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).