Transcript PPT - Fusion Energy Research Program

Chamber Dynamic Response,
Laser Driver-Chamber Interface and
System Integration for Inertial Fusion Energy
Mark Tillack
Farrokh Najmabadi
Rene Raffray
First IAEA-CRP-RCM on
“Elements of Power Plant Design for Inertial Fusion Energy”
May 21-25, 2001
IAEA Headquarters, Vienna
Outline
• ARIES power plant studies program
• Assessment of IFE chambers
• Laser driver-chamber interface studies
• Final optics damage
• Beam propagation through chamber media
• Chamber dynamic response and clearing
• Numerical modeling
• Simulation experiments
Goals of ARIES Integrated IFE Chamber
Analysis and Assessment Research
 Analyze & assess integrated, self-consistent IFE chamber concepts
 Understand trade-offs and identify design windows for promising
concepts. The research is not aimed at developing a point design.
 Identify existing data base and extrapolations needed for each
promising concept. Identify high-leverage items for R&D:
• What data is missing? What are the shortcomings of present tools?
• For incomplete database, what is being assumed and why?
• For incomplete database, what is the acceptable range of data?
Would it make a difference to first order, i.e., does it make or break
the concept?
• Start defining needed experiments and simulation tools.
ARIES-IFE is a Multi-Institutional Effort
OFES
Advisory/Review
Committees
Program Management
F. Najmabadi
Les Waganer (Operations)
Mark Tillack (System Integration)
Executive Committee
(Task Leaders)
Tasks
Fusion
Labs
•
•
•
•
•
Target Fab. (GA, LANL*)
Target Inj./Tracking (GA)
Chamber Physics (UW, UCSD)
Chamber Eng. (UCSD, UW)
Parametric Systems Analysis
(UCSD, BA, LLNL)
• Materials (ANL)
• Target Physics (NRL*, LLNL*, UW)
• Drivers* (NRL*, LLNL*, LBL*)
• Final Optics & Transport
(UCSD, LBL , PPPL, MIT, NRL*,LLNL*)
• Safety & Env. (INEEL, UW, LLNL)
• Tritium (ANL, LANL*)
• Neutronics, Shielding (UW, LLNL)
* voluntary contributions
An Integrated Assessment Defines the R&D Needs
Target
Designs
Chamber
Concepts
Target fabrication,
injection, and tracking
Driver
Characterization
of target yield
Characterization
of chamber response
Chamber
environment
Final optics &
chamber propagation
Assess & Iterate
Chamber R&D:
Data base
Critical issues
Status of ARIES-IFE Study
 Six combinations of target and chamber concepts are under
investigation:
Dry wall
Solid wall with
sacrificial layer
Thick Liquid Wall
Direct drive
target
Nearly Complete,
Documentation
Work started
in March 2001
*
Indirect drive
target
Work started
in March 2001
* Probably will not be considered
Driver-Chamber Interface & Final Optic Damage
85ϋ
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)
The UCSD laser-plasma and laser-material
interactions lab is used for damage tests
Spectra Physics YAG laser:
2J, 10 ns @1064 nm;
800, 500, 300 mJ @532, 355, 266 nm
Peak power density ~1014 W/cm2
Reflectometry
100 ppm accuracy
Class 100
cleanroom
enclosure
Profiling
Shack-Hartmann
Modeling the effects of damage on beam
characteristics helps us establish damage limits
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
particles
Laser propagation near or beyond the
breakdown threshold is uncertain
 Laser intensity near the target:
1013 – 1014 W/cm2
 Threshold intensity is not welldefined; laser light partially ionizes
chamber gas at any intensity
 Gas “breakdown” occurs when
plasma density is high enough that
a substantial amount of laser light is
absorbed (avalanche process).
Data for Xe, except Turcu
 Previous work: breakdown threshold defined as intensity at which visible light is emitted
from the focal spot (most of the visible light is generated by the interaction of electrons
generated by ionization of the background gas with the neutral gas atoms).
 Wavefront distortion can occur at lower (or higher) plasma densities and laser intensities,
changing the beam profile on the target. This “threshold” intensity will depend on the
required degree of beam smoothness on the target, f number of the lens, beam coherence, etc.
 Multi-species and contaminated environmental conditions further complicate the physics.
Understanding Chamber Dynamics and
Clearing is a Critical R&D Item
 The rep-rate is limited by the time it takes for the chamber
environment to return to a sufficiently quiescent and clean,
low-pressure state following a target explosion to allow a
second shot to be initiated (goal: 100-200 ms).
 Many complex phenomena must be understood and modeled.
Gas dynamics:
 Compressible
 Radiation heat transport
 Dissipative processes
 …
Volume interactions:
 In-flight evaporation
 In-flight re-condensation
 Chemistry
 …
Surface Physics:
 Melting & melt layer behavior
 Evaporation/sublimation
 Sputtering
 Macroscopic erosion
 Condensation and redeposition
 …
Response of Chamber to Target Explosion
Covers Two Vastly Different Time Scales
 “First pass” of target-released energy through the chamber –
“fast” time scale (ns to several ms).
 Propagation of X-rays and ions through the chamber;
 Re-radiation of the ions & X-ray energy deposited in the chamber
gas.
 At the completion of this phase, the chamber volume is in a
non-equilibrium state and material is released from the wall.
 Relaxation of chamber environment to a equilibrium state –
“slow” time scale (several ms to hundreds of ms).
 Mass and heat transport in the chamber & to/form chamber wall
 Relaxation to “residual” chamber environment (“pre-shot”
environment)
 The “pre-shot” environment affects target injection & tracking,
laser propagation, …
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 Dynamics Simulation Experiments –
Exploration and Planning
 Simulation experiments are essential to:
 Benchmark simulation codes;
 Ensure all relevant physical phenomena is taken into account
 Relatively new field: Previous experimental work focused on
shock propagation and/or condensation of wetted chamber walls.
 Eventually, we need scaled experiments to screen concepts for
implementation on integrated research experiments (IRE’s).
 Two major areas need to be investigated first:
1. A source of energy to produce prototypical environments for
experimentation,
2. Experiment characterization and array of diagnostics.
Scaled Simulation Experiments Can
Help Address Many Chamber Issues
1–10 J
• Beam propagation and focusing
• Near-surface physics
• Diagnostic development and experimental techniques
100–500 J
• Large-volume tests for geometrically prototypical testing
1–10 kJ
• Integrated (simultaneous) surface and volume effects
• Chamber dynamics in limited volume (~1 liter)
>10 MJ
Incl. neutrons
• Integrated prototypical chamber testing
Many Opportunities Exist for
International Collaboration
• Design studies
• ARIES-IFE
• Laser driver-chamber interface studies
• Modeling and experiments on optics damage
• Breakdown and beam propagation through chambers
• Chamber dynamic response and clearing R&D
• Numerical modeling
• Simulation experiments