Transcript PPT - Advanced Energy Technology Program

Overview of Inertial Fusion
Energy Technology Activities
Mark Tillack
1. Overview of IFE activities in the US
2. Overview of IFE activities at UCSD
3. Optics damage studies at UCSD
July 3, 2001
CIEMAT, Madrid
IFE research is coordinated between
several distinct program elements
Chamber Related
(OFES - VLT)
ARIES-IFE
(OFES - VLT)
Target Tech & Design
(OFES - Science)
Heavy Ion Drivers
(OFES - Science)
Chamber Related (DP)
Target Technology (DP)
Laser Drivers (DP)
OFES R&D focuses on two chamber types
HYLIFE-II: Thick-Liquid-Wall Chamber
SOMBRERO: Dry-Wall Chamber
Different scales
First wall radius:
HYLIFE-II = 3.5 m
SOMBRERO = 6.5 m
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•
•
•
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Georgia Institute of Technology (GT)
Idaho National Environmental & Engineering Lab (INEEL)
Lawrence Livermore National Laboratory (LLNL)
Oak Ridge National Laboratory (ORNL)
University of California:
– Berkeley (UCB), Los Angeles (UCLA), San Diego (UCSD)
•
University of Wisconsin – Madison (UW)
IFE chamber research funded by OFES
• Dry-wall chamber research
• Thick-liquid-wall chamber research
• Driver/chamber interface
– heavy-ion drivers
– laser drivers
• IFE safety and environmental studies
Dry-wall chambers: key features and issues
• Low pressure (< 0.5 Torr), high-Z gas (Xe) protects first
wall from short-ranged target emissions
• Low activation structures (C/C composites and/or SiC)
• Flowing Li2O granules serve as breeder and coolant
• Modular blanket for ease of replacement
• Suited for direct-drive targets
SOMBRERO
Key Issue: Chamber Lifetime. Can the first wall
be protected from x-ray and debris damage? Can
first wall and blanket structures tolerate the effects
of neutron damage for an acceptably long time and
be designed for economical replacement?
Thick-liquid-wall chambers:
key features and issues
• Thick liquid “pocket” shields chamber
structures from neutron damage and
reduces activation
• Oscillating jets dynamically clear
droplets near target
• No blanket replacement required,
increases chamber availability
• Suited for indirect-drive targets
HYLIFE-II
Key Issue: Chamber Clearing. Can the liquid pocket and beam port protection jets
be made repetitively without interfering with beams? Will vapor condensation,
droplet clearing and flow recovery occur fast enough to allow pulse rates of ~ 6 Hz?
Driver/chamber interface: heavy ion drivers
Injector
manifolds
Key Issue: Self-consistent design. Can
superconducting final focusing magnet
arrays be designed consistent with
chamber and target solid angle limits for
the required number of beams, standoff
distance to the target, magnet dimensions
and neutron shielding thickness?
Main flibe
pocket jets
Crossing jets for
beam ports
Final focus
magnets
Shielding and
vacuum pumping
HYLIFE-II with ~ 200 beams
Driver/chamber interface: laser drivers
85Þ
40 cm
stiff, lightweight, actively cooled, neutron transparent substrate
4.6 m
Two primary options are being
considered for the final optic:
1. Grazing incidence metal mirrors
2. Transmissive refractive optics
Grazing incidence mirrors
Key Issue: Protection and survival. Can
final optics be adequately protected from xrays, debris and dust and survive laser and
neutron damage for more than one year
before replacement? Will final optics have
sufficient mechanical stability under pulsed
operation to maintain the required pointing
accuracy for target tracking?
Si2O or CaF2 wedges
Safety and environmental studies
Flow between volumes
considers friction, form
losses and chocking
Considers non-condensible
gas effects
Leak
Filtered
Dried
Heat transfer to
structures
Conservation
of mass,
momentum and
energy for both
liquid and
vapor phases
Aerosol transport
and deposition
Suppression pools,
heat exchangers,
valves, pumps, etc.
