N. Alexander, D. Goodin, J. Hoffer, J. Kaae, T.K. Mau, A. Nobile,R. Petzoldt, D. Schroen-Carey, A. Schwendt,

W. Steckle, M. Tillack

Presented by Dan Goodin

March 8-9, 2001

Livermore, California

Update of IFE Target Fabrication, Injection, and Tracking

Target fabrication, injection, and tracking issues are being addressed in an integrated fashion

LLNL Close-Coupled HI Target

NRL RadiationPreheat Target

…. Presentation will briefly address the work being done for each issue

Target fabrication critical issues1) Ability to fabricate target materials2) Ability to fabricate them economically3) Ability to fabricate, assemble, fill and layer at required rates

Target injection critical issues4) Withstand acceleration during injection5) Survive thermal environment6) Accuracy and repeatability, tracking

A. Schmitt,

NRL

FY 2001 | FY 2002 | FY 2003 | FY 2004 | FY 2005 | FY 2006 | FY2007

Simplified Target Fab/Injection 5-Year Plan

Injection Accuracy and Tracking

Data, Anal. and Modeling

Target Fabrication

Studies, R&D, Proof of Principle

NRL Target Physics

Prel. Target Designs

Target Analysis(Continuing)

TargetBaseline Design(NRL)

Engineering Prototype Development

Upgrade to Cryo Cryo

Target InjectionIRE Plant Design

IRE Plant Design

1) Ability to fabricate target materials

…. Initial materials fabrication and evaluation programs for both direct and indirect drive IFE targets are underway.

Leveraging ICF fabrication experience Indirect drive targets

LANL is studying synthesis of metal doped organic foams

Direct drive targets Schafer is developing DVB foam

shells and seal coats GA is developing characterization

Technical planning meeting at GA 2/21/01 (GA/Schafer/LANL)

GA is depositing high-Z overcoat

Trimethylolpropane trimethacrylate foam

shell with ~1 m hydroxyethylcellulose

seal coat plus GDP, with ~300 Angstroms

of gold

10 mg/cc DVB foam (from Diana

Schroen-Carey)

1) Ability to fabricate target materials - high-Z overcoat

…. Need to pursue baseline approach– but always have backups!

Considerations: Target design (Z, smooth, uniform) Fabrication (ability to coat, cost) Layering (IR or Joule heating)

Permeation through gold could be too slow Current focus

Coat 300 Angstrom gold & measure permeation Evaluate alternatives/backups

Injection (stable, reflective) ES&H (hazardous, mixed waste)

Gold deposited with columnar

structure or pinholes can be

permeable

Calculated Time to Fill Through High-Z OvercoatTemp. (K)Pd Ta V Nb

300 4.4 hrs 50 days 1.3 yrs 6.6 yrs373 1.4 hrs 10 days 60 days 0.44 yrs

Based on bulk metal properties only (no pinholes) and 0.047 atm overpressure

2) Ability to fabricate targets economically – utilizing industrial technologies

Industrial technologies are being evaluated

Fluidized bed is one mass-production technology

Several runs for GDP coating have shown good results (GA)

Can the concept be applied to cryogenic layering?(GA, Schafer)

Coating

MandrelCOLD HELIUM

FLUIDIZED BED WITH GOLD PLATED (IR REFLECTING) INNER WALL

INJECT IR

Fluidized BedConcept for

Layering

PAMS Mandrels in Fluidized Bed

2) Ability to fabricate targets economically – chemical process modeling and cost estimating

…. Scaleup of existing bench scale processes will be evaluated using chemical plant design software (Aspen Plus)

…. Workshop on target fabrication facility equipment and cost estimates being planned (GA, LANL, LLNL, UCSD, …)

