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  Subjects -> PHYSICS (Total: 736 journals)
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PHYSICS (623 journals)            First | 1 2 3 4 5 6 7 | Last

Meccanica     Hybrid Journal   (1 follower)
Mechanics of Advanced Materials and Structures     Hybrid Journal   (3 followers)
Mechanics of Materials     Hybrid Journal   (11 followers)
Mechanics of Solids     Hybrid Journal   (1 follower)
Mechanics of Time-Dependent Materials     Hybrid Journal   (1 follower)
Mechanics Research Communications     Hybrid Journal   (2 followers)
Metal Science and Heat Treatment     Hybrid Journal   (8 followers)
Metamaterials     Hybrid Journal   (2 followers)
Micro and Nano Systems Letters     Open Access   (1 follower)
Microfluidics and Nanofluidics     Hybrid Journal   (9 followers)
Microporous and Mesoporous Materials     Hybrid Journal   (3 followers)
Modern Instrumentation     Open Access   (2 followers)
Modern Physics Letters A     Hybrid Journal   (1 follower)
Modern Physics Letters B     Hybrid Journal  
Molecular Diversity     Hybrid Journal  
Moscow University Mechanics Bulletin     Hybrid Journal  
Moscow University Physics Bulletin     Hybrid Journal   (1 follower)
Multibody System Dynamics     Hybrid Journal  
NANO     Hybrid Journal   (6 followers)
Nano Letters     Full-text available via subscription   (37 followers)
Nano Reviews     Open Access   (15 followers)
Nanoscale and Microscale Thermophysical Engineering     Hybrid Journal   (3 followers)
Nanoscale Research Letters     Open Access   (4 followers)
Nanotechnology Magazine, IEEE     Full-text available via subscription   (12 followers)
Natural Science     Open Access   (9 followers)
Nature Communications     Hybrid Journal   (35 followers)
Nature Materials     Full-text available via subscription   (33 followers)
Nature Photonics     Full-text available via subscription   (13 followers)
Nature Physics     Full-text available via subscription   (22 followers)
NDT & E International     Hybrid Journal   (10 followers)
NEUTRINO     Open Access  
Neutron News     Hybrid Journal  
New Journal of Physics     Open Access   (7 followers)
Niels Bohr Collected Works     Full-text available via subscription  
Noise & Vibration Worldwide     Full-text available via subscription   (5 followers)
Noise Notes     Full-text available via subscription   (3 followers)
Nondestructive Testing And Evaluation     Hybrid Journal   (3 followers)
Nonlinear Dynamics     Hybrid Journal   (5 followers)
NTM Zeitschrift für Geschichte der Wissenschaften, Technik und Medizin     Hybrid Journal   (4 followers)
Nuclear Engineering and Design     Hybrid Journal   (11 followers)
Nuclear Fusion     Full-text available via subscription   (1 follower)
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment     Hybrid Journal   (5 followers)
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms     Hybrid Journal   (6 followers)
Nuclear Medicine and Biology     Hybrid Journal   (1 follower)
Nuclear Physics A     Hybrid Journal   (2 followers)
Nuclear Physics B     Open Access   (1 follower)
Nuclear Physics B - Proceedings Supplements     Hybrid Journal  
Nuclear Physics News     Hybrid Journal  
Nuclear Receptor     Full-text available via subscription   (1 follower)
Open Journal of Biophysics     Open Access   (1 follower)
Open Journal of Fluid Dynamics     Open Access   (3 followers)
Open Journal of Microphysics     Open Access  
Optical Communications and Networking, IEEE/OSA Journal of     Hybrid Journal   (3 followers)
Optical Engineering     Full-text available via subscription   (6 followers)
Optics and Photonics Letters     Open Access   (3 followers)
Optics Express     Open Access   (12 followers)
Optics Letters     Full-text available via subscription   (4 followers)
Optoelectronics Letters     Hybrid Journal  
Organic Electronics     Hybrid Journal   (3 followers)
PAJ: A Journal of Performance and Art     Hybrid Journal   (10 followers)
Particle Physics Insights     Open Access   (1 follower)
Particuology     Hybrid Journal  
Pattern Recognition in Physics     Open Access   (1 follower)
Pergamon Materials Series     Full-text available via subscription  
Phase Transitions and Critical Phenomena     Full-text available via subscription   (1 follower)
Philosophical Magazine     Hybrid Journal   (2 followers)
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences     Full-text available via subscription   (7 followers)
Philosophy and Foundations of Physics     Full-text available via subscription  
Photonics and Optoelectronics     Open Access   (1 follower)
Photonics Journal, IEEE     Full-text available via subscription   (5 followers)
Photonics Letters of Poland     Open Access  
Physica A: Statistical Mechanics and its Applications     Hybrid Journal   (6 followers)
Physica B: Condensed Matter     Hybrid Journal   (4 followers)
physica status solidi (a)     Hybrid Journal   (1 follower)
physica status solidi (b)     Hybrid Journal   (1 follower)
physica status solidi (c)     Hybrid Journal   (1 follower)
Physica Status Solidi - Rapid Research Letters     Hybrid Journal  
Physical Acoustics     Full-text available via subscription   (1 follower)
Physical Communication     Hybrid Journal  
Physical Mesomechanics     Hybrid Journal  
Physical Review C     Full-text available via subscription   (15 followers)
Physical Review Special Topics - Physics Education Research     Open Access   (5 followers)
Physical Review X     Open Access   (5 followers)
Physical Sciences Data     Full-text available via subscription   (1 follower)
Physics - spotlighting exceptional research     Full-text available via subscription  
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (2 followers)
Physics and Chemistry of Liquids: An International Journal     Hybrid Journal  
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (3 followers)
Physics in Medicine & Biology     Full-text available via subscription   (7 followers)
Physics in Perspective     Hybrid Journal   (1 follower)
Physics International     Open Access   (2 followers)
Physics Letters A     Hybrid Journal   (9 followers)
Physics Letters B     Open Access   (2 followers)
Physics of Atomic Nuclei     Hybrid Journal  
Physics of Fluids     Hybrid Journal   (18 followers)
Physics of Life Reviews     Hybrid Journal   (1 follower)
Physics of Particles and Nuclei     Hybrid Journal   (1 follower)
Physics of Particles and Nuclei Letters     Hybrid Journal   (1 follower)
Physics of Plasmas     Hybrid Journal   (6 followers)
Physics of the Dark Universe     Open Access  

  First | 1 2 3 4 5 6 7 | Last

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms    [8 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0168-583X
     Published by Elsevier Homepage  [2556 journals]   [SJR: 0.593]   [H-I: 78]
  • Irradiation resistance properties studies on helium ions irradiated MAX
           phase Ti3AlC2
    • Abstract: Publication date: Available online 22 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): Peng Song , Jianrong Sun , Zhiguang Wang , Minghuan Cui , Tielong Shen , Yuanfei Li , Lilong Pang , Yabin Zhu , Qing Huang , Jinjun Lü
      The study presents an investigation of irradiation resistance properties of Ti3AlC2 under 500keV He ions irradiation with the doses ranging from 5.0×1016 to 1.0×1018 ionscm−2 at certain temperatures, like room temperature (RT), 300 and 500°C. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) are used to study the evolution of structural damage and the behavior of deposited He ions respectively. XRD analysis reveals that for the highest dose irradiation (∼52dpa at peak), no amorphization occurs. And the structural recovery of Ti3AlC2 is more significant accompanied with the gradual disappearance of the irradiation-induced TiC phase as the temperature rises from RT to 300 and to 500°C with the same dose irradiation. TEM observations show that He bubbles appear in the shapes of sphere, string and platelet but no big bubbles are formed for all irradiations. Moreover, no large cracks form in the sample implanted with the highest helium concentration of ∼6.4×105 appm.


