Ion dynamics in a supersonic jet: Experiments and simulations.

Area of Science:

• Plasma Physics
• Atomic and Molecular Physics
• Computational Physics

Background:

• Supersonic plasma jets are crucial in various applications, but ion dynamics within them are complex.
• Understanding ion behavior, including energy distribution and collisions, is key to controlling plasma properties.

Purpose of the Study:

• To develop and validate a computational model for simulating argon ion (Ar(+)) dynamics in a supersonic argon plasma jet.
• To compare model predictions with experimental measurements of ion energy distribution functions.
• To analyze energy loss mechanisms and charge transfer processes affecting Ar(+) ions.

Main Methods:

• Experimental measurement of Ar(+) energy distribution functions using a quadrupole mass spectrometer.
• Development of a numerical model integrating equations of motion for Ar(+) ions.
• Inclusion of Ar(+)-Ar induced dipole interactions via a Lennard-Jones potential and consideration of elastic and charge transfer collisions.
• Simulation of 1000 Ar(+) trajectories with a 10 ps time step.

Main Results:

• The model's simulated ion energy distribution functions showed excellent agreement with experimental data.
• Calculations provided insights into Ar(+) energy loss and mean free paths within the supersonic jet.
• The model successfully distinguished between collision processes with and without charge transfer.
• Effective cross sections for momentum and charge transfer collisions were evaluated and found to be in good agreement with literature values.

Conclusions:

• The developed model accurately simulates Ar(+) dynamics in supersonic plasma jets.
• Charge transfer phenomena significantly influence ion behavior and energy transfer within the jet.
• The study provides valuable data on collision cross sections relevant to ion energies between 0.5-10 eV.