# Positions Particles¶

This plugin prints out the position, momentum, mass, macro particle weighting, electric charge and relativistic gamma factor of a particle to stdout (usually inside the simOutput/output file). It only works with test simulations that have only one particle.

## .cfg file¶

By setting the command line flag --<species>_position.period to a non-zero number, the analyzer is used. In order to get the particle trajectory for each time step the period needs to be set to 1, meaning e.g. --e_position.period 1 for electrons. If less output is needed, e.g. only every 10th time step, the period can be set to different values, e.g. --e_position.period 10.

negligible.

negligible.

## Output¶

The electron trajectory is written directly to the standard output. Therefore, it goes both to simOutput/output as well as to the output file specified by the machine used (usually the stdout file in the main directory of the simulation). The output is ASCII-text only. It has the following format:

[ANALYSIS] [MPI_Rank] [COUNTER] [<species>_position] [currentTimeStep] currentTime {position.x position.y position.z} {momentum.x momentum.y momentum.z} mass weighting charge gamma


Value

Description

Unit

MPI_Rank

MPI rank at which prints the particle position

none

COUNTER

name of the plugin | always <species>_position

currentTimeStep

simulation time step = number of PIC cycles

none

currentTime

simulation time in SI units

seconds

position.x _position.y _position.z

location of the particle in space

meters

momentum.x _momentum.y _momentum.z

momentum of particle

kg m/s

mass

mass of macro particle

kg

weighting

number of electrons represented by the macro particle

none

charge

charge of macro particle

Coulomb

gamma

relativistic gamma factor of particle

none

# an example output line:
[ANALYSIS] [2] [COUNTER] [e_position] [878] 1.46440742e-14 {1.032e-05 4.570851689815522e-05 5.2e-06} {0 -1.
337873603181226e-21 0} 9.109382e-31 1 -1.602176e-19 4.999998569488525


In order to extract only the trajectory information from the total output stored in stdout, the following command on a bash command line could be used:

grep "e_position" stdout > trajectory.dat


The particle data is then stored in trajectory.dat.

In order to extract e.g. the position from this line the following can be used:

cat trajectory.dat | awk '{print \$7}' | sed -e "s/{//g" | sed -e 's/}//g' | sed -e 's/,/\t/g' > position.dat


## Known Issues¶

Attention

This plugin only works correctly if a single particle is simulated. If more than one particle is simulated, the output becomes random, because only the information of one particle is printed. This plugin might be upgraded to work with multiple particles, but better use our HDF5 or ADIOS plugin instead and assign particleIds to individual particles.

Attention

Currently, both simOutput/output and stdout are overwritten at restart. All data from the plugin is lost, if these file are not backuped manually.