      PubDate: 2014-01-24T09:06:49Z
       
  • MeV–GeV ion induced dislocation loops in LiF crystals
    • Abstract: Publication date: Available online 22 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): R. Zabels , I. Manika , K. Schwartz , J. Maniks , R. Grants
      Formation of prismatic dislocation loops and evolution of dislocation structure in LiF crystals irradiated with swift 238U and 36S ions of specific energy 11MeV/u at fluences up to 1013 ionscm−2 has been investigated using chemical etching and AFM. It has been shown that prismatic dislocations are formed in the stage of track overlapping above threshold fluences Φ ≈109 Ucm−2 and Φ ≈1010 Scm−2. The diameter of dislocation loops reaches 600–1000nm for 238U ions and 200nm for 36S ions. The dislocations created by 238U ions are arranged in rows along the direction of ion beam, whereas 36S ions create freely distributed dislocation loops each of them being oriented along the ion beam. The role of dislocations in ion-induced nanostructuring and hardening is discussed.


      PubDate: 2014-01-24T09:06:49Z
       
  • 1.2 MeV/amu Xe ion induced damage recovery in SiC
    • Abstract: Publication date: Available online 23 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): J.H. O’Connell , V.A. Skuratov , A.S. Sohatsky , J.H. Neethling
      The microstructural changes of 4H-SiC samples dual irradiated with either low energy He (10keV) or Ti (220keV) and high energy (167MeV) Xe ions has been studied using cross-sectional transmission electron microscopy. It was found that xenon ions with fluences above 1013 cm−2 restore crystallinity in a heavily damaged partially amorphous zone. No significant damage recovery was observed in fully amorphized layers of silicon carbide apart from a 5% reduction in the amorphous layer thickness.


      PubDate: 2014-01-24T09:06:49Z
       
  • Techniques in helical scanning, dynamic imaging and image segmentation for
           improved quantitative analysis with X-ray micro-CT
    • Abstract: Publication date: Available online 21 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): Adrian Sheppard , Shane Latham , Jill Middleton , Andrew Kingston , Glenn Myers , Trond Varslot , Andrew Fogden , Tim Sawkins , Ron Cruikshank , Mohammad Saadatfar , Nicolas Francois , Christoph Arns , Tim Senden
      This paper reports on recent advances at the micro-computed tomography facility at the Australian National University. Since 2000 this facility has been a significant centre for developments in imaging hardware and associated software for image reconstruction, image analysis and image-based modelling. In 2010 a new instrument was constructed that utilises theoretically-exact image reconstruction based on helical scanning trajectories, allowing higher cone angles and thus better utilisation of the available X-ray flux. We discuss the technical hurdles that needed to be overcome to allow imaging with cone angles in excess of 60°. We also present dynamic tomography algorithms that enable the changes between one moment and the next to be reconstructed from a sparse set of projections, allowing higher speed imaging of time-varying samples. Researchers at the facility have also created a sizeable distributed-memory image analysis toolkit with capabilities ranging from tomographic image reconstruction to 3D shape characterisation. We show results from image registration and present some of the new imaging and experimental techniques that it enables. Finally, we discuss the crucial question of image segmentation and evaluate some recently proposed techniques for automated segmentation.


      PubDate: 2014-01-24T09:06:49Z
       
  • Persistent luminescence, TL and OSL characterization of beta irradiated
           SrAl2O4:Eu2+, Dy3+ combustion synthesized phosphor
    • Abstract: Publication date: Available online 23 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): N.J. Zúñiga-Rivera , R. García , R. Rodríguez-Mijangos , V. Chernov , R. Meléndrez , M. Pedroza-Montero , M. Barboza-Flores
      The persistent luminescence (PLUM), thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of strontium aluminates co-doped with Eu+2 and Dy+3 exposed to beta radiation is reported. The phosphor was synthesized by the combustion synthesis method employing a highly exothermic redox reaction between the metal nitrates [Al(NO3)3, Sr(NO3)2, Eu(NO3)3 and Dy(NO3)3] and organic fuel carbohydrazide (CH6N4O). The long decay PLUM emission, TL and OSL were measured as a function of beta radiation dose. A wide emission band centered at 510nm (green) related to Eu2+ ions and lattice defects were observed for the synthesized samples. The presence of a variety of defects and aggregates were responsible for the observed broad 100°C peaked TL glow curve of the irradiated sample which is composed of several overlapped TL peaks. The existence of multiple trapping levels, with different trapping/detrapping probabilities, is behind the particular features for the PLUM, TL and OSL emissions. We conclude that in the SrAl2O4:Eu2+, Dy3+ phosphors, the low temperature TL peaked around 30–75°C is responsible for the PLUM emission and those around 100°C were related to very stable trapping states which provide suitable radiation storage properties to be used as a PLUM/TL/OSL radiation phosphor.


      PubDate: 2014-01-24T09:06:49Z
       
  • Simulated carbon irradiation of carbon nanotubes – A comparative
           study of interatomic potentials
    • Abstract: Publication date: Available online 23 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): Santiago Heredia-Avalos , Juan Carlos Moreno-Marín , Cristian D. Denton
      We simulate the irradiation of carbon nanotubes (CNT) with carbon ions using a molecular dynamics code. In order to describe the interaction between carbon ions we use the Tersoff or Brenner potential, both joined smoothly to the Universal ZBL potential at short distances. We have analyzed the defects produced after irradiation, the subsequent modification of the CNT structure, and their dependence on the used interatomic potential, the projectile energy (from 10 eV to 5keV) and the dose. For single projectile irradiation, we have obtained that the coordination defect number increases with the projectile energy, although a saturation value is achieved at high projectile energies (∼3keV). For continuous projectile irradiation, we have observed that for low energies (∼10eV) the accumulation of adatoms produces a bump in the irradiated region. However, at intermediate energies (∼100eV) the irradiation produces vacancies which are healed through non-hexagonal rings. This gives rise to a shrinking of the CNT diameter in the irradiated region. Finally, if the projectile energy is high enough (∼1keV) the continuous irradiation produces the breaking of the CNT.


      PubDate: 2014-01-24T09:06:49Z
       
  • Application of X-ray computed micro-tomography to the study of damage and
           oxidation kinetics of thermostructural composites
    • Abstract: Publication date: Available online 22 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): Olivier Caty , Philippe Ibarroule , Mathieu Herbreteau , Francis Rebillat , Eric Maire , Gérard L. Vignoles
      Thermostructural composites are three-dimensionally (3D) structured materials. Weakening phenomena (mechanical and chemical) take place inside the material following its 3D structure and are thus hard to describe accurately. X-ray computed micro-tomography (μCT) is a recent solution that allows their experimental investigation. The technique is applied here to the study of failure under tensile loading and to the self healing processes during oxidation. Results are useful data to verify or invalidate hypotheses or estimations made in current models.


      PubDate: 2014-01-24T09:06:49Z
       
  • The formation of magnetic silicide Fe3Si clusters during ion implantation
    • Abstract: Publication date: Available online 22 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): N. Balakirev , V. Zhikharev , G. Gumarov
      A simple two-dimensional model of the formation of magnetic silicide Fe3Si clusters during high-dose Fe ion implantation into silicon has been proposed and the cluster growth process has been computer simulated. The model takes into account the interaction between the cluster magnetization and magnetic moments of Fe atoms random walking in the implanted layer. If the clusters are formed in the presence of the external magnetic field parallel to the implanted layer, the model predicts the elongation of the growing cluster in the field direction. It has been proposed that the cluster elongation results in the uniaxial magnetic anisotropy in the plane of the implanted layer, which is observed in iron silicide films ion-beam synthesized in the external magnetic field.


