Binary collisions and impact ionization

Smilei includes binary collisions between various species, which can also generate ionization when one of the species is ions and the other one electrons. Smilei’s website already gives a description of the approach, and provides results from various benchmarks.

The list of benchmarks, located in the benchmarks/collisions/ folder is briefly described below. You may run any of these benchmarks depending on your interests.

Beam relaxation

An electron beam encounters a thermal ion population; e-i collisions slow the beam down and make it spread. Various electron velocities and ion charges are considered. For each case, the ratios of weights between electrons and ions is varied.

1. initial velocity = 0.05, ion charge = 1

beam_relaxation1.py

beam_relaxation2.py

beam_relaxation3.py

Analysis and plotting provided in beam_relaxation123.py

2. initial velocity = 0.01, ion charge = 1

beam_relaxation4.py

beam_relaxation5.py

beam_relaxation6.py

Analysis and plotting provided in beam_relaxation456.py

3. initial velocity = 0.01, ion charge = 3

beam_relaxation7.py

beam_relaxation8.py

beam_relaxation9.py

Analysis and plotting provided in beam_relaxation789.py

Thermalization

Thermal electrons start with a different temperature from that of ions. The thermalization due to e-i collisions is monitored for three different weight ratios.

thermalisation_ei1.py

thermalisation_ei2.py

thermalisation_ei3.py

Analysis and plotting provided in thermalisation_ei123.py

Temperature isotropization

Non-isotropic thermal electrons are isotropized with e-e collisions.

temperature_isotropization1.py

temperature_isotropization2.py

Analysis and plotting provided in temperature_isotropization.py

Maxwellianization

An electron population starting with a rectangular velocity distribution becomes maxwellian due to e-e collisions.

Maxwellianization1.py

Analysis and plotting provided in Maxwellianization.py

Stopping power

The e-e slowing rate of test electrons passing through an electron plasma is monitored vs. time and compared to a theoretical stopping power.

Stopping_power1.py : projectiles from 10 to 30 keV

Stopping_power2.py : projectiles from 100 to 300 keV

Stopping_power3.py : projectiles from 1 to 10 MeV

Analysis and plotting provided in Stopping_power123.py

Ionization rate

Drifting electrons in a cold Al plasma cause e-i impact ionization at a rate compared to theoretical values. The three inputs below correspond to various weight ratios between electrons and ions.

ionization_rate1.py

ionization_rate2.py

ionization_rate3.py

Analysis and plotting provided in ionization_rate.py

Inelastic stopping power

The ionizing e-i slowing rate of test electrons passing through an Al plasma is monitored vs. time and compared to a theoretical stopping power.

ionization_stopping_power1.py : measurement for electrons at various energies

ionization_stopping_power2.py :

ionization_stopping_power3.py : three examples to show the stopping dynamics

ionization_stopping_power4.py :

Analysis and plotting provided in ionization_stopping_power.py

Multiple ionization

The capability to ionize several times in one timestep is illustrated for five different materials. For each material, two cases are provided: the first is well resolved, while the second has a low time resolution requiring multiple ionization.

ionization_multipleC1.py

ionization_multipleC2.py

ionization_multipleAl1.py

ionization_multipleAl2.py

ionization_multipleZn1.py

ionization_multipleZn2.py

ionization_multipleSn1.py

ionization_multipleSn2.py

ionization_multipleAu1.py

ionization_multipleAu2.py

Analysis and plotting provided in ionization_multiple.py

Effect of neglecting recombination

As recombination is not accounted for, we can expect excess ionization to occur indefinitely without being balanced to equilibrium. For picosecond laser interaction, we illustrate here that the recombination rate can be neglected, thus providing reasonable ionization state vs. temperature, in various materials.

ionization_equilibriumH.py

ionization_equilibriumAl.py

ionization_equilibriumZn.py

ionization_equilibriumAu.py

Analysis and plotting provided in ionization_equilibrium.py