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Seoul Nat’l Univ.Dept. of Nuclear Eng.
PlasmaApplicationLaboratoryICTP School
TDS Study of Effect of High Energy Ion induced Cascade Damage on Deuterium
Retention in Tungsten
Younggil Jin, Jae-Min Song, Ki-Baek Roh, Gon-Ho Kimjinjun77@snu.ac.kr
Plasma Application LaboratoryEnergy Systems Engineering, Seoul National University, Korea
July 18th, 2016
O4
2/18
Background: Enhanced Retention of W due to Ion Damages
Introduction
Fusion reactor shutdown condition: T Retention > Safety limit (700 g/yr).
T retention increase with damage (dpa) of Low energy fuel ion (D+, Ei < 100
eV), Energetic ion (W+, Be+, C+, Fe+ for ITER and DEMO, sub keV ~ MeV),
fusion product (He ash and n, E ~ 14.5 MeV).
Common Issue: Non-linearity b/w retention and dpa (damage level)
Scattered retention expectation and transition [1]
[1] J. Roth, PSI-18 Toledo, May 26, 2008[2] N. Fedorczak et al., Journal of Nuclear Materials 463 (2015) 85–90
Energetic ion (W+) eject flux in JET-ILW [2]
Safetylimit
Transition?
3/19
Research Topic and StrategyIntroduction
Retention mechanism
By Low energy fuel
ion
Change by Impurity chemical trapping
Change by Defect induced trapping
By self ion
Ion-induced Cascade damageduring operation
Impurity implantation during operation
Desorption due to thermal effect Decrease of
retention
Comprehensive understanding on
1) Retentionfor safety
2) Recycling for PSI analysis
Present topic
Cause of non-linearityIntrinsic retention
W Transmutation effect due to
neutronNeutron effect
4/19
Energetic Ion Irradiation Facility: HIT
Cs ion
FeO2-
FeO Target
FeO2-
Charge exchange gas
Grid : + 1.4 MV
Fe2+
Ion get max. 2.8 MeV : applied V x 2
Quadruple magnetic
lens
W specimen
[3] F. Hinterberger, et al., “Electrostatic accelerators”, Springer, (2005).
High fluence irradiation facility (HIT)In Tokyo University [3]
5/18
Cascade Ion Damage of Fe2+ and Similarity with W+Experiment
Facility: HIT in Tokyo Univ. Damage profile of Fe2+ and W+ (SRIM-2013)
Property ConditionSelf-ion simulate ion Fe2+ ion
Ion energy 2.8 MeV
Incident angle 75° (15° tilted)
Target temperature 300 K (spec.: ~ 873 K)
Damage range 0-0.7 dpa(spec.: dep. on time)
Comparison of cascade damage for heavy ion (Fe2+) to W ion.Property (Estimated by SRIM) 74 W ion (self ion) 26 Fe ion (HIT) Capability of demonstration
Damage(∝dpa)
(1) Target displacement 70959/W Ion 39948/Fe Ion Adjustable by 1.776 times fluence
(2) Target vacancy 60361/W Ion 34079/Fe Ion Adjustable by 1.776 times fluence
Displacement per vacancy generation ratio (=(1)/(2)) 1.175 1.172 (≒ W)
Unadjustable (Intrinsic): it decide TDS spectrum shape Essential for demonstration
(a) 2.8 MeV W ion, 75° (b) 2.8 MeV Fe ion 75°
This research can show representative effect of cascade damage using energetic ion, and then it gives insight to expect tungsten self ion effect.
