Transcript Snead - Advanced Energy Technology Program

Review of ORNL Collaborative Materials Development Work
in Support of the High Average Power Laser Program
In FY-07 Work has been in five general areas:
• Installation of Pulsed Electron Thermofatigue System (ORNL, Duty Talk)
• Continuation of Tungsten Armored Ferritic thermal stability (Romanoski-ORNL)
• Implanted Ion Effects (Parikh-UNC, Romanoski-ORNL, Sharafat-UCLA)
• Thermal Fatigue Testing of Tungsten Armored Ferritic (Snead-ORNL)
• Irradiation of Dielectric Mirrors (Leonard-ORNL, Lahecka-PSU, Parikh-UNC)
• Advanced Concepts Materials (Snead-ORNL, Sawan, et al. U. Wisc.)
Presented at the October 30-31 HAPL Review Meeting
by Lance Snead
Oak Ridge National Laboratory
1
Managed by UT-Battelle
for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
Irradiation Effects on
Dielectric Mirrors
Keith Leonard, Lance Snead, and Joel McDuffee, ORNL
Tom Lahecka, PSU
• Background of work
• He implantation
• Neutron irradiation
• Future work
Summary of work coordinated by Lance Snead and presented at the October 30,31 High Average Powered Laser
Program Review meeting at the Naval Research Laboratory, Washington D.C.
2
Managed by UT-Battelle
for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
Background
The use of dielectric mirrors offer significantly improved transmission of reflected
electromagnetic energy. However, earlier work shows differing opinions as to the use
of dielectric mirrors in nuclear environments.
E.H. Farnum et al. (1995)
• HfO2/SiO2, ZrO2/SiO2, and TiO2/SiO2 mirrors on SiO2 substrates.
• Neutron fluence: 1019 n/cm2, 270-300ºC.
• Excessive damage in HfO2/SiO2 and ZrO2/SiO2 mirrors, including flaking and crazing of films.
K. Vukolov(2005)
• TiO2/SiO2, ZrO2/SiO2 mirrors on KS-4V silica glass.
• Neutron fluence: up to 1019 n/cm2, 275 ºC.
• Dielectric mirrors showed no significant damage.
Outcomes and recommendations of their work
• Fewer and thinner bi-layers improve resistance to environmental effects (thermal cycling and
radiation tolerance).
• Poor performance from SiO2 substrates; suggested use of more damage resistant
substrates: Al2O3 or MgAl2O4.
• Damage resistance is sensitive to fabrication techniques / conditions.
3
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HAPL Meeting Oct 30 -31st, 2007
Mirror Requirements
• Reflectivity: > 99.8% at 248 nm, (99.5% from 238 to 258 nm)
• Absorption: < 500 ppm measured at 248 nm
• Scattering: total integrated scattering < 500 ppm at 633 nm
• Laser Damage Threshold: ~10 J/cm2 at 248 nm, 2 ns FWHM pulse
• Total neutron flux to mirror: ~1x1013 n/cm2s (first mirror) , ~1x1011n/cm2s (final)
- Total neutron fluence in IFE in one year, assuming 80 % plant availability =
2.5x1018 n/cm2 (final mirror) to 2.5x1020 n/cm2 (first mirror) –estimates based
on earlier work by M. Sawan.
• Total g dose rate to mirror: ~3x1012 p/cm2s (first mirror), ~6x1010 p/cm2s (final)
4
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HAPL Meeting Oct 30 -31st, 2007
Environment Issues and Evaluation Techniques
• Differences in radiation and thermally induced swelling or contraction
of the film layers or strain buildup between the first layers and
substrate (visual inspection, ellipsometry).
• Changes in surface roughness (AFM).
• Irradiation / thermally induced structural changes within a given layer
(microscopy, x-ray, ellipsometry).
• Irradiation / thermally induced mixing or formation of interlayer
compounds (microscopy, x-ray).
• Reduction in peak reflectivity and shift towards lower wavelengths
(spectrophotometry).
• Changes in optical absorption due to radiation induced defects
(spectrophotometry).
5
Managed by UT-Battelle
for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
HAPL Dielectric Mirror Samples
• Test samples consisted of 3 dielectric mirror designs (> 99.8% reflectivity at
248 nm) along with monolayer films to evaluate film / substrate interactions.
• Higher damage tolerant sapphire substrates used instead of SiO2.
• Films deposited by electron beam with ion-assist; Spectrum Thin Films, Inc.
