Spectroscopic Analysis of Copper Oxide by Laser-Induced Breakdown Spectroscopyin the Presence and Absence of a Magnetic Field

[摘要] Laser-induced breakdown spectroscopy of CuO plasma in the presence and absence of magnetic field has been investigated. The plasma was generated by employing Nd: YAG laser (532 nm, 9 ns) at various pulse laser energy ranging from 100 to 400 mj in a vacuum. The increasing of pulse laser energy in the presence and absence of the magnetic field had shown increasing in electron density while the electron temperature was decreases. The presence of the magnetic field cause to a rising the electron density but it reduces the electron temperature comparison with the case of absence of the magnetic field. According to theβ value distribution along the target, the results shows in the central region of the target the plasma plump that produced by laser is in a good confinement in this region in contrasted with edge region of the target region.

[关键词] LIBS;Magnetic field confinement;Electron temperature;OES;Electron density Introduction Laser-induced breakdown spectroscopy (LIBS) is an analytical technique based on the application of one or more high power laser pulses on a reduced region of the sample surface;promoting ablation and excitation of the specimen with the formation of a transient plasma. In the technique;the emitted radiation is associated with the sample chemical composition and is monitored by means of an appropriate detection system (wavelength selector and detector) [1]. Laser-produced plasma is transient in nature with characteristic parameters that evolve quickly and are strongly dependent on irradiation conditions such as incident laser Intensity and pulse duration;laser wavelength;irradiation spot size;ambient gas composition;and ambient pressure [2;3]. In recent years;the use of the magnetic field to confine the laser-produced plasma has become significantly important. The magnetic field can be used to control the dynamical properties of transient and energetic plasmas inefficient ways. The high-intensity pulsed magnetic fields have been found useful in enhancing the emission from laser-induced breakdown plasma [4]. The expansion of laser-induced plasma in the presence of magnetic field may initiate several physical phenomena including plume confinement;Joule heating effect;conversion of plasma thermal energy into kinetic energy;plasma instabilities;emission enhancement [5]. Dynamics of laser-produced plasma play an important role in deciding the characteristics of the plasma [6-8]. The degree of plasma confinement was in good agreement with simple magnetohydrodynamic (MHD) modeling [9]. Optical Emission Spectroscopy (OES) has been used for years to determine the plasma parameters such as electron density (ne);electron temperature (Te) and plasma frequency ωp [7]. The electron density in general;specifies the state of thermo- dynamical equilibrium of the plasma;while the temperature determines the strength of the different distribution functions describing the plasma state. The electron temperature of plasma was calculated using Boltzmann plot method [8]: