Diagnostics, Snapshots, & Data Output

Data Saving

Simulation data is saved in two ways:

1. Diagnostics: tables of individual parameters vs. time
2. Snapshots: full-simulation reports at specified times

Diagnostics

Diagnostics come in two classes:

1. Those collected at locations corresponding to probes specified in the file ssc_diagnostics.dat
2. Those related to global system parameters

and are saved in files where the first row is time in nano-seconds and the second column is the indicated parameter. If probes are requested, a list of the actual probe locations is given in the file _probelocs.dat.

A complete list of each diagnostic parameter and the file it is outputted in (as well as the column contents in the second and ensuing columns, if necessary), is:

1. Probe parameters
   • Electron/ion density: dim_Ne_vst.dat/dim_Ni_vst.dat
   • Plasma potential: dim_F_vst.dat
   • Electric field: dim_Ex_vst.dat
2. Global parameters
   • Energies
     • Total energy (potential + kinetic) in particles: dim_fullenergy_vst.dat
     • Potential energy of particles: dim_potenergy_vst.dat (both / elec / ion)
     • Kinetic energy of particles: dim_kinenergy_vst.dat (both / elec / ion)
     • Average kinetic energy of an electron/ion: dim_energy_1e_vst.dat/dim_energy_1i_vst.dat (total / x-directed / y-directed / z-directed)
     • Total kinetic energy of particles that struck the walls since the last diagnostic output: dim_energy_wall_vst.dat (both / elec / ions)
     • Total kinetic energy of particles that were emitted or reflected from the walls since the last diagnostic output: dim_energy_emit_vst.dat (both species / elec / ion)
     • Total kinetic energy of particles lost due to collisions with neutrals since the last diagnostic output: dim_energy_coll_vst.dat (both / elec / ion)
     • Energy into plasma particles due to Joule heating: dim_energy_heat_vst.dat (both / elec / ion)
     • Violation of energy conservation: dim_energy_cons_violat_vst.dat ((Total Energy) - (Wall Losses + Wall Emission + Collisional Losses + Joule Heating) - (Total Energy at prior timestep)) / (Total Energy)
   • Energy Rates (aka. Power)
     • Average rate of change in total energy of particles over diagnostic collection: dim_rate_fullenergy_vst.dat
     • Average rate of change in potential energy of particles over diagnostic collection: dim_rate_potenergy_vst.dat (both / elec / ion)
     • Average rate of change in kinetic energy of particles over diagnostic collection: dim_rate_kinenergy_vst.dat (both / elec / ion)
     • Average rate of change of total kinetic energy of particles that struck the walls over the last diagnostic collection: dim_rate_energy_wall_vst.dat (both / elec / ion)
     • Average rate of change of total kinetic energy of particles that were emitted or reflected from the walls over the last diagnostic collection: dim_rate_energy_emit_vst.dat (both / elec / ion)
     • Average rate of change of total kinetic energy of particles lost due to collisions with neutrals over the last diagnostic collection: dim_rate_energy_coll_vst.dat (both / elec / ion)
     • Average rate of change of energy into plasma particles due to Joule heating over the last diagnostic collection: dim_rate_energy_heat_vst.dat (both species / elec / ion)
   • Perpendicular flow (average over all particles aka. the full volume)
     • Average electron flow velocity in the y/z direction for the preceding timestep: dim_vy_e_vst.dat/dim_vz_e_vst.dat
     • Average current density in the y/z direction for the preceding timestep: dim_jy_vst.dat/dim_jy_vst.dat
   • Collision Frequency (average over the full volume)
     • Electron-neutral collision frequency over the last diagnostic collection: dim_fen_collisions_vst.dat (el / exct-1 / exct-2 / ioniz / turbulence)
     • Ion-neutral collision frequency over the last diagnostic collection: dim_fin_collisions_vst.dat (el / ch-x / turbulence)
   • Wall Interactions
     • Number of particles that interact with the left wall over diagnostic collection: dim_n_leftwall_vst.dat (rate elec impact / rate ion impact / rate elec emit / rate ion emit / rate elec emit via iSEE / surface charge / E field at wall / potential at the wall / current in ext circuit from current continuity at left wall / current in external circuit from Ohm's law)
     • Number of particles that interact with the right wall over diagnostic collection: dim_n_rightwall_vst.dat (rate elec impact / rate ion impact / rate elec emit / rate ion emit / rate elec emit via iSEE / surface charge / E field at wall / potential at the wall / current in ext circuit from current continuity at right wall / current in external circuit from Ohm's law)
     • Average energy of particles that impact the left wall over diagnostic collection: dim_avgenergy_leftwall_vst.dat (elec / ion)
     • Average energy of particles that impact the right wall over diagnostic collection: dim_avgenergy_rightwall_vst.dat (elec / ion)
     • Average energy of particles that are emitted from the left wall over diagnostic collection: dim_avgenergy_leftemit_vst.dat (elec from non-iSEE / ion / elec from iSEE)
     • Average energy of particles that are emitted from the right wall over diagnostic collection: dim_avgenergy_rightemit_vst.dat (elec from non-iSEE / ion / elec from iSEE)
     • Emission coefficient from the left wall: dim_gamma_left_vst.dat (elec / ion / elec elast reflection / elec inelastic reflection / elec SEE)
     • Emission coefficient from the right wall: dim_gamma_right_vst.dat (elec / ion / elec elast reflection / elec inelastic reflection / elec induced SEE)
     • Number of and source of electrons that hit the left wall: dim_n_leftwall_comp_vst.dat (from right wall, after collision, untracked)
     • Number of and source of electrons that hit the right wall: dim_n_rightwall_comp_vst.dat (from left wall, after collision, untracked)
     • Average energy of and source of electrons that hit the left wall: dim_avgenergy_leftwall_comp_vst.dat (from the right, after collision, untracked)
     • Average energy of and source of electrons that hit the right wall: dim_avgenergy_rightwall_comp_vst.dat (from the left, after collision, untracked)
     • Emission coefficient and source of electrons that hit the left wall: dim_gamma_left_comp_vst.dat (from the right, after collision, untracked)
     • Emission coefficient and source of electrons that hit the right wall: dim_gamma_right_comp_vst.dat (from the left, after collision, untracked)