Sample
6
Quantity
Film Thickness / Description
Sapphire substrates only
18
6 mm diameter x 2 mm thickness
Al2O3 monolayer on sapphire
18
¼ l thickness (36 nm)
SiO2 monolayer on sapphire
18
¼ l thickness (40 nm)
HfO2 monolayer on sapphire
18
¼ l thickness (27 nm)
Al2O3 / SiO2 mirror on sapphire
18
26 Bi-layers, 2036 nm total thickness
Al2O3 / HfO2 mirror on sapphire
18
14 Bi-layers, 924 nm total thickness
HfO2 / SiO2 mirror on sapphire
18
11 Bi-layers, 768 nm total thickness
Managed by UT-Battelle
for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
HAPL Dielectric Mirror Irradiations
Ion implantation
• Monolayer and substrate only samples
• Examine tolerance of film / substrate prior to neutron radiation
experiments.
• Performed by Nalin Parikh and Shon Gilliam, UNC-Chapel Hill.
Neutron irradiation
• Substrate, monolayer and mirror samples
• Examine changes in optical properties of mirrors
• Irradiations performed at the High Flux Isotope Reactor (HFIR)
at ORNL.
7
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for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
Ion Implantation
Monolayer and substrate
only samples
Conditions
• 10 keV He ions at 0º tilt, and room temperature
• Implanted doses of 1018, 1019, 1020 and 1021 He/m2
• Use of a implantation mask to maximize sample usage
SiO2 monolayer on Sapphire
SRIM calculations: implantation doses
produce between 0.001 to 1 dpa of
8damage
Managed byat
UT-Battelle
the film / substrate interface.
for the Department of Energy
6 m
HAPL Meeting Oct 30 -31st, 2007
Ion Implantation
• General inspection of films by optical and SEM:
 No
signs of delamination or blistering.
• A slight optical “graying” observed in the
1021 He/m2 implanted HfO2 monolayer sample.
 May
represent a significant loss of in
transmission at 248 nm λ.
• Atomic Force Microscopy (AFM) data.
 No
changes in surface roughness between
implanted and non-implanted regions for all
samples / conditions.
•
Possible future work: ellipsometry in
determining changes in film properties
following ion implantation.
9
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HAPL Meeting Oct 30 -31st, 2007
Monolayer and substrate
only samples
Neutron Irradiation of 15 HAPL Capsules
• All samples tested: mirror, monolayer and substrate only samples.
• HFIR irradiations at 1018, 1019 and 1020 n/cm2, at 300ºC, samples sealed in He.
• Required the design of specialized holders to prevent the scratching of the
optical surfaces. Samples are held only at the edges.
10 Managed by UT-Battelle
for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
Neutron Irradiation
• Three samples from each mirror, monolayer and substrate irradiated in the HFIR core
to 1018, 1019 and 1020 n/cm2 (fast.)
• One order higher than Farnum, Two orders higher than Vukulov
• IFE Final Mirror 2.5 x 1018, IFE Final Mirror 2.5 x 1020
• Calculated mirror temperature 280 and 307ºC (comparable to Farnum/Vukolov work).
• Holders contain SiC thermometry for temperature measurement – to be determined.
Temperature
distribution
Sample
Holder
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for the Department of Energy
Cross-section of holder with sample
HAPL Meeting Oct 30 -31st, 2007
Neutron Irradiation
The LAMDA Laboratories allow for the examination of low
• The irradiated capsules were
activation materials without the need for remote
disassembled in the Low Activation
manipulation (~4500 sq ft. and over 30 different
Materials Design and Analysis (LAMDA) characterization tools).
Laboratory.
• Capsule doses were between 4 and 450
mrem/h @ contact (0.5 to 18 mrem/h at
30 cm) depending on the irradiated dose
and sample type.
• Capsules were disassembled with
remaining FY-07 funds, post-irradiation
examination has been limited in the FY.
12 Managed by UT-Battelle
for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
Neutron Irradiation
• Samples removed from aluminum holders;
visually inspected.
• Changes in (sapphire substrate) color
observed with increasing neutron exposure.

Non-irradiated controls are all clear to visible
light.

Highest dose samples nearly opaque to visible
light.
• All surfaces remain visibly smooth with no
visible signs of cracking or delamination.
• Examples of the HfO2 / SiO2 mirrors are
shown at right, all samples are similar.
