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Sample records for 3c-sic crystals irradiated

  1. Irradiation Defects in Silicon Crystal

    2003-01-01

    The application of irradiation in silicon crystal is introduced.The defects caused by irradiation are reviewed and some major ways of studying defects in irradiated silicon are summarized.Furthermore the problems in the investigation of irradiated silicon are discussed as well as its properties.

  2. Optical restoration of irradiated lead fluoride crystals

    Due to its relatively high resistance to high radiation, lead fluoride (PbF2) crystals are becoming an increasingly popular material of choice for electromagnetic calorimetry, such as for experiments requiring the measurement of high-energy photons in Hall A of Jefferson Lab. For our studies we irradiated the PbF2 crystals using an electron linear accelerator (LINAC) followed by exposing the crystals to blue light so as to restore the nominal optical properties. This technique of optical bleaching with blue light affords an efficient and low-cost means for reversing the deleterious effects of optical transmission loss in radiation-damaged lead fluoride crystals. Whereas earlier experiments irradiated the PbF2 samples with 1.1 and 1.3 MeV γs from 60Co, we used pulsed beams of energetic electrons from the tunable 25-MeV LINAC at Idaho Accelerator Center of Idaho State University in Pocatello, Idaho. A 20-MeV beam of electrons was targeted onto four separate 19 cm length samples of lead fluoride over periods of 1, 2, and 4 hours yielding doses between 7 kGy and 35 kGy. Samples were then bleached with blue light of wavelength 410 - 450 nm for periods between 19.5 and 24 hours. We performed this process twice - radiation, bleaching, radiation, and then followed by bleaching again - for each of these four PbF2 samples. We shall discuss the efficacy of blue light curing on samples that have undergone two cycles of electron irradiation and optical bleaching

  3. Optical restoration of irradiated lead fluoride crystals

    Due to its relatively high resistance to high radiation, lead fluoride (PbF2) crystals are becoming an increasingly popular material of choice for electromagnetic calorimetry, such as for experiments requiring the measurement of high-energy photons in Hall A of Jefferson Lab. For our studies we irradiated the PbF2 crystals using an electron linear accelerator (LINAC) followed by exposing the crystals to blue light so as to restore the nominal optical properties. This technique of optical bleaching with blue light affords an efficient and low-cost means for reversing the deleterious effects of optical transmission loss in radiation-damaged lead fluoride crystals. Whereas earlier experiments irradiated the PbF2 samples with 1.1 and 1.3 MeV γs from 60Co, we used pulsed beams of energetic electrons from the tunable 25-MeV LINAC at Idaho Accelerator Center of Idaho State University in Pocatello, Idaho. A 20-MeV beam of electrons was targeted onto four separate 19 cm length samples of lead fluoride over periods of 1, 2, and 4 hours yielding doses between 7 kGy and 35 kGy. Samples were then bleached with blue light of wavelength 410 - 450 nm for periods between 19.5 and 24 hours. We performed this process twice - radiation, bleaching, radiation, and then followed by bleaching again - for each of these four PbF2 samples. We shall discuss the efficacy of blue light curing on samples that have undergone two cycles of electron irradiation and optical bleaching. (author)

  4. Selective crystallization of metastable phase of acetaminophen by ultrasonic irradiation

    Mori, Yoichiro; Maruyama, Mihoko; Takahashi, Yoshinori; Ikeda, Kenji; Fukukita, Suguru; Yoshikawa, Hiroshi Y.; Okada, Shino; Adachi, Hiroaki; Sugiyama, Shigeru; Takano, Kazufumi; Murakami, Satoshi; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Yoshimura, Masashi; Mori, Yusuke

    2015-06-01

    A new method for selective crystallization of the metastable phase (form II) of acetaminophen is described. To obtain form II, we prepared a highly supersaturated solution (σI = 3.7) and then applied ultrasonic irradiation at different frequencies. Without ultrasonic irradiation, spontaneous crystallization did not occur within one month in the highly supersaturated condition (σI = 3.7). When ultrasonic irradiation at 28 kHz was applied, form II preferentially crystallized. Therefore, we conclude that ultrasonic irradiation can be an effective technique for selectively crystallizing the metastable phase.

  5. Partial crystallization of silicon by high intensity laser irradiation

    Commercial single crystal silicon wafers and amorphous silicon films piled on single crystal silicon wafers were irradiated with a femtosecond pulsed laser and a nanosecond pulsed laser at irradiation intensities between 1017 W/cm2 and 109 W/cm2. In the single crystal silicon substrate, the irradiated area was changed to polycrystalline silicon and the piled silicon around the irradiated area has spindly column structures constructed of polycrystalline and amorphous silicon. In particular, in the case of the higher irradiation intensity of 1016 W/cm2, the irradiated area was oriented to the same crystal direction as the substrate. In the case of the lower irradiation intensity of 108 W/cm2, only amorphous silicon was observed around the irradiated area, even when the target was single crystal silicon. In contrast, only amorphous silicon particles were found to be piled on the amorphous silicon film, irrespective of the intensity and pulse duration. Three-dimensional thermal diffusion equation for the piled particles on the substrate was solved by using the finite difference methods. The results of our heat-flow simulation of the piled particles almost agree with the experimental results.

  6. Effect of gamma ray irradiation on sodium borate single crystals

    Kalidasan, M.; Asokan, K.; Baskar, K.; Dhanasekaran, R.

    2015-12-01

    In this work, the effects of 5 kGy, 10 kGy and 20 kGy doses of gamma ray irradiation on sodium borate, Na2[B4O5(OH)4]·(H2O)8 single crystals have been studied. Initially these crystals were grown by solution growth technique and identified as monoclinic using X-ray diffraction analysis. X-ray rocking curves confirm the formation of crystalline defects due to gamma rays in sodium borate single crystals. The electron paramagnetic resonance spectra have been recorded to identify the radicals created due to gamma ray irradiation in sodium borate single crystals. The thermoluminescence glow curves due to the defects created by gamma rays in this crystal have been observed and their kinetic parameters were calculated using Chen's peak shape method. The optical absorption increases and photoluminescence spectral intensity decreases for 5 kGy and 20 kGy doses gamma ray irradiated crystals compared to pristine and 10 kGy dose irradiated one. The effect of various doses of gamma rays on vibrational modes of the sodium borate single crystals was studied using FT-Raman and ATR-FTIR spectral analysis. The dielectric permittivity, conductance and dielectric loss versus frequency graphs of these crystals have been analyzed to know the effect of gamma ray irradiation on these parameters.

  7. Lattice Raman scattering in gamma-irradiated tryptophan crystals

    The character of change in lattice Raman spectra of aromatic aminoacid crystals-D-tryptophan - under the effect of gamma radiation has been traced. The choice of aromatic aminoacid as object for investigation is related to assumed high sensitivity of tryptophan crystal structure to the effect of short-wave irradiation due to the presence of a great number of protons in it, which interect intensively with gamma quanta. Considerable change in lattice Raman spectrum of D-tryptophan crystals under the effect of small doses of gamma irradiation has been revealed

  8. Formation of carbon crystals from polymers using electron irradiation

    Polymers consist mainly of carbon and other atoms such as hydrogen, oxygen, fluorine and etc. Because of the gas evolution during irradiation, polymer is converted into the carbon-rich materials un deer electron as well as ion irradiation. Ions have more heavy mass than electron, so it could be easy to generate the defects through the collision between ion and polymer. But electrons are not nearly affected the formation of defects due to their light mass. Thus the crystals could be formed from the electron irradiated polymer. PMMA and PE, which are degraded and cross-linked upon electron beam irradiation respectively, are irradiated by electrons of low energy and high fluence in the vacuum. In order to investigate the properties of irradiated polymers changed by electron irradiation, Raman spectrometer, nanoidentor, X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) are used. It reveals that the characteristic Raman bands of starting material are lost upon electron beam irradiation and the one-phonon bands near 1350 cm-1 (D line) and 1580 cm-1 (G line) of amorphous carbon appeared. Also the content of the sp2- and sp3 -bonded carbon which are related with electronic and mechanical properties in an amorphous carbon respectively, increases with fluence. And the surface hardness in the irradiated polymers increases as fluence increases in spite of the fact that PMMA has degrading property under irradiation especially. In the TEM observation, their diffraction patterns and high resolution lattice image show the formation of carbon crystals from polymer

  9. Folding two dimensional crystals by swift heavy ion irradiation

    Ochedowski, Oliver; Bukowska, Hanna [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Freire Soler, Victor M. [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Departament de Fisica Aplicada i Optica, Universitat de Barcelona, E08028 Barcelona (Spain); Brökers, Lara [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Ban-d' Etat, Brigitte; Lebius, Henning [CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5 (France); Schleberger, Marika, E-mail: marika.schleberger@uni-due.de [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany)

    2014-12-01

    Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS{sub 2} and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS{sub 2} does not.

  10. ESR Study on Irradiated Ascorbic Acid Single Crystal

    Food irradiation is a 'cold' process for preserving food and has been established as a safe and effective method of food processing and preservation after more than five decades of research and development. The small temperature increase, absence of residue and effectiveness of treatment of pre-packed food are the main advantages. In food industry, ascorbic acid and its derivatives are frequently used as antioxidant agents. However, irradiation is expected to produces changes in the molecules of food components and of course in the molecules of the agents added as preservation agents such as ascorbic acid. These changes in the molecular structures could cause decreases in the antioxidant actions of these agents. Therefore, the radiation resistance of these agents must be known to determine the amount of radiation dose to be delivered. Electron spin resonance (ESR) is one of the leading methods for identification of intermediates produced after irradiation. ESR spectrum of irradiated solid powder of ascorbic acid is fairly complex and determinations of involved radical species are difficult. In the present work, single crystals of ascorbic acid irradiated by gamma radiation are used to determine molecular structures of radiation induced radicalic species and four radicalic species related in pair with P21 crystal symmetry are found to be responsible from experimental ESR spectrum of gamma irradiated single crystal of ascorbic acid

  11. Melting and crystallization of LDPE containing antioxidants and irradiated

    Gel fraction (%) of LDPE containing antioxidants and irradiated by fast electron beam (200 kGy) at ambient temperature and in air decreases by 6%-30% as compared with the control specimens. DSC measurement shows that the peak melting temperature Tm, enthalpy of fusion, peak crystallization temperature Tc and enthalpy of crystallization of the irradiated LDPE are somewhat declined relative to that of unirradiated specimens. The second heating and cooling DSC run demonstrates that the Tm and Tc of all the samples studied in this work are not changed, but their enthalpies of fusion and crystallization tend to decrease. The cooling DSC reveals no influence of radiation on the blocky distribution of the branches in the LDPE used in this work. The X-ray diffraction analysis for the heat-treated samples demonstrates that irradiation does not cause appreciable change of the crystal structure and crystallite size of the samples, but the degree of the crystallinity of the irradiated samples is somewhat lower than that of unirradiated ones

  12. Charge carrier rearrangement in spinel crystals irradiated at low temperatures

    The results of an investigation of thermoluminescence (TL) in nominally pure MgAl2O4 spinel single crystals in the temperature range between 80-670 K are presented. For a heating rate of 0.21 K/s, TL spectra exhibit glow peaks in three distinct temperature ranges: 100-160, 270-370 and 470-670 K. The most prominent peaks are at 115, 140, 305, 335, 525, 570 and 605 K. The locations of the temperature maxima, as well as the intensity of the peaks, vary depending on the treatment of the crystals, the type of irradiation and the temperature of irradiation. Measurements of the glow peaks at different emission wavelengths and the use of partial bleaching and isothermal decay techniques for TL, allowed us to propose mechanisms for charge carrier rearrangement at lattice defects and impurity ions, during irradiation and subsequent heating

  13. Proton irradiation of liquid crystal based adaptive optical devices

    To assess its radiation hardness, a liquid crystal based adaptive optical element has been irradiated using a 60 MeV proton beam. The device with the functionality of an optical beam steerer was characterised before, during and after the irradiation. A systematic set of measurements on the transmission and beam deflection angles was carried out. The measurements showed that the transmission decreased only marginally and that its optical performance degraded only after a very high proton fluence (1010p/cm2). The device showed complete annealing in the functionality as a beam steerer, which leads to the conclusion that the liquid crystal technology for optical devices is not vulnerable to proton irradiation as expected in space.

  14. Electron-irradiation-induced crystallization of amorphous orthophosphates

    Amorphous LaPO4, EuPO4, GdPO4, ScPO4, and fluorapatite [Ca5(PO4)3F] were irradiated by electron beam in a TEM. Irradiations were done at -150 to 300 C, 80 to 200 keV, and current densities from 0.3 to 16 A/cm2. In all cases, the materials crystallized to form a randomly oriented polycrystalline assemblage. Crystallization is driven dominantly by inelastic processes, although ballistic collisions with target nuclei can be important above 175 keV, particularly in apatite. Using a high current density, crystallization is so fast that continuous lines of crystallites can be ''drawn'' on the amorphous matrix

  15. Positron annihilation spectroscopy of proton irradiated single crystal BCC iron

    Okuniewski, Maria A. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois, Urbana-Champaign, 103 S. Goodwin Avenue, Urbana, IL 61801 (United States)]. E-mail: okuniews@uiuc.edu; Wells, Doug P. [Department of Physics, Idaho Accelerator Center, Idaho State University, Campus Box 8263, Pocatello, ID 83209 (United States); Selim, Farida A. [Department of Physics, Idaho Accelerator Center, Idaho State University, Campus Box 8263, Pocatello, ID 83209 (United States); Maloy, Stuart A. [Los Alamos National Laboratory, MST-8, P.O. Box 1663, Los Alamos, NM 87545 (United States); James, Michael R. [Los Alamos National Laboratory, D-5, P.O. Box 1663, Los Alamos, NM 87545 (United States); Stubbins, James F. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois, Urbana-Champaign, 103 S. Goodwin Avenue, Urbana, IL 61801 (United States); Deo, Chaitanya S. [Los Alamos National Laboratory, MST-8, P.O. Box 1663, Los Alamos, NM 87545 (United States); Srivilliputhur, Srinivasan G. [Los Alamos National Laboratory, MST-8, P.O. Box 1663, Los Alamos, NM 87545 (United States); Baskes, Michael I. [Los Alamos National Laboratory, MST-8, P.O. Box 1663, Los Alamos, NM 87545 (United States)

    2006-06-01

    Positron annihilation spectroscopy was used to analyze the open-volume defects created in single crystal, body-centered cubic iron irradiated with 1.0 MeV protons. The effects of irradiation dose and temperature were investigated. A novel technique utilizing a Bremsstrahlung beam to activate and induce positron decay in the bulk specimens, followed by Doppler broadening spectroscopy, was employed. No open-volume defects were detected in the 0.03 dpa irradiated specimens. However, the 0.3 dpa specimens exhibited an increase in the S parameter when compared to the 0.03 dpa specimens at 723 K. The 0.3 dpa specimen at 723 K indicated an increase in open-volume defects, as the radiation temperature increased compared to the 573 K, 0.3 dpa specimen. This was thought to be a consequence of the void and dislocation loop density decreasing while the void and dislocation loop diameter was increasing.

  16. Positron annihilation spectroscopy of proton irradiated single crystal BCC iron

    Positron annihilation spectroscopy was used to analyze the open-volume defects created in single crystal, body-centered cubic iron irradiated with 1.0 MeV protons. The effects of irradiation dose and temperature were investigated. A novel technique utilizing a Bremsstrahlung beam to activate and induce positron decay in the bulk specimens, followed by Doppler broadening spectroscopy, was employed. No open-volume defects were detected in the 0.03 dpa irradiated specimens. However, the 0.3 dpa specimens exhibited an increase in the S parameter when compared to the 0.03 dpa specimens at 723 K. The 0.3 dpa specimen at 723 K indicated an increase in open-volume defects, as the radiation temperature increased compared to the 573 K, 0.3 dpa specimen. This was thought to be a consequence of the void and dislocation loop density decreasing while the void and dislocation loop diameter was increasing

  17. Transient compression produced in a crystal by laser irradiation

    Multikilobar transient strains were produced in single crystal silicon by laser irradiation. Variations of the lattice spacing with time and in depth were observed by pulsed x-ray diffraction. Targets were (111) silicon wafers, overcoated with 1000 A aluminum to provide a short laser absorption depth, and further overcoated with a 25 μm plastic layer. The target was irradiated with a 1 nsec pulse of 1.06 μm laser light at 0.8 - 8 J cm/sup -2/. At these low irradiances, the plastic layer is transparent; the laser light produces a low temperature aluminum plasma/vapor within the target structure. The plastic overcoat provides inertial confinement of the plasma and results in an enhancement of the pressure pulse

  18. Electron irradiation effect on single crystal of niobium

    The effect of electron irradiation (900 KeV) on gliding dislocations of single crystal Nb with its tensile axe in the [941] orientation was observed for the in-situ deformation in a high voltage electron microscope (HVEM) at Argonne National Laboratory. The experimental was carried out by the 1 hour-electron irradiation with no stress applied. Straight dislocations actuating as sinks for the electron produced defects became helicoidal as the irradiation proceeded. Frenkel pairs were created in Nb for electron energies > = 650 KeV and, as the single vacancies do not undergo long-range migration in Nb at temperatures much below 620 K, the defects that are entrapped by the dislocations are self-interstitials produced by electron displacement. Applying the stress it was possible to observe that modified dislocations did not glide while the dislocations not affected by the irradiation are visibly in movement. This important result explains the neutron and electron-irradiation induced work-hardening effect for Nb that was previously observed. (Author)

  19. Crystal-amorphous-silicon interface kinetics under ion beam irradiation

    Priolo, F.; La Ferla, A.; Spinella, C.; Rimini, E.; Campisano, S. U.; Ferla, G.

    1990-01-01

    Our recent work on ion-beam-assisted epitaxial growth of amorphous Si layers on single crystal substrates is reviewed. The crystallization was induced by a 600 keV Kr2+ beam at a dose rate of 1×1012/cm2 · s. During irradiations the samples were mounted on a resistively heated copper block whose temperature was maintained constant in the range 250-450°C. The planar motion of the crystal-amorphous interface was monitored in situ by dynamic reflectivity measurements. This technique allows the ion-induced growth rate to be measured with a very high precision. We have observed that this growth rate scales linearly with the energy deposited into elastic collisions at the crystal-amorphous interface by the impinging ions. Moreover, the rate shows an Arrhenius temperature dependence with a well defined activation energy of 0.32±0.05 eV. The dependence of this process on substrate orientation and on impurities either dissolved in the amorphous layer or present at very high concentration at the crystal-amorphous interface is also discussed.

  20. EPR study of gamma-irradiated single crystal 4-phenylsemicarbazide

    Single crystals of 4-phenylsemicarbazide (4PSC) were investigated using an electron paramagnetic resonance (EPR) technique, with γ irradiation of the crystals at different orientations in the magnetic field between temperatures of 120 and 450 K, and the spectra were found to be temperature independent. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal 4PSC, we assumed that one or more paramagnetic species were produced, each having an unpaired electron delocalized in the phenyl ring. Pursuant to this assumption, six possible radicals were modeled using the B3LYP/6-311+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radicals using the B3LYP method and TZVP basis set. The calculated hyperfine coupling constants were used as starting points for simulations. The experimental and simulated spectra for each of the three crystallographic axes were well matched for the modeled radical R6. We thus identified the R6 (C6H5NH) radical as a paramagnetic species produced in 4PSC. The experimental g-factor and hyperfine coupling constants of the C6H5NH radical were found to be anisotropic, with the average values g=2.00431, aNHN(8)=8.85G, aNHH(9)=16.85G, ao,pH(14,16,20)=6.47G, and amH(18,19)=2.80G.

  1. Light emission from the nonlinear optical crystal by FEL irradiation

    Measurements of the polarization and the local spectra of the visible light emitted from the nonlinear optical crystal BBO by the infrared FEL irradiation were performed at LEBRA. The visible lights induced by the horizontally polarized FEL consist of two components which polarized vertical and horizontal. Each component has a similar structure which consists of a large spot near the beam axis and bright arcs. The vertically and the horizontally polarized arcs faced each other up and down. The spectrum of the horizontally polarized spot has very broad peak which spreads from red to infrared region. (author)

  2. EPR studies of gamma-irradiated taurine single crystals

    Bulut, A. E-mail: abulut@samsun.omu.edu.tr; Karabulut, B.; Tapramaz, R.; Koeksal, F

    2000-04-01

    An EPR study of gamma-irradiated taurine [C{sub 2}H{sub 7}NO{sub 3}S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of {sup 32}SO{sup -}{sub 2} and {sup 33}SO{sup -}{sub 2} radicals. The hyperfine values of {sup 33}SO{sup -}{sub 2} radical were used to obtain O-S-O bond angle for both sites.

  3. EPR studies of gamma-irradiated taurine single crystals

    Bulut, A.; Karabulut, B.; Tapramaz, R.; Köksal, F.

    2000-04-01

    An EPR study of gamma-irradiated taurine [C 2H 7NO 3S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of 32ṠO -2 and 33ṠO -2 radicals. The hyperfine values of 33ṠO -2 radical were used to obtain O-S-O bond angle for both sites.

  4. EPR studies of gamma-irradiated taurine single crystals

    An EPR study of gamma-irradiated taurine [C2H7NO3S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of 32SO-2 and 33SO-2 radicals. The hyperfine values of 33SO-2 radical were used to obtain O-S-O bond angle for both sites

  5. Liquid crystal alignment on excimer laser irradiated polyimide

    Grating and photoinduced anisotropic modifications are made to polyimide layers to promote homogeneous and pretilted nematic liquid crystal alignment. Gratings are etched into the polyimide by irradiating a phase mask of period 1.1 μm with the output from a KrF excimer laser of wavelength 248 nm with fluences above the threshold required for ablation. Grating depths from 10 to 190 nm have been achieved using a simple pulse from the laser, and the liquid crystal azimuthal anchoring energy is determined as a function of the grating depth. Values up to 1.3 x 10-5 Jm-2 are found. Discrepancies are found when comparisons are made between experimental data and a theory based upon elastic strain energy minimisation. A modified theory taking finite polar anchoring into account shows better agreement. Polarised excimer laser radiation at normal incidence is used to induce an anisotropy which gives rise to homogeneous liquid crystal alignment. The strength of the azimuthal anchoring energy is similar to that produced by grating alignment. Spectroscopic analysis reveals that the alignment originates from the stronger depletion of polyimide chains parallel to the exposure polarisation direction. The dependence of beam fluence and exposure time on the anchoring energy is measured, and the degradation mechanism of the polyimide is investigated as a function of the exposure. We find that oxidative degradation takes place. We also use these techniques to identify the chemical composition of the polyimide material. Pretilted liquid crystal alignment has also been achieved, with pretilt angles up to 3.7 deg. A tilted polymer distribution is generated by oblique exposure of the polyimide to an elliptically polarised beam. We measure the liquid crystal pretilt angle as a function of the angle of incidence, and exposure time and present a theoretical analysis of the polyimide chain azimuthal distribution which agrees with the experimental results. Finally, a simple and novel technique

  6. Comprehensive studies on irradiated single-crystal diamond sensors

    Stegler, Martin [DESY, Zeuthen (Germany)

    2015-07-01

    Single-crystal diamond sensors are used as part of the Beam and Radiation Instrumentation and Luminosity (BRIL) projects of the CMS experiment. Due to an upgrade of the Fast Beam Conditions Monitor (BCM1F) these diamond sensors are exchanged and the irradiated ones are now used for comprehensive studies. Current over voltage (IV), current over time (CT) and charge collection efficiency (CCE) measurements were performed for a better understanding of the radiation damage incurred during operation and to compensate in the future. The effect of illumination with various light sources on the charge collection efficiency was investigated and led to interesting results. Intensity and wavelength of the light were varied for deeper insight of polarization effects.

  7. Study of KTP crystal properties under continuous and pulsed irradiation

    Variation of the optical density at λ = 0.53 and 1.06 μm and of the conversion efficiency in the second harmonic of the AYG: Nd+3 laser 1.06 μm radiation for the KTP crystal elements under the action of continuous gamma (up to the dose of 7.6 x 106 rad) and pulse gamma-neutron (up to the flux of 1.4 x 1015 neutron/cm-2) radiations is investigated. The maximum radiation-induced absorption is 8 x 10-2 cm-1 at λ 0.53 μm and 4 x 10-2 cm-1 at λ = 1.06 μm. The conversion efficiency decreases from 60 to 50% under the action of gamma radiation and to 55% under neutron irradiation

  8. Optical studies of X-irradiated sodium bromide single crystals

    Optical absorption of sodium bromide single crystals colored by X-rays for durations ranging from 8 hours to 200 hours at room temperature has been studied. Two well-resolved absorption bands one at 535 nm (F-band) and the other at 255 nm have been observed in all the samples. Another band at 840 nm (M-band) has also been observed when the irradiation time was extended to 200 hours. A band at 770 nm has been detected for the first time during the process of optical bleaching. The effects of optical bleaching with F-band light on these absorption bands have been studied in detail for durations ranging from a few seconds to 1820 minutes at temperature below the coloration temperature. (author)

  9. Effect of gamma-irradiation defects on ferroelectric phase transitions of TGSe and DTGSs crystals

    Song, Y W

    1999-01-01

    The influence of gamma-irradiation defects upon the second-order phase transition in TGSe and the first-order phase transition in DTGSe crystals was studied by means of specific-heat measurements. gamma-irradiation defects changed the behavior of the thermodynamic properties, and the order of the phase transition was changed from the first to the second in the DTGSe crystal. The kinetics of gamma-irradiation defects was studied.

  10. Effect of SR irradiation on crystallization of amorphous tin oxide film

    Kimura, Y; Hanamoto, K; Sasaki, M; Kimura, S; Nakada, Tatsuya; Nakayama, Y; Kaito, C

    2001-01-01

    In order to see the effect of SR irradiation on crystal growth, crystallization of tin oxide films has been performed in vacuum under SR irradiation. A thin amorphous tin oxide film 50 nm thick was prepared on the carbon substrate by vacuum evaporation of SnO sub 2 power. A SnO crystal appeared between 450-500 deg. C upon vacuum heating, with a preferred orientation of (0 0 1). By SR irradiation using a cylindrical mirror for 20 s, the SnO crystal appeared with the preferred orientation of (1 1 1). The crystal with the crystallographic shear structure was grown by SR irradiation. This growth under a SR beam is discussed in terms of SR beam excitation of lone-pair electrons seen in the SnO crystal structure.

  11. Gamma irradiation effect on optical and dielectric properties of potassium dihydrogen phosphate crystals

    Guo, Decheng; Zu, Xiaotao; Yang, Guixia; Huang, Jin; Wang, Fengrui; Liu, Hongjie; Xiang, Xia; Jiang, Xiaodong

    2016-04-01

    The effect of Co60 gamma-ray irradiation on potassium dihydrogen phosphate crystals is investigated at doses ranging from 1 kGy to 100 kGy with different diagnostics, including UV-Vis absorption spectroscopy, fluorescence spectroscopy, DC electrical conductivity, positron annihilation lifetime spectroscopy and Doppler-broadening spectroscopy. The optical absorption spectra show a wide absorption band between 250 and 400 nm after γ-irradiation and its intensity increases with the increasing irradiation dose. The simulation of radiation defects show that this absorption is assigned to the formation of substitutional impurity defects due to Al, Mg ions substituting for K ions. The fluorescence peak at 355 nm blue shifts after irradiation. The fluorescence intensity is observed to increase with the increasing irradiation dose. The positron annihilation lifetime spectroscopy is used to probe the evolution of vacancy-type defects in potassium dihydrogen phosphate crystal. The variation of size and concentration of vacancy-type defects with the different irradiation dose is investigated. The Doppler-broadening spectroscopy gives direct evidence of the formation of irradiation-induced defects. The dc electrical conductivity of γ-irradiated potassium dihydrogen phosphate crystals increases with the increasing irradiation dose when the dose is less than 10 kGy, whereas keeps constant at high irradiation dose of 100 kGy. The increase of electrical conductivity is associated with the increase of the proton defect concentration in the crystal. A possible explanation about the change of proton defect concentration with irradiation dose is presented.

  12. Piezoelectric resonance calorimetry of nonlinear-optical crystals under laser irradiation

    Ryabushkin, Oleg A.; Konyashkin, Aleksey V.; Myasnikov, Daniil V.; Tyrtyshnyy, Valentin A.; Vershinin, Oleg I.

    2013-09-01

    Novel method is proposed for determination of nonlinear-optical crystal both heat transfer and optical absorption coefficients by measuring kinetics of the laser-irradiated crystal temperature-dependent piezoelectric resonance frequency. When laser radiation propagates through the crystal its temperature evaluation with time is directly determined from crystal piezoelectric resonance frequency shift, which is precisely measured by analyzing crystal response to the applied ac electric voltage. Heat transfer and optical absorption coefficients are obtained using measured characteristic time of crystal laser heating kinetics by solving nonstationary heat conduction equation. Experiments were performed with nonlinear-optical α-quartz, lithium triborate (LBO) and periodically poled lithium niobate (PPLN) crystals.

  13. Effect of 120 MeV Ag{sup 9+} ion irradiation of YCOB single crystals

    Arun Kumar, R., E-mail: rarunpsgtech@yahoo.com [Crystal Growth Centre, Anna University, Chennai 600 025 (India); Department of Basic Sciences - Physics Division, PSG College of Technology, Coimbatore 641 004 (India); Dhanasekaran, R. [Crystal Growth Centre, Anna University, Chennai 600 025 (India)

    2012-09-15

    Single crystals of yttrium calcium oxy borate (YCOB) grown from boron-tri-oxide flux were subjected to swift heavy ion irradiation using silver Ag{sup 9+} ions from the 15 UD Pelletron facility at Inter University Accelerator Center, New Delhi. The crystals were irradiated at 1 Multiplication-Sign 10{sup 13}, 5 Multiplication-Sign 10{sup 13} and 1 Multiplication-Sign 10{sup 14} ions/cm{sup 2} fluences at room temperature and with 5 Multiplication-Sign 10{sup 13} ions/cm{sup 2} fluence at liquid nitrogen temperature. The pristine and the irradiated samples were characterized by glancing angle X-ray diffraction, UV-Vis-NIR and photoluminescence studies. From the characterization studies performed on the samples, it is inferred that the crystals irradiated at liquid nitrogen temperature had fewer defects compared to the crystals irradiated at room temperature and the defects increased when the ion fluence was increased at room temperature.

  14. Atomic force microscopy characterization of a YBaCuO crystal surface patterned by proton irradiation

    A YBaCuO single crystal and a c-axis grown epitaxial YBaCuO film were irradiated with 200 keV protons to study the changes of the transport and especially of the structural properties. The single crystal was covered with a special grid-mask with strips of 5 μm periodicity in the irradiation procedure. The changes of the structural properties of the film and of the single crystal were studied by X-ray diffraction and by interference contrast and atomic force microscopy, respectively. The main structural effect of irradiation with moderate fluences is a lattice expansion of 0.8% in the film. The expansion of the irradiated parts of the crystal was 15-20 nm which is a factor of about 2 higher than in the film. This discrepancy can be resolved by considering the different energy deposition processes in the crystal and in the film. (orig.)

  15. High resolution X-ray diffraction studies on unirradiated and irradiated strontium hexaferrite crystals

    Balwinder Kaur; Monita Bhat; F Licci; Ravi Kumar; K K Bamzai; P N Kotru

    2012-04-01

    High-resolution X-ray diffraction technique, employing a three-crystal monochromator–collimator combination is used to study the irradiation induced defects in flux grown Sr-hexaferrite crystals irradiated with 50 MeV Li3+ ion beams at room temperature with a fluence value of 1 × 1014 ions/cm2. The diffraction curves of the irradiated crystals suggest the possibility of creation of low angle grain boundaries and other point/clusters of defects causing amorphization in the irradiated crystals. The perfection of the irradiated and unirradiated (0001) cleaved surfaces of the crystals is studied using the bulk method of X-ray topography. The topographs supplement the findings suggestive of modifications in the crystalline quality of SrFe12O19 on irradiation with SHI of Li3+. Etching of the (0001) cleaved surfaces in H3PO4 at 120°C suggests that the dissolution characteristics of the surfaces get affected on irradiation with SHI of Li3+, besides supporting the findings of HRXRD and X-ray topography regarding modifications in the perfection of SrFe12O19 on irradiation.

  16. Radiation effects in LiB3O5 nonlinear crystals under eletron beam irradiation

    Investigation results on defect accumulation in LiB3O5 crystals under electron beam irradiation are presented. A conclusion has been made about the role of radiation-induced defects in the accumulation of electric charges in LBO crystals under destructive electron irradiation due to electric breakdown. The processes considered can simulate defect formation in a crystaltransformer based on LBO affected by powerful laser pulses

  17. New effect of ionizing irradiation: anisotropic expansion of a peptide crystal

    Kuroda, S.; Kurita, Y.; Miyagawa, I.

    1985-10-01

    Expansion of crystals resulting from X irradiation was studied in the case of a peptide, N-acetyl-D, L-alanine. This expansion was discovered by examining several irradiated organic solids for possible expansion, which was suggested by the recent observation of crystal imperfections in another peptide. The expansion, which occurred anisotropically along the c axis, was found to depend on dose, the maximum being as large as 20% when assisted by heat treatment.

  18. Defect formation in spinel crystals under electron and gamma beam irradiation

    There were investigated the optical absorption centers formation in magnesium aluminate spinel crystals at the action of high energy gamma or electron beams. It was revealed that at gamma irradiation the most probably the hole centers are formed to compare with that in electron irradiation. At electron beam irradiation the temperature of sample was raised which leads to thermal annealing of unstable radiation-induced centers

  19. Ferromagnetism in proton irradiated 4H-SiC single crystal

    Ren-Wei Zhou

    2015-04-01

    Full Text Available Room-temperature ferromagnetism is observed in proton irradiated 4H-SiC single crystal. An initial increase in proton dose leads to pronounced ferromagnetism, accompanying with obvious increase in vacancy concentration. Further increase in irradiation dose lowers the saturation magnetization with the decrease in total vacancy defects due to the defects recombination. It is found that divacancies are the mainly defects in proton irradiated 4H-SiC and responsible for the observed ferromagnetism.

  20. Ferromagnetism in proton irradiated 4H-SiC single crystal

    Room-temperature ferromagnetism is observed in proton irradiated 4H-SiC single crystal. An initial increase in proton dose leads to pronounced ferromagnetism, accompanying with obvious increase in vacancy concentration. Further increase in irradiation dose lowers the saturation magnetization with the decrease in total vacancy defects due to the defects recombination. It is found that divacancies are the mainly defects in proton irradiated 4H-SiC and responsible for the observed ferromagnetism

  1. Bleaching of potassium dihydrophosphate crystals at large γ-irradiation doses

    The influence of gamma-irradiation on optical absorption spectra and EPR spectra of KH2PO4 single crystals at room temperature is studied. It is shown that the decrease in optical transparency of crystals after irradiation is associated with the formation of the AsO44- and AsO32- impurity radiation defects. The increase in optical transparency associated with the destruction of the AsO44- and AsO32- radicals by gamma rays at high doses of irradiation is observed

  2. Inhomogeneous strain induced by fast neutron irradiation in NaKSO4 crystals

    The effect of fast neutron irradiation on the thermal properties of NaKSO4 crystals was studied around the phase transition temperature Tc=453 K. The thermal expansion coefficient as well as the phase transition temperature were found to be dependent upon the irradiation dose. The specific heat, Cp, showed multiple peaks in the phase transition temperature region. An explanation of this behaviour was based on the induced inhomogeneous strain in the crystal casued by the neutron irradiation process. (author). 10 refs, 3 figs

  3. Ageing effect on the thermoluminescence of X-irradiated yttrium doped KBr crystals

    Thermoluminescence glow curves were recorded on X-irradiated KBr:Y crystals in as grown, aged and quenched conditions. Two glow peaks around 85 and 110 C were observed in as grown crystals. A marked difference in the glow curve patterns have been observed for aged and quenched crystals. These observations are explained on the basis of the state of dispersion of yttrium impurity in KBr lattice. ((orig.))

  4. Low-temperature crystallization of amorphous silicon and amorphous germanium by soft X-ray irradiation

    The low-temperature-crystallization effects of soft X-ray irradiation on the structural properties of amorphous Si and amorphous Ge films were investigated. From the differences in crystallization between Si and Ge, it was found that the effects of soft X-ray irradiation on the crystallization strongly depended on the energy band gap and energy level. The crystallization temperatures of the amorphous Si and amorphous Ge films decreased from 953 K to 853 K and 773 K to 663 K, respectively. The decrease in crystallization temperature was also related to atoms transitioning into a quasi-nucleic phase in the films. The ratio of electron excitation and migration effects to thermal effects was controlled using the storage-ring current (photon flux density). Therefore, we believe that low-temperature crystallization can be realized by controlling atomic migration through electron excitation. - Highlights: • This work investigates the crystallization mechanism for soft X-ray irradiation. • The soft X-ray crystallization depended on the energy band gap and energy level. • The decrease in the crystallization temperature for Si and Ge films was 100 K. • This decrement was related to atoms transitioning into a quasi-nucleic phase

  5. Statistical description of response to flood-field irradiation in scintillation crystal arrays

    Images obtained by flood-field Co57 irradiation of CsI(Tl) crystal arrays detectors, coupled to a metal-channel dynode PSPMT, were statistically analyzed by means of a bivariate normal distribution. For each crystal position, the planar distribution charge was described by a confidence ellipse chosen to maximize the 1-to-1 relationship between the photons incoming at each crystal and the centroid obtained from electric charge distribution. The flood-field irradiation response of a 22 mmx22 mm CsI(Tl) array, with different pixel dimensions, were studied, and the comparison between the charge distribution of a limited number of crystals following the flood-field irradiation was made

  6. Particle irradiation and electron work function: Fe single crystal bombarded with Ar+ ions

    Horváth, Ákos; Nagy, Norbert; Schiller, Robert

    2016-07-01

    Accelerated Ar+ ions of 30 keV energy were used to mimic the effect of fast neutrons on Fe single crystal. Both Monte-Carlo calculations and X-ray Photoelectron Spectroscopy (XPS) measurements indicated that the fast ions did not alter the surface causing damage only at several nm depth. The change in the electrode potential, characteristic also to corrosion processes, was determined by the Kelvin method of work function measurement in order to avoid any post-irradiation process. Irradiation with fluences between 5×1014 and 6×1015 cm-2 decreased the electrode potential of the sample by about 60 mV in qualitative agreement with earlier results about the work functions of Fe single crystal and polycrystalline sample. Thus ion irradiation turns the interior of the single crystal into a disordered, polycrystalline substance increasing the crystal's readiness to be corroded.

  7. Irradiation effect on the annealing of impurity hardening regularities of crystals NaCl

    Crystals, which contain of different types of impurities Ca2+ - hole-acceptor impurity, highly soluble NaCl, and Pb2+ - electron-acceptor one, low soluble in NaCl, were investigated. Softening caused by soft X-ray irradiation before the annealing of doped crystals was found for the first time. Microhardness of the irradiated alloyed crystals becomes lower, than the value, which corresponds to the unannealed unirradiated sample. This effect is manifested more clearly in NaCl:Pb. Opinion is expressed, that softening effect is connected with decomposition of impurity complexes. This assumption is proved by the investigation results of annealing regulations for dislocation structures near the indenter prints. It is shown, that these regularities depend on impurity type: processes of dislocation polygenization are observed on NaCl:Ca crystals, while on NaCl:Pb crystals dislocation distribution is of the chaotic character. Preliminary irradiation of NaCl:Pb crystals results in dislocation arrangement, in polygonization occurrence. It seems, tha X-ray irradiation, while decomposing the impurity complexes in NaCl:Pb crystals, approximates their impurity state to that of NaCl:Ca

  8. Isothermal Crystallization Kinetics of HDPE/HA Compounds Irradiated with Sterilization Doses of Gamma Rays

    The objective of this work was to study the isothermal crystallization of High Density Polyethylene/Hydroxyapatite nanocomposites, with 2 and 5 ppc of HA, irradiated with 25 kGy (sterilization dose) of γ-Ray from a 60Co source, at a rate of 4.8 kGy/h in air and at room temperature. The selected crystallization temperatures were 118, 117, 116 and 115 degree. The crystallization kinetics was analyzed using the Avrami's model whose parameters were optimized using a non-linear regression technique. Regression results show that the Avrami exponent varies between 1.8 and 1.5, meaning that the spherulitic growth is mainly two dimensional. Values for specific crystallization constant 'k' were found to be higher for HDPE/HA compounds than for pure HDPE, clearly indicating the presence of an HA nucleation effect. It was also observed that values for the specific crystallization constant 'k' decreases with increasing temperatures, being this effect more noticeable for HDPE/HA compounds than for pure HDPE. Regarding to irradiated samples, their 'k' values were found to be lower than those for non irradiated samples, the difference getting more significant with decreasing crystallization temperature. Simulation of experimental data with the Avrami's model show a clear influence of the crystallization temperature, the HA content in the sample and the amount of applied radiation. It was also observed that the Avrami model correlates satisfactorily experimental data for not irradiated samples of pure HDPE and HDPE/HA compounds at the highest crystallization (Tc). However, as the crystallization temperature decreases, the values simulated with the Avrami model increasingly deviate from experimental data, specifically at the highest values of the relative crystallinity. This effect is even stronger on irradiated samples of HDPE and HDPE/HA compounds

  9. Influence of electron irradiation upon the properties of MgAl2O4 crystals

    Nominally pure crystals MgOxAl2O3 and MgOx2Al2O3 have been studied. The crystals have been irradiated by an 12 MeV electron beam with the integrated flux of 3x1015 electron/cm-2. Measurements have been taken of optical absorption spectra and of curves of thermoluminescence of magnesium-aluminium spinel crystals. A crystallographic analysis has shown that in the spinel structure, oxygen ions form an almost perfect close-packed cubic lattice, with Mg and Al ions are in tetraedric (A) and octaedric (B) vacancies formed. On irradiation, free electrons and holes are formed which transform into optically active centers. Absorption spectra of the irradiated crystals of 2Al2O3 are presented. When the samples are annealed, the colour centers are destroyed, with a subsequent thermoluminescence (TL). A conclusion may be drawn that irradiation of Mg-Al spinel crystals by 12 MeV electrons leads to intense formation of colour centers with absorption band maxima at 270, 360, 390, 470 and 580 nm. On the TL curves, maxima were observed at 390, 430, 450, 470 and 500 K. A comparison of the absorption bands and TL maxima with the previously observed absorption and TL spectra allows to identify V and F centers, as well as charge exchange of impurity ions during irradiation

  10. Electron-irradiation influence on luminescence anisotropy of GaSe crystals

    Full text : In GaSe crystals with layered structure it has been studied the influence of 4,5 MeV energetic fast electron excitation on luminescence irradiation. In order to carry out polarization with Bridgman method, the grown GaSe crystals were radiated under the influence of electric field, which was applied along the optical axis C, parallel to layers and the irradiation is associated with electron recombination, injected from the contact. Intensity of the emission lines, so the polarization factor of the irradiation are subject to change within the excitation of crystals with fast electrons. It has been shown that, under the influence of electrons, the luminescence intensity and spectral distribution energy of 4,5 Mev are exposed to a non-monotonous change depending on the irradiation dose. After the electron impact within 3,5 min, the intensity of crystals luminescence lines corresponding to impurities increases. In this case, as recombination levels, which occur under the influence of electrons, increase both the intensities and the anisotropy factor gets reduced. At the absorption edge the intensity of the radiation lines and therefore, factor remain unchanged. At high doses (within 60 min. irradiation) luminescence decreases according to impurities, and though the intensity of shortwave radiation line slightly changes, its anisotropy degree increases, dichroism appears in the composition of photopleochroism factor of doped crystals

  11. AFM studies of swift heavy ion and electron irradiated mixed barium strontium borate nonlinear optical crystal

    Single crystals of novel nonlinear optical material of mixed barium strontium borate is grown in our laboratory by employing the low-temperature solution technique. Equal proportion (1:1 molar ratio) of AR grade barium borate and strontium borate are mixed together in double distilled water to prepare a supersaturated solution. The solution is allowed to evaporate at constant temperature (30 deg. C) in a Petri dish for about a week which resulted in the formation of seed crystals. These seed crystals are used to grow larger crystals by suspending them using fine silk thread in the supersaturated mother solution. The solution is allowed to evaporate at constant temperature. This resulted in the growth of good transparent crystals of dimension 15 mmx10 mmx1 mm after about one month. These crystals show good second harmonic generation (SHG) efficiency. The mixed barium strontium borate crystal is found to be a promising nonlinear optical crystal, which possibly can be used for fabrication of photonic devices. The single crystals of mixed barium strontium borate are irradiated by 120 MeV Ag+13 swift heavy ions (SHI) of fluence 5x1011 ions/cm2 at Nuclear Science Centre, New Delhi and also by electrons of 8 MeV energy with a fluence 5.7x109/cm2 using Microtron accelerator at Mangalore University. Surface morphology studies of these crystals are carried out using atomic force microscope. The AFM topographical images of these SHI/electron irradiated single crystals of mixed barium strontium borate are obtained from different frames of the sample taken at different magnifications using atomic force microscope. An attempt is made to explain the surface damage caused due to SHI/electron irradiation using the observed AFM images

  12. Metallic Na formation in NaCl crystals with irradiation of electron or vacuum ultraviolet photon

    Owaki, Shigehiro [Osaka Prefecture Univ., Sakai, Osaka (Japan). Coll. of Integrated Arts and Sciences; Koyama, Shigeko; Takahashi, Masao; Kamada, Masao; Suzuki, Ryouichi

    1997-03-01

    Metallic Na was formed in NaCl single crystals with irradiation of a variety of radiation sources and analyzed the physical states with several methods. In the case of irradiation of 21 MeV electron pulses to the crystal blocks, the optical absorption and lifetime measurement of positron annihilation indicated appearance of Na clusters inside. Radiation effects of electron beam of 30 keV to the crystals in vacuum showed the appearance of not only metallic Na but atomic one during irradiation with Auger electron spectroscopy. Intense photon fluxes in vacuum ultraviolet region of synchrotron radiation were used as another source and an analyzing method of ultraviolet photoelectron spectroscopy. The results showed the metallic Na layered so thick that bulk plasmon can exist. (author)

  13. Coloration of cadmium halide crystals due to reactor irradiation at low temperature

    The optical absorption spectra and ESR spectra of cadmium halide crystals were measured after the reactor irradiation at low temperature to study the coloration. The irradiated neutron dose was about 5 x 1017 n/cm2. In the measurement of ESR spectra, the crystal was rotated around the v-axis (the two-fold axis) in the magnetic field of fixed direction. The optical absorption spectra showed that the Cd3+ center was generated. From the analysis of the angular dependence of ESR spectra, the centers of C(2h) symmetry and the centers of D(3d) symmetry were considered to be generated. The models of these centers were considered, and the angular dependence was analyzed. It can be concluded from the present experiment that the coloration of cadmium halide crystals is recognized as the results of the reactor irradiation at low temperature. (Kato, T.)