      PubDate: 2014-01-24T09:06:49Z
       
  • Corrigendum to “Mechanical and tribological properties of AISI 304
           stainless steel nitrided by glow discharge compared to ion implantation
           and plasma immersion ion implantation” [Nucl. Instrum. Meth. B 257
           (2007) 732–736]
    • Abstract: Publication date: 1 March 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 322
      Author(s): C.E. Foerster , F.C. Serbena , A.C. Zaika , S.L.R. da Silva , C.M. Lepienski , C.J. de M. Siqueira , M. Ueda



      PubDate: 2014-01-24T09:06:49Z
       
  • On the threshold of damage formation in aluminum oxide via electronic
           excitations
    • Abstract: Publication date: Available online 23 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): V.A. Skuratov , J. O’Connell , N.S. Kirilkin , J. Neethling
      This work is aimed to determine the threshold of dense ionization induced damage formation and their morphology in sapphire single crystals irradiated with 1.2MeV/amu Xe ions. Cross-sectional TEM examination of r-oriented Al2O3 specimens irradiated to fluences of 2×1012 and 2×1013 cm−2 has revealed discontinuous ion tracks visible from the irradiated surface up to a depth of 7.6±0.1μm. According to the SRIM code calculation, the threshold electronic stopping power for track formation in Al2O3 is within the range 9.8÷10.5keV/nm. This value agrees with those predicted by both inelastic and analytical thermal spike models.


      PubDate: 2014-01-24T09:06:49Z
       
  • Mechanisms of ion-bombardment-induced DNA transfer into bacterial E. coli
           cells
    • Abstract: Publication date: Available online 23 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): L.D. Yu , K. Sangwijit , K. Prakrajang , B. Phanchaisri , P. Thongkumkoon , P. Thopan , S. Singkarat , S. Anuntalabhochai
      As a useful ion beam biotechnology, ion-bombardment-induced DNA transfer into bacterial Escherichia coli (E. coli) cells has been successfully operated using argon ions. In the process ion bombardment of the bacterial cells modifies the cell envelope materials to favor the exogenous DNA molecules to pass through the envelope to enter the cell. The occurrence of the DNA transfer induction was found ion energy and fluence dependent in a complex manner. At ion energy of a few keV and a few tens of keV to moderate fluences the DNA transfer could be induced by ion bombardment of the bacterial cells, while at the same ion energy but to high fluences DNA transfer could not be induced. On the other hand, when the ion energy was medium, about 10–20keV, the DNA transfer could not be induced by ion bombardment of the cells. The complexity of the experimental results indicated a complex mechanism which should be related to the complex structure of the bacterial E. coli cell envelope. A phase diagram was proposed to interpret different mechanisms involved as functions of the ion energy and fluence.


      PubDate: 2014-01-24T09:06:49Z
       
  • Crystallization of hydrated and anhydrous salts in porous limestone
           resolved by synchrotron X-ray microtomography
    • Abstract: Publication date: Available online 23 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): Hannelore Derluyn , Jan Dewanckele , Matthieu N. Boone , Veerle Cnudde , Dominique Derome , Jan Carmeliet
      The crystallization processes of two anhydrous salts (NaCl and Na2SO4) and one hydrated (sodium sulfate) salt in the pore space of a natural building stone, Savonnières limestone, are studied. We imaged the salt solution distribution before and after crystallization and the solid crystal distribution in between repeated crystallization cycles using synchrotron X-ray microtomography. This technique proves to be very useful to study salt crystallization processes at the pore scale. The use of simultaneous phase-and-amplitude retrieval during X-ray tomographic reconstruction allows a clear segmentation of sodium sulfate solution and hydrated sodium sulfate crystals without the need for a dopant. Salt crystals can precipitate under unconfined as well as confined conditions in the multiple pore systems of Savonnières limestone, depending on their interconnection. Salt solution and salt crystals are located in mechanically weak zones of the limestone, which can be linked to damage patterns observed in this stone after repeated salt weathering cycles. The distribution and the process of pore filling by salt crystals that are revealed here advance the understanding of salt damage in porous media and may open ways to perform remediation.


      PubDate: 2014-01-24T09:06:49Z
       
  • A novel ion-beam-mutation effect application in identification of gene
           involved in bacterial antagonism to fungal infection of ornamental crops
    • Abstract: Publication date: Available online 22 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): S. Mahadtanapuk , W. Teraarusiri , W. Nanakorn , L.D. Yu , P. Thongkumkoon , S. Anuntalabhochai
      This work is on a novel application of ion beam effect on biological mutation. Bacillus licheniformis (B. licheniformis) is a common soil bacterium with an antagonistic effect on Curcuma alismatifolia Gagnep. and Chrysanthemum indicum Linn. In an attempt to control fungal diseases of local crops by utilizing B. licheniformis, we carried out gene analysis of the bacterium to understand the bacterial antagonistic mechanism. The bacterial cells were bombarded to induce mutations using nitrogen ion beam. After ion bombardment, DNA analysis revealed that the modified polymorphism fragment present in the wild type was missing in a bacterial mutant which lost the antifungal activity. The fragments conserved in the wild type but lost in the mutant bacteria was identified to code for the thioredoxin reductase (TrxR) gene. The gene analysis showed that the TrxR gene from B. licheniformis had the expression of the antagonism to fungi in a synchronous time evolution with the fungus inhibition when the bacteria were co-cultivated with the fungi. The collective results indicate the TrxR gene responsible for the antagonism of bacteria B. licheniformis to fungal infection.


      PubDate: 2014-01-24T09:06:49Z
       
  • Thermoluminescence study of Al2O3 and Y3Al5O12 single crystals irradiated
           with reactor neutrons
    • Abstract: Publication date: Available online 23 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): M. Izerrouken , A. Meftah , S. Berkani
      Al2O3 and Y3Al5O12 singles crystals were irradiated by reactor neutrons at about 40°C. After irradiation the generated point defects were investigated by optical absorption, thermoluminescence (TL) and differential scanning calorimetry (DSC) techniques. From the experimental data, it is found that 300nm absorption band observed in Al2O3 and Y3Al5O12 crystals is attributed to Al i + ion and O− - hole center localized near the cation vacancy respectively. It acts as hole traps with activation energies of 1.4 and 1.3eV, respectively. Different annealing steps are observed and discussed in both Y3Al5O12 and Al2O3 crystals.


      PubDate: 2014-01-24T09:06:49Z
       
  • Ion-beam simulation of radiation damage produced by fast neutrons in
           heterophase structures
    • Abstract: Publication date: Available online 22 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): D.I. Tetelbaum , D.V. Guseinov , V.K. Vasiliev , A.N. Mikhaylov , A.I. Belov , D.S. Korolev , S.V. Obolensky , A.N. Kachemtsev
      3D Monte-Carlo algorithm and computer code have been developed that allows choosing and optimizing the conditions of ion irradiation needed for the adequate ion-beam simulation of radiation damage under fast neutron irradiation. It is established that, by the proper selection of energy and dose of Si+ ions, it is possible to reproduce well the effect of irradiation with fission neutrons of subsurface and buried layers of silicon or Si-based 2D and 3D-heterostructures. The results can be used for testing the radiation hardness of silicon-based electronic and optoelectronic device structures.


      PubDate: 2014-01-24T09:06:49Z
       
  • Modeling of defect accumulation in lithium fluoride crystals under
           irradiation with swift ions
    • Abstract: Publication date: Available online 23 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): M.V. Sorokin , K. Schwartz , C. Trautmann , A. Dauletbekova , A.S. El-Said
      In many materials electronic excitations created around the trajectories of swift ions result in defect creation. Experimental observations often yield information on integral damage effects. The presented approach suggests a theoretical model to correlate integral damage results with microscopic effect produced by overlapping of individual single ion tracks. The model is applied to ion-beam induced defects in LiF crystals. Two aspects are treated separately viz. the ion-deposited energy distribution for a given fluence and the material response to the absorbed energy. The first problem is treated within the framework of stochastic superposition of ion tracks, taking into account the radial distribution of the energy transfer of a single ion. For lithium fluoride the creation of color centers is considered as the materials response. The dependence of the defect concentration on the absorbed energy is included in order to obtain the integral defect production.