13 Managed by UT-Battelle
for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
Future Work: Post Irradiation Examination
Center for Advanced Thin-Film
Solar Cells (CATS) Laboratory
• Newly constructed facility at ORNL
• Now completed and in operation
Available Instrumentation
• Spectroscopic and transmission 2modulator generalized ellipsometers
• characterize thin film thickness changes
• strain fields between films and substrate
• Perkin-Elmer Lambda Spectrophotometer
• 180 to 300 nm wavelength
• Integrating sphere (specular and nonspecular reflectance and transmission)
• Veeco DekTak Profilometer
C A T S
Center for
Advanced
Thin-Film
Solar Cells
14 Managed by UT-Battelle
for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
Future Work: Post Irradiation Examination
Thermal Cycling:
• Tests on control materials to evaluate stability of films and optical degradation
following exposure to thermal cycling conditions.
Film-Structural Characterization:
• Cross-sectional transmission electron microscopy of irradiated mirrors.
Evaluate the stability or damage sensitivity of the film layers in the dielectric
mirrors, interfacial reactions, etc.
Substrate-Structural Characterization and Temperature Monitors:
• Density change of substrate to be measured and SiC temperature monitors to
be processed to determine irradiation temperature.
Laser Damage Threshold Testing:
• Further collaboration with T. Lehecka, Penn State Electro-Optics Center.
• Perform initial testing on unirradiated controls, followed by irradiated samples
15 Managed by UT-Battelle
for the Department of Energy
HAPL Meeting Oct 30 -31st, 2007
Helium Retention in nano-Porous Tungsten Implanted with
Helium Threat Spectrum Mimicking IFE Reactor Conditions
R. Parker, (R. Scelle), (S. Gilliam), and N. R. Parikh
University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255
R. G. Downing
National Institute of Standards and Technology,
Gaithersburg, MD 20899-3460
Scott O’Dell
Plasma Processes, Inc., 4914 Moores Mill Rd., Huntsville, AL 35811
G. Romanoski, T. Watkins, L. Snead
QuickTi me™ and a
T IFF (Uncom pressed) decom pressor
are needed to see t his pict ure.
Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6138, USA
•Summary of work coordinated by Nalin Parikh (UNC) and presented by Lance Snead at the October 30,31 High Average Powered
Laser Program Review meeting at the Naval Research Laboratory, Washington D.C.
Outline of the Talk
•
•
•
•
•
•
•
•
Introduction – IFE conditions & He threat spectrum
Objective – Minimizing He retention
Experimental facilities – UNC-CH / NIST
Previous results – 1.3 MeV 3He implantation
He threat spectrum implantation (100 – 500 keV)
Helium retention results of nano-HfC W samples
Carbon implantation in W to form W2C
Ongoing and Proposed Research
OBJECTIVE
• Implant IFE helium threat spectrum in nano-porous HfC-W
and study helium retention while mimicking IFE conditions.
• C+ Implantation in W to Form W2C and Study 3He Diffusion
Through W2C layer.
Engineered Tungsten Armor Development
•
Vacuum Plasma Spray (VPS) forming
techniques are being used to
produce engineered tungsten armor.
•
The engineered tungsten is
comprised of a primary tungsten
undercoat and a nanoporous
tungsten topcoat.
•
•
Nanometer tungsten feedstock powder
is being used to produce
the nanoporous tungsten topcoat.
The resulting nanoporous topcoat
allows helium migration to the
surface preventing premature failure.
Nanoporous W Topcoat
Primary W Layer
Low Activation
Ferritic Steel
Schematic showing the VPSing of the engineered W armor.
SEM image showing
nanometer W feedstock
powder produced by
thermal plasma processing.
Analysis has shown the
average particle size is less
than 100nm. This is one of
two nanometer W feedstock
materials used to produce
the nanoporous topcoat.
Engineered Tungsten Samples for Helium Implantation
Experiments at UNC
• To evaluate the effectiveness of the nanoporous W topcoat to prevent helium
entrapment, engineered W deposits were produced with and without the
nanoporous W topcoat.
• For the samples without the nanoporous topcoat, two different micron size
feedstock powders (-45/+20µm and -20/+15µm) were used to produce the
primary W layer.
• For the samples with the nanoporous topcoat, two different nanometer size
feedstock powders (500 nm and 100 nm) were used.
• HfC additions were made to the nanometer W feedstock powders to pin the
grains and prevent grain growth.