Schematic of MELCOR Capabilities
Key Issues:
Power Plants: Can a level of safety be
achieved so that a public evacuation
plan is not required (< 10 mSv (1 rem)
site boundary dose) for credible
accident scenarios?
Thick-Liquid-Wall Chambers: Can
radioactive hohlraum materials be
recovered from flibe and recycled in
new targets?
Dry-Wall Chambers: Can replaced
chamber materials be recycled to
minimize annual waste volumes? Can
tritium retention in candidate materials
(C/C composites, SiC) be maintained at
an acceptable level?
Goals of the High Average Power Laser Program
Long term goal:
Develop science & technologies required for Inertial Fusion Energy
Focussed on direct drive with lasers
Builds upon recent advances in target design & lasers
Complementary technologies (target fab/injection, chambers, final optics)
Short term goal:
Science & technologies for a rep-rate laser/target/chamber system for DP needs
Study detailed properties of matter relevant to DP
Rep-rate allows extremely accurate and flexible experiments
Complement high energy single shot facilities
Achieving these goals requires development as a coherent, integrated system
Spin offs:
Advanced laser technologies
Robust, high damage threshold optics
Advanced pulsed power systems
Target/ chamber/ final optics development for the NIF
Development of directed energy technologies
High quality science
The elements of the High Average Power Laser Program
2. Target Fabrication
GA: Fab, charac, mass production
1. Direct Drive Target Designs
LANL: Adv mat, target fab, DT inventory
NRL- Nike Program
Target
Schafer: Foams, cryo layering
LLNL: Yield spectrum
factory
Wisconsin- Yield spectrum
3. Target Injection
GA: Injector, Injection & Tracking
LANL: Materials prop, thermal resp.
4. Lasers
NRL: KrF (gas) Laser
LLNL: (DPSSL)
6. Chambers
Wisconsin: Dry wall, safety, integrate design
LLNL: Other walls, target yield, neut damage 5. Final Optics
LLNL: X-rays, ions, debris, neut.
UCSD: Chamber clearing, materials
UCSD: Laser damage, debris mit
SNL et al: Materials resp to x-rays & ions
LANL: Neutrons on optics
The Electra KrF laser (NRL): 1/4 mm, 700 J, 5 Hz
The Mercury dpssl laser (LLNL): 100 J, 1.05 mm, 10 Hz,
2-10 ns, 10% laser for IFE-related experiments
Diode pulsers
Front
end
Injection multipass spatial filter
Gas-cooled
amplifier
Pump
head
delivery
Overview of Inertial Fusion Energy
Technology Activities at UC San Diego
Mark Tillack
http://joy.ucsd.edu
July 3, 2001
CIEMAT, Madrid
UCSD IFE Technology Program Organization, June 2001
Driver
interface
M. Tillack
Final Optics
M. Tillack
Chamber
physics
F. Najmabadi
Beam
Propagation
Numerical
modeling
Experiments
F. Najmabadi
M. Tillack
M. Tillack
A. Gaeris
T. K. Mau
(modeling)
S. S. Harilal
(spectroscopy)
S. S. Harilal
J. Pulsifer
(vac. eng.)
B. Harilal
A. Gaeris
(smoothing)
D. Blair
IFE power plant
studies
F. Najmabadi
Integration
M. Tillack
Engineering
responses
Target
engineering
R. Raffray
M. Tillack
F. Najmabadi
M. Zaghloul
(testing)
Collaboration w/
UCLA, LANL,
LLNL, GA
IFE
engineering
R. Raffray
Z. Dragojlovic
(integrated
modeling)
M. Zaghloul
(materials
response)
Collaboration w/
ANL, INEEL
R. Raffray
M. Zaghloul
X. Wang
J. Pulsifer
R. Raffray
E. Abu-Nada
(integrated
modeling)
T. K. Mau
(radiation)
J. Pulsifer
(thermal
analysis)
Collaboration w/
General Atomics
Chamber Eng.
