Fusion Magic?

“Any sufficiently advanced technology is indistinguishable from magic. Radical, transformative technologies typically appear ‘impossible’ when proposed, and obvious and inevitable once in place. To see things in a different way from those before is a rare, but necessary, quality in an innovator. Getting there from here takes courage and determination in addition to intellect, and is often driven by an underlying vision that transcends rationality.”

 A.C. Clarke, “ Profiles of the Future: An Inquiry into the Limits of the Possible” Holt, Rinehart and Winston, NY (1982).

Wayne MeierLawrence Livermore National Lab

Chamber Studies

Laser IFE Program WorkshopNaval Research Laboratory

February 6 & 7, 2001

* This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

Chamber studies area includes several tasks

• Target emissions (x-rays, debris, neutrons) for direct and indirect drive targets will be characterized

• Alternate chamber concepts will be developed and analyzed

– System integration/interface issues identified

– Analyses & experiments proposed to address critical issues

• Systems models will be improved and used to evaluate plants for KrF and DPSSLs

• Neutron damage modeling of chamber walls will be supported

Chamber studies will benefit both DP and IFE

• Threats to the chambers are similar but to varying degrees

• Damage mitigation techniques will be required by both DP and IFE chambers

• Analytical tools have commonality

– Target physics and characterization of target emissions

– Wall ablation calculations

– Chamber dynamics (condensation, impulse to structures)

– Neutron transport, activation, and damage modeling

• Systems integration considerations are important

– Design constraints (e.g., rep-rate limitations)

– Subsystem interface issues

• Systems modeling and optimization will help guide R&D

– Goals and metrics for various applications

Overall Objective………….. Integrated laser IFE chamber concepts

FY 01 Deliverables………... 1. Progress report on alternate chamber concept(s) including proposed next steps2. Status report on systems modeling for laser

IFE (models and resulting analyses)

PI Experience………………. Fusion Technology Group Leader (LLNL) (POC: W. Meier) Past project manager for Sombrero/Osiris power

plant studyProposed Amount………….. $ 700k

Relevance of Deliverables

[ ] NIF……………………

[X] Laser RR Facility…. Chambers for high rep-rate applications

[X] Other DP/NNSA…… First wall protection options

[X] Energy……………… Options for attractive chamber/plant designs

Related OFES activities…… Other chamber technology and systems studies including ARIES-IFE

LLNL Chamber Studies

Chamber first wall damage and survival is a key issue for both DP and IFE chambers

• Possible chamber wall threats

– Laser light

– X-rays

– Shrapnel (high velocity, solid and liquid projectiles)

– Debris (vaporized target material and fusion burn products)

– Gamma rays

– Neutrons

• Tasks include

– Characterizing target emissions for different types of targets

– Developing/improving first wall protection concepts

Example target spectra

109

1011

1013

1015

1017

10 100 1000 104

Burn Product Spectra from the NRL Target 1-D Analysis

Particles per unit energy (#/keV)

Particle energy (keV)

nHe4T

DH

He3

γ

L.J. Perkin et al., ARIES Meeting, PPPL, Sept. 19, 2000

Alternate chamber concepts - FY01 plan

• Review literature

• Identify potentially promising chamber concepts for direct drive

– Magnetically protected

– Wetted wall

– Alternate first wall materials/coatings

– ?

• Select concept(s) for additional study

• Complete preliminary analysis/assessment to identify key issues

• Propose next steps (analyses, simulations, experiments?) needed to resolve issues

• Complete progress report

One possible example – Magnetically protected first wall

I.O. Bohachevski et al., Nuclear Technology/Fusion, 1, 390 (1981)

Does MHD conversion make any sense?

