Initial experiments with liquid target materials in PSI-2 and TEXTOR
Initial experiments with liquid target materials in PSI-2 and TEXTOR
Initial experiments with liquid target materials in PSI-2 and TEXTOR
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Member of the Helmholtz Association<br />
<strong>Initial</strong> <strong>experiments</strong> <strong>with</strong> <strong>liquid</strong> <strong>target</strong><br />
<strong>materials</strong> <strong>in</strong> <strong>PSI</strong>-2 <strong>and</strong> <strong>TEXTOR</strong><br />
B. Unterberg, J.W. Coenen, A. Kreter, V. Philipps, M. Re<strong>in</strong>hart, G.<br />
Sergienko, A. Terra <strong>and</strong> T. Wegener<br />
Institut für Energie- und Klimaforschung – Plasmaphysik<br />
Forschungszentrum Jülich, Ass. EURATOM- Forschungszentrum Jülich,<br />
Trilateral Euregio Cluster, D- 52425 Jülich, Germany<br />
4th IEA International Workshop on Plasma Material Interaction Facilities for<br />
Fusion Research (PMIF 2013), Oak Ridge, TN, USA, September 9th – 13th 2013
Program on <strong>liquid</strong> <strong>target</strong>s <strong>in</strong> Jülich<br />
§ After assessment of<br />
alternative <strong>target</strong><br />
concepts, FZJ<br />
concentrates on<br />
alternatives to Li <strong>in</strong> CPS<br />
configuration, <strong>in</strong> the<br />
frame of the co-ord<strong>in</strong>ated<br />
EU fusion program<br />
(EFDA-PEX) <strong>and</strong> <strong>in</strong> TEC<br />
collaboration <strong>with</strong> FOM-<br />
DIFFER<br />
§ Development of samples<br />
for exposure <strong>in</strong> <strong>PSI</strong>-2 <strong>and</strong><br />
<strong>TEXTOR</strong><br />
Ø Report on <strong>in</strong>itial<br />
<strong>experiments</strong> <strong>with</strong> t<strong>in</strong><br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 2
Optimization of temperature w<strong>in</strong>dow<br />
motivates work on alternative <strong>materials</strong><br />
Temperature limit<br />
§ Lower limit<br />
§ Melt<strong>in</strong>g<br />
§ Wett<strong>in</strong>g<br />
§ Upper limit<br />
§ Evaporation flux: impact on<br />
plasma performance, redeposition,<br />
migration to<br />
remote areas<br />
§ Chemistry (e.g. LiH<br />
formation), corrosion / alloy<br />
formation (large w<strong>in</strong>dow for<br />
Li, show stopper for Ga)<br />
Evaporation rates<br />
[R. Majeski, "Liquid metal walls, lithium,<br />
<strong>and</strong> low recycl<strong>in</strong>g boundary conditions <strong>in</strong><br />
tokamaks" AlP Conf. Proc. vol. 1237, 122.]<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 3
Re-Deposition<br />
Factor 10 <strong>in</strong>crease <strong>in</strong> redepostion<br />
enhances T<br />
w<strong>in</strong>dow by
Material compatibility of t<strong>in</strong> <strong>with</strong> mesh metals<br />
SST/Ga SST/Sn Mo/Sn W/Sn<br />
SST show a strong ability to form<br />
alloys <strong>with</strong> all <strong>in</strong>vestigated <strong>liquid</strong> metal<br />
c<strong>and</strong>idates.<br />
Mo alloys <strong>with</strong> <strong>liquid</strong> Sn but <strong>in</strong> very<br />
small amounts. EDX analysis shows<br />
small <strong>in</strong>clusions (
Wett<strong>in</strong>g<br />
950 °C<br />
10 -6 mbar<br />
Wett<strong>in</strong>g - contact angle < 90°<br />
Adhesion > Cohesion<br />
Mo/Sn<br />
“Clean” metal surfaces are<br />
normaly wettable <strong>with</strong> <strong>liquid</strong><br />
metals<br />
BUT they nearly always have<br />
oxide layers which reduce the<br />
wettability of the surface!<br />
No Wett<strong>in</strong>g - contact angle >90°<br />
990 °C<br />
10 -6 mbar<br />
W/Sn<br />
1mbar H 2<br />
950°C<br />
W/Sn<br />
Adhesion < Cohesion<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 6
Overview of wett<strong>in</strong>g characteristics<br />
Contact angle<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 7
L<strong>in</strong>ear plasma device <strong>PSI</strong>-2<br />
Plasma<br />
source<br />
Coils<br />
TEAC<br />
Target<br />
manipulator<br />
Side-fed<br />
manipulator<br />
Periphery<br />
level<br />
3 m<br />
§ Plasma conditions (deuterium<br />
plasmas), <strong>with</strong> <strong>target</strong> bias<strong>in</strong>g<br />
q = 0.1 -2 MW m -2 , simulation of<br />
transients by laser irradiation<br />
(120 J / 4 ms)<br />
n e = 10 17 - 10 19 m -3<br />
T e up to 20 eV (T i ~ 0.5 T e )<br />
E ion = 10-300 eV (bias<strong>in</strong>g)<br />
Γ ion = 10 21 - 10 23 m -2 s -1<br />
F = 10 27 m -2 <strong>in</strong> 4 h<br />
Δ flow channel ~ 6 cm<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 8
Target holder <strong>in</strong> <strong>PSI</strong>-2<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 9
Setup<br />
Tungsten Mesh: d=0.1-0.2mm<br />
molybdenum disk & mount<strong>in</strong>g plate<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 10
Exposure<br />
Infra-red<br />
visible<br />
IR-Camera Pyrometer Pyrometer<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 11
Exposed samples<br />
Empty<br />
Before<br />
After<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 12
Material Cuts<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 13
Exposure characteristics<br />
Plasma characteristics<br />
§ Total exposure time (D2-<br />
plasma): 64 m<strong>in</strong>.<br />