6/18
Fe2+ Ion Irradiation Condition
TC 1
TC 20 4000 8000 12000 16000
262728293031323334
Tem
p [o
C ]
Time [sec]
Target 1 TC1 Target 1 TC2 Target 2 TC1 Target 2 TC2 Target 3 TC1 Target 3 TC2
0 sec
0 2 4 6 8 10 12 14 160
2
4
6
8
10
12
Y di
rect
ion
[mm
]
X direction [mm]
-4.000E-112.462E-105.325E-108.187E-101.105E-091.391E-091.677E-091.964E-092.250E-09
0 2 4 6 8 10 12 14 160
2
4
6
8
10
12
Y di
rect
ion
[mm
]
X direction [mm]
-2.000E-112.800E-105.800E-108.800E-101.180E-091.480E-091.780E-092.080E-092.380E-09
Target size
1800 secFe2+ Ion current
Irradiation holder structure Target temperature during irradiation
7/18
Calculation of Cascade Ion Damage: dpa
#of vacanyDefinition of dpa : # target atom
dpa =
8
o
#of vacancy 10 #of vacanyTrim results : a =# of incident ion # of incident ion cm
⋅=
⋅ Α ⋅
# of incident ion : fluence = ion flux time⋅
( )9
22
Farad. cup current [10 ]ion flux = / incident ion charge number : ex. FeFarad. cup surface area [cm ]
A−+
2 6 2Farad. cup surface area : 3.14 104
D mπ −= ⋅
322 3density [g/cm ]Atomic density of target : 6.3 10 #/
molar mass [g/atom]cm= ⋅
Variables
Setting values
8 3
4 2
a ion flux /atomic density of target 10 # of vacancy # of incident ion # of vacancy= / sec
# of incident ion cm # of atom in target # of atom in target sec10 seccm dpa
cm
⋅
⋅⋅ ⋅ = =
⋅ ⋅⋅ ⋅
8/15
Spatial Distribution Analysis of Implanted FeAnalysis
Analysis tool: SIMS
Bi
Cs
Detector
Measuring spot and systematic error
• Sputter beam Cs (sputtering), Bi (monolayer etch)
• Detector: QMS
• Operating pressure (~10-7 Torr)
• Specimen size: up to 10 x 10 mm2
• Sputtering area: 150 x 150 μm2
• Detecting area: 40 x 40 μm2
minimize sputtering uniformity error
• Resolution: 0.5-1 nm/sec
• Sputter depth calibration: α-stepper
• Cause of Systematic Error: Beam current
variance during sputtering (53 ~ 55 pA,
~3.6 %) Error in depth axis (for 1nm, 0.3 Å)
Sputtering (Cs)
Sputtering (Cs)Detecting (Bi)
Detecting (Bi)
Sputtered depth
9/18
Change of Energetic Ion Cascade Damaged W SurfaceResult
Indirect confirmation of dpa increase: Implanted Fe w/ dpa in W Measured by secondary ion mass spectroscopy (SIMS)
Fe Fe fraction in W, C Fe Fe
W W
RSF IRSF I
=
RSF for Fe ~ 1.7 x 1025 [4]RSF for W ~ 6.5 x 1024 [4]IFe: SIMS intensity of FeIW: SIMS intensity of W
0 100 200 300 400 500 600 700 80010-2
10-1
100
101
0 100 200 300 400 500 600 700 80010-2
10-1
100
101
0 100 200 300 400 500 600 700 80010-2
10-1
100
101
0 100 200 300 400 500 600 700 80010-2
10-1
100
101
Fe fr
actio
n in
W, C
Fe
Depth (nm)
0.01 dpa 0.5 dpa 0.2 dpa 0.7 dpa
[4] R. G. Wilson, Int. J. Mass Spectrom. Ion Processes, I43, 43-49 (1995).
