Transcript Document 7879349

Output Calculations for Laser Fusion
Targets
Robert R. Peterson and Donald A. Haynes
University of Wisconsin-Madison
ARIES Meeting
September 18-20, 2000
Princeton University
Fusion Technology Institute
University of Wisconsin - Madison
NRL IFE Concepts Project
9/19/2000
1
Variables Considered
For Choosing the Cavity
Variables Considered For Choosing the
Gas Environmentin
in SOMBRERO
SOMBRERO
GasCavity
Environment
Gas Atom Species
Target
Injection
Gas Opacity:
Stopping of
Target Ions
Stop target xrays and wall
radiant heat
Laser
Propagation:
Breakdown
Neutron
Activation
of Gas
Density of Gas Atoms
Fusion Technology Institute
University of Wisconsin - Madison
NRL IFE Concepts Project
9/19/2000
2
Chamber Physics Critical Issues Involve Target
Output, Gas Behavior and First Wall Response
Target Output
Gas Behavior
Design,
Gas Opacities,
X-rays,
Thermal
Fabrication,
Radiation Transport, Radiation,
Output Simulations, Ion Debris,
Rad-Hydro Simulations Shock
(Output Experiments) Neutrons
Wall Response
Wall Properties,
Neutron Damage,
Near-Vapor Behavior,
Thermal Stresses
UW uses the BUCKY 1-D Radiation-Hydrodynamics Code to Simulate
Target, Gas Behavior and Wall Response.
Fusion Technology Institute
University of Wisconsin - Madison
NRL IFE Concepts Project
9/19/2000
3
BUCKY is a Flexible 1-D Lagrangian RadiationHydrodynamics Code
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1-D Lagrangian MHD (spherical, cylindrical or slab).
Thermal conduction with diffusion.
Applied electrical current with magnetic field and pressure calculation.
Radiation transport with multi-group flux-limited diffusion, method of short
characteristics, and variable Eddington.
Non-LTE CRE line transport.
Opacities and equations of state from EOSOPA or SESAME.
Equilibrium electrical conductivities
Thermonuclear burn (DT,DD,DHe3) with in-flight reactions.
Fusion product transport; time-dependent charged particle tracking, neutron energy
deposition.
Applied energy sources: time and energy dependent ions, electrons, x-rays and lasers.
Moderate energy density physics: melting, vaporization, and thermal conduction in
solids and liquids.
Benchmarking: x-ray burn-through and shock experiments on Nova and Omega, x-ray
vaporization, RHEPP melting and vaporization, PBFA-II K emission, …
Platforms: UNIX, PC, MAC
Fusion Technology Institute
University of Wisconsin - Madison
NRL IFE Concepts Project
9/19/2000
4
Direct and Indirect Drive Targets Under Consideration
Have Different Output
1  CH + 300 Å Au
NRL Direct-drive Laser
Targets May Contain High Z
0.265g/cc
0.25 g/cc
Indirect-drive HIF and Z-pinch
Targets Have High-Z Hohlraums
Foam + DT
DT Fuel
DT Vapor
1  CH
1.952 mm
Foam + DT
DT Fuel
0.265g/cc
1.69 mm
1.5 mm
0.25 g/cc
LLNL/LBNL HIF Target
DT Vapor
1.62 mm
1.44 mm
1.22 mm
X-1 Target
6 mm
Au
He gas
BeO
Be98O2
DT ice
2 mm
DT gas
0
Fusion Technology Institute
University of Wisconsin - Madison
NRL IFE Concepts Project
9/19/2000
5
Original SOMBRERO Study Operated Under Substantially
Different Target Assumptions Than Are Currently Used
Tmin
(K)
T
Allowed
(K)
Target
Reflectivity
Wall
Emissivity
Flight
Length
(m)
Flight
Time
(ms)
Gas
Density
(Torr)
Output
Spectra
Yield
(MJ)
SOMBRERO
(1991)
4
14
0
(no Au)
1.0
6.5
16.3
Xe
.5
given
400
SOMBRERO
(2000)
18
0.5 –
1.7
.99
.8
<2
<5
Xe Kr
< 0.5
given
400
NRL Target
18
0.5 –
1.7
.2
.8
2 – 6.5
5–
16.3
Xe
?
Calc.