Chamber wall
engineering
M. Zaghloul
X. Wang
M. Tillack
Collaboration w/
Sandia Albuquerque
System Model
Final optics
R. Miller
E. Abu-Nada
T. K. Mau
Driver Interface R&D: Beam Propagation
Problem Statement
• The chamber environment following a target explosion contains a hot, turbulent
gas which will interact with subsequent laser pulses.
• Gas breakdown occurs in the vicinity of the target where the beam is focussed.
• A better understanding of the degree of gas ionization and the effects on beam
propagation are needed.
• The effect of aerosol and particulate in the chamber must be understood in order
to establish clearing criteria.
Research Objectives:
• Determine the laser
breakdown threshold in pure
and impure chamber
environments at low pressure.
• Determine the effect of
chamber environmental
conditions on beam propagation.
Beam propagation experiments will be performed in a
multi-purpose vacuum chamber under construction
Key Program Elements
• Construction of a multi-purpose vacuum chamber
• Breakdown emission detection and spectroscopy
• Laser beam smoothing and accurate profiling
(goal of 2-5%)
Initial measurements:
• Visible light emission from the focal spot
• Variation in laser energy profile (CCD) & temporal
pulse shape (photodiodes)
• Wavefront variation (Shack-Hartmann)
Planned future measurements:
• Emission spectroscopy
• Changes in spatial profile with 2% accuracy
Chamber Physics Modeling and Experiments
Problem Statement
The chamber condition following a target explosion in a realistic chamber geometry is
not well understood. The key uncertainty is whether or not the chamber environment will
return to a sufficiently quiescent and clean low-pressure state to allow another shot to be
initiated within 100–200 ms. Modeling and experimental capabilities are needed to
predict the behaviour of an IFE power plant chamber and to ensure that all relevant
phenomena are taken into account.
Objectives
• Develop and benchmark an integrated, state-of-the-art computational model of the
dynamic response of IFE chambers following target explosions
• Use the code to plan experiments and study IFE chambers
• Demonstrate validity of scaling and simulation experiments
• Develop chamber experimental capabilities
• Provide new data relevant to IFE chamber responses
Multi-physics model of chamber dynamics
Target
Chamber
Driver Beams
Wall
Convection
Phase
change
Energy Conservation
Phase change
Transport & deposition
Energy
Input
Eqns. of state
Pressure (T)
Energy deposition
Conduction
Heat
transfer
Radiation transport
Viscous dissipation
Impulse
Momentum
Input
Pressure
(density)
Mass Conservation
Mechanical
response
Fluid
hydrodynamics
Evaporation,
sputtering ...
Erosion/
redeposition
(multi-phase, multi-species)
Condensation
Evacuation
Thermal stress
Momentum Conservation
Impulse
Mass
Input
Thermal
response
Chamber Physics Simulation Experiments
Energy required to simulate IFE chamber issues
1-10 J
Optics damage
Beam propaga tion
Surface phy sics and ne ar-surface chamber interactions
Diagno stic development and exper imental techniques
100-500 J
Volumetric tests in small prototypi cal chambers (~1 liter)
1-10 kJ
Simultaneous surface and volu me effects (~10 liter)
>10 MJ
Integrated p rototypical chamber testing
Direct surface illumination
x-ray source w/close-in targets
HYADES simulation of laser irradiation of Au
Micro-enclosure
Engineering Modeling of IFE Targets
Layering
Injection
Free Flight
Chamber Transport
Hydrodynamic
interactions
Mass transfer