0.0 dpa (Pristine)
0.01 dpa 0.05 dpa 0.2 dpa 0.7 dpa
FESEM
FESEM FESEM FESEM FESEM
# of Fe is indirect evidence of induced dpa
Approximately no damage
Severe damage
∝ dpa
10/18
Demonstration of Fuel Ion Retention on Ion Damaged WExperiment
SNU-TDS: Analysis Objective: desorption energy (Edes) analysis to identify defect using Tp of thermal desorption spectroscopy (TDS)
SNU-ECR: Demonstration
Property ConditionBase pressure ~10-7 Torr
TDS range 300-1273 K
Ramp rate 20 K/min (spec.:10-60 K/min)
RGA (QMS) resolution 0.1-1 amu
Analysis theory Readhead approximation(Error < 1.5% for 108 < ν1/β < 1013 K-1)
Property ConditionSource type Electron cyclotron resonance plasma
Ion energy 100 eV/D2+ (spec.: 0-300 eV)
(Target biased sheath potential)
Ion flux ~2.8 x 1021 D2+/m2-s
Target temperature 700-800 K (Active cooling)
Ion fluence ~4.0x1025 D/m2 (spec.: 1024 -1026 D/m2)
Objective: Simulate T retention using D ion (D2+)
irradiation to investigate fuel ion induced retention.
11/18
TDS Analysis: Identification of Defect Type
1ln 3.64Md P
vTE RTβ
∆ = −
Redhead approximationExpect Tp in TDS spectrum for certain defect-H trapping desorption energy (Ed) with unity set of TDS experiment.
(Error is less than 1.5% for 108 < ν1/β < 1013 K-1 [5]where ν1: Debye frequency = 1013 s-1, β: ramp rate [K/min)
[5] Dirk Rosenthal , Electronic Structure, Department of Inorganic Chemistry, Fritz-Haber-Institut der MPG, Berlin, Germany
0 10 20 30 40 50 60 70 80 900
1x1013
2x1013
3x1013
4x1013
5x1013
6x1013
7x1013
8x1013
v 1/β (Κ
-1)
TDS Ramp rate (K/min)
Readhead approximation zone
IAEA CRP recommend ramp rate (10-60 K/min)
10 15 20 25 30 35 40400
440
480
520
560
600
640
680
720
760
T p of R
edhe
ad A
ppro
xim
atio
n (K
)
TDS Ramp rate (K/min)
Ion-induced vacancy (Ed=1.43eV) Neutron-induced cluster (Ed=1.85eV)
12/18
TDS Spectrum Variation of Ion Cascade Damaged WResult
Dislocation Vacancy Cluster
0
1x1016
2x1016
3x1016
4x1016
0
1x1016
2x1016
3x1016
4x1016
0
1x1016
2x1016
3x1016
4x1016
0
1x1016
2x1016
3x1016
4x1016
300 400 500 600 700 800 9000
1x1016
2x1016
3x1016
4x1016
Des
orpt
ion
flux
[D2/m
2 -s]
Temperature (K)
0 dpa
0.01 dpa
0.05 dpa
0.2 dpa
0.7 dpa
dpa TDS peak and dominant trapping
400-500 K D-dislocationtrap (Edes=0.75-0.95 eV)
580-680 K D-vacancy trap (Edes1.83 eV)
710-810 K D- cluster trap (Edes=2.34 eV)
0.00 O (461 K) O (638 K): dominant X
0.01 O (490 K) O (581 K, 666 K) O (800 K)
0.05 O (473 K) O (624 K, 730 K) O (810 K)
0.20 O (390 K, 488 K, 527 K): dominant
X O (799 K)
0.70 O (394 K, 482 K, 572 K): dominat
X O (808 K)
Variation: Dominant vacancy Dominant dislocation