1

WATER-1

B1

S1

B3

OIL-1 S4

B4

B5

S2

S3

S5

Stream HeatersInput Streams100 Liter PAMS Mandrel

PolymerizationReactor

Water Decant Stream

B8

S 8

S 9

PAMS Mandrel/Water Separator

Shell Water WashB6

Ethanol Extraction

S 6

S 7

B9

B10

AIR-1

S 11

S 12

Fluidizd BedPI or GDP

Coat Capsule

S 13

B11

Fluidized BedDrier

S 14

Capsule Manufacture

S 10

S 15

S 16

Flowsheet prepared by LANL

2.0

2.22.42.62.8

3.03.2

3.43.63.8

0% 5% 10% 15% 20% 25% 30% 35%

Void

Beta-layering

IR-layering

Total inventory

3) Ability to fabricate, assemble, fill, and layer at required rates – high volume filling

• Permeation filling is demonstrated technology from ICF- Void volume reduction (LANL)

Large Batch Permeation

Direct Injection

• Alternative fill techniques (GA)- Direct injection of liquid DT- Fast filled liquid target

LANL Calculations of Total DT Inventory for Direct Drive Targets Filled at 340K

NEEDLE

JET PIERCE

Target injection critical issues

Target injection is pursuing the Experimental Plan developed in FY99

“Experimental Plan for IFE Target Injection & Tracking”, GA-C23241 (Oct, 1999)

Program is a combination of

-analyses & modeling -materials property meas. -demonstrations

…. Ultimate goal is demonstration of injecting cryogenic targets into hot chamber

4) Withstand acceleration during injection –materials measurements are needed

• Have estimated DT can withstand 1000g acceleration at 18K- But based on hydrogen properties

extrapolated in both isotope and in temperature

• Need to measure DT yield strength and modulus under representative conditions- Correct crystalline form- Function of temperature- Function of time (3H -> 3He + )

• Planning meeting at NRL February 7, 2001- GA, LANL, NRL, Schafer- Reviewed objectives & requirements- LANL is developing detailed

measurement approachRef: Krupskii, I.N., Soviet J.

Low Temp. Phy. 3, 453, 1977

POSITION SENSOR

LOAD SENSOR

QUARTZ ROD

HEATERS

TEMPERATURE SENSORS

LHE JACKET (VACUUMINSULATED)

BELLOWS

VARIABLE CONDUCTANCEJACKET (GAS FILLED)

DT SAMPLE

5) Survive the thermal environment –indirect drive target thermal calculations

• ANSYS finite element model for indirect drive target- LLNL close coupled heavy ion driven target- 30 ms acceleration with 300K surface temperature- 30 ms coasting phase at 100 m/s- 30 ms in-reactor phase assuming 930K and 90 reflectance

• Results show negligible DT heating during injection

15

17

19

21

23

25

27

29

0 0.5 1 1.5 2 2.5 3 3.5 4

Distance from top surface, mm

18 K

Close Coupled Heavy IonInjection at 100 m/sReflection is 90%

Outer Hohlraum Surface

DT Fuel Capsule

5) Survive the thermal environment –direct drive target “success pathways”

TargetSurvival

TargetSurvival

“Survival” Criteria?

Reflectivity

Target Protection-Sabot in chamber-Injection Tube (UW)

Transmission

Criteria/concernsHigh reflectivityPermeation fillingTarget physics

Wall damageWasteMaterials CostComplexity

DT absorptionCH absorptionTarget Physics

Heating due to thermal radiation and from conduction/convection from the chamber gas

Review Status

and Plans

Preliminary Calculations

Experimental Data

Next Presentation (Alexander)

0

1

2

3

4

5

6

7

8

9

10

0 200 400 600 800 1000

Injection Velocity, m/s

Total Heat Flux, W/cm^2

0.05 torr of Xe

Whitaker Equation

Vacuum, 98% Reflectivity

0.05 torr of Xe

DSMC flow simulation method

Subsonic

Whitaker Valid

Supersonic

Whitaker Invalid

5) Survive the thermal environment –heating of a highly reflective direct drive target

Brief historical review:1. Thermal radiation heat flux from blackbody

spectrum (98% reflectance)2. Convective heat flux with “corrected”

Whitaker equations3. ANSYS model to estimate DT response4. Survival (Failure) criteria defined