Transient stresses
Acceleration in sabot
Input Parameters
Initial target configuration
Properties database
Imposed accelerations
Thermal environment
Chamber gas, aerosol and particulate species
Chamber hydrodynamic environment
In-hohlraum beta layering analysis:
Gravity
Thermal radiation
Convective
heat transfer
Computed Parameters
Target temperature distribution
Target trajectory
Target internal stress distribution
Internal mass transport
IFE Wall Engineering
ESLI carbon fiber flocked surface
RHEPP/MAP ion beam facility, SNLA
Structured surfaces may offer superior
thermal response and improved erosion
behavior under exposure to pulsed energy
sources
Studies of Laser Induced Damage
to Grazing Incidence Metal Mirrors
Mark Tillack
http://joy.ucsd.edu
July 3, 2001
CIEMAT, Madrid
Geometry of the Driver-Chamber Interface
85Þ
40 cm
stiff, lightweight, actively cooled, neutron transparent substrate
(20 m)
4.6 m
Grazing incidence mirrors
(30 m)
(SOMBRERO
values in red)
Prometheus-L reactor building layout
Si2O or CaF2 wedges
Final Optic Damage Threats
Two main concerns:
• Damage that increases absorption (<1%)
• Damage that modifies the wavefront –
–
spot size/position (200mm/20mm) and spatial uniformity (1%)
Final Optic Threat
Nominal Goal
Optical damage by laser
>5 J/cm2 threshold (normal to beam)
Sputtering by ions
Ablation by x-rays
(~25 mJ/cm2, partly stopped by gas)
Wavefront distortion of <l/3 * (~100 nm)
(6x108 pulses in 2 FPY:
2.5x106 pulses/allowed atom layer removed)
Defects and swelling induced by
g-rays (~3) and neutrons (~18 krad/s)
Absorption loss of <1%
Wavefront distortion of < l/3 *
Contamination from condensable
materials (aerosol and dust)
Absorption loss of <1%
>5 J/cm2 threshold
* “There is no standard theoretical approach for combining random wavefront distortions of individual optics.
Each l/3 of wavefront distortion translates into roughly a doubling of the minimum spot size.” (Ref. Orth)
GIMM development issues*
• Experimental verification of laser damage thresholds
• Wavefront issues: beam smoothness, uniformity, shaping,
f/number constraints
• Experiments with irradiated mirrors
• Protection against debris and x-rays (shutters, gas jets, etc.)
• In-situ cleaning techniques
• Large-scale manufacturing
• Cooling
* from Bieri and Guinan, Fusion Tech. 19 (May 1991) 673.
Aluminum is the 1st choice for the GIMM
• Lifetime of multi-layer dielectric mirrors is
Normal incidence reflectivity of metals
1
questionable due to rapid degradation by neutrons
0.8
• Al maintains good reflectivity into the UV
0.6
Reflectivity
• Al is a commonly used mirror material
– easy to machine, easy to deposit
• Thin (~10 nm), protective, transparent oxide
0.4
0.2
Ag
Al
Cu
W
Au
Hg
Mo
0
200
Aluminum reflectivity at 532 nm
1
Reflectivity
0.95
•
0.9
•
•
•
p-polarized
0.85
0.8
0.75
10
20
30
600
800
1000
Wavelength, nm
s-polarized
0
400
40
50
60
Angle of incidence
70
80
90
Normal incidence damage threshold ~0.2 J/cm2
Grazing incidence raises s-reflectivity to >99%
Larger footprint reduces fluence by cos(q)
Combined effects hopefully raise the damage
threshold to >5 J/cm2
Several surface types have been fabricated
Al 1100
diamond-turned Al 6061
MgSi occlusions
99.999% pure Al
75 nm Al on superpolished flat:
±2Å roughness, 10Å flatness
UCSD Laser Plasma and Laser-Material
Interactions Laboratory
Spectra Physics laser:
2J, 10 ns @1064 nm
700, 500, 300 mJ
@532, 355, 266 nm
Peak power~1014 W/cm2
Profiling
Shack-Hartmann
Q ~ 200 mrad
Ringdown reflectometry is used for accurate