  14. Thermoluminescence of CsI:Sr++ crystals irradiated with X-rays

    Thermoluminescence and optical absorption studies have been made in pure and Sr++ doped CsI crystals irradiated with X-rays. In undoped cesium iodide there are glow peaks at 363 and 401oK for 5 minutes of X-ray irradiation. These two glow peaks are attributed to thermal decay of F-centre. Three glow peaks at 348 K, 386 K and 396 K have been observed in CsI:Sr++ crystals for 5 minutes of irradiation. The glow peaks at 348 K and 396 K for CsI:Sr++ crystals could be attributed to thermal decay of F-centres. The F-centre glow peaks of doped samples exhibit a shift towards the lower temperature side. The glow peak at 386 K is attributed to thermal decay of Z1 centres. (author). 4 refs., 2 figs

  15. Investigation of swift heavy ion irradiation effects in CdTe crystals

    CdTe crystals grown by the Bridgman technique were irradiated by swift heavy ions (SHIs), 100 MeV Ag7+ ions, with fluences varying from 1011 to 1014 ions cm-2 and the damage is investigated by atomic force microscopy, x-ray diffraction, hall effect measurements and photoluminence. It is found that the behaviour of CdTe crystals under a SHI irradiation induces structural disorder, generation of optically active defects, decrease in the electron mobility but an increase in the carrier concentration compared with as-grown samples. The observed effects are mainly due to the intense electronic excitation created by SHIs

  16. Characterisation of irradiation-induced defects in ZnO single crystals

    Prochazka, I.; Cizek, J.; Lukac, F.; Melikhova, O.; Valenta, J.; Havranek, V.; Anwand, W.; Skuratov, V. A.; Strukova, T. S.

    2016-01-01

    Positron annihilation spectroscopy (PAS) combined with optical methods was employed for characterisation of defects in the hydrothermally grown ZnO single crystals irradiated by 167 MeV Xe26+ ions to fluences ranged from 3×1012 to 1×1014 cm-2. The positron lifetime (LT), Doppler broadening as well as slow-positron implantation spectroscopy (SPIS) techniques were involved. The ab-initio theoretical calculations were utilised for interpretation of LT results. The optical transmission and photoluminescence measurements were conducted, too. The virgin ZnO crystal exhibited a single component LT spectrum with a lifetime of 182 ps which is attributed to saturated positron trapping in Zn vacancies associated with hydrogen atoms unintentionally introduced into the crystal during the crystal growth. The Xe ion irradiated ZnO crystals have shown an additional component with a longer lifetime of ≈ 360 ps which comes from irradiation-induced larger defects equivalent in size to clusters of ≈10 to 12 vacancies. The concentrations of these clusters were estimated on the basis of combined LT and SPIS data. The PAS data were correlated with irradiation induced changes seen in the optical spectroscopy experiments.

  17. Study on irradiation damage of Bi-doped PbWO4 crystal

    The luminescence and point defects of pure lead tungstate crystals (PbWO4) and Bismuth (Bi) doping crystal (PbWO4:Bi) grown by modified Bridgman method are studied. It is found that irradiation results in the great change of the transmission and X-ray excited emission after γ-ray irradiation about 4 Mrad dose. The defects in PbWO4 crystal have been studied by means of positron annihilation lifetime and X-ray photoelectron spectra. The results show that Bi dopant suppresses the concentrations of positron capture centers and low-valent oxygen ions. After γ-ray irradiation, in the pure crystal the concentration of lead vacancy (VPb) is decreased and that of low-valent oxygen increased; on the contrary, in Bi dopant crystal the concentrations of positron capture centers increased and that of low-valent oxygen ions suppressed. It is tentatively proposed that Bi3+ dopants would mainly occupy the site of lead vacancies resulted from Pb volatilization. And irradiation changes the chemical valence of Bi element, which is Bi3+→Bi5+. the Bi5+ will replace the lattice W6+ ions and it will cause some (WO4)2- replaced by (BiO3 + Vo)-

  18. Electron-irradiation-induced crystallization at metallic amorphous/silicon oxide interfaces caused by electronic excitation

    Nagase, Takeshi; Yamashita, Ryo; Lee, Jung-Goo

    2016-04-01

    Irradiation-induced crystallization of an amorphous phase was stimulated at a Pd-Si amorphous/silicon oxide (a(Pd-Si)/SiOx) interface at 298 K by electron irradiation at acceleration voltages ranging between 25 kV and 200 kV. Under irradiation, a Pd-Si amorphous phase was initially formed at the crystalline face-centered cubic palladium/silicon oxide (Pd/SiOx) interface, followed by the formation of a Pd2Si intermetallic compound through irradiation-induced crystallization. The irradiation-induced crystallization can be considered to be stimulated not by defect introduction through the electron knock-on effects and electron-beam heating, but by the electronic excitation mechanism. The observed irradiation-induced structural change at the a(Pd-Si)/SiOx and Pd/SiOx interfaces indicates multiple structural modifications at the metal/silicon oxide interfaces through electronic excitation induced by the electron-beam processes.

  19. Irradiation effects in CaF2: ZnO nanostructed crystals

    Effects of β, X, and UV radiation were studied in CaF2: ZnO single crystals in which ZnO was embedded as nanoparticles. Absorption measurements of these crystals showed a steep increase below 250nm and a weak absorption peak at about 310nm. After prolonged β irradiation, additional absorption bands were recorded at 395 and 595nm. The irradiated samples showed during heating several thermoluminescence (TL) peaks. Samples which had been exposed to β-irradiation at RT and subsequently illuminated at LNT with 390nm light showed during re-heating to RT several TL peaks that are attributed to a process of photo-transferred TL (PTTL). Main photoluminescence (PL) emission bands were recorded at 320 and 340nm with excitation maxima near 250 and 300nm. These emission bands were also observed during X-irradiation as well as additional emission bands near 355 and 400nm. In pre-irradiated samples, a 320nm luminescence band could also be excited by 395nm light and is attributed to a process of photostimulation. The stimulation maxima of the OSL and PTTL in the 390nm region are apparently due to the observed absorption band at 395nm induced by the β-irradiation. The fact that some of the same emission bands appeared in the XL, PL, TL and OSL of this crystal indicates that the same luminescence centers are involved in these emissions.

  20. D-D neutron irradiation effects on single-crystal TiO2

    Rutile single-crystal TiO2 were irradiated by 2.5 MeV neutrons from D-D reaction on a neutron generator at Lanzhou University. Positron annihilation lifetime spectra and X-ray diffraction (XRD) patterns of the irradiated samples were compared with those of the virgin. Considering the fact that the threshold displacement energy of titanium atoms is almost two times of that of oxygen atoms, more oxygen vacancies (VO) would be produced than that of titanium vacancies (VTi) under the neutron irradiation. Lifetime results indicated that the irradiated samples had larger electron density of titanium vacancies than the virgin rutile, as a result of increased oxygen vacancies surrounding the Ti vacancy, because of the coulombic repulsion. From the XRD results, distance along the c-axis shrank slightly and the crystallinity became weaker after the neutron irradiation. (authors)

  1. Modification of mechanical properties of Si crystal irradiated by Kr-beam

    Graphical abstract: - Highlights: • Modification of mechanical properties of silicon crystal irradiated by Kr-beam was observed by means of continuous measurements of nano-indentation technique. • Modified mechanical properties show fluence-dependence. • Young's modulus is more sensitive to crystal to amorphous phase transition while hardness is more sensitive to damage induced by ion beam irradiation. • The depth profile of modified mechanical properties have a potential application of determining the longitudinal size of phase transition region induced by nanoindentation. - Abstract: The application of ion-beam irradiation in fabrication of structures with micro-/nanometer scale has achieved striking improvement. However, an inevitable damage results in the change of mechanical properties in irradiated materials. To investigate the relation between mechanical properties and ion-irradiation damages, nanoindentation was performed on crystalline silicon irradiated by Kr-beam with an energy of 240 keV. Modified Young's modulus and nanohardness, provided from the indentation, indicated fluence dependence. Stopping and range of ions in matter (SRIM) calculation, transmission electron microscopy (TEM) observation, and Rutherford backscattering-channeling (RBS-C) measurement were utilized to understand the irradiation effect on mechanical properties. In addition, the longitudinal size of the phase transition region induced by indentation was firstly evaluated based on the depth profile of modified nanohardness

  2. Strange light emission from the nonlinear optical crystal by FEL irradiation

    During a tuning to generate second-harmonics from the FEL with wave-length of 1640nm by using the nonlinear optical crystal BBO at LEBRA, we observed non-harmonic visible light emission with large dispersion angle. The emission appears when the crystal is set detuned angle. The color changes depending on the crystal angle and the FEL intensity. By irradiation of the enhanced FEL by means of the burst-mode operation of the linac, bright arcs appeared around the emission. (author)

  3. Dielectric spectra of doped and X-ray irradiated calcium fluoride crystals

    Calcium fluoride crystals doped with PbF2 and codoped with LiF, NaF have been grown using the vertical Bridgman method. The frequency (1-100 kHz) dependence of the real and imaginary parts of the complex dielectric constant, ε1 and ε2, have been studied in the temperature range 160-300 K; the activation parameters of the relaxation process have been determined for various doped and X-irradiated calcium fluoride crystals. The optical absorption spectra of the crystals are also investigated. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Optical transitions in magnesium aluminate spinel crystals of different compositions exposed to irradiation

    Optical absorption of magnesium aluminate spinel single crystals of different compositions MgO · nAl2O3 (n=1.0 and 2.5) were investigated after irradiation with neutrons, X-rays and the UV-light to elucidate existence of specific absorption bands related to lattice defects. The radiation induced absorption envelope is shifted to higher energy and is larger in intensity in non-stoichiometric spinel in comparison with stoichiometric one at the same irradiation conditions. Deconvolution of difference optical spectra of irradiated crystals shows the shift of the F-type centers from 4.75 and 5.3 eV in stoichiometric crystals to 5.08 and 5.63 eV in MgO · 2.5Al2O3 for F+- and F-centers, respectively. The absorption bands at 3.1 and 3.78 eV are present in both stoichiometric and non-stoichiometric crystals and are identified as V-type centers. By changing the irradiation time and using isochronal annealing it was revealed that additional bands appear in optical absorption spectra at 4.15 eV for MgO · 1.0Al2O3 crystals and at 4.46 eV for MgO · 2.5Al2O3 crystals. From the shift of the band energy position and the high intensity of this band in non-stoichiometric spinel crystals, it could be identified with electronic centers related to lattice defects

  5. Optical transitions in magnesium aluminate spinel crystals of different compositions exposed to irradiation

    Gritsyna, V.T. E-mail: gritsyna@pht.univer.kharkov.ua; Afanasyev-Charkin, I.V.; Kazarinov, Yu.G.; Sickafus, K.E

    2004-06-01

    Optical absorption of magnesium aluminate spinel single crystals of different compositions MgO {center_dot} nAl{sub 2}O{sub 3} (n=1.0 and 2.5) were investigated after irradiation with neutrons, X-rays and the UV-light to elucidate existence of specific absorption bands related to lattice defects. The radiation induced absorption envelope is shifted to higher energy and is larger in intensity in non-stoichiometric spinel in comparison with stoichiometric one at the same irradiation conditions. Deconvolution of difference optical spectra of irradiated crystals shows the shift of the F-type centers from 4.75 and 5.3 eV in stoichiometric crystals to 5.08 and 5.63 eV in MgO {center_dot} 2.5Al{sub 2}O{sub 3} for F{sup +}- and F-centers, respectively. The absorption bands at 3.1 and 3.78 eV are present in both stoichiometric and non-stoichiometric crystals and are identified as V-type centers. By changing the irradiation time and using isochronal annealing it was revealed that additional bands appear in optical absorption spectra at 4.15 eV for MgO {center_dot} 1.0Al{sub 2}O{sub 3} crystals and at 4.46 eV for MgO {center_dot} 2.5Al{sub 2}O{sub 3} crystals. From the shift of the band energy position and the high intensity of this band in non-stoichiometric spinel crystals, it could be identified with electronic centers related to lattice defects.

  6. Optical transitions in magnesium aluminate spinel crystals of different compositions exposed to irradiation

    Gritsyna, V. T.; Afanasyev-Charkin, I. V.; Kazarinov, Yu. G.; Sickafus, K. E.

    2004-06-01

    Optical absorption of magnesium aluminate spinel single crystals of different compositions MgO · nAl 2O 3 ( n=1.0 and 2.5) were investigated after irradiation with neutrons, X-rays and the UV-light to elucidate existence of specific absorption bands related to lattice defects. The radiation induced absorption envelope is shifted to higher energy and is larger in intensity in non-stoichiometric spinel in comparison with stoichiometric one at the same irradiation conditions. Deconvolution of difference optical spectra of irradiated crystals shows the shift of the F-type centers from 4.75 and 5.3 eV in stoichiometric crystals to 5.08 and 5.63 eV in MgO · 2.5Al 2O 3 for F +- and F-centers, respectively. The absorption bands at 3.1 and 3.78 eV are present in both stoichiometric and non-stoichiometric crystals and are identified as V-type centers. By changing the irradiation time and using isochronal annealing it was revealed that additional bands appear in optical absorption spectra at 4.15 eV for MgO · 1.0Al 2O 3 crystals and at 4.46 eV for MgO · 2.5Al 2O 3 crystals. From the shift of the band energy position and the high intensity of this band in non-stoichiometric spinel crystals, it could be identified with electronic centers related to lattice defects.

  7. Kinetics of nucleation and coarsening of colloids and voids in crystals under irradiation

    Dubinko, V.I.; Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den

    2002-01-01

    The kinetics of nucleation and coarsening of vacancy clusters in irradiated crystals are considered with account of their elastic interaction with point defects resulting in the biased absorption of vacancies and interstitial atoms. It is shown that in the technologically important range of high dos

  8. Defect-production efficiency in spinel crystals under electron and gamma-neutron irradiation

    The origin and concentration of defects in MgOxnAl2O3 (n=1 and 2.5) crystals were investigated after irradiation with reactor neutrons, electrons, X-rays and UV-light. Low efficiency of defect production in cation sublattice are explained by small coefficient of cation site filling

  9. EPR investigation of gamma irradiated single crystal guaifenesin: A combined experimental and computational study

    Tasdemir, Halil Ugur; Sayin, Ulku; Türkkan, Ercan; Ozmen, Ayhan

    2016-04-01

    Gamma irradiated single crystal of Guaifenesin (Glyceryl Guaiacolate), an important expectorant drug, were investigated with Electron Paramagnetic Resonance (EPR) spectroscopy between 123 and 333 K temperature at different orientations in the magnetic field. Considering the chemical structure and the experimental spectra of the gamma irradiated single crystal of guaifenesin sample, we assumed that alkoxy or alkyl-type paramagnetic species may be produced by irradiation. Depending on this assumption, eight possible alkoxy and alkyl-type radicals were modeled and EPR parameters of these modeled radicals were calculated using the B3LYP/6-311++G(d,p)-level of density functional theory (DFT). Theoretically calculated values of alkyl-type modeled radical(R3) are in good agreement with experimentally determined EPR parameters of single crystal. Furthermore, simulation spectra which are obtained by using the theoretical initial values are well matched with the experimental spectra. It was determined that a stable Cα •H2αCβHβCγH2γ (R3) alkyl radical was produced in the host crystal as a result of gamma irradiation.

  10. Photon irradiation response of photonic crystal fibres and flat fibres at radiation therapy doses

    Radiation effects of photon irradiation in pure Photonic Crystal Fibres (PCF) and Flat fibres (FF) are still much less investigated in thermoluminescense dosimetry (TLD). We have reported the TL response of PCF and FF subjected to 6 MV photon irradiation. The proposed dosimeter shows good linearity at doses ranging from 1 to 4 Gy. The small size of these detectors points to its use as a dosimeter at megavoltage energies, where better tissue-equivalence and the Bragg–Gray cavity theory prevails. - Highlights: • First study about radiation effects of photon irradiation in pure Photonic Crystal Fibres (PCF) and Flat fibres (FF). • PCF and FF. have been found to have good dose linearity (up to 4 Gy). • The value of Zeff obtained is in the range of 10.3–11.3 and 11.3–11.8 for PCF and FF respectively

  11. Development of a neutron irradiation device with a cooled crystal filter: Radiation physical properties and applications in in vivo irradiations

    The radiation-physical and geometrical properties of a neutron-beam, collimated with a Bi-crystal filter were investigated at the reactor BER II. The influence of the crystal temperature as well as the actions of a reflector and a collimator on neutron flux-density and neutron field of the thermal neutrons were investigated. The dose contributions of the thermal, epithermal and fast neutrons as well as γ-radiation was determined by activation of the sample respective with TLD-measurements. The influence of irradiation and measurement geometry on the sensitivity and detection probability was investigated by means of phantom irradiations. The method prooved to be suitable, to detect changes of the Ca-content in a rat hind leg by about 10%. In investigations on animal groups of about 10 animals a threshold of detectability for changes of the ca-content is to be expected by about 4%. In a further group experiment it was found, that even in the case of multiple radiation the procedure of irradiation and measurement was not followed by a significant change in the Ca-content of the hind legs of the testing animals. (orig.)

  12. Coherent polarization radiation from crystals irradiated with relativistic charged particles

    When polarization radiation (polarization bremsstrahlung) occurs in a crystal, the radiation becomes coherent in X-ray wavelengths. This radiation, called coherent polarization radiation (CPR) in this paper, is considered as a possible compact X-ray source because CPR is intense, monochromatic, tunable, small background, and easy to extract. We present a simple theory of CPR with emphasis on its relation to Cherenkov radiation and transition radiation. Various properties of CPR are also discussed

  13. Gamma irradiated LDPE in presence of oxygen. Part I. Non-isothermal crystallization

    Alvarez, V.A. [Composite Materials Group (CoMP), Research Institute of Material Science and Technology (INTEMA), Engineering Faculty, National University of Mar del Plata UNMdP, Solís 7575, B7608FDQ, Mar del Plata (Argentina); Perez, C.J., E-mail: cjperez@fi.mdp.edu.ar [Science and Technology Polymer Group, Research Institute of Material Science and Technology (INTEMA) – National University of Mar del Plata (UNMdP), Av. Juan B. Justo 4302, B7608FDQ, Mar del Plata (Argentina)

    2013-10-20

    Highlights: • Dynamical crystallization process of irradiated LDPE in different atmospheres was studied. • The radiation dose retards the overall crystallization process of LDPE in a given atmosphere. • At constant radiation dose, crystallization is accelerated with increasing the oxygen content. • Parameters of the used models and CCT diagrams are in good agreement with explained tendencies. - Abstract: Non isothermal crystallization of low density polyethylene (LDPE) samples irradiated under three different atmospheres was analyzed. The used doses were between 33 and 222 kGy and the atmospheres content 0, 21 and 100% of oxygen. At a given radiation dose, the amount of produced gel is higher when the oxygen content present in the radiation process is lower. The temperature and the enthalpy of crystallization of the modified polymer decreased almost linearly with the radiation dose. Different classic models were used to predict the development of the relative degree of crystallinity (in the range 0.01–0.3 crystallinity fraction) as a function of temperature and several parameters were analyzed. The values of half-time of crystallization (t{sub 1/2}) and the parameter Z{sub c}, from Avrami's method which characterize the kinetics of non-isothermal crystallization, showed that the crystallization rate, at the same cooling rate, decreased with increasing radiation dose and, at the same dose, with the decrease in the oxygen content. The activation energy for crystallization increased with the radiation dose and with the reduction of the oxygen content, indicating that the increment in molecular crosslinking restricts the crystallization process.

  14. Optical and thermal stability of Ag centers in RT X-irradiated KCl:Ag crystals

    The optical absorption, thermoluminescence (TL), monochromatic TL, and TL spectra of potassium chloride crystals doped heavily with silver are measured after X-irradiation at RT. The effect of optical bleaching on X-irradiated crystals with light in the F, E, and B bands both, separately and together, as well as thermal annealing effects of the defect centres are studied. It is found that in the heavily doped crystals the role of holes in the form of doubly charged impurity ions (Ag++) is predominant compared to holes of the host lattice in the form of Cl2- etc. The Ag ions stabilised only at cation sites in different valence states are involved in the recombination-luminescence process. From the TL spectral data of the glow peaks preferential redistribution of the excess electron centres on optical bleaching is evident. The results support that tunnelling of electrons is responsible for the observed TL and TL spectral data. (author)

  15. Mobility of edge dislocations in stressed iron crystals during irradiation

    Korchuganov, A. V., E-mail: avkor@ispms.ru; Zolnikov, K. P.; Kryzhevich, D. S. [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Chernov, V. M. [A.A. Bochvar High-Technology Scientific Research Institute for Inorganic Materials, Moscow, 123098 (Russian Federation); Psakhie, S. G. [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Skolkovo Institute of Science and Technology, Skolkovo, 143025 (Russian Federation)

    2015-10-27

    The behavior of a/2(111)(110) edge dislocations in iron in shear loading and irradiation conditions was studied by means of molecular dynamics simulation. Edge dislocations were exposed to shock waves formed by atomic displacement cascades of different energies. It was shown that starting from a certain threshold amplitude shock waves cause displacement of edge dislocations in the loaded samples. Calculations showed that the larger the shear load and the amplitude of the shock wave, the greater the displacement of dislocations in the crystallite.

  16. Effect of defects induced by doping and fast neutron irradiation on the thermal properties of lithium ammonium sulphate crystals

    Structural defects were introduced in lithium ammonium sulphate crystals (LAS) either in the process of crystal growth (in the form of foreign ions) or by neutron irradiation. The effect of such defects on the thermal properties of LAS crystals was studied in the temperature range 300-500 K. It was assumed that the doped LAS crystals are composed of a two-phase system having different thermal parameters in each phase. The specific heat at constant pressure, Cp, of irradiated samples was found to decrease with increasing irradiation doses. The thermal expansion of LAS crystals was found to be dependent on neutron irradiation, and was attributed to two processes: the release of new species and the trapping process. (author)

  17. Effects of the auto irradiation in KBr:Eu2+ crystals

    In KCl :Eu2+ crystals and in KBr :Eu2+ crystals it has been detected the effect of the auto irradiation with 40 K isotope. In this work, a study of auto irradiation thermoluminescence in KBr :Eu2+ crystals with different Eu2+ concentrations and different thermal treatments is presented. The form of the Tl curve shows mainly a sparkle at 110 Centigrade degrees. The sparkle intensity increases linearly in a time interval around 3600 sec. After this time the increase of intensity was slower. In the linear interval, the lukewarm effects are almost scornful. The analysis of results is looked to the relation between the thermoluminescence and the Eu2+ additions. It is discussed the form of the curve comparing it with the Tl induced by external irradiation sources on this type of materials. Also it is discussed the temporary dependence of the quantity of induced defects. Finally, the Tl intensity results for crystals with and without previous luke warms are compared. (Author)

  18. Helium release from neutron-irradiated Li{sub 2}O single crystals

    Yamaki, Daiju; Tanifuji, Takaaki; Noda, Kenji [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    Helium release behavior in post-irradiation heating tests was investigated for Li{sub 2}O single crystals which had been irradiated with thermal neutrons in JRR-4 and JRR-2, and fast neutrons in FFTF. It is clarified that the helium release curves from JRR-4 and JRR-2 specimens consists of only one broad peak. From the dependence of the peak temperatures on the neutron fluence and the crystal diameter, and the comparison with the results obtained for sintered pellets, it is considered that the helium generated in the specimen is released through the process of bulk diffusion with trapping by irradiation defects such as some defect clusters. For the helium release from FFTF specimens, two broad peaks were observed in the release curves. It is considered to suggest that two different diffusion paths exist for helium migration in the specimen, that is, bulk diffusion and diffusion through the micro-crack due to the heavy irradiation. In addition, helium bubble formation after irradiation due to the high temperature over 800K is suggested. (J.P.N.)

  19. Digested livestock wastewater treatment using gamma-ray irradiation and struvite crystallization

    Kim, Tak Hyun; Lee, Sang Ryul; Nam, Youn Ku; Lee, Myun Joo [Korea Atomic Energy Research Institute, Jeongeup (Korea, Republic of)

    2009-06-15

    Livestock wastewater generally contains high strength of organics (COD), ammonia nitrogen (NH{sub 4}{sup +} -N), phosphate phosphorus (PO{sub 4}{sup 3-} -P) and suspended solids. It is very difficult to treat by conventional wastewater treatment techniques. In this study, struvite crystallization was carried out to treat the digested livestock wastewater. 1.0 :1.2 :1.2 was determined as an optimal NH{sub 4}+ :Mg{sup 2+} : PO{sub 4}{sup 3-} mol ratio of struvite crystallization. For the digested livestock wastewater, COD, NH{sub 4}{sup +} -N and PO{sub 4}{sup 3-} -P removal efficiencies by struvite crystallization were 72.4%, 98.9%, and 74.8%, respectively. Gamma-ray irradiation was carried out prior to struvite crystallization of livestock wastewater. The enhancement of struvite crystallization efficiency could be obtained by the pretreatment of gamma-ray irradiation due to the decrease of COD, NH{sub 4}{sup +} -N and PO{sub 4}{sup 3-} -P concentration.

  20. Effects of ultrasonic irradiation on crystallization and structural properties of EMT-type zeolite nanocrystals

    Synthesis of EMT zeolite nanocrystals from rice husk ash biomass (RHA) under continuous ultrasonic irradiation is reported. The aging, nucleation and crystallization stages of EMT zeolite in the system were monitored at ambient temperature, and compared with the conventional hydrothermal method. It was found that ultrasonic wave induced rapid crystal growth of the nanosized EMT zeolite. Complete crystallization of EMT nanocrystals was achieved within 24 h which was much faster than conventional hydrothermal synthesis (36 h). Furthermore, XRD and TEM analyses revealed that more nuclei were formed during the nucleation stage, allowing the preparation of smaller zeolite nanocrystals with high crystallinity. The results also showed that sonocrystallization produced EMT zeolite with high yield (ca. 80%). The ultrasound-prepared EMT nanocrystals were also found to have high porosity and high hydrophilicity, making the material promising for water sorption applications including vapor sensing, heat pump and adsorption technologies. - Highlights: • Nanosized EMT zeolites are formed from rice husk ash under ultrasonic irradiation. • The effects of ultrasonic waves in nanosized EMT zeolite synthesis are studied. • Ultrasound induces rapid crystal growth and produces high zeolite yield. • Smaller zeolite nanocrystals with high crystallinity and large defect sites are obtained. • Improved surface hydrophilicity of crystals is beneficial for water sorption applications

  1. Effects of ultrasonic irradiation on crystallization and structural properties of EMT-type zeolite nanocrystals

    Ng, Eng-Poh, E-mail: epng@usm.my [School of Chemical Sciences, Universiti Sains Malaysia, USM, 11800 Penang (Malaysia); Awala, Hussein [Laboratoire Catalyse & Spectrochimie, CNRS-ENSICAEN, Université de Caen (France); Ghoy, Jia-Pei [School of Chemical Sciences, Universiti Sains Malaysia, USM, 11800 Penang (Malaysia); Vicente, Aurélie [Laboratoire Catalyse & Spectrochimie, CNRS-ENSICAEN, Université de Caen (France); Ling, Tau Chuan [Institute of Biological Sciences, Faculty of Science, University of Malaya (Malaysia); Ng, Yun Hau [School of Chemical Engineering, The University of New South Wales, Sydney (Australia); Mintova, Svetlana [Laboratoire Catalyse & Spectrochimie, CNRS-ENSICAEN, Université de Caen (France); Adam, Farook, E-mail: farook@usm.my [School of Chemical Sciences, Universiti Sains Malaysia, USM, 11800 Penang (Malaysia)

    2015-06-01

    Synthesis of EMT zeolite nanocrystals from rice husk ash biomass (RHA) under continuous ultrasonic irradiation is reported. The aging, nucleation and crystallization stages of EMT zeolite in the system were monitored at ambient temperature, and compared with the conventional hydrothermal method. It was found that ultrasonic wave induced rapid crystal growth of the nanosized EMT zeolite. Complete crystallization of EMT nanocrystals was achieved within 24 h which was much faster than conventional hydrothermal synthesis (36 h). Furthermore, XRD and TEM analyses revealed that more nuclei were formed during the nucleation stage, allowing the preparation of smaller zeolite nanocrystals with high crystallinity. The results also showed that sonocrystallization produced EMT zeolite with high yield (ca. 80%). The ultrasound-prepared EMT nanocrystals were also found to have high porosity and high hydrophilicity, making the material promising for water sorption applications including vapor sensing, heat pump and adsorption technologies. - Highlights: • Nanosized EMT zeolites are formed from rice husk ash under ultrasonic irradiation. • The effects of ultrasonic waves in nanosized EMT zeolite synthesis are studied. • Ultrasound induces rapid crystal growth and produces high zeolite yield. • Smaller zeolite nanocrystals with high crystallinity and large defect sites are obtained. • Improved surface hydrophilicity of crystals is beneficial for water sorption applications.

  2. Effect of crystal orientation on low flux helium and hydrogen ion irradiation in polycrystalline tungsten

    Liu, Fangshu [Department of Physics, Beihang University, Beijing 100191 (China); School of Material Engineering, Panzhihua University, Panzhihua 617000 (China); Ren, Haitao; Peng, Shixiang [State Key Laboratory of Nuclear Physics and Technology, Institute of Heavy Ion Physics, Peking University, Beijing 100871 (China); Zhu, Kaigui, E-mail: kgzhu@buaa.edu.cn [Department of Physics, Beihang University, Beijing 100191 (China)

    2014-08-15

    Blistering behavior in polycrystalline tungsten is investigated under low flux helium and hydrogen ion irradiation. Subsequent to irradiation, the grain orientations near (0 1 1), (1 0 1) and (1 1 1) planes on the surface are analyzed by SEM and EBSD. It is found that blister density is the greatest on the grain orientation near (1 1 1) plane, and the smallest on the grain orientation near (0 0 1) plane. Experiments suggest that blistering degree highly depends upon the grain orientation, blisters are easily formed on the grain orientation near (1 1 1) plane, and medium on the grain orientation near (1 0 1) plane, and the most rare on the grain orientation near (0 1 1) plane. The surface resistant orientation of tungsten is orientation near (0 0 1) plane. The atom binding energy in the crystal plane in combination with the channeling effect of adjacent crystal planes may play an important role for the difference of the surface morphology.

  3. Thermoluminescence studies on γ-irradiated Mn:Li2B4O7 single crystals

    Manganese doped Li2B4O7 (LTB) crystals were grown by Czochralski technique and various kinetic parameter of thermoluminescence (TL) were measured. Crystals were irradiated with different γ-dose using Co60 source. Thermoluminescence curves were recorded at various heating rates. Trap depth and frequency factor were calculated. Fading of Mn: Li2B4O7 was found only ∼5%-6% in 6 months. Thermoluminescence intensity of Mn: Li2B4O7 was found highly sensitive to the mass of the material, and it varies abruptly with mass change of +/− 1 mg, irradiated with the same dose. Therefore, the accuracy in mass is important parameter for thermoluminescence dosimeter badge.

  4. Liquid Crystal Alignment on Solution Derived Zinc Oxide Films via Ion Beam Irradiation.

    Park, Hong-Gyu; Han, Jae-Jun; Seo, Dae-Shik

    2016-03-01

    A 75-nm-thick ZnO film was deposited by a sol-gel method on indium-tin oxide (ITO)-coated glass. This film served as a liquid crystal (LC) alignment layer. We report the fabrication and characteristics of this film after ion-beam (IB) irradiation. Uniform LC alignment was achieved at an IB incident energy above 2400 eV. The IB-treated ZnO surface was analyzed by X-ray photoelectron spectroscopy (XPS), monitoring the intensity of the Zn 2p and O 1s peaks as a function of IB-irradiation energy density. The electro-optical (EO) characteristics of a twisted nematic-liquid crystal display (TN-LCD) were comparable to rubbed polyimide. PMID:27455726

  5. Optical and electrical properties of cadmium sulphide single crystals irradiated by electrons

    We present the data concerning the optical and electrical properties of specially undoped and Cu-doped CdS single crystals with defects generated under irradiation by electrons with the energy of 1.2 MeV. The dose dependences of defect generation and temperature dependences of the annealing of radiation defects in these crystals are investigated. Analysis of the obtained results gives the possibility to study the relations of generation of initial defects and their complex in binary semiconductors. Conclusions about the structure of defects which determine bands of green, orange, red, and infrared luminescence of CdS and about their rearrangement under the annealing of irradiated samples are done

  6. Swelling, thermal diffusivity and microstructural investigation of neutron-irradiated single crystals of nonstoichiometric spinel

    Single crystals of nonstoichiometric magnesium aluminate spinel (MgO.3A12O3) were neutron-irradiated in the Japan Materials Testing Reactor (JMTR) to fluences (E >1 MeV) from 8.3x1022 n/m2 at 373 K to 5.3x1024 n/m2 at 1058 K. Changes in macroscopic length, lattice parameter and thermal duffusivity for the specimen irradiated to a fluence of 8.3x1022 n/m2 at 373 K were +0.065%, +0.076% and -27%, respectively. On the other hand, those for the specimen irradiated to a fluence of 2.4x1024 n/m2 at 743 K were +0.008%, +0.021% and -1%, respectively. Microstructural examination by transmission electron microscopy revealed no evidence of any agglomerated damage for the specimen irradiated to a fluence of 8.3x1022 n/m2 at 373 K, whereas a number of finer interstitial Frank loops (≅ 20 nm in diameter) having the Burgers vector of the {111} type were observed in the specimen irradiated to a fluence of 2.4x1024 n/m2 at 743 K. The specimen irradiated to a fluence of 5.2x1024 n/m2 at 1058 K formed precipitates in the spinel phase, which was identified to be the type II intermediate phase of spinel. (orig.)

  7. A comparison of 95 MeV oxygen ions and 60Co gamma irradiation effect on nonlinear optical L-alanine cadmium chloride single crystals

    Single crystal of nonlinear optical (NLO) material L-alanine cadmium chloride (LACC) was grown by slow evaporation method at room temperature. The grown crystals were irradiated with 95 MeV oxygen ions and 60Co gamma radiation at doses of 1 Mrad and 6 Mrad. The structural, chemical, dielectric properties, AC and DC conductivity, refractive index of the crystals were studied before and after irradiation. There is a slight change in the lattice parameters due to compressive strain field generated in the irradiated crystals. The observed increase in dielectric constant was found to be more for 60Co gamma irradiated crystals than 95 MeV oxygen ion irradiated crystal. A considerable change in the values of refractive indices was observed for both gamma and ion irradiated crystals. The AC and DC conductivity was found to increase after irradiation. (author)

  8. Thermally and optically stimulated processes in X-irradiated scheelite type crystals

    Böhm, M.; Grasser, R.; Hofstaetter, A.; Scharmann, A.

    1980-01-01

    In tungstate and molybdate crystals having scheelite structure various (intrinsic and extrinsic) hole and electron centres are created by X-irradiation at liquid nitrogen temperature. Several of these centres have been thoroughly investigated by electron paramagnetic resonance (EPR) measurements. Their thermal decay and optical bleaching, resp., can be related to glow peaks of thermoluminescence and thermally resp. optically stimulated conductivity as well as characteristic changes in optical...

  9. Zenithal alignment of liquid crystal on homeotropic polyimide film irradiated by ion beam

    Choi, Yoonseuk; Yoon, Tae-Hoon; Kwon, Jin Hyuk; Yi, Jonghoon; Gwag, Jin Seog

    2012-01-01

    We investigate the pretilt characteristics of a nematic liquid crystal [LC] in terms of ion beam exposure conditions on the homeotropic polyimide alignment layer. The pretilt angle of LCs in the case of high-energy ion beam treatment was decreased considerably almost the same to that of the homogenous alignment layer though we used homeotropic polyimide film at first. Increasing irradiating energy, we could control the pretilt from 90° to 1° with several steps. We believe that this is because...

  10. Impact of Conditions of Irradiation on Nature of Radiation Defects in n-Si Crystals

    It is shown that efficiency of formation of radiation defects of high thermal stability with annealing temperature (Tann≥400℃) in n-type silicon crystals reaches its maximum at irradiation temperature Tirr=150℃. The observed effect may be explained by formation of multy-vacancy, phosphorus-containing defects (double phosphorus vacancy PV2 or triple phosphorus vacancy PV3) based on thermally ionized E centers and non-equilibrium negative mono-vacancies. (author)

  11. Thermo-exoemission of NaCl:Ag crystals, cleaved before and after X-irradiation

    Sorkin, B.; Kaeaembre, H. (AN Ehstonskoj SSR, Tartu. Inst. Fiziki)

    1984-06-16

    Thermally stimulated exoelectron emission (TSEE) has been measured in Ag-doped NaCl crystal slices cleaved before and after X-irradiation. The TSEE peaks in the thermal spectra obtained for excitation at 100 and 295 K, respectively have been assigned to different volume traps and surface processes. It is concluded that TSEE of NaCl:Ag cannot be completely reduced to surface excitation processes.

  12. Effect of thermal treatment and γ-irradiation on optical properties of gadolinium silicate (GSO) crystals

    Absorption spectra (AS) and thermoluminescence (TL) curves are studied for γ-irradiated and thermally treated gadolinium silicate (Gd2SiO5:Ce) crystals in oxidized and reducible environment. It is demonstrated that reducing thermal treatment leads to increase of absorption band intensities and TL peaks, whereas oxidisation thermal treatment does not lead to changes in the above properties. The nature of traps causing TL peaks is determined. (authors)

  13. Optical bleaching of BaFCl crystals X-irradiated at room temperature

    The optical bleaching behaviour of the optical absorption bands produced by X-irradiation is investigated by paying particular attention to the difference between the two types of F centers in the BaFCl crystals. The optical bleachings are performed using a Xe-lamp. The optical absorption spectra and changes in the absorption bands during bleaching with F(Cl-) and F(F-) light are given and discussed

  14. Mechanoluminescence produced during cleavage of γ-irradiated alkali halide crystals

    When g-irradiated alkali halide crystals are cleaved, then in their mechanoluminescence (ML) intensity versus time curve, two peak intensities Im1 and Im2 are observed at time tm1 and tm2 respectively. The ML intensity both beyond tm1 and tm2 decrease exponentially. It is shown that ML provides a new technique for determining the pinning time of dislocations and lifetime of the electrons in dislocation band. (author)

  15. Amorphous to single crystal transition in Si induced by ion-beam irradiation

    The amorphous to single crystal transition in Si can occur at temperatures as low as 2000C during ion-beam irradiation. The ion-assisted recyrstallization of amorphous Si is here briefly reviewed. In particular the dependence of the process on the energy deposited by the impinging ions into elastic collision, on temperature and on impurities dissolved in the amorphous layer is presented and discussed. (orig.)

  16. Thermoluminescence of CsCl:Ce crystals irradiated with gamma rays

    UV-visible absorption spectrum of CsCl:Ce crystal shows two sharp bands at 267nm and 205nm. Upon γ-irradiation the characteristic F and V bands form, which are similar to those observed in pure CsCl. Three glow peaks at 363 K, 378 K and 408 K have been identified in the irradiated crystals. The resistance of the 408 K peak to F-bleaching, is more compared to the lower temperature peaks. The TL emission spectra show emission bands at 445nm and 388nm. The 388nm band is attributed to the emission of Ce3+ ions and the 445nm band is attributed to the emission of Eu2+ ions, which were present as unintentional impurities. These results are correlated with the photoluminescence spectra. The thermoluminescence emission of γ-irradiated CsCl:Ce crystal appears to be due to the energy transfer from the recombining F-center electron and V-center pair, to the nearby Ce3+ and Eu2+ ions in the lattice. (author). 11 refs., 5 figs

  17. Large-area regular nanodomain patterning in He-irradiated lithium niobate crystals

    Ofan, A; Gaathon, O; Osgood, R M Jr [Center for Integrated Science and Technology, Columbia University, New York, NY 10027 (United States); Lilienblum, M; Hoffmann, A; Soergel, E [Institute of Physics, University of Bonn, Wegelerstrasse 8, 53115 Bonn (Germany); Sehrbrock, A; Irsen, S [Center of Advanced European Studies and Research (CAESAR), Ludwig-Erhard-Allee 2, 53175 Bonn (Germany); Bakhru, S; Bakhru, H, E-mail: ao2199@columbia.edu, E-mail: soergel@uni-bonn.de [College of Nanoscale Science and Engineering, State University of New York at Albany, Albany, NY 12222 (United States)

    2011-07-15

    Large-area ferroelectric nanodomain patterns, which are desirable for nonlinear optical applications, were generated in previously He-implanted lithium niobate crystals by applying voltage pulses to the tip of a scanning force microscope. The individual nanodomains were found to be of uniform size, which depended only on the inter-domain spacing and the pulse amplitude. We explain this behavior by the electrostatic repulsion of poling-induced buried charges between adjacent domains. The domain patterns were imaged by piezoresponse force microscopy and investigated by domain-selective etching in conjunction with focused ion beam etching followed by scanning electron microscopy imaging. In order to optimize the He-irradiation parameters for easy and reliable nanodomain patterning a series of samples subjected to various irradiation fluences and energies was prepared. The different samples were characterized by investigating nanodomains generated with a wide range of pulse parameters (amplitude and duration). In addition, these experiments clarified the physical mechanism behind the facile poling measured in He-irradiated lithium niobate crystals: the damage caused by the energy loss that takes place via electronic excitations appears to act to stabilize the domains, whereas the nuclear-collision damage degrades the crystal quality, and thus impedes reliable nanodomain generation.

  18. β-ray irradiation effects in RbBr: Eu crystals

    Defects induced by β-ray irradiation in RbBr: Eu2+ crystals doped with a high concentration of Eu2+ ions are studied by means of optical absorption (OA), thermoluminescence (TL), and optically stimulated TL (OSTL). The fading, dose, and optical bleaching effects on the TL glow curves of room temperature irradiated samples has been analyzed. OA indicates that irradiation of samples at room temperature induce the formation of F but not Fz centers. The TL glow curves show peaks at 267, 303, and 403 K. The 267 K glow peak disappear in less than 1 s under blue light or infrared radiation photo bleaching. A high sensitivity to the ionizing radiation has been observed. These results confirm that this material is an efficient phosphor. (Author)

  19. Fluorescence-based remote irradiation sensor in liquid-filled hollow-core photonic crystal fiber

    Zeltner, R.; Bykov, D. S.; Xie, S.; Euser, T. G.; Russell, P. St. J.

    2016-06-01

    We report an irradiation sensor based on a fluorescent "flying particle" that is optically trapped and propelled inside the core of a water-filled hollow-core photonic crystal fiber. When the moving particle passes through an irradiated region, its emitted fluorescence is captured by guided modes of the fiber core and so can be monitored using a filtered photodiode placed at the fiber end. The particle speed and position can be precisely monitored using in-fiber Doppler velocimetry, allowing the irradiation profile to be measured to a spatial resolution of ˜10 μm. The spectral response can be readily adjusted by appropriate choice of particle material. Using dye-doped polystyrene particles, we demonstrate detection of green (532 nm) and ultraviolet (340 nm) light.

  20. Structure of InP single crystals irradiated with reactor neutrons

    The structural characteristics of InP single crystals have been investigated depending on the radiation effects produced by fast neutrons and the full spectrum of the reactor neutrons and subsequent heat treatment procedures. The lattice parameter of InP single crystals decreases under neutron irradiation as opposed to other III-V semiconductor compounds. Fast neutrons make the main contribution to the change of the lattice parameter. A thermal neutron component initiates the formation of Sn atoms in the material, but does not influence the change of the lattice parameter significantly. Heat treatment of the irradiated samples up to 600 deg. C causes annealing of the radiation defects and recovery of the lattice parameter. With increasing neutron fluences, the lattice parameter becomes even higher than before irradiation. The data analysis proves the following assumption: anti-site defects PIn mainly contribute to the lattice parameter decrease during neutron irradiation of InP. In this case, anti-site imperfections produce an effect similar to that of vacancy defects

  1. The Effect of Compression on the Annealing Behaviour of Neutron-Irradiated Potassium Dihydrogen Arsenate Crystals

    The annealing behaviour of As76 atoms (from (n, γ) reaction) and As74 atoms (from (n, 2n) reaction) in neutron (slow and fast) irradiated potassium dihydrogen arsenate crystals with and without compression has been studied. Several times recrystallized, A.R. grade potassium dihydrogen arsenate crystals sieved to 20-30 and 30-80 mesh size were used for irradiation in the BEPO reactor and for fast neutron irradiation. Thermal annealing was performed in a thermostatically controlled air oven. The compression of samples was carried out in sealed copper tubes either with or without liquid paraffin as medium. Applied pressure ranged up to 2000 atm. The distribution of radioactive arsenic atoms between tri- and pentavalent form was carried out either by paper electrophoresis in 0.01M sodium hydroxide solutions (for slow-neutron-irradiated samples) or by gravimetric method as magnesium pyroarsenate (for fast-neutron-irradiated samples). Paper strips were counted by an end-window G-M tube. The magnesium pyroarsenate samples were counted after dissolution in sulphuric acid by means of a liquid counter. It has been found that there is no essential differente in annealing behaviour of As74 and As76 atoms both without and with pressure treatment, when the paraffin oil is used as pressure transmitting medium. When irradiated samples are compressed without paraffin oil, there is an increase of the content of the pentavalent form of arsenic as long as the pressure is applied before the pseudo-plateau for the given temperature has been reached. The amount of the change does not depend on the value of pressure applied, once the threshold value has been applied. The effect has been explained in terms of defects produced by slipping of dislocation lines, caused by anisotropic compression, when the pressure is applied without the paraffin oil as medium. (author)

  2. Afterglow in bulk AlN single crystals under β-irradiation

    Regularities of afterglow at room temperature and of thermoluminescence at further heating up to 673 K have been studied in bulk aluminum nitride single crystals. It has been established that after exposure to β-irradiation luminescence decay at RT may be described by superposition of two exponential components: fast (59 s) and slow (606 s) ones, caused by defects of the anion crystal sublattice ON- and VN-centers, respectively. The afterglow spectrum is shown to be characterized by the 3.43 eV band with FWHM=0.61 eV that dominates also in the thermoluminescence under study. From analysis of the TL curves in terms of the general order formalism it has been concluded that variation of the activation energy observed within the 0.46–0.85 eV range with increasing storage of the samples from 5 min to 3 days may be caused by energy distribution of traps on the basis of oxygen-related centers. For the first time the compensation effect has been found, and phenomenologically interpreted for the TL processes of the AlN single crystals. Isokinetic temperature has been estimated within the framework of empiric and non-empiric relations. - Highlights: ► Analysis of afterglow curves and emission spectra in irradiated bulk AlN crystals. ► Evaluation of kinetic and thermodynamic parameters of thermoluminescence. ► Observation of compensation effect in TL processes for AlN in the first time.

