Laser ablated carbon plume flow dynamics under magnetic field

Abstract

The dynamics of a conducting laser ablated carbon plume flow in the ablation furnace typical for nanoparticle synthesis is investigated by numerical modeling. The effect of magnetic field on the flow is accounted through the Lorentz body force. The study begins with benchmark calculations of two simple test cases, the Kelvin–Helmholtz instability and Hartmann layer. The evolution of plume is then studied for longitudinal and transverse magnetic fields. It is observed that the transverse magnetic fields have more impact than longitudinal fields on plume evolution for this application. Ionization and heat capacity variation in the plume are accounted through the Saha equation and the Shomate equation, respectively. Multiple plume ejections typical for pulsed laser deposition of thin films are also discussed.

Numerical simulations of laser ablated plumes using Particle-in-Cell (PIC) methods

“…As observed (Hoffman et al, 2011). already (Pathak & Chandy, 2009;Neogi & Thareja, 2001) the presence of the J × B magnetic force changes the behavior of the plasma plume with respect to the one expanding for example into vacuum having a strong influence on the ionization characteristics as well as on the velocity of the plume itself. This translates for axial magnetic field as for HEIGHTS-PIC in a stronger confinement close to target.…”

“…Carbon has been studied for many years as possible candidate of divertors and plasma facing components in Tokamaks and understanding its plasma plume evolution and shielding effects is still very important. Other studies using laser pulses interacting with an external magnetic field have pointed out it the importance of the J × B force in effectively containing the plume propagation converting kinetic energy into thermal energy (Pathak & Chandy, 2009). All these aspects of the plasma plume are studied and analyzed using HEIGHTS-PIC package and showed good agreement with both theoretical and experimental available results.…”

The Investigation of Plasma Produced by Intense Nanosecond Laser Ablation in Vacuum Under External Magnetic Field Using a Two-Stage Model

“…At the end of Stage I, the conditions of laser-induced plasma can be predicted by the model in Stage I, which will be used to determine the plasma initial conditions (in the way discussed earlier) for the model calculation in Stage II, where the plasma long-term evolution in vacuum under the applied external magnetic field is described by solving 2D gas dynamic equations in the plasma plume region [11,12,14,25] dL IdM dN _d t "'"r dr "^"öT"^( la)…”

“…(where p^ is the electrical resistivity), V is the velocity vector, and / is the electric current density induced by electromagnetic field and can be calculated as [11] …”

“…For example, in Ref. [11], a model has been developed for laser ablated carbon plume flow under magnetic field. However, the model does not simulate the initial plasma generation process.…”