ARIES Team Activities

Farrokh Najmabadi

VLT PAC Meeting

December 4-5, 2000UCLA

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

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

Highlights of ARIES Team activities

Progress in ARIES IFE study

Plans for the coming year.

Outline

August 2000: Peer review of ARIES Program

• Review went very well. Presentations to the Peer Review committee is available in ARIES Web site. OFES will release synopsis of reviewer's reports.

• Review Panel made several good recommendation to better inform the community of ARIES research:

* Better organization of ARIES Web site for easy access to ARIES publications: Already implemented. We have also added a monthly “featured research” item.

* More seminars & presentations in the fusion laboratories specially those on detailed work to engage specialists.

* Re-institution of ARIES review committees in addition to the town meetings.

Highlights of ARIES Team Activities

October 2000: ARIES-AT technical work completed

• Documentation in progress. Final report is to be published in J. of Fusion Eng. & Design.

• Paper at IAEA Fusion Energy Conference.

• Nine papers, including a plenary presentation at ANS topical meeting .

October 2000: ARIES Fusion Neutron Source Study completed and documented (available on ARIES Web site).

October 2000: Most of the ARIES technical activity is focused on ARIES-IFE which was initiated in parallel to ARIES-AT in July 2000.

Highlights of ARIES Team Activities

January 2000: International workshop on SiC composites sponsored jointly by ARIES Team & US material community:

• Very useful meeting which brought designers and material scientists together.

• Workshop summary is published in J. of Fusion Eng. & Design.

March 2001: ARIES town meeting on fueling & tritium systems:

• Wide participation by both MFE & IFE communities,

• Attendance from EU and Japan is expected.

March 2001: Japan/US workshop on power plant studies and advanced technologies with participation of EU and China

• Meeting of IEA task group on safety and economic of fusion power.

ARIES Team Town Meetings & Workshops

Highlights of ARIES Team activities

Progress in ARIES IFE study

Plans for the coming year.

Outline

Analyze & asses 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 experiments needed to complete the database

ARIES Integrated IFE Chamber Analysis and Assessment Research -- Goals

Project Organization

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)

• Materials (ANL)

• Tritium (ANL, LANL*)

• Drivers* (NRL*, LLNL*, LBL*)

• Chamber Eng. (UCSD, UW)

• CAD (UCSD)

• Target Physics (NRL*, LLNL*, UW)

• Chamber Physics (UW, UCSD)

• Parametric Systems Analysis (UCSD, BA, LLNL)

• Safety & Env. (INEEL, UW, LLNL)

• Neutronics, Shielding (UW, LLNL)

• Final Optics & Transport (UCSD, NRL*,LLNL*, LBL)

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

Approach

Six classes of target were identified. Advanced target designs from NRL and LLNL are used as a starting point – both direct-drive and indirect drive designs.

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).

Initial Results of ARIES IFE Study

1. Characterization of Target Yield: New, accurate knowledge of target output (X-rays, debris, neutrons) has established protection requirements.

2. Characterization of Chamber Response:

a. Power loads on the chamber walls are identified.

b. Engineered chamber surfaces may expand the design window.

c. Safety considerations restrict the design window & choices.

3. Target injection. Need to establish chamber environment that is consistent with both first wall protection and target injection and tracking.

4. Driver/chamber interface. Laser optics compatible with the chamber environment as well as propagation of ion beams in dry chambers are being studied.

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

Ion Spectra from Reference Direct and Indirect Target Designs

Slow Ions:

Fast Ions:

Characterization of Chamber Response: Power & Particle Loading on the Chamber Wall

• NRL advanced direct-drive targets with output spectra from LLNL & NRL target codes;

• 6.5-m radius chamber (in vacuum)

• Most of heat flux due to fusion fuel and fusion products.

Characterization of Chamber Response: X-ray Loading on the Chamber Wall

Xe Density (Torr)

Ion Energy

Deposited in Gas (MJ)

Ion Energy

deposited in wall (MJ)

X-ray Energy

Deposited in gas (MJ)

X-ray Energy

Deposited in Wall

(MJ)

Vaporized Wall mass

(g)

0.05 24.9 4.8 0.6 1.7 3000.1 28 2 0.8 1.5 10

0.15 28.2 1.5 1 1.3 00.3 28.7 0.95 1.1 1.2 0

• A sequence of BUCKY runs varying the Xe density were per-formed for the NRL target in a 6.5m radius graphite chamber

• Assumed Target Yields: Ions 29.7 MJ, X-rays 2.33 MJ.

