Achievements and open issues in impurity profile control at JET. M. Valisa and
E1/E2 Meeting, 7 April 2011 1 Achievements and open issues in impurity profile control at JET. M....
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Transcript of E1/E2 Meeting, 7 April 2011 1 Achievements and open issues in impurity profile control at JET. M....
1
E1/E2 Meeting, 7 April 2011
Achievements and open issues in impurity profile control at JET.
M. Valisa and Angioni Carraro Coffey Lauro-Taroni Predebon PuiattiAlper Belo Corrigan vanEester Garzotti Giroud Lerche Mantica Naulin Tala Tsala et al
JET E1\/E2 meeting - Culham 7 April 2011
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E1/E2 Meeting, 7 April 2011
Outline
Background
What we have learnt at JET of the effect of RF on impurity transport
Open Issues
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E1/E2 Meeting, 7 April 2011
Impurity accumualtion avoidance may require Active Control to guarantee stationary plasma fusion experiments and optimization of reactor efficiency.
Codes validation is required to include impurities and their control in a ITER/ DEMO flight simulator
RF well know empirical means to pump out impurities in present day experiments. Underlying mechanims still uncertain.
Background 1
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E1/E2 Meeting, 7 April 2011
• For core issues, what really matters is the relationship between
D_impurities , D_fuel and e,i , since the relevant parameter is dilution.
• Used impurity density perturbations (= trace impurity )to work out impurity transport as with laser ablation. Modelling of the transient evolutions of the impurities provides an estimate of the transport coefficients.
Background 2
nnD v+ accurate atomic physics
Used 1D transport model with
Main diagnostics for metal impurities: SXR, emission lines , bolometry
At stationarity
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E1/E2 Meeting, 7 April 2011
Change RF deposition profile (heat modulation to work out heat transport – P Mantica Gas modulation or pellet for DD – L Garzotti)
Shown that D imp and e,i in some situations go together
See ME Puiatti et al PoP 2006
RF (3He minority) deposition radius
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E1/E2 Meeting, 7 April 2011
M-E. Puiatti PoP 13 2006 ; C. Angioni et al PRL 2006
RF power on electrons is effective as a means to control heavy impurities in JET low collisionality regimes
eff [=10-14 <ne > <Te >–2 Zeff R ] ≤0.2
MH 58144
MC 58149
Dominant ITG inward v
Subdominant TEM outward v
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E1/E2 Meeting, 7 April 2011
RF power as a means to control heavy impurities also in JET Elmy H mode / HIGH DENSITY and Ar puffing in JET
•Core diffusion decreases
•Core convection also decreases and may become outward
NO ICRH
Shot 52136: Strong INward convection
Shots 53548 , 53015 WITH ICRH:
convection may become OUTward
M.E. Puiatti et al .Plas. Phys.Contr. Fus. 44(2002)1863
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E1/E2 Meeting, 7 April 2011
LBO & ICRH power scan: Ni and Mo areexpelled from the centre as power increases
H minority / H mode / low collisionality/ about 12 MW NBI, 1.5MA, 3T
= 0.2
Ni and Mo
68383 and 81 – marginal H mode(L-mode, but P>>LH threshold)Low collisonality, Similar triangularity and elongation
Mo( 42) and Ni ( 28):similar behaviour
Open symbols Shots around 58140He3 minority
RF power scan
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E1/E2 Meeting, 7 April 2011
GS2 Simulation of the shots with RF power scan
No sign of flow inversion with increaasing RF
Quasi linear, electrostatic
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E1/E2 Meeting, 7 April 2011
Discharges of the RF power scan
= RF Power increase“ “
Target Plasma:
Ip=1.5 MAB= 3TNBI= 12 MWLow triangularityNo sawteethCentral ICRH
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E1/E2 Meeting, 7 April 2011
RF power scan and LBO injection of Ni
= 0.2
Nickel
Out of many correlation attempts ( with rotation, Ti/Te, q and q shear etc ) the best correlation is with R/LTi
Signature of a neoclassical trend?
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E1/E2 Meeting, 7 April 2011
= 0.2
Good correlation of v/D with R/LTe
NO RF
1 MW RF
3MW RF
Stationary profiles : extrapolation using evaluated vand D’s
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E1/E2 Meeting, 7 April 2011
neoclassical V and D from NCLASS
Neoclassical transport parameters too small:do not macth the experiment
0.05
0.2
0
0.15
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E1/E2 Meeting, 7 April 2011
Sensitivity study on neoclassical transport
chord integrated central SXR emission during theinjection of Ni in discharge 74360
ExperimentSimulation - normalized
V neo and D from Exp.
v neo and v/D from Exp
LBO
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E1/E2 Meeting, 7 April 2011
D’s and V’s in the ICRH scan database
Impact of RF scan seems to be more on v than on D
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E1/E2 Meeting, 7 April 2011
Open Issues
- Role q and q shear? Required shots with similar settings but different timing of LBO during pulseor different timing of ICRH and or NBI
- Role of rotation and shear rotation ? Counter beam or different share of ICRH and NBI keeping total power constant.
1,4
1,6
1,8
2
2,2
2,4
2,6
2,8
44 45 46 47 48 49 50 51
q
74354743557435674360
q(r
ho
=0
.2)
t(s)
ICRH
1) Understand the pump out effect of ICRH
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E1/E2 Meeting, 7 April 2011
Open Issues
- Is there a direct role of the RF itself ?
Test different heating schemes – ICRH on fundamental harmonic ,He3 minority heating
-Are neoclassical terms correctly evaluated?
