Search results for "RADIATION"
showing 10 items of 5298 documents
Monte Carlo simulation of micelle formation in block copolymer solutions
1998
Short block copolymers in selective solvents (bad for A-block, good for B-block) are modeled by flexible bead-spring chains, where beads interact with short range Morse potentials of variable strength. It is shown that already very short chains (N A = N B = 2) exhibit a rather well-defined critical micelle concentration (cmc). The mass distribution of the micelles and their gyration tensor components as well as their internal structure are studied. It is shown that the relaxation time increases exponentially with the strength E AA of the attractive energy between the A-monomers, and thus frozen-in micelles of medium size are obtained when E AA is chosen too large. Our results are compared t…
Compact Method for Proton Range Verification Based on Coaxial Prompt Gamma-Ray Monitoring: a Theoretical Study
2020
Range uncertainties in proton therapy hamper treatment precision. Prompt gamma-rays were suggested 16 years ago for real-time range verification, and have already shown promising results in clinical studies with collimated cameras. Simultaneously, alternative imaging concepts without collimation are investigated to reduce the footprint and price of current prototypes. In this manuscript, a compact range verification method is presented. It monitors prompt gamma-rays with a single scintillation detector positioned coaxially to the beam and behind the patient. Thanks to the solid angle effect, proton range deviations can be derived from changes in the number of gamma-rays detected per proton,…
Long-range magnetic order in the porous metal–organic framework Ni(pyrazine)[Pt(CN)4]
2017
A combined study involving DFT calculations, neutron scattering, heat capacity and magnetic measurements at very low temperatures demonstrates the long-range magnetic ordering of Ni(pyrazine)[Pt(CN)4] below 1.9 K, describing its antiferromagnetic spin arrangement. This compound belongs to the family of porous coordination polymers M(pyrazine)[Pt(CN)4] (M = divalent metal), renowned for showing interesting combinations of porosity and magnetic properties. The possibility of including long-range magnetic ordering, one of the most pursued functional properties, opens new perspectives for the multifunctionality of this class of compounds.
Study of intrinsic energy dependence of α-alanine and dose intercomparison with ESR and ISE techniques
1993
Abstract The intrinsic energy behavior of the radiation chemical yields G(R·) and G(NH3) which determine the dose response for the alanine/ESR and alanine/Ion-Selective Electrode (ISE) system, is an important characteristic for the consistent use in different radiation environments. Therefore, the response of ISS and Gent α-alanine dosimeters in the dose range 0.1 to 700 kGy was examined with 60Co, bremsstrahlung and electron beam radiation. Bremsstrahlung beams with end point energy between 5 and 12 MeV and electron beams with mean energy at the effective point of measurement between 4 and 25 MeV were used. Analysis of the 60Co calibration results shows that there are no significant differ…
Luminescence of ZnO nanopowders
2004
Abstract The luminescence of ZnO nanocrystals prepared by different methods was studied under pulsed electron beam excitation. It is shown that the luminescence intensity depends on the nanocrystal sintering conditions and does not depend on the nanocrystal size within the range 10–50 nm. The relative luminescence intensities for the 3.32 eV (free exciton) and ∼3.20 eV (bound exciton) bands showed a dependence on nanocrystal size. The role of the nanocrystal surface in excitonic luminescence is discussed.
Evaluation of the relative thermoluminescence efficiency of LiF:Mg,Ti and LiF:Mg,Cu,P TL detectors to low-energy heavy ions
2013
Abstract The most popular types of LiF-based thermoluminescent (TL) detectors, LiF:Mg,Ti (MTS-N) and LiF:Mg,Cu,P (MCP-N), have been investigated, with respect to their dose (fluence) response and relative TL efficiency to different ion species. The detectors were irradiated using the nitrogen, iron, krypton and xenon ion beams, at energies ranging from 5.0 to 9.3 MeV/n. Supra- and sublinear response was found, for the MTS-N and MCP-N, respectively, similarly as observed for γ-rays. However, the level of nonlinearity of response of studied detectors is strongly reduced by increasing values of the ion ionization density (no supralinearity for Xe ions, for MTS-N, within calculated uncertaintie…
Analysis of small-angle scattering patterns from a commercial Al-Li alloy by means of a model incorporating a repulsive step potential
1992
Abstract Small-angle X-ray scattering measurements are reported for a commercial Al-8·49%Li-51% Cu (atomic composition) alloy solution treated at 520°C and thermally aged for several times at several temperatures. Data have been analysed by means of a model of ellipsoidal precipitate particles previously proposed by some of us and by a modification of this model where, in the interparticle interference term, allowance is made for interactions between the precipitate particles at longer range than previously. This was achieved by the introduction, in addition to the hard-sphere interaction potential, of a potential step. Our fits indicate that the precipitate particles interact through a rep…
Study of collisional effects on band shapes of the ν1/2ν2 Fermi dyad in CO2 gas with stimulated Raman spectroscopy. III. Modeling of collisional narr…
1994
High resolution stimulated Raman spectra (SRS) of the ν1/2ν2 Fermi dyad of CO2 have been recorded in the 0.4–22. amagat density range at 700 K and in the 0.6–16 amagat density range at 900 K. The data have been successfully analyzed with a theoretical model taking into account both rotational line mixing through the energy corrected sudden‐polynomial (ECS‐P) law for the relaxation matrix and vibrational line broadening γv and line shifting δv. The two vibrational parameters have been accurately determined from fit to the experimental spectra. These new high temperature data together with previous data obtained at 295 and 500 K [B. Lavorel et al., J. Chem. Phys. 93, 2176 (1990); B. Lavorel e…
Objectivization of the electrical discharge measurement results taken by the acoustic emission method
2006
The subject matter of this paper refers to the improvement of the acoustic emission method (AE) in its application for diagnostics of insulation systems of power appliances whereas the detailed subject matter is connected with determining the possibilities and indicating the range of using statistical and digital methods of signal processing for the evaluation of the AE pulses generated by partial discharges (PDs), which can occur in paper-oil insulation of power transformers.
Stable and long-time operation of a soft x-ray laser for user applications experiments
2011
LASERIX is a high-power laser facility leading to High-repetition-rate XUV laser pumped by Titanium:Sapphire laser. The aim of this laser facility is to offer Soft XRLs in the 30-7 nm range and auxiliary IR beam that could also be used to produce synchronized XUV sources. This experimental configuration highly enhances the scientific opportunities of the facility, giving thus the opportunity to realize both X-ray laser experiments and more generally pump/probe experiments, mixing IR and XUV sources. In this contribution, the main results concerning both the development of XUV sources(X-Ray lasers and HHG sources) and their use for applications are presented.