1. Tungsten Armor Engineering:
Debris Ions and He-Bubbles
Carbon Implantation
Roughening Mechanisms
Shahram Sharafat, Nasr Ghoniem, Qiyang Hu, Jaafar El-Awady, Sauvik Benarjee, and Michael Andersen
University of California Los Angeles, CA.
11th High Average Power Laser Program Workshop Lawrence Livermore National Laboratory Livermore, CA June 20-21, 2005

2. Debris Ions and Helium Bubbles Carbon Implantation
TOPIC
Debris Ions and Helium Bubbles
Carbon Implantation
Roughening Mechanisms

3. Debris Ions and He-Bubbles
HAPL W-Armor Exposure:
Ions - He plus P, D, T, C, Au, and Pt
He-Implantation Experiments:
Ions - He plus D, P (planned)
Do we need to consider these in He implantation experiments ?
- How much damage do they cause ? - What is their effect on He-bubbles ? - Do we need to modify experiments ?
Use the HEROS code to investigate

4. Density Profiles (SRIM)
DEBRIS-IONS

5. Low- and High Yield Target Debris- and Burn Ions*
Ions per Shot
Significant** Energy Range (keV)
Implantation Range (um)
Vacancies / Ion
154 MJ
401 MJ
DEBRIS: (pulse ~2x10-6s)
He3
51017
21018
40-400
70-700
0.2 – 0.8 70
He4
41019
11020
80-550
0.4 – 1.8 87 H
91018
2 1018
11 – 220
36 – 240
0.2 – 1.0 7 D
61020
1 1021
30 – 300
50 – 460 25 T
50 – 400
70 – 680
0.2 – 2.0 52
C12
11019
2 1019
200 – 1500
1550 Au
11017
1 1017
11,000 – 24,000
13,000 – 20,000
0.8 – 1.8
89,300
BURN: (pulse ~8x10-7s)
61016
31017
200–3600
0.5 – 1.6
117
700 – 3600
1.0 – 10
149
6 1018
600 – 3000
200 – 3600
3 – 27 34
5 1019
700 – 13,000
90 – 9000
3 – 180
280 – 3600
1 – 70
102
* Based on THREAT SPECTRA; **Based on largest percentage of ions

6. Self-Damage (Defect) Rate Profiles (SRIM)

7. Comparison of Damage Rates

8. HEROS: Damage and Implantation Profiles
SRIM Profiles
HEROS Input Profiles
Implantation Density:
Burn
Temperature Rise
Implantation Debris (apa/s)
Ion Self-Damage:
Damage
Debris (dpa/s)
Burn

9. HEROS: Bubble Concentration including Debris Damage
Temperature Rise: 2200 oC
Chamber Radius: 10.1 m
2 Consecutive Shots (5Hz)
Bubble Concentration in W (#/cm3)
Green  Annealing Temp. Drop
Red  Implantation
2 Consecutive Shots

10. Bubble Concentration Including Debris Damage
Burn
T=10-10sec
T=10-8sec
T=0.4sec
T=0.7sec
Debris
Effect of D, T, C, & Au Simultaneous Self-Damage)
Annealing
T=0.8sec
T=1.5sec
T=2.1sec
T=0.8msec
High Temperature Annealing
End of Implantation
Annealing
Burn-2nd Pulse
Debris- 2nd Pulse
Annealing-2nd Pulse
T=0.2s+0.7s
T=0.2sec
T=0.2s +2.1s
T=0.4sec
End of Pulse Two
End of Pulse One
End of Burn of Pulse Two
End of Debris of Pulse Two

11. Importance of Simultaneous Debris-Ion Damage
Large displacement damage is caused by Debris Ions (C, Au, P, D, T , Pt)
Factor of 10 X He-Self Damage
Results in SUPERSATURATION of vacancies
Supersaturation of vacancies provides larger number of He-trap sites
Poster by Q. Hu on He-Modeling
Schematic of He-Bubble Resolution
High Debris-Ion Damage Rates:
Momentum transfer of Excess Interstitials
Collisional Displacement of He from bubbles: Bubble RE-SOLUTION
Increases effective DHe coef.
Rapid temperature rise (2200 oC) facilitates annealing of He-Vac-Clusters and small Bubbles.
Combination of high debris ion damage plus high temperature rise significantly enhances Helium-recycling
Collision Cascade (SIA)
Helium Bubble
Self- Interstitial W-atom
Produced by Debris (PKA)
Smaller Helium Bubble decorated with He-Vacancy Clusters