  3. Isothermal crystallization of gamma irradiated LDPE in the presence of oxygen

    Lanfranconi, M. R.; Alvarez, V. A.; Perez, C. J.

    2015-06-01

    This work is focused on the study of the effect of oxygen on the isothermal crystallization process of gamma irradiated low density polyethylene (LDPE). The induction time increased with the dose indicating a retarding effect. On other hand, at the same dose, this parameter decreased with the augment in the oxygen content. The classical Avrami equation was used to analyze the crystallization kinetic of these materials. n values suggested that both, the dose and the oxygen content, did not affect the mechanism of crystals growth. An Arrhenius type equation was used for the rate constant (k). Used models correctly reproduced the experimental data. TTT diagrams of studied materials were constructed and also reflected the effects of the doses and the oxygen content.

  4. Self-organization processes and nanocluster formation in crystal lattices by low-energy ion irradiation

    The goal of this paper is to study self-organization processes that cause nanostructural evolution in nonlinear crystal media. The subjects of the investigation were nonlinear homogeneous and heterogeneous atom chains. The method of computer simulation was used to investigate the interaction between low-energy ions and crystal lattices. It was based on the conception of three-dimensional lattice as a nonlinear atom chain system. We showed that that in homogeneous atom chains critical energy needed for self-organization processes development is less than for nonlinear atom chain with already embedded clusters. The possibility of nanostructure formation was studied by a molecular dynamics method of nonlinear oscillations in atomic oscillator systems of crystal lattices after their low-energy ion irradiation. (authors)

  5. Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

    Structural changes in magnesium aluminate spinel (MgO · nAl2O3) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne+ ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO · Al2O3 has a tendency to form the normal spinel configuration, where Mg2+ ions and Al3+ ions occupy mainly the tetrahedral and the octahedral sites, respectively. Electron irradiation induces simple cation disordering between the tetrahedral sites and the octahedral sites in MgO · Al2O3. In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO · Al2O3 irradiated with Ne+ ions. In contrast, cation disordering is suppressed in MgO · 2.4Al2O3 irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effective in promoting irradiation damage recovery through interstitial-vacancy recombination

  6. Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

    Soeda, Takeshi; Matsumura, Syo; Kinoshita, Chiken; Zaluzec, Nestor J.

    2000-12-01

    Structural changes in magnesium aluminate spinel (MgO · nAl 2O 3) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne + ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO · Al 2O 3 has a tendency to form the normal spinel configuration, where Mg 2+ ions and Al 3+ ions occupy mainly the tetrahedral and the octahedral sites, respectively. Electron irradiation induces simple cation disordering between the tetrahedral sites and the octahedral sites in MgO · Al 2O 3. In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO · Al 2O 3 irradiated with Ne + ions. In contrast, cation disordering is suppressed in MgO · 2.4Al 2O 3 irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effective in promoting irradiation damage recovery through interstitial-vacancy recombination.

  7. Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

    Soeda, Takeshi E-mail: soeda@regroup5.nucl.kyushu-u.ac.jp; Matsumura, Syo; Kinoshita, Chiken; Zaluzec, Nestor J

    2000-12-01

    Structural changes in magnesium aluminate spinel (MgO {center_dot} nAl{sub 2}O{sub 3}) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne{sup +} ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO {center_dot} Al{sub 2}O{sub 3} has a tendency to form the normal spinel configuration, where Mg{sup 2+} ions and Al{sup 3+} ions occupy mainly the tetrahedral and the octahedral sites, respectively. Electron irradiation induces simple cation disordering between the tetrahedral sites and the octahedral sites in MgO {center_dot} Al{sub 2}O{sub 3}. In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO {center_dot} Al{sub 2}O{sub 3} irradiated with Ne{sup +} ions. In contrast, cation disordering is suppressed in MgO {center_dot} 2.4Al{sub 2}O{sub 3} irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effective in promoting irradiation damage recovery through interstitial-vacancy recombination.

  8. AG, TL, and IRSL dosimetric properties in X-ray irradiated HPHT diamond crystals

    Gil-Tolano, M.I. [Programa de Posgrado, Departamento de Investigacion en Fisica, Universidad de Sonora, A. P. 5-088, Hermosillo, Sonora, 83190, Mexico (Mexico); Melendrez, R.; Lancheros-Olmos, J.C.; Soto-Puebla, D.; Chernov, V.; Pedroza-Montero, M.; Barboza-Flores, M. [Departamento de Investigacion en Fisica, Universidad de Sonora, A. P. 5-088, Hermosillo, Sonora, 83190, Mexico (Mexico); Castaneda, B. [Departamento de Fisica, Universidad de Sonora, Blvd. Luis Encinas y Rosales S/N, Hermosillo, Sonora, 83000, Mexico (Mexico)

    2014-10-15

    HPHT diamonds have been studied for several years for their potential in different applications. In previous studies it has been found that the thermoluminescence (TL) glow curves of ''as-grown'' HPHT diamonds are non-reproducible. In this work, we study the afterglow (AG), thermoluminescent (TL), and optically stimulated luminescence (OSL) response of commercial samples of synthetic HPHT type-Ib diamond crystals exposed to X-ray irradiation (0.75 mA, 35 kV) at a dose rate of 0.624 Gy/s, after a high gamma ({sup 60}Co) dose irradiation of 500 kGy followed by a thermal treatment at 1073 K for 1 h in nitrogen atmosphere. Deconvolution of the TL glow curves shows four peaks, located around 379, 509, 561, and 609 K. The crystals exhibit evident AG recorded for 300 s immediately after X-ray irradiation, due to the thermal emptying of the traps responsible for the low-temperature TL peaks (below 400 K). The stimulation of irradiated crystals with 870-nm light, creates pronounced OSL and destroys all TL peaks with the exception of the high-temperature peak at 609 K. The dose responses of the integrated AG, TL, and OSL are linear in the range of 0.6-5 Gy and saturated at higher doses. The reproducibility of AG, TL, and OSL measurements is about 5%. The fading in the first hour of storage in dark conditions at RT of TL signal of HPHT diamond is mainly associated to the emptying of the traps responsible for the 379-K TL peaks. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Correlation of Beam Electron and LED Signal Losses under Irradiation and Long-term Recovery of Lead Tungstate Crystals

    Batarin, V. A.; Butler, J.; Davidenko, A. M.; Derevschikov, A. A.; Goncharenko, Y. M.; Grishin, V. N.; Kachanov, V A.; Konstantinov, A. S.; Kravtsov, V. I.; Kubota, Y.; Lukanin, V. S.; Matulenko, Y. A.; Melnick, Y. M.; Meschanin, A. P.; Mikhalin, N. E.

    2005-01-01

    Radiation damage in lead tungstate crystals reduces their transparency. The calibration that relates the amount of light detected in such crystals to incident energy of photons or electrons is of paramount importance to maintaining the energy resolution the detection system. We report on tests of lead tungstate crystals, read out by photomultiplier tubes, exposed to irradiation by monoenergetic electron or pion beams. The beam electrons themselves were used to measure the scintillation light ...

  10. Effect of x-ray irradiation on thermal expansion of KCl single crystals

    The apparatus designed and fabricated earlier for accurate measurement of changes in length of solids through changes in capacitance of a condenser has been improved considerably to step up the accuracy of measurement to 10sup(-6) cm. Using this set-up, the thermal expansion of KCl single crystals before and after X-ray irradiation has been studied. It is found that the linear thermal expansion co-efficient (α) of X-ray irradiated KCl crystal increases to 47 x 10sup(-6)/deg C around room temperature, but attains the α value of unirradiated sample (39.8 x 10sup(-6)/deg C) in the temperature range 125deg C to 200deg C. From these data the number of vacancies created in KCl at room temperature by X-ray irradiation is calculated to be 9 x 10sup(17)/c.c. which is in fairly good agreement with the value 6 x 10sup(17)/c.c. calculated from optical absorption measurements taken on the same sample in the laboratory. (auth.)

  11. Defect recovery in electron-irradiated α-Zr single crystals: A positron annihilation study

    Five separate positron annihilation spectroscopy studies of electron irradiation damage and its thermally-activated recovery have been made on α-Zr single crystals. The samples were all cut from the same parent crystal; they had either (0001) or (10anti 10) plane surfaces. The nominal beam energy and fluence were 1.3 MeV and 2-4x1021 m-2, respectively, and the irradiation temperature was < 143 K. Isochronal recovery has been measured in terms of conventional Doppler-broadening peak (S) and wing (W) parameters, as well as a parameter R, which has the potential to be defect specific. Both S and W exhibit strong increases in the irradiation-induced defect signal in the range 250-300 K (associated with vacancy clustering); immediately thereafter, there is either a fairly rapid decline in the defect signal or, in the case of the samples with (10anti 10) surfaces, a relatively stable state to 350 K, followed by recovery. The origin of the apparent dependence of the shape of the recovery spectrum on the specimen orientation is, as yet, undetermined. (orig.)

  12. EPR study of gamma irradiated 2,5-di-tert-butyl-hydroquinone single crystals

    γ-irradiated single crystals of 2,5-di-tert-butyl-hydroquinone (DTBHQ) were investigated using the electron paramagnetic resonance (EPR) technique. The spectra of the crystals at different orientations in the magnetic field between temperatures of 120 and 450 K, were found to be temperature dependent. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystals of DTBHQ, we assumed that one or more paramagnetic species were produced, each having an unpaired electron delocalized in the phenyl ring. Pursuant to this assumption, four possible radicals were modeled using the B3LYP/6-31+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radicals using the B3LYP method and TZVP basis set. The calculated hyperfine-coupling constants were used as starting points for simulations. The experimental and simulated spectra for each of the three crystallographic axes were well matched for the modeled radical R4; we thus identified the hydroquinone anion radical as a paramagnetic species produced in DTBHQ. The experimental g-factor of the hydroquinone anion radical were found to be anisotropic with the average value giso=2.0096. The hyperfine coupling constants of the Ηα proton was found anisotropic with the average value (aH7α)iso=6.3G and Ηβ proton was found isotropic with the average value (aH8β)=3.5G.

  13. Characterization of high energy Xe ion irradiation effects in single crystal molybdenum with depth-resolved synchrotron microbeam diffraction

    Yun, Di; Miao, Yinbin; Xu, Ruqing; Mei, Zhigang; Mo, Kun; Mohamed, Walid; Ye, Bei; Pellin, Michael J.; Yacout, Abdellatif M.

    2016-04-01

    Microbeam X-ray diffraction experiments were conducted at beam line 34-ID of the Advanced Photon Source (APS) on fission fragment energy Xe heavy ion irradiated single crystal Molybdenum (Mo). Lattice strain measurements were obtained with a depth resolution of 0.7 μm, which is critical in resolving the peculiar heterogeneity of irradiation damage associated with heavy ion irradiation. Q-space diffraction peak shift measurements were correlated with lattice strain induced by the ion irradiations. Transmission electron microscopy (TEM) characterizations were performed on the as-irradiated materials as well. Nanometer sized Xe bubble microstructures were observed via TEM. Molecular Dynamics (MD) simulations were performed to help interpret the lattice strain measurement results from the experiment. This study showed that the irradiation effects by fission fragment energy Xe ion irradiations can be collaboratively understood with the depth resolved X-ray diffraction and TEM measurements under the assistance of MD simulations.

  14. The effect of doses, irradiation temperature, and doped impurities in the thermoluminescence response of NaCl crystals

    The interactions between ionizing gamma-radiation and two alkali halide single crystals, NaCl doped with Cd2+ (0.5 mol %) or Mn2+ (0.087 mol %), were analyzed for their possible use as low dose dosimeters. For that purpose, two irradiation temperatures (298 K and 77 K) and different doses at a fix dose rate were studied. The irradiated crystals were analyzed using their thermoluminescence and optical absorption properties. The F-centers formed in these crystals were measured as a function of the dose. The production of irradiation defects in the solid were correlated with the glow curve. Bleaching the F-centers produced a decrease in the peak of the glow curve, suggesting that F centers are intimately involved in the production of the thermoluminescence phenomenon. For the NaCl crystals doped with Cd, the area under the peak observed in the glow curves (associated to very deep traps) changes uniformly in the 1.15–13.8 Gy dose intervals, making this crystal a candidate for use as a dosimeter in low dose intervals. -- Highlights: ► The gamma irradiation of single crystals of NaCl doped with Cd or Mn were studied. ► The bleaching of the F-centers produced a decrease of the peak of the glow curve. ► Crystals of NaCl:Cd can be use as a dosimeter at low radiation doses

  15. Multi-cycling nanoindentation in MgO single crystals before and after ion irradiation

    The paper presents a nanoindentation study of MgO single crystals before and after ion irradiation up to a fluence of 1020 Ar+ m-2. It is confirmed that crystalline MgO is a brittle material of comparatively high nanohardness, ranging from H = 12.5 to 14.5 GPa depending on surface orientation. The plastic deformation is based on a dislocation glide with formation of slip bands giving rise to piling up around the indent which is strongly related to the sample crystallography. Repeated loading-unloading cycles (multi-cycling) revealed the appearance of hysteresis loops that are related to nanofracturing. Irradiation with 100 keV Ar+ ions resulted in a reproducible hardness increase to a value of H = 19 GPa independent of surface orientation. The indentation modulus E = 285 GPa remained unaffected by ion irradiation. Furthermore, no hysteresis loop in the force-displacement curve was formed with multi-cycling after implantation. This is explained in terms of point defect assisted plasticity: defect pinning will decrease the dislocation mobility and hence increase the hardness and also cause the sample to become less brittle resulting in a large decrease in nanocrack formations. In contrast to the dislocation glide, the point defect contribution to plastic deformation is almost orientation independent. This picture is supported by the orientation independent hardness as well as by the observation that ion irradiated samples exhibit a reduction in, and more homogeneously distributed, piling up around the indent

  16. Proton irradiation effects on critical current of bulk single-crystal superconducting YBCO wire

    The authors have investigated the effects of 10 MeV proton irradiation on the magnetization M and critical current density Jc of bulk single-crystal YBa2Cu3O7-δ (YBCO) superconducting thick wire filaments produced through laser-heated floating zone (LHFZ) technique. M and Jc were determined both along the length and perpendicular to the length of the wire. Radiation-induced enhancement of Jc along the length of the wire was observed while there was a small decrease in Jc perpendicular to its length. Jc values along the length of the wire up to ∼1.4 x 105 A/cm2 at 77K and ∼1.3 x 106 A/cm2 at 30K and in applied magnetic field H = 1 T were observed in the irradiated samples. In the unirradiated sample, the difference in magnetization ΔM at a given field in the magnetic hysteresis loop for increasing and decreasing field applied perpendicular to the sample length was observed to depend on the orientation of the sample about its axis. This indicates anisotropy in Jc along the sample length. This anisotropy increased on irradiation relative to the direction of irradiation. They believe that these Jc values along the length are amongst the highest published Jc values for bulk high temperature superconductor (HTS) thick wire filament

  17. Influence of crystal orientation on hardness and nanoindentation deformation in ion-irradiated stainless steels

    Miura, Terumitsu; Fujii, Katsuhiko; Fukuya, Koji; Takashima, Keisuke

    2011-10-01

    The influence of crystal orientation on hardness and the range of plastic deformation caused by nanoindentation was investigated in a solution annealed type 316 stainless steel irradiated with Fe 2+ ions. The hardness was a function of grain orientation and was correlated with the Taylor factor averaged over three normal directions of the contact surface of the Berkovich indenter. The transmission electron microscope observations of the deformation microstructure under the indentations showed that the range of plastic deformation reached up to 10 times the indent depth for unirradiated material and depended on the orientation relation between the contact surface of the indenter and the slip directions. The range of plastic deformation decreased as the damage structure developed in ion irradiation.

  18. Influence of crystal orientation on hardness and nanoindentation deformation in ion-irradiated stainless steels

    Miura, Terumitsu, E-mail: miura@inss.co.jp [Institute of Nuclear Safety System, Incorporated, 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Fujii, Katsuhiko, E-mail: fujiik@inss.co.jp [Institute of Nuclear Safety System, Incorporated, 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Fukuya, Koji, E-mail: fukuya@inss.co.jp [Institute of Nuclear Safety System, Incorporated, 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Takashima, Keisuke, E-mail: maestro@mech.fukui-u.ac.jp [Graduate School of Nuclear Power and Energy Safety Engineering, University of Fukui, 910-8507, 3-9-1 Bunkyo, Fukui (Japan)

    2011-10-01

    The influence of crystal orientation on hardness and the range of plastic deformation caused by nanoindentation was investigated in a solution annealed type 316 stainless steel irradiated with Fe{sup 2+} ions. The hardness was a function of grain orientation and was correlated with the Taylor factor averaged over three normal directions of the contact surface of the Berkovich indenter. The transmission electron microscope observations of the deformation microstructure under the indentations showed that the range of plastic deformation reached up to 10 times the indent depth for unirradiated material and depended on the orientation relation between the contact surface of the indenter and the slip directions. The range of plastic deformation decreased as the damage structure developed in ion irradiation.

  19. Critical currents in proton irradiated YBa2Cu3O7-δ crystals

    A large enhancement in the critical current of YBaCuO crystals in magnetic field is observed after irradiation with 3 MeV protons. Critical current densities with values up to 2 x 105 A/cm2 at 77 K and 1 T are observed. TEM studies show the presence of isolated clusters of defects after irradiation; however, an analysis of the critical current scaling indicates that these clusters are not the dominant pinning sites. The dose dependence of the current density suggests that the pinning is dominated by the randomly distributed point defects generated by the protons and can be described by a collective pinning model in the amorphous limit. 24 refs., 7 figs

  20. Influence of crystal orientation on hardness and nanoindentation deformation in ion-irradiated stainless steels

    The influence of crystal orientation on hardness and the range of plastic deformation caused by nanoindentation was investigated in a solution annealed type 316 stainless steel irradiated with Fe2+ ions. The hardness was a function of grain orientation and was correlated with the Taylor factor averaged over three normal directions of the contact surface of the Berkovich indenter. The transmission electron microscope observations of the deformation microstructure under the indentations showed that the range of plastic deformation reached up to 10 times the indent depth for unirradiated material and depended on the orientation relation between the contact surface of the indenter and the slip directions. The range of plastic deformation decreased as the damage structure developed in ion irradiation.

  1. Intensification of electroluminescence of ZnSe(Te,O) crystals after gamma-irradiation

    Full text: Wide-gap A2B6 semiconductors are of special interest within eyeshot of energy-saving, on the base of which light sources are produced. Excitation voltage for injection electro luminescence (EL) corresponds to a transition potential barrier height, and wavelength determines the radiative transition energy and a recombination level position. The problem is in increasing the EL excitation efficiency, in particular the way of lowering the working voltage. The aim of the present work is experimental researches of possible amendment of EL characteristics of wide-gap ZnSe(Te,O) single crystals by influence of ionizing gamma-radiation on the electrical and optical active centers, and also exposure of possibility for creation of light emitting structures. We studied ZnSe crystals grown with Bridgman method at the Research Institute for Single Crystals (Kharkov, Ukraine). Diffusion doping with Te was used for creation of p-n transition in ZnSe crystals, that resulted in additional generation of Zn vacancies, treatment in oxidizing environment caused formation of extra Zn interstitials. Dominating evaporation of Zn, which is stipulated by a higher mobility of Zni, leads to the increase of defect concentration of VZn type, this process is vividly expressed in the crystals doped with Te that may be explained by the formation of stable VZnTeSeZni associates. A few samples of each series were irradiated with≅ 1.25 MeV gamma-rays of 60Co radioisotope source at the dose power of 10 Gy/s to the dose of 106 Gy at 300 K and compared with the non-irradiated reference samples. Spectra of EL were measured in the wave range of 200-900 nm at 300 K. A constant voltage in the range of 7-80 V was applied in straight and inverse direction for exposing hysteresis in the EL voltage-brightness dependences. The EL spectra include a wide band with the maximum at 600 nm. For the untreated samples the threshold voltage was 70-80 V, when the EL intensity began growing sharply, depending

  2. Study of the vortex patterns in Bi-2212 single crystals irradiated with heavy ions

    In this work, we compare observations of vortices in Bi-2212 single crystals, before and after the creation of defects by irradiation. The decorated flux line patterns have been characterized using scanning electron microscopy and computer image analysis. In the decorated flux line networks, the degree of disorder and its nature have been investigated by several methods: determination of radial distribution functions, of translational and orientational correlation functions according to the theory of Nelson et al. (3) and calculation of elastic energy terms. (orig.)

  3. Intrinsic Defects in UV-irradiated MgO Single Crystal Detected by Thermoluminescence

    D. Kadri

    2005-01-01

    Full Text Available The Thermoluminescence (TL properties of an MgO single crystal sample were studied from 170 to 500°K after UV-irradiation (4.8 eV for 10 min. The aim of this study was to determine the MgO intrinsic defects centers and in particular the F, F+, F2 and Fcat centers, these defects are localized in the 270-570 nm region, their TL signal was characterized by four emission bands detected at wavelengths 540, 380, 350 and 290 nm, respectively.

  4. Intrinsic Defects in UV-irradiated MgO Single Crystal Detected by Thermoluminescence

    D. Kadri; A. Mokeddem; Hamzaoui, S.

    2005-01-01

    The Thermoluminescence (TL) properties of an MgO single crystal sample were studied from 170 to 500°K after UV-irradiation (4.8 eV for 10 min). The aim of this study was to determine the MgO intrinsic defects centers and in particular the F, F+, F2 and Fcat centers, these defects are localized in the 270-570 nm region, their TL signal was characterized by four emission bands detected at wavelengths 540, 380, 350 and 290 nm, respectively.

  5. Extrinsic Defects in UV-irradiated MgO Single Crystal Detected by Thermoluminescence

    D. Kadri; S. Hiadsi; Hamzaoui, S.

    2007-01-01

    MgO single crystal sample previously irradiated with ultraviolet light (UV) 4.8 eV has been studied using thermoluminescence (TL) technique in the temperature range 170-500�K, in this study, we were mainly interested in the extrinsic defects (impurities), these impurities are localised in four distinct regions, Cr3+ is assigned to the first region 680-760 nm, in the second region 465-500 nm we find Ni2+, Fe3+ is localised in the third region 310-375 nm and lastly the Ca2+ and K+ have been fou...

  6. Extrinsic Defects in UV-irradiated MgO Single Crystal Detected by Thermoluminescence

    D. Kadri

    2007-01-01

    Full Text Available MgO single crystal sample previously irradiated with ultraviolet light (UV 4.8 eV has been studied using thermoluminescence (TL technique in the temperature range 170-500�K, in this study, we were mainly interested in the extrinsic defects (impurities, these impurities are localised in four distinct regions, Cr3+ is assigned to the first region 680-760 nm, in the second region 465-500 nm we find Ni2+, Fe3+ is localised in the third region 310-375 nm and lastly the Ca2+ and K+ have been found to emit in the 180-260 nm region.

  7. Paramagnetic centres in X-irradiated LiNaSO4 single crystals

    The EPR and optical absorption spectra of paramagnetic centers produced by X-irradiation in LiNaSO4 single crystals were investigated. 7 EPR lines are observed at room temperature and 6 more lines at LNT. The angular dependences of line positions at LNT are studied and the principal g-factor values are defined. The comparison with published data permitted to assign six the most anisotropic lines to ion-radical SO4- with different orientations in the lattice; two lines to ion-radical SO2-; slightly anisotropic doublet line to O3- ozonide ion; isotropic line with g = 2.0045 to ion radical SO3-. (author)

  8. Accumulation of color centers in lithium fluoride crystals under irradiation with swift lead projectiles

    Lithium fluoride crystals were irradiated with lead ions of different energies, having the electronic energy loss of 10–20 keV/nm. Accumulation of F centers with fluence was studied by absorption UV–VIS spectroscopy. It was found that the average F-center concentration is mainly determined by the average absorbed energy density with a weak decrease above 1023 eV/cm3. A defect accumulation model, taking into account the recombination processes, is proposed for a seamless description of the F-center concentration fluence dependences for various projectiles and energy losses

  9. Accumulation of color centers in lithium fluoride crystals under irradiation with swift lead projectiles

    Benhacine, H. [LRPCSI, University of 20 Août 1955 Skikda, Route El-Hadaeik, 21000 Skikda (Algeria); Département de physique Université Constantine 1, Route Ain El-Bey 25000 (Algeria); Sorokin, M.V., E-mail: m40@lab2.ru [National Research Centre ‘Kurchatov Institute’, Kurchatov Square 1, 123182 Moscow (Russian Federation); Schwartz, K. [GSI Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany); Meftah, A. [LRPCSI, University of 20 Août 1955 Skikda, Route El-Hadaeik, 21000 Skikda (Algeria)

    2015-09-15

    Lithium fluoride crystals were irradiated with lead ions of different energies, having the electronic energy loss of 10–20 keV/nm. Accumulation of F centers with fluence was studied by absorption UV–VIS spectroscopy. It was found that the average F-center concentration is mainly determined by the average absorbed energy density with a weak decrease above 10{sup 23} eV/cm{sup 3}. A defect accumulation model, taking into account the recombination processes, is proposed for a seamless description of the F-center concentration fluence dependences for various projectiles and energy losses.

  10. Fluorescence Properties of Colour Centres Produced by Ultrashort Laser Irradiation in LiF Crystals

    Samad, R. E.; Courrol, L. C.; Gomes, L.; Ranieri, I. M.; Baldochi, S. L.; de Freitas, A. Z.; Vieira, N. D., Jr.

    2010-11-01

    LiF is a nonhygroscopic alkali halide crystal which possesses good optical and physical properties, and can host different species of colour centres at room temperature. Colour centres in LiF present broad absorption and emission bands in the near UV, visible and near IR regions of the spectrum. In this paper we study spectroscopic properties of colour centres produced in LiF by ultrashort laser pulses. The absorption and emission properties of these materials were measured showing that during the irradiation F, F2, F2+, F3+ and F2- colour centres were created in the crystals. A colour centres formation dose-like curve as a function of the ultrashort pulse energy was determined using fluorescence spectroscopy.

  11. Microwave emission by nonlinear crystals irradiated with a high-intensity, mode-locked laser

    Borghesani, A. F.; Braggio, C.; Guarise, M.

    2016-06-01

    We report on the experimental investigation of the efficiency of some nonlinear crystals to generate microwave (RF) radiation as a result of optical rectification (OR) when irradiated with intense pulse trains delivered by a mode-locked laser at 1064 nm. We have investigated lithium triborate (LBO), lithium niobate (LiNbO3), zinc selenide (ZnSe), and also potassium titanyl orthophosphate (KTP) for comparison with previous measurements. The results are in good agreement with the theoretical predictions based on the form of the second-order nonlinear susceptibility tensor. For some crystals we investigated also the second harmonic generation (SHG) to cross check the theoretical model. We confirm the theoretical prediction that OR leads to the production of higher order RF harmonics that are overtones of the laser repetition rate.

  12. Rise and fall of ferromagnetism in O-irradiated Al2O3 single crystals

    In dilute magnetic semiconductors studies, sapphire was usually used as non-magnetic substrate for films. We observed weak ferromagnetic component in Al2O3 single crystal substrate, and excluded the possibility of ferromagnetic contaminations carefully by inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy. The ferromagnetism rise and fall during the process of annealing-oxygen irradiation-annealing of the sapphire. The ferromagnetic changes are consistent with Al-vacancy related defects detected by positron annihilation spectroscopy. With first-principle calculations, we confirm that Al-vacancy can introduce magnetic moment for 3 μB in Al2O3 crystal and form stable VAl-VAl ferromagnetic coupling at room temperature

  13. Microwave emission by nonlinear crystals irradiated with a high-intensity, mode-locked laser

    Borghesani, A F; Guarise, M

    2016-01-01

    We report on the experimental investigation of the efficiency of some nonlinear crystals to generate microwave (RF) radiation as a result of optical rectification (OR) when irradiated with intense pulse trains delivered by a mode-locked laser at $1064\\,$nm. We have investigated lithium triborate (LBO), lithium niobate (LiNbO$_3$), zinc selenide (ZnSe), and also potassium titanyl orthophosphate (KTP) for comparison with previous measurements. The results are in good agreement with the theoretical predictions based on the form of the second-order nonlinear susceptibility tensor. For some crystals we investigated also the second harmonic generation (SHG) to cross check the theoretical model. We confirm the theoretical prediction that OR leads to the production of higher order RF harmonics that are overtones of the laser repetition rate.

  14. Effects of gamma ray irradiation on the struvite crystallization of livestock wastewater

    Yoo, Byeong Hak; Jo, Seong Hui; Lee, Myun Joo; Kim, Tak Hyun [Korea Atomic Energy Research Institute, Jeongeup (Korea, Republic of)

    2010-12-15

    The struvite crystallization was applied to remove NH{sub 4}{sup +} in livestock wastewater. The ammonium ions can be very toxic to the aquatic creatures. In this experiments, the livestock wastewater from Gongju livestock wastewater treatment plant was used. The behaviors of various parameters such as pH, mole ratio of Mg{sup 2+} : NH{sub 4}{sup +}: PO{sub 4}{sup 3-} and reaction temperature for struvite crystallization of livestock wastewater and the effect of gamma ray irradiation were evaluated. As results, for the pH variation, the NH{sub 4}{sup +} removal efficiency showed the highest, 88%, at pH 9 {approx} 9.25. The removal efficiency of NH{sub 4}{sup +}, Mg{sup 2+} and PO{sub 4}{sup 3-} was showed highest when same molar ratio of Mg{sup 2+} and PO{sub 4}{sup 3-} were applied. The NH{sub 4}{sup +} removal efficiency showed 82% at 7 .deg. C, and 90% at 30 .deg. C, with temperature. When the wastewater was irradiated with 20 kGy of gamma ray, NH{sub 4}{sup +} was removed as much as 83%.

  15. ESR of trapped centers in γ irradiated silver chlorates single crystals

    The paramagnetic centers O-3, ClO2, and (ClO2--Cl)- have been identified in irradiated AgClO3 single crystals by X and Q band ESR experiments at room temperatures and by the optical absorption bands at 480 and 360 nm, characteristic of the first two centers, respectively. The ESR spectrum and its angular dependence show that the first two centers have two magnetically inequivalent sites per unit cell. The third center was clearly observed only at certain orientations. The data for ClO2 show that the principal directions of the g and A tensors do not coincide; the two magnetically inequivalent sites have similar principal values of the g and A tensors related by a 900 rotation about the tetragonal crystal axis of symmetry, and can therefore be assumed to be chemically equivalent. It is found that the ClO2 center is formed substitutionally in the ClO-3 ion position, but that the ozonide O-3 is not. The thermal annealing of the γ irradiated AgClO3 has revealed an increase in the concentration of the O-3 radical that seems to be connected with the simultaneous destruction of the ClO2 center

  16. 10CFR61 irradiated component characterization at Crystal River Unit 3

    Since the enactment of 10CFR61, nuclear utilities have experienced difficulty in obtaining representative samples of irradiated hardware. Problems stem from the very high dose rates of irradiated hardware (1,000 - 50,000 R/hr), which necessitates the execution of a sampling procedure underwater in fuel storage pools. FPC Crystal River unit 3 approached the problem by utilization of direct assay technology, which quantifies the 10CFR61 radionuclides that are either gamma-emitting or neutron-emitting (TRU) radionuclides. The direct underwater assay of in-core instrumentation and SSHT bolts was performed by using direct assay equipment which was submerged in the fuel pool. This work was done in conjunction with an EPRI technology demonstration project which evaluated the current technologies and techniques used for direct measurement of radionuclides in waste packages. Additionally, the direct assay equipment characterized 10CFR61 radionuclides in waste packages containing CVCS filters, primary resins, radwaste resin, and DAW. This paper presents the results of the direct assay techniques demonstrated at Crystal River unit 3

  17. γ-irradiation effect on the optical absorption in band-edge region of dicalcium lead propionate single crystals

    Crystals of Dicalcium lead propionate (DLP) irradiated with different doses of gamma radiation were used to investigate gamma radiation effect on some optical parameters. The absorption coefficient of unirradiated and irradiated DLP crystals were calculated. Values of the allowed indirect optical energy gap (Ε) of DLP were calculated as a function of gamma-dose. decreases from 4.12 eV to 3.94 eV with increasing gamma-doses from 0 up to 10 kGy. This decrease was attributed to point defects created in DLP crystals during gamma-irradiation. The exponential dependence of the absorption coefficient as a function of the incident photon energy suggests that the Urbach rule is obeyed, and indicated the formation of a band tail. It was found that the band tail exhibits the opposite Ε behaviour

  18. Effects of annealing treatment and gamma irradiation on the absorption and fluorescence spectra of Cr:GSGG laser crystal

    Sun, D. L.; Luo, J. Q.; Xiao, J. Z.; Zhang, Q. L.; Jiang, H. H.; Yin, S. T.; Wang, Y. F.; Ge, X. W.

    2008-09-01

    The influence of annealing treatments and gamma-ray irradiation on the absorption and fluorescence spectra of Cr:GSGG crystals grown by the Czochralski method has been investigated. Two absorption bands located near 686 nm and 1050 nm were weakened markedly after the crystal was re-annealed in H2 atmosphere, which is due to the Cr4+ ions being de-oxidized into Cr3+ ions. The other two weak additional absorption bands induced by gamma-ray irradiation appearing near 310 nm and 480 nm are ascribed to the Fe2+ ions and F-type color centers, respectively. In particular, the gamma-ray irradiation with a dose of 100 Mrad has an effect of improving slightly the luminescence properties of Cr:GSGG crystals. The improvement mechanism is analyzed and discussed.

  19. Electrical and structural properties of InSb crystals irradiated with reactor neutrons

    The structural transformations in InSb crystals irradiated with fast neutrons (E>0.1MeV) and the full spectrum of reactor neutrons with the ratio of the slow to fast neutron fluxes φsn/φfn∼1 are studied. Two ranges on the dose dependence can be selected according to the influence of fast neutron irradiation on the lattice parameter. Increase of the lattice parameter is not observed at the low flux (Ffn17cm-2). As it follows from the X-ray diffuse scattering analysis, vacancy-type clusters dissociate in this range, and the number of small interstitial-type clusters simultaneously increases in this range. At Ffn>2.5x1017cm-2 the lattice parameter linearly increases with flux. A great number of small interstitial- and vacancy-type clusters, which can trap Sn impurity atoms, are formed. The heat treatment of irradiated samples up to 400oC completely recovers the values of the lattice parameter

  20. EPR study of gamma-irradiated amphi-phenylglyoxime single crystals

    Gamma-irradiated single crystals of Amphi-phenylglyoxime (APGO) were investigated using electron paramagnetic resonance (EPR) at different orientations in a magnetic field at room temperature (298 K). Considering the chemical structure and the experimental spectra of the irradiated single-crystals of APGO, we assumed that two different paramagnetic species, labeled as R* and R**, are either two iminoxy radicals formed by the abstraction of a H atom from different oxime branches or are different conformations of an iminoxy radical. Pursuant to this assumption, RA- and RB-type iminoxy radicals were modeled by the abstraction of H atoms from different oxime branches, and conformational analysis of these modeled radicals was performed using the semi-empirical AM1 and B3LYP/6-31+G(d,p) methods. EPR parameters were calculated for the modeled radicals using the B3LYP method and EPR-III basis set. Theoretically calculated values of the most stable conformers (RA-1 and RB-1) of the modeled radicals are in good agreement with the experimental EPR parameters determined from the spectra (differences in isotropic hyperfine coupling constant values * and R** radicals in the single crystal of amphi-phenylglyoxime are the most stable conformers of RA- and RB-type modeled iminoxy radicals, respectively. The experimental g factors and hyperfine coupling constants were found to be anisotropic, with average values of g=2.0052, A(14N)=29.50 G, A(1H)=25.30 G for R*, and g=2.0057, A(14N)=34.50 G for R**.

  1. Vortex dynamics in a ring-like irradiated Bi2Sr2CaCu2O8 crystal

    A Bi2Sr2CaCu2O8 crystal selectively irradiated near the edges is studied using a Hall-sensor array. Vortices penetrating into the central Jc = 0 region are open-quotes focusedclose quotes in the center of the sample on increasing the applied field. In decreasing field, vortices leave the center and a large vortex accumulation is observed on the inner rim of the irradiated region. Spatially resolved magnetization measurements confirm the developed theoretical model

  2. Spectrum of electron states and parameters of Si crystal with oxygen-silicon precipitates, irradiated by fast neutron

    The paper deals with properties of oxygen reach Si crystal irradiated with fast reactor neutrons. The spectra of electron states and electrical properties were studied by the method of modulation spectroscopy of light electrical reflection. From experimental data influence of irradiation and annealing on energetic position of quantum level (60 and 85 meV) and the width of surface quantum well (3 and 2 nm, according) were obtained

  3. Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation

    Sun, Xinxing; Ehrhardt, Martin; Lotnyk, Andriy; Lorenz, Pierre; Thelander, Erik; Gerlach, Jürgen W.; Smausz, Tomi; Decker, Ulrich; Rauschenbach, Bernd

    2016-06-01

    The amorphous to crystalline phase transformation of Ge2Sb2Te5 (GST) films by UV nanosecond (ns) and femtosecond (fs) single laser pulse irradiation at the same wavelength is compared. Detailed structural information about the phase transformation is collected by x-ray diffraction and high resolution transmission electron microscopy (TEM). The threshold fluences to induce crystallization are determined for both pulse lengths. A large difference between ns and fs pulse irradiation was found regarding the grain size distribution and morphology of the crystallized films. For fs single pulse irradiated GST thin films, columnar grains with a diameter of 20 to 60 nm were obtained as evidenced by cross-sectional TEM analysis. The local atomic arrangement was investigated by high-resolution Cs-corrected scanning TEM. Neither tetrahedral nor off-octahedral positions of Ge-atoms could be observed in the largely defect-free grains. A high optical reflectivity contrast (~25%) between amorphous and completely crystallized GST films was achieved by fs laser irradiation induced at fluences between 13 and 16 mJ/cm2 and by ns laser irradiation induced at fluences between 67 and 130 mJ/cm2. Finally, the fluence dependent increase of the reflectivity is discussed in terms of each photon involved into the crystallization process for ns and fs pulses, respectively.

  4. Structural changes in the crystal-amorphous interface of isotactic polypropylene film induced by annealing and γ-irradiation

    Annealing and radiation effects on the microstructures of isotactic polypropylenes, homopolymer and ethylene (<2.3 wt%) incorporated random copolymers, in the solid state were studied to get mechanistic insight into the modification and degradation of mechanical properties. The growth of helical conformation of isotactic chains in the crystal-amorphous interface was induced to greater extent by γ-irradiation, while the transition from smectic to monoclinic modifications in the crystal phase occurred simultaneously by annealing. The yield stress of the polypropylene films increased with the increased content of helical conformation as the result of annealing and/or γ-irradiation. (author)

  5. Crystal growth in EPDM by chemi-crystallisation as a function of the neutron irradiation dose and flux level

    Neutron irradiation at room temperature were performed on EPDM (ethylene-propylene-diene monomer) in two different nuclear reactors at different fluxes. The effect of the irradiation on the chain arrangement in the polymer, as a function of the dose is discussed. Different crystal concentrations and crystal shapes, developed by chemi-crystallisation, are obtained depending on the neutron dose. In addition the radiation damage degree in the polymer depends both on the dose and the flux level. Dynamical mechanical analysis, swelling studies, X-ray diffraction, differential thermal analysis and infrared studies were employed as experimental techniques

  6. Radiation-induced transformations of luminescence centers in anion-defective alumina crystals under high-dose irradiations

    Highlights: •Alumina crystals (Al2O3:C) were studied after exposures with doses up to 106 Gy. •PL and PLE spectra of alumina crystals were measured after exposure to high-dose. •New wide emission band was found in the PL spectra of irradiated crystals. •High dose irradiations give rise to charged aggregate F2-type centers. •Aggregate centers are responsible for the change in PL spectra and TL yield. -- Abstract: Luminescent spectroscopy is used to show formation of new trapping centers of charge carriers in anion-defective alumina crystals at radiation-induced transformations of F and F+-centers created by oxygen vacancies when exposed to high-dose gamma-radiation. A new wide band in the range 440–700 nm was registered in the photoluminescence spectrum at excitations with UV photons. High-dose irradiation of the crystals leads to appearance of F2-type aggregate centers in different charged states. These centers are additional traps of charge carriers. The new traps increase a luminescent yield at high-dose irradiation with gamma-rays and an electron beam

  7. Synthesis of TiO2 nanoscale rods with MHz femtosecond laser irradiation of single crystal surface and characterisation

    M. Sivakumar

    2011-06-01

    Full Text Available Growth of nanoscale rods on single crystal rutile TiO2 surface irradiated by MHz pulse repetition rate femtosecond laser in nitrogen environment without a catalyst or template is reported. The rods are of 100 nm in width to 1 micron length. Microraman analysis of the laser irradiated surface shows only a decrease in the intensity of active modes as compared to untreated surface. The growth of TiO2 nanorods can be explained by a method combining nanoparticles formation due to expulsion of molten material from laser irradiated spot and their subsequent growth by vapor-liquid-solid process.

  8. Effect of irradiation temperature on crystallization of {alpha}-Fe induced by He irradiations in Fe{sub 80}B{sub 20} amorphous alloy

    San-noo, Toshimasa; Toriyama, Tamotsu; Wakabayashi, Hidehiko; Iijima, Hiroshi [Musashi Inst. of Tech., Tokyo (Japan); Hayashi, Nobuyuki; Sakamoto, Isao

    1997-03-01

    Since amorphous alloys are generally highly resistant to irradiation and their critical radiation dose is an order of magnitude higher for Fe-B amorphous alloy than Mo-methods, these alloys are expected to become applicable as for fusion reactor materials. The authors investigated {alpha}-Fe crystallization in an amorphous alloy, Fe{sub 80}B{sub 20} using internal conversion electron Moessbauer spectroscopy. The amount of {alpha}-Fe component was found to increase by raising the He-irradiation dose. The target part was modified to enable He ion radiation at a lower temperature (below 400 K) by cooling with Peltier element. Fe{sub 80}B{sub 20} amorphous alloy was cooled to keep the temperature at 300 K and exposed to 40 keV He ion at 1-3 x 10{sup 8} ions/cm{sup 2}. The amount of {alpha}-Fe crystal in each sample was determined. The crystal formation was not observed for He ion radiation below 2 x 10{sup 18} ions/cm{sup 2}, but that at 3 x 10{sup 8} ions/ cm{sup 2} produced a new phase ({delta} +0.40 mm/sec, {Delta} = 0.89 mm/sec). The decrease in the radiation temperature from 430 to 300 K resulted to extremely repress the production of {alpha}-Fe crystal, suggesting that the crystallization induced by He-radiation cascade is highly depending on the radiation temperature. (M.N.)

  9. Thermally and optically stimulated processes in X-irradiated scheelite type crystals

    In tungstate and molybdate crystals having scheelite structure various (intrinsic and extrinsic) hole and electron centres are created by X-irradiation at liquid nitrogen temperature. Several of these centres have been thoroughly investigated by electron paramagnetic resonance (EPR) measurements. Their thermal decay and optical bleaching, resp., can be related to glow peaks of thermoluminescence and thermally resp. optically stimulated conductivity as well as characteristic changes in optical absorption. For the case of CaWO4 doped with lead some of these centres and typical transport processes are discussed. From analysis of EPR data, polarization and spectral composition of thermoluminescence, optical absorption, spectral response of optically stimulated conductivity and re-excited thermoluminescence detailed information about electronic structure can be obtained

  10. Zenithal alignment of liquid crystal on homeotropic polyimide film irradiated by ion beam

    Choi, Yoonseuk; Yoon, Tae-Hoon; Kwon, Jin Hyuk; Yi, Jonghoon; Gwag, Jin Seog

    2012-01-01

    We investigate the pretilt characteristics of a nematic liquid crystal [LC] in terms of ion beam exposure conditions on the homeotropic polyimide alignment layer. The pretilt angle of LCs in the case of high-energy ion beam treatment was decreased considerably almost the same to that of the homogenous alignment layer though we used homeotropic polyimide film at first. Increasing irradiating energy, we could control the pretilt from 90° to 1° with several steps. We believe that this is because the side chain with hydrophobicity in the used polyimide is broken by ion beam exposure. To confirm it, contact angle measurement was carried out. With this result, we can easily control the LC pretilt in the pixel with appropriate exposure conditions which is critical to achieve excellent electrooptic characteristics and good image quality.

  11. FLUKA studies of hadron-irradiated scintillating crystals for calorimetry at the High-Luminosity LHC

    Quittnat, Milena Eleonore

    2015-01-01

    Calorimetry at the High-Luminosity LHC (HL-LHC) will be performed in a harsh radiation environment with high hadron fluences. The upgraded CMS electromagnetic calorimeter design and suitable scintillating materials are a focus of current research. In this paper, first results using the Monte Carlo simulation program FLUKA are compared to measurements performed with proton-irradiated LYSO, YSO and cerium fluoride crystals. Based on these results, an extrapolation to the behavior of an electromagnetic sampling calorimeter, using one of the inorganic scintillators above as an active medium, is performed for the upgraded CMS experiment at the HL-LHC. Characteristic parameters such as the induced ambient dose, fluence spectra for different particle types and the residual nuclei are studied, and the suitability of these materials for a future calorimeter is surveyed. Particular attention is given to the creation of isotopes in an LYSO-tungsten calorimeter that might contribute a prohibitive background to the measu...

