Recent Numerical Advances for Beam-Driven HEDP Experiments

S.A. Veitzer, P.H. Stoltz, J.R. CaryTech-X Corporation

J.J. BarnardLawrence Livermore National Laboratory

Fusion Energy Science Advisory Committee SubpanelWorkshop on High Energy Density Laboratory Plasmas

August 24 - 26, 2008Washington, D.C.

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Funded by DOE SBIR Grant #DE-FG02-03ER83797---------------------

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Ion Beams Can Drive Target Heating

• An attractive approach for studying HED, WDM, and ICF, with a potential for producing IFE

• Different attributes than laser-driven heating, yet some physics still relevant to ICF, etc.– Uniform heating of macroscopic target volumes– High repetition rate– Cost-effective

• Theory and simulation are important components for driving experiments

• Collaborative research with the HIF Virtual National Laboratory

• Recent successes in modeling energy deposition, especially with respect to low energy beams

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Threefold goals for enhanced numerical modeling

• Develop and implement accurate stopping power models at and below the Bragg peak

• Increase access to and ease-of-use of numerical models of beam-material interactions for the research community

• Validate stopping power models with established codes and experiments

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• Stopping power has three components– Bound electronic (Brandt-Kitigawa)– Free electron (Peter & Meyer-ter-Vehn)– Nuclear (Semi-empirical, SRIM)

• Compare with Classical Bethe-Bloch stopping

Low-energy beams require nuclear stopping power models

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ΛB =2mec

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• Models are implemented in C in a standalone numerical library called TxPhysics – open source and free to download for non-commercial use

• Automated build system works on Linux, Mac, and Windows

• Many language bindings for inclusion in simulation packages, e.g. Python, Java

• Routines are currently interfaced to– WARP (LBNL)– HYDRA (LLNL)– VORPAL, OOPIC Pro (Tech-X)– Others

• Additional physics, e.g. secondary electron emission, impact ionization, field emission, sputtering, and radiation models

• Python-driven web 2.0 interface

Modern software design standards provides increased usability

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Web and Python access to TxPhysicsphysics models

http://txphysics.txcorp.com

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Web interface allows quick access to stopping powers without coding

http://txphysics.txcorp.com

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Researchers can plot or download tables, save and publish

http://txphysics.txcorp.com

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Dual pulse simulations show dE/dx differences

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are needed to see this picture.

In collaboration with researchers at LLNL, we have interfaced TxPhysics stopping power models with Hydra.

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QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Dual pulse simulations show dE/dx differences

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QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Dual pulse simulations show dE/dx differences

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

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Future Direction: Grazing Incidence Focusing of beams

• Grazing collisions with solid density nozzles (hollow cones) can focus space charge dominated beams– Secondary electrons provide enhanced beam neutralization– Multiple reflections from cone surface may reduce the spot size

in the focal plane

• Experiments are needed to – Measure secondary electron yields for grazing incidence

collisions for various materials (conductors and insulators)– Demonstrate focusing by grazing incidence deflections

• Computational models are needed to– Drive target design and fabrication– Predicting accelerator performance