- In/out asymmetries / role of centrifugal forces. Impact on analysis
Can sawteeth be as efficient as RF ? How large and frequent must ST be? Shown in the past that if small their efficiency is smaller than 2MW RF (Puiatti et al PPCF 2003)
2) Issue of poloidal asymmetries
3) Efficiency of RF compared to sawteeth
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E1/E2 Meeting, 7 April 2011
Open Issues
4) Effect of ICRF on Zeff In #68383 ( 8 MW ICRH ) Zeff increase from 2 to 4-5 with Zeff from C nearly constant ( L Carraro et al EPS Warsaw) See also JET works by Czarneka where the problem has been investigated in some details. Lot of work also on other machines.
5) Analysis Tools for dealing with Tungsten
- Do we have reliable tools for detection and analysis ?- Will W radiation be overwelming to make traditional techniques( such as LBO with Ni and Mo) useless?
6) How to implement a feedback control system on impurity accumulation
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E1/E2 Meeting, 7 April 2011
Data available are:• some SXR/VUV spectroscopic lines (KT2 and KT4) with a fairly coarse time resolution. Have lines been identified ? • Soft-X rays: a vertical camera with 34 l-o-s (250μ filter) and a horizontal camera with 17 channels (350μ filter).
Detection and analysis of W on JET
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E1/E2 Meeting, 7 April 2011
Heavy impurity transport simulations.Available the predictive impurity transport simulation JETTO/SANCO
The ADAS tables can be used to calculate the local emissivities that integrated along the various l-o-s can simulate the experimental SXR channels
Standard treatment: ZI +1 equations with ionisation and recombination to and from neighbouring ionised states provided by ADAS/adf11 tables.
Superstages treatment: Reduced set of equations each representing a ‘bundle’ of contiguous ionised stages (a ‘superstage’) in coronal equilibrium between each other.
W from 74 to 35 , or more aggressively down to 10 superstages.
Detection and analysis of W on JET
See L Lauro-Taroni H Summers et al presentation at the General Task Force T Meeting 16 February 2009
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E1/E2 Meeting, 7 April 2011
Tungsten data available at JET
Most recent W LBOs have been performed during C17 (Nov 2006):68373 3.2T/2.3MA 4.5 MW ICRH, 8.9MW NBI, 0.5 MW LHCD68374 6 MW ICRH, 8.9 MW NBI, 0.8MW LHCD68387 7.7 MW ICRH, 9 MW NBI, 1.1MW LHCD
68373SXR
BOLO
W LBO data available at JET available for testing tools
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E1/E2 Meeting, 7 April 2011
SXR Horizontal cameras - B.Alper 68373. W ablation at t=55 s
Example of SXR after LBO of W shwoing central peaking
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E1/E2 Meeting, 7 April 2011
SXR Vertical Camera ( B.Alper) 68373 W ablation at t=55
In-Out Asymmetry
Example of SXR after LBO of W showing polidal asymmetry
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E1/E2 Meeting, 7 April 2011
Different superstages partitions of W 74 ion (no bundling)35 superstages: natural bundling26 superstages: natural bundling, with 55+ upwards bundled into 2 SS 10 superstages: ions with ionisation potential >800 eV bundled into 1 SS
( for edge plasmas).
But the partition into 10 SS yields a slightly different SXR simulation, with a faster rise in the initial phase. ONGOING WORK
Could be superstage treatment be included in feedback controlled system?
All partitions yield the same nW(x,t), same total number of particles, same Power
Effect of ionization stages partitioning has been tested
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E1/E2 Meeting, 7 April 2011
SXR
Black: V Ch. 3 (peripheral)
Red: V Ch 12 (central)
Light blue: H Ch11 (central)
SXR
-500
0
500
1000
1500
2000
2500
3000
3500
4000
54.95 55 55.05 55.1 55.15 55.2 55.25 55.3 55.35 55.4 55.45
time
W/m
2
W source
ΔP bolo
P sim
D (m2/s)
50
100
V (m/s)
Example of ongoing work: simulation of Prad and SXR after W LBO
time
time
ρ Jetto
By L Lauro-Taroni
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E1/E2 Meeting, 7 April 2011
Summary and conclusions
• Central ICRH effective on JET to pump out Ni and Mo which feature peaked profiles in JET NBI only H mode plasmas
About 3 MW ICRH required in the analysed shots
• W : only very Preliminary analysis by Lauro Taroni
• Mechanism for impurity pump out? Trends recall neoclassical transport ( proportional to R/LTi) but absolute values do not fit
• Ni (28) and Mo(42) seem to behave similarly , and W?? •ICRH is accompanied by higher Zeff .
• Possibility of treatment of W in superstages successfully implemented in JETTO/SANCO (ADAS files for bundled impurities can be generated )
Simulations of a Tungsten injection in JET started
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E1/E2 Meeting, 7 April 2011
SHOT Ip(MA) Bt(T) NBI (MW) ICRH (MW) H/He3
58143 1.8 3.27 13.6 4.7 He3
58149 1.8 3.27 14.6 5.1 He3
66432 1.8 3.35 20 2 He3
66434 1.8 3.35 20 2 He3
68383 2.3 3.2 8.3 8 H
69808 1.8 3.2 11 0 H
74354 1.5 3 12 0 H
74355 1.5 3 12 1 H
74359 1.5 3 12 3 H
74360 1.5 3 10.7 2.9 H
74363 1.5 3 10.5 2.9 H
Ni injections
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E1/E2 Meeting, 7 April 2011
68381 2.3 3.2 9 8.45 H
74357 1.5 3 12.5 0 H
74362 1.5 3. 10.5 3 H
Mo injections
SHOT Ip(MA) Bt(T) NBI (MW) ICRH (MW) H/He3