Status and Plans for Systems Modeling for Laser IFE

HAPL Progress Meeting13-14 November 2001

Pleasanton, CA

Wayne Meier, Charles Orth, Don Blackfield Lawrence Livermore National Laboratory*

* Work performed under the auspices of the U. S. Department of Energy by University of California Lawrence Livermore National Laboratory under Contract W-7405-Eng-48

UCRL-PRES-146198

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Systems modeling work has included the following activities

• Evaluation of the potential economic benefits of Fast Ignition applicable to both DPSSL and KrF (See Fast Ignitor Poster)

• Charles Orth’s use of his DPSSL IFE code to develop a simple driver cost scaling relationship for a DPSSL

• Use of Sombrero systems code with a DPSSL driver to evaluate sensitivity of COE to direct-drive target performance

• Improvements to Orth’s DPSSL IFE code

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DPSSL cost scaling derived from Orth’s code

The total laser cost is approximately given by

CL = 570 + 370·(Cdiode/0.07)·E + 21·E2 $M

where

E = 3 laser energy (MJ) and

Cdiode = diode cost per peak watt ($/Wp)

- Established over driver energy range of ~ 1- 6 MJ

- Fixed part likely dependent on assumed requirement for large number of beams (Orth set N 192) – needs further analysis

- The term proportional to E is the diode cost

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Direct-drive target gain curves depend strongly on the Fermi degenerate parameter,

0.1 1 1010

100

1 103

Alpha = 1 plus zoomingAlpha = 2Alpha = 3

Driver energy, MJ

Targ

et g

ain

Representative curves – will be improved with additional work on direct-drive target designs

= 1 with zooming

= 2= 3

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Optimal driver energy and COE decrease with increasing target performance

COE, ¢/kWeh

Rep-rate, Hz

- Optimal driver energy decreases from 3.5 MJ for = 3 to 1.5 MJ for = 1

- Optimal rep-rate is 12-15 Hz

- Minimum COE is significantly lower for low

COEmin1 = 7.8 ¢/kWeh

COEmin2 = 9.4 ¢/kWeh (+20%)

COEmin3 = 10.9 ¢/kWeh (+40%)0 1 2 3 4 5

0

5

10

15

COE for alpha = 3COE for alpha = 2COE for alpha = 1 plus zoomingRep-rate for alpha = 3Rep-rate for alpha = 1Rep-rate for alpha = 1

Driver Energy, MJ

Net power = 1 GWe, laser efficiency = 8.6% (fixed)

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Achieving high driver efficiency is most important for the lowest gain curve

COE, ¢/kWeh

Net power = 1 GWe, Rep-rate = 10 Hz

Effect of doubling laser efficiency from 5 to 10%: = 3: COE decreases 24 % = 2: COE decreases 17 % = 1: COE decreases 9 %

Future work – Determine the dependence of laser efficiency on laser energy and determine laser cost/efficiency trade-offs.

4 6 8 10 12 140

2

4

6

8

10

12

14

Driver efficiency, %

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Improvements to Orth’s DPSSL IFE code

• Motivation• Objectives• Future Activities• Revised Code Structure

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Motivation: An improved, updated systems model will be valuable tool for the laser IFE community (1)

• Overall objective is to provide useful information to the laser IFE community, including– Information to help make R&D decisions, e.g.,

• What is the value of developing optical switches and pinholes for average power operation?

• What can we afford to pay for more efficient components (diode arrays, pulsed power for KrF)?

• What is the point of diminishing returns for hibachi lifetime?– Input to the development plan by identifying optimal design

points• How big (MJ’s) is a power plant driver and how does that

influence development plan/steps?• How do design trades impact next step IRE design? e.g.,

minimize cost at expense of efficiency?

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Motivation: An improved, updated systems model will be valuable tool for the laser IFE community (2)

– Consistent comparisons of laser IFE design options (different drivers/chambers/target combinations)

• How does a more efficient but more expensive laser compare to a less efficient, lower cost option? How do the results depend on success in target performance?

• What is the trade between higher plant efficiency (obtained by chamber/BOP designs that operate at higher temperature) and higher associated costs?

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A systems model will aid IRE decisions by narrowing design space for detailed designs

• Current Development Strategy: IFE target design + Ignition on NIF + IRE + chamber and target technology development combine to make a compelling case for an ETF

• The IRE will be cost constrained yet must demonstrate laser technology at a scale that extrapolates to an ETF driver (~ 1-2 MJ’s). It must also meet technical goals (efficiency, reliability, etc.).

• A flexible systems model can rapidly examine a wide parameter space of IRE design options to define a limited number of attractive points that would receive more detailed design effort (i.e., the type of detailed design required for Mercury, which is currently very time-consuming)

• The system code will be used to address questions related to cost, performance and technology development

• Results provide a technical basis for defending selection of final proposed IRE point design

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A system model will aid IRE decisions –an example of one type of result

Maximumallowable cost

Here the potential design space is above some minimum laser energy (set by need to demonstrate scalability to ETF driver or other technical objectives of the IRE) and below some maximum allowable cost based on projected IFE program budgets.

Component cost - sensitivity to diode cost would allow one to select an IRE energy base on success in lowering diode costs

Laser energy

IRECost

Increasing diode cost

Minimum laser size Maximumallowable cost

Laser energy

Increasing crystal scale

Minimum laser size

Technology development – sensitivity to success in developing large laser crystals defines another aspect of the design space

Efficiency and reliability – similar plots could be constructed to define design space andcost trades with respect to laser (or component) efficiency and reliability

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Objectives: Features required by a successful systems code

• Should be able to quickly explore a highly dimensioned design space

• Must contain up-to-date algorithms to remain relevant• Should be flexible so that design options can quickly be

examined• Must be easy to modify by “non-experts” so that algorithms

can be kept up-to-date• Should be extremely robust and prevent examination of “non-

physical” design space• Should be easy to operate (user-friendly)• Output results should be understandable and design options

clearly presented

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Future Activities: Improve driver, target, and Chamber/BOP models

• Update and improve DPSSL model (dates to 1994)– e.g., beam smoothing, extraction model, diff. architectures

• Need improved KrF Laser model from NRL (current model dates to Avco work in early 1990’s)– e.g., Scaling tied to physics, current thinking on component

cost and performance, etc.• Update target gain curves to reflect target physics results and

include dependence on other laser parameters (e.g., number of beams)

• Update Sombrero chamber model to reflect ARIES and HAPL results on chamber radius vs. protective gas density and target yield

• Review BOP and economics models and benchmark conventional subsystems (e.g., electric plant equipment) to MFE systems code