measurements and in-situ surface monitoring
partially-reflective
spherical output coupler
1
100 ppm accuracy
photodiode
Reflectivity
0.95
no oxide
10 nm
0.9
20 nm
30 nm
Al 6061
Al 1100
0.85
0
10
20
30
40
50
Angle
60
70
80
90
In-situ reflectometry can measure surface
changes not visible to the naked eye
Al 1100 shows no apparent damage up to 1 J/cm2
1000 shots in Aal 1100 at 85˚, 1 J/cm2 peak
Several shots in Al 6061 at 80˚, 1 J/cm2 peak
MgSi
Fe
Fe
1000x
1000x
• Damage occurs at a higher fluence as compared with normal incidence
• Silicide occlusions in Al 6061 preferentially absorb light, causing
explosive ejection and melting
• Fe impurities appear unaffected
• Exposure of Al 1100 to 1000 shots at 85˚ exhibited no damage
Tools for modeling effects of damage
on beam characteristics
Dimensional Defects
Gross deformations,
>l
Compositional Defects
Surface morphology,
 <l
Gross surface
contamination
Local contamination
CONCERNS
•
•
•
•
Fabrication qu ality
Neutron swelling
Thermal swelling
Gravity lo ads
• Laser-induced
damage
• Thermomechanical
damage
• Transmutations
• Bulk redeposition
• Aerosol, du st &
debris
MODELLING TOOLS
Optical design
software (ZEMAX)
Scattering by rough
surfa ces (Kirchhoff)
Fresnel multi-layer
solver
Scattering by p articles
Effect of Surface Coatings and Contaminants
metal substrate
n4, k4
n3, k3
coating
n2, k2
contaminant
q1
n1, k1
• 4-layer Fresnel model was developed to examine
behavior of coatings and contamination
• Surface contaminants (such as carbon) on mirror
protective coatings can substantially alter reflectivity,
depending on layer thickness and incident angle.
Incident
medium
d2=0
q1 = 80o
d2=0
q1 = 0o
1
80o
60o
40o
lo = 532 nm
Al2O3 coating (10 nm)
Al mirror
20o
reflectivity
0.8
0.6
lo = 532 nm
Carbon film
Al mirror
0.2
q1 =
d2=2 nm
q1 = 80o
0.4
0o
d2=2 nm
q1 = 0o
0
0
Carbon film thickness (nm)
0.05
0.1
0.15
0.2
0.25
Al2O3 coating thickness, d3/lo
0.3
The effect of induced surface roughness on beam quality
was investigated using Kirchhoff wave scattering theory
• Specularly reflected intensity is degraded by induced mirror surface
roughness
• For cumulative laser-induced and thermomechanical damages, we assume
Gaussian surface height statistics with rms height s.
1.0
Isc
Iinc
q1
0.8
q2
q1 = 80o
0.6
70o
0.4
Isc
60o
0.2
0.1
g
 Id
Io : reflected intensity from smooth surface
Id : scattered incoherent intensity
g : (4p s cosq1/l)2
0
0
 I 0e
0.2
0.3
0.4
0.5
e.g., at q1 = 80o, s/l = 0.1, e-g = 0.97
s/l
• Grazing incidence is less affected by surface roughness
• To avoid loss of laser beam intensity, s / l < 0.01
University of California, San Diego
School of Engineering
Graduate Studies in Plasma Physics &
Controlled Fusion Research
Current Research Areas:
• Theoretical low temperature plasma physics
• Experimental plasma turbulence and transport studies
• Theoretical edge plasma physics in fusion devices
• Plasma-surface interactions
• Diagnostic development
• Semiconductor manufacturing technology
• Theory of emerging magnetic fusion concepts
• Fusion power plant design and technology
• Radio-frequency heating and current drive
• Laser-matter interactions and inertial confinement fusion
• Thermo-mechanical design of nuclear fusion reactor components
• Theoretical space and astrophysical applications
Interested students are encouraged to visit
our website at:
http://www-ferp.ucsd.edu/brochure.html
for information on our research, available
financial support and
university admissions policy.