Analyze & assess integrated and 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 zeroth order, i.e., does it make or break the concept?

• Start defining needed experiments and simulation tools.

ARIES Integrated IFE Chamber Analysis and Assessment Research -- Goals

ARIES-IFE Is a Multi-institutional Effort

Program ManagementF. Najmabadi

Les Waganer (Operations)

Mark Tillack (System Integration)

Program ManagementF. Najmabadi

Les Waganer (Operations)

Mark Tillack (System Integration)Advisory/Review

Committees

Advisory/Review

Committees

OFESOFESExecutive Committee

(Task Leaders)

Executive Committee

(Task Leaders)

Fusion

Labs

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)

Tasks

* voluntary contributions

An Integrated Assessment Defines the R&D Needs

Characterization

of target yield

Characterization

of target yield

Target

Designs

Chamber

ConceptsCharacterization

of chamber response

Characterization

of chamber response

Chamber

environment

Chamber

environment

Final optics &

chamber propagation

Final optics &

chamber propagation

Chamber R&D:Data base

Critical issues

Chamber R&D:Data base

Critical issues

DriverDriver

Target fabrication,

injection, and tracking

Target fabrication,

injection, and tracking

Assess & Iterate

We Use a Structured Approach to Asses Driver/Chamber Combinations

To make progress, we divided the activity based on three classes of chambers:• Dry wall chambers;• Solid wall chambers protected with a “sacrificial zone” (such

as liquid films); • Thick liquid walls.

We plan to research these classes of chambers in series with the entire team focusing on each.

While the initial effort is focused on dry walls, some of the work is generic to all concepts (e.g., characterization of target yield, target injection and tracking, etc).

Status of ARIES-IFE Study

Six classes of target were identified. Advanced target designs from NRL (laser-driven direct drive) and LLNL (Heavy-ion-driven indirect-drive) are used as references.

Detailed output spectrum from these targets are calculated and used for analysis of other systems.

Analysis of design window for successful injection of direct and indirect drive targets in a gas-filled chamber (e.g., Xe) is completed.

Final focus and transport is under study:

• Grazing incident metal mirrors for lasers.

• Focusing magnets for heavy ions and beam transport in a “high-pressure” chamber.

Status of ARIES-IFE Study

Six combination of target spectrum and chamber concepts are under investigation:

Nearly Complete,

Documentation

Direct drive

target

Work started

in March 2001

Dry wallSolid wall with

sacrificial layerThick Liquid Wall

Indirect drive

target

Work started

in March 2001

* Probably will not be considered because of large number of penetrations needed

*

Backup Material

Reference Direct and Indirect Target Designs

NRL Advanced Direct-Drive Targets

DT Vapor0.3 mg/cc

DT Fuel

CH Foam + DT

1 m CH +300 Å Au

.195 cm

.150 cm

.169 cm

CH foam = 20 mg/cc

DT Vapor0.3 mg/cc

DT Fuel

CH Foam + DT

5 CH

.122 cm

.144 cm

.162 cm

CH foam = 75 mg/cc

1

10

100

1000

0 5 10 15time (ns)

laser power •NRL Direct Drive Target Gain Calculations (1-D) have been corroborated by LLNL and UW.

LLNL/LBNL HIF Target

Energy output and X-ray Spectra from Reference Direct and Indirect Target Designs

NRL Direct Drive Target (MJ)

HI Indirect Drive Target (MJ)

X-rays 2.14 (1%) 115 (25%)

Neutrons 109 (71%) 316 (69%)

Gammas 0.0046 (0.003%) 0.36 (0.1%)

Burn product fast ions

18.1 (12%) 8.43 (2%)

Debris ions kinetic energy

24.9 (16%) 18.1 (4%)

Residual thermal energy

0.013 0.57

Total 154 458

X-ray spectrum is much harder

for NRL direct-drive target

X-ray and Charged Particles SpectraNRL Direct-Drive Target

1. X-ray (2.14 MJ)

2. Debris ions (24.9 MJ)

3. Fast burn ions (18.1 MJ)(from J. Perkins, LLNL)

3

1

2

Ion Spectra from Reference HI-Driven Indirect –Drive Target

Slow Ions

Fast Ions

• 1992 Sombrero Study highlighted many advantages of dry wall chambers.

