Fusion Technology Institute University of Wisconsin - Madison NRL IFE Concepts Project 9/19/2000 1...

9/19/2000

1

Fusion Technology InstituteUniversity of Wisconsin - Madison NRL IFE Concepts Project

Output Calculations for Laser Fusion Output Calculations for Laser Fusion TargetsTargets

ARIES MeetingARIES MeetingSeptember 18-20, 2000September 18-20, 2000Princeton UniversityPrinceton University

Robert R. Peterson and Donald A. HaynesUniversity of Wisconsin-Madison

9/19/2000

2


Laser Propagation:Breakdown

Variables Considered For Choosing the Cavity Gas Environment in SOMBRERO

Gas Opacity:Stop target x-rays and wall radiant heat

Stopping of Target Ions

Gas Atom Species

Density of Gas Atoms

Variables Considered For Choosing the Cavity Gas Environment in SOMBRERO

Neutron Activation of Gas

Target Injection

9/19/2000

3


Chamber Physics Critical Issues Involve Target Output, Gas Behavior and First Wall Response

Design,Fabrication,

Output Simulations,(Output Experiments)

Design,Fabrication,

Output Simulations,(Output Experiments)

Gas Opacities,Radiation Transport,

Rad-Hydro Simulations

Gas Opacities,Radiation Transport,

Rad-Hydro Simulations

Wall Properties,Neutron Damage,

Near-Vapor Behavior,Thermal Stresses

Wall Properties,Neutron Damage,

Near-Vapor Behavior,Thermal Stresses

X-rays,Ion Debris,Neutrons

Thermal Radiation,

Shock

Target Output Gas Behavior Wall Response

UW uses the BUCKY 1-D Radiation-Hydrodynamics Code to Simulate Target, Gas Behavior and Wall Response.

9/19/2000

4


BUCKY is a Flexible 1-D Lagrangian Radiation-

Hydrodynamics Code • 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

9/19/2000

5


Direct and Indirect Drive Targets Under Consideration Have Different Output

DT Vapor

DT Fuel

Foam + DT

1 CH + 300 Å Au

0.265g/cc

0.25 g/cc1.5 mm

1.69 mm

1.952 mm

DT Vapor

DT Fuel

Foam + DT

1 CH

0.265g/cc

0.25 g/cc1.22 mm

1.44 mm

1.62 mm

NRL Direct-drive LaserTargets May Contain High Z

Indirect-drive HIF and Z-pinchTargets Have High-Z Hohlraums

DT gas

DT iceBe98O2

BeO

He gas

Au

0

2 mm

6 mmX-1 TargetLLNL/LBNL HIF Target

9/19/2000

6


Original SOMBRERO Study Operated Under Substantially Different Target Assumptions Than Are Currently Used

Tmin (K) T Allowed (K)

Target Reflect-ivity

Wall Emis-sivity

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

9/19/2000

7


Target X-ray Spectrum

Direct-Drive Target Output is Dominated by Neutrons and Energetic Ablator Ions

Debris Ions 94 keV D - 5.81 MJ141 keV T - 8.72 MJ138 keV H - 9.24 MJ188 keV He - 4.49 MJ 1600 keV C - 55.24 MJTotal - 83.24 MJ per shot=15.68 J/cm2 on SOMBRERO Wall

X-Rays22.41 MJ per shot=4.22 J/cm2 on SOMBRERO Wall

Neutrons317 MJ per shot=59.7 J/cm2 on SOMBRERO Wall

SOMBRERO Target

DT gas

DT iceCH

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

9/19/2000

8


Bucky Target Implosion and Burn Calculations used to Study Target Output

•Bucky does not have zooming or detailed LPI, so laser deposition will not agree with codes that do.

•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.

Time (ns)

AbsorbedLaserPower(TW)

0 10 2010-1

100

101

102

NRL-DD-2NRL-DD-14

9/19/2000

9


Time (ns)

Position(mm)

0 0.5 1 1.5 21.9

1.925

1.95

1.975

2

2.025

2.05

2.075

2.1

NRL DD-3515 Au zones

Laser

Au

CH

DT-wetted Foam

Laser Quickly Burns though 300 Ǻ Au and 1 Plastic and Launches a Shock in DT-wetted Foam

9/19/2000

10


Time (ns)

Position(cm)

0 10 20 300

0.1

0.2

0.3

0.4

0.5

NRL DD-43

Au

CH

DT-wetted foam

DT

With Laser Pulse NRL-DD-14, Target Implodes and Ignites at 27.3 ns, giving 115 MJ of Yield

•22% of DT ice is burned; NRL and LLNL get about 32 %.