  12. On stability of spatial distributions of crystal structure defects in irradiated high burnup UO2 fuel

    Conditions of Kinoshita instability development of point defects and dislocation spatial distributions in the crystal structure of UO2 fuel are studied. As a result of the instability development, spatially non-uniform regions with increased dislocation density are formed. Closed-form expressions of instability increment and spatial scale are derived. Parameters of the instability for irradiation conditions of high burnup UO2 fuel are obtained by means of numerical simulation. Instability development time is shown to be inversely proportional to fission rate and it increases as dislocation density decreases. Calculated values of instability spatial scale and increment are in accordance with the size of fine grains and their formation rate in the peripheral zones of high burnup LWR fuel pellets

  13. ESR study of the CF3xxxF radical in irradiated trifluoroacetamide single crystals

    ESR and deuteration studies of x-irradiated trifluroacetamide crystals at 77 0K show that the CF3(A) radical initially formed interacts with a fluorine nucleus on a neighboring molecule, resulting in an additional fluorine doublet of A/sub z/=10 G, A/sub y/0K and is irreversibly replaced by the ESR spectrum of CF3(B) that is stable to 200 0K. Based on an INDO calculation, the formation of CF3(A) occurs when the crystallographic intermolecular FxxxCF3 distance in the parent compound decreases from 3.77 to 2.4 A upon radical formation at 77 0K. Following the formation of CF3(A), the FxxxCF3 distance increases with time or temperature to approximately 3.0 A

  14. Influence of dislocation structure and impurities on void lattice formation in crystals under irradiation

    The void ordering under irradiation in simple cubic, bcc, fcc and hcp-crystals is considered within the framework of the dislocation model of void lattice formation based upon the absorption of perfect interstitial loops by voids. The ordering criterion is derived taking into account not only perfect loopd but Frank sessile loops and straight dislocations as well. Analytical dependence of void lattice parameters on the concentration of the loop nucleation sites is derived. Impurities are shown to stimulate or prevent void ordering depending on their influence on the loop nature. Finally, a mechanism of loop-punching from submicroscopic overpressurized gas bubbles is considered as a possible source of perfect loops which could induce the swelling saturation and void ordering in fcc metals with low stacking fault energy. 15 refs.; 3 figs

  15. FLUKA studies of hadron-irradiated scintillating crystals for calorimetry at the High-Luminosity LHC

    Calorimetry at the High-Luminosity LHC (HL-LHC) will be performed in a harsh radiation environment with high hadron fluences. The upgraded CMS electromagnetic calorimeter design and suitable scintillating materials are a focus of current research. In this paper, first results using the Monte Carlo simulation program FLUKA are compared to measurements performed with proton-irradiated LYSO, YSO and cerium fluoride crystals. Based on these results, an extrapolation to the behavior of an electromagnetic sampling calorimeter, using one of the inorganic scintillators above as an active medium, is performed for the upgraded CMS experiment at the HL-LHC. Characteristic parameters such as the induced ambient dose, fluence spectra for different particle types and the residual nuclei are studied, and the suitability of these materials for a future calorimeter is surveyed. Particular attention is given to the creation of isotopes in an LYSO-tungsten calorimeter that might contribute a prohibitive background to the measured signal

  16. Enrichment of InP crystal surface by indium as a result of selective material evaporation under pulsed laser irradiation

    Laser irradiation flux threshold density under which local melting-like changes on InP, GaAs and InAs crystals surface were established. Conclusion was made that changes are due to compounds decomposition under beam heating of surface to temperatures lower than compound melting point

  17. Irradiation damage in Gd2Ti2O7 single crystals: Ballistic versus ionization processes

    The structural transformations induced in Gd2Ti2O7 single crystals irradiated at high energies (870-MeV Xe), where ionization processes (electronic stopping) dominate, and at low energies (4-MeV Au), where ballistic processes (nuclear stopping) dominate, have been studied via the combination of Rutherford backscattering spectrometry and channeling (RBS/C), Raman spectroscopy, and transmission electron microscopy (TEM) experiments. At high energy, amorphization occurs directly in individual ion tracks from the extreme electronic-energy deposition, and full amorphization results from the overlapping of these tracks as described by a direct impact model. The track diameters lie in the range 6-9 nm. At low energy, amorphization occurs via indirect processes, driven by ballistic nuclear energy deposition from the ions, that is accounted for in the framework of both direct-impact/defect-stimulated and multi-step damage accumulation models. The ion fluence for total amorphization of the irradiated layer is much higher at low energy (0.5 ion nm-2) than at high energy (0.05 ion nm-2), consistent with the nuclear stopping at low energy (5.2 keV/nm) compared to the electronic stopping at high energy (29 keV/nm).

  18. Irradiation-induced voids in alumina single crystal studied by positron annihilation

    Angular correlation of annihilation radiation (ACAR) has been measured on α-alumina single crystals irradiated with fast neutrons to a dose of 3x1024 n/m2 at about 470 K. After post-irradiation annealing above 900 K, remarkable narrowing in ACAR curves has been observed. These ACAR curves can be decomposed into three Gaussian components: a narrow (N), an intermediate (M) and a broad (B) component, with FWHM of 2-5, about 6 and 11 mrad, respectively. The N and M components are attributed to positrons trapped in the voids. A magnetic quenching effect is observed for the N component but not for the M component. This shows that the N component is due to two photon self-annihilation of positronium (Ps) formed in voids. The FWHM of the N component indicates, through the momentum of zero-point motion of Ps, that the average void diameter is 0.6 nm after annealing at 1000 K and 1.7 nm after annealing at 1525 K. Striking similarity of the M component to a void-surface trapping component in metallic Al, together with nearly the same lifetime as that of voids in Al, suggests the existence of metallic surface-conduction-electron states in the voids in α-alumina. ((orig.))

  19. ESR study of irradiated single crystals of the cocrystalline complex of cytidine: Salicylic acid

    Irradiation at 77 K of single crystals of the 1:1 complex of cytidine and salicylic acid produces a phenoxyl radical formed by oxidation of the salicylic acid. Anisotropic hyperfine coupling tensors have been determined for this radical which are associated with the para and ortho hydrogens. No cytidine oxidation products (alkoxy or hydroxyalkyl radicals) were observed at 77 K. Following the decay of the phenoxyl radical at room temperature, four radicals were detected. These include the cytosine 5--yl and 6--yl radicals, formed by H addition to the cytosine ring, and an anisotropic doublet. By UV irradiation at room temperature, it is possible to convert a significant fraction of 6-yl radicals into 5-yl radicals. Hyperfine coupling and g tensors determined for the anisotropic doublet indicate that this radical is formed in the C/sub 1'/-C/sub 2'/ region of the sugar moiety. These results indicate a shift in radiation damage away from the salicylic acid upon warming, and show that the radiation chemistry of the cocrystalline complex is different from that of the isolated bases

  20. Correlation of Beam Electron and LED Signal Losses under Irradiation and Long-term Recovery of Lead Tungstate Crystals

    Batarin, V A; Davidenko, A M; Derevshchikov, A A; Goncharenko, Yu M; Grishin, V N; Kachanov, V A; Konstantinov, A S; Kravtsov, V I; Kubota, Y; Lukanin, V S; Matulenko, Yu A; Melnik, Yu M; Meshchanin, A P; Mikhalin, N E; Minaev, N G; Mochalov, V V; Morozov, D A; Nogach, L V; Ryazantsev, A V; Semenov, P A; Semenov, V K; Shestermanov, K E; Soloviev, L F; Stone, S; Uzunian, A V; Vasilev, A N; Yakutin, A E; Yarba, J V

    2005-01-01

    Radiation damage in lead tungstate crystals reduces their transparency. The calibration that relates the amount of light detected in such crystals to incident energy of photons or electrons is of paramount importance to maintaining the energy resolution the detection system. We report on tests of lead tungstate crystals, read out by photomultiplier tubes, exposed to irradiation by monoenergetic electron or pion beams. The beam electrons themselves were used to measure the scintillation light output, and a blue light emitting diode (LED) was used to track variations of crystals transparency. We report on the correlation of the LED measurement with radiation damage by the beams and also show that it can accurately monitor the crystals recovery from such damage.

  1. Magnetic flux oscillations in partially irradiated Bi2Sr2CaCu2O8+δ crystals

    Barness, D.; Sinvani, M.; Shaulov, A.; Trautmann, C.; Tamegai, T.; Yeshurun, Y.

    2009-04-01

    We report on generation of spatiotemporal oscillations of magnetic flux in a Bi2Sr2CaCu2O8+δ crystal irradiated in part with 2.2 GeV Au ions. Flux oscillations are spontaneously excited after exposing the sample to a steady magnetic field near the order-disorder vortex phase transition line. The oscillations originate at the border between the irradiated and nonirradiated parts of the sample and propagate into the nonirradiated region toward the sample edge. Previously reported flux oscillations were observed in the vicinity of undefined defects in as grown Bi2Sr2CaCu2O8+δ crystals. Observation of spontaneous oscillations in partially irradiated samples present the first attempt to generate such oscillations in a controlled manner.

  2. Spatially resolved nuclear spin relaxation, electron spin relaxation and light absorption in swift heavy ion irradiated LiF crystals

    Spatially resolved 19F and 7Li spin-lattice relaxation rates are measured for LiF single crystals after irradiation with two kinds of swift heavy ions (12C of 133 MeV and 208Pb of 1.78 GeV incident energy). Like in earlier studies on 130Xe and 238U irradiated LiF crystals, we found a strong enhancement of the nuclear spin-lattice relaxation rate within the ion penetration depth and a slight-but still significant-enhancement beyond. By evaluating the nuclear relaxation rate enhancement within the ion range after irradiation with different projectiles, a universal relationship between the spin-lattice relaxation rate and the dose is deduced. The results of accompanying X-band electron paramagnetic resonance relaxation measurements and optical absorption spectroscopy are included in a physical interpretation of this relationship. Also the reason for the enhanced relaxation rate beyond the ion range is further discussed.

  3. Mechanical characterization of magnesium aluminate MgO·nAl2O3 spinel single crystals irradiated with Cu- ions

    Ion-irradiation response of spinel single crystals was investigated using a nanoindentation technique. Specimens of stoichiometric (n=1) and non-stoichiometric (n=2.4) single crystals of MgO n(Al2O3) spinel were irradiated with 60 keV Cu- ion at room temperature. Dose rate ranged from 1 to 100 μA/cm2, and a total dose was kept constant at 3x1016 ions/cm2. Both plastic hardness and elastic modulus of all the irradiated specimens were softened. Radiation-induced swelling simultaneously occurred. Rutherford back scattering spectroscopy detected disordering of spinel crystalline structure. Accordingly, the radiation-induced softening and swelling are ascribed to accumulation of point defects associated with the disordering. In comparison between the stoichiometric and the non-stoichiometric specimens, the radiation-induced softening is suppressed in the non-stoichiometric composition. (author)

  4. Influence of gamma irradiation on electric and dielectric properties of TIGaTe2 crystals

    Full text: TlGaTe2 has a quasi-one-dimensional layered structures and exhibit para-to-ferroelectric phase transitions through an intermediate incommensurate phase. TlGaTe2 exhibit nonlinear transport properties. This structure is body-centered tetragonal and features c-axis chains of atoms and edge-sharing GaTe4 tetrahedra. The TlGaTe2 monocrystals were grown by the modified Bridgman-Stockbarger method. The measurements were carried out on the sides perpendicular to polar axis. The sides were ground and covered by silver paste. Dielectric constant ε(T) and angle tangent of dielectric losses were measured by the alternating current bridge E7-8 (1 kHz), P5058 (10 kHz), E7-12 (1 mHz) and Tesla BM560 (100 kHz) in the temperature region 150-250K. The velocity of temperature scanning was 0,1 K / min. The loops of dielectric hysteresis were studied at frequency 50 Hz using the modified circuit Soyer-Tower. The pyroeffect has been investigated by the quasistatic method using universal voltmeter V7-30. The samples were irradiated (Co60) at room temperature. The irradiation dose was accumulated through sequential exposures of the same sample and reached 100, 200, 300 and 400 Mrad. The dependences ε(T) and σ(T) were measured after each exposure of the sample to irradiation. Conductivity was measured by the alternating current method. The temperature dependencies of dielectric constant ε(T) of TlGaTe2 crystals at different frequencies are measured. It is known, that the presence of an impurity in the semiconductor results in occurrence of local states near the Fermi level. On these local states the hopping mechanism of charge transport is realized, which essentially influences both on electrical, and dielectrically properties of semiconductor-ferroelectrics. TlGaTe2. According to the temperature dependencies of dielectric constant ε(T) study, TlGaTe2 has temperature instabilities of the crystal lattice lead to ferroelectric ordering. (author)

  5. Pulsed EPR study of low-dose irradiation effects in L-alanine crystals irradiated with γ-rays, Ne and Si ion beams

    Low-dose irradiation effects in L-alanine single crystals irradiated with γ-rays, Ne and Si ion beams have been investigated by means of a two-pulse electron spin echo (ESE) technique. An effective phase memory time, TM, was measured from the first stable L-alanine radical, SAR1, and its complex relaxation mechanism is discussed. Both spectral and instantaneous diffusion contributions to the total effective relaxation rate have been extrapolated through the detection of the two-pulse ESE signal as a function of turning angle. The local microscopic concentration of paramagnetic centers C(ions)/C(γ-ray) for low-dose heavy-ion irradiation has been deduced from the corresponding spin-spin interaction

  6. Thermoluminescence studies on single crystal, polycrystalline and glass lithium tetraborate samples irradiated by X-rays from Indus-2

    Kar, S.; Debnath, C.; Verma, S. [Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Dhamgaye, V.P.; Lodha, G.S. [X-ray Optics Section, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Bartwal, K.S., E-mail: bartwal@rrcat.gov.in [Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)

    2015-01-01

    Undoped, Mn doped and Cu doped samples of lithium tetraborate (LTB) were prepared in single crystal, polycrystalline and glass forms. These samples were investigated for their thermoluminescence (TL) response on irradiation by X-rays from Indus-2 synchrotron radiation source. Two well separated peaks were observed in TL glow curves for the doped single crystal and polycrystalline samples; however, glass samples show only one peak. Activation energy, frequency factor and order of kinetics were determined from the TL glow curve. Cu doped LTB crystal sample was found most TL sensitive whereas undoped LTB glass gives the least TL counts. Compared to doped samples, the undoped LTB glass sample was found suitable for high dose measurement immediately after irradiation.

  7. Homogeneous liquid crystal alignment characteristics on solution-derived HfYGaO films treated with IB irradiation.

    Lee, Yun-Gun; Park, Hong-Gyu; Jeong, Hae-Chang; Lee, Ju Hwan; Heo, Gi-Seok; Seo, Dae-Shik

    2015-06-29

    Solution-derived HfYGaO films have been treated by ion beam (IB) irradiation and used as liquid crystal (LC) alignment layers. Solution processing was adopted due to its simplicity, high throughput, and facile composition modification. Homogeneous and uniform LC alignment was achieved on the IB-irradiated HfYGaO films, and when these films were adopted in twisted nematic (TN) cells, electro-optical performance comparable to that of TN cells with conventional polyimide layers was achieved, with almost no capacitance-voltage hysteresis. Moreover, LC cells based on IB-irradiated HfYGaO films had a high thermal budget. The proposed IB-irradiated solution-derived HfYGaO films have considerable potential for use in advanced LC applications. PMID:26191738

  8. Fast crystallization of amorphous Gd2Zr2O7 induced by thermally activated electron-beam irradiation

    We investigate the ionization and displacement effects of an electron-beam (e-beam) on amorphous Gd2Zr2O7 synthesized by the co-precipitation and calcination methods. The as-received amorphous specimens were irradiated under electron beams at different energies (80 keV, 120 keV, and 2 MeV) and then characterized by X-ray diffraction and transmission electron microscopy. A metastable fluorite phase was observed in nanocrystalline Gd2Zr2O7 and is proposed to arise from the relatively lower surface and interface energy compared with the pyrochlore phase. Fast crystallization could be induced by 120 keV e-beam irradiation (beam current = 0.47 mA/cm2). The crystallization occurred on the nanoscale upon ionization irradiation at 400 °C after a dose of less than 1017 electrons/cm2. Under e-beam irradiation, the activation energy for the grain growth process was approximately 10 kJ/mol, but the activation energy was 135 kJ/mol by calcination in a furnace. The thermally activated ionization process was considered the fast crystallization mechanism

  9. Electron irradiation effects on 4-amino-5-mercapto- 3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole single crystal

    Vijayalakshmi Rao; K Naseema

    2010-09-01

    In this paper, we report the electron irradiation effects on the properties of an organic NLO single crystal of 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole. The crystal was irradiated with electron beam of different doses and was characterized by powder XRD, UV–Vis, FTIR, DSC, microhardness and SHG measurements. In XRD, the peaks are shifted due to irradiation. The SHG efficiency has been found to enhance rapidly with irradiation. The investigation of the influence of electron irradiation on the surface morphology of the grown crystal reveals the formation of craters on the surface. The laser damage threshold remains constant as the dose rate increases whereas refractive index increases after irradiation.

  10. Thermoluminescence and photoluminescence studies on γ-ray-irradiated Ce(3+) ,Tb(3+) -doped potassium chloride single crystals.

    Bangaru, S; Saradha, K; Muralidharan, G

    2016-05-01

    Single crystals of KCl doped with Ce(3+) ,Tb(3+) were grown using the Bridgeman-Stockbarger technique. Thermoluminescence (TL), optical absorption, photoluminescence (PL), photo-stimulated luminescence (PSL), and thermal-stimulated luminescence (TSL) properties were studied after γ-ray irradiation at room temperature. The glow curve of the γ-ray-irradiated crystal exhibits three peaks at 420, 470 and 525 K. F-Light bleaching (560 nm) leads to a drastic change in the TL glow curve. The optical absorption measurements indicate that F- and V-centres are formed in the crystal during γ-ray irradiation. It was attempted to incorporate a broad band of cerium activator into the narrow band of terbium in the KCl host without a reduction in the emission intensity. Cerium co-doped KCl:Tb crystals showed broad band emission due to the d-f transition of cerium and a reduction in the intensity of the emission peak due to (5) D3 -(7) Fj (j = 3, 4) transition of terbium, when excited at 330 nm. These results support that energy transfer occurs from cerium to terbium in the KCl host. Co-doping Ce(3+) ions greatly intensified the excitation peak at 339 nm for the emission at 400 nm of Tb(3+) . The emission due to Tb(3+) ions was confirmed by PSL and TSL spectra. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26381612

  11. Effect of high-energy heavy ion irradiation on the crystallization kinetics of Co-based metallic glasses

    Rohit Jain; Deepika Bhandari; N S Saxena; S K Sharma; A Tripathi

    2001-02-01

    Differential scanning calorimeter (DSC) is employed to study the crystallization kinetics of irradiated (at three different fluences with high-energy heavy ion; Ni11+ of 150 MeV) specimens of two Co-based metallic glasses. It is found that the crystallization process in both the glasses is completed in two phases. The DSC data have been analysed in terms of kinetic parameters viz. activation energy (), Avrami exponent (), dimensionality of growth (), using two different theoretical models. The results obtained have been compared with that of virgin samples. The lower activation energy in case of second crystallization occurring at higher temperature indicates the easier nucleation of second phase. The abnormally high value of Avrami exponent in Co–Ni glass indicates very high nucleation rate during first crystallization.

  12. Synthesis of TiO2 nanoscale rods with MHz femtosecond laser irradiation of single crystal surface and characterisation

    M.Sivakumar; Bo Tan; Krishnan Venkatakrishnan

    2011-01-01

    Growth of nanoscale rods on single crystal rutile TiO2 surface irradiated by MHz pulse repetition rate femtosecond laser in nitrogen environment without a catalyst or template is reported. The rods are of 100 nm in width to 1 micron length. Microraman analysis of the laser irradiated surface shows only a decrease in the intensity of active modes as compared to untreated surface. The growth of TiO2 nanorods can be explained by a method combining nanoparticles formation due to expulsion of molt...

  13. In-situ observation of damage evolution in TiC crystals during helium ion irradiation

    In-situ observations were performed on bubble formation and growth in TiC during 20 keV helium ion irradiation over the wide range of irradiation temperatures from 12 to 1523 K. No amorphization occurred over this temperature range. The bubble densities and sizes were almost independent of irradiation temperatures from 12 to 1273 K. Remarkable growth and coalescence occurred during irradiation at high temperature above 1423 K and during annealing above 1373 K after irradiation. ((orig.))

  14. Radiation damage in vitamin B1: an ENDOR study of an x-irradiated single crystal of thiamine

    A single crystal of thiamine chloride hydrochloride has been x-irradiated at room temperature and studied by 1H-ENDOR spectroscopy at 110 K. It is shown that at least two radical species are trapped in the crystal. Several 1H-hyperfine tensors have been determined for each radical; they indicate that one species is due to cleavage of the thiamine molecule into its pyrimidine and thiazole moieties while the other species is due to hydrogen addition onto the pyrimidine ring. (author)

  15. Relation between the swelling and the disordering in ionic crystals irradiated by fast heavy ions

    When fast heavy ions penetrate in matter, they slow down essentially by depositing their energy on the electrons. This can lead to strong electronic excitation densities in the solid and then to structural modifications. In this work, calcium fluoride (CaF2) was used to look further into the damage induced by irradiation with fast heavy ions in ionic crystals. Four techniques were mainly employed to characterise this damage. These techniques of analysis are wide angle X-ray diffraction, surface profilometry, Rutherford backscattering spectrometry and UV-visible optical absorption spectroscopy. The results of this work show that CaF2 answers in a multiple way to the electronic excitations. For stopping powers higher than approximately 5 keV/nm, a polygonization seems to occur. This causes a structural disorder, a swelling of 0.27 % and the formation of fractures in the material. A second damage mechanism is caused above approximately 13 keV/nm and results in a loss of the initial crystalline structure. However, optical centres appear whatever the ion stopping power, which indicates that these defects cannot be the cause of the two above mentioned damage mechanisms. According to a thermal spike model, the two thresholds can be linked to melting and sublimation energy of the material, respectively. (author)

  16. Effects of swift argon-ion irradiation on the proton-exchanged LiNbO3 crystal

    Huang Qing; Liu Peng; Liu Tao; Guo Sha-Sha; Wang Xue-Lin

    2012-01-01

    A proton-exchanged LiNbO3 crystal was subjected to 70-MeV argon-ion irradiation.The lattice damage was investigated by the Rutherford backscattering and channeling technique.It was found that the lattice disorder induced by the proton exchange process was partially recovered and the proton-exchanged layer was broadened.It indicated that the lithium ions underneath the initial proton-exchanged layer migrated to the surface during the swift argon-ion irradiation and supplemented the lack of lithium ions in the initial proton-exchanged layer.This effect was ascribed to the great electronic energy deposition and relaxation.The swift argon-ion irradiation induced an increase in extraordinary refractive index and formed another waveguide structure beneath the proton-exchanged waveguide.

  17. Superior optical properties of homogeneous liquid crystal alignment on a tin (IV) oxide surface sequentially modulated via ion beam irradiation.

    Kang, Young-Gu; Park, Hong-Gyu; Kim, Hyung-Jun; Kim, Young-Hwan; Oh, Byeong-Yun; Kim, Byoung-Yong; Kim, Dai-Hyun; Seo, Dae-Shik

    2010-10-11

    We first investigated the alignment characteristics of tin (IV) oxide (SnO(2)) thin films deposited by radio-frequency (RF) magnetron sputtering. This study demonstrates that liquid crystal (LC) molecules could be aligned homogeneously by controlling the Ion Beam (IB) irradiation energy densities. We also show that the pretilt angle of the LC molecules has a close relation with the surface energy. X-ray photoelectron spectroscopy (XPS) indicates that a non-stoichiometric SnO(2-x) surface converted by ion beam irradiation can horizontally align the LC molecules. The measured electro-optical (EO) characteristics showed high performance, comparable with those of rubbed and ion-beam irradiated polyimide (PI) layers. PMID:20941057

  18. The influence of Pb-ion irradiation on melt-textured YBa2Cu3Ox crystals

    Melt-textured YBa2Cu3Ox crystals have been irradiated along the c-axis with 208Pb56+ ions corresponding to dose matching fields, BΦ=0.5 T and BΦ=2.0 T. Magnetization measurements were conducted along the ab plane of the samples. The strength of pinning sites was investigated by measuring magnetization hysterisis and the saturation remanent magnetization MR at several temperatures. We have found that the pinning strength was considerably enhanced after irradiation at both doses. Interestingly, the pinning strength at a Pb-ion irradiation which corresponds to the dose matching field BΦ=0.5 T, was found to be significantly larger than that at the dose matching field BΦ=2.0 T at all temperatures. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Comparative study of effects of low dose gamma-irradiation on phase transitions in single crystals of triglycine sulfate and its deuterated analogue

    Paper presents the results of the comparative study of the effect of γ-irradiation low (less than 0.5 MR) doses on the specific heat (Cp) of triglycine sulfate crystal and of its deuterated analogue prepared by means of the precision vacuum adiabatic calorimetry within 80-350 K temperature range. One observed essential changes of Cp behaviour of the pure and the γ-irradiated crystals near (Tc) phase transition temperature decreasing as the dose increased

  20. Anisotropy and Raman absorption of the polyimide surface irradiated by the ion beam for liquid crystal alignment

    In this paper, polyimide surfaces irradiated by an ion-beam for liquid crystal alignment are investigated by using atomic force microscopy, Raman spectroscopy, and spectroscopic ellipsometry. A liquid crystal cell aligned homogeneously through the ion-beam exposure exhibits electro-optic switching behavior similar to that of a rubbing-aligned liquid crystal cell. However, we found that the surface morphology and bonding molecules of ion-beam-treated polyimide surfaces show properties very different from mechanically-rubbed ones. Experimental results show that optical anisotropy of ion-beam-treated polyimide surfaces results in the formation of hydrogenated amorphous carbon-like structure with a short main-chain, while mechanical rubbing has little effect on structural and compositional variations of polyimide layers

  1. Short-living centers of color and luminescence in LiNbO3 crystals irradiated by pulsed electron beams

    Paper presents data on investigation into spectra of short-living optical absorption (SOA) and of luminescence inducted in lithium niobate crystals under pulsed electron irradiation (0.25 MeV, 20 ns, 15-160 mJ/Cm2) within 80-350 K temperature range. Within SOA spectra one distinguished anisotropic band with maximums at 1.6 and 4.0 eV resulting from capture of one or two conduction electrons for bunches (NbNb - NbLi) respectively as well as, slightly polarized bands at 2.5 and 3.3 eV caused by holes localized in Li and Nb vacancies. Cathodoluminescence (CL) of lithium niobate crystals is characterized by quick (τ < 4 ns) dying down. Variation of initial defect nature of crystal via their regeneration under 830 K is shown to result in similar for CL and for SOA variation of spectra

  2. Gamma-ray irradiation effect on the absorption and luminescence spectra of Nd:GGG and Nd:GSGG laser crystals

    Sun Dunlu [Crystal Lab, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shushanhu Road 350, PO Box 1125, Hefei, Anhui 230031 (China); Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, Aveiro 3810-193 (Portugal)], E-mail: dlsun@aiofm.ac.cn; Luo Jianqiao; Zhang Qingli [Crystal Lab, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shushanhu Road 350, PO Box 1125, Hefei, Anhui 230031 (China); Xiao Jingzhong [Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, Aveiro 3810-193 (Portugal); Xu Jiayue [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Jiang Haihe; Yin Shaotang [Crystal Lab, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shushanhu Road 350, PO Box 1125, Hefei, Anhui 230031 (China)

    2008-12-15

    Laser crystals Nd{sup 3+}:Gd{sub 3}Ga{sub 5}O{sub 12} (Nd:GGG) and Nd{sup 3+}:Gd{sub 3}Sc{sub 2}Ga{sub 3}O{sub 12} (Nd:GSGG) were grown by Czochralski method. The influence of gamma-ray irradiation on their absorption and luminescence spectra has been investigated. Two additional absorption (AA) bands induced by gamma-ray irradiation appear in the spectra of Nd:GGG crystal while only a very weak AA band appears for the Nd:GSGG crystal. This indicated that Nd:GSGG crystal has stronger ability to resist the color center formation by irradiation. The intensity of the excitation and emission spectra of Nd:GGG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, a luminescence strengthening effect was observed in Nd:GSGG crystal after exposure to the same irradiation dose. The results showed that the Nd:GSGG crystal is a promising candidate used under radiation environments such as in outer space.

  3. Gamma-ray irradiation effect on the absorption and luminescence spectra of Nd:GGG and Nd:GSGG laser crystals

    Laser crystals Nd3+:Gd3Ga5O12 (Nd:GGG) and Nd3+:Gd3Sc2Ga3O12 (Nd:GSGG) were grown by Czochralski method. The influence of gamma-ray irradiation on their absorption and luminescence spectra has been investigated. Two additional absorption (AA) bands induced by gamma-ray irradiation appear in the spectra of Nd:GGG crystal while only a very weak AA band appears for the Nd:GSGG crystal. This indicated that Nd:GSGG crystal has stronger ability to resist the color center formation by irradiation. The intensity of the excitation and emission spectra of Nd:GGG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, a luminescence strengthening effect was observed in Nd:GSGG crystal after exposure to the same irradiation dose. The results showed that the Nd:GSGG crystal is a promising candidate used under radiation environments such as in outer space

  4. Electron paramagnetic resonance study of free radicals in γ-irradiated single crystal of tris(glycine) calcium(II) dibromide

    Tris(glycine) calcium(II) dibromide single crystal has been irradiated with a γ-source to produce free radicals and the irradiated sample has been subjected to EPR studies. The observed spectra reveal that an NH4 radical is formed by rupturing glycine molecule due to irradiation. The unpaired electron is localized on the C-N bond. The proton hyperfine interaction on the unpaired spin shows orthorhombic symmetry and the spectroscopic splitting factor remains isotropic. (author)

  5. Annihilation behaviour under electron irradiation of athermal ω-phase crystals formed by cooling at 131K in a β-Ti-Mo alloy

    Formation of athermal ω-phase crystals due to cooling to 131 K has been directly observed in a β-type Ti-15mass%Mo alloy. The athermal ω-phase crystals easily disappear by electron irradiation during the in-situ observation at 131 K. Incubation phenomenon of the annihilation is also recognized. The annihilation behaviour was investigated based on the dependence on electron irradiation conditions and incubation phenomena. It is concluded that the annihilation mechanism is concerned with interactive effects of temperature rise due to electron irradiation and collective oscillation resulted from inelastic scattering of electron beam.

  6. Study on excimer laser irradiation for controlled dehydrogenation and crystallization of boron doped hydrogenated amorphous/nanocrystalline silicon multilayers

    Gontad, F., E-mail: fran_gontad@yahoo.es [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Conde, J.C. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Filonovich, S.; Cerqueira, M.F.; Alpuim, P. [Department of Physics, University of Minho, Campus de Azurém, 4800-058 Guimarães (Portugal); Chiussi, S. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain)

    2013-06-01

    We report on the excimer laser annealing (ELA) induced temperature gradients, allowing controlled crystallization and dehydrogenation of boron-doped a-Si:H/nc-Si:H multilayers. Depth of the dehydrogenation and crystallization process has been studied numerically and experimentally, showing that temperatures below the monohydride decomposition can be used and that significant changes of the doping profile can be avoided. Calculation of temperature profiles has been achieved through numerical modeling of the heat conduction differential equation. Increase in the amount of nano-crystals, but not in their size, has been demonstrated by Raman spectroscopy. Effective dehydrogenation and shape of the boron profile have been studied by time of flight secondary ion mass spectroscopy. The relatively low temperature threshold for dehydrogenation, below the monohydride decomposition temperature, has been attributed to both, the large hydrogen content of the original films and the partial crystallization during the ELA process. The results of this study show that UV-laser irradiation is an effective tool to improve crystallinity and dopant activation in p{sup +}-nc-Si:H films without damaging the substrate. - Highlights: • An efficient dehydrogenation is possible through excimer laser annealing. • 140 mJ/cm{sup 2} is enough for dehydrogenation without significant changes in doping profile. • Fluences up to 300 mJ/cm{sup 2} promote partial crystallization of the amorphous structures.

  7. The role of impurities in thermally stimulated luminescence of MgO:Mn2+ and MgO:V2+ crystals irradiated in a reactor

    The high-temperature thermally stimulated luminescence (TSL) of nominally pure MgO crystals and MgO crystals with excessive amounts of paramagnetic manganese and vanadium ions irradiated in a reactor has been studied. It was observed that the influence of impurity on the TSL of crystal is different at low and relatively high doses. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Study and identification of paramagnetic centers by EPR technique in K3Cu(CN)4 crystals irradiated with X-rays

    Paramagnetic centers created in K3Cu(CN)4 crystals by X-ray irradiation, using EPR technique are studied. The crystals are irradiated in following conditions: a) liquid nitrogen temperatures, b) room temperatures. Crystals field models of the paramagnetic centers which determine the following local symmetric in order to satisfy experimental results: a) Cu++ in C sub(3v) symmetric and b) K0 in distorted octahedral symmetry are proposed. The decay of these centers and the observation that Cu++ ions are very much instable and disappear at T = 148K are studied. The K0 atom remain up to T approximatelly 300K. (E.G.)

  9. Broadband near-infrared luminescence in gamma-irradiated Bi-doped alpha-BaB(2)O(4) single crystals.

    Su, Liangbi; Yu, Jun; Zhou, Peng; Li, Hongjun; Zheng, Lihe; Yang, Yan; Wu, Feng; Xia, Haiping; Xu, Jun

    2009-08-15

    Spectroscopic properties of as-grown and gamma-irradiated undoped and Bi-doped alpha-BBO (BaB(2)O(4)) single crystals were investigated. Bi(2+) and color centers in Bi:alpha-BBO crystals were investigated to be nonluminescent in the near-infrared (NIR) region. Broadband NIR luminescence at 1139 nm with a FWHM of 108 nm and a decay time of 526 mus was realized in Bi:alpha-BBO crystal through gamma irradiation. Bi(+) was attributed to be responsible for the NIR emission, which can be bleached by thermal annealing. The involved physical processes in Bi:alpha-BBO crystal during the courses of irradiation and heat annealing were tentatively established. PMID:19684830

  10. Critical current densities in neutron irradiated Tl 2Ca 2Ba 2Cu 3O 10 single crystals

    Brandstätter, G.; Sauerzopf, F. M.; Weber, H. W.; Aghaei, A.; Schwarzmann, F.

    1994-12-01

    A Tl 2Ca 2Ba 2Cu 3O 10 single crystal with a transition temperature of 117.5 K was subjected to fast neutron irradiation to fluences of 2·10 21, 4·10 21, 8·10 21, and 1.6·10 22 m 2 (E>0.1 MeV). The superconducting transition temperatures T c, the hysteresis loops and the irreversibility lines were measured before and after each irradiation step. The critical current densities J c were calculated from the magnetization loops using an anisotropic Bean model. With increasing fluence we find a decrease of T c, as observed in YBCO-123 and other high temperature superconductors, and an increase of J c. The irreversibility line is shifted to higher fields and temperatures.

  11. Dosimetric characteristics of ultraviolet and x-ray-irradiated KBr:Eu{sup 2+} thermoluminescence crystals

    Melendrez, R.; Perez-Salas, R. [Programa de Posgrado en Fisica de Materiales, Centro de Investigacion, Cientifica y de Educacion Superior de Ensenada, Apartado Postal 2681, Ensenada, Baja California, 22800 (Mexico); Aceves, R.; Piters, T.M.; Barboza-Flores, M. [Centro de Investigacion en Fisica, Universidad de Sonora, Apartado Postal 5-088, Hermosillo, Sonora, 83190 (Mexico)

    1996-08-01

    Thermoluminescence (TL) characteristics of KBr:Eu{sup 2+} (150 ppm) previously exposed to ultraviolet (UV) light (200{endash}300 nm) and x-ray radiation at room temperature have been determined. The TL glow curve of UV-irradiated samples is composed of six peaks located at 337, 384, 402, 435, 475, and 510 K. The TL glow curves of x-irradiated samples show mainly a TL peak around 384 K. The TL intensities of UV-irradiated (402 and 510 K glow peaks) and x-irradiated specimens present a linear dependence as a function of radiation dose as well as fading stability 300 s after irradiation. These results further enhance the possibilities of using europium-doped materials in nonionizing (actinic region) and ionizing radiation detection and dosimetry applications. {copyright} {ital 1996 American Institute of Physics.}

  12. Dosimetric characteristics of ultraviolet and x-ray-irradiated KBr:Eu2+ thermoluminescence crystals

    Thermoluminescence (TL) characteristics of KBr:Eu2+ (150 ppm) previously exposed to ultraviolet (UV) light (200 endash 300 nm) and x-ray radiation at room temperature have been determined. The TL glow curve of UV-irradiated samples is composed of six peaks located at 337, 384, 402, 435, 475, and 510 K. The TL glow curves of x-irradiated samples show mainly a TL peak around 384 K. The TL intensities of UV-irradiated (402 and 510 K glow peaks) and x-irradiated specimens present a linear dependence as a function of radiation dose as well as fading stability 300 s after irradiation. These results further enhance the possibilities of using europium-doped materials in nonionizing (actinic region) and ionizing radiation detection and dosimetry applications. copyright 1996 American Institute of Physics

  13. Domain configurations in the ferroelectric phase of KH2AsO4 from ENDOR studies of irradiated crystals

    Using ENDOR spectroscopy, the radical AsO44- created by gamma irradiation in KH2AsO4 crystals has been reexamined. An earlier study by Dalal et al. had shown the existence of two types of domains in the ferro-electric phase. By considering the origin of a small splitting of the ENDOR lines, it is shown that in fact this technique allows the detection of the four domain types which are expected to exist in KH2AsO4 as in KH2PO4

  14. Development and high temperature testing by 14 MeV neutron irradiation of single crystal diamond detectors

    Pilotti, R.; Angelone, M.; Pagano, G.; Loreti, S.; Pillon, M.; Sarto, F.; Marinelli, M.; Milani, E.; Prestopino, G.; Verona, C.; Verona-Rinati, G.

    2016-06-01

    In the present paper, the performances of single crystal diamond detectors "ad hoc" designed to operate at high temperature are reported. The detectors were realized using commercial CVD single crystal diamond films, 500 micron thick with metal contacts deposited by sputtering method on each side. The new detector layout is based upon mechanical contacts between the diamond film and the electric ground. The detector was first characterized by measuring the leakage current as function of temperature and applied biasing voltage (I-V characteristics). The results obtained using two different metal contacts, Pt and Ag respectively, while irradiated with 14 MeV neutrons at the Frascati neutron generator (FNG) are reported and compared. It is shown that diamond detectors with Ag metal contacts can be properly operated in spectrometric mode up to 240oC with energy resolution (FWHM) of about 3.5%.

  15. Optical bleaching of F-centers in BaFCl crystals after X-irradiation at room temperature

    The optical bleaching behaviour of the F-band formed by X-irradiation in BaFCl crystals is investigated paying attention to the difference between two types of F-centers. Optical absorption spectra, decay curves of the F-band under excitation with F light and excitation spectra of the bleaching are given and discussed. The bleaching of the F-bands is achieved by light in the absorption band irrespective of the component. Energy transfer among excited states of F-centers is responsible for the bleaching of F-centers in BaFCl crystals, involving energy transfer between F(Cl-) and F(F-) centers in their optical bleaching process

  16. Magnetoplastic effect in irradiated NaCl and LiF crystals

    Impact of low doses of X-ray radiation on magnetoplastic effect is alkali-halide crystals, consisting in detachment of dislocations from paramagnetic centers under effect of external magnetic field is studied. The measurements of LiF crystals and three types of NaCl crystals, differing in the admixture content were conducted. Dependence of the dislocations medium run on the sample rotation frequency in the magnetic field proved to be especially sensitive to low doses

  17. Optical bleaching of colour centres in gamma-irradiated sodium chloride crystals

    The conversion of F centers to F-aggregate centers in gamma-coloured NaCl crystals of various origin and purity is examined. The conversion efficiency is the highest in NaCl crystals of natural origin with possibly low contents of primary vacancies (negligible quantity of trapped-hole defects active in trapping F-centre electrons). It is shown that M and R centres are formed in an early stage and N1 centres in a later stage process. The results obtained imply that in certain crystals subjected to the action of ionizing radiation, the F centres are formed within some preferred regions of the crystal. (author)

  18. Early Stage of Deformation under Nanoindenter Tip of Ion-irradiated Single Crystals

    Ion irradiation has been used for almost 40 years to emulate the effect of neutrons. Ion irradiation has a number of advantages in terms of time and expenses compared to neutron irradiation. Ion irradiation is expected to greatly contribute to the development of Fusion and Gen IV materials. Ions have short penetration depth, and they induce continuously varying dose rate over the penetration depth. Although it depends on the energy and species of incident ions, the depth of ion-irradiated region is in general on the order of a few micron meters. Depth controlled probing technique is required to measure the mechanical properties of ion-irradiated layer, and nanoindentation is widely used. During nanoindentation, a hard tip with known properties is pressed into a material which has unknown properties. The depth of penetration and load on the indenter are recorded during loading and unloading. The initial Loading depth curve follows the Hertzian elastic solution, and at a certain load, a sudden displacement excursion occurs in indenter depth and then hardening follows. This is called 'Pop-in' event, and since residual impression can be found only after pop-ins, the pop-in is regarded as the onset of plasticity. The objectives of this research are to investigate the effects of ion irradiation on popins, and to examine dislocation nucleation and propagation at the onset of plasticity by using MD simulations

  19. Formation of color centers in CdF/sub 2/ crystals irradiated by gamma rays

    Kaipov, B.; Tavshunskii, G.A.; Gapparov, N.

    1975-01-01

    After irradiation in liquid nitrogen, an ultraviolet absorption band in the region of 350 nm was induced in all samples. This band is maintained during annealing of thermoemission peaks below 170/sup 0/K. On annealing above this temperature the absorption band at 350 nm vanished, and the EPR signal with g = 2.014 induced by the gamma irradiation at 77/sup 0/K vanished at the same time. This behavior is attributed to the formation of localized holes by the gamma irradiation. (SJR)

  20. EPR, Endor and DFT Studies on X-Irradiated Single Crystals of L-Lysine HCl 2 H 2O and L-Arginine HCl H2O

    Zhou, Yiying; Nelson, William H.

    2011-03-01

    When proteins and DNA interact, arginine and lysine are the two amino acids most often in close contact with the DNA. In order to understand the radiation damage to DNA in vivo, which is always associated with protein, it is important to learn the radiation chemistry of arginine and lysine independently, and then complexed to DNA. This work studied X-irradiated single crystals of L- lysine . HCl . 2 H2 O and L- arginine . HCl . H2 O with EPR, ENDOR techniques and DFT calculations. In both crystal types irradiated at 66K, the carboxyl anion radical and the decarboxylation radical were identified. Specifically, the calculations performed on the cluster models for the carboxyl anion radicals reproduced the proton transfers to the carboxyl group from the neighboring molecules through the hydrogen bonds. Moreover, computations supported the identification of one radical type within irradiated arginine as the guanidyl radical anion with an electron trapped by the guanidyl group. Based on the radicals detected in the crystal irradiated at 66K and at 298K, and the annealing experiments from the irradiation at 66K, the mechanisms of the irradiation damage on lysine and arginine were proposed, and the possible effects of irradiated arginine and lysine to the DNA within chromatin were analyzed.

  1. Mechanical properties and microstructures of copper, gold and palladium single crystals irradiated with 600 MeV protons

    In the present work, the defect microstructures and hardening effects produced by 600 MeV proton irradiation in Cu, Pd and Au single crystals have been studied at room temperature. The defect microstructures in the irradiated Cu have been investigated by using transmission electron microscopy (TEM) in a dose range from 9.7x10-4 to 4.6x10-2 dpa. It has been observed that about 90% of the total defect clusters are stacking fault tetrahedra (SFT's). This fraction is independent of the thickness of the foil up to about 130 nm. The irradiation defect cluster densities obtained are in agreement with previous published results of high energy proton irradiation. With the present data at medium doses, the dose dependence of the defect cluster density, in high energy proton irradiated Cu, has been well established. A comparison between the results of Cu irradiated with high energy protons, fusion neutrons and fission neutrons indicates that there is no difference in defect cluster densities produced by these particle irradiations when the results are compared on the basis of dpa. The data compiled can be fitted within a band which shows that the defect cluster density starts to saturate at a value of about 4x1023 m-3. A large transition dose range between the linear dependence to the saturation is located between 3x10-3 and 1x10-1 dpa. The defect cluster size distribution measured under weak beam dark field (WBDF) imaging conditions with (g,6g) (WBDF(g,6g)), g=200, shows that the most probable size is between 1.5 and 2 nm and the mean size is about 2 nm independent of the dose. This result is also in agreement with published results. The defect structure in Au at dose of 1.1x10-1 dpa has been observed. It shows that about 85% of the total defect clusters are SFT's. There are no grouped defect clusters, which may probably be due to the fact that the defect cluster density (5.1x1023) has already saturated at this high dose. The most probable defect cluster size is between 2

  2. Longitudinal uniformity, time performance and irradiation test of pure CsI crystals

    Angelucci, M.; Atanova, O.; Baccaro, S; Cemmi, A.; Cordelli, M.; Donghia, R.; S. Giovannella; Happacher, F.; Miscetti, S.; I. Sarra; Soleti, S. R.

    2016-01-01

    To study an alternative to BaF2, as the crystal choice for the Mu2e calorimeter, thirteen pure CsI crystals from Opto Materials and ISMA producers have been characterized by determining their light yield (LY) and longitudinal response uniformity (LRU), when read with a UV extended PMT. The crystals show a LY of ~ 100 p.e./MeV (~ 150 p.e./MeV) when wrapped with Tyvek and coupled to the PMT without (with) optical grease. The LRU is well represented by a linear slope that is on average around -0...

