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Low Energy Plasma Focus as an Intense X-ray Source for Radiography

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Plasma Science and Technology 2004年第3期6卷 2296-2300页

作者： S.Hussain m.zakaullah Shujaat Ali A.Waheed Department of Physics Quaid-i-Azam University 45320 Islamabad PakistanDepartment of Physics Quaid-i-Azam University 45320 Islamabad PakistanDepartment of Physics Quaid-i-Azam University 45320 Islamabad PakistanPINSTECH P. O. Box 2151 44000 Islamabad Pakistan

Study on X-ray emission from a low energy (1.8 kJ) plasma focus devicepowered by a 9 μF capacitor bank, charged at 20 kV and giving peak discharge current of about 175kA by using a lead-inserted copper-tapered anode is reported. The X-ray yield in different energywindows is measured as a function of hydrogen filling pressure. The maximum yield in 4π-geometry isfound to be (27.3+-1.1) J and corresponding wall plug efficiency for X-ray generation is 1.52+-0.06%. X-ray emission, presumably due to bombarding activity of electrons in current sheath at theanode tip was dominant, which is confirmed by the pinhole images. The feasibility of the device asan intense X-ray source for radiography is demonstrated.

关键词： plasma focus X-ray source radiography

Comparative Study of Plasma Parameters in magnetic Pole Enhanced Inductively Coupled Argon Plasmas

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Plasma Science and Technology 2013年第4期15卷 329-334页

作者： F.JAN A.W. KHAN A.SAEED m.zakaullah Department of Physics Quaid-i-Azam University Department of Physics Gomal University

Langmuir probe measurements of radio frequency （RF） magnetic pole enhanced inductively coupled （maPE-ICP） argon plasma were accomplished to obtain the electron number densities and electron temperatures. The measurements were carried out with a fixed RF frequency of 13.56 mHz in a pressure range of 7.5 mTorr to 75 mTorr at an applied RF power of 10 W and 100 W. These results are compared with a global （volume average） model. The results show good agreement between theoretical and experimental measurements. The electron number density shows an increasing trend with both RF power and pressure while the electron temperature shows decreasing trend as the pressure increases. The difference in the plasma potentim and floating potential as a function of electron temperature measured from the electrical probe and that obtained theoretically shows a linear relation with a small difference in the coefficient of proportionality. The intensity of the emission line at 750.4 nm due to 2pl → 1s2 （Paschen＇s notation） transition closely follows the variation of ne with RF power and filling gas pressure. measured electron energy probability function （EEPF） shows that electron occupation changes mostly in the high-energy tail, which highlights close similarity of 750.4 nm argon line to he.

关键词： maPE-ICP Langmuir probe global model

Glow Discharge Plasma Nitriding of AISI 304 Stainless Steel

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Plasma Science and Technology 2007年第4期9卷 463-468页

作者： A.QAYYUm m.A.NAVEED S.ZEB G.mURTAZA m.zakaullah National Tokamak Fusion Program IslamabadPakistan Department of Physics Quaid-i-Azam University45320 IslamabadPakistan Salam Chair in Physics Government College University54000 LahorePakistan

Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples were analysed by X-ray diffraction （XRD） to explore the changes induced in the crystallographic structure. The XRD pattern confirmed the formation of an expanded austenite phase （TN） owing to incorporation of nitrogen as an interstitial solid solution in the iron lattice. A Vickers microhardness tester was used to evaluate the surface hardness as a function of indentation depth （μm）. The results showed clear evidence of surface changes with substantial increase in surface hardness.

关键词： optical diagnostics plasma nitriding austenitic stainless steel

Pulsed ion beam-assisted carburizing of titanium in methane discharge

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Chinese Physics B 2010年第1期19卷 247-256页

作者： m.Shafiq m.Hassan K.Shahzad A.Qayyum S.Ahmad R.S.Rawat m.zakaullah Department of Physics Quaid-i-Azam University Department of Physics GC University National Tokamak Fusion Program Natural Sciences and Science Education National Institute of EducationNanyang Technological University