ID
Number
V2-06-349
V2-06-355
V2-06-443
V2-06-450
Feedstock Powders Used to Produce the Engineered W Armor
Primary W Layer
Nanoporous W Topcoat
W(-45/+20µm)
None
Thickness: ~0.6mm
W(-20/+15µm)
None
Thickness: ~0.6mm
W(-45/+20µm)
W(100nm) - HfC
Thickness: ~0.5mm
Thickness: ~75µm
W(-45/+20µm)
W(500nm) - HfC
Thickness: ~0.5mm
Thickness: ~50µm
No. of
Samples
8
8
8
8
Experimental Facilities
UNC – Chapel Hill, NC
• 2.5 MV Van de Graaff accelerator
3He implantation and helium retention measurements by nuclear reaction
analysis (NRA) technique
• 200 kV Eaton Ion Implanter NV-3204
High fluence C+ implantation to study WCx formation
High fluence He+ implantation to study sputtering
Irradiation Damage study of multilayer dielectric mirrors
NIST, Gaithersburg, MD
• Nuclear reactor neutron source
Measure helium retention by neutron depth profiling (NDP) technique
Ion Beam Laboratory
University of North Carolina at Chapel Hill, NC
Previous results of He retention in W
•
1.3 MeV to a dose of 1020 3He/m2 at 850°C followed by a flash anneal at 2000°C
•
Same total dose was implanted in 1, 100, 500, and 1000 cycles of implantation
and flash heating
3
Relative He retention
1.00
0.80
0.60
0.40
Mono He in SCW
0.20
Threat Spec in PolyW
0.00
1.00E+17
1.00E+18
1.00E+19
1.00E+20
3
He dose per cycle (m-2)
NRA results of 3He retention for single crystal and polycrystalline tungsten with
a total dose of 1020 He/m2. Percentage of retained 3He compared to implanting
and annealing in a single cycle.
Ion Beam Laboratory
University of North Carolina at Chapel Hill, NC
New work with helium threat spectrum
•
Degrade the monoenergetic beam by transmission through a thin Al foil
•
Tilting the foil provides a range of degraded energies by varying the path length d
through the foil
t
d
where  = 0° is normal incidence
cos θ
Foil
E0
Tungsten
E = E0 – Efoil
He beam
t
•
Al stopping power: ~330 keV/micron
•
900 keV 3He beam through a 1.5 micron Al foil tilted 0 – 60°
•
Degraded energies: 100 – 500 keV
Ion Beam Laboratory
University of North Carolina at Chapel Hill, NC
Threat spectrum implantation conditions
Relative He fluence
IFE Helium Threat Spectrum
0
200
400
600
800
1000
1200
1400
Energy (keV)
•
Implantation at 850°C with flash heating to 2000°C between implant steps or at the end of a
single step implant. (Temp. measured by infrared thermometer.)
•
Total helium dose is divided by the no. of steps
Partial dose is implanted as a threat profile with the sample at 850°C
Sample heating 850°C  2000°C  850°C (10 s cycle)
•
Next implant step begins
•
LabVIEW automates foil tilt motions to implant correct dose at each position and controls
sample temperature via power controller and infrared thermometer
•
NDP used to determine helium depth profiles and for comparison of total helium retention
Ion Beam Laboratory
University of North Carolina at Chapel Hill, NC
NDP
Neutron monitor
Neutron

Sample
beam
NDP Experimental Arrangement
NDP of boron in silicon
Depth range: 15 nm – 3.8 µm
1e22
Detection limit (at/cm3)
• Technique: Neutron Depth Profiling (NDP) measures
elemental concentration profiles up to a few micrometers in
depth for elements that emit a charged particle following
neutron capture. (R.G. Downing, et al., NIST J. Res. 98 (1993)109.)
• Elements Analyzed: boron, lithium, helium, nitrogen and
several additional light elements with less sensitivity.
• Sample Environment: In an evacuated chamber, samples
are irradiated with a beam of low energy neutrons. A small
percentage of the emitted reaction particles are analyzed by
surface barrier detectors to determine their number and
individual energies.
• Principles: The emission intensity is compared to a known
standard to quantitatively determine the elemental
concentration. The emitted particles lose energy at a
predicable rate as they pass through the film; the total energy
loss correlates to the depth of the reacting nucleus.
• Advantage: NDP is non-destructive - allowing repeated
determinations of the sample volume following different
treatment processes.
• Neutron beam flux at sample: ~7.5x108 n/cm2-s
• Beam area: from a few mm2 to ~110 mm2
• Reaction: NDP utilizes the 3He(n,p)T reaction (5333 barns)
and produces 572 keV protons and 191 keV recoil tritons.