  3. Behavior under gamma irradiation of single crystals of NaCl doped with divalent cations

    Thermally stimulated luminescence and optical absorption measurements were performed on NaCl single crystals, both single and double doped. The NaCl single crystals were exposed to gamma rays from a 60Co source at both low and room temperatures. The radiation-induced defects were mainly F and H centers, and the absorption bands for the F centers were centered at 464 nm. Bleaching with F-light showed the participation of the F center generated by gamma radiation on the TL phenomenon. The results suggest that NaCl single crystals, both single and double doped can be used as dosimeters, within certain doses. (author)

  4. Study on the effect of heat-annealing and irradiation on spectroscopic properties of Bi:alpha-BaB2O4 single crystal.

    Xu, Jun; Zhao, Hengyu; Su, Liangbi; Yu, Jun; Zhou, Peng; Tang, Huili; Zheng, Lihe; Li, Hongjun

    2010-02-15

    The absorption, excitation, and ultrabroadband near-infrared luminescence spectra of Bismuth were investigated in H(2)-annealed and gamma-irradiated Bi:alpha-BaB(2)O(4)(alpha-BBO) single crystals, respectively. Energy-level diagrams of the near-infrared luminescent centers were fixed. The electronic transition energies of near-infrared active centers are basically consistent with the multiplets of free Bi(+) ions. The minor difference of the energy-level diagrams of Bi(+) ions in H(2)-annealed and gamma-irradiated Bi:alpha-BaB(2)O(4) crystals can be ascribed to the difference of the local lattice environments. The involved physical and chemical processes were discussed. The effect of Ar-, air-annealing and electron-irradiation on Bi:alpha-BaB(2)O(4) crystal were also investigated. PMID:20389348

  5. Study of local crystallization induced in FeSiNbZrB amorphous alloy by swift heavy ion (SHI) irradiation at room temperature

    Sun, Jianrong, E-mail: sunjr@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Wang, Zhiguang; Wang, Yuyu; Chang, Hailong; Song, Peng; Shen, Tielong; Zhu, Yabin; Pang, Lilong [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Li, Fashen [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

    2013-07-15

    Amorphous FeSiNbZrB alloy (metallic glass) ribbons were prepared by melt spinning and swift heavy ion (SHI) irradiation experiments were performed on the materials research terminal of the 320 kV ECR platform at the Institute of Modern Physics (IMP), Lanzhou. XRD, TEM and Mössbauer spectroscopy was used to reveal the irradiation-induced local crystallization, plastic deformation, damages and the magnetic moments rearrangements. The dimensions of our ribbons perpendicular to ion beam direction increased slightly , but the ribbon dimension along the ion beam shrunk; Irradiation of Xe-ions could cause local crystallization of amorphous FeSiNbZrB alloy ribbons and form finer α-Fe(Si) phases precipitations with diameter of 1–2 nm; SHI irradiation could make the distribution of the magnetic moments of amorphous ribbons change their orientation from the in-plane orientation to the perpendicular one.

  6. Effects of O2+ ions beam irradiation on crystal structure of rare earth sesquioxides

    We report the results of ion irradiation influence on rare earth sesquioxides structure, which are materials of practical importance as a radiation resistant ceramics in nuclear applications. Y2O3, Gd2O3 and Er2O3 sesquioxides in the pellet form were irradiated by oxygen ions (O2+) beam with the energy of 30 keV and implantation fluence of 5 x 1020 m-2. Samples are characterized by Grazing Incidence X-ray Diffraction (GIXRD), Raman spectroscopy and atomic force microscopy (AFM). By GIXRD it was found partial transformation from cubic (C) to monoclinic (B) phase only in Gd2O3, induced by O2+ irradiation. This was confirmed by Raman spectroscopy. Although full phase transition from C to B phase in Y2O3 was not observed, the splitting and broadening of the main intensity Raman band for C phase could be explained by the stress and the disorder induced by the quenching. Analysis done by AFM showed changes in surface topology, i.e. values of average roughness (Ra) and root mean squared roughness (RMS) were significantly changed after irradiation for all samples. RMSs in Y2O3 before and after irradiation were 35 nm and 26 nm, respectively.

  7. Electron spin resonance and E.N.D.O.R. double resonance study of free radicals produced by gamma irradiation of imidazole single crystals

    Gamma irradiation of imidazole single crystals at 300 deg. K gives two radicals. Identification and detailed studies of their electronic and geometric structure have been made by ESR and ENDOR techniques. A study of the hydrogen bonded protons hyperfine tensor is made and let us conclude to the inexistence of movement and tunneling of these protons. The principal low temperature radical, produced by gamma irradiation at 77 deg. K has been also studied by ESR and a model has been proposed. (author)

  8. Longitudinal uniformity, time performance and irradiation test of pure CsI crystals

    Angelucci, M; Baccaro, S; Cemmi, A; Cordelli, M; Donghia, R; Giovannella, S; Happacher, F; Miscetti, S; Sarra, I; Soleti, S R

    2016-01-01

    To study an alternative to BaF2, as the crystal choice for the Mu2e calorimeter, thirteen pure CsI crystals from Opto Materials and ISMA producers have been characterized by determining their light yield (LY) and longitudinal response uniformity (LRU), when read with a UV extended PMT. The crystals show a LY of ~ 100 p.e./MeV (~ 150 p.e./MeV) when wrapped with Tyvek and coupled to the PMT without (with) optical grease. The LRU is well represented by a linear slope that is on average around -0.6 %/cm. The timing performances of the Opto Materials crystal, read with a UV extended MPPC, have been evaluated with minimum ionizing particles. A timing resolution of ~ 330 ps (~ 440 ps) is achieved when connecting the photosensor to the MPPC with (without) optical grease. The crystal radiation hardness to a ionization dose has also been studied for one pure CsI crystal from SICCAS. After exposing it to a dose of 900 Gy, a decrease of 33% in the LY is observed while the LRU remains unchanged.

  9. Origin of TSL peaks located at 200-250 K in UV-irradiated PbWO4 crystals

    Thermally stimulated luminescence (TSL) was studied for many PbWO4 crystals after their selective irradiation at 80-220 K in the 3.4-5.0 eV energy range to clarify the origin of the defects responsible for the TSL peaks located in the 200-250 K range. The conclusion is made that both in PbWO4 and PbWO4:Mo crystals the total TSL intensity and the intensity ratio of various TSL peaks are mainly determined by the concentration and type of oxygen and lead vacancies which depend on the crystal preparation and annealing conditions and on the concentration of trivalent rare-earth impurity ions. The TSL peak near 200 K is ascribed to {Pb+-WO3} centers and the peak in the 210-230 K range, to the electron centers, containing oxygen vacancies of the type of WO2 and WO. Only the 250 K peak arises from electron MoO43- centers. Thermally stimulated processes are accompanied with the green G(II) emission

  10. Thermal bleaching of optical absorption and photoluminescence spectra of γ-irradiated CaF_2:Dy:Pb:Na single crystals

    S.M.; Moses; Kennedy

    2010-01-01

    The variation of the optical absorption (OA) and photoluminescence (PL) spectra with temperature was studied on γ-irradiated CaF2:Dy:Pb:Na single crystals. The OA spectrum showed bands around 2.05, 3.20, 3.82 and 6.20 eV which could be attributed to different sodium associated (SA) colour centres (CCs) such as MNa and RA+ . Heating the crystal indicated the annihilation and formation of different SACCs. The excitation spectrum for the characteristic Dy3+ emission at 2.14 eV immediately after irradiation was...

  11. Dielectric constant/ loss behaviour of high energy 238U ion irradiated polymer liquid crystal

    Dielectric constant/loss behaviour in high energy 238U (11.6 MeV/n) ion irradiated poly (P-hydroxy benzoic acid-co-ethylene terephthalate) PET/ x.PHB (x is the molar concentration) has been investigated. The observations were made at temperature ranging from 20 to 250 degC at the frequencies 120Hz, 1kHz, 10kHz and 100kHz by using Keithley precession LCZ meter. PET rich phase has been affected drastically by high energy heavy ion irradiation as the dielectric constant is suppressed in contrast to sharp increase in dielectric constant between 40 to 100 degC in pristine PET. The appearance of few kinks in the low temperature region due to decomposition of carboxyl group is evident in high energy heavy ion irradiated 0.7 PHB. (author)

  12. Influence of Gamma-Ray Irradiation on Absorption and Fluorescent Spectra of Nd:YAG and Yb:YAG Laser Crystals

    We investigate the influence of gamma-ray irradiation on the absorption and fluorescent spectra of Nd3+:Y3A15O12 (Nd:YAG) and Yb3+:Y3A15O12 (Yb:YAG) crystals grown by the Czochralski method. Two additional absorption (AA) bands induced by gamma-ray irradiation appear at 255nm and 340 nm. The former is contributed due to Fe3+ impurity, the latter is due to Fe2+ ions and F-type colour centres. The intensity of the excitation and emission spectra as well as the fluorescent lifetime of Nd:YAG crystal decrease after the irradiation of 100Mrad gamma-ray In contrast, the same dose irradiation does not impair the fluorescent properties of Yb:YAG crystal. These results indicate that Yb:YAG crystal possesses the advantage over Nd:YAG crystal that has better reliability for applications in harsh radiant environment. (fundamental areas of phenomenology (including applications))

  13. High energy ion irradiation-induced ordered macro-pores in zeolite crystals

    The present study demonstrated the possibility to form a secondary system of parallel macro-pores in zeolite crystals. The secondary pore formation was predetermined by the creation of defect zones in ZSM-5 crystals. A high energy 238U ion beam was employed to form latent tracks in zeolite crystals, which were further subjected to attack with diluted HF solution and thus developed to uniformly sized macro-pores. The selective extraction of material from latent tracks was due to the higher etching velocity of highly agitated zones created by heavy ion bombardment. The combination of complementary methods unambiguously demonstrated the formation of hierarchical zeolite material comprising parallel macro-pores that extended through the entire crystal. The catalytic tests revealed improved activity at retained selectivity in the reaction ofm-xylene conversion. The possibility to control the number of macro-pores per unit of crystal surface and thus the catalytic performance of the material was demonstrated. This model material is expected to bring better understanding to the effect of a secondary pore system in the catalytic performance of hierarchical zeolites obtained by the top-down or bottom-up approach. (authors)

  14. Temperature effects on ion irradiation damage in MgAl2O4 spinel single crystals

    The search for radiation resistant materials, particularly ceramics, for the applications in radiation environments has been an active area of research for the past few decades. Among the most well studied ceramics, stoichiometric magnesium aluminate spinel (MgAl2O4) has been found to be one of the most radiation resistant ceramics. Here, single crystalline samples of (MgAl2O4), oriented, were irradiated at 100K and 670K with 370--400 keV Xe ions to doses of (1--2)x1016 Xe/cm2. The microstructures of irradiated samples were subsequently examined by cross-sectional transmission electron microscope. A uniform layer of amorphous phase was observed on the surface of spinel irradiated at 100K. At the end of the damage range underlying the amorphous layer, a disordered transition layer resided on the undamaged substrate. Both high resolution electron microscopy and microdiffraction revealed that the transition layer retained single crystallinity with epitaxial relationship to the underlying substrate. However, the intensity of reflections in the transition layer was significantly weaker than that of the undamaged spinel. No evidence of amorphization was found in the spinel sample irradiated at 670K to a dose of 2x1016 Xe/cm2. The reflections exhibit only limited diminution in the heavily damaged region. The observation of reduced intensity of reflections or absent reflections suggests that spinel experiences a structural transition from its original cubic phase (a=0.808 nm) to a new cubic phase (a=0.404 nm). A transition sequence from the original phase to a metastable phase and then to an amorphous phase has been observed. The temperature dependence of metastable and amorphous phase formation has revealed that the accumulation efficiency of cation disorder decreases with increasing irradiation temperature due to the enhancement of interstitial-vacancy recombination

  15. Modification of the crystal structure of gadolinium gallium garnet by helium ion irradiation

    The structure of gadolinium gallium garnet (GGG) single crystals before and after implantation by He+ ions has been investigated using high-resolution X-ray diffraction methods and the generalized dynamic theory of X-ray scattering. The main types of growth defects in GGG single crystals and radiation-induced defects in the ion-implanted layer have been determined. It is established that the concentration of dislocation loops in the GGG surface layer modified by ion implantation increases and their radius decreases with an increase in the implantation dose

  16. Vertical Liquid Crystal Orientation on Amorphous Tantalum Pentoxide Surfaces Depending on Anisotropic Dipole-Dipole Interaction via Ion Beam Irradiation

    Lee, Jong-Jin; Kim, Hyung-Jun; Kang, Young-Gu; Kim, Young-Hwan; Park, Hong-Gyu; Kim, Byoung-Yong; Seo, Dae-Shik

    2011-03-01

    We achieved vertically aligned (VA) liquid crystals (LCs) on amorphous tantalum pentoxide (Ta2O5) alignment films deposited by radio frequency (rf) magnetron sputtering using ion beam (IB) irradiation. By analyzing measurements by X-ray photoelectron spectroscopy (XPS), we confirmed the bond breaking, as detected from the O 1s spectra, which caused an isotropic dipole-dipole interaction between the LC molecules and the Ta2O5 alignment film to uniformly align the vertical LC molecular orientation as a function of IB energy density. Moreover, by examining the electro-optical (EO) characteristics of the Ta2O5 surfaces compared with those of the polyimide (PI) alignment layer, we confirmed that Ta2O5 has a low threshold voltage and a low power consumption when used as an LC alignment layer.

  17. CH3xxx13CO2 pairs in irradiated single crystals of CH313CO2Lix2D20

    The CH3 radical trapped in irradiated single crystals of CH313CO2Lix2D2O has been found to interact with a 13CO2 molecule, which is formed from the C--C bond breakage as a counterpart. The 13C superhyperfine coupling tensor was determined to be (-4.0, -3.3, -3.5) G. The 13CO2 molecule is located in the direction of the unpaired electron orbital of CH3 with the molecular axis perpendicular to it. The spectrum arising from the electron excess center CH313CO22- was also detected together with the CH3 radical. Our results indicate that the CH3xxx13CO2 pair is essentially a positive hole center formed from one electron loss followed by the C--C bond breakage

  18. Defects creation under UV irradiation of PbWO.sub.4./sub. crystals

    Boháček, Pavel; Fabeni, P.; Krasnikov, A.; Nikl, Martin; Pazzi, G.P.; Susini, C.; Zazubovich, S.

    2006-01-01

    Roč. 119, 1-4 (2006), s. 164-167. ISSN 0144-8420 Institutional research plan: CEZ:AV0Z10100521 Keywords : defects * doping * single crystals * scintillators Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.446, year: 2006

  19. FREE RADICAL ELIMINATION IN IRRADIATED UHMWPE THROUGH CRYSTAL MOBILITY IN PHASE TRANSITION TO THE HEXAGONAL PHASE

    Oral, Ebru; Beckos, Christine Godleski; Muratoglu, Orhun K.

    2008-01-01

    Ultra-high molecular weight polyethylene (UHMWPE) is radiation cross-linked to decrease wear in total joint applications. Irradiation decreases the strength of UHMWPE and introduces residual free radicals, which can cause oxidation in the long-term. We advanced a method eliminating the free radicals without a reduction in strength. UHMWPE exhibits a hexagonal phase at high pressure and temperature, where chain mobility in the crystalline phase is increased, leading to the formation of extende...

  20. Damage creation in silicon single crystals irradiated with 200 keV/atom Aun+ clusters

    Silicon wafers of (1 0 0) orientation were irradiated with Aun cluster beams (1≤n≤7) produced by the 2.5 MV Van de Graaff accelerator of the Institut de Physique Nucleaire de Lyon equipped with a liquid metal source. The incident energy was of 200 keV per gold atom, which corresponds to a slowing-down mainly governed by elastic processes (nuclear energy loss of Au+ ions: 3 keV nm-1). All the irradiations were performed at room temperature with fluences up to 5x1014 Au (at. cm-2). The typical beam currents varied from 1.5 nA for Au+ down to 20 pA for Au7+. The radiation-induced disorder was measured by means of Rutherford backscattering spectrometry in channeling geometry (RBS-C), using a 4He+ beam accelerated at 2 MV. From the fluence evolution of the lattice disorder at the target surface, we evidence that polyatomic projectiles produce more defects per incident atom than single Au+ ions. As an example we measured damage cross-sections per incident Au atom of 12.5 and 2.7 nm2 for Au7+ and Au+ projectiles, respectively. This cluster effect was ascribed to the high density of nuclear energy deposited within the cascade. Transmission electron microscopy (TEM) was performed on samples irradiated at low fluences (109 at. cm-2) in order to visualize each projectile impact

  1. Neutron-diffraction studies of the crystal structure and the color enhancement in γ-irradiated tourmaline

    Maneewong, Apichate; Seong, Baek Seok; Shin, Eun Joo; Kim, Jeong Seog; Kajornrith, Varavuth

    2016-01-01

    Tourmaline gemstones have an extremely complex composition and show great variety in color. Most color centers are related to transition-metal ions. Oxidation/reduction of these ions is known to be related with the color enhancement of tourmaline caused by gamma-ray ( γ)-irradiation and/or thermal treatment. However, the current understanding of the microscopic structure of the color centers remains weak. In this work, γ-irradiation was performed on three types of tourmaline gemstones to enhance the colors of the gemstones: two pink from Afghanistan and one green from Nigeria. All three samples were irradiated at 600 and 800 kGy. Their crystal structural and chemical behaviors have been investigated by using a Rietveld refinement analysis of neutron diffraction data, Energy Dispersive X-ray Fluorescence (EDXRF), Ultraviolet-visible Spectroscopy (UV-Vis) and X-ray Photoelectron Spectroscopy (XPS), and the results were compared with data obtained for samples in the natural state. Pink tourmaline of a high number of Mn ions (T2, 0.24 wt%) showed significant improvement in the quality of the pink color (rubellite) after irradiation of 800 kGy while the pink tourmaline of low MnO content (T1, 0.08 wt%) showed color adulteration. Pink color enhancement in T2, responding to darker pink, was associated with increases in the two absorption bands, one peaking at 396 and the other at 522 nm, after irradiation. These absorption bands are ascribed to d-d transitions of divalent manganese. T1 with color enhancement due to oxidation of Mn2+ showed a slightly larger distance. The green tourmaline containing much higher amounts of both Mn (T3) and Fe ions, 2.59 wt% and 5.7 wt%, respectively, changed to a yellow color after irradiation at 800 kGy. The refined structural parameters of this sample revealed distortions in the Z site. The distance decreased from 2.033 to 2.0192 Å. In addition, the unit-cell parameter was decreased after irradiation. The color change in T3 is ascribed

  2. Defect creation under UV irradiation of CsI:Pb crystals in Pb 2+ -induced absorption bands investigated by luminescence methods

    Babin, V.; Kalder, K.; Krasnikov, A.; Nikl, Martin; Nitsch, Karel; Zazubovich, S.

    2002-01-01

    Roč. 234, č. 2 (2002), s. 689-700. ISSN 0370-1972 Grant ostatní: NATO(XX) SfP 973510 Institutional research plan: CEZ:AV0Z1010914 Keywords : CsI:Pb crystal * luminescence * thermoluminescence * defect creation * UV irradiation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.930, year: 2002

  3. Tritium release behavior from neutron-irradiated Li{sub 2}TiO{sub 3} single crystal

    Tanifuji, Takaaki; Yamaki, Daiju; Noda, Kenji [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Nasu, Shoichi

    1998-03-01

    Li{sub 2}TiO{sub 3} single-crystals with various size (1-2mm) were used as specimens. After the irradiation up to 4 x 10{sup 18} n/cm{sup 2} with thermal neutrons in JRR-2, tritium release from the Li{sub 2}TiO{sub 3} specimens in isothermal heating tests was continuously measured with a proportional counter. The tritium release in the range from 625K to 1373K seems to be controlled by bulk diffusion. The tritium diffusion coefficient (D{sub T}) in Li{sub 2}TiO{sub 3} was evaluated to be D{sub T}(cm{sup 2}/sec) = 0.100exp(-104(kJ/mol)/RT), 625Kirradiated with thermal neutrons up to 2 x 10{sup 19} n/cm{sup 2}. It indicates that the tritium release performance of Li{sub 2}TiO{sub 3} is essentially good as Li{sub 2}O. (author)

  4. Effect of 520 MeV Kr{sup 20+} ion irradiation on the critical current density of Bi-2212 single crystals

    Terai, Takayuki; Ito, Yasuyuki [Tokyo Univ. (Japan). Faculty of Engineering; Kishio, Kouji

    1996-10-01

    Change in magnetic properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+y} (Bi-2212) single crystals due to Kr{sup 20+} ion irradiation is reported, focused on critical current density and irreversibility magnetic field. The Bi-2212 single crystal specimens (3x3x0.3 mm{sup 3}) were prepared by the floating zone method. Each specimen was irradiated with 520 MeV Kr{sup 20+} ions of 10{sup 10}-10{sup 11} cm{sup -2} in the fluence. Magnetic hysteresis was measured at 4.2K-60K with a vibrating sample magnetometer before and after irradiation. Very large enhancement was observed in critical current density and irreversibility magnetic field above 20K. (author)

  5. ESR study of the CH2ClCO radical at 77 K in x-irradiated chloroacetamide crystals

    X-irradiation of chloroacetamide crystals at 77 K yields at least two radicals which are not stable near 300 K. One of these give rise to a four line ESR spectrum due to two nonequivalent protons with the principal hyperfine tensor components for H (1) equal to 268.4, 260.3, and 256.1 MHz and for H (2) equal to 129.9, 109.7, and 109.9 MHz. The principal g values are g/sub max/=2.0674, g/sub int/=2.0144, and g/sub min/=1.9909. Comparing the corresponding direction cosines to selected molecular directions obtained from an x-ray crystal structure as well as deuteration studies suggests the species to be the π-radical CH2ClCO. The unpaired electron is largely distributed between the oxygen and carbon 2p orbitals whose symmetry axis lies perpendicular to the CCO plane. Crystallographically, the chlorine atom lies nearly in the CCO plane and does not give rise to any resolvable ESR hyperfine couplings. The second radical gives rise to a complex ESR spectrum which has been tentatively assigned as due to xCH2Cl. This radical decays upon warming above 100 K with the resultant formation of CHClCONH2

  6. Fabrication of well ordered Zn nanorod arrays by ion irradiation method at room temperature and effect on crystal orientations

    Highly oriented and densely packed one-dimensional (1D) polycrystalline Zn nanorods were fabricated on zinc plate without any catalyst at room temperature by bombardment with obliquely incident Ar+ ion via ion irradiation method. The sputtered surfaces were fully covered with Zn nanostructures with diameter and the length around 60 nm and 1.3 μm, respectively, confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystal orientation of the Zn plate was investigated by electron back scattering pattern method (EBSP). The numerical density and morphology of Zn nanostructures (nanoneedle or nanorods) were found to be 2.1 x 106 to 9 x 106/mm2 depending upon the crystal orientation and the atomic density on different crystallographic faces. (21-bar 1-bar 0) faces of Zn polycrystal tended to form more dense nanostructures compared to (0001-bar) faces. This is because of lower atomic density on (21-bar 1-bar 0) faces in comparison with (0001-bar) faces. This indicates that lower atomic density on any crystallographic faces is favorable to form nanostructure of higher density. The outstanding feature of this growth technique is that it provides a new direction for the controllable growth of desired nanostructures of variable density at room temperature without any catalyst. These well-aligned arrays of Zn nanorods/nanoneedle might be a promising material for the future application in nanodevices.

  7. Properties changes in BeO and LiB3O5 single crystals after He ions irradiation

    The results of study of a creation and accumulation of radiation defects for single crystals BeO and LiB3O5 under irradiation with the 4.6 MeV helium ions produced by cyclotron over the fluence range from 1013 cm-2 have been presented. For the first time we studied the dose behaviour of defects accumulation in BeO and LBO over the broad range of the ion fluences. The radiation induced defects were revealed to be created above the 1015 (LBO) and 1016 cm-2 (BeO) fluences of helium ions. Properties of these defects were studied in detail by the use of electron spin resonance and optical absorption techniques. The structural models for the defects as well as mechanisms of their creation are discussed. Analysis of the crystals BeO through the use of the Rutherford back scattering revealed a change in distribution of the non-controlled tungsten impurity over the near-surface region

  8. Radiation damage induced in Al2O3 single crystal sequentially irradiated with reactor neutrons and 90 MeV Xe ions

    Zirour, H.; Izerrouken, M.; Sari, A.

    2016-06-01

    The present investigation reports the effect of 90 MeV Xe ion irradiation on neutron irradiated Al2O3 single crystals. Three irradiation experiments were performed, with neutrons only, 90 MeV Xe ions only and with neutrons followed by 90 MeV Xe ions. Neutron and 90 MeV Xe ion irradiations were performed at NUR research reactor, Algiers, Algeria and at GANIL accelerator, Caen, France respectively. After irradiation, the radiation damage was investigated by Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), optical absorption measurements, and X-ray diffraction (XRD) techniques. Raman technique revealed that the concentration of the defects formed in Al2O3 samples subsequently irradiated with neutrons and 90 MeV Xe ions is lower than that formed in Al2O3 samples which were irradiated only with neutrons. This reveals the occurrence of ionization-induced recovery of the neutron damage. Furthermore, as revealed by XRD analysis, a new peak is appeared at about 2θ = 38.03° after irradiation at high fluence (>3 × 1013 Xe/cm2). It can be assigned to the formation of new lattice plane.

  9. Crack nucleation in ion beam irradiated magnesium oxide and sapphire crystals

    Monocrystals of magnesium oxide and sapphire have been subjected to ion implantation with 86 keV Si- ions to a dose of 5x1016 cm-2 and with 3 MeV H+ ions to a dose of 4.8x1017 cm-2 prior to thermal stress testing in plasma. Fracture and deformation characteristics of the surface layer were measured in ion implanted and unimplanted samples using optical and scanning electron microscopy. Ion implantation is shown to modify the near-surface structure of samples by introducing damage, which makes crack nucleation easier under the applied stress. The effect of ion dose on the thermal stress resistance is investigated and the critical doses which produce a noticeable change in the stress resistance is determined for sapphire crystals. In comparison with 86 keV- Si ions the high energy implantation of sapphire and magnesium oxide crystals with 3 MeV H+ ions results in the formation of large-scale defects, which produce the low density crack system and cause a considerable reduction in the resistance to damage. Fracture mechanics principles are applied to evaluate the size of the implantation-induced microcracks which is shown to be comparable with the ion range and the damage range in the crystals tested. Possible mechanisms of crack nucleation for a low and high energy ion implantation are discussed

  10. The influence of crystal structure on ion-irradiation tolerance in the Sm(x)Yb(2-x)TiO5 series

    Aughterson, R. D.; Lumpkin, G. R.; de los Reyes, M.; Gault, B.; Baldo, P.; Ryan, E.; Whittle, K. R.; Smith, K. L.; Cairney, J. M.

    2016-04-01

    his ion-irradiation study covers the four major crystal structure types in the Ln(2)TiO(5) series (Ln = lanthanide), namely orthorhombic Pnma, hexagonal P63/mmc, cubic (pyrochlore-like) Fd-3m and cubic (fluorite-like) Fm-3m. This is the first systematic examination of the complete Ln(2)TiO(5) crystal system and the first reported examination of the hexagonal structure. A series of samples, based on the stoichiometry Sm(x)Yb(2-x)TiO5 (where x = 2, 1.4, 1, 0.6, and 0) have been irradiated using 1 MeV Kr2+ ions and characterised in-situ using a transmission electron microscope. Two quantities are used to define ion-irradiation tolerance: critical dose of amorphisation (D-c), which is the irradiating ion dose required for a crystalline to amorphous transition, and the critical temperature (T-c), above which the sample cannot be rendered amorphous by ion irradiation. The structure type plus elements of bonding are correlated to ion-irradiation tolerance. The cubic phases, Yb2TiO5 and Sm0.6Yb1.4TiO5, were found to be the most radiation tolerant, with Tc values of 479 and 697 K respectively. The improved radiation tolerance with a change in symmetry to cubic is consistent with previous studies of similar compounds.

  11. Development of high quality single crystal nanostructures using proton beam irradiation

    By using proton implantations, we have demonstrated high quality single crystal semiconductors, formation of nanocrystals, and phase modification of metal and insulators. Solid phase growth of thin films using proton implantation. - Solid phase growth of semiconductor thin films using proton implantation. - Recrystalization of amorphous semiconductors using proton implantation Nanocrystals formation with phase modification of insulators using proton implantation. - Recrystalization and phase modification of Al2O3 thin film using proton implantation. Defect analysis and control using proton implanted semiconductors - Study of defect states recovered by proton - Study of defect states generated by proton beam

  12. Optical and thermal bleaching of colour centres in gamma-irradiated sodium chloride crystals

    Long lasting optical bleaching of natural NaCl crystals at room and elevated temperatures has been examined. This process has been found to result in the appearance of some new bands and Z2 and Z3 centre bands. The new bands referred to as Zsub(M), Zsub(N) and Zsub(R) are ascribed to the formation of electron-trapped colour centres related to alcaline earth impurities. The Zsub(M), Zsub(R) and Zsub(N) bands are dichroic after excitation with polarized light. The model of N1 centres is discussed; the impurities of calcium group elements are also considered to be responsible for these centres. The thermal bleaching of coloured NaCl crystals of natural origin results in the destruction of ordinary F-aggregate centres as well as of Zsub(M), Zsub(R) and Zsub(N) ones and in the formation of colloidal centres. The thermal stability of the defects in the series Zsub(M), Zsub(N), Zsub(R) and M, N1, R is virtually the same. (author)

  13. Optical spectroscopy and imaging of colour centres in lithium fluoride crystals and thin films irradiated by 3 MeV proton beams

    Piccinini, M., E-mail: massimo.piccinini@enea.it; Ambrosini, F.; Ampollini, A.; Carpanese, M.; Picardi, L.; Ronsivalle, C.; Bonfigli, F.; Libera, S.; Vincenti, M.A.; Montereali, R.M.

    2014-05-01

    Lithium fluoride is a well-known dosimeter material and it is currently under investigation also for high-resolution radiation imaging detectors based on colour centre photoluminescence. In order to extend their applications, proton beams of 3 MeV energy, produced by a linear accelerator, were used to irradiate LiF crystals and thin films in the fluence range of 10{sup 10}–10{sup 15} protons/cm{sup 2}. The irradiation induces the formation of colour centres, mainly the primary F centre and the aggregate F{sub 2} and F{sub 3}{sup +} defects, which are stable at room temperature. By optical pumping in the blue spectral region, the F{sub 2} and F{sub 3}{sup +} centres emit broad photoluminescence bands in the visible spectral range. By conventional fluorescence microscopy, the integrated photoluminescence intensity was carefully measured in LiF crystals and thin films as a function of the irradiation fluence: a linear optical response was obtained in a large range of fluence, which is dependent on the used LiF samples. Colour centres concentrations were estimated in LiF crystals by optical absorption spectroscopy. It was possible to record the transversal proton beam intensity profile by acquiring the photoluminescence image of the irradiated spots on LiF films.

  14. Fast crystallization of amorphous Gd{sub 2}Zr{sub 2}O{sub 7} induced by thermally activated electron-beam irradiation

    Huang, Zhangyi; Qi, Jianqi, E-mail: qijianqi@scu.edu.cn; Zhou, Li; Feng, Zhao; Yu, Xiaohe [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Gong, Yichao [College of Materials Science and Engineering, Sichuan University, Chengdu 610064 (China); Yang, Mao; Wei, Nian [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Key Laboratory of High Energy Density Physics of Ministry of Education, Sichuan University, Chengdu 610064 (China); Shi, Qiwu [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); College of Materials Science and Engineering, Sichuan University, Chengdu 610064 (China); Lu, Tiecheng, E-mail: lutiecheng@scu.edu.cn [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Laboratory of High Energy Density Physics of Ministry of Education, Sichuan University, Chengdu 610064 (China)

    2015-12-07

    We investigate the ionization and displacement effects of an electron-beam (e-beam) on amorphous Gd{sub 2}Zr{sub 2}O{sub 7} synthesized by the co-precipitation and calcination methods. The as-received amorphous specimens were irradiated under electron beams at different energies (80 keV, 120 keV, and 2 MeV) and then characterized by X-ray diffraction and transmission electron microscopy. A metastable fluorite phase was observed in nanocrystalline Gd{sub 2}Zr{sub 2}O{sub 7} and is proposed to arise from the relatively lower surface and interface energy compared with the pyrochlore phase. Fast crystallization could be induced by 120 keV e-beam irradiation (beam current = 0.47 mA/cm{sup 2}). The crystallization occurred on the nanoscale upon ionization irradiation at 400 °C after a dose of less than 10{sup 17} electrons/cm{sup 2}. Under e-beam irradiation, the activation energy for the grain growth process was approximately 10 kJ/mol, but the activation energy was 135 kJ/mol by calcination in a furnace. The thermally activated ionization process was considered the fast crystallization mechanism.

  15. A photoluminescence study of excitonic grade CuInSe2 single crystals irradiated with 6 MeV electrons

    High-quality single crystals of CuInSe2 with near-stoichiometric elemental compositions were irradiated with 6 MeV electrons, at doses from 1015 to 3 × 1018 cm−2, and studied using photoluminescence (PL) at temperatures from 4.2 to 300 K. Before irradiation, the photoluminescence spectra reveal a number of sharp and well resolved lines associated with free- and bound-excitons. The spectra also show broader bands relating to free-to-bound transitions and their phonon replicas in the lower energy region below 1.0 eV. The irradiation with 6 MeV electrons reduces the intensity of the free- and the majority of the bound-exciton peaks. Such a reduction can be seen for doses above 1016 cm−2. The irradiation induces new PL lines at 1.0215 eV and 0.9909 eV and also enhances the intensity of the lines at 1.0325 and 1.0102 eV present in the photoluminescence spectra before the irradiation. Two broad bands at 0.902 and 0.972 eV, respectively, are tentatively associated with two acceptor-type defects: namely, interstitial selenium (Sei) and copper on indium site (CuIn). After irradiation, these become more intense suggesting an increase in the concentration of these defects due to irradiation

  16. Radiationless decay, fission and fusion of excitons in irradiated molecular crystals

    The creation and evolution of excited states in ionizing particle tracks were investigated. The passage of high energy ionizing particles in molecular crystals results in the formation of highly excited states which energy is generally above the molecular ionization potential. The theory of non radiative transitions, which describes the transitions from the highly excited states to the lowest singlet and triplet excitons S1 and T1 is developed. Among these non radiative transitions, the fission of singlet excitons into two singlet or triplet excitons of lower energies is studied experimentally. These results and a kinematics study of the S1 and T1 excitons in ionizing particle tracks were used to get a complete description of the scintillation. These results are in good agreement with the experimental measurements on the scintillation

  17. A single-crystal proton ENDOR study of the ClO3 centre in γ-irradiated barium perchlorate at 120 K

    Hyperfine coupling tensors for 24 protons have been determined from electron nuclear double resonance (ENDOR) measurements of the C1O3 centre trapped in γ-irradiated single crystals of barium perchlorate trihydrate at 120 K. The tensors have small isotropic components and their dipolar components are close to axial so that their interpretation in the point-dipole approximation to reconstruct the proton geometry in the vicinity of the trapped radical is justifiable. The model thus obtained indicates that there is no severe distortion of the crystal structure in the immediate vicinity of the trapped radicals. There are two chemically identical but ENDOR-distinguishable sites related by a reflection in the a1a2 plane of the hexagonal crystal. The observation supports the assignment of the P63/m space group to the crystal. (author)

  18. Charge dynamics of MgO single crystals subjected to KeV electron irradiation

    Boughariou, A.; Blaise, G.; Braga, D.; Kallel, A.

    2004-04-01

    A scanning electron microscope has been equipped to study the fundamental aspects of charge trapping in insulating materials, by measuring the secondary electron emission (SEE) yield σ with a high precision (a few percent), as a function of energy, electron current density, and dose. The intrinsic secondary electron emission yield σ0 of uncharged MgO single crystals annealed at 1000 °C, 2 h, has been studied at four energies 1.1, 5, 15, and 30 keV on three different crystal orientations (100), (110), and (111). At low energies (1.1 and 5 keV) σ0 depends on the crystalline orientation wheras at high energies (30 keV) no differentiation occurs. It is shown that the value of the second crossover energy E2, for which the intrinsic SEE yield σ0=1, is extremely delicate to measure with precision. It is about 15 keV±500 eV for the (100) orientation, 13.5 keV±500 eV for the (110), and 18.5 keV±500 eV for the (111) one. At low current density J⩽105 pA/cm2, the variation of σ with the injected dose makes possible the observation of a self-regulated regime characterized by a steady value of the SEE yield σst=1. At low energies 1.1 and 5 keV, there is no current density effects in MgO, but at high energies ≈30 keV, apparent current density effects come from a bad collect of secondary electrons, due to very high negative surface potential. At 30 keV energy, an intense erratic electron exoemission was observed on the MgO (110) orientation annealed at 1500 °C. This phenomenon is the result of a disruptive process similar to flashover, which takes place at the surface of the material.

  19. Effect of low irradiation temperature on the thermoluminescent response of doped crystal NaCl:XCl2 :MnCl2(X=Ca, Cd)

    Production of crystalline materials suitable thermoluminescent properties over a wide range of doses is becoming more important to evaluate different radiation fields. However, the thermoluminescence response and the structure of the glow curves may be modified by the participation of defects to low irradiation temperature. In this work it is analyzed the effect of the irradiation temperature, 77 and 200 K on the thermoluminescence response of crystal NaCl:XCl2:MnCl2 (X=Ca, Cd) doubly doped. The glow curves obtained were analyzed using a deconvolution program of CGCD, and the response linearity was analyzed by supra linearity index. (Author)

  20. Thermally stimulated luminescence studies of x-irradiated L-alanine: Cr3+ single crystals

    Thermally stimulated luminescence studies of x-irradiated L-alanine: Cr3+ have been conducted in the interval 10--300 K. Glow peaks were observed at 42, 60, 72, 148, and 208 K. The 148 K peak has been previously reported, while the one at 208 K was of insufficient intensity to study. Also, the 60 K peak was difficult to analyze due to overlap with the neighboring peaks. Detailed analyses of the 42 and 72 K peaks yielded, respectively, the following parameters: E = 24 meV, s = 5.3 s-1, and l = 1; E = 180 meV, s = 2.4 x 1010 s-1, and l = 2.8, where l is the kinetics order. Identical emission was observed from each peak, characterized by a maximum at 445 nm with FWHM equal to 0.605 eV. A tentative model is presented to explain these results in terms of detrapping and deexcitation via the excited singlet and triplet states

  1. TEM investigation of irradiation damage in single crystal CeO2

    In order to understand the evolution of radiation damage in oxide nuclear fuel, 150-1000 keV Kr ions were implanted into single crystal CeO2, as a simulation of fluorite ceramic UO2, while in situ transmission electron microscopy (TEM) observations were carried out. Two characteristic defect structures were investigated: dislocation/dislocation loops and nano-size gas bubbles. The growth behavior of defect clusters induced by 1 MeV Kr ions up to doses of 5 x 1015 ions/cm2 were followed at 600 deg. C and 800 deg. C. TEM micrographs clearly show the development of defect structures: nucleation of dislocation loops, transformation to extended dislocation lines, and the formation of tangled dislocation networks. The difference in dislocation growth rates at 600 deg. C and 800 deg. C revealed the important role which Ce-vacancies play in the loop formation process. Bubble formation, studied through 150 keV Kr implantations at room temperature and 600 deg. C, might be influenced by either the mobility of metal-vacancies correlated with at threshold temperature or the limitation of gas solubility as a function of temperature.

  2. Electro-optical characteristics of ZrO2 nanoparticle doped liquid crystal on ion-beam irradiated polyimide layer.

    Park, Hong-Gyu; Kim, Hyung-Jun; Kim, Myoung-Seong; Lee, Il-Hwan; Seo, Dae-Shik

    2012-07-01

    It is well known that doping liquid crystals (LCs) with nanoparticles can readily change the physical and electro-optical properties of LC mixture. In this paper, we report on how the electro-optical properties and thermal stability of an LC system were enhanced by dispersing zirconia (ZrO2) nanoparticles in nematic LCs on ion-beam irradiated polyimide layers. Homogeneous LC alignment was achieved and ZrO2/LC mixture was applied in twisted-nematic (TN) mode. The addition of ZrO2 nanoparticles contributed to improvement of electro-optical properties in the TN LC cell by lowering voltage operation and decreasing response time. The TN LC cells with a ZrO2 nanoparticle concentration of 2.0 wt% showed the lowest threshold voltage of 2.0 V and the fastest response time of 15.3 ms. This enhanced electro-optical performance was likely due to van-der waals interactions and the screening effect of the ZrO2 nanoparticles in the LC medium. The thermal stability of the ZrO2/LC mixture was also improved compared to a pristine LC system. PMID:22966615

  3. Thermoluminescence and electron spin resonance studies of x-irradiated L-alanine:Cr3+ single crystals

    Single crystals of x-irradiated L-alanine:Cr3+ have been studied between 90 and 300 K by electron spin resonance (ESR) and thermoluminescence (TL) techniques. Ultraviolet (uv) photobleaching of the Cr3+ electron traps and L-alanine radical centers was also investigated. The results demonstrate that the x-ray generated radical centers can be destroyed by uv-induced electron transport activity, and this destruction follows first order kinetics. Also, the transformation of the primary neutral radical species to a secondary radical in L-alanine was found not to be induced by intermolecular electron transport. The TL glow was determined to proceed by first-order kinetics at a temperature of 160 K with an activation energy of 0.3 eV and a frequency factor of 1.0 x 108 s-1. It is suggested that the TL glow may arise from both the decay of the primary cation radical species in L-alanine and the bleaching of the Cr3+ electron traps, and that the Cr3+ impurity acts to enhance the free radical thermoluminescence

  4. Free radical formation in crystals of 2'-deoxyguanosine 5'-monophosphate irradiated at 15 K: an ESR study

    Radiation-induced radicals in single crystals of 2'-deoxyguanosine 5'-monophosphate (5'-dGMP) at 15 K have been studied by electron spin resonance (ESR) spectroscopy. At low temperatures three radicals were analyzed in detail. The negatively charged pi anion of the guanine base completely dominated the spectra. Weaker resonances were due to an alkoxy radical with the spin density in the C3'-O3' region of the sugar moiety as well as another sugar-centered radical. The anion rapidly decayed upon exposure to uv light at 15 K or by annealing above 25 K. In both cases no successor radical was observed. The second sugar-centered radical decays at 200 K with a concomitant appearance of the resonance from the C8 H-addition radical. By annealing at 295 K the latter resonance was the only one observed. After irradiation at 295 K, however, an additional resonance from a sugar-centered radical, which has been analyzed previously by B. Rakvin and J. N. Herak (Radiat. Res. 88, 240-250 (1981)) was observed. A reinvestigation of this resonance was performed

  5. Strong shift of the irreversibility line in bismuth and thallium based 2212 HTSC single crystals irradiated by 6. 0 GeV Pb ions

    Hardy, V.; Provost, J.; Groult, D.; Hervieu, M.; Raveau, B. (Lab. CRISMAT-ISMRa, Univ. de Caen, 14 (France)); Durcok, S.; Pollert, E. (Inst. of Physics, CSAV, Prague (Czechoslovakia)); Frison, J.C.; Chaminade, J.P.; Pouchard, M. (Lab. de Chimie du Solide, 33 - Talence (France))

    1992-02-01

    Bi-2212 (Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}) and Tl-2212 (Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8})-type single crystals have been irradiated by 6.0 GeV Pb ions. The irradiation results in the creation of tubes of amorphized material (latent tracks) which extend throughout the whole thickness of the crystals. Such induced defects act as efficient pinning centers and lead to unusual large changes in the magnetic hysteresis loops. A strong shift of the irreversibility line to high fields and temperatures and a significant change of its shape are also reported for both compounds, demonstrating that pinning effects have to be taken into account to describe the onset of the FLL motion. (orig.).

  6. Strong shift of the irreversibility line in bismuth and thallium based 2212 HTSC single crystals irradiated by 6.0 GeV Pb ions

    Bi-2212 (Bi2Sr2CaCu2O8) and Tl-2212 (Tl2Ba2CaCu2O8)-type single crystals have been irradiated by 6.0 GeV Pb ions. The irradiation results in the creation of tubes of amorphized material (latent tracks) which extend throughout the whole thickness of the crystals. Such induced defects act as efficient pinning centers and lead to unusual large changes in the magnetic hysteresis loops. A strong shift of the irreversibility line to high fields and temperatures and a significant change of its shape are also reported for both compounds, demonstrating that pinning effects have to be taken into account to describe the onset of the FLL motion. (orig.)

  7. Photo-alignment of low-molecular mass nematic liquid crystals on photochemically bifunctional chalcone-epoxy film by irradiation of a linearly polarized UV light

    Photocrosslinkable chalcone-epoxy compound comprising 1,3-bis-(4-hydroxy-phenyl)-propenone was synthesized for fabricating the photo-alignment layer of liquid crystals. Chalcone group was introduced into the main chain unit of the epoxy oligomer. We observed a photodimerization behavior and an optical anisotropy of this material by irradiation of a linearly polarized UV(LP-UV) light. With a trace amount of cationic photo initiator (TRS-HFA), polymerization of epoxy groups was also conducted at the similar wavelength range used for photodimerization . Linearly polarized UV irradiation on the chalcone-epoxy films with cationic photoinitiator induced optical anisotropy of the film and the resultant film can be used for alignment layers for low molecular weight nematic liquid crystals

  8. Effect of irradiation with reactor neutrons and the temperature of subsequent heat treatment on the structure of InP single crystals

    The results of studying the features of the effect of irradiation with fast and full-spectrum reactor neutrons and subsequent heat treatments on the structural characteristics of InP single crystals are reported. It is shown that, in contrast to other III-V semiconductor compounds, the lattice constant decreases in InP as a result of irradiation with neutrons. Fast neutrons make the major contribution to the variation in the lattice constant. The presence of the component of thermal neutrons that give rise to Sn atoms in the material does not bring about any appreciable variation in the lattice constant. Heat treatment of irradiated samples at temperatures as high as 600 deg. C leads to annealing of radiation defects and recovery of the lattice constant; in the samples irradiated with high neutron fluences, the lattice constant becomes even larger than that before irradiation. An analysis of the obtained experimental data made it possible to assume that the decrease in the InP lattice constant as a result of irradiation with neutrons is mainly caused by the introduction of the PIn antisite defects that give rise to an effect similar to that of vacancy-related defects

  9. Teraherts spectra of A3B3C62 crystals under gamma-irradiation

    the crystal, showing strong absorption bands.

  10. Crystallization of fused silica surfaces by ultra-violet laser irradiation

    In recent years, the increased use of high power lasers has created problems in optical elements due to laser damage. The International Organization for Standardization (ISO) describes in a publication ISO 11254 a laser-power resilience (LPR) test which we used to verify that by flattening the glass substrate of an optical element, we could improve the resistance to laser damage. We report on an evaluation of two types of samples of fused silica substrate whose surface roughness differed (Ra = 0.20 nm and Ra = 0.13 nm) using customized on-line laser damage testing. To induce laser damage to samples, we used the fifth harmonic generation from a Nd:YAG pulse laser (wavelength: 213 nm, pulse width: 4 ns, repetition frequency: 20 Hz). Results show that flattening reduced the progression of laser damage in the meta-phase laser damage phase by 1/3 of that without flattening. However, pro-phase laser damage which started at fluence 2.39 J/cm2 was unrelated to surface roughness. To analyze the pro-phase laser damage, we used x-ray diffraction (XRD), Raman spectroscopy, and variable pressure-type scanning electron microscopy (VP-SEM). From XRD data, we observed XRD patterns of cristobalite (111), cristobalite (102), α-quartz (111), and β-quartz (102). Raman spectrum data showed an increase in the three-membered ring vibration (600 cm-1), four-membered ring vibration (490 cm-1), and many-membered ring vibration (450 cm-1, 390 cm-1, and 300 cm-1). We observed patchy crystallized areas on the sample surfaces in the VP-SEM images. Based on these experimental results, we believe that the dominant factors in pro-phase laser damage are their physical properties. Substrate and thin film material must be appropriately selected in producing an optical element with a high level of resilience to laser exposure.