The carburizing of titanium （Ti） is accomplished by utilizing energetic ion pulses of a 1.5 kJ mather type dense plasma focus （DPF） device operated in methane discharge. X-ray diffraction （XRD） analysis confirms the deposition of polycrystalline titanium carbide （TIC）. The samples carburized at lower axial and angular positions show an improved texture for a typical （200）TIC plane. The Williamson-Hall method is employed to estimate average crystallite size and microstrains in the carburized Ti surface. Crystallite size is found to vary from - 50 to 100 nm, depending on the deposition parameters. microstrains vary with the sample position and hence ion flux, and are converted from tensile to compressive by increasing the flux. The carburizing of Ti is confirmed by two major doublets extending from 300 to 390 cm^-1 and from 560 to 620 cm^-1 corresponding to acoustic and optical active modes in Raman spectra, respectively. Analyses by scanning electron microscopy/energy dispersive x-ray spectroscopy （SEm/EDS） have provided qualitative and quantitative profiles of the carburized surface. The Vickers microhardness of Ti is significantly improved after carburizing.

关键词： carbide plasma focus microstructure surface morphology

Investigation of 50 Hz Pulsed DC Nitrogen Plasma with Active Screen Cage by Trace Rare Gas Optical Emission Spectroscopy

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Plasma Science and Technology 2014年第4期16卷 324-328页

作者： A.SAEED A.W.KHAN m.SHAFIQ F.JAN m.ABRAR m.ZAKA-UL-ISLAm m.zakaullah Department of Physics Gomal University Department of Physics Quaid-i-Azam University Department of Physics Hazara University Mansehra Plasmant Department of Chemistry Univesity of Antwerp campus DriEkin

Optical emission spectroscopy is used to investigate the nitrogen-hydrogen with trace rare gas （4% Ar） plasma generated by 50 Hz pulsed DC discharges. The filling pressure varies from 1 mbar to 5 mbar and the current density ranges from 1 mA-cm-2 to 4 ***-2. The hydrogen concentration in the mixture plasma varies from 0% to 80%, with the objective of identifying the optimum pressure, current density and hydrogen concentration for active species （[N] and IN2]） generation. It is observed that in an N2-H2 gas mixture, the concentration of N atom density decreases with filling pressure and increases with current density, with other parameters of the discharge kept unchanged. The maximum concentrations of active species were found for 40% H2 in the mixture at 3 mbar pressure and current density of 4 ***-2.

关键词： TRG-OES DC glow discharge reactive species

Optimization Study of Pulsed DC Nitrogen-Hydrogen Plasma in the Presence of an Active Screen Cage

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Plasma Science and Technology 2014年第5期16卷 460-464页

作者： A.SAEED A.W.KHAN F.JAN H.U.SHAH m.ABRAR m.ZAKA-UI-ISLAm m.KHALID m.zakaullah National Centre for Physics Quaid-i-Azam University Campus Islamabad Department of Physics Gomal University Department of Physics Quaid-i-Azam University Department of Physics Hazara University Mansehra Department of Physics Faculty of ScienceUniversity of Jazan

A glow discharge plasma nitriding reactor in the presence of an active screen cage is optimized in terms of current density,filling pressure and hydrogen concentrations using optical emission spectroscopy（OES）.The samples of AISI 304 are nitrided for different treatment times under optimum *** treated samples were analyzed by X-ray diffraction（XRD） to explore the changes induced in the crystallographic *** XRD pattern confirmed the formation of iron and chromium nitrides arising from incorporation of nitrogen as an interstitial solid solution in the iron lattice.A Vickers microhardness tester was used to evaluate the surface hardness as a function of treatment time（h）.The results showed clear evidence of improved surface hardness and a substantial amount of decrease in the treatment time compared with the previous work.

