modelling of time dependent high q operational scenario for iter-like device
DESCRIPTION
MODELLING OF TIME DEPENDENT HIGH Q OPERATIONAL SCENARIO FOR ITER-LIKE DEVICE. 3 d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache. V. Leonov: Modelling of High-Q Scenario. RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE» NUCLEAR FUSION INSTITUTE. Motivation - PowerPoint PPT PresentationTRANSCRIPT
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MODELLING OF TIME DEPENDENT HIGH Q OPERATIONAL SCENARIO FOR
ITER-LIKE DEVICE.
V.M. Leonov
Nuclear Fusion Institute, RRC “Kurchatov Institute”, Moscow, Russia.
ITPA Confinement Database and Modelling Topical Group 3d Meeting, 21-23 October 2002, Cadarache, France.
2
Motivation
One of the ITER goals is “to explore the possibility of high-Q
operation if favourable confinement conditions can be achieved”.
High-Q operation is interesting for investigations of burning
stability, control of plasma parameters and burning conditions
by different feedback loops at the small Paux 0.
RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE»
NUCLEAR FUSION INSTITUTE
3d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache.
V. Leonov: Modelling of High-Q Scenario
3
Issues
Analysis of ITER operational diagrams show that for
high Q (Paux 0) operation it is desirable to have:
--- plasma current higher than 15MA (q<3) (MHD stability-?)
--- enhanced density (close to the Greenwald limit) (E (n) - ?)
--- enhanced confinement (RS regimes with ITB) (Paux = 0 -?).
The subject of this work is to investigate the possibility of
ITER operation in enhanced confinement regime with ITB
at Paux = 0 during the time ~ some hundreds sec ( >> E ).
(to test burning dynamics and possibility to control performance and plasma
parameters in regimes with Paux= 0 ).
RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE»
NUCLEAR FUSION INSTITUTE
3d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache.
V. Leonov: Modelling of High-Q Scenario
4
Simulations show that RS configuration can’t be achieved
by bootstrap current only and some auxiliary off-axis CD (or Paux)
is necessary. It does difficult to achieve high Q values
but ...
... the main idea:
To use very long skin time (~ 3000s) which >> E (~ some s).
If the RS configuration is once achieved on the initial stage of the
discharge the operation in this configuration with the enhanced
confinement can be then continued for some hundred sec during
j(r) profile reorganization at Paux = 0.
RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE»
NUCLEAR FUSION INSTITUTE
3d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache.
V. Leonov: Modelling of High-Q Scenario
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-0,2
0,0
0,2
0,4
0,6
0
100
200
300
0
5
10
15
0
2
4
6
8
10
Ulo
op (
V)
Uloop
Ip
I p (M
A)
Paux
Pfus
P fus (
MW
)
020406080100
P aux (
MW
)
<Te>
<n e>
<Ti>
<T>
(keV
)
02468101214
<n
e> (
1019
m-3)
0,0
0,5
1,0
1,5
li3
p
p
0,0
0,5
1,0
1,5
l i3
0123456
q 0
q min
q
q95
-200 0 200 400 600 800 1000 1200
time (s)
Example of simulation of plasma parameters evolution for WNS-like scenario after switch on Paux and <ne>.
Time of j(r) profile reorganization
~ 3000 s
RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE»
NUCLEAR FUSION INSTITUTE
3d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache.
V. Leonov: Modelling of High-Q Scenario
0,0 0,2 0,4 0,6 0,8 1,00
1
2
3
4
>3000s
200s
1600s
800s
t = 0
q
(see also D.Moreau, I. Voytsekhovitch Nucl. Fus.V.39 (1999), 685)
6
In D.Moreau, I. Voytsekhovitch paper (Nucl. Fus.V.39 (1999), 685) strategy of the initial stage of the discharge (which consists of some stages) with the total time duration ~ some thousand sec is suggested.
This strategy for discharges with a plasma current flat-top ~ some hundred sec (as in our case) is not effective.
RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE»
NUCLEAR FUSION INSTITUTE
3d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache.
V. Leonov: Modelling of High-Q Scenario
We use other strategy including a simultaneous ramp-up of the plasma current in accordance with the plasma minor radius and plasma density increase which gives possibility to decrease time of j(r) profile formation to some tens sec (in our case ~ 50 s). (In this case profile forms layer after layer)
J(r)
rmax
0 0.5 1
7
The model :1.5D ASTRA transport code : 2D equilibrium + 1D transport
i,e =i,e,o f (). Fi, e (S) + i,e
neo, D = Dof ().Fe(S) io = eo = Deo
f () = 1 + 3.2 - radial dependence, DHe= e , Vp= Vp He= 0
Fi, e (S) = exp{4. (S-1)}/(1 + exp{4. (S-1)}) , S = r .(q`/ q)
eo is fitted to provide E=scaling (OH, L or H-98(y2))
Boundary conditions : on the basis of B2-Eirine results approximation:
(Ts/1eV)3/2ns/1019m-3=90 Ploss/1MW
Thermalized Helium pumping speed: to produce He/E = 5.
