Highlights of ARIES-IFE Study Farrokh Najmabadi VLT Conference Call April 18, 2001 Electronic copy: ARIES Web Site:

 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 Management F. Najmabadi Les Waganer (Operations) Mark Tillack (System Integration) Program Management F. Najmabadi Les Waganer (Operations) Mark Tillack (System Integration) Advisory/Review Committees Advisory/Review Committees OFES Executive 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 Concepts Characterization 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 Driver 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 wall Solid wall with sacrificial layer Thick 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 Spectra NRL 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 temperatures Low gas pressure:More accurate calculation of wall loading & response Advanced engineered material Alternate wall protectionMagnetic 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 < 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 = 3x m (availability=0.85) Coolant at 500°C3-mm thick Carbon Chamber Wall Energy Front Evaporation heat flux B.C at incident wall Convection B.C. at coolant wall: h= 10 kW/m 2 -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°C 3-mm thick W Chamber Wall Energy Front Evaporation heat flux B.C at incident wall Convection B.C. at coolant wall: h= 10 kW/m 2 -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-17Li out in He Blanket Pb-17Li (70% of Thermal Power) He FW (30% of Thermal Power) ~50°C IHX Example Case:  For a  T FW of ~ °C, the average surface T wall 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