160
Fusion Technology Institute
University of Wisconsin - Madison
NRL IFE Concepts Project
9/19/2000
6
Direct-Drive Target Output is Dominated by
Neutrons and Energetic Ablator Ions
SOMBRERO Target
CH
DT ice
94 keV D 5.81 MJ
DT gas
141 keV T 8.72 MJ
138 keV H 9.24 MJ
188 keV He 4.49 MJ
1600 keV C 55.24 MJ
Total 83.24 MJ per shot
=15.68 J/cm2 on SOMBRERO Wall
Neutrons
317 MJ per shot
=59.7 J/cm2 on SOMBRERO Wall
X-Rays
22.41 MJ per shot
=4.22 J/cm2 on SOMBRERO Wall
Fusion Technology Institute
University of Wisconsin - Madison
Assumed Target X-Ray Spectrum
10
Spectrum (A.U.)
SOMBRERO Target
Debris Ions
10
16
Target X-ray Spectrum
15
1014
10
-1
10
0
10
1
Photon Energy (keV)
10
2
Z Experiments in Progress (6/15-6/21)
Explosion of a thin plastic foil with Z-pinch
x-rays (to simulate the explosion of an
ablator) and a measurement of ion energies
NRL IFE Concepts Project
9/19/2000
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Bucky Target Implosion and Burn Calculations
used to Study Target Output
•Laser deposition comes from
Andy Schmitt’s calculation.
•Pulse shape is then adjusted to
get best implosion.
•Sensitivity of output spectra
and partitioning to target yield
is studied by adding energy to
core.
10 2
Absorbed Laser Power (TW)
•Bucky does not have zooming
or detailed LPI, so laser
deposition will not agree with
codes that do.
NRL-DD-2
NRL-DD-14
10 1
10 0
10
-1
0
10
20
Time (ns)
Fusion Technology Institute
University of Wisconsin - Madison
NRL IFE Concepts Project
9/19/2000
8
Laser Quickly Burns though 300 Ǻ Au and 1 
Plastic and Launches a Shock in DT-wetted Foam
2.1
2.075
Laser
Position (mm)
2.05
2.025
Au
2
1.975
CH
1.95
1.925
1.9
0
NRL DD-35
15 Au zones
DT-wetted Foam
0.5
Fusion Technology Institute
University of Wisconsin - Madison
1
1.5
2
Time (ns)
NRL IFE Concepts Project
9/19/2000
9
With Laser Pulse NRL-DD-14, Target Implodes
and Ignites at 27.3 ns, giving 115 MJ of Yield
0.5
•22% of DT ice is burned;
NRL and LLNL get about
32 %.
•BUCKY burn fraction
would be improved with
further tuning.
•Target expands at a few x
108 cm/s and radiates.
0.4
Position (cm)
•Very little DT in wetted
foam is burned.
Au
CH
DT
0.3
DT-wetted foam
0.2
0.1
0
0
NRL DD-43
Fusion Technology Institute
University of Wisconsin - Madison
10
20
30
Time (ns)
NRL IFE Concepts Project
9/19/2000
10
Implosion Keeps In-Flight Aspect Ratio Less than
40; Convergence Ratio is About 9
NRL Thermally Smoothed Direct-Drive Laser Target
10
115 MJ NRL Laser Target
2
40
20 ns
22 ns
24 ns
26 ns
27 ns
27.2 ns
3
Mass Density (g/cm )
101
100
30
10
IFAR
10-1
20
-2
10
10
-3
10
-4
0
NRL-DD-43
0.1
0.2
0.3
0.4
0.5
Radius (cm)
Fusion Technology Institute
University of Wisconsin - Madison
0.6
0.7
0
0
NRL-DD-43
10
20
Time (ns)
NRL IFE Concepts Project
9/19/2000
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Most of Burn is in Cryogenic DT Ice and Takes
Place in < 50 ps
115 MJ NRL Laser Target
X-ray Emission from 115 MJ NRL Laser Target
At Bang Time = 27.3 ns
10
6
10
5
10 6
Fusion Power (TW/gm)
Fusion Power (TW)
104
103
10
2
101
10
10
0
-1
10-2
10 5
10
4
10 3
10 2
10
1
10-3
23
NRL-DD-43
24
25
26
27
28
29
Time (ns)
30
10 0
0
NRL-DD-43
Fusion Technology Institute
University of Wisconsin - Madison
0.1
0.2
Radius (cm)
NRL IFE Concepts Project
9/19/2000
12
Ion Spectrum for UW Best Burn
Ion Spectrum from 115 MJ NRL Laser Target
10
20
10
19
Number of Ions
•Ion Spectrum is calculated from
the velocity of each zone in the
final time step of the BUCKY.
•The particle energy of each
species in each zone is then
calculated as mv2/2.
•The numbers of ions of each
species in each zone are plotted
against ion energy.
•The spectra from direct fusion
product D, T, H, He3, and He4 are
calculated by BUCKY but are not
shown in the figure (their numbers
are low).
