1Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association...
Transcript of 1Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association...
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J. Bucalossi 1Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA
Report on Tore Supra activities on Mitigation of disruptions loads for ITER
WP09-PWI-08-01/08-02
J. Bucalossi, F. Saint-Laurent, C. Reux
and Tore Supra team
Institute for Research on Magnetic Fusion
Association Euratom-CEA
Annual meeting of the SEWG Transient Heat LoadsLjubljana, 1st/2nd October 2009
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J. Bucalossi 2Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Outline
•Mitigation of disruption loads with massive gas injection
•Control of runaway electron beams
•Activities in 2010
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J. Bucalossi 3Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Outline
•Mitigation of disruption loads with massive gas injection
•Control of runaway electron beams
•Activities in 2010
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J. Bucalossi 4Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Previously on TS
0 0.2 0.4 0.6 0.8 1 1.2 1.410
2
104
106
108
1010
1012
1014
Neu
tron
s pr
oduc
ed d
urin
g du
ring
disr
uptio
n
Initial plasma current [MA]
Non-mitigated disruptions
Helium
Neon
Argon
Mix He/Ar
• With MGI reduction of dIp/dt for all gases (~50%), mild reduction of eddy current in toroidal pumped limiter (TPL)
• Ne and Ar MGI have no effect on RE production• He (He/Ar) MGI are very efficient at suppressing RE even in small
amount (12-500 Pa.m3, plasma ~25m3, vacuum vessel ~50 m3)
NB: MGI triggered disruptions on stable plasmas
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J. Bucalossi 5Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Fuelling efficiency
• Ne was estimated using fast FIR interferometer and approximate integration of several chords
• He assimilation much higher (measurement not possible up to TQ)
TQ
TQ
TQHe reaches plasma edge
Ar reaches plasma edge
0
0.5
1
1.5
2
x 1021 Electrons added to the plasma
N
e
6 8 10 12 14
0
5%
10%
15%
Time from Massive gas injector trigger [ms]
fuel
ling
eff
icie
ncy He - 270 Pa.m3
He - 90 Pa.m3
Ar - 230 Pa.m3
Ar - 120 Pa.m3
• Ne ~ 2x plasma e content with Ar
• Ne > 6x plasma e content with He
• TQ at higher density with He• Only a fraction of the
injected gas reaches the plasma before TQ
NB: fuelling efficiency estimated assuming single ionization and that all the gas reached the plasma before TQ
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J. Bucalossi 6Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Gas penetration
• Determined using a Fast framing visible camera and interference filters for low ionized species (He II 468.5 nm, Ar II 476.5 nm, He I 706.5 nm)
cold front
poloidal plane parallel to the endoscope lens
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J. Bucalossi 7Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Gas jet dynamics
• Penetration depth nearly independent of nature and amount of gas (5 to 500 Pa.m3 in He)
• Penetration speed higher for higher amount of gas (consistent with density measurement) but smaller than gas sound speed (He~1000m/s and Ar~320m/s)
0 100 200 300 400 500 6000
20
40
60
80
100
120
140
Amount of gas injected [Pa.m3]
Co
ld f
ron
t sp
ee
d in
sid
e t
he
pla
sma
[m
.s-1
]
HeliumArgon
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J. Bucalossi 8Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Safety factor influence
Stopping surface
qρ
• Penetration depth nearly constant in safety factor (stop near q = 2)
• Scan in q profile (Ip / Bt variations)• Same He MGI 25 Pa.m3
• q profile reconstructed with CRONOS
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J. Bucalossi 9Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Thermal energy influence
• Scan in LH power (1 to 3.5 MW)• Same He MGI 25 Pa.m3
• q profile reconstructed with CRONOS
• Penetration depth more sensitive to q profile than thermal energy
LH power [MW]
Energy stored
between plasma edge
and gas stopping
surface [kJ]
ohmic 18
1 21.1
2,5 33.1
3,2 40.8
3,5 34
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J. Bucalossi 10Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Penetration “bounce”
0
50
100
SX
R s
ign
al [
a.u
.]
