Transcript Litio PSI - Consorzio RFX

Lithization on FTU:
tools and results
G. Mazzitellia
Many thanks to:M.L. Apicellaa, V. Pericoli Ridolfinia, A. Alekseyevb, G.
Apruzzesea, W. Binc, P. Burattia, R. Cesarioa,, G. Calabròa, R. De Angelisa, B.
Espositoa, L. Gabellieria, F. Gandinic, E. Giovannozzia, R. Gomesd, G. Granuccic , H.
Kroeglera, I. Lyublinskie , M.Marinuccia, C. Mazzottaa, A. Romanoa, O. Tudiscoa, A.
Vertkove, the FTU Teama and ECRH Teamc
a Associazione
EURATOM-ENEA sulla Fusione, C. R. Frascati,00044 Frascati, Roma, Italy
b TRINITI, Troitsk, Moscow reg., Russia
c Associazione EURATOM-ENEA, IFP-CNR,Via R. Cozzi,53-20125 Milano Italy
d Centro de Fusao Nuclear, IST Av. Rovisc Pais,n.1 1049-Lisboa Portugal
e FSUE,“RED STAR”, Moscow, Russia
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Introduction
• Why Lithium ?
– Very low Z (Z=3)
– High impurity getter (C,O)
– High H retention
Recycling
– Low melting point (180.6 ° C)
– Strong reduction of total graphite sputtering
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Introduction
• Where Lithium (How) ?











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DIII-D (DIMES)
Negative
Alcator C-MOD (Pellet)
Negative
TFTR (Pellet)
Good
JIPP T_IIU (Evaporation)
Good
T-11 (Capillary Porous System)
Good
NSTX (Evaporation+Powder)
Good
CDX-U (Evaporation+liquid Tray)
Good
TJ-II (Evaporation)
Good
T-10 (Evaporation)
Good
LTX (Liquid wall)
Starting
FTU (Capillary Porous System)
Good
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OUTLINE
1. Experimental Setup
2. Experimental Results
 High density peaked discharges
 Quasi-quiescent MHD discharges
 ECRH + LH Discharges
3. Future plans
4. Conclusions
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1. Experimental Setup
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Liquid Lithium Limiter
Langmuir probes
Thermocouples
Heater electrical
cables
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Capillary Porous System (CPS)
The LLL system is composed by three similar units
Liquid lithium surface
Mo heater accumulator
Thermocouples
Heater
Li source
S.S. box with a
cylindrical support
100 mm
CPS is made as a
matt from wire
meshes with porous
radius 15 m and
wire diameter 30 m
Structural material
of wires is S.S.
34 mm
Ceramic break
Scheme of fully-equipped lithium limiter unit
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Meshes filled
with Li
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Toroidal Limiter
Total lithium area
Plasma interacting area
Inventory of lithium
LLL initial temperature
~ 170 cm2
~ 50- 85 cm2
 80 g
> 200oC
Liquid Lithium Limiter
Melting point 180.6 °C
Boiling point 1342 °C
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2. Experimental Results
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Main features of lithium operations:
1. Better plasma performances with Lithium than with Boron
2. Zeff in ohmic discharges is well below 2(0.15 1020<ne<3.1020m-3)
 The VUV spectrum is dominated by the Li lines
 O, Mo are strongly reduced
3. Radiation losses are very low less than 30%
4. With lithium limiter much more gas has to be injected to
get the same electron density with respect to boronized
and fully metallic discharges > 10 times
5. Operations near or beyond the Greenwald limit are easily
performed
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Main features of lithium operations:
6. In lithium discharges, Te in the SOL is 50% higher than
before while the increase in ne is negligible
7. Plasma operations are more reliable with good plasma
reproducibility and easier recovery from plasma
disruptions
8. The LLL is able to withstand heat load up to 5 MW/m2
More details:
• Apicella et al. J. Nuclear Materials 363-365 (2007) 1346-1351
• V. Pericoli Ridolfini et al. Plas. Phys. Contr. Fusion 49 (2007) S123-S135