FTIR
1e20
RBS
NDP
1e18
1e16
1e14
XRF
TOF-SIMS
TXRF
Dynamic SIMS
1e12
1000 Å 1µm 10 µm 100 µm 1 mm 1 cm
Sample Dimension
He retention for 1020 He/m2 in nano-W(<100nm Particles)
Ion Beam Laboratory
University of North Carolina at Chapel Hill, NC
He retention comparisons for 1020 He/m2
nano-porous (>500nm particles) W with HfC
Ion Beam Laboratory
University of North Carolina at Chapel Hill, NC
Results of He3 Retention in nano-porous W
Implanted with Helium Threat Spectrum
Nano- porous W (<100 nm) samples showed very dramatic decrease in retention of He
when high dose (1E20/m2) implanted sample was heated to 2000 C, 5 min.
- Results confirm diffusion data of Wagner and Seidman- Phys Rev Lett 42, 515 (1979)
Nano-cavity W (>500 nm) samples behaved very much like poly crystalline W.
- nano particle size too big to have effective diffusion.
Ion Beam Laboratory
University of North Carolina at Chapel Hill, NC
Carbon implantation in W to form WCx
Shon Gilliam, Zane Beckwith, Richard Parker, Nalin Parikh (UNC-Chapel Hill)
Greg Downing (NIST)
Glenn Romanoski, Lance Snead (ORNL)
Shahram Sharafat, Nsar Ghoniem (UCLA)
Why are we interested?
• Carbon ion irradiation and high temperatures in the first wall may lead to
tungsten carbide formation
• The presence of WCx may affect helium retention characteristics
Objectives
• Try to form W2C in W samples through high fluence implantation of C and high
temperature annealing
• Study how W2C effects hydrogen and helium retention/diffusion
Ion Beam Laboratory
University of North Carolina at Chapel Hill, NC
XRD Spectra of C+ implantation into W to form
W2C under various implantation conditions
GM2
W2C
Formation
•
•
•
GM2 100 keV 1.4e19 C/cm2 at RT 2000C/5min.
GM3 1.5 MeV 3.5e17 C/cm2 at RT 2000C/5min.
30 Managed by UT-Battelle
for the Department of Energy
Oct 30 -31 , 2007
P04637 (threat spectrum) 1e18 C/cm2 atHAPL
RTMeeting
2000C/5min.
st
Summary of W2C formation study
• 100 keV C implantation shows new XRD peaks compared to unimplanted W
• Need to establish conditions for W2C formation for samples implanted with C
threat-spectrum
• Need to confirm that new peaks indicate W2C formation
• XTEM to observe microstructure of new phase
• After the phase is identified, implant H and He threat spectra to study
retention
Proposed Research
• Reproduce He3 retention in nano-porous W
•In cooperation with Plasma processes, Inc. (Scott O’Dell) and NIST (G. Downing)
• Formation of Tungsten Carbide
• UNC (Parikh,et al), ORNL (G. Romanoski) and UCLA (S. Sharafat, N. Ghoniem)
•Accrual of carbon in near surface volumes of tungsten.
•Damage phenomena associated with the implantation of Carbon
•Mobility of carbon to the W/steel interface by grain boundaries and splat boundaries
(for plasma sprayed tungsten). This route should be at least 10X faster than bulk
diffusion through tungsten.
• Effect of Carbide on Diffusion and Surface Integrity
•Implantation and carbide formation, UNC (Parikh, et al)
•Thermal Fatigue and Thermal Stability (Romanoski, et al ORNL)
•Modeling of diffusion and release of helium
Acknowledgement
This research is supported under the US Department of Energy, High Average
Power Laser Program managed by the Naval Reactor Laboratory through
subcontract with the Oak Ridge National Laboratory.
Publications
S. Gilliam, S. Gidcumb, D. Forsythe, N. Parikh, J. Hunn, L. Snead, G. Lamaze,
Helium retention and surface blistering characteristics of tungsten with regard to
first wall conditions in an inertial fusion energy reactor, Nuclear Instruments and
Methods B, 241 (2005) 491-495.
S. Gilliam, N. Parikh, S. Gidcumb, B. Patnaik, J. Hunn, L. Snead, G. Lamaze,
Retention and surface blistering of helium irradiated tungsten as a first wall
material, Journal of Nuclear Materials, 347 (2005) 289-297.
R. G. Downing, R. Parker, R. Scelle and N. Parikh, Helium Retention in NanoCavity Tungsten Implanted with Helium Threat Spectrum Mimicking IFE Reactor
Conditions, American Nuclear Society (Nov. 2007)
Ion Beam Laboratory
University of North Carolina at Chapel Hill, NC