关键词： optical diagnostics plasma nitriding austenitic stainless steel

Trace-Rare-Gas Optical Emission Spectroscopy of Nitrogen Plasma Generated at a Frequency of 13.56 mHz

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Plasma Science and Technology 2011年第2期13卷 208-212页

作者： N.U.REHmAN F.U.KHAN S.NASEER G.mURTAZA S.S.HUSSAIN I.AHmAD m.zakaullah Department of Physics COMSATS Institute of Information Technology Department of Physics Gomal University Department of Physics Peshawar University Department of Physics Quaid-i-Azam University

Optical emission spectroscopic measurement of trace rare gas is carried out to determine the density of nitrogen （N） atom, in a nitrogen plasma, as a function of filling pressure and RF power applied. 2% of argon, used as an actinometer, is mixed with nitrogen. In order to normalize the changes in the excitation cross section and electron energy distribution function at different operational conditions, the Ar-I emission line at 419.83 nm is used, which is of nearly the same excitation efficiency coefficient as that of the nitrogen emission line at 493.51 nm. It is observed that the emission intensity of the selected argon and atomic nitrogen lines increases with both pressure and RF power, as does the nitrogen atomic density.

关键词： optical actinometry N atomic density EEDF RF plasma

Evolution of plasma parameters in an Ar-N2/He inductive plasma source with magnetic pole enhancement

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Plasma Science and Technology 2017年第2期19卷 34-42页

作者： maria YOUNUS N U REHmAN m SHAFIQ m NAEEm m ZAKA-UL-ISLAm m.zakaullah Department of Physics Plasma Physics LaboratoryQuaid-i-Azam University45320 IslamabadPakistan Plasma Physics Laboratory Department of PhysicsCOMSATS Institute of Information Technology44000 IslamabadPakistan Department of Physics Faculty of ScienceJazan University114 JazanSaudi Arabia

magnetic pole enhanced inductively coupled plasmas （maPE-ICPs） are a promising source for plasma-based etching and have a wide range of material processing applications. In the present study Langmuir probe and optical emission spectroscopy were used to monitor the evolution of plasma parameters in a maPE-ICP Ar-Na/He mixture plasma. Electron density （ne） and temperature （Te）, excitation temperature （Texc）, plasma potential （Vp）, skin depth （6） and the evolution of the electron energy probability function （EEPF） are reported as a function of radiofrequency （RF） power, pressure and argon concentration in the mixture. It is observed that ne increases while Te decreases with increase in RF power and argon concentration in the mixture. The emission intensity of the argon line at 750.4 nm is also used to monitor the variation of the ‘high-energy tail＇ of the EEPF with RF power and gas pressure. The EEPF has a ‘bi-maxwellian＇ distribution at low RF powers and higher pressure in a pure N2 discharge. However, it evolves into a ‘maxwellian＇ distribution at RF powers greater than 70 W for pure N2, and at 50 W for higher argon concentrations in the mixture. The effect of argon concentration on the temperatures of two electron groups in the ‘bi-maxwellian＇ EEPF is examined. The temperature of the low-energy electron group TL shows a decreasing trend with argon addition until the ‘thermalization＇ of the two temperatures occurs, while the temperature of high-energy electrons Ta decreases continuously.

关键词： maPE-ICP Langmuir probe OES EEPF

Nonlinear forced vibration in a subcritical regime of a porous functionally graded pipe conveying fluid with a retaining clip

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Applied mathematics and mechanics(English Edition) 2025年第1期46卷 101-122页

作者： m.GHOLAmI m.EFTEKHARI Department of mechanical Engineering Shahid Bahonar University of Kerman

This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGm) that conveys fluids and is equipped with a retaining clip, focusing on primary resonance and subcritical dynamics. The nonlinear governing equations for the FGm pipe are derived by the extended Hamilton's principle, and subsequently discretized through the application of the Galerkin *** direct method of multi-scales is then used to solve the derived equations. A thorough analysis of various parameters, including the clip stiffness, the power-law index, the porosity, and the clip location, is conducted to gain a comprehensive understanding of the system's nonlinear dynamics. Through the analysis of the first natural frequency, the study highlights the influence of the flow velocity and the clip stiffness, while the comparisons with metallic pipes emphasize the role of FGm composition. The examination of the forced response curves reveals saddle-node bifurcations and their dependence on parameters such as the detuning parameter and the power-law index, offering valuable insights into the system's nonlinear resonant behavior. Furthermore, the frequency-response curves illustrate the hardening nonlinearities influenced by factors such as the porosity and the clip stiffness, revealing nuanced effects on the system response and resonance characteristics. This comprehensive analysis enhances the understanding of nonlinear behaviors in FGm porous pipes with a retaining clip, providing key insights for practical engineering applications in system design and optimization.

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