The variation defined by peak analysis:Theoretical and Literature value of TDS peak
Edes [eV] Es [eV] TP (Error range) [K]0.75-0.95 0.35-55 (dislocation) 350-550 K, Literature [6]
1.83 1.43 (vacancy) [7, 8] 616 (566-666), Theory
2.34 1.94 (vacancy cluster) [9] 796 (746-846), Theory
[6] H. Fujita et al., Phys. Scr. T167 (2016) 014068[7] D. F. Johnson et al., J. Mater. Res., Vol. 25, No. 2, Feb 2010[8] K. Heinola et al., Physical Review B 82, 094102 2010 [9] Ogorodnikova, Roth, and Mayer, J. Appl. Phys. 103, 034902 2008
Fuel ion only retention
+ Cascade damaged
13/18
Retention Property under Low Ei Fuel Ion Only (~0 dpa) [10]
Result
0.0
2.0x1018
4.0x1018
6.0x1018
8.0x1018
1.0x1019
300 400 500 600 700 800 900 1000 1100 12000.0
2.0x1018
4.0x1018
6.0x1018
8.0x1018
1.0x1019
Des
orpt
ion
flux
(D2/m
2 -s)
Temperature (K)
TDS measurement for 2.0 x 1025 D/m2
Fit Peak 1 at 452 K Fit Peak 2 at 670 K Cumulative Fit Peak
Des
orpt
ion
flux
(D2/m
2 -s)
Temperature (K)
TDS measurement for 4.0 x 1025 D/m2
Fit Peak 1 at 455 K Fit Peak 2 at 680 K Cumulative Fit Peak
1. Mechanism for retention under fuel ion only = vacancy trapping (Eb=1.43 eV)
Fluence dependence of vacancy trapping(Plotted with TDS peak deconvolution)
Change: from solution to vacancy trapping
Vacancy trapping dominates retention after the
fluence over 2.0 x 1025 D/m2 with Eb=1.43 eV.
Es=0.89 eV Es=1.43 eVEdes=0.89 eV Edes=1.83 eV
300 400 500 600 700 800 900 1000 1100 12000.0
2.0x1018
4.0x1018
6.0x1018
8.0x1018
1.0x1019
Des
orpt
ion
flux
(D2/m
2 -s)
Temperature (K)
0.5x1025D/m2 (No peak) 2.0x1025D/m2 Gaussian fit (462 K) 4.0x1025D/m2 Gaussian fit (676 K)
D Solution in W Vacancy trapping
[10] Y. Jin et al., Journal of Korean Physical Society, 2016
Occur of vacancy
Dominant vacancy
14/18
Retention Property under Low Ei Fuel Ion Only (~0 dpa) [10]
Result
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 1000.00
0.01
0.02
0.03
0.04
0.05 SIMS measurement Gaussian fit
D c
once
ntra
tion
in W
Depth (nm)
10-3
10-2
10-1
100
10-3
10-2
10-1
100
1 10 100 1000
10-3
10-2
10-1
100
D c
once
ntra
tion
in W
, CD (f
ract
ion)
Ion fluence=0.5 x 1025 D/m2
D concentration in W
Ion fluence=2.0 x 1025 D/m2
concentration
Ion fluence=4.0 x 1025 D/m2
D concentration in W
Depth (nm)
100
101
102
103
100
101
102
103
1 10 100 1000
100
101
102
103
Ion fluence=0.5 x 1025 D/m2
D W
SIM
S in
tens
ity, I
(cou
nts/
sec)
Ion fluence=2.0 x 1025 D/m2
D W
Ion fluence=4.0 x 1025 D/m2
D W
Depth (nm)
Peak
Peak
Peak
Peak
(a)
(b)
(c)
(d)
(e)
(f)
2. Cause of variation: Deuterium Oversaturation in Tungsten Saturation property for given PSI condition limited formation of vacancy in nm scale.