• General Atomic calculations indicated that direct-drive targets do not survive injection in Sombrero chamber.

A Year Ago, Feasibility of Dry Wall Chambers Was in Question

Target injection Design Window Naturally Leads to Certain Research Directions

Chamber-based solutions:Low wall temperature: Decoupling of first wall & blanket temperaturesLow gas pressure: More accurate calculation of wall loading & response

Advanced engineered materialAlternate wall protection Magnetic diversion of ions*

Target-based solutions: Sabot or wake shield, Frost coating* * Not considered in detail

Target injection window

(for 6-m Xe-filled chambers):

Pressure < 10-50 mTorr

Temperature < 700 C

Variations in the Chamber Environment Affects the Target Trajectory in an Unpredictable Way

• Forces on target calculated by DSMC Code

•“Correction Factor” for 0.5 Torr Xe pressure is large (~20 cm)

• Repeatability of correction factor requires constant conditions or precise measurements

• 1% density variation causes a change in predicted position of 1000 m (at 0.5 Torr)

• For manageable effect at 50 mTorr, density variability must be <0.01%.

• Leads to in-chamber tracking

Ex-chamber tracking system

• MIRROR R 50 m

• TRACKING, GAS, &• SABOT REMOVAL • 7m

• STAND-OFF • 2.5 m

• CHAMBER • R 6.5 m • T ~1500 C

• ACCELERATOR • 8 m • 1000 g • Capsule velocity out 400 m/sec

• INJECTOR • ACCURACY

• TRACKING • ACCURACY

• GIMM R 30 m

Photon and Ion Attenuation in Carbon and Tungsten

10.0x103

1.0x105

1.0x106

1.0x107

1.0x108

1.0x109

1.0x1010

1.0x10-6 1.0x10-5 1.0x10-4 1.0x10-3 1.0x10-2

Penetration Depth (m)

Photons, C

Photons, W

Fast ions, C

Fast ions, W

Debri ions, C

Debri ions, W

Temporal Distribution of Energy Distribution from

Photons and Ions Taken into Account

Time (ns)

Fu

sio

nP

ow

er

(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

From R. Peterson and D. Haynes’s presentation At ARIES meeting September 2000.

Example Photon Temporal Distribution

Temporal Distribution for Ions Based on Given Spectrum and 6.5 m Chamber

0.0E+00

1.0E+13

2.0E+13

3.0E+13

4.0E+13

5.0E+13

6.0E+13

Th

erm

al P

ower

(W

)

0.0E+00 1.0E-06 2.0E-06 3.0E-06 4.0E-06 5.0E-06

Time (s)

Time-of-Flight Ion Power Spread

C12(KE)

He4(KE)

He4(PB)

P(BP)

T(BP)

D(BP)

P(KE)

T(KE)

D(KE)

Debris Ions

Time10ns 0.2s 1s 2.5s

FastIonsP

hot

onsEnergy

Deposition

• Dramatic decrease in the maximum surface temperature when including temporal distribution of energy deposition- e.g. Tmax for carbon reduced from ~6000°C to ~1400°C for a case with constant kcarbon (400 W/m-K) and without protective gas, presented at the Dec. 2000 ARIES meeting

Example Temperature History for Carbon Flat Wall Under Energy Deposition from NRL Direct-

Drive Spectra• Coolant temperature = 500°C

• Chamber radius = 6.5 m

• Maximum temperature = 1530 °C

• Sublimation loss per year = 3x10-13 m (availability=0.85)

Coolant at 500°C3-mm thick Carbon Chamber Wall

EnergyFront

Evaporation heat flux B.C at incident wall

Convection B.C. at coolant wall:h= 10 kW/m2-K

Summary of Thermal and Sublimation Loss Results for Carbon Flat Wall

Coolant Temp. Energy Deposition Maximum Temp. Sublimation Loss Sublimation Loss

(°C) Multiplier (°C) per Shot (m) per Year (m)*

500 1 1530 1.75x10-21 3.31x10-13

800 1 1787 1.19x10-18 2.25x10-10

1000 1 1972 5.3x10-17 1.0x10-8

500 2 2474 6.96x10-14 1.32x10-5

500 3 3429 4.09x10-10 7.73x10-2

* Shot frequency = 6; Plant availability = 0.85

• Encouraging results: sublimation only takes off when energy deposition is increased by a factor of 2-3

