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Heavy Ions (heavy + ion)

Distribution by Scientific Domains
Physics and Astronomy66%
Polymers and Materials Science33%

Selected Abstracts

Survey of Theoretical Work for the Proposed HEDgeHOB Experimental Schemes: HIHEX and LAPLAS

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 4-5 2007
N. A. Tahir
Abstract This paper presents a review of the theoretical work that has resulted in a scientific proposal on studies of High-Energy-Density (HED) states in matter using intense beams of energetic heavy ions that will be available at the future Facility for Antiprotons and Ion Research (FAIR) at Darmstadt [W.F. Henning, Nucl. Inst. Meth B 24 (2003) 725-729]. The proposal is named HEDgeHOB that stands for High Energy Density Matter Generated by Heavy Ion Beams. Two experimental schemes have been worked out for the HEDgeHOB experimental proposal, namely, HIHEX and LAPLAS. The first scheme allows for studies of HED states by isochoric and uniform heating of matter by an intense heavy ion beam that is followed by isentropic expansion of the heated material. Numerical simulations have shown that using the beam parameters that will be available at the FAIR, one can access all the interesting physical states of HED matter including an expanded hot liquid state, twophase liquid-gas region, critical point parameters and strongly coupled plasmas for all the materials of interest. The second scheme involves a low-entropy compression of a test material like hydrogen that is enclosed in a cylindrical shell of a high-Z material like gold or lead. The target can be driven by a hollow or a circular beam. This compression scheme relies on multiple shock reflection between the hydrogen-gold (lead) boundary and the cylinder axis. The hydrodynamic stability of the LAPLAS target has also been analyzed that shows that the implosion is completely stable to Rayleigh-Taylor and Richtmyer-Meshkov instabilities. LAPLAS implosion using a hollow beam is suitable for studying the problem of hydrogen metallization whereas the one employing a circular focal spot leads to physical conditions that are expected to exist in the interiors of the giant planets. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Aligned Gold Nanorods in Silica Made by Ion Irradiation of Core,Shell Colloidal Particles,

ADVANCED MATERIALS, Issue 3 2004
S. Roorda
Colloidal particles with a 14,nm diameter Au core surrounded by a 72,nm thick silica shell have been irradiated with 30,MeV heavy ions. The shell deforms into an oblate ellipsoid, while the core becomes rod-shaped (aspect ratio up to 9) with the major axis along the beam. Optical extinction measurements show evidence for split plasmon bands, characteristic for anisotropic metal nanoparticles. [source]

Conductive nanodots on the surface of irradiated CaF2

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2008
Tino Roll
Abstract CaF2(111) single crystal surfaces have been irradiated with fast heavy ions under oblique angles resulting in chains of nanosized hillocks. In order to characterize these nanodots with respect to their conductivity we have applied non-contact atomic force microscopy using a magnetic tip. Measurements in ultra high vacuum as well as under ambient conditions reveal a clearly enhanced electromagnetic interaction between the magnetic tip and the nanodots. The dissipated energy per cycle is comparable to the value found for metals, indicating that the interaction of the ion with the target material leads to the creation of metallic Ca nanodots on the surface. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Dependence of long-lived defect creation on excitation density in MgO single crystals

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007
Aleksandr Lushchik
Abstract The processes of the creation, stabilization and annealing of anion Frenkel defects have been investigated in MgO and MgO:Be single crystals irradiated by , particles, uranium swift ions or fast neutrons at 300 K and also additionally irradiated by 5 keV electrons at 6 K. Neutral oxygen interstitials undergo stabilization due to their association with the holes localized near Be2+ ions or near cation vacancies. The peculiarities of the processes of nonimpact creation and stabilization of point defects under conditions of a high density of electronic excitations formed in the tracks of swift heavy ions have been considered by the example of MgO crystals, where the creation energy of a pair of long-lived Frenkel defects exceeds the energy gap, EFD > Eg. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Role of structural modification on the electrical properties of poly(ethylene terephthalate) irradiated with 90-MeV carbon ion beam

POLYMER ENGINEERING & SCIENCE, Issue 6 2008
A. Srivastava
Thin films of poly(ethylene terephthalate) (PET) having a thickness of 100 ,m were exposed to different ion fluence of swift heavy ions of carbon in the range of 5 × 1011 , 5 × 1013 ions/cm2. The effect of ion beam on structural and electrical modification has been studied by UV/vis, FTIR, X-ray diffraction (XRD), Differential Scanning Calorimetery (DSC), and AC electrical measurement techniques. On irradiation, a shift in absorption wavelength toward the red end of spectrum with increase of ion fluence was observed. The intensity of crystalline IR bands and main diffraction peak in XRD pattern were found to decrease with increase in ion fluence. It indicates the loss of crystallinity induced by ion-beam irradiation. The crystallite size was found to increase on irradiation. The melting temperature (Tm) of PET films increased at a low ion dose (5.0 × 1012 ions/cm2), while it decreased at higher ion fluence (50.0 × 1012 ions/cm2). The dielectric constant (,,) of PET films was increased with increase of ion fluence. The modifications brought about in the dielectric constant are correlated with chemical and molecular structural changes occurring on irradiation. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers. [source]

Time evolution of relativistic d + Au and Au + Au collisions

ANNALEN DER PHYSIK, Issue 6 2006
G. Wolschin
Abstract The evolution of charged-particle production in collisions of heavy ions at relativistic energies is investigated as function of centrality in a nonequilibrium-statistical framework. Precise agreement with recent d + Au and Au + Au data at = 200 GeV is found in a Relativistic Diffusion Model with three sources for particle production. Only the midrapidity source comes very close to local equilibrium, whereas the analyses of the overall pseudorapidity distributions show that the systems remain far from statistical equilibrium. [source]