  11. Optical absorption of selenite single crystals subjected to high electric fields and irradiated with X-rays or γ-rays

    Measurements of the optical absorption coefficient of selenite single crystals show two peaks at 236 and 400 nm when plotted as a function of wavelength. These peaks decrease with increasing irradiation time for both γ and X-rays. Subsequent thermal bleaching increases the absorption coefficient at all wavelengths and flattens out the peaks at 1400C and 3300C respectively. The imposition of an a.c. or d.c. field prior to irradiation preserves the thermal bleaching characteristics with an overall increase in absorption coefficient. These effects are attributed to two different types of bond formed by water of crystallization giving rise to the two absorption peaks. Irradiation may destroy some of the bands of loosely bound water molecules near defect regions leading to a decrease in absorption. Thermal bleaching removes water molecules reducing the transparency of the samples, the more strongly bound molecules being removed at the higher temperature. Irradiation after a.c. or d.c. field treatment may introduce more defect regions enabling the removal of more water molecules by bleaching and hence increasing the absorption. (U.K.)

  12. Vortex-glass phase transition and enhanced flux pinning in C4+-irradiated BaFe1.9Ni0.1As2 superconducting single crystals

    We report the effects of C4+-irradiation on the superconducting properties of BaFe1.9Ni0.1As2 single crystal. The BaFe1.9Ni0.1As2 single crystal before and after C4+-irradiation was characterized by magnetic, magneto-transport and magneto-optical techniques over a wide range of magnetic fields (0–13 T) and temperatures (2–200 K). We demonstrate that the C4+-irradiation significantly enhances the in-field critical current density (by a factor of up to 1.5 at 5 K) and induces enhanced flux jumping at 2 K, with only a small degradation (by 0.5 K) of the critical temperature, Tc. The vortex phase diagram describing the evolution of the vortex-glass transition temperature with magnetic field and the upper critical field has been resolved for the C4+-irradiated sample. For temperatures below Tc, the resistivity curves and the pinning potential were found to show good scaling, using a modified model for vortex-liquid resistivity. The vortex state is three dimensional at temperatures lower than a characteristic temperature. Good agreement between the thermally activated flux flow model, which is usually employed to account for the resistivity in the vortex-liquid region, and the modified vortex-liquid model, has been observed. (paper)

  13. Effect of X-ray Irradiation on Indentation Size Effect Behavior and Formation of Cracks for Potassium Zinc Chloride Crystals Doped with Lithium Ions

    Effects of x-beam irradiation with different doses on microhardness and its related physical constants on K2ZnCl4:yLi+ crystals with concentrations, y equals 0.000, 0.34, 0.86, 0.94, 1.13 or 1.29% has been studied. The tests were performed for x-doses from 0.2 kGy up to 1.6 kGy for loads from 20 to 160 g. The variation of hardness on (010) faces of orthorhombic K2ZnCl4:yLi+ crystals with load were studied. The experimental results showed that, the hardness decreased as the x-doses increased. Variation of the microhardness follows the normal ISE trend for low x-doses and un-irradiated crystals, then follows the reverse ISE trend for high x-doses. Analysis of the experimental results revealed that: Indentation size effect can be explained satisfactory by elastic/plastic deformation and proportional specimen resistance models. Brittleness of two cracks system are applicable for characterizing cracks around indentation impression (i.e. radial cracks) and another is (lateral cracks) for K2ZnCl4:yLi+ crystals in the load range 60 -160 g. It is shown that indentation induced microhardness decreases, whereas the length of radial cracks induced on indentation increases with the increase of x-doses

  14. Effect of 120 MeV Au{sup 9+} ion irradiation on structural, optical and dielectric properties of YCa{sub 4}O(BO{sub 3}){sub 3} nonlinear optical crystal

    Kalidasan, M. [Crystal Growth Centre, Anna University, Chennai 600 025 (India); Arun Kumar, R. [Crystal Growth Centre, Anna University, Chennai 600 025 (India); PSG College of Technology, Coimbatore 641 004 (India); Asokan, K. [Inter University Accelerator Centre, New Delhi 110 067 (India); Dhanasekaran, R., E-mail: rdhanasekaran@annauniv.edu [Crystal Growth Centre, Anna University, Chennai 600 025 (India)

    2012-06-01

    Highlights: Black-Right-Pointing-Pointer Yttrium calcium oxy-borate crystals were irradiated with 120 MeV Au{sup 9+} ions. Black-Right-Pointing-Pointer Irradiation was carried out at both ambient and liquid nitrogen temperatures. Black-Right-Pointing-Pointer Effects of irradiation on the crystal were analyzed through various studies. Black-Right-Pointing-Pointer All studies reveal that surface level modification has been created by Au{sup 9+} ions. Black-Right-Pointing-Pointer The radiation induced effects are less pronounced at liquid nitrogen temperature. - Abstract: Yttrium calcium oxy borate (YCOB) is an important nonlinear optical (NLO) crystal belongs to RECOB (RE = Gd, Sm, Nd, Er, La and Y) family of crystals with the general formula RECa{sub 4}O(BO{sub 3}){sub 3}. YCOB is a negative biaxial crystal which crystallizes in the monoclinic structure with non-centrosymmetric space group Cm. In the present work, the flux grown YCOB single crystals were irradiated with various fluences of 120 MeV Au{sup 9+} heavy ions at ambient and at liquid nitrogen (LN{sub 2}) temperatures, respectively. Grazing incidence angle X-ray diffraction (GIXRD) studies of pristine and irradiated crystals confirm the ion induced surface modification. UV-Visible spectral analysis shows that there was a red shift of optical edge of the pristine sample with ion fluence from 10{sup 11} to 10{sup 13} ions/cm{sup 2}. Laser Raman spectrum of YCOB crystal presents the intense band of (BO{sub 3}){sup 3-} modes at 1123 cm{sup -1} and its peak intensity reduces with ion fluence. The dielectric loss and relative permittivity of YCOB crystal show a marked increase with ion irradiation fluence.

  15. Alkoxy radical, RCH2O, as a free radical product in x-irradiated single crystals of nucleosides and nucleotides

    The RCH2O radical is formed in x-irradiated 3'-cytidylic acid (3'CMP), 5-chlorodeoxyuridine (ClUdR), 5-bromodeoxyuridine (BUdR), adenosinexHCl (ARxHCl), and deoxyadenosine monohydrate (AdRxH2O) owing to the net loss of hydrogen from O5/sub prime/ of the primary hydroxylic group. ESR measurements were made between 78 and 100 K on single crystals of 3'CMP, ClUdR, BUdR, and ARxHCl and on polycrystalline AdRxH2O. The range of principal g values is g/sub max/=2.054--2.093, g/sub int/=2.005--2.009, g/sub min/ =1.995--2.000. The range of sum of the isotropic β-hydrogen hyperfine couplings is A/sup β/1/sub iso/ +A/sup β/2/sub iso/=141--156 G. The g tensors and A/sup β//sub iso/ values are used to determine which oxygen nonbonding orbital contains the bulk of the unpaired electron density. The unpaired electron 2p orbital symmetry axis is perpendicular to a plane determined by X(H) xxxO--C. Of the two relevant hydrogen bonds in the undamaged molecule, the X--HxxxO bond remains intact whereas the hydrogen in the O--HxxxY bond is displaced. The equation A/sup β//sub iso/=B0+B2 cos2theta, with B0 =0 and B2=101 +- 13 G describes the dependency of the β-hydrogen hyperfine coupling on the torsion angle theta, between the unpaired electron symmetry axis and the C--H/sub β/ bond of the RCH2O radical. Mechanisms of formation, factors in stabilization, and reactions of decay are discussed

  16. A photoluminescence study of excitonic grade CuInSe{sub 2} single crystals irradiated with 6 MeV electrons

    Yakushev, M. V., E-mail: michael.yakushev@strath.ac.uk [Department of Physics, SUPA, Strathclyde University, G4 0NG Glasgow (United Kingdom); Ural Federal University, Ekaterinburg 620002 (Russian Federation); Institute of Solid State Chemistry of RAS, Ekaterinburg 620990 (Russian Federation); Mudryi, A. V.; Borodavchenko, O. M. [Scientific-Practical Material Research Centre of National Academy of Science of Belarus, 220072 Minsk (Belarus); Volkov, V. A. [Ural Federal University, Ekaterinburg 620002 (Russian Federation); Martin, R. W., E-mail: r.w.martin@strath.ac.uk [Department of Physics, SUPA, Strathclyde University, G4 0NG Glasgow (United Kingdom)

    2015-10-21

    High-quality single crystals of CuInSe{sub 2} with near-stoichiometric elemental compositions were irradiated with 6 MeV electrons, at doses from 10{sup 15} to 3 × 10{sup 18 }cm{sup −2}, and studied using photoluminescence (PL) at temperatures from 4.2 to 300 K. Before irradiation, the photoluminescence spectra reveal a number of sharp and well resolved lines associated with free- and bound-excitons. The spectra also show broader bands relating to free-to-bound transitions and their phonon replicas in the lower energy region below 1.0 eV. The irradiation with 6 MeV electrons reduces the intensity of the free- and the majority of the bound-exciton peaks. Such a reduction can be seen for doses above 10{sup 16 }cm{sup −2}. The irradiation induces new PL lines at 1.0215 eV and 0.9909 eV and also enhances the intensity of the lines at 1.0325 and 1.0102 eV present in the photoluminescence spectra before the irradiation. Two broad bands at 0.902 and 0.972 eV, respectively, are tentatively associated with two acceptor-type defects: namely, interstitial selenium (Se{sub i}) and copper on indium site (Cu{sub In}). After irradiation, these become more intense suggesting an increase in the concentration of these defects due to irradiation.

  17. Optical ridge waveguides in Yb:YAG laser crystal produced by combination of swift carbon ion irradiation and femtosecond laser ablation

    Cheng, Yazhou; Lv, Jinman; Akhmadaliev, Shavkat; Hernández-Palmero, Irene; Romero, Carolina; Vázquez de Aldana, Javier R.; Zhou, Shengqiang; Chen, Feng

    2015-09-01

    We report on the fabrication of optical ridge waveguides in ytterbium-doped yttrium aluminum garnet (Yb:YAG) single crystal by applying swift C5+ ion irradiation and the followed femtosecond laser ablation. The planar waveguide layer is first produced by C5+ ion irradiation and the laser ablation is used to microstructure the planar waveguide surface to construct ridge structures. The lowest propagation loss of the ridge waveguide has been determined to be ~2.1 dB/cm. From the confocal micro-fluorescence and micro-Raman spectra obtained from the waveguide regions, the intensities, positions and widths of the emission-line peaks had no obvious changes with respect to those from the bulks, which indicate that C5+ ion irradiation does not affect the bulk-related properties of the Yb:YAG crystal significantly in the waveguide regions. The results obtained in this work suggest potential applications of the Yb:YAG ridge waveguides as integrated laser sources.

  18. Optical absorption and thermoluminescence of Gd- and Sm-doped CaF2 single crystals irradiated with X-rays

    Optical absorption measurements carried out on CaF2: Gd (0.2 mol%) show that it exhibits an absorption band at 272 nm. X-ray irradiation seems to remove this band but produces two absorption bands at 370 and 540 nm, the absorption in these bands increasing with X-ray dosage. CaF2:Sm (0.2 mol%) shows absorption bands at 240, 300, 412 and 630 nm. X-ray irradiation increases the absorption in these bands except in 412 nm which decreases with X-ray dosage. Partial thermal bleaching experiments bring out interesting changes in the absorption bands; when the X-ray-irradiated CaF2:Gd and CaF2:Sm are heated to 3000C, these crystals seem to attein their original absorption characteristics. Thermoluminescence light output of these samples irradiated with X-rays shows peaks at 107, 177, and 277 degC for CaF2:Gd and at 100, 152 and 244 degC for CaF2:Sm. An attempt is made to explain these results. (author)

  19. Direct observation of gliding dislocations interactions with defects in irradiated niobium single crystals by means of the high voltage electronic microscopy (HVEM)

    The interactions of gliding dislocations with defects in irradiated niobium that result in the formation of dislocations channels. The effects in the mechanical behaviour of [941]- and [441]- oriented Nb single crystals due to oxygen addition, neutron and electron irradiation was observed either by macroscopic deformation in a Instron machine or 'in-situ' deformation in the HVEM-High Voltage Electron Microscope. Some specimens were irradiated at IPNS-Intense Pulsed Neutron Source, at 325 K, with 5 x 1017 n/cm2, others were irradiated with electrons in the HVEM. The interactions between gliding dislocations with clusters point defects and dislocations were observed. The primary mechanism for removal of the clusters by the gliding dislocations was the 'sweeping' of the clusters along with the gliding dislocations. As to the point defects, they were 'swept' by the gliding dislocations and left as aligned loops close to the intersections of the gliding dislocations with the upper and lower specimen surfaces. For the illustration of this phenomena, a schematic drawing was made. The mechanism of 'bowing-out' interaction of dislocations with defect clusters was also observed. The reported anomalous slip observed to operate in the [941]- oriented Nb was also directly observed and a qualitive explanation along with a schematic drawing was proposed. This would explain the softenig observed after the yield stress in the [941]- oriented Nb deformed in the Instron machine. (Author)

  20. Energy loss effect on color center creation in LiF crystals under irradiation with 12C, 14N, 40Ar, 84Kr, and 130Xe ions

    Color center creation in LiF crystals irradiated with 12C, 14N, 40Ar, 84Kr, and 130Xe MeV ions were studied as a function of the absorbed energy (fluence). For light ions (12C, 14N) the saturation of single F centers takes place at higher absorbed energy (5 × 1023 eV/cm3) than that for 40Ar, 84Kr and 130Xe ions (∼1023 eV/cm3). The saturation concentration of F centers for 12C and 14N (2 × 1019 cm−3) is twice of that for the heavier ions. Further irradiation with light ions decreases concentration of F centers, presumably due to aggregation, whereas for heavy ions the saturation concentration remains approximately the same that can be explained by much stronger recombination losses within single tracks

  1. Characteristics of microdomains and microdomain patterns recorded by electron beam irradiation on Y-cut LiNbO{sub 3} crystals

    Kokhanchik, L. S. [Institute of Microelectronics Technology and High Purity Materials of the Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region (Russian Federation); Gainutdinov, R. V.; Volk, T. R., E-mail: volk@ns.crys.ras.ru [Institute of Crystallography of the Russian Academy of Sciences, 119333 Moscow (Russian Federation); Lavrov, S. D. [Moscow State Institute of Radio Engineering, Electronics and Automation, 119454 Moscow (Russian Federation)

    2015-08-21

    We present the results of investigations of planar domain patterns (isolated domains and domain gratings) fabricated by irradiation of the nonpolar Y-surface of LiNbO{sub 3} crystals by an electron beam (EB) incident normally onto the surface. The EB recorded domains were investigated using atomic force microscopy, confocal second harmonic generation microscopy, and chemical etching as an auxiliary method. The dependence of the domain characteristics on irradiation conditions (acceleration voltage U, EB current I, and irradiation time t{sub irr}) were determined. The length L{sub d} of both isolated domains and domain gratings along the polar axis Z grows linearly with t{sub irr} (at U, I = const) with no tending to saturation. The plots L{sub d}(t{sub irr}) obtained for U = 10 and 15 kV are practically identical, whereas the values of L{sub d} for U = 5 kV are essentially lower. The domain thickness T{sub d} along the Y-direction, i.e., the depth of the switched layer grows with acceleration voltage U. These results are discussed in terms of space-charge fields formation arising under EB irradiation of insulators. The linearity of L{sub d}(t{sub irr}) is accounted for by the frontal domain growth via the viscous friction law. The experimental dependence of T{sub d} on U supports the suggestion that the domain thickness is determined by the penetration depth R{sub e} of primary electrons, which in turn is governed by U. The difference in L{sub d}(t{sub irr}) plots for different U is accounted for by different electron emission σ. Indirect evidences of a defect structure modification in a thin surface layer with respect to the crystal bulk are obtained.

  2. Enhanced current density Jc and extended irreversibility in single-crystal Bi2Sr2Ca1Cu2O8 via linear defects from heavy ion irradiation

    Large enhancements in the critical current density Jc were produced in single crystals of the high-temperature superconductor Bi2Sr2Ca1Cu2O8 by irradiation with high energy Sn ions. In addition, the irreversibility line was moved to considerably higher magnetic fields. In contrast with analogous studies on Y1Ba2Cu3O7, there was little, if any, selective pinning when the magnetizing field was applied parallel to the linear, ion-damage-produced tracks

  3. Observed regimes of collective flux creep in proton-irradiated, single-crystal Y-Ba-Cu-O: Dependence on current density

    Flux-creep studies have quantified the time decay of supercurrents in a proton-irradiated YBa2Cu3O7 crystal. We determine the dependence of the characteristic exponent μ (which governs current decay) on current density and magnetic field. The results are compared with collective-creep theory for the case of random pointlike disorder. Observed are predicted regimes of creep with small and large bundles of vortices, indications of single vortex motion, crossovers in current density, and other qualitative consistencies

  4. High-resolution electron microscopy study of electron-irradiation-induced crystalline-to-amorphous transition in α-SiC single crystals

    An electron-irradiation-induced crystalline-to-amorphous (CA) transition in α-SiC has been studied by high-resolution electron microscopy (HREM). The irradiation-produced damage structure was examined as a function of dose of electrons by taking high-resolution maps extending from the unirradiated crystalline region to the completely amorphized region. In the intermediate region between those two regions, that is in the CA transition region, the damage structure was essentially a mixture of crystalline and amorphous phases. The volume fraction of the amorphous phase was found to increase with increasing dose of electrons and no discrete crystalline-amorphous interface was observed in the CA transition region. These facts indicate the heterogeneous and gradual nature of the CA transition. In the transition region close to the unirradiated crystalline region, a sort of fragmentation of the crystal lattice was observed to occur, crystallites with slightly different orientations with respect to the parent crystal were formed owing to the strain around the dispersed local amorphous regions. In the transition region close to the amorphized region, these crystallites were reduced in size and were embedded in an amorphous matrix. This damage structure is the result of the increased volume fraction of the amorphous phase. In the completely amorphized region, no lattice fringes were recognized in the HREM images. The atomistic process of the CA transition is discussed on the basis of the present results and those from previous studies. (Author)

  5. TSD current investigations in pristine and 100 MeV Ni-ion irradiated PET/0.3 PHB polymer liquid crystal

    The dielectric relaxations investigations have been carried out in pristine as well as 100 MeV 58Ni ion irradiated (PELLETRON facility, Nuclear Science Center, New Delhi) PET/0.3 PHB PLC samples. Thermally stimulated depolarization current technique (TSDC) has been employed for this purpose. The plc samples were polarized at 180 deg C under the influence of various polarizing fields following the usual method. Three current maxima are observed around 35deg, 120deg and 155degC which are ascribed as β', β and α transitions. These transitions are mainly due to the fast reacting dipoles of PHB regions, dipolar character due to carbonyl groups in PET rich phase and to the cold crystallization of PET. The results confirm the biphasic nature of this plc. The high energy irradiation influences both β and α transitions. Increase in fluence shifts the β peak as well as α peak towards higher temperature. This confirms that high energy irradiation has not only affected the carbonyl groups but has created new phases. (author)

  6. Evidence for weakly bound electrons in non-irradiated alkane crystals. The electrons as a probe of structural differences in crystals

    Pietrow, M.; Gagos, M.; Misiak, L. E.; Kornarzynski, K.; Szurkowski, J.; Rochowski, P.; Grzegorczyk, M.

    2014-01-01

    It is generally assumed that weakly bound (trapped) electrons in organic solids come only from radiolytical (or photochemical) processes like ionization caused by an excited positron entering the sample. This paper presents an evidence for the presence of these electrons in non-irradiated samples of docosane. We argue that these electrons can be located (trapped) either in interlamellar gaps or in spaces made by non-planar conformers. The electrons from the former ones are bound more weakly t...

  7. Thermal stability of radiation-induced free radicals in γ-irradiated l-alanine single crystals

    Decay of the radiation-induced stable free radicals in l-alanine single crystals and powders at the temperatures from 379 to 476K was examined by electron paramagnetic resonance. For single crystals, the calculated activation energy of the radical decay is 104.3±1.7kJ/mol (i.e. 12 538+/-202K) and the frequency factor lnν0 is 24.1±0.4min-1. The lifetime of the radical in single crystals at 296K is 162 years. The results confirm the long-term stability of the radicals, but the decay was found to be faster in large crystals than in powders

  8. EPR studies of the defect centers in γ-irradiated KH2PO4, NH4H2PO4 and Ba(H2PO4)2 single crystals

    The CrO42- impurity has been found to be very effective in stabilizing a phosphorus oxyradical produced by γ-irradiation at room temperature in KH2PO4 and NH4H2PO4 crystals. A similar radical species can be observed in pure Ba(H2PO4)2 crystals γ-irradiated at room temperature. The observed principal values of the g-factor and the 31P hyperfine splitting indicate that this radical species could be the [PO5]2- or [O3POO]2-. (author)

  9. Material properties of pulsed-laser crystallized Si thin films grown on yttria-stabilized zirconia crystallization-induction layers by two-step irradiation method

    Thi Kieu Lien, Mai; Horita, Susumu

    2016-03-01

    Amorphous Si thin films on yttria-stabilized zirconia (YSZ) layers were crystallized widely in solid phase by the two-step method with a pulsed laser, moving the sample stage. The crystalline quality, impurity diffusion, and electrical properties of the crystallized Si films were investigated. It was found that the crystallinity of the Si thin films was improved and their surface was smooth without an incubation layer at the interface, indicating the uniform crystallinity of Si on YSZ. The diffusion of Zr and Y into the Si thin films was as small as or smaller than the order of 1017 atoms/cm3. We evaluated the electrical properties of carrier concentration and Hall mobility of the Si thin films with/without YSZ layers by using the resistivity and AC Hall effect measurements. The temperature and doping concentration dependences were measured for both undoped and P-doped films. It was found that both the undoped and P-doped Si/YSZ/glass films showed higher mobilities and carrier concentrations (and therefore higher conductivities), which indicate a smaller number of defects, than the Si/glass films. This suggested that the Si film crystallized on the YSZ layer is more suitable for application to electronic devices than the Si film on glass.

  10. Evidence for weakly bound electrons in non-irradiated alkane crystals. The electrons as a probe of structural differences in crystals

    Pietrow, M; Misiak, L E; Kornarzynski, K; Szurkowski, J; Rochowski, P; Grzegorczyk, M

    2014-01-01

    It is generally assumed that weakly bound (trapped) electrons in organic solids come only from radiolytical (or photochemical) processes like ionization caused by an excited positron entering the sample. This paper presents an evidence for the presence of these electrons in non-irradiated samples of docosane. We argue that these electrons can be located (trapped) either in interlamellar gaps or in spaces made by non-planar conformers. The electrons from the former ones are bound more weakly than those from the latter ones. The origin of Vis absorption for the samples is explained. These spectra can be used as a probe indicating differences in the solid structures of hydrocarbons.

  11. Effect of dose rate, temperature and impurity content on the radiation damage in the electron irradiated NaCl crystals

    Dubinko, V.I.; Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den

    2000-01-01

    The dependencies of void formation and radiolytic sodium accumulation on the irradiation dose, dose rate, temperature and impurity content are analyzed within a framework of a theoretical model, which is based on a new mechanism of dislocation climb. The mechanism involves the production of V-F cent

  12. Evidence for weakly bound electrons in non-irradiated alkane crystals: The electrons as a probe of structural differences in crystals

    It is generally assumed that weakly bound (trapped) electrons in organic solids come only from radiolytical (or photochemical) processes like ionization caused by an excited positron entering the sample. This paper presents evidence for the presence of these electrons in non-irradiated samples of docosane. This can be due to the triboelectrification process. We argue that these electrons can be located (trapped) either in interlamellar gaps or in spaces made by non-planar conformers. Electrons from the former ones are bound more weakly than electrons from the latter ones. The origin of Vis absorption for the samples is explained. These spectra can be used as a probe indicating differences in the solid structures of hydrocarbons

  13. Evidence for weakly bound electrons in non-irradiated alkane crystals: The electrons as a probe of structural differences in crystals.

    Pietrow, M; Gagoś, M; Misiak, L E; Kornarzyński, K; Szurkowski, J; Rochowski, P; Grzegorczyk, M

    2015-02-14

    It is generally assumed that weakly bound (trapped) electrons in organic solids come only from radiolytical (or photochemical) processes like ionization caused by an excited positron entering the sample. This paper presents evidence for the presence of these electrons in non-irradiated samples of docosane. This can be due to the triboelectrification process. We argue that these electrons can be located (trapped) either in interlamellar gaps or in spaces made by non-planar conformers. Electrons from the former ones are bound more weakly than electrons from the latter ones. The origin of Vis absorption for the samples is explained. These spectra can be used as a probe indicating differences in the solid structures of hydrocarbons. PMID:25681918

  14. Evidence for weakly bound electrons in non-irradiated alkane crystals: The electrons as a probe of structural differences in crystals

    Pietrow, M., E-mail: mrk@kft.umcs.lublin.pl; Misiak, L. E. [Institute of Physics, M. Curie-Skłodowska University, ul. Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin (Poland); Gagoś, M. [Department of Cell Biology, Institute of Biology and Biochemistry, Maria Curie-Skłodowska University, ul. Akademicka 19, 20-033 Lublin (Poland); Kornarzyński, K. [Department of Physics, University of Life Sciences in Lublin, Akademicka 13, 20-950 Lublin (Poland); Szurkowski, J.; Grzegorczyk, M. [Institute of Experimental Physics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk (Poland); Rochowski, P. [Institute of Experimental Physics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdańsk (Poland); Pomeranian University in Słupsk, Arciszewskiego 22b, 76-200 Słupsk (Poland)

    2015-02-14

    It is generally assumed that weakly bound (trapped) electrons in organic solids come only from radiolytical (or photochemical) processes like ionization caused by an excited positron entering the sample. This paper presents evidence for the presence of these electrons in non-irradiated samples of docosane. This can be due to the triboelectrification process. We argue that these electrons can be located (trapped) either in interlamellar gaps or in spaces made by non-planar conformers. Electrons from the former ones are bound more weakly than electrons from the latter ones. The origin of Vis absorption for the samples is explained. These spectra can be used as a probe indicating differences in the solid structures of hydrocarbons.

  15. Free radicals in L-arginine·HCl·H2O single crystals X-irradiated at 298 K-EPR, ENDOR and DFT studies

    Electron Paramagnetic Resonance (EPR), Electron-Nuclear DOuble Resonance (ENDOR) and ENDOR Induced EPR (EIE) results indicated at least three radicals produced in L-arginine·HCl·H2O single crystals irradiated at 298 K. Radical RI dominated the central portion of the EPR spectra and was identified as the main-chain deamination radical, and Density Function Theory (DFT) calculations indicated that RI has protonated carboxyl group, (H2…OOC)ĊH(CH2)3 NHC(NH2)2+, and the COOH protons are transferred from the hydrogen bonded amino group and guanidyl group in two different neighboring molecules. Radicals RII and RIII were identified respectively as the radicals dehydrogenated at C5, −(OOC)CH(NH3)+(CH2)2ĊHNHC(NH2)2+, and at C2, −(OOC)Ċ(NH3)+(CH2)3NHC(NH2)2+. Two conformations of RII were detected, denoted as RIIa and RIIb, and the conformational differences are mainly due to the different dihedral angles of the two β-protons bonded to C4, which were supported by the modeling calculations for RIIa and RIIb. - Highlights: • Three distinct free radicals formed in X-ray irradiated L-arginine·HCl·H2O single crystals at 298 K were identified. • DFT modeling computations indicated the main-chain deamination radical has protonated carboxyl group. • Two conformations of the radical dehydrogenated at C5 were detected. The conformational differences were analyzed with experimental and computational methods. • The annealing experiments indicated these three radicals are stable radicals

  16. Possibilities of capture of swift bombarding heavy Kr 86 ions with energy EKr=394 MeV and FKA from its into axial channeling regime under irradiation GaAs single crystal

    The results of radiation damage study at GaAs [100] after irradiation by swift heavy 84Kr7+ with energy EKr=394 MeV up to the fluence Φt=5·1012 ion/cm2. The distribution of damage along the projected ranges of ions in crystal was investigated using selective chemical etching of cross-sections. (authors)

  17. Radiation tolerance of a high quality synthetic single crystal chemical vapor deposition diamond detector irradiated by 14.8 MeV neutrons

    Pillon, M.; Angelone, M.; Aielli, G.; Almaviva, S.; Marinelli, Marco; Milani, E.; Prestopino, G.; Tucciarone, A.; Verona, C.; Verona-Rinati, G.

    2008-09-01

    Diamond exhibits many properties such as an outstanding radiation hardness and fast response time both important to design detectors working in extremely radioactive environments. Among the many applications these devices can be used for, there is the development of a fast and radiation hard neutron detector for the next generation of fusion reactors, such as the International Thermonuclear Experimental Reactor project, under construction at Cadarache in France. A technology to routinely produce electronic grade synthetic single crystal diamond detectors was recently developed by our group. One of such detectors, with an energy resolution of 0.9% as measured using an A241m α particle source, has been heavily irradiated with 14.8 MeV neutrons produced by the Frascati Neutron Generator. The modifications of its spectroscopic properties have been studied as a function of the neutron fluence up to 2.0×1014 n/cm2. In the early stage of the irradiation procedure an improvement in the spectroscopic performance of the detector was observed. Subsequently the detection performance remains stable for all the given neutron fluence up to the final one thus assessing a remarkable radiation hardness of the device. The neutron damage in materials has been calculated and compared with the experimental results. This comparison is discussed within the nonionizing energy loss (NIEL) hypothesis, which states that performance degradation is proportional to NIEL.

  18. Investigation of the influence of gamma-irradiation on dielectric properties of the (CH3)2NH2Al(SO4)2*6H2O crystal in the ferroelectric phase transition range

    Influence of gamma irradiation on dielectric permittivity and dielectric losses of the dimethylammoniumaluminiumsulfate (DMAAS) crystal in the ferroelectric phase transition on different frequencies is investigated. Samples were cut out from monocrystals DMAAS as plates in the size 4 on 4 centimeters and thickness of 0.7-0.9 mm. The silver paste was applied the samples surface and they were located in the special holder which fell into nitrogen pairs . Measurement of dielectric permittivity and dielectric losses carried out by a method of continuous cooling - heating with speed 0.5 K/min on frequencies 1 MHz, 0.1, 1, 10 kHz in the temperature range 120-170 K. An gamma-irradiation of samples was carried out from a source cobalt 60 with doze capacity approximately 180 R/sec at room temperature. The irradiation doze collected by consecutive expositions and has made 106, 107, 5*107 R. It is shown that dielectric permittivity and dielectric loss angle decreases under gamma-irradiation. The strong dispersion of dielectric permittivity as in not irradiated as in irradiated crystals is found out

  19. Positive ion emission accompanying UV irradiation of single crystal MgO and NaNO3

    Although MgO is much more resistant to radiolysis by 248-nm photons than NaNO3, the ion emission processes at low fluence have much in common: both materials yield high energy ions (>5 eV kinetic energy) with a strongly nonlinear fluence dependence. The authors report time-of-flight measurements of quadrupole mass-selected Mg+ from polished, single crystal MgO and Na+ from cleaved, single crystal NaNO3. At fluences between 10 and 1,000 mJ/cm2, the Mg+ intensities show a strongly nonlinear fluence dependence which decreases to roughly second order behavior at fluences above 100 mJ/cm2. The Na+ intensities display third or fourth order emission kinetics throughout the experimental range of fluences. The authors attribute these emissions to cations adsorbed atop surface electron traps where the cation is ejected when the underlying trap is photo-ionized. The potential energy of this defect configuration accounts for the observed ion kinetic energies. However, the direct photo-ionization of surface vacancy/adsorbed ion defects with 5 eV photons should not be possible. Thus the authors propose that emission requires the photoionization of nearby electron traps, followed by photo-induced charge transfer to the empty traps. They show that a sequence of single-photon absorption events [involving photo-ionization, charge transfer, and electron retrapping] accounts for the strongly nonlinear fluence dependence

  20. Comparative Study of the Effects of Electron Irradiation and Natural Disorder in Single Crystals of SrFe2(As1-xPx)2 Superconductor (x=0.35)

    Strehlow, C P [Ames Laboratory; Konczykowski, M. [Laboratoire des Solides Irradies; Murphy, J. A. [Ames Laboratory; Teknowijoyo, S. [Ames Laboratory; Cho, K. [Ames Laboratory; Tanatar, M. A. [Ames Laboratory; Kobayashi, T. [Osaka University; Miyasaka, S. [Osaka University; Tajima, S. [Osaka University; Prozorov, Ruslan [Ames Laboratory

    2014-07-01

    The London penetration depth λ(T) was measured in single crystals of a SrFe2(As1-xPx)2 (x=0.35) iron-based superconductor. The influence of disorder on the transition temperature Tc and on λ(T) was investigated. The effects of scattering controlled by the annealing of as-grown crystals was compared with the effects of artificial disorder introduced by 2.5 MeV electron irradiation. The low-temperature behavior of λ(T) can be described by a power-law function Δλ(T)=ATn, with the exponent n close to one in pristine annealed samples, as expected for a superconducting gap with line nodes. Upon electron irradiation with a dose of 1.2×1019 e/cm2, the exponent n increases rapidly, exceeding a dirty limit value of n=2, implying that the nodes in the superconducting gap are accidental and can be lifted by the disorder. The variation of the exponent n with Tc is much stronger in the irradiated crystals compared to the crystals in which disorder was controlled by the annealing of the growth defects. We discuss the results in terms of different influence of different types of disorder on intraband and interband scattering.

  1. Heavy ions irradiation effects on magnetization of Tl sub 2 Ba sub 2 CaCu sub 2 O sub 8 and TlBa sub 2 CaCu sub 2 O sub 7 single crystals

    Hardy, V.; Provost, J.; Groult, D.; Raveau, B. (Lab. CRISMAT-ISMRA, 14 - Caen (France)); Tessler, L.R. (D.F.A.I.F.G.W., Campinas, SP (Brazil)); Frison, J.C.; Chaminade, J.P. (L.C.S., 33 - Talence (France)); Bouffard, S. (CIRIL, 14 - Caen (France))

    1992-04-30

    Magnetization measurements were performed as a function of magnetic field and time Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} and TlBa{sub 2}CaCu{sub 2}O{sub 7} single crystals to study the effects of high energy Xe ion irradiation. The effective pinning energies at 6K and 40K have been evaluated from magnetic relaxation measurements. The activation energies are hardly changed after irradiation. The study of magnetization hysteresis shows that an irradiation fluence of 2x10{sup 11} ions cm{sup -2} enhanced hysteresis at 6K in both crystals. But a fluence of 10{sup 12} ions cm{sup -2} was detrimental for the 2212 sample which is the most sensitive to heavy ion irradiation damage in the Tl-cuprate family. The magnetic hysteresis at 70K after irradiation is more drastically increased than at 6K. This spectacular modification is interpreted by a recovery of the 3D character of the flux line lattice. (orig.).

  2. The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Positive ion emission

    We examine UV laser-induced ion emission from a wide bandgap semiconductor, single-crystal ZnO, at fluences well below both the damage threshold and plasma formation. At fluences below 200 mJ/cm2, we observe only Zn+, and the Zn+ intensity decreases monotonically during exposure. At higher fluences, after an initial decrease, the emission is sustained; in addition O+ and O2+ are observed. We explain: how Zn ions of several eV in energy can be produced on the surface of a semiconductor, how sustained emission can be maintained, and the origin of an anomalous emission of slow Zn+ ions -- the latter is shown to arise from photoionization of atomic Zn, also emitted by this radiation.

  3. Confocal and Atomic Force Microscopies of Color Centers Produced by Ultrashort Laser Irradiation in LiF Crystals

    Courrol, Lilia Coronato; Martinez, Oscar; Samad, Ricardo Elgul; Gomes, Laércio; Ranieri, Izilda Márcia; Baldochi, Sonia Licia; de Freitas, Anderson Zanardi; Junior, Nilson Dias Vieira

    2008-04-01

    We report properties of the spatial and spectral distribution of color centers produced in LiF single crystals by ultrashort high intensity laser pulses (60 fs, 10 GW) using confocal spectral microscopy and atomic force microscopy. We could identify a large amount of F centers that gave rise to aggregates such as F2, F4, F2+ and F3+ distributed in cracked shape brownish areas. We have taken a 3D image using confocal microscopy of the sample (luminescent image) and no difference is observed in the different planes. The atomic force microscopy image clearly shows the presence of defects on the modified surface. The formation of micrometer or sub-micrometer voids, filaments and void strings was observed and related to filamentation process.

  4. Size characterisation of noble-metal nano-crystals formed in sapphire by ion irradiation and subsequent thermal annealing

    Highlights: ► Systematic study on the formation of Ag and Au nano-particles in Al2O3. ► Annealing in a reducing atmosphere, below the metal melting point is more suitable. ► Au nano-particles grow up to 15 nm and Ag nano-particles up to 45 nm in radius. ► Ostwald ripening is the mechanism responsible for the formation of large nanoparticles. ► Optical properties of metallic nano-particles in Al2O3 can be related to their size. - Abstract: Metallic nano-particles embedded in transparent dielectrics are very important for new technological applications because of their unique optical properties. These properties depend strongly on the size and shape of the nano-particles. In order to achieve the synthesis of metallic nano-particles it has been used the technique of ion implantation. This is a very common technique because it allows the control of the depth and concentration of the metallic ions inside the sample, limited mostly by straggling, without introducing other contaminant agents. The purpose of this work was to measure the size of the nano-particles grown under different conditions in Sapphire and its size evolution during the growth process. To achieve this goal, α-Al2O3 single crystals were implanted with Ag or Au ions at room temperature with different fluences (from 2 × 1016 ions/cm2 to 8 × 1016 ions/cm2). Afterwards, the samples were annealed at different temperatures (from 600 °C to 1100 °C) in oxidising, reducing, Ar or N2 atmospheres. We measured the ion depth profile by Rutherford Backscattering Spectroscopy (RBS) and the nano-crystals size distribution by using two methods, the surface plasmon resonance in the optical extinction spectrum and the Transmission Electron Microscopy (TEM).

  5. Relation between the swelling and the disordering in ionic crystals irradiated by fast heavy ions; Relation entre le gonflement et la creation de defauts dans les cristaux ioniques irradies par des ions lourds rapides

    Boccanfuso, M

    2001-12-01

    When fast heavy ions penetrate in matter, they slow down essentially by depositing their energy on the electrons. This can lead to strong electronic excitation densities in the solid and then to structural modifications. In this work, calcium fluoride (CaF{sub 2}) was used to look further into the damage induced by irradiation with fast heavy ions in ionic crystals. Four techniques were mainly employed to characterise this damage. These techniques of analysis are wide angle X-ray diffraction, surface profilometry, Rutherford backscattering spectrometry and UV-visible optical absorption spectroscopy. The results of this work show that CaF{sub 2} answers in a multiple way to the electronic excitations. For stopping powers higher than approximately 5 keV/nm, a polygonization seems to occur. This causes a structural disorder, a swelling of 0.27 % and the formation of fractures in the material. A second damage mechanism is caused above approximately 13 keV/nm and results in a loss of the initial crystalline structure. However, optical centres appear whatever the ion stopping power, which indicates that these defects cannot be the cause of the two above mentioned damage mechanisms. According to a thermal spike model, the two thresholds can be linked to melting and sublimation energy of the material, respectively. (author)

  6. Thermoluminescence of undoped and Mn2+-doped NaF crystals after room-temperature ν-ray irradiation

    The undoped samples exhibit five glow peaks at 60, 105, 145, 175 and 2850C. The 600C peak is tentatively attributed to F' centres, the 105, 175 and 2850C peaks to F centres and the 1450C peak to hole centres. Doped samples exhibit six glow peaks at 85, 106, 145, 177, 230 and 3200C. The 106, 145 and 1770C peaks of doped samples are respectively the same as the 105, 145 and 1750C peaks of the undoped samples, and are explained in a similar fashion. The 85 and 2300C peaks are attributed to F centres and the 3200C peak to hole centres. The TL emission spectra of the doped samples consist of two bands at 410-420 and 570 nm at all temperatures, the 410-420 nm emission being due to the intrinsic luminescence perturbed or allowed by the impurities, and the 570 nm emission being due, at least in the case of the first five peaks, to the host-sensitised secondary luminescence with Mn acting as activator. The emission spectrum observed when irradiated doped samples are excited with 342 nm (F band) light also contains bands at 420 and 570 nm. (author)

  7. Measurements of crystal lattice strain and crystallite size in irradiated UO2 pellet by X-ray diffractometry

    Lattice parameters, crystallite sizes, and nonuniform strains of high-burnup UO2 fuel samples were measured using micro-X-ray diffractometry in order to investigate the effects of grain subdivision and strain distribution between crystallites on the microstructural changes, so-called rim structure formation, in UO2 pellets. The samples were prepared from fuel rods irradiated in commercial reactors, and pellet-averaged burnups of the samples were in the range from 41 to 61 GWd/t. While the lattice parameters of the samples increased linearly in the burnup region up to approximately 70 GWd/t, the lattice parameters slightly decreased and tended to level off above 70 GWd/t. The measured crystallite sizes were in the range from 100 to 200 nm and these were nearly the same as those of the 'recrystallized grains' in the rim structure. The elastic strain energy densities, which were evaluated from the lattice parameters and nonuniform strains, tended to increase with burnup and show two plateaus at burnups of approximately 50 and 70 GWd/t, respectively. The saturation of the measured strain energy density at approximately 50 GWd/t can be attributed to the tangle of accumulated dislocations, and the increase in the strain energy density above 60 GWd/t can be explained by the strain caused by crystallite rotation under the restraint conditions between crystallites. (author)

  8. Thermally stimulated luminescence studies of x-irradiated L-alanine: Cr/sup 3 +/ single crystals

    Cooke, D.W.; Jahan, M.S.

    1983-06-01

    Thermally stimulated luminescence studies of x-irradiated L-alanine: Cr/sup 3 +/ have been conducted in the interval 10--300 K. Glow peaks were observed at 42, 60, 72, 148, and 208 K. The 148 K peak has been previously reported, while the one at 208 K was of insufficient intensity to study. Also, the 60 K peak was difficult to analyze due to overlap with the neighboring peaks. Detailed analyses of the 42 and 72 K peaks yielded, respectively, the following parameters: E = 24 meV, s = 5.3 s/sup -1/, and l = 1; E = 180 meV, s = 2.4 x 10/sup 10/ s/sup -1/, and l = 2.8, where l is the kinetics order. Identical emission was observed from each peak, characterized by a maximum at 445 nm with FWHM equal to 0.605 eV. A tentative model is presented to explain these results in terms of detrapping and deexcitation via the excited singlet and triplet states.

  9. Bose-glass transition in highly anisotropic BSCCO and isotropic (K,Ba)BiO3 heavy ion irradiated single crystals

    The current-voltage characteristics has been investigated by transport measurements in highly anisotropic Bi2Sr2CaCu2O8+δ and isotropic (K,Ba)BiO3 single crystals irradiated in the direction parallel with to c-axis. We show that, for Bphi/10phi (where Bphi is the matching field), the same scaling functions can be used to describe the transition in these two systems emphasizing the universality of this transition. The field and sample-independent critical exponents which were found to be νperpendicular=1.1±0.1, z=5.3±0.2 and α(≡ν///νperpendicular)=2, are in a very good agreement with numerical simulations in the case of strongly screened vortex line interactions. Surprisingly, in (K,Ba)BiO3, the Bose-glass formalism can be used to describe the transport properties up to magnetic fields about as twice as the matching field

  10. Free radical formation in single crystals of 9-methyladenine X-irradiated at 10 K. An electron paramagnetic resonance and electron nuclear double resonance study

    Single crystals of 9-methyladenine were X-irradiated at 10 K and at 65 K and were studied using K-band EPR, ENDOR and field-swept ENDOR (FSE) techniques in the temperature range 10 K to 290 K. Three major radicals are stabilized in 9-methyladenine at 10 K. These are: MA1, the adenine anion, probably protonated at N3; MA2, the species formed by net hydrogen abstraction from the 9-methyl group; and MA3, the radical formed by net hydrogen addition to C8 of the adenine moiety. Radical MA1 decayed at about 80 K, possibly into the C2 H adduct (MA4). The other two species (MA2, MA3) were stable at room temperature. A fifth radical species was clearly present in the EPR spectra at 10 K but was not detectable by ENDOR. This species, which decayed above 200 K (possibly into MA3), remains unidentified. The radical population at room temperature is as described by previous authors. The mechanisms for radical formation in 9-methyladenine are discussed in light of the hydrogen bonding scheme and molecular stacking interactions. 32 refs., 4 figs., 2 tabs

  11. Annealing process of F- and F{sup +}-centers in Al{sub 2}O{sub 3} single crystal induced by fast neutrons irradiation

    Izerrouken, M., E-mail: izerrouken@yahoo.com [Centre de Recherche Nucléaire de Draria, BP.43, Sebala, Draria, Algiers (Algeria); Djouadi, Y. [Université Ferhat Abbas, Faculté des Sciences, Université de Sétif (Algeria); Zirour, H. [Faculté de Physique, Université des Sciences et de la Technologie Houari Boumediene, El-Alia, BP 32, Bab-Ezzouar, Algiers (Algeria)

    2014-01-15

    F and F{sup +} centers were produced in Al{sub 2}O{sub 3} single crystal by fast neutrons (E{sub n} > 1.2 MeV) irradiation at low fluence (4.4 × 10{sup 16} n cm{sup −2}). The evolution of defects intensity as a function of temperature and of time at 493, 623 and 823 K was investigated by UV–visible spectrophotometry technique. It can be concluded from the analysis of isochronal and isothermal annealing data, that the F- and F{sup +}-centers annealing process is complex. At low annealing temperature (<473 K), only F- to F{sup +}-center conversion process takes place. At higher temperature (>493 K) the annealing is due to the superposition of several mechanisms with different activation energies. According to our results, the activation energies needed for both F- and F{sup +}-centers elimination are 0.2, 0.3 and 0.03 eV for temperature range of 300–673 K, 673–873 K and >873 K, respectively.