0
0.5
1
Pla
sma
cu
rre
nt [
MA
]
5 10 15 20 25 30
0.8
0.9
1
Time from MGI trigger [ms]
ga
s fr
on
t po
sitio
n [r
/a]
SXR - coreIp
SXR - edge
gas frontposition
(a)
(a)
(b)
(b)
(c)(c)
(d)
(d)
8.8 ms
15.1 ms
18.8 ms
24.4 ms
TQ
He 25 Pa.m3
PLH = 3.5 MW
• Soft X-ray analysis• Core and edge chords behavior correlated with the movement of the
cold front
• Heat pulse from the core to the edge triggered by the perturbation of the q = 2 rational surface (MHD)
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J. Bucalossi 11Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Outline
•Mitigation of disruption loads with massive gas injection
•Control of runaway electron beams
•Activities in 2010
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J. Bucalossi 12Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA RE creates a cold plasma
0 0.5 1 1.50
1
2
3
4
5
6
7
Time (s)
Plasma currentIp (MA)
Line integratedElectron Density(1019 m-2) for 2chords
TS#33707
Photoneutron (s-1)
1010
1012
1014
( N
tn/s
)
0 0.5 1 1.50
1
2
3
4
5
6
7
Time (s)
Plasma currentIp (x100 kA)
Line integratedElectron Density(1019 m-2) for 2chords
TS#33707
Photoneutron (s-1)
1010
1012
1014
( N
tn/s
)
• Line averaged density recovers after the disruption without any gas puffing (RE density ~ only a few 1017 m-2 from RE current)
• A cold background plasma is generated: RE-neutrals collisions (ionization on C dusts and D atoms)? RE-wall interaction?
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J. Bucalossi 13Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA RE beam in action
450 ms plateauExp: 495 µs
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J. Bucalossi 14Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Interaction with dust
-0.1 0 0.1 0.2 0.3 0.40
1
2
3
4
5
6
7TS#43493
Ip (100 kA)nl (1019 m-2) chord#3
Time (s)
1010
1014
1012
neutron (s-1)
nl (1019 m-2) chord#4
-0.1 0 0.1 0.2 0.3 0.40
1
2
3
4
5
6
7TS#43493
Ip (100 kA)nl (1019 m-2) chord#3
Time (s)
1010
1014
1012
neutron (s-1)
nl (1019 m-2) chord#4
• Many photoneutron peaks, large peaks associated to density rises and radiating events
• Radiating events associated to transverse transport of RE• Filamentary events observed using fast visible camera• Location and radial size of RE beam can be estimated
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J. Bucalossi 15Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Controlling beam position
• Controlling the beam position is an important issue• Active position control on current channel barycentre was
implemented 30 ms after the disruption (no Ip control nor fuelling so far)
• More time to apply mitigation technique on the RE beam
0 0.5 1 1.5
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
Time -tdisr (s)
TS#33707TS#43491
Rb
ary
cen
tre
(m)
disruption
RE plateau
Without
With
0 0.5 1 1.5
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
Time -tdisr (s)
TS#33707TS#43491
Rb
ary
cen
tre
(m)
disruption
RE plateau
Without
With
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J. Bucalossi 16Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Decelerating electric field
• Variation of the central solenoid voltage with RE beam position control
0 500 1000 15000
0.1
0.2
0.3
0.4
0.5
0 200 4000
0.1
0.2
0.3
0.4
0.5
TS#43491
Neutrons (s-1)
Time -tdis(ms)
TS#43493
Ip (MA)
Time -tdis(ms)
ECS = 0 mV/m 35 mV/m
Ntn = 2.5 1012
