Summary of Research in theAdvanced Energy Technology Group

at UC San Diego

Farrokh Najmabadi and Mark Tillack

March 2004

http://aries.ucsd.edu

Our Research Staff and Students

Sophia Chen graduate student Electrical & Computer Engineering

Brian Christensen graduate student Mechanical & Aerospace Engineering

Kevin Cockrell undergraduate Electrical & Computer Engineering

Zoran Dragojlovic project scientist Electrical & Computer Engineering

Andres Gaeris project scientist Electrical & Computer Engineering

S. S. Harilal project scientist Electrical & Computer Engineering

Tak Kuen Mau research scientist Electrical & Computer Engineering

Farrokh Najmabadi professor Electrical & Computer Engineering

Beau O’Shay graduate student Electrical & Computer Engineering

John Pulsifer engineer Center for Energy Research

René Raffray research scientist Mechanical & Aerospace Engineering

Kevin Sequoia graduate student Mechanical & Aerospace Engineering

Dai Kai Sze research scientist CER/MAE

Mark Tillack research scientist Mechanical & Aerospace Engineering

Phyllis Voigts administrative specialist

Center for Energy Research

Xueren Wang engineer Center for Energy Research

Summary of Research Activities

• ARIES Fusion Concept Studies• High Average Power Laser Program

– final optics– chamber clearing– dry-wall armor thermomechanics– cryogenic target survival

• Inertial Fusion Energy Chamber Physics– magnetic diversion of ablation plumes– phase change physics

• Laser-Matter Interactions– laser ablation plume dynamics and cluster formation– laser plasma EUV light source

• Thermal Sciences

1. ARIES Fusion Concept Studies

The ARIES Team has examined several magnetic and inertial fusion power plant

concepts during the past 15 years

• TITAN reversed-field pinch (1988)

• ARIES-I first-stability tokamak (1990)

• ARIES-III D-3He-fueled tokamak (1991)

• ARIES-II and -IV second-stability tokamaks (1992)

• Pulsar pulsed-plasma tokamak (1993)

• SPPS stellarator (1994)

• Starlite study (1995) (goals & technical requirements for power plants & Demo)

• ARIES-RS reversed-shear tokamak (1996)

• ARIES-ST spherical tokamak (1999)

• ARIES-AT advanced tokamak (2001)

• ARIES-IFE IFE chamber studies (2003)

• ARIES-CS compact stellarator (ongoing)

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Concept studies incorporate customer require-ments and the existing database to assess concepts, innovate, and guide the

base program Customer Input

Missionand Goals

Evaluation Based on Customer Attributes

Attractiveness

Characterizationof Critical Issues

Feasibility

Design Options

Assessment

Present Data Base

Redesign R &D Needs,Development Plan

Concept Studies

R&D Program

Objectives:

Analyze & assess integrated and self-consistent IFE chamber concepts

Understand trade-offs and identify design windows for promising concepts. The research was not aimed at developing a point design.

Approach:

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

To make progress, the activity was divided based on 3 chamber classes:• Dry wall chambers;• Solid wall chambers protected with a “sacrificial zone” (such as

liquid films); • Thick liquid walls.

These classes of chambers were researched in series with the entire team focusing on each.

ARIES integrated IFE chamber analysis and assessment research was a 3-year exploration study, recently completed

History of the UCSD IFE program

1997 1998 1999 2000 2001 2002 20032004

OFES proposal lab YAG Stafframp-up

excimerlaser

vacuumsystem new lab

LLNL-funded studies of chamber simulationexperiments

OFES grant on chamber physics, modified to address final optics

ARIES-IFE

DP HAPL programs

GA target engineering

OFES grant on chamber physics (terminated)

dry walls liquid walls

2. High Average Power Laser Program

Our IFE research is focused on the key issues for IFE chambers and chamber

interfaces

Prometheus-L Reactor Building• Final optics that survive the environment

• Understanding of residual chamber medium and propagation of targets and beams through it

– Chamber dynamic response, chamber clearing

– Beam & target interactions

• Chamber walls that survive or are renewable

• Cryogenic targets that survive injection

We are developing damage-resistant final optics based on grazing-incidence metal

mirrors

cubedumpcube1/2 waveplatebeam diagnosticsdumpviewing portspecimenmount

Objectives:• Measure laser-induced damage

threshold and demonstrate long-term operation of a grazing incidence metal mirror at laser fluence of ~5 J/cm2 normal to the beam.