12. Debris Ions and Helium Bubbles
TOPIC
Debris Ions and Helium Bubbles
Carbon Implantation: Mechanical Properties Helium Retention Tritium Retention
Roughening Mechanisms

13. Debris Carbon Implantation Profile (SRIM 2003)
Assuming No Carbon Diffusion (154 MJ Target):

14. Debris Carbon Implantation Profile (SRIM 2003)
Assuming COMPLETE Carbon Diffusion (5 Hz; 154 MJ Target):
This slide was not shown

15. Debris Carbon Implantation Profile (SRIM 2003)
Assuming COMPLETE Carbon Diffusion (10 Hz; 154 MJ Target):
This slide was not shown

16. This slide was not shown
Temperatures
Slide from Jake’s Presentation: HAPL NRL 2005
Additions/Modifications appear in RED
Carbon arrives (max implantation depth ~1 um)
154 MJ
7 m
250 microns tungsten
3 mm steel
This slide was not shown

17. Impact of WC-Layer: Thermo-Mechanical Props.
Above 940 oC various W-C compounds can form depending on temperature and molar ratios.
Thermo-Mechanical Impact:
WC & W2C Tmelting ~2800 oC
Tm of WC ~600 oC less than W
WC is a ceramic more brittle
WC effects crack behavior
Low Temp. Metal Fracture Toughness (MPa√m)
Aluminum alloy 36
Steel alloy 50
Titanium alloy
44-66
Tungsten
10-15
Ceramics (Bulk)
Aluminum oxide
3-5.3
Soda-lime-glass WC
4-7
Demetriou, Ghoniem, Lavine, Acta Materialia. (2002)

18. Impact of WC-Layer: Helium Release
Could not find helium release data for WC.
At elevated temperatures He retention in SiC and B4C is low (implanted He: E=5 keV; He=1e18 /m2-s; Temp: RT; Hino-JNM-1999).
U-Pu-Oxide fuels show significant fission product (gas) migration.
Migration of Helium bubbles through WC needs to be verified experimentally.
T. Hino, JNM (1999)
Inoue, JNM (2004)

19. Impact of Carbon Implantation: Tritium Retention
High T implantation: ~2x1017 T/m2 per shot for a R=10.1 m chamber.
Effects of Carbon on T retention at High Temperatures?
Irradiated tungsten at 653K with carbon concentration as a parameter (1 keV ~7× 1024 H/m2 [Ueda,2004].

20. Debris Ions and Helium Bubbles Carbon Implantation
TOPIC
Debris Ions and Helium Bubbles
Carbon Implantation
Roughening: Failure Mechanisms Effect of Hydrogen

21. Surface Cracks in Polycrystalline Tungsten
TOPICS
Roughening induced Failure Mechanisms
Surface Cracks in Polycrystalline Tungsten
Steel Substrate
W-Armor
1. Surface cracks can penetrate to the interface and turn
2. Low Cycle fatigue initiates cracks
at the interface (weaker intermetallic W16Fe)
Margevicius, 1999
Poster by J.El-Ewady on Bond-Strength Measurements

22. Roughening Mechanisms: Effect of Hydrogen
About 4x1017 (T+D)/m2 per shot for a 10.1 m chamber
Experimental Setup of CVD Tungsten on Copper
Cyclic heat load tests with a hydrogen beam and a comparable electron beam on CVD-tungsten.
Hydrogen surface damage more severe than that by the electron beam.
Cracked surface at all temperatures from 300 C to 1600 C.
H-Irradiation Conditions
Tamura, JNM, 2005
HAPL: 3000 shots (10 min)

23. Effect of Hydrogen at 1600oC
TOPICS
Effect of Hydrogen at 1600oC
Tamura, JNM, 2005
Surface morphology of the CVD Tungsten: 110 shots with a peak temperatures of 1600 C. Small pores are observed at the coating surface (b) after hydrogen beam irradiation.

24. Summary and Conclusions
DEBRIS ION Self-DAMAGE:
C-, Au-, and Pt Debris ions cause large damage within the first 2-um.
Large damage assists in “RE-SOUTION” of helium bubbles:
- Facilitates efficient He-recycling.
A high helium He-Recycling coefficient may be attainable.
Needs experimental verification ?
CARBON:
Implantation of C into W is significant: Localized C/ W > 1 in a few days
Effects on mechanical performance of W-armor needs investigation.
Effect of Carbon on P-, D-, and T retention has not been addressed.
May be critical for W-armor reliability.
ROUGHENING •Mechanism of armor failure as it relates to roughening will be experimentally determined and theoretically modeled • Role of hydrogen implantation on surface cracking needs consideration.