Ntn = 1.7 1012
1011
1012
1013
1014
1015
Mechanical load (a.u)
0 500 1000 15000
0.1
0.2
0.3
0.4
0.5
0 500 1000 15000
0.1
0.2
0.3
0.4
0.5
0 200 4000
0.1
0.2
0.3
0.4
0.5
0 200 4000
0.1
0.2
0.3
0.4
0.5
TS#43491
Neutrons (s-1)
Time -tdis(ms)
TS#43493
Ip (MA)
Time -tdis(ms)
ECS = 0 mV/m 35 mV/m
Ntn = 2.5 1012
Ntn = 1.7 1012
1011
1012
1013
1014
1015
Mechanical load (a.u)
• Reduction of the plateau duration with a small voltage (~0.5 V/turn)• Photoneutrons reduced (~30%) but still a neutron burst at the end• Further studies required
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J. Bucalossi 17Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Effect of MGI on RE beam
0 0.2 0.40
0.1
0.2
0.3
0.4
0.5
0.6
0 0.2 0.40
0.1
0.2
0.3
0.4
0.5
0.6
TS#33711 TS#43512
He MGI
Ar MGI
Time (s)
Ip (MA) Ip (MA)
Neutron (s-1)
Neutron (s-1)
1011
1012
1013
1014
1015
4 1021 at/m3 6 1020 at/m3
5.5 1012 ntn 1.3 1012 ntn
0 0.2 0.40
0.1
0.2
0.3
0.4
0.5
0.6
0 0.2 0.40
0.1
0.2
0.3
0.4
0.5
0.6
TS#33711 TS#43512
He MGI
Ar MGI
Time (s)
Ip (MA) Ip (MA)
Neutron (s-1)
Neutron (s-1)
1011
1012
1013
1014
1015
4 1021 at/m3 6 1020 at/m3
5.5 1012 ntn 1.3 1012 ntn
Xo Density thickness dE Stop Time Exp.
(g cm-2) (at/m3) 1 turn (g cm-2) (eV) (ms) (ms)
He 94.3 4 1021 2.7 10-5 58 10 150
Ar 19.6 6 1020 4.3 10-5 87 7.5 35
Tabulated using an averaged RE energy E = 10 MeV
• faster decrease of RE current• increase of the photoneutron flux• slowing down by neutrals not
effective
• Increase of the RE transverse transport towards the wall: Multiple Coulomb scattering = stochastic effect larger interacting area lower heat loads
• Beneficial effect for mitigating RE
3/ Heo
Aro 5/ He
ntnArntn
Simple assumption of a free stopping in neutral gas
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J. Bucalossi 18Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Damages on CFC tiles
• large energy deposit leads to vaporization of CFC bulk and fast expulsion of carbon fragments (200-600 m/s)
• Detailed Monte-Carlo simulation of RE-carbon interaction in progress
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J. Bucalossi 19Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Outline
•Mitigation of disruption loads with massive gas injection
•Control of runaway electron beams
•Activities in 2010
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J. Bucalossi 20Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Activities in 2010
•MGI
– radiated power analysis with “faster” bolometers
– better characterization of the gas jet
– modeling effort (CRONOS, JOREK, etc.)
•RE beam control
– improve statistics (reliable RE beam creation)
– study of mitigation of RE beams with MGI
– modeling of RE beam damping
•IR fast camera (from ASDEX Upgrade)
– analysis of SOL widening on the TPL during disruption
– estimation of conducted heat loads on the TPL during TQ
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J. Bucalossi 21Annual meeting SEWG Transient Heat Loads, Ljubljana, 1st/2nd October 2009
TORE SUPRAAssociationEuratom-CEA Summary
•MGI
– Fuelling efficiency estimated
– Data gathered on gas penetration
•Runaway electrons
– Cold background plasma observed
– Interaction with dusts observed
– Active position control achieved
– Mitigation techniques applied to created RE beam
•2010
– More experiments planned
– New diagnostic (fast IR camera)
– Modeling effort