Top level overview of target fabrication tasks

High Average Power Laser Program Workshop

Princeton Plasma Physics Laboratory

October 27 and 28, 2004

Presented by

Dan Goodin

at the

1. What are we trying to do in Phase I?

2. What is the target design?

3. What are the basic target specifications?

4. How is the target fabricated?

5. What are the remaining issues?

6. What’s being done to address the issues?

Summary - target fabrication

1. Develop mass production methods to fabricate cryogenic DT targets that meet the requirements of the target design codes and chamber design. Includes characterization.

2. Combine these methods with established mass production costing models to show targets cost will be less than $0.25.

What are we trying to do in Phase I?

Address issues about the feasibility of the laser fusion target supply

Phase I goals for target fabrication:

A 1000 MW(e) power plant will operate at about 6 Hz - about 500,000 targets per day.

Some Expected Direct Drive Specifications

Capsule Material CH (DVB) foam

Capsule Diameter ~4-5 mm

Capsule Wall Thickness ~260 m

Foam shell density 100-120 mg/cc

Out of Round <1% of radius

Non-Concentricity <1% of wall thickness

Shell Surface Finish ~20 nm RMS

Ice Surface Finish <1 m RMS

Temperature at shot ~15 - 18K

Positioning in chamber ± 5 mm

Alignment with beams <20 m

What is the target design and what are the requirements?

(A) “Baseline” Direct Drive High

Gain Target Design

Divinyl benzene foam shellPolyvinyl phenol overcoatAu/Pd “reflector” on top

1. Baseline target (18K): <0.68 W/cm2 (970C and no gas)

2. Foam-insulated: <3.7 W/cm2 (970C and 12.5 mtorr @ 4000K)

3. Foam-insulated (16K): <9.3 W/cm2 (970C and 40 mtorr @ 4000K)

DT gas

DT solid

DT + foam

Insulating foam

Permeation barrier

~1 m fill holes

(B) “Backup” target with

additional “dry” foam to provide

insulation

Au and/or Pd on top

Foam-insulated target is thermally robust

Pressure cell

Micro-encapsulation and/or sputter coating (Be)

Synergism with ICF programs and decades of R&D

Fabricate Capsules

Fabricate Capsules

DT Fuel Fill

DT Fuel Fill

DT Fuel Layer

DT Fuel Layer

Fabricate hohlraum or sabot

Fabricate hohlraum or sabot

Load capsule

Load capsule

Fluidized bed (CH) Advanced manufacturing

methods

IFE target fab processes have many common elements - which are derived from ICF experiments

Injector demo experiment

Inject/Track or insert

Inject/Track or insert

Existing and major new ICF facilities

Z-ROMEGA EP

NIF

How is the target fabricated and what are the issues?

Pressure cellwith trays

Microencapsulation

600 Å Pd onPAMS shell

Cryogenic fluidizedbed layering

Advantage = started with ICF experience base

injector

Step Methods Demonstrated? Remaining IssuesCapsules, Microencapsulation, Yes, including DVB Non-concentricity, overcoat

polydensation quality, mass-production, meeting specs

Metal Overcoat Sputter Coating Yes, on small scale Standard industrial process..

Filling with DT Permeation Yes, including DVB shells Optimize for min. DT inventory

Layering -layering Yes, but on single targets Mass-production demo

Cryo HandlingCryostats Yes, but on single targets Part of layering/injection demoInjection EM, gas gun Room Temp. demo now, Accuracy, tracking demo,

cryo survival

So the specific issues in this session are………

Capsule non-concentricity - spec is NC <1% of wall thickness Overcoat - delamination of the overcoat, surface finish of 20 nm Gas tightness of overcoat & “buckle pressure” for filling Production process yield improvement Mass-production methods for 500,000/day - online characterization DT behavior under heat flux (really injection issue) - understand the limits of DT when exposed to heat flux (impact on chamber

design)

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Batch of ~400 3.5 mm OD DVB

Coating

Droplet generator

4 mm dia., 200 m foam layer, CH overcoat, Schroen, Streit

DT layer after ~1 W/cm2 for 24 ms

Failures during overpressure

The presentations deal directly with these issues………

Five talks/posters:

1) Divinyl benzene (DVB) shells - Diana Schroen, Jon Streit

2) Mass production of IFE targets - Brian Vermillion

3) Solid DT studies - Jim Hoffer, Drew Geller, John Sheliak

4) Poster: DVB foam shells with a dual initiator - Reny Paguio

5) Poster: Foam characterization with ultrasound - Leonard Bond, Morris Good, Diana Schroen

GDP Coated RF Foam (related ICF studies)

~ 5 µm PVP

DVB Foam

W2

Amp

DAQ

PCLaser

Data

Laser

PhotodiodeSensors

“Online” feedback & characterization