§ Plasma parameters <strong>in</strong><br />
front of <strong>target</strong>: n e =<br />
8x10 17 m -3 /T e = 9 eV<br />
§ Plasma flux density:<br />
5x10 21 m -2 s -1<br />
Surface temperature<br />
§ Heat flux density: 60<br />
kWm -2 (no bias<strong>in</strong>g) Equilibrium reached after ~900s<br />
IR-cam: temperature variation across<br />
sample ≤ ±100° C<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 14
Sn mass loss <strong>in</strong> dur<strong>in</strong>g exposure<br />
§<br />
§<br />
§<br />
§<br />
Total loss: 240 mg (of 1139mg)<br />
Surface temperature needed<br />
for evaporation of 240 mg:<br />
1120°C (full area)<br />
“effective erosion yield”:<br />
Y=0.15 >> Y sputter<br />
Penetration depth of Sn atoms:<br />
λ= 1.7 cm, E k<strong>in</strong> =1.5 eV >> E k<strong>in</strong><br />
=0.15 eV (evaporated Sn)<br />
Ø Indicat<strong>in</strong>g sputtered particles<br />
§<br />
SnI <strong>in</strong>tensity ris<strong>in</strong>g dur<strong>in</strong>g<br />
<strong>in</strong>crease of <strong>target</strong> temperature,<br />
<strong>in</strong>dication of temperature<br />
enhanced erosion?<br />
Intensity distribution SnI (380 nm)<br />
<strong>target</strong><br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 15
<strong>TEXTOR</strong> experiment: Aims<br />
A:<br />
T<strong>in</strong> Evaporation<br />
Temperature Evolution<br />
T<strong>in</strong> Spectroscopy<br />
Liquid Metal Stability<br />
under quiescent Plasmas<br />
B:<br />
Stability of Liquid T<strong>in</strong> Layers<br />
under Disruptive Events<br />
DMV triggered disruptions<br />
And be prepared for suprises<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 16
Setup<br />
Tungsten Mesh filed <strong>with</strong> T<strong>in</strong><br />
TZM Holder<br />
filled<br />
empty<br />
Heatable Limiter-Setup<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 17
Conditions<br />
T<strong>in</strong> surface<br />
The Limiter is preheated to<br />
300˚C, to allow <strong>liquid</strong> T<strong>in</strong> to<br />
be present at all times<br />
Position at the Bottom of<br />
<strong>TEXTOR</strong><br />
TZM<br />
Graphite<br />
49cm, LCFS ~ 47cm<br />
1MW NBI heated (1-4.5s) BT=2.25 T, Ip=350 kA<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 18
Exposure<br />
Before<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 19
Wetted surface<br />
After<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 20
Wett<strong>in</strong>g Loss<br />
After<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 21
Camera View<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 22
3 frames<br />
#119916<br />
Strong droplet mission<br />
#119919<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 23
Fast Camera<br />
S<strong>in</strong>gle Frames<br />
3000fps<br />
#119916<br />
25 frames<br />
50 frames 500 frames<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 24
Droplets<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 25
Disruptions<br />
14 frames before 6 frames dur<strong>in</strong>g<br />
Droplets do not orig<strong>in</strong>ate from mesh dur<strong>in</strong>g disruption<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 26
Mass Loss <strong>in</strong> <strong>TEXTOR</strong><br />
Droplets sizes<br />
seem to be <strong>in</strong> the<br />
µm range <strong>in</strong> sized<br />
r=10µm--> 30ng<br />
Sn Mass<br />
available 2.12g<br />
Mass Loss:<br />
5.3159*10 -3 g<br />
~180000 Droplets<br />
Consistent <strong>with</strong> numbers<br />
extrapolated from fast CCD<br />
Mechanism not yet<br />
understood<br />
Differences <strong>PSI</strong>-2 – <strong>TEXTOR</strong> to be assessed:<br />
§ Plasma temperature / ion energies<br />
§ Carbon background <strong>in</strong> <strong>TEXTOR</strong> (coat<strong>in</strong>g of Sn surface)<br />
§ Magnetic field strength<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 27
Summary <strong>and</strong> outlook<br />
§ T<strong>in</strong> has been studied as <strong>liquid</strong> <strong>target</strong> material alternative to<br />
Lithium <strong>with</strong><strong>in</strong> the concept of a the capillary porous system.<br />
§ Tungsten has been found as optimum mesh material, wett<strong>in</strong>g<br />
improved under hydrogen atmosphere.<br />
§ Exposure <strong>in</strong> <strong>PSI</strong>-2: mass loss could not be expla<strong>in</strong>ed by<br />
physical sputter<strong>in</strong>g / evaporation – temperature enhanced<br />
sputter<strong>in</strong>g?<br />
§ Exposure <strong>in</strong> <strong>TEXTOR</strong>: mass loss dom<strong>in</strong>ated by strong droplet<br />
emission, mechanism unclear to date<br />
§ Next exposure <strong>in</strong> <strong>PSI</strong>-2: <strong>target</strong> bias<strong>in</strong>g to <strong>in</strong>crease ion energy<br />
to come close to <strong>TEXTOR</strong> conditions <strong>and</strong> to assess<br />
temperature enhanced erosion<br />
§ Next exposure <strong>in</strong> <strong>TEXTOR</strong>: position<strong>in</strong>g of <strong>target</strong>s <strong>in</strong> erosion<br />
dom<strong>in</strong>ated zone to prevent carbon deposition<br />
September 9th, 2013<br />
B. Unterberg | Institut für Energie- und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich Nr. 28
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