      PubDate: 2014-01-24T09:06:49Z
       
  • Leaky mode suppression in planar optical waveguides written in
           Er:TeO2–WO3 glass and CaF2 crystal via double energy implantation
           with MeV N+ ions
    • Abstract: Publication date: Available online 24 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): I. Bányász , Z. Zolnai , M. Fried , S. Berneschi , S. Pelli , G. Nunzi-Conti
      Ion implantation proved to be an universal technique for producing waveguides in most optical materials. Tellurite glasses are good hosts of rare-earth elements for the development of fibre and integrated optical amplifiers and lasers covering all the main telecommunication bands. Er3+-doped tellurite glasses are good candidates for the fabrication of broadband amplifiers in wavelength division multiplexing around 1.55μm, as they exhibit large stimulated cross sections and broad emission bandwidth. Calcium fluoride is an excellent optical material, due to its perfect optical characteristics from UV wavelengths up to near IR. It has become a promising laser host material (doped with rare earth elements). Ion implantation was also applied to optical waveguide fabrication in CaF2 and other halide crystals. In the present work first single-energy implantations at 3.5MeV at various fluences were applied. Waveguide operation up to 1.5μm was observed in Er:Te glass, and up to 980nm in CaF2. Then double-energy implantations at a fixed upper energy of 3.5MeV and lower energies between 2.5 and 3.2MeV were performed to suppress leaky modes by increasing barrier width.


      PubDate: 2014-01-24T09:06:49Z
       
  • Experimental approach and atomistic simulations to investigate the
           radiation tolerance of complex oxides: Application to the amorphization of
           pyrochlores
    • Abstract: Publication date: Available online 24 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): G. Sattonnay , L. Thomé , N. Sellami , I. Monnet , C. Grygiel , C. Legros , R. Tetot
      Both experimental approach and atomistic simulations are performed in order to investigate the influence of the composition of pyrochlores on their radiation tolerance. Therefore, Gd2Ti2O7 and Gd2Zr2O7 were irradiated with 4MeV Au and 92MeV Xe ions in order to study the structural changes induced by low and high-energy irradiations. XRD results show that, for both irradiations, the structural modifications are strongly dependent on the sample composition: Gd2Ti2O7 is readily amorphized, whereas Gd2Zr2O7 is transformed into a radiation-resistant anion-deficient fluorite structure. Using atomistic simulations with new interatomic potentials derived from the SMTB-Q model, the lattice properties and the defect formation energies were calculated in Gd2Ti2O7 and Gd2Zr2O7. Calculations show that titanates have a more covalent character than zirconates. Moreover, in Gd2Ti2O7 the formation of cation antisite defects leads to strong local distortions around Ti-defects and to a decrease of the Ti coordination number, which are not observed in Gd2Zr2O7. Thus, the radiation resistance is related to the defect stability: the accumulation of structural distortions around Ti-defects could drive the Gd2Ti2O7 amorphization induced by irradiation.


      PubDate: 2014-01-24T09:06:49Z
       
  • Atomistic simulation of irradiation effects in GaN nanowires
    • Abstract: Publication date: Available online 24 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): Wei Ren , Antti Kuronen , Kai Nordlund
      We have studied effects of ion irradiation in GaN nanowires using classical molecular dynamics simulations. Nanowires with diameters of 3 and 4nm were irradiated with 100 Ar ions at energies of 100eV to 10keV corresponding to ion fluence of about 3 × 10 14 ions/cm2. The structure of the nanowires was analyzed along with sputtering yields and mechanical properties in the form of Young’s modulus. The results show a total sputtering yield of up to 8.3 sputtered atoms per ion and preferential sputtering of nitrogen with gallium to nitrogen ratio approximately 0.7. The Young’s modulus of the nanowires was observed to decrease as a function of the irradiation dose with the largest relative effect observed for ion energies of 1 and 10keV.


      PubDate: 2014-01-24T09:06:49Z
       
  • Poly(vinylbenzyl sulfonic acid)-grafted poly(ether ether ketone) membranes
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): Mi-Lim Hwang , Jisun Choi , Hyun-Su Woo , Vinod Kumar , Joon-Yong Sohn , Junhwa Shin
      In this study, an aromatic hydrocarbon based polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)-grafted poly(ether ether ketone) (PEEK-g-PVBSA), has been prepared by the simultaneous irradiation grafting of vinylbenzyl chloride (VBC) monomer onto a PEEK film and subsequent sulfonation. Each chemical conversion was monitored by FT-IR and SEM–EDX instruments. The physicochemical properties including IEC, water uptake, proton conductivity, and methanol permeability of the prepared membranes were also investigated and found that the values of these properties increase with the increase of degree of grafting. It was observed that the IEC values of the prepared PEEK-g-PVBSA membranes with 32%, 58%, and 80% DOG values were 0.50, 1.05, and 1.22meq/g while the water uptakes were 14%, 20%, and 21%, respectively. The proton conductivities (0.0272–0.0721S/cm at 70°C) were found to be somewhat lower than Nafion 212 (0.126S/cm at 70°C) at a relative humidity of 90%. However, the prepared membranes showed a considerably lower methanol permeability (0.61–1.92×10−7 cm2/s) compared to a Nafion 212 membrane (5.37×10−7 cm2/s).


      PubDate: 2014-01-24T09:06:49Z
       
  • Measurement of cross-sections for produced radionuclide in proton induced
           reactions on natHf up to 45MeV
    • Abstract: Publication date: 1 March 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 322
      Author(s): Muhammad Shahid , Kwangsoo Kim , Haladhara Naik , Guinyun Kim
      We measured production cross-sections of Hf, Lu, and Ta radioisotopes from proton-induced reaction of natHf by using a stacked-foil activation and off-line γ-ray spectrometric technique at the MC-50 cyclotron of the Korea Institute of Radiological and Medical Sciences. The results were compared with the reported experimental data as well as the theoretical calculations based on the TALYS 1.4 code. The present results in the energy region from the threshold energy to 45MeV are in general good agreement with the other experimental data and calculated results. The present experimental results will play an important role in enrichment of the literature data base for proton-induced reactions on natural hafnium leading to various applications. Some of the investigated radionuclides (e.g. 177gLu) have remarkable applications in the field of nuclear medicine, a thin layer activation analysis, and a trace element analysis.


      PubDate: 2014-01-24T09:06:49Z
       
  • Behavioral modeling of SRIM tables for numerical simulation
    • Abstract: Publication date: 1 March 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 322
      Author(s): S. Martinie , T. Saad-Saoud , S. Moindjie , D. Munteanu , J.L. Autran
      This work describes a simple way to implement SRIM stopping power and range tabulated data in the form of fast and continuous numerical functions for intensive simulation. We provide here the methodology of this behavioral modeling as well as the details of the implementation and some numerical examples for ions in silicon target. Developed functions have been successfully tested and used for the simulation of soft errors in microelectronics circuits.


      PubDate: 2014-01-24T09:06:49Z
       
  • Volume changes in glass induced by an electron beam
    • Abstract: Publication date: 1 March 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 322
      Author(s): Tadeáš Gavenda , Ondrej Gedeon , Karel Jurek
      Three glasses (float, borosilicate float and Schott D263 glasses) were irradiated by 50keV electron beams with doses within the range of 0.21–318.5kC/m2. Volume changes induced by electron bombarding were monitored by means of Atomic Force Microscopy. Incubation doses, related to mobility of alkali ions, were measured. Low doses showed compaction of all glasses while higher doses revealed volume inflation, except for borosilicate float glass. Both surfaces of float glass were irradiated and significant differences between them were found.