Impurity: in the coronal approximation
Mean plasma density : is controlled by the gas puff in the kinetic approach.
H & CD : NBI, ECR, LH
RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE»
NUCLEAR FUSION INSTITUTE
3d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache.
V. Leonov: Modelling of High-Q Scenario
8
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0
100
200
300
400
500
600
0
5
10
15
0
5
10
15
Ulo
op (V
)
Wth
Uloop
Ip
I p (M
A)
Paux
Pfus
PauxP fu
s (M
W)
0
20
40
60
80
100
P aux (M
W)
PLH
N
<Te>
n C
<Ti>
<T>
(keV
)
0
1
2
3
4
P loss/P
LH-t
hr
0
2
4
6
8
10 <ne>
<ne>
(10 1
9 m -
3 )
0
200
400
600
Wth (M
J)
0 50 100 150 200 250 3000
20
40
60
80
100
n Ar
P (M
W)
Prad
Ploss
time (s)
0,00,10,20,30,40,50,6
n Ar (
%)
0,0
0,2
0,4
0,6
0,8
1,0
li3
p
p
0,0
0,5
1,0
l i3
0
1
2
3
4
E
024681012
E (
s)
0,0
0,5
1,0
1,5
2,0
Zef
f
Zeff
fHe
0
2
4
6
8
10
12
f He,
f C
(%)
0
2
4
6k
q
a
q95
0
1
2
a (
m),
k
0 50 100 150 200 250 3000
5
10
15
20
25
res (W
b)
res
time (s)
0,00
0,05
0,10
0,15
0,20
0,25
High-Q operational scenario
with RS configuration
Pfus feedback control by ne (Paux=0)
ne feedback control by fuelling
Ploss feedback control by Ar seeding
RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE»
NUCLEAR FUSION INSTITUTE
3d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache.
V. Leonov: Modelling of High-Q Scenario
t = 250 s R (m) / a (m) 6.2 / 2.0 k95 / 95 1.7 / 0.33 BT (T) / Ip (MA) 5.3 / 15.0 q95 3.6<ne> (1019m-3) / (n / nGr) 10.0 / 0.84<Ti > / <Te> (keV) 12.2 / 11.2< T > ( % ) / N 3.56 / 2.53 Pfus (MW) 628 Paux (MW) 0 Q = Pfus / Paux
P loss(MW) / P rad (MW) 74.9 / 52.1 Ploss / P L-H-thr 1.55 fHe (%) / fBe (%) 7.4 / 2 fAr (%) 0.1 Zeff (ave) 1.68
E (s) 4.8HH-98 (y2) 1.3
9
Radial profiles during high-Q operation
RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE»
NUCLEAR FUSION INSTITUTE
3d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache.
V. Leonov: Modelling of High-Q Scenario
t = 250 s (end of high-Q operation)
t = 70 s (start of high-Q operation)
0,0 0,2 0,4 0,6 0,8 1,00
5
10
15
20
25
0,0 0,2 0,4 0,6 0,8 1,00
1
2
3
4
5
Te
Ti T
(keV)
q
0,0 0,2 0,4 0,6 0,8 1,00
10
20
30
40
500,0 0,2 0,4 0,6 0,8 1,00
1
2
3
4
5
Te
Ti
T (keV)
q
10
CONCLUSIONS
Operational strategy including j(r) profile formation layer after layer by
ramp-up of the plasma current simultaneously and in accordance with the
increase of plasma minor radius gives possibility to decrease time of j(r) profile formation to some tens sec.
Long time scale of j(r) profile reorganization gives possibility after
the achieving of RS configuration to work in this configuration some hundreds sec with enhanced confinement at very high Q (Paux= 0).
Simulations demonstrates possibility to control fusion power, plasma
density, power losses to the divertor and some other parameters by
feedback loops in high-Q regime at Paux = 0.
RUSSIAN RESEARCH CENTRE «KURCHATOV INSTITUTE»
NUCLEAR FUSION INSTITUTE
3d ITPA Meeting (Conf. DB and Modelling) 21-23 Oct. 2002, Cadarache.
V. Leonov: Modelling of High-Q Scenario