  12. EPR, ENDOR and DFT study of L-lysine·HCl·2H 2O single crystals X-irradiated at 66 K

    Zhou, Yiying; Nelson, William H.

    2010-04-01

    Electron Paramagnetic Resonance (EPR), Electron-Nuclear DOuble Resonance (ENDOR) and ENDOR-Induced EPR (EIE) results indicated at least three radicals produced in L-lysine·HCl·2H 2O crystals irradiated at 66 K. EPR from radical R1 dominated the spectra and it was identified as the carboxyl anion, (H 2OOĊ) CH (NH 3) + (CH 2) 4 (NH 3) +. Density-Functional Theory (DFT) calculations supported the assignment and indicated that the carboxyl group transformed from planar to a pyramidal configuration following electron trapping. Two small couplings detected from R1 were ascribed to protons transferred to the carboxyl group from neighboring molecules through intermolecular hydrogen bonds. Radical R2 was identified as the product of decarboxylation, ĊH (NH 3) +(CH 2) 4 (NH 3) +. Although it was not possible to obtain R2's α-coupling tensor from the experiment, EPR simulations and DFT calculations provided strong support for the identification. Radical R3 exhibited several β-couplings but could be detected only in one plane and could not be identified.

  13. EPR, ENDOR and DFT study of L-lysine.HCl.2H2O single crystals X-irradiated at 66 K

    Electron Paramagnetic Resonance (EPR), Electron-Nuclear DOuble Resonance (ENDOR) and ENDOR-Induced EPR (EIE) results indicated at least three radicals produced in L-lysine.HCl.2H2O crystals irradiated at 66 K. EPR from radical R1 dominated the spectra and it was identified as the carboxyl anion, (H2OOC) CH (NH3)+ (CH2)4 (NH3)+. Density-Functional Theory (DFT) calculations supported the assignment and indicated that the carboxyl group transformed from planar to a pyramidal configuration following electron trapping. Two small couplings detected from R1 were ascribed to protons transferred to the carboxyl group from neighboring molecules through intermolecular hydrogen bonds. Radical R2 was identified as the product of decarboxylation, CH (NH3)+(CH2)4 (NH3)+. Although it was not possible to obtain R2's α-coupling tensor from the experiment, EPR simulations and DFT calculations provided strong support for the identification. Radical R3 exhibited several β-couplings but could be detected only in one plane and could not be identified.

  14. Space-Selective Precipitation of Ba2TiSi2O8 Crystals in Sm3+-Doped BaO-TiO2-SiO2 Glass by Femtosecond Laser Irradiation

    ZHU Bin; DAI Ye; MA Hong-Liang; LIN Geng; QIU Jian-Rong

    2008-01-01

    The ferroelectric crystal Ba2TiSi2O8 with high second-order optical nonlinearity is precipitated in Sm3+-doped BaO-TiO2-SiO2 glass by a focused 800 nm,250 kHz and 150 fs femtosecond laser irradiation.No apparent blue and red emissions are observed at the beginning,while strong blue emission due to second harmonic generation and red emission due to the f-f transitions of Sm3+ are observed near the focal point of the laser beam after irradiation for 25 s. Micro-Raman spectra confirm that Ba2TiSi2O8 crystalline dots and lines are formed after laser irradiation.The mechanism of the phenomenon is discussed.

  15. Shift of localized surface plasmon resonance by Ar-ion irradiation of Ag–Au bimetallic films deposited on Al{sub 2}O{sub 3} single crystals

    Meng, Xuan [Graduate School of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628 (Japan); Shibayama, Tamaki, E-mail: shiba@qe.eng.hokudai.ac.jp [Center for Advanced Research of Energy and Materials, Faculty of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan); Yu, Ruixuan; Takayanagi, Shinya [Graduate School of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628 (Japan); Watanabe, Seiichi [Center for Advanced Research of Energy and Materials, Faculty of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan)

    2013-11-01

    Effects of Ar-ion induced surface nanostructuring were studied using 100 keV Ar-ion irradiation of 30 nm Ag–Au bimetallic films deposited on Al{sub 2}O{sub 3} single crystals, under irradiation fluences ranging from 5.0 × 10{sup 15} cm{sup −2} to 6.3 × 10{sup 16} cm{sup −2}. Scanning electron microscope was used to study the ion-beam-induced surface nanostructuring. As the irradiation fluence increased, dewetting of the bimetallic films on the Al{sub 2}O{sub 3} substrate was observed, and formation of isolated Ag–Au nanostructures sustained on the substrate were obtained. Next, thermal annealing was performed under high vacuum at 1073 K for 2 h; a layer of photosensitive Ag–Au alloy nanoballs partially embedded in the Al{sub 2}O{sub 3} substrate was obtained when higher fluence irradiation (>3.8 × 10{sup 16} cm{sup −2}) was used. The microstructures of the nanoballs were investigated using a transmission electron microscope, and the nanoballs were found to be single crystals with a FCC structure. In addition, photoabsorption spectra were measured, and localized surface plasmon resonance peaks were observed. With increase in the irradiation fluence, the size of the Ag–Au nanoballs on the substrate decreased, and a blue-shift of the LSPR peaks was observed. Further control of the LSPR frequency over a wide range was achieved by modifying the chemical components, and a red-shift of the LSPR peaks was observed as the Au concentration increased. In summary, ion irradiation is an effective approach toward surface nanostructuring, and the nanocomposites obtained have potential applications in optical devices.

  16. Cascade phonon-assisted trapping of positrons by divacancies in n-FZ-Si(P) single crystals irradiated with 15 MeV protons

    Arutyunov, N. Yu., E-mail: n-arutyunov@yahoo.com [Martin Luther University Halle, Department of Physics, 06120 Halle, Germany and Inst. of Ion-Plasma and Laser Technologies (Inst. of Electronics), 700187 Tashkent (Uzbekistan); Emtsev, V. V.; Oganesyan, G. A. [Ioffe Physico-Technical Institute, 194021 St. Petersburg (Russian Federation); Krause-Rehberg, R.; Kessler, C. [Martin Luther University Halle, Department of Physics, 06120 Halle (Germany); Elsayed, M. [Martin Luther University Halle, Department of Physics, 06120 Halle, Germany and Minia university, Faculty of Science, Physics Department, P.O. box 61519 Minia (Egypt); Kozlovski, V. V. [St. Petersburg State Polytechnic University, 195251 St. Petersburg (Russian Federation)

    2014-02-21

    The trapping of positrons by the radiation defects in moderately doped oxygen-lean n-FZ-Si(P) single crystal irradiated with 15 MeV protons has been investigated in a comparative way using the positron lifetime spectroscopy and Hall effect measurements. The experiments were carried out within a wide temperature interval ranging from 25 K – 29 K to 300 K. The positron trapping rate for divacancies was reconstructed in the course of many-stage isochronal annealing. The concentration and the charged states of divacancies (V{sub 2}{sup −} and V{sub 2}{sup −−}) were estimated. The temperature dependency of the trapping cross section of positrons by the negatively charged divacancies is in a good agreement with the data of calculations based on the assumptions of the cascade phonon-assisted mechanism of exchange of the energy between the positron and acoustic long-wave phonons. Obeying ∼ T{sup −3} law, the cross-section of the trapping of positrons by divacancies changes considerably ranging from ∼1.7×10{sup −12} cm{sup 2} (66 – 100 K) to ∼2×10{sup −14} cm{sup 2} (≈ 250 K). The characteristic length of trapping of the positron by V{sub 2}{sup −−} divacancy was estimated to be l{sub 0}(V{sub 2}{sup −−})≈(3.4±0.2)×10{sup −8} cm.

  17. Radiation-damage-induced defects in quartz. I. Single-crystal W-band EPR study of hole centers in an electron-irradiated quartz

    Nilges, Mark J.; Pan, Yuanming; Mashkovtsev, Rudolf I.

    2008-03-01

    Single-crystal W-band electron paramagnetic resonance (EPR) spectra of an electron-irradiated quartz, measured at room temperature, 110 and 77 K, disclose three previously reported hole centers (#1, G and an ozonide radical). The W-band EPR spectra of these three centers clearly resolve six magnetically nonequivalent sites each, whereas previous X- and Q-band EPR studies reported Centers #1 and the ozonide radical to consist of only three symmetry-related components and interpreted them to reside on twofold symmetry axes in the quartz structure. The calculated g matrices of Center #1 and the ozonide radical show that deviations from twofold symmetry axes are <10°, which are probably attributable to distortion related to neighboring charge compensating ions. The W-band EPR spectra of Center G not only result in improved g matrices but also allow quantitative determination of the nuclear hyperfine ( A) and quadrupole ( P) matrices of its 27Al hyperfine structure that was incompletely resolved before. In particular, the g-maximum and g-minimum principal axes of Center G are approximately along two pairs of O-O edges of the SiO4 tetrahedron, while the unique A principal axis is approximately along a Si-Si direction. These new spin-Hamiltonian parameters suggest that Center G most likely involves trapping of a hole between two oxygen atoms related to a silicon vacancy and stabilized by an Al3+ ion in the neighboring tetrahedron (hence an O{2/n-}-Al3+ defect, where n is either 1 or 3).

  18. Optical waveguide properties of Ca{sub 0.4}Ba{sub 0.6}Nb{sub 2}O{sub 6} crystal formed by oxygen ion irradiation

    Wang, Tie-Jun; Zhou, Yu-Fan; Yu, Xiao-Fei; Liu, Tao; Zhang, Lian; Song, Hong-Lian; Qiao, Mei; Wang, Xue-Lin, E-mail: xuelinwang@sdu.edu.cn

    2015-07-01

    We report the fabrication of a planar optical waveguide in a Ca{sub 0.4}Ba{sub 0.6}Nb{sub 2}O{sub 6} crystal by irradiation with 6.0 MeV oxygen ions. We measured the guiding mode by the prism-coupling method at 633 nm and 1539 nm. The near-field intensity distributions were measured by the end-face coupling setup at a wavelength of 633 nm. The reflectivity calculation method (RCM) was used for reconstructing refractive index profiles. SRIM was used to simulate the electronic and nuclear stopping power caused by oxygen ion irradiation, and the finite-difference beam propagation method (FD-BPM) was used to simulate the near-field intensity distributions. Micro-Raman spectra were measured at room temperature in air to study the differences between the substrate and waveguide region.

  19. EPR study of gamma irradiated N-methyl taurine (C 3H 9NO 3S) and sodium hydrogen sulphate monohydrate (NaHSO 3·H 2O) single crystals

    Yıldırım, İlkay; Karabulut, Bünyamin

    2011-03-01

    EPR study of gamma irradiated C 3H 9NO 3S and NaHSO 3.H 2O single crystals have been carried out at room temperature. There is one site for the radicals in C 3H 9NO 3S and two magnetically distinct sites for the radicals in NaHSO 3. The observed lines in the EPR spectra have been attributed to the species of SO3- and RH radicals for N-methyl taurine, and to the SO3- and OH radicals for sodium hydrogen sulfate monohydrate single crystals. The principal values of the g for SO3-, the hyperfine values of RH and OH proton splitting have been calculated and discussed.

  20. Photodegradation of crystal violet in TiO2 suspensions using UV-vis irradiation from two microwave-powered electrodeless discharge lamps (EDL-2): Products, mechanism and feasibility

    Aqueous crystal violet (CV) solutions containing P25-TiO2 photocatalyst were irradiated with ultraviolet-visible (UV-vis) light from two microwave-powered electrodeless discharge lamps (EDL-2). The results demonstrated that approximately 94.4% of CV was effectively removed after 3 min of irradiation, with a pseudo-first order kinetic constant of 0.838 min-1. According to 32 kinds of products, a five-step degradation pathway of CV was proposed. Further investigations showed that (1) three kinds of N-demethylated products and 4-dimethylaminobenzophenone (DLBP) were the main intermediates; (2) malachite green (MG) and leuco-crystal violet could not be generated by N-demethylation and phototransformation reactions, respectively; (3) bis(4-(dimethylamino)phenyl)methanone preferentially generated via decomposition of the conjugated structure of CV could be further N-demethylated into DLBP. Moreover, the unique degradation pathways of CV and MG were ascribed to the different substituents on the conjugated structures. Additionally, the cost and kinetic constant of different processes was also evaluated, and the results indicated the feasibility of this method for treatment of CV in field situations.

  1. Irradiation Creep in Graphite

    Ubic, Rick; Butt, Darryl; Windes, William

    2014-03-13

    An understanding of the underlying mechanisms of irradiation creep in graphite material is required to correctly interpret experimental data, explain micromechanical modeling results, and predict whole-core behavior. This project will focus on experimental microscopic data to demonstrate the mechanism of irradiation creep. High-resolution transmission electron microscopy should be able to image both the dislocations in graphite and the irradiation-induced interstitial clusters that pin those dislocations. The team will first prepare and characterize nanoscale samples of virgin nuclear graphite in a transmission electron microscope. Additional samples will be irradiated to varying degrees at the Advanced Test Reactor (ATR) facility and similarly characterized. Researchers will record microstructures and crystal defects and suggest a mechanism for irradiation creep based on the results. In addition, the purchase of a tensile holder for a transmission electron microscope will allow, for the first time, in situ observation of creep behavior on the microstructure and crystallographic defects.

  2. Irradiation-Induced Nanostructures

    Birtcher, R.C.; Ewing, R.C.; Matzke, Hj.; Meldrum, A.; Newcomer, P.P.; Wang, L.M.; Wang, S.X.; Weber, W.J.

    1999-08-09

    This paper summarizes the results of the studies of the irradiation-induced formation of nanostructures, where the injected interstitials from the source of irradiation are not major components of the nanophase. This phenomena has been observed by in situ transmission electron microscopy (TEM) in a number of intermetallic compounds and ceramics during high-energy electron or ion irradiations when the ions completely penetrate through the specimen. Beginning with single crystals, electron or ion irradiation in a certain temperature range may result in nanostructures composed of amorphous domains and nanocrystals with either the original composition and crystal structure or new nanophases formed by decomposition of the target material. The phenomenon has also been observed in natural materials which have suffered irradiation from the decay of constituent radioactive elements and in nuclear reactor fuels which have been irradiated by fission neutrons and other fission products. The mechanisms involved in the process of this nanophase formation are discussed in terms of the evolution of displacement cascades, radiation-induced defect accumulation, radiation-induced segregation and phase decomposition, as well as the competition between irradiation-induced amorphization and recrystallization.

  3. Post-irradiation effects in polyethylenes irradiated under various atmospheres

    If a large amount of polymer free radicals remain trapped after irradiation of polymers, the post-irradiation effects may result in a significant alteration of physical properties during long-term shelf storage and use. In the case of polyethylenes (PEs) some failures are attributed to the post-irradiation oxidative degradation initiated by the reaction of residual free radicals (mainly trapped in crystal phase) with oxygen. Oxidation products such as carbonyl groups act as deep traps and introduce changes in carrier mobility and significant deterioration in the PEs electrical insulating properties. The post-irradiation behaviour of three different PEs, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) was studied; previously, the post-irradiation behaviour of the PEs was investigated after the irradiation in air (Suljovrujic, 2010). In this paper, in order to investigate the influence of different irradiation media on the post-irradiation behaviour, the samples were irradiated in air and nitrogen gas, to an absorbed dose of 300 kGy. The annealing treatment of irradiated PEs, which can substantially reduce the concentration of free radicals, is used in this study, too. Dielectric relaxation behaviour is related to the difference in the initial structure of PEs (such as branching, crystallinity etc.), to the changes induced by irradiation in different media and to the post-irradiation changes induced by storage of the samples in air. Electron spin resonance (ESR), differential scanning calorimetry (DSC), infra-red (IR) spectroscopy and gel measurements were used to determine the changes in the free radical concentration, crystal fraction, oxidation and degree of network formation, respectively. - Highlights: • The post-irradiation behaviour of three different PEs, LDPE, LLDPE and HDPE, was studied. • In order to investigate influence of different irradiation media on post-irradiation behaviour, samples

  4. Optical Properties of Irradiated Yttrium Aluminum Garnet

    The results of investigation of the photoluminescence (PL) and optical absorption of crystals Y3Al5O12(YAG) doped with different concentrations of manganese ions exposed to fast neutron irradiation and electron irradiation are presented. Photoluminescence spectra of YAG before neutron irradiation at T=80 K contain fine lines in orange region of spectrum, ascribed to Mn2+ ions in octahedral position. After irradiation band broadening is observed in the luminescence spectra of garnet crystals. Electron irradiation produced broad band with a complex structure related to Mn4+ ions. Exchange interaction between radiation defect and impurity ions during neutron irradiation and electron irradiation leads to appearance of additional lines and luminescence bands broadening in investigated crystals.

  5. High temperature neutron irradiation of carbon materials

    The radiation change in dimensions and certain properties of carbon structural materials, irradiated at 2100-2300 K by fluence up to 3x1020 neutr/cm2 (E >= 0.18 MeV) is considered. It is established that crystal structure of composite materials and carbon fibers improves as the result of high-temperature irradiation. The crystal lattice parameter decreases, whereas the dimensions of crystals and texture index grow

  6. Spectrometry of the Rutherford backscattering of ions and the Raman scattering of light in GaS single crystals irradiated with 140-keV H{sub 2}{sup +} ions

    Garibov, A. A.; Madatov, R. S., E-mail: msrahim@mail.ru [Azerbaijan National Academy of Sciences, Institute of Radiation Problems (Azerbaijan); Komarov, F. F.; Pilko, V. V. [Belarus State University, RTCCU of “Nanotechnology and Physical Electronics” (Belarus); Mustafayev, Yu. M.; Akhmedov, F. I.; Jakhangirov, M. M. [Azerbaijan National Academy of Sciences, Institute of Radiation Problems (Azerbaijan)

    2015-05-15

    The methods of the Raman scattering of light and Rutherford backscattering are used to study the degree of structural disorder in layered GaS crystals before and after irradiation with 140-keV H{sub 2}{sup +} ions. It is shown that the distribution of the crystal’s components over depth is homogeneous; for doses as high as 5 × 10{sup 15} cm{sup −2}, the stoichiometric composition of the compound’s components is retained. The experimental value of the critical dose for the beginning of amorphization amounts to about 5 × 10{sup 15} cm{sup −2} and is in accordance with the calculated value. The results obtained by the method of the Raman scattering of light confirm conservation of crystalline structure and the start of the amorphization process.

  7. Annealing-induced crystallization of the Er.sub.2./sub.Fe.sub.13.8./sub.B alloy amorphized by irradiation

    Chukalkin, Y.G.; Teplykh, A. E.; Kudrevatykh, N. V.; Bogdanov, S.G.; Choo, K.N.; Lee, S.; Andreev, Alexander V.; Pirogov, A. N.

    2015-01-01

    Roč. 116, č. 3 (2015), s. 242-247. ISSN 0031-918X R&D Projects: GA ČR GAP204/12/0150 Institutional support: RVO:68378271 Keywords : permanent magnets * amorphous state * isochronous annealing * crystallization * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.761, year: 2014

  8. Beam tests of proton-irradiated PbWO$_4$ crystals and evaluation of double-sided read-out technique for mitigation of radiation damage effects

    Lucchini, Marco Toliman

    2016-01-01

    The harsh radiation environment in which detectors will have to operate during the High Luminosity phase of the LHC (HL-LHC) represents a crucial challenge for many calorimeter technologies. In the CMS forward calorimeters, ionizing doses and hadron fluences will reach up to 300 kGy (at a dose rate of 30 Gy/h) and $2\\times10^{14}$ cm$^{-2}$, respectively, at the pseudorapidity region of $\\lvert \\eta\\rvert=2.6$. To evaluate the evolution of the CMS ECAL performance in such conditions, a set of PbWO$_4$ crystals, exposed to 24 GeV protons up to integrated fluences between $2.1\\times10^{13}$ cm$^{-2}$ and $1.3\\times10^{14}$ cm$^{-2}$, has been studied in beam tests. A degradation of the energy resolution and a non-linear response to electron showers are observed in damaged crystals. Direct measurements of the light output from the crystals show the amplitude decreasing and pulse becoming faster as the fluence increases. The evolution of the performance of the PbWO$_4$ crystals has been well understood and parame...

  9. Irradiation-induced displacement of Ag atoms from lattice sites in an Al-0.2% Mg-0.1% Ag crystal

    In irradiated alloys of Al containing approximately 0.1 at% Ag, the backscattering - channelling method shows that Al-Ag dumbells are created by the trapping of Al interstitial atoms at Ag solute atoms. The present results demonstrate that the addition of 0.2 at% Mg to such irradiated alloys retards not only the formation of Al-Ag dumbells during annealing from 30 to 100 K but also their annihilation during annealing from 180 to 240 K. Al interstitials are released from Mg traps at 100 to 160 K, causing further trapping at Ag atoms. Approximately 70% of the Ag atoms return to lattice sites at approximately 200 K (stage III) (compared with 100% in the Al-0.1% Ag alloys) and the remainder return to lattice sites at approximately 260 K. These results favour migration of Al-Ag dumbells rather than vacancies during stage III annealing. (author)

  10. Lattice damage and compositional changes in Xe ion irradiated InxGa1-xN (x = 0.32-1.0) single crystals

    Zhang, Limin; Jiang, Weilin; Dissanayake, Amila C.; Peng, Jinxin; Ai, Wensi; Zhang, Jiandong; Zhu, Zihua; Wang, Tieshan; Shutthanandan, V.

    2016-06-27

    Lattice disorder and compositional changes in InxGa1-xN (x=0.32, 0.47, 0.7, 0.8 and 1.0) films on GaN/Al2O3 substrates, induced by room-temperature irradiation of 5 MeV Xe ions, have been investigated using both Rutherford backscattering spectrometry under ion-channeling conditions and time-of-flight secondary ion mass spectrometry. The results show that for a fluence of 3E13 cm-2, the relative level of lattice disorder in InxGa1-xN increases monotonically from 59% to 90% with increasing indium concentration x from 0.32 to 0.7; a further increase in x up to 1.0 leads to little increase in the disorder level. In contrast to Ga-rich InxGa1-xN (x=0.32 and 0.47), significant volume swelling of up to ~25% accompanied with oxidation in In-rich InxGa1-xN (x=0.7, 0.8 and 1.0) is observed. In addition, irradiation-induced atomic mixing occurs at the interface of In-rich InxGa1-xN and GaN. The results from this study indicate an extreme susceptibility of the high In-content InxGa1-xN to heavy-ion irradiation, and suggest that cautions must be exercised in applying ion-implantation techniques to these materials at room temperature. Further studies of the irradiation behavior at elevated temperatures are warranted.

  11. A defect density-based constitutive crystal plasticity framework for modeling the plastic deformation of Fe-Cr-Al cladding alloys subsequent to irradiation

    It is essential to understand the deformation behavior of these Fe-Cr-Al alloys, in order to be able to develop models for predicting their mechanical response under varied loading conditions. Interaction of dislocations with the radiation-induced defects governs the crystallographic deformation mechanisms. A crystal plasticity framework is employed to model these mechanisms in Fe-Cr-Al alloys. This work builds on a previously developed defect density-based crystal plasticity model for bcc metals and alloys, with necessary modifications made to account for the defect substructure observed in Fe-Cr-Al alloys. The model is implemented in a Visco-Plastic Self Consistent (VPSC) framework, to predict the mechanical behavior under quasi-static loading.

  12. A defect density-based constitutive crystal plasticity framework for modeling the plastic deformation of Fe-Cr-Al cladding alloys subsequent to irradiation

    Patra, Anirban [Los Alamos National Laboratory; Wen, Wei [Los Alamos National Laboratory; Martinez Saez, Enrique [Los Alamos National Laboratory; Tome, Carlos [Los Alamos National Laboratory

    2016-02-05

    It is essential to understand the deformation behavior of these Fe-Cr-Al alloys, in order to be able to develop models for predicting their mechanical response under varied loading conditions. Interaction of dislocations with the radiation-induced defects governs the crystallographic deformation mechanisms. A crystal plasticity framework is employed to model these mechanisms in Fe-Cr-Al alloys. This work builds on a previously developed defect density-based crystal plasticity model for bcc metals and alloys, with necessary modifications made to account for the defect substructure observed in Fe-Cr-Al alloys. The model is implemented in a Visco-Plastic Self Consistent (VPSC) framework, to predict the mechanical behavior under quasi-static loading.

  13. Passivation of the surfaces of single crystal gadolinium molybdate (Gd2(MoO4)3) against attack by hydrofluoric acid by inert ion beam irradiation

    The passivation effect from inert ion beam bombardment has been studied on a ferroelectric surface. The mechanism in these materials may have some additional contributions because of the polarization charges of the domains and the dipole effect (ion beam and surface species) on the surfaces. For these studies Gd2(MoO4)3 (GMO) crystals were selected. Two possible mechanisms of passivation of GMO surfaces when bombarded with ion beams are discussed

  14. A microstructurally-based model for the evolution of irradiation-induced re-crystallization in U-MO monolithic and AL-dispersion fuels

    Full text: In a monolithic U-Mo fuel design, in the absence of substantial interaction product development fuel swelling will be the primary deformation mechanism. Irradiation-induced recrystallization appears to be a general phenomenon in that it has been observed to occur in a variety of nuclear fuel types, e.g. U-x Mo, UO2, and U3O8. The recrystallization process results in sub-micron sized grains that accelerate fission-gas swelling due to the combination of short diffusion distances, increased grain-boundary area per unit volume, and greater intergranular bubble growth rates as compared to that in the grain interior. An expression has been derived for the fission density at which irradiation-induced recrystallization is initiated that is athermal and weakly dependent on fission rate. The initiation of recrystallization is to be distinguished from the subsequent progression and eventual consumption of the original fuel grain. The formulation takes into account the observed microstructural evolution of the fuel, the role of precipitate pinning and fission gas bubbles, the triggering event for recrystallization, as well as the evolution of recrystallization as a function of burnup. The calculated dislocation density, fission gas bubble size distribution, fission density at which recrystallization first appears, and the subsequent progression as a function of burnup are compared to measured quantities. Estimates of fuel swelling for a monolithic U-Mo fuel design are provided. (author)

  15. Transformation of centers of red and infrared luminescence under electron irradiation and annealing of CdS and CdS : Cu single crystals

    The luminescence centers of specially nonalloyed and alloyed with copper CdS monocrystals and their transformation under electron irradiation are studied. The Cu atoms, interacting basically with defects in the cadmium sublattice, form the CuCd centers, responsible for luminescence by the wave lengths λm = 0.98 μm. Transformation of defects complexes, responsible for the bands of green (λm = 0.541 μm), red (λm = 0.72 μm) and infrared (λm = 0.98 μm) luminescence, occurs at the annealing temperature above 50 deg C due to the increase in the mobility of point defects both in the CdS : Cu cadmium and sulfuric sublattices

  16. Frequency Doubling Broadband Light in Multiple Crystals

    The authors compare frequency doubling of broadband light in a single nonlinear crystal with doubling in five crystals with intercrystal temporal walk off compensation, and with doubling in five crystals adjusted for offset phase matching frequencies. Using a plane-wave, dispersive numerical model of frequency doubling they study the bandwidth of the second harmonic and the conversion efficiency as functions of crystal length and fundamental irradiance. For low irradiance the offset phase matching arrangement has lower efficiency than a single crystal of the same total length but gives a broader second harmonic bandwidth. The walk off compensated arrangement gives both higher conversion efficiency and broader bandwidth than a single crystal. At high irradiance, both multicrystal arrangements improve on the single crystal efficiency while maintaining broad bandwidth

  17. Radiation damage by heavy ion irradiation

    Various phenomena caused by heavy ion irradiation are introduced. The experiments concerning this radiation damage are in progress with small size heavy ion accelerators. The accelerated ions are Ar+, Xe+, He+, and Mo+. The samples to be irradiated are Al and Al alloy, Nb and Nb alloy, and W. As the result of heavy ion irradiation, surface sputtering is caused. The rate of sputtering depends on the energy of incident particles, the kinds of particles, and the direction of crystal axis in relation to that of incident particles. Blistering is caused by gaseous atoms in crystals. Usually, the gaseous atoms are injected into the crystals. The phenomenon of blistering proceeds to flaking by further irradiation. Due to these phenomena, the wall of a fusion reactor gets big damage, and the flaked material becomes the impurities in the plasma. Interstitial atom clusters are formed by the atoms ejected from the lattice positions in crystals. (Kato, T.)

  18. Effect of electron irradiation on nanogroove-networked single-crystalline and dendritic polycrystalline platinum nanosheets prepared from lyotropic surfactant liquid-crystal templates

    Using transmission electron microscopy (TEM) electron irradiation effects were studied for nanogroove-network structured single-crystalline and dendritic polycrystalline Pt nanosheets 50-60 nm in size. These two nanosheets with nearly the same average groove-width or dendritic spacing of 1.3-1.4 nm were prepared from the mixed and single surfactant liquid crystalline templates, respectively. On exposure to electron beam for 20 min at the acceleration voltage of 200 kV, the nanogrooved nanosheets were morphologically little affected, but the dendritic ones were transformed into less branched polycrystalline structures with spacings distributed around ∼1.7 nm. The shape transformation of the latter occurred by the combined mechanism of segmental migration and atomic diffusion. These observations indicate that the nanogrooved Pt nanosheets are highly stabilized by the grooved but crystallographically continuous Pt framework, leading to their extremely high thermo-resistance, in marked contrast to the polycrystalline dendritic structures constructed of crystallographically discontinuous linkages of nanoblocks

  19. Food irradiation

    Food irradiation is a promising technology in which food products are exposed to a controlled amount of radiant energy to eliminate disease-causing bacteria. The process can also control parasites and insects, reduce spoilage and inhibit ripening and sprouting. Food irradiation is endorsed by the most important health organisations (WHO, CDC, USDA, FDA, EFSA, etc.) and allowed in nearly 40 Countries. It is to remember that irradiation is not a substitute either for comprehensive food safety programs or for good food-handling practices. Irradiated foods must be labelled with either the statement treated with radiation or treated by irradiation and the international symbol for irradiation, the radura. Some consumer associations suppose negative aspects of irradiation, such as increase of the number of free radicals in food and decrease of antioxidant vitamins that neutralize them

  20. Single- and double energy N+ ion irradiated planar optical waveguides in Er: Tungsten–tellurite oxide glass and sillenite type Bismuth Germanate crystals working up to telecommunications wavelengths

    Ion implantation proved to be a 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 1.55 μm, as they exhibit large stimulated cross sections and broad emission bandwidth. Fabrication of channel waveguides in such a material via N+ ion implantation was reported recently. Sillenite type Bismuth Germanate (BGO) crystals are good nonlinear optical materials. Parameters of waveguide fabrication in both materials via implantation of MeV-energy N+ ions were optimized. First single-energy implantations at 3.5 MeV at various fluences were applied. Waveguide operation up to 1.5 μm was observed in both materials. Then double-energy implantations at a fixed upper energy of 3.5 MeV and lower energies between 2.5 and 3.1 MeV were performed to suppress leaky modes by increasing barrier width. Improvement of waveguide characteristics was found by m-line spectroscopy and spectroscopic ellipsometry

  1. Crystals in the LHC

    Antonella Del Rosso

    2012-01-01

    Bent crystals can be used to deflect charged particle beams. Their use in high-energy accelerators has been investigated for almost 40 years. Recently, a bent crystal was irradiated for the first time in the HiRadMat facility with an extreme particle flux, which crystals would have to withstand in the LHC. The results were very encouraging and confirmed that this technology could play a major role in increasing the beam collimation performance in future upgrades of the machine.   UA9 bent crystal tested with a laser. Charged particles interacting with a bent crystal can be trapped in channelling states and deflected by the atomic planes of the crystal lattice (see box). The use of bent crystals for beam manipulation in particle accelerators is a concept that has been well-assessed. Over the last three decades, a large number of experimental findings have contributed to furthering our knowledge and improving our ability to control crystal-particle interactions. In modern hadron colliders, su...

  2. Rows of Dislocation Loops in Aluminium Irradiated by Aluminium Ions

    Henriksen, L.; Johansen, A.; Koch, J.;

    1967-01-01

    Single-crystal aluminium specimens, irradiated with 50-keV aluminium ions, contain dislocation loops that are arranged in regular rows along <110 > directions. ©1967 The American Institute of Physics......Single-crystal aluminium specimens, irradiated with 50-keV aluminium ions, contain dislocation loops that are arranged in regular rows along <110 > directions. ©1967 The American Institute of Physics...

  3. Pendellosung effect in photonic crystals

    Savo, S; Miletto, C; Andreone, A; Dardano, P; Moretti, L; Mocella, V

    2008-01-01

    At the exit surface of a photonic crystal, the intensity of the diffracted wave can be periodically modulated, showing a maximum in the "positive" (forward diffracted) or in the "negative" (diffracted) direction, depending on the slab thickness. This thickness dependence is a direct result of the so-called Pendellosung phenomenon, consisting of the periodic exchange inside the crystal of the energy between direct and diffracted beams. We report the experimental observation of this effect in the microwave region at about 14 GHz by irradiating 2D photonic crystal slabs of different thickness and detecting the intensity distribution of the electromagnetic field at the exit surface and inside the crystal itself.

  4. Explosive phenomena in heavily irradiated NaCl

    denHartog, HW; Vainshtein, DI; Matthews, GE; Williams, RT

    1997-01-01

    In heavily irradiated NaCl crystals explosive phenomena can be initiated during irradiation or afterwards when samples are heated to temperatures between 100 and 250 degrees C. During irradiation of NaCl Na and Cl-2 precipitates and void structures are produced along with the accumulation of stored

  5. Irradiation damage in lithium ceramics

    The irradiation response of two candidate tritium-breeding materials, LiAlO2 and Li2ZrO3, was investigated using electron irradiation to produce atomic displacements, and EPR and transmission electron microscopy (TEM) to detect damage responses. In a first set of experiments, single crystals and sintered polycrystals of γ-LiAlO2 were irradiated with 2.5 MeV electrons at a temperature of 20 K. EPR measurements made at 4 K on samples kept at 77 K after electron irradiation confirm that paramagnetic defects are created during irradiation, and that most of these defects disappear at about 100 K. TEM observations at room temperature indicate, however, that annealing of these defects does not result in visible defect aggregates. In a second set of experiments, sintered polycrystalline LiAlO2 and Li2ZrO3 samples were thinned to electron transparency and heavily irradiated in situ with 200 keV electrons. In LiAlO2, laths of LiAl5O8 grew intragranularly under irradiation. Li2ZrO3 showed little or no aggregate damage after extensive irradiation near room temperature. (orig.)

  6. Irradiated planets

    We present models for the spectra emitted by irradiated planets and discuss the numerical methods used in the modeling. In addition, we show results of simple 3D calculations that are designed as a first step toward detailed multi-dimensional models of irradiated planets

  7. Food irradiation

    The paper discusses the need for effective and efficient technologies in improving the food handling system. It defines the basic premises for the development of food handling. The application of food irradiation technology is briefly discussed. The paper points out key considerations for the adoption of food irradiation technology in the ASEAN region (author)

  8. Food irradiation

    The author reviews in outline the present status of industrial gamma irradiation plants for food and medical sterilization and in particular lists commercial irradiation plants currently operating in the U.K., considering briefly plant design, efficiency, costs and dose control. (UK)

  9. Irradiation damage

    There is considerable interest in irradiation effects in intermetallic compounds from both the applied and fundamental aspects. Initially, this interest was associated mainly with nuclear reactor programs but it now extends to the fields of ion-beam modification of metals, behaviour of amorphous materials, ion-beam processing of electronic materials, and ion-beam simulations of various kinds. The field of irradiation damage in intermetallic compounds is rapidly expanding, and no attempt will be made in this chapter to cover all of the various aspects. Instead, attention will be focused on some specific areas and, hopefully, through these, some insight will be given into the physical processes involved, the present state of our knowledge, and the challenge of obtaining more comprehensive understanding in the future. The specific areas that will be covered are: point defects in intermetallic compounds; irradiation-enhanced ordering and irradiation-induced disordering of ordered alloys; irradiation-induced amorphization

  10. Food irradiation

    Food irradiation can have a number of beneficial effects, including prevention of sprouting; control of insects, parasites, pathogenic and spoilage bacteria, moulds and yeasts; and sterilization, which enables commodities to be stored for long periods. It is most unlikely that all these potential applications will prove commercially acceptable; the extend to which such acceptance is eventually achieved will be determined by practical and economic considerations. A review of the available scientific literature indicates that food irradiation is a thoroughly tested food technology. Safety studies have so far shown no deleterious effects. Irradiation will help to ensure a safer and more plentiful food supply by extending shelf-life and by inactivating pests and pathogens. As long as requirement for good manufacturing practice are implemented, food irradiation is safe and effective. Possible risks of food irradiation are not basically different from those resulting from misuse of other processing methods, such as canning, freezing and pasteurization. (author)

  11. Irradiation damage

    Howe, L.M

    2000-07-01

    There is considerable interest in irradiation effects in intermetallic compounds from both the applied and fundamental aspects. Initially, this interest was associated mainly with nuclear reactor programs but it now extends to the fields of ion-beam modification of metals, behaviour of amorphous materials, ion-beam processing of electronic materials, and ion-beam simulations of various kinds. The field of irradiation damage in intermetallic compounds is rapidly expanding, and no attempt will be made in this chapter to cover all of the various aspects. Instead, attention will be focused on some specific areas and, hopefully, through these, some insight will be given into the physical processes involved, the present state of our knowledge, and the challenge of obtaining more comprehensive understanding in the future. The specific areas that will be covered are: point defects in intermetallic compounds; irradiation-enhanced ordering and irradiation-induced disordering of ordered alloys; irradiation-induced amorphization.

  12. Thermal Annealing of Paramagnetic Defects Induced by Gamma Irradiation in (NH4)2SO4 and (ND4)2SO4 Single Crystals: Experimental Verification of the Theory of Fletcher and Brown

    In irradiated (NH4)2SO4 And (ND4)2SO4 crystals two paramagnetic species were identified by means of the electron spin resonance method. The g constant of the first radical is 2.014 and of the second 2.020 for the normal hydrogen compound; for the deuterated compound they are 1.996 and 2.0032 respectively. Study of the annealing of the first radical in the 60°-170°C range showed that in this case the kinetics display a single plateau corresponding to a total recombination of the radicals. For each isotherm it was possible to obtain the appropriate equation using the errors function derived by Fletcher and Brown and taking as a model the recombination of initially correlated (and subsequently liberated) pairs by a random-walk process. Agreement between this function and experimental results was obtained after correcting the function by a factor α. The composite annealing curve is in good agreement with the corrected errors function. Using the phenomenological method of Fletcher and Brown for calculating the activation energy we obtained a value of 1.594 eV, corresponding to the first radical in (NH4)2SO4. On the basis of the variation of the diffusion coefficient with temperature we obtained a value of 1.592 eV for the same activation energy. With the Vand- Primack method we obtained 1.45 eV, which is lower than the two preceding values. We concluded that the recombination of correlated pairs by a random-walk process can be used as a model in the form given by the theory if the interaction between the species formed and the lattice is fairly weak; in this way the pairs which are initially correlated can be liberated. (author)

  13. Crystal Meth

    ... for: Navigation Home / Stories of Hope / Crystal meth Crystal meth Story Of Hope By giovanni January 3rd, ... about my drug addiction having to deal with Crystal meth. I am now in recovery and fighting ...

  14. Defect free single crystal thin layer

    Elafandy, Rami Tarek Mahmoud

    2016-01-28

    A gallium nitride film can be a dislocation free single crystal, which can be prepared by irradiating a surface of a substrate and contacting the surface with an etching solution that can selectively etch at dislocations.

  15. Food irradiation

    Food treatment by means of ionizing energy, or irradiation, is an innovative method for its preservation. In order to treat important volumes of food, it is necessary to have industrial irradiation installations. The effect of radiations on food is analyzed in the present special work and a calculus scheme for an Irradiation Plant is proposed, discussing different aspects related to its project and design: ionizing radiation sources, adequate civil work, security and auxiliary systems to the installations, dosimetric methods and financing evaluation methods of the project. Finally, the conceptual design and calculus of an irradiation industrial plant of tubercles is made, based on the actual needs of a specific agricultural zone of our country. (Author)

  16. Fruits irradiation

    The objectives of this project in food irradiation are two-fold, to study the effect of irradiation in prolongation of useful storage life of fruits and to evaluate irradiation as a means of preserving fruits. However radiation is not intended to replace existing preservation processes but may be used in conjunction with current methods such as refrigeration, drying, fermentation etc. In fact radiation should combine with proper storage and packaging techniques in order to ensure maximum benefits. Ripening retardation of fruits by irradiation kinds of fruits: papaya, mango, rambutan, longan and durian. Changes in organoleptic properties of fruit flavor and taste, texture changes by taste panel estimation of significance level of results by statistical mathematical methods, chemical changes determination of climacteric peak in fruits by estimation of carbon dioxide evolution, vitamin C determination by Tillmann's method, carotenoid separation by thin layer chromatography, reducing sugars and acidity determination, volatile components of durian by gas-chromatography

  17. Food irradiation

    The preservation of food using irradiation may replace or be used in combination with traditional or conventional food preservation techniques. Studies have shown that the irradiation technique which uses less energy than other preservation methods is a potential way for reducing post harvest losses. However, economic feasibility among other constraints is the core factor to determine the success of the technique at commercial scale. The need and importance for considering this new technique in Malaysia are discussed here. (author)

  18. Food irradiation

    A worldwide standard on food irradiation was adopted in 1983 by codex Alimentarius Commission of the Joint Food Standard Programme of the Food and Agriculture Organization (FAO) of the United Nations and The World Health Organization (WHO). As a result, 41 countries have approved the use of irradiation for treating one or more food items and the number is increasing. Generally, irradiation is used to: food loses, food spoilage, disinfestation, safety and hygiene. The number of countries which use irradiation for processing food for commercial purposes has been increasing steadily from 19 in 1987 to 33 today. In the frames of the national programme on the application of irradiation for food preservation and hygienization an experimental plant for electron beam processing has been established in Inst. of Nuclear Chemistry and Technology. The plant is equipped with a small research accelerator Pilot (19 MeV, 1 kW) and industrial unit Electronika (10 MeV, 10 kW). On the basis of the research there were performed at different scientific institutions in Poland, health authorities have issued permissions for irradiation for; spices, garlic, onions, mushrooms, potatoes, dry mushrooms and vegetables. (author)

  19. Photoluminescence Spectra of Crystal Pattern Written by Femtosecond Laser Irradiation in Rare-earth-doped BaO-TiO2-SiO2 Glasses%飞秒激光诱导稀土掺杂BaO-TiO2-SiO2玻璃析晶的发光光谱

    朱斌; 戴晔; 马洪良; 张松敏; 林耿; 邱建荣

    2007-01-01

    A focused femtosecond laser with 800 nm, 250 kHz and 150 fs was used to irradiate Tm3+-doped and Eu3+-doped BaO-TiO2-SiO2 glasses. White emissions were observed around the focal point of the femtosecond laser beam at the initial stage of the laser irradiation in both glass samples. A blue emission began to emerge from the irradiation region in Tm3+-doped glass after 20 s irradiation, but both blue and red emissions were observed from the irradiation region in Eu3+-doped glass. It was found from micro-Raman spectra that nonlinear optical crystal Ba2TiSi2O8 were precipitated in both glass samples after the laser irradiation. The mechanisms of the observed phenomena are discussed.%使用聚焦的800 nm,120 fs,1 kHz飞秒激光照射TM3+和Eu3+掺杂的BaO-TiO2-SiO2玻璃.照射开始,TM3+和Eu3+掺杂玻璃均在飞秒激光聚焦附近发出强烈白光.照射20 s后, 掺杂TM3+的玻璃在聚焦附近开始有蓝光发出,但在Eu3+掺杂玻璃同时有蓝光和红光发出.由显微拉曼光谱判定:经过激光的照射后,2种玻璃均有Ba2TiSi2O8晶体析出.

  20. Commercial irradiator

    Commercial irradiation, the treatment of products with gamma radiation principally using a Cobalt-60 source, had its beginnings in Europe and Australia 25 years ago. To date the most successful application of the process is the sterilization of medical products and, for a variety of reasons, gamma sterilization is now becoming dominant in this important field. Many other applications have been evaluated over the years and the most exciting is undoubtedly food irradiation for which there is a vast potential. The commercial feasibility of setting up and irradiation facility is a complex subject and the selection of Cobalt-60 gamma plant depends on a number of technical and economic considerations. The parameters which determine the design and capacity of the optimum plant include throughput, product size and dose requirements; a balance has to be struck between plant flexibility and overall economy. The Ansell irradiators are designed primarily for the sterilization of medical products although some experimental food irradiation has been done, particularly in Australia. (author)

  1. Crystal plasticity study of single crystal tungsten by indentation tests

    Owing to its favorable material properties, tungsten (W) has been studied as a plasma-facing material in fusion reactors. Experiments on W heating in plasma sources and electron beam facilities have shown an intense micro-crack formation at the heated surface and sub-surface. The cracks go deep inside the irradiated sample, and often large distorted areas caused by local plastic deformation are present around the cracks. To interpret the crack-induced microscopic damage evolution process in W, one needs firstly to understand its plasticity on a single grain level, which is referred to as crystal plasticity. In this thesis, the crystal plasticity of single crystal tungsten (SCW) has been studied by spherical and Berkovich indentation tests and the finite element method with a crystal plasticity model. Appropriate values of the material parameters included in the crystal plasticity model are determined by fitting measured load-displacement curves and pile-up profiles with simulated counterparts for spherical indentation. The numerical simulations reveal excellent agreement with experiment. While the load-displacement curves and the deduced indentation hardness exhibit little sensitivity to the indented plane at small indentation depths, the orientation of slip directions within the crystals governs the development of deformation hillocks at the surface. It is found that several factors like friction, indentation depth, active slip systems, misoriented crystal orientation, misoriented sample surface and azimuthal orientation of the indenter can affect the indentation behavior of SCW. The Berkovich indentation test was also used to study the crystal plasticity of SCW after deuterium irradiation. The critical load (pop-in load) for triggering plastic deformation under the indenter is found to depend on the crystallographic orientation. The pop-in loads decrease dramatically after deuterium plasma irradiation for all three investigated crystallographic planes.