      PubDate: 2014-01-24T09:06:49Z
       
  • Effects of thermal annealing on the evolution of He bubbles in zirconia
    • Abstract: Publication date: Available online 23 January 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
      Author(s): Shuyan Kong , Gihan Velisa , Aurélien Debelle , Tengfei Yang , Chenxu Wang , Lionel Thomé , Jianming Xue , Sha Yan , Yugang Wang
      Single crystals of yttria-stabilized zirconia were implanted with 100keV He ions at two fluences of 9×1016 and 3×1017 cm−2 (5 and 17 He at.%). In order to investigate the effect of thermal annealing on the evolution of both zirconia lattice and implanted He, the samples were annealed at several temperatures ranging from 500°C to 1400°C. Three complementary analysis techniques, RBS/C, AFM and TEM were used to study structural damage and surface morphology of the crystal before and after implantation. Results show different He evolution phenomena under the two implantation fluences. It is inferred that, at the lower fluence, the migration and agglomeration of He ions lead to bubble formation after annealing. These bubbles jack up sample surface causing the deformation of surface region and the damage level of surface region increase accordingly. As the temperature continues to increase, He gradually releases and the damage recovers. However, at the higher fluence, the He concentration is sufficient to induce bubble precipitation without annealing. He release and damage recovering is less efficient upon annealing.


      PubDate: 2014-01-24T09:06:49Z
       
  • Residual defects in low-dose arsenic-implanted silicon after
           high-temperature annealing
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): Akihiko Sagara , Miori Hiraiwa , Akira Uedono , Nagayasu Oshima , Ryoichi Suzuki , Satoshi Shibata
      We investigated the residual defects in low-dose (1013 cm− 2) arsenic implanted Si after high-temperature (1100°C) annealing. The presence of residual damage was successfully revealed after using a rapid thermal process for heat treatment. This damage was identified as vacancy-type defects distributed near the surface, such as tetravacancies or pentavacancies. When O2 gas was introduced to the annealing chamber, vacancy-type defects were transformed into divacancy and carbon–oxygen complex. They were confirmed to be created by a non-equilibrium reaction during the rapid cooling-down step in the annealing sequence.


      PubDate: 2014-01-20T09:06:24Z
       
  • Experimental investigation and theoretical calculation of 3He-particle
           induced nuclear reactions on cadmium up to 27MeV
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): B.M. Ali , M. Al-Abyad , U. Seddik , S.U. El-Kameesy , F. Ditrói , S. Takács , F. Tárkányi
      Excitation functions of 3He-particle induced nuclear reactions on natural cadmium were measured using the standard stacked foil technique and high resolution gamma-ray spectroscopy. From their threshold energies up to 27MeV, cross-sections for natCd(3He,xn)117m,113,111,110Sn, natCd(3He,xnp)117m,g,116m,115m,114m,113m,111,110m,g,109,108,107In, and natCd(3He,X)115g,111mCd reactions were measured. The nuclear codes TALYS, and EMPIRE-3,1 were used to describe the formation of these products. The present data were compared to theoretical results and to the available experimental data. Integral yields for some important radioisotopes were determined.


      PubDate: 2014-01-16T09:15:23Z
       
  • The effect of temperature on primary defect formation in Ni–Fe alloy
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): Chengbin Wang , Wei Zhang , Cuilan Ren , Ping Huai , Zhiyuan Zhu
      Molecular dynamics (MD) simulations have been used to study the influence of temperature on defect generation and evolution in nickel and Ni–Fe alloy (with 15%and 50% Fe content) with a 10-keV primary knock-on atom (PKA) at six different temperatures from 0 to 1500K. The recently available Ni–Fe potential is used with its repulsive part modified by Vörtler. The temporal evolution and temperature dependence of stable defect formation and in-cascade clustering processes are analysed. The number of stable defect and the interstitial clustering fraction are found to increase with temperature whereas the vacancy clustering fraction decreases with temperature. The alloy composition dependence of the stable defect number is also found for the PKA energy considered here. Additionally, a study of the temperature influence on the cluster size distribution is performed, revealing a systematic change in the cluster size distributions, with higher temperature cascades producing larger interstitial clusters.


      PubDate: 2014-01-16T09:15:23Z
       
  • Molecular dynamics simulation of displacement cascades in U–Mo
           alloys
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): Xiao-Feng Tian , Hong-Xing Xiao , Rui Tang , Chun-Hai Lu
      Molecular dynamics simulations are employed to investigate the displacement cascades in U–Mo alloys. The cascade process is analyzed in detail. The effects of initial directions of primary knock-on atom (PKA), Mo content and PKA energies on the final damage state are evaluated. The results suggest that the direction of the PKA has no effect on the final primary damage state. A high content of Mo will raise the number of defects and the probability of Mo replacement. Most of the sizes of defects cluster are no larger than three and the probabilities of producing larger interstitial and vacancy clusters are increased with higher PKA energy. The fractions of Mo interstitial in clusters with size larger than three and isolated Mo interstitials is low, while more than half the total Mo interstitials are contained in dumb-bells. Finally, it is found that the number of U–U dumb-bells is the highest and the number of Mo–Mo dumb-bells is the lowest in both alloys. The number of Mo–Mo dumb-bells seems to be independent of Mo content but the numbers of U–U and U–Mo dumb-bells decline with the increase of Mo content in alloys.


      PubDate: 2014-01-12T09:05:03Z
       
  • Electronic stopping power of hydrogen in HfO2 at the stopping maximum and
           below
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): D. Primetzhofer
      Electronic energy loss of hydrogen ions in HfO2 was investigated in a wide energy range in the medium and low energy ion scattering regime. Experiments by Time-Of-Flight Medium-Energy Ion Scattering (TOF-MEIS) with proton and deuteron projectiles were performed in backscattering geometry for nm-films of HfO2 on Si with an ultrathin SiO2 interface layer prepared by ALD. At energies around the stopping maximum excellent agreement is found with earlier results from Behar et al. (2009) [45] and theoretical predictions. Towards lower energies discrepancies between experiment and calculations increase slightly. The low energy data exhibits excellent velocity proportionality and indicates the absence of clear effects due to distinct electronic states. Thus, no apparent velocity threshold can be extrapolated from the experiments within the uncertainty of present data. The magnitude of the energy loss is discussed in terms of a free-electron model and compared with the expected electron densities from plasmon frequencies.


      PubDate: 2014-01-12T09:05:03Z
       
  • Microdosimetry spectra and RBE of 1H, 4He, 7Li and 12C nuclei in water
           studied with Geant4
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): Lucas Burigo , Igor Pshenichnov , Igor Mishustin , Marcus Bleicher
      A Geant4-based Monte Carlo model for Heavy-Ion Therapy (MCHIT) is used to study radiation fields of 1H, 4He, 7Li and 12C beams with similar ranges ( ∼ 160–180mm) in water. Microdosimetry spectra are simulated for wall-less and walled Tissue Equivalent Proportional Counters (TEPCs) placed outside or inside a phantom, as in experiments performed, respectively, at NIRS, Japan and GSI, Germany. The impact of fragmentation reactions on microdosimetry spectra is investigated for 4He, 7Li and 12C, and contributions from nuclear fragments of different charge are evaluated for various TEPC positions in the phantom. The microdosimetry spectra measured on the beam axis are well described by MCHIT, in particular, in the vicinity of the Bragg peak. However, the simulated spectra for the walled TEPC far from the beam axis are underestimated. Relative Biological Effectiveness (RBE) of the considered beams is estimated using a modified microdosimetric-kinetic model. Calculations show a similar rise of the RBE up to 2.2–2.9 close to the Bragg peak for helium, lithium and carbon beams compared to the modest values of 1–1.2 at the plateau region. Our results suggest that helium and lithium beams are also promising options for cancer therapy.