- “At-risk” when yield stress is reached- “Failure” assumed at triple point- Need surface heat flux <1 W/cm2

5. DSMC code utilized for more accurate convective heating calculations

6. Conclusion: Reference SOMBRERO conditions unusable

1485°C

18

18.5

19

19.5

20

20.5

21

21.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Heat Flux, W/cm^2

Outer Ablator Temperature, K

At Risk Region

Failure

200 m/s

400 m/s

1000 m/s

2

7

12

17

22

0 50 100 150 200

Angle from leading edge, Degrees

Heat Flux, W/cm^2

400 m/s

200 m/s

100 m/s

Gas Temperature - 1485 CGas Pressure - 0.5 torr (300 K)Target Diameter - 3.902 mm

5) Survive the thermal environment –direct drive targets have a design window

ANSYS Flotran Calculations

Excessive heating

Excessive heating

Asymmetric heating

Asymmetric heating

1. Lower first wall temperatures2. Lower gas pressures

1. Lower first wall temperatures2. Lower gas pressures

Assumes 98% target surface reflectivity

Assumes 98% target surface reflectivity

5) Survive the thermal environment –removing the chamber gas widens the “window”

Conclusions: 1) Analyses of target heating are well in-hand2) Most important issues are:

- Response of the DT to rapid heat flux- Ability to fabricate highly reflective targets

3) It’s time for some data!

5) Survive the thermal environment –experiment on response of DT to a rapid heat flux

• Based on prior experiments done for ICF- Equipment available at LANL

• Cryogenic torus effectively turns the target “inside-out” – exposing the DT ice inner surface for viewing

• Experiment planning meeting at NRL on February 7, 2001 (LANL, GA, Schafer, NRL)

• Experimental equipment being evaluated/designed at LANL

Side view, cross-section of LANL cryogenic torus

(windows not shown)

DT/Foam Layer

Foam cast in torus

Exposed DT

5) Survive the thermal environment –data on gold overcoating reflectivity

• Deposited gold layers on 1 m of GDP (flats for now, spheres next)• Measured optical properties with ellipsometry• Calculated reflectivity as function of wavelength and angle of incidence• Calculated overall reflectivity for a given blackbody spectrum• Calculated the corresponding heat flux and compared to the 2-level criteria

for survival

0.75

0.8

0.85

0.9

0.95

1

700 900 1100 1300 1500

Wall Temperature (C)

Ref

lect

ivit

y

Gold thickness = 100 Å

300 Å500 Å900 Å

From T. K. Mau, UCSD

5) Survive the thermal environment –transmission may be a viable option

• Evaluated IR absorption bands for DT vs. blackbody radiation spectrum• Calculated bulk heating of DT assuming normal incidence• Results show low DT absorption

6) Accuracy and repeatability, tracking - experimental target injection and tracking system

A gas-gun is selected as a demonstrated technology to acquire injection/tracking data

• Strategy and approach– Acquire proof-of-principle data on target injection as soon as possible (RT

first, then cryo)– Provide a facility to aid in developing practical, survivable targets– Develop and demonstrate injection and tracking technologies suitable for

an IFE power plant– Prototype concepts and designs for application in an IRE

• Conceptual design was completed in CY00; final design in 2001

Direct drive target sabotDirect drive target sabot

Summary and conclusions

• Demonstrating a credible pathway for mass-production of IFE targets:– Five-year plan– Proof-of-principle fabrication steps being taken– Issues, e.g., gold permeability, being examined and backups developed– Industrial mass-production technologies being evaluated– Chemical process modeling and fab facility cost estimates started– High-volume filling methods being studied in detail

Target Fabrication

Target Injection

• Analyses of target survival during injection have shown “success windows”- Next step is acquisition of data on DT response and reflection

• Design of an injection and tracking system is proceeding as planned– Conceptual design review completed with minor comments

…. Significant progress is being made towards demonstrating practical and self-consistent scenarios for target fabrication and injection