• Margin for setting coolant temperature and chamber wall radius, and accounting for uncertainties

Example Temperature History for Tungsten Flat Wall Under Energy Deposition from NRL Direct-

Drive Spectra

• Coolant temperature = 500°C• Chamber radius = 6.5 m• Maximum temperature = 1438 °C

Coolant at 500°C3-mm thick W Chamber Wall

EnergyFront

Evaporation heat flux B.C at incident wall

Convection B.C. at coolant wall:h= 10 kW/m2-K

Key issue for tungsten is to avoid reaching the melting point = 3410°C

W compared to C:• Much shallower energy deposition from photons • Somewhat deeper energy deposition from ions

Example Temperature History for Tungsten Flat Wall Under 5 x Energy Deposition from

NRL Direct-Drive Spectra• Illustrate melting process from W; melting point = 3410°C• Include phase change in ANSYS by increasing enthalpy at melting point to

account for latent heat of fusion (= 220 kJ/kg for W)• Melt layer thickness ~ 1.2 m Separation = 1 m

Summary of Thermal Results for Tungsten Flat Wall

Coolant Temp. Energy Deposition Maximum Temp.

(°C) Multiplier (°C)

500 1 1438

800 1 1710

1000 1 1972

500 2 2390

500 3 3207

500 5 5300

• Encouraging results: melting point (3410°C) is not reached even when energy deposition is increased by a factor of 3

• Some margin for setting coolant temperature and chamber wall radius, and accounting for uncertainties

An Efficient Dry-laser IFE Blanket With Low Wall Temperature Is Possible IFE dry-wall blanket example: ARIES-AT blanket. First wall

coated with C armor and is cooled by He. Coupled to advanced Brayton Cycle

Power loadings based on NRL targets injected at 6 Hz.

30% of power is in the first wall.

Blanket(e.g.

ARIES-AT)

Sep.FW

Pb-17Lioutin

He

BlanketPb-17Li (70% of Thermal Power)

He

FW (30% of Thermal Power)

~50°CIHX

Example Case: For a TFW of ~100-150°C, the

average surface Twall at target injection can be lowered to ~600°C while maintaining a cycle efficiency of 50%

Initial Results from ARIES-IFE have Removed Major Feasibility Issues of Dry Wall Chambers

Research is now focused on Optimization And Attractiveness

Trade-off studies are continuing to fully characterize the design window. We are analyzing response of the chamber to Higher target yields Smaller chamber sizes Different chamber wall armor

Un-going activities in: Engineered Material, Effect of chamber environment on target trajectory Final optics Safety

• Good parallel heat transfer, compliant to thermal shock

• Tailorable fiber geometry, composition, matrix

• Already demonstrated for high-power laser beam dumps and ion erosion tests

• Fibers can be thinner than the x-ray attenuation length.

Advanced Engineered Materials May Provide

Superior Damage Resistance

Carbon fiber velvet in carbonizable substrate 7–10 m fiber diameter1.5-2.5-mm length1-2% packing fraction

Laser-Final Optics Threat Spectra

Final Optic Threat Nominal Goal

Optical damage by laser >5 J/cm2 threshold (normal to beam)

Nonuniform ablation by x-rays Wavefront distortion </3 (~100 nm)Nonuniform sputtering by ions 6x108 pulses in 2 FPY:

2.5x106 pulses/atom layer removed

Defects and swelling induced Absorption loss of <1%by -rays and neutrons Wavefront distortion of < /3

Contamination from condensable Absorption loss of <1%materials (aerosol, dust, etc.) >5 J/cm2 threshold

Two main concerns: Damage that increases absorption (<1%) Damage that modifies the wavefront –

spot size/position (200m/20m) and spatial uniformity (1%)

85Þ

stiff, lightweight, actively cooled, neutron transparent substrate

1 m

11.5 m

Safety and Environmental Activities in ARIES-IFE Chamber Assessment

In-vesselActivation

Ex-vesselActivation

Waste Assessment

Waste Metrics

Energy Source Radiological and Toxic Release

Metrics

Evaluation

Decay Heat

Calculation

Tritium and ActivationProduct

Mobilization

Debris or Dust

ChemicalReactivity

ToxicMaterial

(Performed jointly by INEEL, UW, LLNL)