Highlights of ARIES-IFE Study

Farrokh Najmabadi

VLT Conference Call

April 18, 2001

Electronic copy: http://aries.ucsd.edu/najmabadi/TALKS

ARIES Web Site: http://aries.ucsd.edu/ARIES

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

We Use a Structured Approach to Assess 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).

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

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

*

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

• 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

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

Drive Spectra (Vacuum Chamber)• 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 • Wall Survives!

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

Drive Spectra (Vacuum Chamber)

• 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

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