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RISS 인기검색어
- 검색키워드
- 저자 : Walid Tawfik (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Damage Profile of HDPE Polymer using Laser-Induced Plasma
Walid Tawfik,W Aslam Farooq,Z. A. Alahmed 한국광학회 2014 Current Optics and Photonics Vol.18 No.1
In this paper we studied the laser-induced crater depth, mass, and emission spectra of laser-ablated high-density polyethylene (HDPE) polymer using the laser-induced plasma spectroscopy (LIPS) technique. This study was performed using a Nd:YAG laser with 100 mJ energy and 7 ns pulse width, focused normal to the surface of the sample. The nanoscale change in ablated depth versus number of laser pulses was studied. By using scanning electron microscope (SEM) images, the crater depth and ablated mass were estimated. The LIPS spectral intensities were observed for major and minor elements with depth. The comparison between the LIPS results and SEM images showed that LIPS could be used to estimate the crater depth, which is of interest for some applications such as thin-film lithography measurements and online measurements of thickness in film deposition techniques.
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Mohamed, Walid Tawfik,Chen, Guanglong,Kim, Jaehoon,Tao, Geng Xiao,Ahn, Jungkwen,Kim, Dong Eon Optical Society of America 2011 Optics express Vol.19 No.17
<P>We report the observation of longitudinally uniform plasma waveguide with a controlled length of up to nearly 5 mm, in argon clustered gas jet. This self-channeling plasma is obtained using a 35 mJ, 30 fs FWHM pulse as a pump laser pulse to create the plasma channel. A 1 mJ pulse of the same laser is used for probing the plasma channels using interferometric diagnostics. The radial distribution of the electron density confirms the formation of a plasma waveguide. Clustered argon enhances the absorption efficiency of femtosecond pulses which enables the use of pump pulses of only 35 mJ, approximately 10 times less energy than required for heating conventional gas targets. The plasma channel length is controlled by the laser focus point (F), the laser intensity (I), the pump-probe delay time (t) and the laser height from a nozzle (z). The variation of the electron density for these parameters is also studied. We found that the highest density of 1.2 x 10(19) cm(-3) was obtained at I = 5.2 x 10(16) W/cm(2), z = 2 mm and t = 7.6 ns. It was demonstrated that by using a clustered jet, both the plasma waveguide length and the plasma density could be controlled.</P>
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Qualitative Analysis and Plasma Characteristics of Soil from a Desert Area using LIBS Technique
W Aslam Farooq,Walid Tawfik,Fahad N. AL-Mutairi,Zeyad A. Alahmed 한국광학회 2013 Current Optics and Photonics Vol.17 No.6
In this work, laser induced breakdown spectroscopy (LIBS) is used to investigate soil samples collectedfrom different desert areas of Riyadh city in Saudi Arabia. Both qualitative analysis and plasma parametersare studied via the observed LIBS spectra. These experiments have been done using a Spectrolaser-7000system with 50 mJ fundamental wavelength of Nd:YAG laser and detection delay time of 1 microsecond. Many spectral lines are highly resolved for many elements like Al, Fe, Mg, Si, Mn, Na, Ca and K. Theelectron temperatures Te and electron densities Ne, for the constituent of generated LIBS plasma, aredetermined for all the collected samples. It is found that both Te and Ne vary from one desert area toother. This variation is due to the change of the elemental concentration in different desert areas that affectsthe sample’s matrices. Time dependent measurements have also been performed on the soil samples. Whilethe signal-to-base ratio (SBR) reached its optimal value at 1 microsecond, the plasma parameters Ne andTe reach values of 4×1017cm-3and 9235 K, respectively, at 2.5 microsecond. The later indicate that theplasma cooling processes are slow in comparison to the previously observed results for metallic samples. The observed results show also that in the future it is possible to enhance the exploitation of LIBS inthe remote on-line environmental monitoring application, by following up only the values of Ne and Tefor one element of the soil desert sample using an optical fiber probe.
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