On the radiative heat loss and axis-switching phenomena of a decaying laser spark

Abstract

A three-dimensional numerical simulation of a decaying laser spark in gaseous nitrogen has been carried out in Cartesian co-ordinate. The simulation starts with the introduction of a laser pulse in the domain. Thermal equilibrium has been assumed throughout the numerical simulation involving the species N2, N, N+, e−. The boundary conditions are treated following characteristic property of the waves to ensure smooth transmission of the blast wave out of the computational domain. The previously unexplained axis-switching phenomenon of the breakdown region has been explained, and a qualitative comparison of the same with experimental schlieren images has been made. The total radiation loss, including the loss during the breakdown, has been calculated. The variation of inverse Bremsstrahlung radiation, black body radiation, and spectral radiation of atomic nitrogen with time have been shown separately. Additionally, the temporal variation of radiation intensity of atomic nitrogen over a wavelength range has been plotted. The total radiation loss has been found to be small compared to the deposited laser energy.

Insight into the evolution of laser-induced plasma during successive deposition of laser energy

“…Later, the plasma begins to retreat due to its low available energy and also due to the lower pressure in the core. The fluctutation of core pressure can also be seen in Fig 16 also in our previous works [29,31]. Zone III starts when the plasma begins to cool and recombination begins to dominate the ionization process n e n i /n a ≥ 1.…”

“…W and K b are the potential energy and Boltzmann constant, and T is the temperature of plasma in thermal equilibrium. C is the constant that depends on the atomic crosssection, plank constant and other constant factors [28,29,30]. Let us now understand what is really happening physically and how Eq.…”

Mechanism of nonequilibrium plasma-enhanced ignition in the event of dual-pulse laser energy deposition

“…The model could simulate the key events such as the formation of the two-lobed kernel structure and quasi-periodic spots for multi-mode pulses as observed in experiments [63]. Conversely, assuming an experimentally observed laser beam shape, Joardar et al [64] also developed a three-dimensional numerical model incorporating three radiation losses (e.g. bremsstrahlung, blackbody, and spectrally integrated radiation of atomic nitrogen under local thermodynamic equilibrium approximation), and they concluded that the total radiation losses were insignificant compared with the deposited laser energy.…”