•Regions of origin are shown.
•In chamber calculations, these
ions are assumed to be launched
over 10 ns from the center of the
chamber.
10
10
DT Ice
D
T
H
C
Au
He
DT
Gas
Wetted Foam
18
Plastic
Au
17
SOMBRERO
10
16
10
3
NRL-DD-43
Fusion Technology Institute
University of Wisconsin - Madison
10
4
10
5
10
6
10
7
10
8
10
9
Ion Energy (eV)
NRL IFE Concepts Project
9/19/2000
13
Ion Spectrum for UW Adjusted Burn
Ion Spectrum from 160 MJ NRL Laser Target
10
20
10
19
Number of Ions
•Adjusted Burn has 140 MJ of
burn plus an extra 20 MJ in the
core plasma.
•Since 30% of the fusion yield
leaves the target as nonneutronic, x-ray and ion spectra
are equivalent to a 200 MJ
yield.
•SOMBRERO ion energies (one
energy for each species) are
shown for reference.
•Naturally, ion energies are
higher in adjusted burn case
(i.e. Au is 50 % more energetic)
•Extremely high energies of a
few Au ions do not agree with
LLNL calculations (molecular
flow?).
10
10
D
T
H
C
Au
He
DT Ice
DT
Gas
Wetted Foam
18
Plastic
17
Au
SOMBRERO
10
16
10
3
NRL-DD-49
Fusion Technology Institute
University of Wisconsin - Madison
10
4
10
5
10
6
10
7
10
8
10
9
Ion Energy (eV)
NRL IFE Concepts Project
9/19/2000
14
Gold Ions are at a Charge State Between 10 and
25; Other Ions are Full Stripped
•Charge State of debris ions is
important to deposition in Chamber
Gas.
160 MJ NRL Laser Target
•At launch time (end of target
explosion simulation), charge state
is taken from data tables in
temperature and density.
•The free electrons are assumed to
move with the ions (quasineutrality).
15
Final Charge State
•The tables are calculated by the
EOSOPA code in a Saha LTE
method.
20
10
5
•The greatly expanded target
remnants are probably in Coronal
Equilibrium or not in equilibrium at
all.
10
NRL-DD-49
Fusion Technology Institute
University of Wisconsin - Madison
20
30
Radius (cm)
NRL IFE Concepts Project
9/19/2000
15
X-ray Spectra from Targets is Changed by High
Z Components
X-ray Spectrum from 115 MJ and 160 MJ NRL and SOMBRERO Laser Targets
10-1
10
Normalized X-ray Fluence
•X-ray spectra are converted to sums
of 3 black-body spectra.
•Time-dependant spectra are in
Gaussian pulses with 1 ns halfwidths and are used in chamber
simulations.
• Time-integrated fluences are
shown for Best UW calculation,
adjusted yield, and SOMBRERO.
•The presence of Au in the NRL
targets adds emission in spectral
region above a few keV.
•At higher yield the Au is more
important.
10
-2
-3
10-4
10-5
10
-6
10
-7
10
160 MJ
115 MJ
SOMBRERO
1
NRL-DD-43
NRL-DD-49
Fusion Technology Institute
University of Wisconsin - Madison
10
2
10
3
10
4
10
5
10
6
Photon Energy (eV)
NRL IFE Concepts Project
9/19/2000
16
X-ray Power Emitted from Target is Mostly from
Target Explosion in 1 ns Burst, but Laser History
is Apparent
UW Best
Adjusted Yield
X-ray Emission from 160 MJ NRL Laser Target
X-ray Emission from 115 MJ NRL Laser Target
103
10
X-ray Power (TW/cm2)
X-ray Power (TW/cm2)
103
2
101
10
10
0
10
101
10
-1
0
NRL-DD-43
10
20
Time (ns)
Fusion Technology Institute
University of Wisconsin - Madison
30
2
10
0
-1
0
NRL-DD-49
10
20
30
Time (ns)
NRL IFE Concepts Project
9/19/2000
17
X-ray and Ion Debris Yield Partitioning Not A strong
Function of Total Yield
Laser Energy (MJ)
Fusion Yield (MJ)
Added Energy (MJ)
X-Ray Yield (MJ)
Debris Yield (MJ)
Total Non-Neutronic Yield (MJ)
Fusion Technology Institute
University of Wisconsin - Madison
DD-43
DD-49
1.6
1.6
115.7
139.7
0
20
1.66 (8%)
2.33 (7.3%)
19.0 (92%)
29.7 (92.7%)
20.66
32.0
NRL IFE Concepts Project
9/19/2000
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