Coding

As a computational physicist, I don't just use simulation codes; I also develop them. Here are some of the tools I've used and/or developed. Outside of the heavy simulation codes, I mostly use Python for analysis but I like to dabble and play with other languages such as Julia.

GTC simulation results from our initial paper on drift-wave stability in the FRC.

Gyrokinetic Toroidal Code (GTC)

GTC is the simulation code that my advisor at UCI started some twenty years ago. Since then, it has been modified and added to by researchers from around the world. At its base, GTC is a particle-in-cell code which solves the gyrokinetic equations written in Fortran.

Most of the modifications that I added to the code involved components related to the field-reversed configuration (FRC). For example, I added the semi-spectral Poisson solver and wedge domain, which made use of the FRC's geometry to reduce computational costs and raise signal-to-noise efficiency.

A New Code (ANC)

ANC is the simulation code that was started by a (at the time) more senior student in the plasma theory/computation group at UCI during his PhD (along with help from one of the staff scientists in our group). Since then, I have helped added to and modified the code as well, working in the same group currently as well. At its base, ANC is also a particle-in-cell code which solves the gyrokinetic equations written in Fortran, with the main difference in physics being that the equations are cast in cylindrical coordinates (whereas GTC's equations are cast in magnetic Boozer coordinates) which allow for simulation across the magnetic separatrix without singularities. ANC is also written using more modern Fortran standards, including more object-oriented methods.

Part of the modifications that I contributed to ANC were essentially ports of the Poisson solver from GTC to ANC , benchmark tests, and so on. A major change that I added was the implementation of a field-aligned mesh for the code which added to computational efficiency and numerical stability for turbulence studies.

ANC field-aligned simulation mesh follows along the magnetic field-lines for numerical stability and efficiency.

A simulation marker particle bouncing between the high magnetic fields outside of the core (with the direction of time represented by color going from red to purple to blue). This shows the capable of the blended particle mover in capturing the full kinetics of the particle with small enough time-steps.

A quick simulation of a wakefield with lattice effects, showing the (TOP) electric field, (MID) electron density and contours of the laser pulse, and (BOT) a line out of the longitudinal electric field and laser pulse. This was a quick proof of concept and uses an initial waveform inside of the simulation domain instead of a laser pulse being injected from outside of the domain, which explains the patterns left in the initial pulse region on the left side.

EPOCH

EPOCH is a simulation code developed in Europe developed for plasma wakefield physics. This is a code that I and others used for plasma acceleration studies (such as the work on relativistic ponderomotive acceleration and the betatron radiation). In addition, I have made changes our own forked versions of EPOCH to include finite particle shape effects, simple lattice effects, and so forth.

PWFA

PWFA is a 1-D relativistic, electromagnetic, particle-in-cell code. It was based on a simulation code from the Department of Earth and Planetary Science at University of Tokyo, referred to me by Prof. Toshiki Tajima. In order to efficiently use this code for large scale parameter scans, I added OpenMP parallelism to this code and a variety of other conveniences (including run-time variables instead of compiler-time variables). In addition, I created a set of primitive Python scripts for post-processing.

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