Experimental investigation of ultraviolet laser induced plasma density and temperature evolution in air

Abstract

We present measurements and analysis of laser induced plasma neutral densities and temperatures in dry air by focusing 200 mJ, 10 MW high power, 193 nm ultraviolet ArF ͑argon fluoride͒ laser radiation to a 30 m radius spot size. We examine these properties that result from multiphoton and collisional cascade processes for pressures ranging from 40 Torr to 5 atm. A laser shadowgraphy diagnostic technique is used to obtain the plasma electron temperature just after the shock front and this is compared with optical emission spectroscopic measurements of nitrogen rotational and vibrational temperatures. Two-color laser interferometry is employed to measure time resolved spatial electron and neutral density decay in initial local thermodynamic equilibrium ͑LTE͒ and non-LTE conditions. The radiating species and thermodynamic characteristics of the plasma are analyzed by means of optical emission spectroscopy ͑OES͒ supported by SPECAIR, a special OES program for air constituent plasmas. Core plasma rotational and vibrational temperatures are obtained from the emission spectra from the N 2 C-B͑2+͒ transitions by matching the experimental spectrum results with the SPECAIR simulation results and the results are compared with the electron temperature just behind the shock wave. The plasma density decay measurements are compared with a simplified electron density decay model that illustrates the dominant three-and two-body recombination terms with good correlation.

Dynamics of strong-field laser-induced microplasma formation in noble gases

“…An order of magnitude decrease in the electron temperature of Xe plasma is observed within the first 250 ps after the plasma formation. Tracking such rapid dynamics was made possible in our measurements because the temporal resolution is increased by several orders of magnitude compared to the previous nanosecond measurements [29,30,33,34]. The e> [35] , and provide a complement to the h lower values of p I is manifest in the intensity evolution of the FWM signal generated in the micro-plasma.…”

“…However, these spectroscopic techniques have only been demonstrated for relatively long time scales of >10 ns. The electron temperature can also be determined by measuring the expansion velocity of the shock wave generated by the plasma [33,34]. Measurements of plasmas produced by ns pulses have been made in air using a cw probe in which the temporal resolution was limited by the gating of the CCD detection to the nanosecond timescale [33,34].…”

Measurement the Spectroscopic Temperature of Electron in Aluminum Laser Induced Plasma

“…The ratio for intensity of two lines of the same species of ionization stage Z in the emission spectrum of the target ablated b laser is expressed as: where I 1 is the line intensity from the k-i transition (arbitrary unit), I 2 is that from the nm transition (arbitrary unit), is the wavelength from the k-i transition (nm), is the wavelength from the n-m transition (nm), is the transition probability from the k-i transition (s -1 ) , is the transition probability from the n-m transition (s -1 ), is the statistical weight of the k state, is the statistical weight of the n state, is the energy of the k state (eV), is the energy of the n state (eV), k B is the Boltzmann constant 1.38x10 -23 J.K -1 , and T e is the electron temperature (eV). From equation (1) we can find the electron temperature T e by comparison of two spectral lines in the emission spectrum [10]. The aim of this research is to estimate electron temperature T e of plasma produced by Nd:YAG pulsed laser of Al element which can be used in many application such as electroptics devices and semiconductors alloys.…”

“…By increasing the fluence over the ablation threshold, the saturation of the produced plasma density allows the increase of the ions and electrons temperatures [7]. Because of the transient features of the plasma created by LIP, optical emission spectroscopy (OES) technique with time and space resolution is especially used to obtain information about the behavior of the created plasma species in space and time as well as the dynamics of the plasma evolution [8][9][10]. The ratio for intensity of two lines of the same species of ionization stage Z in the emission spectrum of the target ablated b laser is expressed as: where I 1 is the line intensity from the k-i transition (arbitrary unit), I 2 is that from the nm transition (arbitrary unit), is the wavelength from the k-i transition (nm), is the wavelength from the n-m transition (nm), is the transition probability from the k-i transition (s -1 ) , is the transition probability from the n-m transition (s -1 ), is the statistical weight of the k state, is the statistical weight of the n state, is the energy of the k state (eV), is the energy of the n state (eV), k B is the Boltzmann constant 1.38x10 -23 J.K -1 , and T e is the electron temperature (eV).…”

Shockwave and cavitation bubble dynamics of atmospheric air

“…The crucial issue involved in efficient coupling of optical energy is the interaction of high power laser beams with materials, which is an intriguing field of research owing to the nonlinear optical properties coming to the fore during laser-matter interaction. In the study of laser induced shockwaves in ambient conditions and in under dense plasmas, the existing theoretical and experimental reports mostly consider the SWs emanate from a single point source [6][7][8] and neglects the self-focusing of laser pulses interacting with the plasma. To address this issue, we present our results from the SHW imaging technique revealing the dynamics of LISW and hot core plasma (HCP) from LPP in air generated with 7 ns laser pulses which gives the full spatial information of the evolution of the position of SW fronts and expansion of the hot gas.…”