•Very little DT in wetted foam is burned.

•BUCKY burn fraction would be improved with further tuning.

•Target expands at a few x 108 cm/s and radiates.

9/19/2000

11


Radius (cm)

MassDensity(g/cm3)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.710-4

10-3

10-2

10-1

100

101

102

20 ns22 ns24 ns26 ns27 ns27.2 ns

NRL The rmally S moothe d Dire ct-Drive Las e r Targe t

NRL-DD-43 Time (ns)0 10 20

0

10

20

30

40

NRL-DD-43

115 MJ NRL Laser Target

Implosion Keeps In-Flight Aspect Ratio Less than 40; Convergence Ratio is About 9

9/19/2000

12


Time (ns)

FusionPower(TW)

23 24 25 26 27 28 29 30

10-3

10-2

10-1

100

101

102

103

104

105

106

NRL-DD-43

X-ray Emission from 115 MJ NRL Laser Target

Radius (cm)0 0.1 0.2

100

101

102

103

104

105

106

NRL-DD-43


At Bang Time = 27.3 ns

Most of Burn is in Cryogenic DT Ice and Takes Place in < 50 ps

9/19/2000

13


Ion Energy (eV)

NumberofIons

103 104 105 106 107 108 1091016

1017

1018

1019

1020 DTHCAuHe

NRL-DD-43

Ion Spectrum from 115 MJ NRL Laser Target

Ion Spectrum for UW Best Burn

Wetted Foam

Plastic

Au

DT Ice

DT Gas

SOMBRERO

•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.

9/19/2000

14


Ion Energy (eV)

NumberofIons

103 104 105 106 107 108 1091016

1017

1018

1019

1020 DTHCAuHe

NRL-DD-49

Ion Spectrum from 160 MJ NRL Laser Target

Wetted Foam

Plastic

Au

DT Ice

DT Gas

Ion Spectrum for UW Adjusted Burn

SOMBRERO

•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 non-neutronic, 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?).

9/19/2000

15


Radius (cm)

FinalChargeState

10 20 30

5

10

15

20

NRL-DD-49


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.

•At launch time (end of target explosion simulation), charge state is taken from data tables in temperature and density.

•The tables are calculated by the EOSOPA code in a Saha LTE method.

•The free electrons are assumed to move with the ions (quasi-neutrality).

•The greatly expanded target remnants are probably in Coronal Equilibrium or not in equilibrium at all.

9/19/2000

16


X-ray Spectra from Targets is Changed by High Z Components

•X-ray spectra are converted to sums of 3 black-body spectra. •Time-dependant spectra are in Gaussian pulses with 1 ns half-widths 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.

Photon Energy (eV)101 102 103 104 105 10610-7

10-6

10-5

10-4

10-3

10-2

10-1

160 MJ115 MJSOMBRERO

NRL-DD-43NRL-DD-49

X-ray Spectrum from 115 MJ and 160 MJ NRL and SOMBRERO Laser Targets

9/19/2000

17


Time (ns)

X-rayPower(TW/cm2)

0 10 20 3010-1

100

101

102

103

NRL-DD-49


Time (ns)

X-rayPower(TW/cm2)

0 10 20 3010-1

100

101

102

103

NRL-DD-43


X-ray Power Emitted from Target is Mostly from Target Explosion in 1 ns Burst, but Laser History

is Apparent

UW Best Adjusted Yield

9/19/2000

18


DD-43 DD-49

Laser Energy (MJ)1.6 1.6

Fusion Yield (MJ)115.7 139.7

Added Energy (MJ)0 20

X-Ray Yield (MJ)1.66 (8%) 2.33 (7.3%)

Debris Yield (MJ)19.0 (92%) 29.7 (92.7%)

Total Non-Neutronic Yield (MJ)20.66 32.0

X-ray and Ion Debris Yield Partitioning Not A strong Function of Total Yield

Date post:	21-Dec-2015
Category:	Documents
View:	216 times
Download:	0 times

Fusion Technology Institute University of Wisconsin - Madison NRL IFE Concepts Project 9/19/2000 1...

Documents