      PubDate: 2014-01-12T09:05:03Z
       
  • Editorial board
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320




      PubDate: 2014-01-12T09:05:03Z
       
  • Synthesis and controlling the optical and dielectric properties of CMC/PVA
           blend via γ-rays irradiation
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): A.M. El Sayed
      Carboxymethyl cellulose (CMC)/Polyvinyl alcohol (PVA) blend films were prepared by solution casting method. Then, these films were irradiated with γ-rays from a Co-60 source at doses over the range 0–70kGy to investigate the modifications induced in the optical and dielectric properties. The dielectric constant (ε′) was measured in the temperature range 303–408K and in the frequency range 10kHz–1MHz. The indirect optical band gap was found to increase within the dose range 0–10kGy, and to decrease at the higher doses. The refractive index values, however, showed a reversed behavior. The highest transmittance percentage was obtained at 10kGy dose. According to the frequency and temperature dependence of ε′, α- relaxation peaks were observed in all samples and assigned to the micro-Brownian motion of the blend chains. The values of ɛ′ showed a decrease in the dose range 0–10kGy and an increase in the dose range 10–70kGy. The ac conductivity σac (T) showed an Arrhenius type behavior separated into two distinct regions. The results of the present system are compared with those of similar materials.


      PubDate: 2014-01-12T09:05:03Z
       
  • Tailoring the size and distribution of Ag nanoparticles in silica glass by
           defects
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): Yitao Yang , Chonghong Zhang , Yin Song , Jie Gou , Liqing Zhang , Hengqing Zhang , Juan Liu , Yongqiang Xian , Yizhun Ma
      The composites embedded with metallic nanoparticles show large nonlinear optical susceptibility and strong surface plasmon resonance absorption, which enable potential application in opto-electronics. Ion implantation has been proven to be a powerful technique of synthesis of metallic nanoparticles due to its versatility and compatibility. However, the synthesis of nanoparticles by ion implantation inevitably leads to a broad size distribution due to Ostwald ripening process. The broad size distribution has a negative effect on improving the figure of merits for nonlinear optics. In this paper, we tried to introduce defects in silica glass to act as pre-nucleation centers to mediate the size and distribution of Ag nanoparticles. In experiment, the silica glass samples were pre-irradiated by 200keV Ar ions to fluences of 0.8, 2.0 and 5.0×1016 ions/cm2, and then 200keV Ag ions were implanted into the pre-irradiated samples to fluence of 2.0×1016 ions/cm2. UV–VIS results show that the absorbance intensity of Ag SPR peak initially increases and then decreases with pre-irradiation fluence, which implies the change in size and density of Ag nanoparticles in samples. TEM results verify that Ag nanoparticles in the sample pre-irradiated to the fluence of 0.8×1016 ions/cm2 grow bigger and distribute in a relatively narrow region comparing with that without pre-irradiation. With further increase of pre-irradiation fluence, the size of Ag nanoparticles shows a depth dependent distribution. A boundary can be clear seen at the depth of 110nm, larger Ag nanoparticles disperse in region shallower than 110nm, and smaller Ag nanoparticles disperse in the region deeper than 110nm. The average size of Ag nanoparticles initially increases and then decreases with pre-irradiation fluence. Therefore, the introduction of defects by pre-irradiation could be an effective way to tailor the size and distribution of metallic nanoparticles in matrix.


      PubDate: 2014-01-08T09:06:49Z
       
  • HEU age determination by the activity ratio 227Th/235U
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): Junjie Li , Lina Zeng , Jian Wu , Chun Zheng , Jiansheng Li
      It is important to measure the age of a highly enriched uranium (HEU) assembly for authentication of the material in the frame of arms control inspections. A new non-destructive gamma spectrometric method for HEU age-dating is reported. This method relies on measuring the daughter/parent activity ratio 227Th/235U by high-resolution gamma spectrometry. Only a narrow gamma range of energy of uranium from 230keV to 242keV will be used for analysis. The relative efficiency of every characteristic gamma ray changes in a small range because it has a near energy, which makes the results more accurate in theory. It provides a quick and reliable method for HEU age determination. Several gamma spectra of the same HEU assembly have been measured with different conditions (gain settings, distance and measurement time). When a branching ratio of 12.6% was chosen for the 235.96keV line of 227Th, we obtained the activity ratios of (5.61±0.40)×10−4, (5.17±0.39)×10−4, (5.26±0.39)×10−4, (5.10±0.35)×10−4, (5.50±0.44)×10−4 and (5.47±0.42)×10−4, respectively. These ratios correspond to ages of 52.2±2.4years, 49.7±2.3years, 50.1±2.3years, 49.3±2.2years, 51.6±2.5years and 51.5±2.4years, respectively, which are consistent with the known age of this material and the results of the U–Bi method.


      PubDate: 2014-01-08T09:06:49Z
       
  • Delta-electron spectra, inelastic cross sections, and stopping powers of
           ions in silicon: Comparison between different models
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): A. Akkerman , M. Murat , J. Barak
      The energy spectrum of the δ-electrons ejected by an ion moving in the bulk of a solid is the origin of numerous effects which follow the transport of these electrons. This spectrum cannot be measured directly. Therefore, it should be derived theoretically. The present work aims to investigate the uncertainties introduced when applying commonly used theoretical approaches like BEA, CDFT, and PWBA to calculate δ-electron spectrum. Our calculations show that, above a certain δ-electron energy, the energy spectra of the δ-electrons obtained using the various approaches behave similarly. Below this energy, the spectra found using these approaches differ significantly due to the manner in which the solid state character of the target material is taken into account in each approach. This results in differences in the inelastic cross sections and stopping powers for the ions, which in turn result in different ion track structures. Also discussed in this paper is the effect of the uncertainty in the effective ion charge on the accuracy of ion track calculations. The results obtained for silicon allow estimating the possible uncertainties of the calculated ion track properties and related effects.


      PubDate: 2014-01-04T10:28:09Z
       
  • Ion beam induced epitaxial crystallization of α-Al2O3 at room
           temperature
    • Abstract: Publication date: 15 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 321
      Author(s): Younes Sina , Manabu Ishimaru , Carl J. McHargue , Eduardo Alves , Kurt E. Sickafus
      The structure of single crystal α-Al2O3 irradiated with 175keV zirconium ions to fluences of 7.5×1015 and 1.5×1016 Zr/cm2 at room temperature, was investigated using Rutherford backscattering spectroscopy with ion channeling (RBS-C) and transmission electron microscopy (TEM). A buried amorphous layer was observed in samples irradiated at room temperature to a fluence of 1.5×1016 Zr+/cm2 (175keV). The buried amorphous region is sandwiched between two highly-damaged crystalline regions. Nano-beam electron diffraction confirmed that both the near-surface damaged layer and the deeper damaged layer remained crystalline, but the buried amorphous region is lacking in long-range atomic order. Post irradiation using 55keV oxygen ions at room temperature into pre-Zr-implanted samples produced ion beam-induced epitaxial crystallization (IBIEC) of the amorphous region adjacent to the near-surface damaged layer. Growth of the metastable polymorph γ-Al2O3 was observed at the amorphous/near surface damaged crystalline interface, as a result of this oxygen ion irradiation.