• Determine limits due to contamination & other target threats.

• Determine effects of damage on beam quality.

The SPARTAN chamber dynamics and clearing code was developed for studies of

the post-blast chamber environment

• 2-D Transient Compressible Navier-Stokes Equations.

• Second order Godunov method, for capturing strong shocks.

• Diffusive terms (conductivity, viscosity) depend on local state variables.

• Adaptive Mesh Refinement for uniform accuracy throughout the fluid domain.

• Arbitrary boundary resolved with Embedded Boundary method.

Cyclic thermomechanical behavior of dry-wall chamber armor is under

investigation

Temperature is calculated from measurement of radiated energy at two wavelengths:

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A fast (nanosecond) optical thermometer was developed to assist the project with time-resolved surface response measurements

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0 1 2 3 4 5 6 7 8 9 10

Heat Flux (W/cm2)

Vapor Thickness (m)

Rigid, tv_o = 1e-6 m

Rigid, tv_o = 3e-6 m

Bending, tv_o = 1e-6 m, ro = 5e-6 m

Bending, tv_o = 3e-6 m, ro= 5e-6m

Bending, tv_o = 1e-6 m, ro = 7e-6 m

+

Survival of cryogenic direct-drive targets in hot, turbulent chambers is a challenging

problem

Pre-existing vapor bubbles could close if initial bubble is below a critical size and the heat flux above a

critical value

t = 0.015 s

Tinit = 18 K

DT Vapor Core

Plastic Shell

Local Vapor Bubble

Rigid DT Solid

tv,o

ro

Thermal, mechanical and phase change studies were performed on cryogenic DT targets subjected to chamber heating

3. Inertial Fusion Energy Chamber Physics

Magnetic diversion of expanding laser plasma is being studied as a possible

means to mitigate target debris

Phase change physics is important for under-standing the generation of impulse

and behavior of aerosols in liquid-protected IFE chambers

• Homogeneous nucleation and growth from the vapor phase

– Supersaturated vapor

– Ion-seeded vapor

– Impurity-seeded vapor

• Phase decomposition from the liquid phase

– Thermally driven phase explosion

– Pressure driven fracture

• Hydrodynamic droplet formation (flow conditioning)

Spinodal decomposition of Si (Craciun)

4. Laser-Matter Interactions

Laser ablation plume dynamics is extremely complex, involving laser interactions, phase change, gasdynamics, atomic and plasma

physics

0.01 Torr

1 Torr

0.1 Torr

10 Torr

100 Torr

Ionization was shown to play a dominant role in nanocluster formation in laser ablation

plumes

5x109 W/cm2

Polyimide laser ink-jet printer head (courtesy of HP)

We recently began a program of research on next-generation

semiconductor lithography based on laser-plasma EUV emission

Achieving higher efficiency and lower contamination are key issues for EUV light sources

5. Thermal Sciences

Studies of heat transfer enhancement techniques are equally important in high heat

flux applications (like fusion) and energy efficiency

• Heat transfer in porous and granular media– Energy recovery ventilator– High heat flux devices

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are needed to see this picture.Coaxial heat exchanger

di

Di

t

di = 1.936 inches

t = 0.032 inchesDi = 3.068 inches

Conductive Wall (Alloy 122 Copper Tubing)

Insulated Wall (3 in PVC pipe)

Hot Stream (packed with porous media)

Cold Stream (packed with porous media)

UCSD Laser Plasma and Laser-Matter Interactions

Laboratory