Simulations of Fast Ion
Slowing-Down Rates in a
Background Plasma
Elijah Kolmes
Advised by Professor Cohen
2014 PEI Summer Internship at PPPL
Broader Context
• Working at Princeton Plasma Physics Lab
• Research geared toward understanding the behavior of
plasmas, which are important for developing fusion
energy.
Image from science.energy.gov
Field-Reversed Configurations
• Alternative approach to
magnetic confinement.
• Several potential
advantages, including
small size and potential
suitability for aneutronic
fuels.
• Behavior of energetic
fusion products has
important implications for
FRC performance.
• Power and particle control
Image from w3.pppl.gov
(taken by Professor Cohen)
Slowing-Down Rates in an FRC-like
Plasma
• Relevant for understanding the behavior of fusion
products, as well as understanding heating techniques.
• My simulations were primarily relevant to the behavior of
the products of D-He3 fusion.
• Strong magnetic field
• ρL < λD – possible disruptions to Debye shielding?
• Very high temperatures
• vfast ion > velectron
LSP and PIC Codes
• Large-scale plasma simulations.
• A few simplifications
• Particle-in-Cell codes: discretization of some
continuous quantities
• Larger numbers of “real” particles are
clumped together to be simulated as
macroparticles.
• Some of these effects turn out to be
more important than initially anticipated.
Overall Results
• Measured basic characteristics of the algorithm’s
performance (precision of energy conservation, etc.)
• Measured dependences of fast ion slowing-down rates on
a number of parameters, including fast ion charge and
plasma density.
• Most of these results were fairly close to the expected
relationships.
• Later, I found some interesting effects that came out of the
LSP code itself.
• Effects of macro-particle “clumping” on measurements of dW/dx.
Reflections
• This was a very rewarding experience.
• Exposure to computational physics and to plasma physics
research.
• Continued interest in plasma physics and in physics
research in general.
Thanks to:
• Professor Cohen, my advisor
• Dr. Welch at Voss Scientific
• Dr. Sefkow at Sandia National Labs