Simulations of Fast Ion Slowing-Down Rates in a Background PlasmaElijah 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