      PubDate: 2014-01-04T10:28:09Z
       
  • Intense 31–35Ar beams produced with a nanostructured CaO target at
           ISOLDE
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): J.P. Ramos , A. Gottberg , T.M. Mendonça , C. Seiffert , A.M.R. Senos , H.O.U. Fynbo , O. Tengblad , J.A. Briz , M.V. Lund , G.T. Koldste , M. Carmona-Gallardo , V. Pesudo , T. Stora
      At the ISOLDE facility at CERN, thick targets are bombarded with highly energetic pulsed protons to produce radioactive ion beams (RIBs). The isotopes produced in the bulk of the material have to diffuse out of the grain and effuse throughout the porosity of the material to a transfer line which is connected to an ionizer, from which the charged isotopes are extracted and delivered for physics experiments. Calcium oxide (CaO) powder targets have been used to produce mainly neutron deficient argon and carbon RIBs over the past decades. Such targets presented unstable yields, either decaying over time or low from the beginning of operation. These problems were suspected to come from the degradation of the target microstructure (sintering due to high temperature and/or high proton intensity). In this work, a CaO microstructural study in terms of sintering was conducted on a nanostructured CaO powder synthesized from the respective carbonate. Taking the results of this study, several changes were made at ISOLDE in terms of the CaO target production, handling and operation in order to produce and maintain the nanostructured CaO. The new target, the first nanostructured target to be operated at ISOLDE, showed improved yields of (exotic) Ar and more importantly a stable yield over the whole operation time, while operating with lower temperatures. This contradicts the ISOL paradigm of using the highest possible temperature regardless of the target’s microstructure degradation.


      PubDate: 2014-01-04T10:28:09Z
       
  • The world’s first pelletized cold neutron moderator at a neutron
           scattering facility
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): V. Ananiev , A. Belyakov , M. Bulavin , E. Kulagin , S. Kulikov , K. Mukhin , T. Petukhova , A. Sirotin , D. Shabalin , E. Shabalin , V. Shirokov , A. Verhoglyadov
      In July 10, 2012 cold neutrons were generated for the first time with the unique pelletized cold neutron moderator CM-202 at the IBR-2M reactor. This new moderator system uses small spherical beads of a solid mixture of aromatic hydrocarbons (benzene derivatives) as the moderating material. Aromatic hydrocarbons are known as the most radiation-resistant hydrogenous substances and have properties to moderate slow neutrons effectively. Since the new moderator was put into routine operation in September 2013, the IBR-2 research reactor of the Frank Laboratory of Neutron Physics has consolidated its position among the world’s leading pulsed neutron sources for investigation of matter with neutron scattering methods.


      PubDate: 2013-12-31T10:32:14Z
       
  • Low-energy electron transport in non-uniform media
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): C. Wälzlein , M. Krämer , E. Scifoni , M. Durante
      We simulated the transport of low and medium energy electrons with energies between 1.26eV and 10keV in non-uniform carbon targets using the track structure Monte Carlo code TRAX which has several applications in biophysics and radiation physics. Cross sections for electrons incident on carbon have been critically assessed. Furthermore the code has been extended to handle non-uniform targets allowing a complex geometry description. Solid state targets, which are commonly used as targets in electron spectrometers and other devices can be non-uniform, e.g. have highly irregular surfaces or pinholes. The resulting electron spectra can be significantly affected by these non-uniformities. We reproduce experimental data obtained by GSI’s Toroid electron spectrometer using thin solid state foils as targets. This unique experiment was designed to gain further insight in the emission and transport of low energy electrons in solids to improve the description of microscopic energy deposition. The realistic implementation of non-uniform targets in TRAX was verified by comparison with available experimental data. The increased backscattering due to the roughness of an unpolished target in comparison with polished ones could be reproduced as well as secondary electron spectra from the Toroid.


      PubDate: 2013-12-31T10:32:14Z
       
  • High energy (MeV) ion fluence dependent nano scale free volume defects
           studies of PMMA films
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): Paramjit Singh , Rajesh Kumar , Jincemon Cyriac , M.T. Rahul , P.M.G. Nambissan , Rajendra Prasad
      A systematic study on the dependence of the free volume at nanoscale in carbon ions irradiated polymethylmethacrylate polymer samples was carried out by means of positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy (DBS). An investigation about the evolution of cross-linking in the polymeric chains after ion irradiation was carried out from the calculated values of hole radius, free volume and fractional free volume using Tao-Eldrup Model. The role of rise in temperature on the growth of free volume was observed at higher fluences. The results were supported by variations in the S parameter of DBS study. The structural analyses were carried out using XRD to investigate for the modification in the structural nature, degree of crystallinity and average crystallite size of the polymer after ion irradiation. Additional information on the modifications of optical and chemical properties was extracted by means of UV–visible and FTIR spectroscopy respectively.


      PubDate: 2013-12-31T10:32:14Z
       
  • Prompt isothermal decay of thermoluminescence in an apatite exhibiting
           strong anomalous fading
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): I.K. Sfampa , G.S. Polymeris , N.C. Tsirliganis , V. Pagonis , G. Kitis
      Anomalous fading (AF) is one of the most serious drawbacks in thermoluminescence (TL) and optically stimulated luminescence (OSL) dating. In the present work the isothermal decay of TL signals from Durango apatite is studied for temperatures located on the rising part of the main TL peak. This material is known to exhibit strong AF phenomena, and its isothermal TL decay properties have not been studied previously. The experimental results show that the characteristic decay time of the isothermal signal does not depend of the temperature, and that this signal does not exhibit the strong temperature dependence expected from conventional TL kinetic theories. This is further direct experimental evidence for the possible presence of tunneling phenomena in this material. The isothermal decay curves are analyzed and discussed within the framework of conventional theories of TL, as well as within the context of a recently developed tunneling kinetic model for random distributions of electron-hole pairs in luminescent materials.


      PubDate: 2013-12-31T10:32:14Z
       
  • Accurate evaluation of pressure effects on the electronic stopping cross
           section and mean excitation energy of atomic hydrogen beyond the Bethe
           approximation
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): R. Cabrera-Trujillo , S.A. Cruz
      Atomic hydrogen is used as a fundamental reference target system to explore pressure effects on the electronic stopping cross section, S e , of swift bare ions such as protons and α -particles. This is achieved by considering the hydrogen atom under pressure as a padded spherically-confined quantum system. Within this scheme, S e is calculated rigorously in the first Born approximation taking into account the full target excitation spectrum and momentum transfer distribution for different confinement conditions (pressures) and fixed projectile charge states. Pressure effects on the target mean excitation energy, I, are also formally calculated and compared with corresponding accurate calculations based on the Local Plasma Approximation (LPA). Even though atomic hydrogen is the simplest target system, its accurate treatment to account for the role of pressure in the stopping dynamics is found to provide useful means to understand the behavior of more complex systems under similar conditions. It is found that: (i) the region of projectile velocities for which the Bethe approximation remains valid is shifted towards higher values as pressure increases; (ii) shell corrections are enhanced relative to the free-atom case as pressure increases, and (iii) the LPA seems to underestimate I as pressure is increased. The results of this work for atomic hydrogen may serve as accurate benchmark reference values for studies of pressure effects on S e and I using different methodologies.


      PubDate: 2013-12-31T10:32:14Z
       
  • M sub shell X-ray emission cross section measurements for Pt, Au, Hg, Pb,
           Th and U at 8 and 10keV synchrotron photons
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): Gurpreet Kaur , Sheenu Gupta , M.K. Tiwari , Raj Mittal
      M sub shell X-ray emission cross sections of Pt, Au, Hg, Pb, Th and U at 8 and 10keV photon energies have been determined with linearly polarized photon beam from Indus-2 synchrotron source. The measured cross sections have been reported for the first time and were used to check the available theoretical Dirac–Hartree–Slater (DHS) and Dirac–Fock (DF) values reported in literature and also the presently derived Non Relativistic Hartree–Slater (NRHS), DF and DHS values for Mξ, Mδ, Mα, Mβ, Mγ, Mm1 and Mm2 group of X-rays.