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Peaked electron density discharges
Ip=0.5MA Bt=6T
Ip=0.7MA Bt =6 T
3
3
#30584
-3
r=0.0 m
e,line
n
eline
[x10
n
2
[x10
20
20
2
m ]
r=0.0 m
-3
m ]
#30583
1
1
r=0.235 m
r=0.235 m
0
0
0
0,4
0,8 t (s) 1,2
0
1,6
0,3
0,6
t(s) 0,9
1,2
At electron density greater than 1.0 1020 m-3
spontaneously the density profile peaks
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Peaked electron density discharges
Central density increases while edge and SOL densities do not change
The SOL densities do not follow the FTU scaling law
neSO L  n1.e46
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Peaked electron density discharges
The profile is peaked as with pellet injection
5
#30583
#26793
4
5
ne [x1020 m-3]
4
[x 10
20
-3
m ]
The profiles are taken at different times
but at the same line-averaged density
3
2
n
e,line
3
2
r=0
1
1
r=0.2 m
0
0
0,5
t(s)
1
1,5
0
0,6
0,7
0,8
0,9
R (m)
1
1,1
1,2
1,3
The strong particle depletion in the outermost plasma
region is due to the strong pumping capability of lithium
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Energy Confinement Time
If the confinement time of lithized discharges is compared with the general behaviour of
the confinement time of the ohmic and pellet fuelled FTU discharges database, it clearly
results that the threshold of the SOC regime is raised from ~45÷50 ms to ~65÷70 ms,
suggesting a behaviour which is akin to that shown by multiple-pellet PEP regimes
120
t
100
80
60
40
20
k = 7.1±0.6
20
t (ms)
E
E-linear
-3
1.41±0.07
= k ne,lin(10 m ) q
0.5 MA
0.8 MA
1.1 MA
1.4 MA
pellet: open symbols
0.50 MA Li
0.75 MA Li
0
1
2
3
20
4
-3
line averaged ne (x10 m )
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Quasi-quiescent MHD activity
Te at the edge is geneally higher
than in boronized discharges
A possible theoretical explanation is proposed in which electrostatic waves
excited by thermal background in the plasma core enhance the turbulence at
the edge via non-linear mode coupling.
R. Cesario et. EPS Conference 2007
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ECRH + LH Discharges
0.54 s 0.59 s
#30620 With LLL
PECH=0.80 MW
.5
I [MA]
PLH =0.75 MW
p
7
5
3
#27923 Without LLL
19
-3
n [10
e
6
4
2
PECH=1.20 MW
m ]
PLH =1.50 MW
T [KeV]
e
#27923
2
1
P [MW]
ECH
LH
#30620
2
1
P [MW]
0.3
0.4
LH
ECH
0.5
Strong and wide ITB develops
after LH injection, with very
high central Te up to 8 KeV in
spite of the lower value of
additional power
0.6
t(s)
Very interesting features are obtained with combined ECR+LH Power
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ECRH + LH Discharges
8
rITB/a
0.6
Te[keV] 0.54 s
6
4
Padd=1.6MW
0.4
Padd=1.6MW
0.2
Radial extension of ITB
2
0
-0,2
-0,1
6
Te[keV]
5
0
ρ*T
0,1
0.02
B
0.59 s
4
Padd=1.2MW
3
Padd=2.2MW
2
0.01
0.3
1
0
-0,2
Strength of ITB
0.4
0.5
t (s)
ρ*T,max=Max of the normalized Te gradient
-0,1
r (m)0
0,1
B
A wide ITB is formed with a strong Te gradient
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ECRH + LH Discharges
1,5 10
Counts
4
1 10
4
#27923
Mo
Fe
O
5000
4
1,5 100
Counts
1 10
#30620
4
Li lines
5000
0
100
150
200
250

( A )
300
The strong difference between the two discharges is in the impurity
content. Zeff is reduced by at least a factor 2 in lithium discharges that
increases the LH current drive efficiency
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ECRH + LH Discharges
5
11
neutrons/s [x10 ]
4
But Zeff ~ 2 means
about 50% of dilution
as indicated by the
strong reduction in
neutron signal.
3
#27823
2
1
#30620
0
0
0,2
0,4
0,6
t(s)
The dilution is strictly correlated with the plasma
start-up phase and the low value of electron density
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Dilution
1.0
0.5
Ip [MA]
3.0
2.0
30584 LLL Inside
29919 lithized
ne [x1020 m-3]
28847 metallic
1.0
28833 boronized
2.0
Te [KeV]
1.0
4.0
Neutrons/s [x1011]
2.0
0.