D concentration measurement by SIMS: peak = oversaturation Gaussian fit to determine depth
Oversaturation depth
0 1 2 3 40
2
4
6
8
10
12
14
16
18
20
Ove
rsat
urat
ion
dept
h (n
m)
D ion fluence (D2+/m2)
Asymptotic line
Saturated
[10] Y. Jin et al., Journal of Korean Physical Society, 2016
15/18
Transition of Retention by Energetic Ion Cascade Damage (>0.01 dpa)
Result
0 dpa 0.01 dpa 0.05 dpa 0.2 dpa 0.7 dpa0.0
4.0x1018
8.0x1018
1.2x1019
1.6x1019
2.0x1019
2.4x1019
2.8x1019
3.2x1019
Ret
entio
n am
ount
(D/m
2 )
dpa
Dislocation (Eb=0.75-0.95 eV) Vacancy (Eb=1.43eV) Cluster (Eb=2.34 eV) Total
3. Cascade damagedominated
1. Oversaturationdominated
Transition of dominant defect trapping
TDS peak integration = retention amount of each peak
Oversaturation induced vacancy (Eb=1.43 eV) due to Fuel ion
Ion cascade damage induced main dislocation (Eb=0.85 eV) + minor cluster (Eb=2.34 eV)due to self-ion
2. Transition
Dislocation Vacancy Cluster
0
1x1016
2x1016
3x1016
4x1016
0
1x1016
2x1016
3x1016
4x1016
0
1x1016
2x1016
3x1016
4x1016
0
1x1016
2x1016
3x1016
4x1016
300 400 500 600 700 800 9000
1x1016
2x1016
3x1016
4x1016
Des
orpt
ion
flux
[D2/m
2 -s]
Temperature (K)
0 dpa
0.01 dpa
0.05 dpa
0.2 dpa
0.7 dpa
Fuel ion only retention
+ Cascade damaged
16/18
Mechanism of Defect Transition (vacancy↓, dislocation↑)
Discussion
1. Generation fraction: dislocation > vacancy [12] Vacancy aggregates explains,
Pathway of vacancy cluster(pore or cavity) accompanyingreduction of vacancy population.
Free SIAs interstitial loop Dislocation, Vacancy aggregates cavity (cluster)
2. Vacancy aggregation [13]
Formation of dislocation loopreduces dislocation recovery
[12] A. E. Sand et al., EPL, 103 (2013) 46003[13] A. J. E. Foreman and B. N. Singh, Radiation Effects and Defects in Solids, 1990, 113, 175-19.1
17/18
Quantitative Effect of Ion Cascade Damage on RetentionDiscussion
Retention enhancement factor [11]
[11] Yasuhisa Oya et al., Phys. Scr. T145 (2011) 014050 (5pp)
Damage [dpa] Total Retention[D/m2]
Retention enhancement factor [1]
Retention phase
0.00 6.74E18 1 Deuterium oversaturationdominated
0.01 5.75E18 0.853 (85.3%), Transition(Steep increase of retention)0.05 1.96E19 2.91 (291%)
0.20 2.20E19 3.26 (326%) Ion cascade damage dominated(Steady increase of retention)0.70 2.50E19 3.71 (371%)
-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
1x1019
2x1019
3x1019
4x1019
5x1019
dpa
Tota
l ret
entio
n (D
2/m
2)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Ret
entio
n en
hanc
emen
t fac
tor
Similarcondition
Increase of retention with dpa (Fe damage)
0.05 dpa
0.01 dpa
18/18
Summary and Conclusion
By using 2.8 MeV Fe2+ irradiation, Ion cascade damage effect on D
retention of W have been investigated as 3 phase.
Phase. 1 Oversaturation dominated retention (0-0.01 dpa).
1. Fuel ion oversaturation dominates retention with vacancy trap (Eb=1.43 eV)
2. Oversaturation saturates at certain depth. cause of transition
Phase. 2 Transition (0.01-0.05 dpa)
1. Occur when # of dislocation > # vacancy because oversaturation has
saturation property while dislocation can increase with dpa.
2. Defect transition: due to dislocation loop formation, vacancy aggregation.
Phase. 3 Energetic Ion cascade damage dominated retention (> 0.05 dpa).
1. Self ion induced cascade collisional damage increase retention steadily.
2. Dislocation trapping (Eb=1.84 eV), vacancy cluster trapping (Eb=2.34 eV).
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