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Radiation-Induced Nano-Explosions at the Solid Surface: Near Surface Radiation Damage in CR-39 Polymer

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Chinese Physics Letters 2011年第8期28卷 83-86页

作者： mukhtar ahmed rana Physics Division Pakistan Institute of Nuclear Science and Technology(PINSTECH)P.O.NiloreIslamabadPakistan

New measurements of fission fragment and alpha particle induced surface damage in the most sensitive and commonly used nuclear track detector CR-39 are presented *** designed and optimized exposure and chemical etching experiments are employed to unfold the structure of radiation induced surface damage(RISD).Delay in the startup of the chemical etching of latent tracks or surface radiation damage is measured and is found to contain important information about the structure of the surface *** atomic scale pictures of RISD and its chemical etching are developed in an empirical *** model and experimental findings coherently compose a realistic picture of early or femtosecond evolution of RISD.

关键词： coherent finding damage

Planar Channelling Criticalities of MeV Protons in Si Crystal： Simulations, Evaluation and Applications

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Chinese Physics Letters 2008年第10期25卷 3724-3727页

作者： mukhtar ahmed rana Methodology Applications Initiative Physics Division PINSTECH Post Office Nilore Islamabad Pakistan

We reports a phase-space structure of MeV proton beam planar channelled along {110} planes in Si crystal using simulation results with the help of a computer code FLUX. The aim is to understand channelling conditions suitable for disorder measurement in crystals. Phase-space distribution of a planar channelled proton beam evolutes in a systematic fashion when it travels into the crystal. Planar channelled beam oscillates between phase-like and space-like conditions in which a part of the beam becomes under phase and space criticalities. These criticality conditions in planar channelling are analysed, explained and discussed with the perspective of defect measurement in crystals.

关键词： the power-law exponents precipitation durative abrupt precipitation change

Microscopic model for chemical etchability along radiation damage paths in solids

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Nuclear Science and Techniques 2008年第3期19卷 174-177页

作者： mukhtar ahmed rana Physics Division Directorate of Science PINSTECH P.O. Nilore Islamabad Pakistan

It would be very interesting to develop a picture about removal of atoms from the radiation damaged paths or latent nuclear tracks and undamaged bulk material in track detectors. Here, theory of chemical etching is described briefly and a new model for chemical etching along radiation damaged paths in solids is developed based on basic scientific facts and valid assumptions. Dependence of chemical etching on radiation damage intensity and etching conditions is discussed. A new parameter for etching along radiation damaged paths is introduced, which is useful for investigation of relationship between chemical etchability and radiation damage in a solid. Results and discussion presented here are also useful for further development of nuclear waste immobilization.

关键词：固态径迹探测器晶体缺陷辐射损伤固体

A compound spike model for formation of nuclear tracks in solids

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Nuclear Science and Techniques 2007年第6期18卷 349-353页

作者： mukhtar ahmed rana Physics Division Directorate of SciencePINSTECHP.O.NiloreIslamabadPakistan

Formation of nuclear tracks in solids has been described as a thermal spike as well as a Coulomb explo- sion ***,formation of nuclear tracks is described as a compound spike including partial roles of both thermal and Coulomb explosion spikes in track *** roles of both spikes depend on atomic and electronic structure of a track detector and deposited energy density in the track detector by the incident charged ***- havior of the cylindrical zone along the path of the incident particle is described mathematically in terms of bulk and individual atomic flow or *** structure of the latent nuclear tracks is described and conditions of con- tinuity and discontinuity of latent tracks are evaluated and *** paper includes mathematical description, analysis and evaluation of the nuclear track formation issue in the light of published experimental and theoretical re- sults,which are useful for users of nuclear track detection technique and researchers involved in ion beam induced materials modification and ions implantation in semiconductors.

关键词：核子轨道探测技术晶体固态径迹探测探测方法

Challenges in spent nuclear fuel final disposal:conceptual design models

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Nuclear Science and Techniques 2008年第2期19卷 117-120页

作者： mukhtar ahmed rana Physics Division Directorate of SciencePINSTECHP.O.NiloreIslamabadPakistan

The disposal of spent nuclear fuel is a long-standing issue in nuclear ***,UO_2 and metallic U arc used as a fuel in nuclear *** nuclear fuel contains fission products and transuranium elements,which would remain radioactive for 10~4 to 10~8 *** this brief communication,essential concepts and engineering elements related to high-level nuclear waste disposal are *** design models are described and discussed considering the long-time scale activity of spent nuclear fuel or high level *** of physical and chemical barriers to contain nuclear waste are *** regarding integrity,self-irradiation induced decomposition and thermal effects of decay heat on the spent nuclear fuel are also *** question of retrievability of spent nuclear fuel after disposal is considered.