B. G. Logan, Fusion Engineering and Design, 22, 151 (1993).

Systems integration is an important aspect of the proposed work

• It is important not to develop subsystems in isolation – encourage interactions of individuals working on target physics, chambers, target fabrication and injection

• Interface issues and constraints often require design trade-offs

• Laser/target/chamber interface issues will be considered for chamber design concepts we analyze

Final optics configuration depends on target type and chamber design

• 60 beams• Uniform (direct-drive) illumination• Dry-wall chamber• Fused silica final optics (wedges)• Focusing mirrors removed from

direct line of site

3D neutronics model of SOMBRERO target building including final optics and neutron dumps

Systems models and analyses will help identify the optimum design configurations

• Models include systems performance and cost as a function of design variables for laser, chamber, support and/or plant facilities

• Used to optimize various figures of merit

– Shot rate

– Laser efficiency

– Project cost

– Cost of electricity (IFE)

• Used to identify design aspects with high leverage for concept/ design improvements

Yield / rep-rate operating space – an example

0 2 4 6 8 10 12 14 160

200

400

600

800

1000

Low alpha, zooming, eta = 15%Alpha = 3, eta = 5%

Rep-rate, Hz

Target Yield, MJ

Limit on max yield, e.g.,set by first wall limits for given wall design and radius

Limit on max rep-rate,e.g., set by chamber clearingor target injection velocity

As chamber radius increases, the max yield typically increases, but max rep-rate might decrease (longer clearing time, limited target transit time). Constraints would shift up and left.

0 1 2 3 4 50

0.5

1

1.5

2

COE for alpha = 2Rep-rate for alpha = 2

Driver Energy, MJ

COE (c/kWeh) and Rep-rate (Hz)

Rep-rate constraints could prevent operatingat minimum COE point

E RR COE(MJ) (Hz) (norm.)

2.4 15 1.003.1 10 1.014.7 5 1.11

5 Hz pt.

E = 4.4 MJ

Min COE pt.

E = 2.4 MJ 10 Hz pt.

E = 3.1 MJ

Neutron damage modeling work will be supported

• $100k will be provided to leverage off the large DP effort on materials modeling for stockpile stewardship

• Need to include consideration of

– Fusion spectrum

– Fusion materials

Concentration of Traps300 nm

300 nm

300nm

Pulsed irradiation

- We simulate pulse rates of 1 Hz, 10 Hz and 100 Hz and an instantaneous dose rate of 1.4 dpa/s during the pulse (1s long). - Simulations were carried out at 300K (Stage III -> mobile vacancies) and 620K (Stage V->unstable vacancy clusters)

The effect of pulsed irradiation can be studied with kMC simulations

0

0.5

1

1.5

2

2.5

3

3.5

4

5 10-5 1 10-4 1.5 10-4 2 10-4

1 Hz10 Hz100 Hz1.4 10-6 dpa/s

Dose (dpa)

0

5 1016

1 1017

1.5 1017

2 1017

2.5 1017

5 10-5 1 10-4 1.5 10-4 2 10-4

Vacancy cluster density in iron irradiated at 300K

1 Hz10 Hz100 Hz1.4 e-6 dpa/s

Dose (dpa)

If we compare pulsed irradiation with continuous irradiation at 1.4 dpa/s with fusion neutrons (Magnetic Fusion conditions), the damage accumulation is almost identical to the 1 Hz case, whose integrated dose rate is also 1.4 dpa/s

The variable that controls vacancy cluster size is the annealing timebetween pulses, or between cascades in the continuous irradiation case.

Comparison between pulsed and continuum irradiation in Cu at 300 K

Chamber studies area includes several tasks

• Target emissions (x-rays, debris, neutrons) for direct and indirect drive targets will be characterized

• Alternate chamber concepts will be developed and analyzed

– System integration/interface issues identified

– Analyses & experiments proposed to address critical issues

• Systems models will be improved and used to evaluate plants for KrF and DPSSLs

• Neutron damage modeling of chamber walls will be supported

We are looking forward to contributing in many areas and working with this team to advance the technical

feasibility and attractiveness of laser IFE designs.