FBPIC-Electric Work Profiler (FBPIC-EWP)

FBPIC-EWP, short for FBPIC-Electric Work Profiler, is a tool designed to estimate the work performed by the Laser and Plasma fields on tracked electrons in FBPIC (Fourier-Bessel Particle-In-Cell) simulations.

Overview and Motivation

FBPIC-EWP operates within the context of FBPIC simulations, which employs a set of 2D cylindrical grids to represent fields with distinct azimuthal modes. While m=0 corresponds to fields independent of the azimuthal angle $\theta$, m>1 represents fields varying proportionally to $\cos(\theta)$ and $\sin(\theta)$. In an idealized scenario, m=1 represents the laser field.

The motivation behind FBPIC-EWP stems from the need to understand the contribution of both the Laser and Plasma fields to regimes like Direct Laser Acceleration. By estimating the work performed by these fields, researchers can gain insights into the acceleration mechanisms of tracked electrons.

Key Features

FBPIC-EWP workflow is the following:

• Field Retrieval Process: FBPIC-EWP retrieves the total field ($\mathbf{E}_T$) on all selected particles, along with their coordinates $(x, y, z)$ and normalized momenta ($u$) for every FBPIC iteration. The total electric field is defined as the sum of the Laser and Plasma fields (i.e., $\mathbf{E}_L$ and $\mathbf{E}_W$ respectively)
• Laser and Plasma field Calculation: Disposing of the 3D electric field map, a 2D linear interpolation is performed for m=0 in order to calculate the Plasma electric field on each electron. Subsequently, the Laser electric field is retrieved as $\mathbf{E}_L = \mathbf{E}_T - \mathbf{E}_W$
• Work Calculation: Lastly, the work of each electric field component is calculated as $W_{W,L} = -e \int_{0}^{t} \mathbf{E}_{W,L} \cdot \mathbf{v},dt'$ in the time interval $[0, t]$. The results are stored in an HDF5 file.

FBPIC-EWP also allows to calculate the Laser and Plasma magnetic fields on each particle, through the magnetic_field parameter in the main.py module. magnetic_field is set to False by default.

Requirements

• Python 3.x
• NumPy
• SciPy
• numba
• h5py
• openPMD-viewer
• tqdm

Files

• func.py: Python module containing all the functions necessary to perform the work calculation (interp_2D, particles_loop, spatial_lowpass_filter and shift_half_step)
• main.py: Python module that allows to select the simulation and the electrons to study. It performs the actual work calcuation using the func.py module

Installation

You can install FBPIC-EWP cloning the source

git clone https://github.com/laumrt/FBPIC-EWP.git
cd FBPIC-EWP
pip install .

or directly with PiPy

pip install git+https://github.com/laumrt/FBPIC-EWP.git

Contributions

Your contributions and suggestions for improvements are welcome. If you encounter any issues or have ideas for enhancements, please feel free to open an issue or submit a pull request.