0.2
0.4
0.6
0.8
1.0
At higher electron densities dilution is negligible
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3. Future Plans
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No Surface Damage of CPS Structure
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A new limiter panel type actively cooled and
equipped with a system for lithium refilling
Preliminary design
Top view
Toroidal lmiter
LLL
LLL
This limiter should be able to act as main limiter for
withstanding heat loads up to 10 MW/m2 for 3 s
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4
2
5
3
25
FTU Vacuum
Vessel
Lithium Limiter
FTU Port
26
27
CONCLUSIONS
•Lithization is a very good and
effective tool for plasma operations
•Exposition of a liquid surface on
tokamak has been done on FTU with
very promising results
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Thank youG.for
your attention Padova 21/01/09
Mazzitelli
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Dilution Problem
It is strictly correlated with the plasma start-up phase and the
absolute value of density
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ECRH + LH Discharges
3
0.40 s
5
2
Te[keV]
Te[keV]
4
0.48 s
1
No Padd
0
-0,2
-0,1
0
r (m)
0,1
3
Padd=0.8MW
2
Padd=0.0MW
B
#30620
#27923
1
0
-0,2
r (m)0
0,1
B
8
Te[keV]
-0,1
6
Te[keV]
0.54 s
5
0.59 s
6
4
Padd=1.6MW
4
Padd=1.6MW
Padd=1.2MW
3
Padd=2.2MW
2
2
1
0
-0,2
-0,1
r (m)
0
0
-0,2
0,1
-0,1
r (m)0
0,1
B
B
Comparison of electron temperature profiles showing ITB formation
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(%) T (KeV) n (x10 m )
Comparison between Lithization and Boronization
19 -3
7.5
af t er lith.
af t er boron.
7
ne(x1019m-3)
Ohmic shots
e
6.5
1.8
ohm
1.6
50
40
30
20
10
0.95
0.9
0.85
0.8
Zeff
Z
eff
V
loop
rad
(V) P /P
Prad(%)
Vloop(V)
Ip=0.5MA Bt=6T
2
e
Te(keV)
6
ti m e
1.8
1.6
1.4
1.2
0.6
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The Li effects
are similar or
even better
than those of B
0.8
1
ti me (s)
Time(s)
1.2
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Zeff was well below 2 during all the experimental campaign
After liquid Lithium limiter insertion
4
0.15x1020 m-3<ne<2.7x1020 m-3
3,5
0.5MA<Ip<0.7MA Bt=6 T
3
Zeff
2,5
2
1,5
1
0,5
0
0
50
100
Shots
150
200
Zeff is always well below 2 with lithizated wall
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Np(×1020 plasma particles)
Strong D2 pumping capability
After
Lithization
much more gas has to
be injected to get the
same electron density
with
respect
to
boronized and fully
metallic discharges
Ng(×1021 injected particles)
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500
2
Surface temperature
deviation from ANSYS
calculation at about 1s
is probably due to Li
radiation in front of
the limiter surface.
2 MW/ m
0
Surface temperature T ( C)
Thermal analysis
450
400
350
300
T1
T2
T3
T2
250
(exp. )
(exp. )
(exp. )
(ANSY S)
Calculation
with
TECXY code support
this hypothesis
200
0
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0.5
1
time (s)
1.5
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High capability to sustain high thermal loads
1.4
Ne
Strong density peaking
(x1020m-3)
1.0
Heat load
exceeding 5
MW/m2
.6
2.
450 º C
T1,2,3
1.
midplane
0.
Vertical Plasma
Position
- 0.2
Z (cm)
0.9
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Time(s)
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Electron thermal diffusivity
1.6
e
Electron thermal
diffusivity is
significantly lower for
the lithizated discharge
with respect to the
metallic one
2
(m /s)
1.2
0.8
0.4
metallic wall
lithized wall
0
0.05
0.1
0.15
0.2
0.25
minor radius (m)
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Lithium
• Isotopic Abundances
6Li 7.59%
7Li 92.41%
• Melting point
180.54 °C
• Boiling point
1342 °C
• Nuclear Reactions
6Li + n
T + a + 4.8 MeV
7Li + n
T + a + n’ - 2.87 MeV
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LITHIUM DETECTION
LITHIUM REACTS WITH WATER GIVING A BASIC
SOLUTION:
2Li(s,l,g) + 2H2O(l,g) → 2LiOH(aq,g)+ H2 (g)
USING A A WHITE CLOTH IMBUED WITH A
SOLUTION OF PHENOLPHTHALEIN (ACID-BASE
INDICATOR ) WE CAN DETECT LITHIUM DROPS
BECAUSE
THE
SOLUTION
TURNS
FROM
COLORLESS(ACID-NEUTRAL SOLUTION) TO RED
(BASIC SOLUTION) IN PRESENCE OF LITHIUM.
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