关键词：核燃料概念设计模型自我辐射分解热反应

Total Fragmentation Cross Section of 158A GeV Lead Projectiles in Cu Target

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Chinese Physics Letters 2008年第9期25卷 3208-3211页

作者： mukhtar ahmed rana Shahid Manzoor Physics Division Directorate of Science PINSTECH PO Nilore Islamabad Pakistan

Total fragmentation cross section for the reaction 158A Pb ions ＋ Cu target is measured using the most sensitive track detector CR-39. Measured values are compared with calculations. Exposures of target-detector stack with 158A P5 projectiles are made at CERN-SPS beam facility. Results of calibration of CR-39 detector in a charge region （63 ≤ Z ≤ 83） are also reported, which can be used for high energy particle identification using CR-39 and in determination of partial charge changing cross sections. The charge resolution δz achieved by this technique is about 0.2e. A systematic dependence of total fragmentation cross section on target properties is revealed and the corresponding results are presented.

关键词： the power-law exponents precipitation durative abrupt precipitation change

Fission of Weakly Prolate 119Sn and Weakly Oblate ^(209)Bi Nuclei Induced by 500 and 672 MeV Negative Pions

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Chinese Physics Letters 2011年第9期28卷 88-91页

作者： mukhtar ahmed rana Gul Sher Shahid Manzoor M.I.Shahzad Physics Division Pakistan Institute of Nuclear Science and Technology(PINSTECH)P.O.NiloreIslamabadPakistan

Fission cross-sections of ^(119)Sn and ^(209)Bi induced by negative pions of two energies 500 and 672 MeV were measured using a CR−39 nuclear track ***-detector stacks were exposed to pion beams at the Brookhaven National Laboratory(USA).Measurement results are compared with the corresponding calculations using the computer code *** between measurements and calculations is fairly good for the ^(209)Bi target nuclei whereas it is poor for 119Sn at both investigated energies of 500 and 672 *** cross−section results of^( 119)Sn and ^(209)Bi are explained using the equilibrium properties of these nuclides including nuclear electric quadrupole moments which determine the shapes of nuclei.A logarithmic dependence of fission cross−section on Z^(2)/A is observed for the above−mentioned reactions and a critical limit of Z^(2)/A is identified with the value of 30 which divides the curve ofσf versus Z2/A into two regimes,one with weak dependence and the other with strong dependence.

关键词： Weakly mentioned limit

New Method for Diagnostics of Ion Implantation Induced Charge Carrier Traps in Micro- and Nanoelectronic Devices

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World Journal of Nuclear Science and Technology 2012年第4期2卷 174-180页

作者： mukhtar ahmed rana Physics Department International Islamic University Kashmir Highways Islamabad Pakistan

An important problem of defect charging in electron-hole plasma in a semiconductor electronic device is investigated using the analogy of dust charging in dusty plasmas. This investigation yielded physical picture of the problem along with the mathematical model. Charging and discharging mechanism of charge carrier traps in a semiconductor elec-tronic device is also given. Potential applications of the study in semiconductor device technology are discussed. It would be interesting to find out how dust acoustic waves in electron-hole plasma in micro and nanoelectronic devices can be useful in finding out charge carrier trap properties of impurities or defects which serve as dust particles in elec-tron-hole (e-h) plasma. A new method based on an established technique “deep level transient spectroscopy” (DLTS) is described here suggesting the determination of properties of charge carrier traps in present and future semiconductor devices by measuring the frequency of dust acoustic waves (DAW). Relationship between frequency of DAW and properties of traps is described mathematically proposing the basis of a technique, called here, dust mode frequency deep level transient spectroscopy (DMF-DLTS).

关键词： Semiconductors Ion Implantation Defects Dust Acoustic Waves Deep Level Transient Spectroscopy Electron-Hole Plasma Nanoelectronics

High-Level Nuclear Wastes and the Environment: Analyses of Challenges and Engineering Strategies

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World Journal of Nuclear Science and Technology 2012年第3期2卷 89-105页

作者： mukhtar ahmed rana Physics Division Directorate of Science PINSTECH Islamabad Pakistan

The main objective of this paper is to analyze the current status of high-level nuclear waste disposal along with presentation of practical perspectives about the environmental issues involved. Present disposal designs and concepts are analyzed on a scientific basis and modifications to existing designs are proposed from the perspective of environmental safety. A new concept of a chemical heat sink is introduced for the removal of heat emitted due to radioactive decay in the spent nuclear fuel or high-level radioactive waste, and thermal spikes produced by radiation in containment materials. Mainly, UO2 and metallic U are used as fuels in nuclear reactors. Spent nuclear fuel contains fission products and transuranium elements which would remain radioactive for 104 to 108years. Essential concepts and engineering strategies for spent nuclear fuel disposal are described. Conceptual designs are described and discussed considering the long-term radiation and thermal activity of spent nuclear fuel. Notions of physical and chemical barriers to contain nuclear waste are highlighted. A timeframe for nuclear waste disposal is proposed and time-line nuclear waste disposal plan or policy is described and discussed.

关键词： High-Level Nuclear Waste Nuclear Waste Containment and Disposal Environment Conceptual Model Designs Radioactivity Damage Chemical Heat Sink