Important Note: A strikethrough in the above list indicates that something about this diagnostic may not be properly implemented.

Snapshots

Snapshots save data in two ways:

1. Spatial data written into a _####_all_vsx.dat file. Spatial data is saved at each plasma node, or cell boundary
2. Distribution functions over velocity or energy

All snapshot data is saved in files with a naming convention _####_<data_type>.dat where #### is the snapshot number (ranging from 1 to 9999) and <data_type> is the file name. The actual snapshot times are printed to the file _snapmoments.dat.

A complete list of all parameters saved in snapshots and the file it is outputted in (as well as the column contents in the first and ensuing columns, if necessary), is:

1. In the _####_all_vsx.dat file:
   • col 1: X-coordinate of the plasma node [m]
   • col 2: Instantaneous electrostatic potential [V]
   • col 3: Instantaneous X-electric field [V]
   • col 4: Instantaneous electron number density [m^-3]
   • col 5: Instantaneous ion number density [m^-3]
   • col 6: X-electric current density averaged over the diagnostic step [A/m^2]
   • col 7: Y-electric current density averaged over diagnostic collection [A/m^2]
   • col 8: Z-electric current density averaged over diagnostic collection [A/m^2]
   • col 9: X-velocity of electrons averaged over diagnostic collection [m/s]
   • col 10: Y-velocity of electrons averaged over diagnostic collection [m/s]
   • col 11: Z-velocity of electrons averaged over diagnostic collection [m/s]
   • col 12: X-energy of electrons averaged over diagnostic collection [eV]
   • col 13: Y-energy of electrons averaged over diagnostic collection [eV]
   • col 14: Z-energy of electrons averaged over diagnostic collection [eV]
   • col 15: X-velocity of ions averaged over diagnostic collection [m/s]
   • col 16: Y-velocity of ions averaged over diagnostic collection [m/s]
   • col 17: Z-velocity of ions averaged over diagnostic collection [m/s]
   • col 18: X-energy of ions averaged over diagnostic collection [eV]
   • col 19: Y-energy of ions averaged over diagnostic collection [eV]
   • col 20: Z-energy of ions averaged over diagnostic collection [eV]
   • col 21: Instantaneous BX-magnetic field [Gauss]
   • col 22: Instantaneous BY-magnetic field [Gauss]
   • col 23: Volume ionization rate averaged over the diagnostic step
   • col 24: Integral of volume ionization rate averaged over the diagnostic step
   • col 25: Ion flux averaged over the diagnostic step
   • col 26: Electron flux averaged over the diagnostic step
   • col 27: Gas heating rate due to elastic collisions w. electrons averaged over the diagnostic step [W/cm3]
   • col 28: Gas heating rate due to collisions w. ions averaged over the diagnostic step [W/cm3]
   • col 29: Charge density at the left wall (x = 0) [Normalized Units]
   • col 30: Displacement current [A/m^2]
2. Distribution Functions
   • Energy distribution functions [eV]
     • Instantaneous electron distribution in energy: _####_eedf.dat (midpoint of energy bin, number of elec)
     • Instantaneous ion distribution in energy: _####_iedf.dat (midpoint of energy bin, number of ion)
     • Distribution of ions impacting the left wall since the prior snapshot (or simulation start time): _####_ilwedf.dat (midpoint of energy bin, number of ion)
     • Distribution of ions impacting the right wall since the prior snapshot (or simulation start time): _####_irwedf.dat (midpoint of energy bin, number of ion)
   • Velocity distribution functions [V_th_e]
     • Instantaneous electron distribution in X-velocity: _####_evxdf.dat (midpoint of velocity bin, number of elec, number of elec from the left wall, number of elec from the right wall)
     • Instantaneous ion distribution in X-velocity: _####_ivxdf.dat (midpoint of velocity bin, number of ion)
     • Instantaneous electron distribution in Y-velocity: _####_eyxdf.dat (midpoint of velocity bin, number of elec, number of elec from the left wall, number of elec from the right wall)
     • Instantaneous electron distribution in Z-velocity: _####_evzdf.dat (midpoint of velocity bin, number of elec, number of elec from the left wall, number of elec from the right wall)