• 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

Pyrolytic carbon at 1278˚C:k 400 W/m-K2250 kg/m3

Cp 1900 J/kg-K

Characteristic Diffusiontime length

Prompt X-ray pulse 0.1 ns 0.1 mFiber diameter 10-30 m 1-10 mReradiation pulse 100 s 100 m

= k/Cp

= L2/

L

y

d

incident energy

Enhanced thermal behavior results from extended

surface, short diffusion time, & semi-transparency

• Thermal performance, erosion, plugging and material transport need to be studied

Af/A = 4/ (1- ) L/d~5 for the ESLI material

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

Heating of Direct-Drive Targets Limits Wall Temperature & Gas Pressure

Chamber-based solutions:Low gas pressureLow wall temperatureAlternate wall protection

Target-based solutions:Sabot or wake shieldFrost coating

Failure criteria:• triple point• stress

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 of </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

• Damage that increases absorption (<1%)

• Damage that modifies the wavefront –

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

Two main concerns:

Mirrors and transmissive wedges are considered

Fused silica or CaF2 wedges

85Þ

stiff, lightweight, actively cooled, neutron transparent substrate

1 m

11.5 m

Grazing incidence metal mirror

= 80-85˚Transverse energy 10-20 J/cm2

Reflectivity Degradation of Damaged or Contaminated Mirrors Is Being Investigated

0.75

0.8

0.85

0.9

0.95

1

Ref

lect

ivit

y

0 10 20 30 40 50 60 70 80 90

Angle of incidence

Aluminum reflectivity at 532 nm

s-polarized

p-polarized

Concerns include absorption, scattering, interference effects Thin protective coatings (not “tuned” multi-layer coatings) also

under review

0

0.25

0.5

0.75

1

Ref

lect

ivit

y0 0.2 0.4 0.6 0.8 1

Al2O3 Coating thickness (h/)

0Þ

60Þ

85Þ

1 m thick dry wall chamber provides lifetime protection for ceramic insulators of adiabatic lens and chamber wall

In addition to blanket, 35 cm thick local shield is needed to protect FF magnets against radiation

Placing final optics at > 25 m from target alleviates damage by streaming source neutrons

Magnet shielding is an important driver-chamber interface concern for Heavy-ion drivers

Fusion Technology InstituteUniversity of Wisconsin - Madison

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)

• Highlights of ARIES Team activities

• Progress in ARIES IFE study

• Plans for the coming year.

Outline

* ARIES resources include 35k in FY00 & 70k in FY01 devoted to socioeconomic work (not included in socioeconomic total).

Distribution of Advanced Design Research

1,894*

27050

FY00: 2,214k FY00: 2,225k45

480

1700*

Excellent progress up to date.Excellent progress up to date.

Regular presentations and participation by IFE scientists who Regular presentations and participation by IFE scientists who are not funded by the ARIES program. ARIES program has are not funded by the ARIES program. ARIES program has become an umbrella to share the latest results in IFE technology become an umbrella to share the latest results in IFE technology and discuss trade-offs and issues.and discuss trade-offs and issues.

We will continue with our Research PlanWe will continue with our Research Plan

For FY01, 200k of resources shifted to socioeconomic work.For FY01, 200k of resources shifted to socioeconomic work.

Cuts hurts in two major areas:Cuts hurts in two major areas:

• GA budget is zeroed out. No target injection, tracking, and GA budget is zeroed out. No target injection, tracking, and fabrication expertise in the ARIES program.fabrication expertise in the ARIES program.

• LLNL budget is cut by 50%.LLNL budget is cut by 50%.

ARIES Team meeting on Dec. 6-8 will consider how to deal ARIES Team meeting on Dec. 6-8 will consider how to deal with these cuts.with these cuts.

Plans for FY01 ARIES IFE