays an essential role in ionization. SOL model decides ionization rate from molecules a
nd atoms
1012
1014
1016
1018
1020
Number of Particles
0.60.40.20.0
Time[ms]
ne
nH
nH*
nH**
nH+
nH2
nH2+
nH3+
( )
2
2 2
2
2
2
20
20
1
2
1 11
2 2
1 1
2
p pHI H p
p
pHHI H p MH H p
p
H H pwW MH H p W in out
ab w p
Hp pw wW W
p ab w p
H Molecule
N NN N
t
NNN N N N r
t
N N NNkN N N CN
t N
NN NN NkN r CN
t N
N N
γτ
γ γτ
γτ τ
τ τ τ
�= − +
�
� = − + +�
� � �= − − − + + Γ − Γ� �� � �
� �� = − + − + − −� �� � �=
Hα ===================
38
=======
Ip ===
0.25 ============== CX =====================
Te:10eV
Te:50eV
Cross-section of the considering reactions for the CR model calculatio
n
39
The data file HYDHEL“Elementary Processes in Hydrogen-Helium Plasmas”
A calculated result with the CR model
tp=0.05sec,H2 ==== 3 = 1018 ========== 5 = 10-5
CR ======= (0~0.002sec) CR ======= (0~1sec)
Typical properties of particle balances in long duraion discharge
s
IAEA P?-?? A. Kuzmin, et al
===============
Sub Box
• ================================================• ======================= Sub Box ==========================
inΓnSN
inWΓin
WrΓoutWΓ
p pN τn iN τ
inΓnSN
inWΓin
WrΓoutWΓ
p pN τn iN τ
outsub WΓ
Image of a diffusion and trap model
Permeation
SUS substrateDeposition layer
Trap site
Diffusion
Recombination
Potential
Distance
Desorption
Long-tern retention has an impact to fuel circulation in JET-class plasmas.
T. Loarer et al, Nucl. Fusion 47 (2007) 1112–1120
Many parameters make a complicated connection and lead to difficulties to promote international collaboration.
Fuel retention seems to depend on heating power, wall temperature, wall material and so on.
T. Loarer et al, Nucl. Fusion 47 (2007) 1112–1120
S. Brezinsek et al = Nucl. Fusion 53 (2013) 083023
Calorimetric measurement was applied to investigate heat load distribution in various magnetic configuration
60
50
40
30
20
10
0
Power fraction (%)
Limiter IBnull Divertor
InnerLimiter
Divertor MovableLimiter
Vessel
Summary of heat load distribution on various magnetic configuration. Inner limiters locate on center stuck, and divertor limiters on divertor plates, and a movable limiter locates on outer vessel.
Measured Parameters:IP: -108499.797IPF17: 1077.304IPF26: 1241.405IPF35: -6.7895IPF42AB: -600.9293IextraPF: 0IHCUL: -1.3646
Fitted Parameters:IP: -108500.094IPF17: 1077.3015IPF26: 1241.3992IPF35: -6.7894IPF42AB: -600.9293IextraPF: 0IHCUL: -1.3646
CurR: 0.76CurZ: 1.04e-004MagR: 0.81MagZ: 1.05e-004
Fitted Parameters:β
p:0.41558β
t:2.9955li:1.011q95:4.811δ
up: 0.20597δ
down: 0.20597
κ: 1.0582Estor: 3736.2507JIP- : -108500.1 A
IP+: 0 A
R/m
Z/m
JRZ
shot:10760 Time: 1440ms
0.2 0.4 0.6 0.8 1 1.2 1.4-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Hot wall is a control knob of fuel circulation.
47
Hot wall
Heater
Cooling panel
RadiationShield
Vacuum Vessel
ThermalIsolator
Some cooling channels will be installed on the vessel
Present Status of the hot wall. The hot wall is ready to operate.
Hot wall is expected to control H recycling during plasma dischar
ges. 1.0
0.8
0.6
0.4
0.2
0.0
Rrec
10008006004002000Time (sec)
373K
300K
373K 300K
Wall stored H Recycling ratio20x10
19
15
10
5
0
Stored H
10008006004002000Time (sec)
Summary
• Many of microscopic observations is well-collaborated in the QUEST wall model.
• Global wall behavior such as flux and wall temperature dependences can be expressed by QUEST wall model.
• Capability of the hot wall can be demonstrated by the QUEST wall model.
• International cooperated activities can support to obtain basic physical parameters and plasma induced phenomena such as co-deposition and defect production.
• For Integrated control to aim at SSO, SOL and plasma models should be established.
CS
W blocks
Maintenance hole
Bt 0.25 T at R=0.64 m (CW)PF 4 pairsCS 3 coilsRF systems 2.45GHz 50 kW(CW) 8.2 GHz 400 kW(CW)
VQUEST~12.8 m3SQUEST~26.5 m2Spump~2.7 m3/s
W-PFCs (~ 30 %) in QUEST
Present situation of QUEST PFCs
A model is proposed to handle what happened in the system.
( )
2
2 2
2
2
2
20
20
1
2
1 11
2 2
1 1
2
p pHI H p
p
pHHI H p MH H p
p
H H pwW MH H p W in out
ab w p
Hp pw wW W
p ab w p
H Molecule
N NN N
t
NNN N N N r
t
N N NNkN N N CN
t N
NN NN NkN r CN
t N
N N
γτ
γ γτ
γτ τ
τ τ τ
∂= − +
∂
∂ = − + +∂
∂ = − − − + + Γ − Γ ∂
∂ = − + − + − − ∂ =
8
6
4
2
0
n e (10
17m
-2)
403020100Time (sec)
460 sec
60sec
220sec
30
25
20
15
10
5
0Enhancement factor
50403020100Integrated Hα
#24692 50kW 5ms puff #24726 90kW 15ms puff #24727 90kW 10ms puff
=========
54
===== (I.Takagi et al, Journal of Nuclear Materials 417(2011)564-567)