      PubDate: 2013-12-27T14:46:43Z
       
  • Effective source size, radial, angular and energy spread of therapeutic
           11C positron emitter beams produced by 12C fragmentation
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): Marta Lazzeroni , Anders Brahme
      The use of positron emitter light ion beams in combination with PET (Positron Emission Tomography) and PET–CT (Computed Tomography) imaging could significantly improve treatment verification and dose delivery imaging during radiation therapy. The present study is dedicated to the analysis of the beam quality in terms of the effective source size, as well as radial, angular and energy spread of the 11C ion beam produced by projectile fragmentation of a primary point monodirectional and monoenergetic 12C ion beam in a dedicated range shifter of different materials. This study was performed combining analytical methods describing the transport of particles in matter and the Monte Carlo code SHIELD-HIT+. A high brilliance and production yield of 11C fragments with a small effective source size and emittance is best achieved with a decelerator made of two media: a first liquid hydrogen section of about 20cm followed by a hydrogen rich section of variable length. The calculated intensity of the produced 11C ion beam ranges from about 5% to 8% of the primary 12C beam intensity depending on the exit energy and the acceptance of the beam transport system. The angular spread is lower than 1 degree for all the materials studied, but the brilliance of the beam is the highest with the proposed mixed decelerator.


      PubDate: 2013-12-27T14:46:43Z
       
  • Charging behavior of Al2O3 and AlN under positive and negative charge
           injection using a kV electron beam
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): M. Belhaj , T. Paulmier , R. Hanna , M. Arnaout , N. Balcon , D. Payan , J. Puech
      Under electron irradiation, insulating materials may charge either negatively or positively depending on their electron emission properties and characteristics of the incident electrons. The electrical behavior of these materials is linked to the sign of the injected charge. The aim here is to describe an electron beam based method that can be used to study the electrical behaviors of insulators under either positive or negative charge injection. The method was tested on ceramics samples, Al2O3 and AlN. It was shown that the electrical behaviors of both materials under e-irradiation are very different according the sign of the injected charge. Negative charging results to stable space charge for Al2O3 and on the contrary it leads to a fast charge-decay for AlN. Remarkably, reversed trends are observed for positive charge injection. The practical consequences of these results are then discussed.


      PubDate: 2013-12-27T14:46:43Z
       
  • Green up-conversion of swift C5+ ion irradiated planar waveguide in Er3+,
           MgO codoped nearly stoichiometric LiNbO3 crystal
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): Hongliang Liu , Yuechen Jia , Yingying Ren , Shavkat Akhmadaliev , Shengqiang Zhou , Feng Chen
      We report on the green up-conversion emission from Er3+, MgO codoped nearly stoichiometric LiNbO3 planar waveguides fabricated by the swift C5+ ion irradiation. The characteristics of the waveguides are investigated by using a continuous wave laser at wavelength of 800nm. The reconstructed distribution of the refractive index of the C ion irradiated waveguides shows a “barrier and well” profile. The up-conversion emissions of green light, corresponding to the transition of 4 H 11 / 2 → 4 I 15 / 2 and 4 S 3 / 2 → 4 I 15 / 2 bands, have been observed in the waveguides with intensity of 40% of that from the bulk.


      PubDate: 2013-12-27T14:46:43Z
       
  • Synthesis of Cu doped TiN composite films deposited by pulsed bias arc ion
           plating
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): L. Zhang , G.J. Ma , G.Q. Lin , K.C. Han , H. Ma
      The Ti–Cu–N films with different compositions were deposited by pulsed bias arc ion plating. The effect of Cu on the structure and mechanical properties of these films is investigated by means of electron probe micro-analyzer (EPMA), grazing incident X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron spectroscopy (FE-SEM) and nanoindentation, respectively. It is shown that the Ti–Cu–N film with low Cu content presents a pronounced columnar growth. The hardness enhancement in Ti–Cu–N films from 23GPa for pure TiN to maximum of 37GPa with 0.6 at.% Cu content might be correlated with the change of nanocomposite structure. Meanwhile, with further addition of Cu, the columnar structure is replaced by a dense globular structure, and the film hardness is greatly reduced due to excess soft metallic Cu. Therefore, pulsed bias arc ion plating as an effective tool can tailor the structure and mechanical properties of Ti–Cu–N composite films.


      PubDate: 2013-12-23T08:27:59Z
       
  • Charge transfer and Coulomb fragmentation in slow collisions of Xe25+ ions
           with Ar dimers
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): Bilel Zarour
      We have evaluated removal and charge transfer cross sections for Xe25+–Ar2 collisions at the impact velocity v =0.3a.u. The theoretical method includes the many-electron aspect of the problem and makes use of the classical molecular dynamics (CMD), which includes over-barrier (OB) and tunneling (TU) mechanisms. We have studied the Coulomb fragmentation of the dimer and showed the preference for asymmetric channels.


      PubDate: 2013-12-23T08:27:59Z
       
  • Investigation of deep implanted carbon and oxygen channeling profiles in
           [110] silicon, using d-NRA and SEM
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): V. Paneta , M. Erich , S. Fazinić , M. Kokkoris , I. Kopsalis , S. Petrović , T. Tadić
      Ion implantation is one of the most important techniques used in the silicon-based semiconductor industry. Using the ion axial channeling effect, which occurs when an ion beam is oriented along a crystallographic axis, it is theoretically possible to implant ions deeper in the crystal, in comparison with the ‘random’ ion beam-solid orientation, while – at the same time – minimizing the induced crystal lattice damage. In the present work, 4MeV 12C2+ and 5MeV 16O2+ ions were implanted in high-purity [110] Si crystal wafers at fluences of the order of ∼1017 particles/cm2, in both the channeling and random orientations. The resulting profiles were measured using d-NRA, i.e. implementing the 12C(d,p0) and 16O(d,p0,α0) reactions respectively, at E d,lab =1.2–1.4MeV. The results were validated using SEM (Scanning Electron Microscopy), while the extent of crystalline damage was monitored during the implantation via RBS/C (Rutherford Backscattering Spectrometry/Channeling) spectra. The resulting profiles seem to be in good agreement with those obtained in the past for fluorine and nitrogen ions implanted in silicon, and clearly demonstrate the capabilities of high-energy channeling implantations, as well as, the accuracy of d-NRA (Nuclear Reaction Analysis) profiling measurements.


      PubDate: 2013-12-23T08:27:59Z
       
  • The use of gamma irradiation in preparation of polybutadiene rubber
           nanopowder; Its effect on particle size, morphology and crosslink
           structure of the powder
    • Abstract: Publication date: 1 February 2014
      Source:Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 320
      Author(s): Majid Rezaei Abadchi , Azam Jalali-Arani
      The aim of this work was the preparation and characterization of polybutadiene rubber (BR) powder by irradiating of rubber lattices using 60Co radiation and spray-drying of them at the appropriate condition. The influences of absorbed dose on the volume swelling ratio, molecular weight between crosslinks, gel fraction, and glass transition temperature of obtained powder were studied. Morphology, size and size distribution of rubber particles were examined by using scanning electron microscopy (SEM) and laser particle size analyzer (LPSA) technique, respectively. Results obtained by LPSA revealed that radiation has no effect on particle size of rubber latex but after drying, adherence properties of rubber particle causes increase in particle size of rubber powder, as shown in SEM photograph. Fourier transform infrared spectroscopy of rubber powders confirmed that with increasing the irradiation dose, characteristic peak corresponds to the >CC< double bands decreased. Also Charlesby–Pinner equation was used to evaluate radiation yield.


      PubDate: 2013-12-23T08:27:59Z
       
 
 
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