  2. Vinca irradiator

    The development programme of the VINCA radiosterilisation centre involves plans for an irradiator capable of working in several ways. Discontinuous operation. The irradiator is loaded for a certain period then runs automatically until the moment of unloading. This method is suitable as long as the treatment capacity is relatively small. Continuous operation with permanent batch loading and unloading carried out either manually or automatically (by means of equipment to be installed later). Otherwise the design of the apparatus is highly conventional. The source is a vertical panel submersible in a pool. The conveyor is of the 'bucket' type, with 4 tiers to each bucket. The batches pass successively through all possible irradiation positions. Transfert into and out of the cell take place through a maze, which also provides access to the cell when the sources are in storage at the bottom of the pool

  3. Crystals in crystals

    Christensen, Claus H.; Schmidt, I.; Carlsson, A.;

    2005-01-01

    the outer surface of the zeolite particles, particularly after thermal treatment. When using mesoporous zeolites, the particles were evenly distributed throughout the mesopore system of the zeolitic support, even after calcination, leading to nanocrystals within mesoporous zeolite single crystals........ As representative examples, a metal (Pt), an alloy (PtSn), and a metal carbide (beta-Mo2C) were supported on conventional and mesoporous zeolite carriers, respectively, and the degree of particle dispersion was compared by TEM imaging. On conventional zeolites, the supported material aggregated on...

  4. Virtual Crystallizer

    Land, T A; Dylla-Spears, R; Thorsness, C B

    2006-08-29

    Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.

  5. Influence of isopropanol on ferroelectric properties of triglycine sulfate crystals

    Milovidova, S. D.; Rogazinskaya, O. V.; Sidorkin, A. S.; Nguen, Kh. T.; Bykova, A. V.

    2015-03-01

    The dielectric and switching properties of triglycine sulfate (TGS) crystals grown from aqua solution with isopropanol have been studied. It has been shown that their behavior has common features with the behavior of the TGS crystals irradiated by X-rays, and also with the TGS crystals doped with L, α-alanine.

  6. Food irradiation

    The colloquium has been held on the occasion of the commissioning of a new linear electron accelerator. The 17 papers presented by the experts give a survey of the present status of food irradiation and related aspects. Every paper has been analysed and prepared for retrieval from the database. (orig.)

  7. Ionic conductivity in irradiated KCL

    The ionic conductivity of X and gamma irradiated KCL single crystals has been studied between room temperature and 600 degree centigree. the radiation induced damage resulting in a decrease of the conductivity heals by thermal annealing in two steps which are at about 350 and 550 degree centigree respectively. It has been found that the radiation induced colour centres are not involved in the observed decrease of the ionic conductivity. However. It has been observed that the effects of quenching and plastic deformation on the conductivity of the samples are very similar to the effect induced by irradiation. It is suggested that, samples radiation induced dislocation loops might cause the ionic conductivity decrease observed in irradiated samples. (Author)

  8. Light-Induced Photorefractive Waveguides in Iron-Doped Lithium Niobate Crystals

    2003-01-01

    Waveguides were fabricated in lithium niobate crystals solely by light irradiation using binary optical masks and SLM-prepared optical masks. Arrayed-waveguides were also obtained by once or twice irradiations of an interferogram of two plane waves.

  9. Food irradiation: An update

    Recent regulatory and commercial activity regarding food irradiation is highlighted. The effects of irradiation, used to kill insects and microorganisms which cause food spoilage, are discussed. Special attention is given to the current regulatory status of food irradiation in the USA; proposed FDA regulation regarding the use of irradiation; pending irradiation legislation in the US Congress; and industrial applications of irradiation

  10. TSEE from aluminas and spinels subjected to Ar+-ion irradiation

    TSEE from Ar+-ion and/or X-ray irradiated alumina and spinel was investigated. A TSEE peak at 150 deg C from X-ray irradiated alumina was suppressed when the alumina was further irradiated by Ar+-ions. A TSEE peak at 300 deg C was observed for Ar+-ion irradiated alumina and was suppressed by the combined effect of Ar+-ion and X-ray irradiations. Only weak TSEE peaks were observed between 250 and 350 deg C in Ar+-ion irradiated spinels. Generally, sprayed spinel specimens showed weaker TSEE peaks than the specimens of a single-crystal spinel. This is attributable to the fact that a plasma-sprayed spinel becomes amorphous more easily than its single crystals. X-ray irradiated spinel single-crystal showed well-defined TSEE when they were not irradiated with Ar+-ions. (author)

  11. Food irradiation

    Various aspects of food treatment by cobalt 60 or caesium 137 gamma radiation are reviewed. One of the main applications of irradiation on foodstuffs lies in its ability to kill micro-organisms, lethal doses being all the lower as the organism concerned is more complex. The effect on parasites is also spectacular. Doses of 200 to 300 krad are recommended to destroy all parasites with no survival period and no resistance phenomenon has ever been observed. The action of gamma radiation on macromolecules was also investigated, the bactericide treatment giving rise to side effects by transformation of food components. Three examples were studied: starch, nucleic acids and a whole food, the egg. The organoleptic aspect of irradiation was examined for different treated foods, then the physical transformations of unpasteurized, heat-pasteurized and radio-pasteurized eggs were compared. The report ends with a brief analysis of the toxicity and conditions of application of the treatment

  12. Food irradiation

    Radiation processing of food is based on irradiation by gamma radiation from a 60Co source or X-ray with energy < 5 MeV or electron beam with energy < 10 MeV. This technique is now completely mastered. About 30 countries use this technique to extend the storage life of food but the total quantity processed is weak, only 30000 tons a year for France. Some countries like Morocco or Tunisia have launched technical programmes about the radiation processing of dates and vegetable oil. These programmes may lead to the creation of a quality label. A joint laboratory between CEA and the Aix-Marseille-3 university is working on the detection of food irradiation in order to fight the fraud. 3 techniques are being investigated: thermoluminescence, electronic paramagnetism resonance and a chemical method. (A.C.)

  13. Endolymphatic irradiation

    The authors analysed the clinical evolution and the result of renal transplantation some years after irradiation in 24 patients (group I) who received endolymphatic 131I as a pre-transplantation immunesuppresive measure. The control group (group II) consisted of 24 non-irradiated patients comparable to group I in age, sex, primary disease, type of donor and immunesuppressive therapy. Significant differences were observed between the two groups regarding such factors a incidence and reversibility of rejection crises in the first 60 post-transplantation days, loss of kidney due to rejection, and dosage of azathioprine. The authors conclude that this method, besides being harmless, has prolonged immunesuppressive action, its administration being advised for receptores of cadaver kidneys, mainly those who show positive cross-match against HLA antigens for painel. (Author)

  14. Cation disorder in high dose neutron irradiated spinel

    The crystal structures of MgAl2O4 spinel single crystals irradiated to high neutron fluences (>5·1026 n/m2 (En>0.1 MeV)), were examined by neutron diffraction. Crystal structure refinement of the highest dose sample indicated that the average scattering strength of the tetrahedral crystal sites decreased by ∼20% while increasing by ∼8% on octahedral sites. Since the neutron scattering length for Mg is considerably larger than for Al, this result is consistent with site exchange between Mg2+ ions on tetrahedral sites and Al3+ ions on octahedral sites. Least squares refinements also indicated that in all irradiated samples, at least 35% of Mg2+ and Al3+ ions in the crystal experienced disordering replacements. This retained dpa on the cation sublattices is the largest retained damage ever measured in an irradiated spinel material

  15. Irradiation effects in glasses

    The deposition of irradiation energy can alter the physical properties of glasses through bond-breaking (energetic photons; fast particles) and atomic displacements (Coulombic and collisional: n0, e, ions). These processes can alter UV-visible optical properties via electron-hole trapping and IR-spectra as a result of network damage. The movement of network atoms results in volume dilatation which change the hardness, refractive index, and dissolution rates. All of these changes can be realized with ion implantation and, in addition, implantation of chemically active species can lead to compound formation in the implanted regions. For this reason, emphasis will be placed on the implantation-induced surface modifications of glasses (mostly silicates). The paper includes crystallization, surface stress, refractive index changes and optoelectronic application and chemical reactivity

  16. Low temperature irradiation of FeB amorphous alloys

    These experiments show that low temperature electron irradiation induce localized defects in the short range order of the amorphous structure. These defects are assumed to be of Frenkel pair type. At low temperature, 2.5 MeV electron irradiation induces an higher concentration of defects in the amorphous than in its crystallized counterpart

  17. Defect recovery in aluminum irradiated with protons at 20 K

    Linderoth, S.; Rajainmäki, H.; Nieminen, R. M.

    1987-01-01

    Aluminum single crystals have been irradiated with 7.0-MeV protons at 20 K. The irradiation damage and its recovery are studied with positron-lifetime spectroscopy between 20 and 500 K. Stage-I recovery is observed at 40 K. At 240 K, loss of freely migrating vacancies is observed. Hydrogen in...

  18. The enigma of cooking salt crystals

    Two Soviet experts, Vladimir Gromov and Valentin Krylov, have discovered an unexpected phenomenon on irradiating cooking salt crystals with electrons. When the crystals are subsequently ground the rate at which they are dissolved increases, but not always. The electrons cause the salt molecules to polarize thus creating an internal electric field. This acts against the double electric layer which is inevitably formed in the part of the solution touching the crystal surface. So, if the permittivity of the solution is much greater than that of the molecules of the crystal, the rate of dissolution is increased, and vice versa. (G.T.H.)

  19. Change of structure and properties of carbon fibers under high temperature neutron irradiation

    Characteristics of crystal structure and macroproperties of VPR-19 carbon fibre treatment under 2300, 2800 and 3100 K after irradiation by 1020 n/cm2 fluence under 2100-220 K are studied. Improvement of crystal structure, carrying away and resputtering of carbon are observed. Interconnection between relative size changes of fibres under irradiation and their macroproperties is shown

  20. Protein Crystallization

    Chernov, Alexander A.

    2005-01-01

    Nucleation, growth and perfection of protein crystals will be overviewed along with crystal mechanical properties. The knowledge is based on experiments using optical and force crystals behave similar to inorganic crystals, though with a difference in orders of magnitude in growing parameters. For example, the low incorporation rate of large biomolecules requires up to 100 times larger supersaturation to grow protein, rather than inorganic crystals. Nucleation is often poorly reproducible, partly because of turbulence accompanying the mixing of precipitant with protein solution. Light scattering reveals fluctuations of molecular cluster size, its growth, surface energies and increased clustering as protein ages. Growth most often occurs layer-by-layer resulting in faceted crystals. New molecular layer on crystal face is terminated by a step where molecular incorporation occurs. Quantitative data on the incorporation rate will be discussed. Rounded crystals with molecularly disordered interfaces will be explained. Defects in crystals compromise the x-ray diffraction resolution crucially needed to find the 3D atomic structure of biomolecules. The defects are immobile so that birth defects stay forever. All lattice defects known for inorganics are revealed in protein crystals. Contribution of molecular conformations to lattice disorder is important, but not studied. This contribution may be enhanced by stress field from other defects. Homologous impurities (e.g., dimers, acetylated molecules) are trapped more willingly by a growing crystal than foreign protein impurities. The trapped impurities induce internal stress eliminated in crystals exceeding a critical size (part of mni for ferritin, lysozyme). Lesser impurities are trapped from stagnant, as compared to the flowing, solution. Freezing may induce much more defects unless quickly amorphysizing intracrystalline water.

  1. Computational crystallization.

    Altan, Irem; Charbonneau, Patrick; Snell, Edward H

    2016-07-15

    Crystallization is a key step in macromolecular structure determination by crystallography. While a robust theoretical treatment of the process is available, due to the complexity of the system, the experimental process is still largely one of trial and error. In this article, efforts in the field are discussed together with a theoretical underpinning using a solubility phase diagram. Prior knowledge has been used to develop tools that computationally predict the crystallization outcome and define mutational approaches that enhance the likelihood of crystallization. For the most part these tools are based on binary outcomes (crystal or no crystal), and the full information contained in an assembly of crystallization screening experiments is lost. The potential of this additional information is illustrated by examples where new biological knowledge can be obtained and where a target can be sub-categorized to predict which class of reagents provides the crystallization driving force. Computational analysis of crystallization requires complete and correctly formatted data. While massive crystallization screening efforts are under way, the data available from many of these studies are sparse. The potential for this data and the steps needed to realize this potential are discussed. PMID:26792536

  2. Food irradiation

    The first part of this data is relative to the study of chemical modifications induced by gamma radiations (60Co, 137Cs) on macromolecules of food and their contaminates with the help of two examples: starch and nucleic acids. Then the second part shows what are the consequences of irradiation on food and their preservation; we make distinction between useful effects (for instance germination inhibition of tubercules, destruction of insects or micro-organisms) and the results which are contingently bad for nutritional, technological and above all toxicologic aspects. The last part is relative to a short restatement of the problems inherent in the industrialization of this treatment

  3. Thermal decomposition of ammonium perchlorate during gamma-ray irradiation

    To assess radiation damage effects in propellants, pyrotechnics, and similar materials, thermal decomposition measurements were made on ammonium perchlorate powders and crystals during gamma-ray irradiation. Gas evolution studies were made on single crystals and powders of ammonium perchlorate, both at room temperature and at 2270C. The results are discussed. (U.S.)

  4. Proton induced radiation damage in fast crystal scintillators

    Yang, Fan; Zhang, Liyuan; Zhu, Ren-Yuan; Kapustinsky, Jon; Nelson, Ron; Wang, Zhehui

    2016-07-01

    This paper reports proton induced radiation damage in fast crystal scintillators. A 20 cm long LYSO crystal, a 15 cm long CeF3 crystal and four liquid scintillator based sealed quartz capillaries were irradiated by 800 MeV protons at Los Alamos up to 3.3 ×1014 p /cm2. Four 1.5 mm thick LYSO plates were irradiated by 24 GeV protons at CERN up to 6.9 ×1015 p /cm2. The results show an excellent radiation hardness of LYSO crystals against charged hadrons.

  5. Crystal Data

    SRD 3 NIST Crystal Data (PC database for purchase)   NIST Crystal Data contains chemical, physical, and crystallographic information useful to characterize more than 237,671 inorganic and organic crystalline materials. The data include the standard cell parameters, cell volume, space group number and symbol, calculated density, chemical formula, chemical name, and classification by chemical type.

  6. Irradiation Induced Microstructure Evolution in Nanostructured Materials: A Review

    Wenbo Liu

    2016-02-01

    Full Text Available Nanostructured (NS materials may have different irradiation resistance from their coarse-grained (CG counterparts. In this review, we focus on the effect of grain boundaries (GBs/interfaces on irradiation induced microstructure evolution and the irradiation tolerance of NS materials under irradiation. The features of void denuded zones (VDZs and the unusual behavior of void formation near GBs/interfaces in metals due to the interactions between GBs/interfaces and irradiation-produced point defects are systematically reviewed. Some experimental results and calculation results show that NS materials have enhanced irradiation resistance, due to their extremely small grain sizes and large volume fractions of GBs/interfaces, which could absorb and annihilate the mobile defects produced during irradiation. However, there is also literature reporting reduced irradiation resistance or even amorphization of NS materials at a lower irradiation dose compared with their bulk counterparts, since the GBs are also characterized by excess energy (compared to that of single crystal materials which could provide a shift in the total free energy that will lead to the amorphization process. The competition of these two effects leads to the different irradiation tolerance of NS materials. The irradiation-induced grain growth is dominated by irradiation temperature, dose, ion flux, character of GBs/interface and nanoprecipitates, although the decrease of grain sizes under irradiation is also observed in some experiments.

  7. Demonstration of finite element simulations in MOOSE using crystallographic models of irradiation hardening and plastic deformation

    Patra, Anirban [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wen, Wei [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Martinez Saez, Enrique [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tome, Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-31

    This report describes the implementation of a crystal plasticity framework (VPSC) for irradiation hardening and plastic deformation in the finite element code, MOOSE. Constitutive models for irradiation hardening and the crystal plasticity framework are described in a previous report [1]. Here we describe these models briefly and then describe an algorithm for interfacing VPSC with finite elements. Example applications of tensile deformation of a dog bone specimen and a 3D pre-irradiated bar specimen performed using MOOSE are demonstrated.

  8. Contribution to knowledge of radiation damage in KCl crystals doped with Sr

    The radiation damages in KCl crystals doped with Sr++ using thermo-ionic technique (ITC) and optical absorption measurements were studied. The variation of the entropy for the dipole jump starting from results reported by several authors was calculated. The irradiation effects with three different exposures were analysed: irradiation with gamma rays; irradiation with fast neutrons added to gamma irradiation; and irradiation with thermal neutrons together with fast neutrons and gamma rays. (Author)

  9. Formation of Elemental Distribution in Glasses by Femtosecond Laser Irradiation

    We report on the fabrication of optical waveguides and the precipitation of nonlinear optical crystals inside glass caused by local element migration with high-repetition femtosecond laser irradiation. Elements that contribute to the high refractive index migrated to the center of the focal region because of the femtosecond laser irradiation in phosphate and borate glasses. Based on this result, we successfully wrote optical waveguides in these glasses, where element distributions were continuously induced along a path traversed by the focal point. Furthermore, we succeeded in space-selective precipitation of nonlinear optical crystals such as β-BBO inside glass by controlling the thermophysical property (crystallization temperature).

  10. Reduction effects in rutile induced by neutron irradiation

    Reduction effect in rutile induced by neutron irradiation and its post-annealing experiment has been investigated. Rutile TiO2 (1 1 0) specimens were cut from the same crystal, and irradiated with high-fluence (1x1019 cm-2) neutron irradiation, then annealed in vacuum and oxidizing atmosphere at different temperatures, respectively. After irradiation, rutile shows deep dark-blue color. After oxidization, it becomes transparent again. But annealed in vacuum, the color of irradiated sample keeps invariable. By means of UV-VIS-IR, XPS, XRD and AFM, samples were investigated before and after irradiation, as well as after annealing. The results show that neutron irradiation induces O2- ions sputtering and Ti4+ ions reduce to Ti3+, Ti2+, even Ti+, and leads to metallization tendency, and the reduction of Ti4+ presents depth-distribution. Especially surface morphology shows step pattern and polycrystalline structure because of insufficiency of O2- ions

  11. Liquid crystal tunable photonic crystal dye laser

    Buss, Thomas; Christiansen, Mads Brøkner; Smith, Cameron; Kristensen, Anders

    2010-01-01

    We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium.

  12. Molecular Crystals

    Wright, John D.

    1995-02-01

    This book describes the chemical and physical structure of molecular crystals, their optical and electronic properties, and the reactions between neighboring molecules in crystals. In the second edition, the author has taken into account research that has undergone extremely rapid development since the first edition was published in 1987. For instance, he gives extensive coverage to the applications of molecular materials in high-technology devices (e.g. optical communications, laser printers, photocopiers, liquid crystal displays, solar cells, and more). There is also an entirely new chapter on the recently discovered Buckminsterfullerene carbon molecule (C60) and organic non-linear optic materials.

  13. Liquid crystal tunable photonic crystal dye laser

    Buss, Thomas; Christiansen, Mads Brøkner; Smith, Cameron;

    2010-01-01

    We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium.......We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium....

  14. Study on thermal properties and crystallization behavior of electron beam irradiated ethylene vinyl acetate (EVA)/waste tyre dust (WTD) blends in the presence of polyethylene graft maleic anhydride (PEgMAH)

    The aim of this article is to show the effects of the electron beam irradiation dose and presence of a compatibiliser on the thermal properties and crystallinity of EVA/WTD blends. The purpose of applying electron beam radiation with doses range 50 to 200 kGy and adding a compatibiliser was to enhance the compatibility of the studied blends and at the same time to investigate the possibility of using this technique in the process of recycling polymeric materials. As the compatibilisers, the polyethylene grafted maleic anhydride (PEgMAH) was utilized, they were added at the amounts of 1-5 phr respectively. The enhancement of thermal properties was accompanied by the following effects, discussed in this article: i) an irradiated EVA/WTD blend at 200kGy was found to improve the thermal properties of EVA, ii) the addition of PEgMAH in EVA/WTD blends and the subsequent irradiation allowed prevention of degradation mechanism. iii) the ΔHf and crystallinity percentage decrease at higher PEgMAH content

  15. Study on thermal properties and crystallization behavior of electron beam irradiated ethylene vinyl acetate (EVA)/waste tyre dust (WTD) blends in the presence of polyethylene graft maleic anhydride (PEgMAH)

    Ramli, Syuhada; Ahmad, S. H. [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan (Malaysia); Ratnam, C. T. [Radiation Processing Technology Division, Malaysian Nuclear Agency (Nuclear Malaysia), Bangi, 43000 Kajang (Malaysia); Athirah, Nurul [School of Materials and Mineral Resources, USM Engineering Campus (Malaysia)

    2013-11-27

    The aim of this article is to show the effects of the electron beam irradiation dose and presence of a compatibiliser on the thermal properties and crystallinity of EVA/WTD blends. The purpose of applying electron beam radiation with doses range 50 to 200 kGy and adding a compatibiliser was to enhance the compatibility of the studied blends and at the same time to investigate the possibility of using this technique in the process of recycling polymeric materials. As the compatibilisers, the polyethylene grafted maleic anhydride (PEgMAH) was utilized, they were added at the amounts of 1-5 phr respectively. The enhancement of thermal properties was accompanied by the following effects, discussed in this article: i) an irradiated EVA/WTD blend at 200kGy was found to improve the thermal properties of EVA, ii) the addition of PEgMAH in EVA/WTD blends and the subsequent irradiation allowed prevention of degradation mechanism. iii) the ΔH{sub f} and crystallinity percentage decrease at higher PEgMAH content.

  16. Study on thermal properties and crystallization behavior of electron beam irradiated ethylene vinyl acetate (EVA)/waste tyre dust (WTD) blends in the presence of polyethylene graft maleic anhydride (PEgMAH)

    Ramli, Syuhada; Ratnam, C. T.; Ahmad, S. H.; Athirah, Nurul

    2013-11-01

    The aim of this article is to show the effects of the electron beam irradiation dose and presence of a compatibiliser on the thermal properties and crystallinity of EVA/WTD blends. The purpose of applying electron beam radiation with doses range 50 to 200 kGy and adding a compatibiliser was to enhance the compatibility of the studied blends and at the same time to investigate the possibility of using this technique in the process of recycling polymeric materials. As the compatibilisers, the polyethylene grafted maleic anhydride (PEgMAH) was utilized, they were added at the amounts of 1-5 phr respectively. The enhancement of thermal properties was accompanied by the following effects, discussed in this article: i) an irradiated EVA/WTD blend at 200kGy was found to improve the thermal properties of EVA, ii) the addition of PEgMAH in EVA/WTD blends and the subsequent irradiation allowed prevention of degradation mechanism. iii) the ΔHf and crystallinity percentage decrease at higher PEgMAH content.

  17. Pulsed laser irradiation of silicon

    Pulsed laser irradiation of silicon was investigated with a ruby laser. Development of heat flow theory made it possible to calculate temperature profiles in silicon during pulsed laser irradiation. Silicon self-diffusion measurements, laser annealing of damage in As implanted silicon, and laser induced doping of single crystal silicon was investigated. A computer programme was writen based on the numerical solution, and was used to calculate the temperature profiles in silicon during irradiation. Radioactive 31Si was used to determine the self-diffusion of silicon in silicon during irradiation. Radioactivity profiles in the silicon sample were measured by anodic oxidation, sequential removal of the formed SiO2 by etching in dilute HF and measurement of the radioactivity left in the sample. Spreading of the radioactive silicon marker started to take place at energy densities above 0.8 Jcm-2, giving an average duffusion coefficient of (5.0 ± 2.7) x 10-8 m2s-1, which is of the order of magnitude expected when melting takes place. The doping of silicon with Sb, Bi and In by laser assisted diffusion was investegated from evaporated layers as well as solutions of these dopants. The threshold energies for doping was 0.6, 0.9 and 0.7 Jcm-2, while maximum dopant concentrations of 2 x 1021, 7 x 1020 and 4 x 1020 respectively was found for Sb, Bi and In. These values exceed the equilibrium solid solubility by orders of magnitude, and can be ascribed to trapping of the dopant atoms, due to the high recrystallization velocities involved. Doping was carried out by placing silicon substrates directly into solutions of SbCl3 and triphenyl antimony. The threshold of solution doping was found to be much greater than doping from evaporated layer. This difference could be ascribed to the much larger absorption coefficient of the laser light in the evaporated layers, as compared to single crystal silicon

  18. Pulsed laser irradiation of silicon

    Pulsed laser irradiation of silicon was investigated with a ruby laser, having a pulse width of 30 ns and a variable energy up to 1.5 Joules. Peak powers as high as 50 MW are obtained, which is sufficient to cause melting to depths of a few thousand angstroem. In this study, development of heat flow theory made it possible to calculate temperature profiles in silicon during pulsed laser irradiation. Silicon self-diffusion measurements, laser annealing of damage in As implanted silicon, and laser induced doping of single crystal silicon was also investigated. A computer programme was used to calculate the temperature profiles in silicon during pulsed laser irradiation. Radioactive 31Si (half-life = 2.62 hours) was used to determine for the first time the self-diffusion of silicon in silicon during pulsed laser irradiation. Radioactivity profiles in the silicon sample were measured by anodic oxidation, sequential removal of the formed SiO2 by etching in dilute HF and measurement of the radioactivity left in the sample. The removal of damage caused during ion implantation of Si substrates with As was investigated by using laser annealing. Rutherford backscattering of charged nuclear paricles coupled with the channeling technique, showed that an amorphous layer 1140 A thick formed during implantation. Complete removal of this damage only started to take place at energies high enough to cause melting to depths greater than the amorphous/single crystal interface. During resolidification, the molten silicon regrows epitaxially leading to complete removal of all the damage. Disorder removal started at 0.6 Jcm-2, while complete damage removal was achieved at energies above 1.5 Jcm-2. The doping of silicon with Sb, Bi and In by laser assisted diffusion was investigated from evaporated layers as well as solutions of these dopants

  19. Irradiation damage in γ-LiA102

    Using EPR measurements at temperatures ranging from 30 K to 300 K, we studied the response of lithium aluminate single crystals to the irradiation with electrons in the MeV range at 20 K and with X-rays at room temperature. In the electron-irradiated γ-LiA102 sample, we observed three different paramagnetic defects - that were absent prior irradiation - whose EPR features are described here. Two of these defects were also present in the X-ray irradiated sample. The latter result proves that, in the γ-LiA102 sample, a photochemical mechanism exists, that is efficient in producing these two defects

  20. A study of the x-irradiated Cs sub 5 H sub 3 (SO sub 4) sub 4 centre dot H sub 2 O crystal by EPR in the 80-415 K temperature range

    Waplak, S; Baranov, A I; Shuvalov, L A

    1997-01-01

    The EPR spectra of the x-irradiated fast proton conductor Cs sub 5 H sub 3 (SO sub 4) sub 4 centre dot H sub 2 O were investigated in the temperature range of 80-415 K. Two kinds of paramagnetic SO sub 4 sup - centres with different proton configurations below about 370 K and freeze-out behaviour of one of them below about 200 K were observed. The role of acid proton dynamics with respect to the glassy-like transition is discussed. (author)

  1. Is food irradiation harmful

    The paper reports on a seminar on 'The irradiation of food', held in London, 1987, and organised by the Royal Society and the Association of British Science Writers. A description is given of the food irradiation techniques. Problems with food irradiation are discussed with respect to the nutritional value of food, killing of microorganisms, survival of fungi following treatment, mutation of irradiated bacteria, and chemical changes produced in the food. Monitoring and controls of food that has been irradiated is discussed. A personal opinion of irradiated food by the author is given, including a verdict on irradiated food. (UK)

  2. Modelling irradiation creep of zirconium alloys

    The effect of texture and dislocation structure on irradiation creep of Zircaloy-2 (irradiated at about 340 K) and Zr-2.5Nb alloys (irradiated at about 558 K) is studied by means of a self-consistent model. The model relates the creep behaviour of polycrystals to that of single crystals by taking into account the crystallographic texture, dislocation density, grain shape and the intergranular stesses generated due to the crystallographic anisotropy. Three independent creep compliances of the polycrystal obtained from creep tests on a reference material are used to derive the single crystal creep compliances. These are used to calculate the polycrystalline compliances for the remaining materials. At low irradiation temperatures the predicted polycrystalline compliances agree well with the measured values. The observed behaviour can be described by a climb-assisted glide mechanism, in which the creep strain is accommodated mainly by prismatic slip, with smaller contributions from basal and pyramidal slip systems. At higher irradiation temperatures, the self-consistent approach can also describe well the creep behaviour of Zr-2.5Nb samples

  3. The role of oxygen containing impurities in defects formation in cesium halide crystals

    Hud, I.; Garapyn, I.; Pavlyk, B.

    2003-01-01

    The dependence of defect formation efficiency in CsI single crystals both on the type of oxygen containing impurities and the value of the absorbed irradiation dose was studied. Correlative results were obtained under investigation by methods of ionic thermocurrent (ITC), thermostimulated exoemission (TSEE), electrical conductivity and optical spectroscopy. The peculiarities of defect formation in gamma-irradiated CsI-CO3(SO4, OH) and X-irradiated CsI-OH single crystals are discussed.

  4. Thermoluminescence studies in cerium doped NaCl crystals

    Cerium is known to enter substitutionally in trivalent state when doped in alkali halides. Cerium doped NaCl crystals exhibit greatly enhanced thermoluminescence output upon X-irradiation at RT, the intensity of emission being about 10 times that in undoped crystals for similar dosage of irradiation. The cerium doped crystals give upon X-irradiation a very intense glow peak at 145degC with shoulders at 120degC and 210degC. Upon partially bleaching the crystal with F-light, the peak at 120degC becomes prominent probably due to faster bleaching of the glow at 145degC. From further optical bleaching studies, it is concluded that the glow peak at around 120degC is due to cerium centres in the irradiated crystal and the 145degC peak due to F centres. This F centre emission occurs at lower temperature, compared to that in the undoped crystals where it occurs at around 180degC. The spectral emission in the Ce doped crystals is in the blue-green region as compared to the emission in the blue region in undoped crystals. The trap depth and other parameters of the 120degC glow peak are estimated by the total curve fitting method. (author)

  5. Liquid Crystals

    1990-01-01

    Thermochromic liquid crystals, or TLCs, are a type of liquid crystals that react to changes in temperature by changing color. The Hallcrest/NASA collaboration involved development of a new way to visualize boundary layer transition in flight and in wind tunnel testing of aircraft wing and body surfaces. TLCs offered a new and potentially better method of visualizing the boundary layer transition in flight. Hallcrest provided a liquid crystal formulation technique that afforded great control over the sensitivity of the liquid crystals to varying conditions. Method is of great use to industry, government and universities for aerodynamic and hydrodynamic testing. Company's principal line is temperature indicating devices for industrial use, such as non-destructive testing and flaw detection in electric/electronic systems, medical application, such as diagnostic systems, for retail sale, such as room, refrigerator, baby bath and aquarium thermometers, and for advertising and promotion specials. Additionally, Hallcrest manufactures TLC mixtures for cosmetic applications, and liquid crystal battery tester for Duracell batteries.

  6. Detection of irradiated liquor

    D-2,3-butanediol is formed by irradiation processes in irradiated liquors. This radiolytic product is not formed in unirradiated liquors and its presence can therefore be used to identify whether a liquor has been irradiated or not. The relation meso/dl∼1 for 2,3-butanediol and the amount present in irradiated liquors may therefore be used as an indication of the dose used in the irradiation. (author)

  7. ESR study of irradiated uranyl salts

    Results of ESR measurements on gamma-irradiated single crystals of ammonium uranyl nitrate and potassium uranyl nitrate are reported. In ammonium uranyl nitrate, the observed radical is found to have a similar behaviour to irradiated rubidium uranyl nitrate. However, a pair of satellites to the main lines have been observed and they have been interpreted as the simultaneous proton spin-flips. In the case of potassium uranyl nitrate, the observed radicals are also assigned to NO3. The directions of the principal axes of the g-tensor and their values are reported. These results support theoretical predictions based on the electronic structure. (K.B.)

  8. Radiation processes in crystal solid solutions

    Gladyshev, Gennadi

    2012-01-01

    This is a monograph explaining processes occurring in two classes of crystal solids (metal alloys and doped alkali halide) under irradiation by various types of radiation (alpha, beta, gamma, X-radiations, ions). This e-book is a useful reference for advanced readers interested in the physics of radiation and solid state physics.

  9. Irradiation damage of SiC semiconductor device (I)

    Park, Ji Yeon; Kim, Weon Ju

    2000-09-01

    This report reviewed the irradiation damage of SiC semiconductor devices and examined a irradiation behavior of SiC single crystal as a pre-examination for evaluation of irradiation behavior of SiC semiconductor devices. The SiC single was crystal irradiated by gamma-beam, N+ ion and electron beam. Annealing examinations of the irradiated specimens also were performed at 500 deg C. N-type 6H-SiC dopped with N+ ion was used and irradiation doses of gamma-beam, N+ion and electron beam were up to 200 Mrad, 1x10{sup 16} N{sup +} ions/cm{sup 2} and 3.6 x 10{sup 17} e/cm{sup 2} and 1.08 x 10{sup 18} e/cm{sup 2} , respectively. Irradiation damages were analyzed by the EPR method. Additionally, properties of SiC, information about commercial SiC single crystals and the list of web sites with related to the SiC device were described in the appendix.

  10. Irradiation damage of SiC semiconductor device (I)

    This report reviewed the irradiation damage of SiC semiconductor devices and examined a irradiation behavior of SiC single crystal as a pre-examination for evaluation of irradiation behavior of SiC semiconductor devices. The SiC single was crystal irradiated by gamma-beam, N+ ion and electron beam. Annealing examinations of the irradiated specimens also were performed at 500 deg C. N-type 6H-SiC dopped with N+ ion was used and irradiation doses of gamma-beam, N+ion and electron beam were up to 200 Mrad, 1x1016 N+ ions/cm2 and 3.6 x 1017 e/cm2 and 1.08 x 1018 e/cm2 , respectively. Irradiation damages were analyzed by the EPR method. Additionally, properties of SiC, information about commercial SiC single crystals and the list of web sites with related to the SiC device were described in the appendix

  11. Cation disorder in high-dose, neutron-irradiated spinel

    Sickafus, K.E.; Larson, A.C.; Yu, N. [Los Alamos National Lab., CA (United States)] [and others

    1995-04-01

    The objective of this effort is to determine whether MgAl{sub 2}O{sub 4} spinel is a suitable ceramic for fusion applications. The crystal structures of MgAl{sub 2}O{sub 4} spinel single crystals irradiated to high neutron fluences [>5{times}10{sup 26} n/m{sup 2} (E{sub n}>0.1 MeV)] were examined by neutron diffraction. Crystal structure refinement of the highese dose sample indicated that the average scattering strength of the tetrahedral crystal sites decreased by {approx}20% while increasing by {approx}8% on octahedral sites.

  12. Photonic crystals

    Busch, Kurt; Wehrspohn, Ralf B; Föll, Helmut

    2006-01-01

    The majority of the contributions in this topically edited book stems from the priority program SPP 1113 ""Photonische Kristalle"" run by the Deutsche Forschungsgemeinschaft (DFG), resulting in a survey of the current state of photonic crystal research in Germany. The first part of the book describes methods for the theoretical analysis of their optical properties as well as the results. The main part is dedicated to the fabrication, characterization and modeling of two- and three-dimensional photonic crystals, while the final section presents a wide spectrum of applications: gas sensors, micr

  13. Optical Studies on Sol-Gel Derived Lead Chloride Crystals

    Rejeena, I; Lillibai, B; Nithyaja, B; Nampoori, P.N V; P. Radhakrishnan

    2013-01-01

    Optical characterization of lead chloride crystals prepared by sol-gel method is reported. The relevant sol-gel technique is used for the preparation of PbCl2 samples with five different types. In this paper, we report the absorption and fluorescence behaviour of pure, UV& IR irradiated and electric & magnetic field applied lead chloride crystal samples in solution phase at two different concentrations. Optical bandgap and emission studies of these crystals are also done.

  14. Effect of gamma irradiation on Korean traditional multicolored paintwork

    Gamma irradiation can destroy fungi and insects involved in the bio-deterioration of organic cultural heritages. However, this irradiation procedure can alter optical and structural properties of historical pigments used in wooden cultural heritage paintings. The crystal structure and color centers of these paintings must be maintained after application of the irradiation procedure. In this study, we investigated the effects of gamma irradiation on Korean traditional multicolored paintwork (Dancheong) for the preservation of wooden cultural heritages. The main pigments in Korean traditional wooden cultural heritages, Sukganju (Hematite; Fe2O3), Jangdan (Minium; Pb3O4), Whangyun (Crocoite; PbCrO4), and Jidang (Rutile; TiO2), were irradiated by gamma radiation at doses of 1, 5, and 20 kGy. After irradiation, changes in Commision Internationale d’Eclairage (CIE) color values (L*, a*, b*) were measured using the color difference meter, and their structural changes were analyzed using X-ray diffraction (XRD) analysis. The slightly change in less than 1 dE* unit by gamma irradiation was observed, and structural changes in the Dancheong were stable after exposure to 20 kGy gamma irradiation. In addition, gamma irradiation could be applied to painted wooden cultural properties from the Korean Temple. Based on the color values, gamma irradiation of 20 kGy did not affect the Dancheong and stability was maintained for five months. In addition, the fungicidal and insecticidal effect by less than 5 kGy gamma irradiation was conformed. Therefore, the optical and structural properties of Dancheong were maintained after gamma irradiation, which suggested that gamma irradiation can be used for the preservation of wooden cultural heritages painted with Dancheong. - Highlights: • Effects of gamma irradiation on the Dancheong were evaluated. • We confirmed that optical and structural properties of Dancheong were maintained. • Irradiation can contribute the decontamination for

  15. Defect formation in MgOxnAl2O3 at gamma-neutron irradiation

    Optical and mechanical characteristics of spinel crystals after reactor irradiation are investigated. The comparison of the concentrations of radiation-induced anion vacancies and stable F-centers has shown that less than one tenth of the point defects is stabilized at room temperature. The annealing of these vacancies occurs at 800 K. The vacancy formation during gamma-neutron irradiation of nominally pure spinel crystals improves the crack resistance. The irradiation of Fe- and Mn ion-doped crystals MgOxnAl2O3, is accompanied by the coagulation stresses and crack resistance decrease

  16. X-ray and optical study on point defect formation and interaction under irradiation adn doping of KCl

    Optical and X-ray diffuse scattering methods have been applied to investigate structural changes, taking place in KCl crystals during irradiation with γ-quanta and doping with barium. It is shown that γ-irradiation of ''pure'' and doped KCl crystals mainly leads to formation of F-centers and spherical vacancy complexes. F-center concentration in irradiated addition crystals (3x10-6) has turned out to be 25% lower, than in irradiated pure ones (4x10-6), which is connected with interaction of radiation and addition defects. The type of defects, causing assymetry in the distribution of diffuse scattering has been determined. Appearance of scattering ability modulation over direction during irradiation of KCl pure crystals has been found. Critical radius of spherical complexes formed during irradiation has been estimated, it appeared to be 2.5 a, where a is a lattice period

  17. Ion transport in Au+ doped/undoped KDP crystals with KI/NaI as additives

    R Ananda Kumari; R Chandramani

    2003-02-01

    Undoped KDP and KDP crystals containing KI/NaI with/without gold doping were grown by slow evaporation technique. All the grown crystals were -irradiated using 60Co source. Electrical conductivity measurements were carried out on all these crystals perpendicular to the unique direction before and after -irradiation. The present results show that the conductivity of KDP crystals increases with the addition of KI/NaI and with gold doping as well as upon rise in temperature. Computed values of activation energies from the conductivity measurements are given. For all the grown crystals, dielectric constant is measured as a function of frequency.

  18. Extraction of radiometal nuclides from reactor irradiated metal phthalocyanines: evaluation of the Ostwald-ripening mechanism

    Finely ground samples of β-copper phthalocyanine and β-zinc phthalocyanine were irradiated and subsequently submitted to extraction into a crystallizing solvent/dilute aqueous acid system. The quantities of radionuclide extracted are only slightly greater than those obtained from unground crystals of the β-metal phthalocyanines. Thus, the mechanism of extraction probably does not relate directly to crystal growth in the crystallizing solvent, as previously suggested. (author)

  19. The effect of γ-rays irradiation on poly (L-lactic acid)

    Poly (L-lactic acid) was irradiated by γ-rays. The effects of absorbed dose on viscosity average molecular weight, crystallization and thermal weight loss in irradiated condition under vacuum, nitrogen, air and oxygen were investigated, which were characterized by using ubbelohde viscometer, differential scamming calorimeter (DSC), polarized microscope and thermogravimetry analysis (TGA). Viscosity average molecular weight of PLLA decreases with increment of absorbed dose and viscosity average molecular weight of PLLA irradiated in vacuum is highest among the different irradiated condition at same absorbed dose. Both degree and rates of crystallization increase with increment of absorbed dose and TGA curves of PLLA irradiated under vacuum or nitrogen are shifted towards higher temperature compare with un-irradiated sample at the absorbed dose from 6-40kGy. The weight loss of PLLA irradiated under oxygen is lower than that under vacuum at absorbed dose of 6kGy. (authors)

  20. Irradiation of goods

    The necessary dose and the dosage limits to be observed depend on the kind of product and the purpose of irradiation. Product density and density distribution, product dimensions, but also packaging, transport and storage conditions are specific parameters influencing the conditions of irradiation. The kind of irradiation plant - electron accelerator or gamma plant - , its capacity, transport system and geometric arrangement of the radiation field are factors influencing the irradiation conditions as well. This is exemplified by the irradiation of 3 different products, onions, deep-frozen chicken and high-protein feed. Feasibilities and limits of the irradiation technology are demonstrated. (orig.)

  1. Neutron irradiation induced amorphization of silicon carbide

    Snead, L.L.; Hay, J.C. [Oak Ridge National Lab., TN (United States)

    1998-09-01

    This paper provides the first known observation of silicon carbide fully amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60 C to a total fast neutron fluence of 2.6 {times} 10{sup 25} n/m{sup 2}. Amorphization was seen in both materials, as evidenced by TEM, electron diffraction, and x-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density ({minus}10.8%), elastic modulus as measured using a nanoindentation technique ({minus}45%), hardness as measured by nanoindentation ({minus}45%), and standard Vickers hardness ({minus}24%). Similar property changes are observed for the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C.

  2. Neutron irradiation induced amorphization of silicon carbide

    This paper provides the first known observation of silicon carbide fully amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60 C to a total fast neutron fluence of 2.6 x 1025 n/m2. Amorphization was seen in both materials, as evidenced by TEM, electron diffraction, and x-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density (-10.8%), elastic modulus as measured using a nanoindentation technique (-45%), hardness as measured by nanoindentation (-45%), and standard Vickers hardness (-24%). Similar property changes are observed for the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C

  3. Photonic crystals principles and applications

    Gong, Qihuang

    2013-01-01

    IntroductionPrimary Properties of Photonic CrystalsFabrication of Photonic CrystalsPhotonic Crystal All-Optical SwitchingTunable Photonic Crystal FilterPhotonic Crystal LaserPhotonic Crystal Logic DevicesPhotonic Crystal Sensors

  4. Effects of ionizing radiation on struvite crystallization of livestock wastewater

    Livestock wastewater is generally very difficult to be treated by conventional wastewater treatment techniques because it contains high-strength organics (COD), ammonium (NH4+), phosphate (PO43−) and suspended solids. Struvite crystallization has been recently studied for the simultaneous removal of NH4+ and PO43−. In this study, gamma ray irradiation was carried out prior to struvite crystallization of the anaerobically digested livestock wastewater. The effects of gamma ray irradiation on the struvite crystallization of livestock wastewater were investigated. As a result, gamma ray irradiation can decrease the concentration of COD, NH4+ and PO43− contained in the livestock wastewater. This results in not only an enhancement of the struvite crystallization efficiency but also a decrease in the chemical demands for the struvite crystallization of livestock wastewater. - Highlights: • Gamma ray was applied prior to struvite crystallization of livestock wastewater. • Gamma ray resulted in an enhancement of struvite crystallization efficiency. • This is due to the decrease of COD concentration by gamma ray irradiation

  5. Group-Velocity-Matched Three Wave Mixing in Birefringent Crystals

    SMITH,ARLEE V.

    2000-12-12

    We show that the combination of pulse-front slant, k-vector tilt, and crystal birefringence often permits exact matching of both phase and group velocities in three wave mixing in birefringent crystals. This makes possible more efficient mixing of short light pulses, and it permits efficient mixing of chirped or broad bandwidth light. We analyze this process and present examples. Differences in the group velocities of the three interacting waves in a nonlinear crystal often limits the effective interaction length. For example, in mixing very short pulses, temporal walk off can stretch the pulses in time unless the crystal is very short. Efficient mixing with such short crystals requires high irradiances, but the irradiances are limited by higher order nonlinear effects such as intensity-dependent refractive index and two-photon absorption. Improved matching of the group velocities can alleviate this problem, allowing longer crystal and lower irradiances. Similarly, for high energy pulses, practical limits on crystal apertures mandate temporally stretching the pulses to reduce irradiances. For the resulting chirped pulses, temporal walk off restricts the chirp range unless the group velocities are well matched. In addition to perfectly matching the group velocities of all three waves, it is sometimes useful to match two velocities, such as the signal and idler in parametric amplification, permitting broadband parametric amplification, or to arrange the velocities of two inputs to bracket the generated sum frequency pulse, giving pulse compression under suitable circumstances.

  6. Defect controlled ferromagnetism in xenon ion irradiated zinc oxide

    Satyarthi, P.; Ghosh, S. [Nanostech Laboratory, Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); Mishra, P.; Sekhar, B.R. [Institute of Physics, Bhubaneswar 751005 (India); Singh, F.; Kumar, P.; Kanjilal, D. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Dhaka, R.S. [Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); Srivastava, P., E-mail: pankajs@physics.iitd.ac.in [Nanostech Laboratory, Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India)

    2015-07-01

    We report evolution of magnetic properties in zinc oxide (ZnO) single crystals and polycrystalline films induced by 500 KeV xenon ion (Xe{sup 3+}) irradiation. Room temperature ferromagnetism (RT-FM) behavior is observed in as deposited polycrystalline ZnO film and strength of FM enhances with ion fluence up to 2×10{sup 17} ions/cm{sup 2} and then decreases. However, RT-FM is not observed in ZnO single crystals even after irradiation with fluence up to 3.5×10{sup 17} ions/cm{sup 2}. The X-ray diffraction (XRD) and Raman measurements of ZnO single crystal reveal slightly disordered hexagonal wurtzite structure after irradiation. However, as deposited and irradiated polycrystalline ZnO films indicate excessive lattice defects in the wurtzite structure. X-ray photoelectron spectroscopy (XPS) reveals that Zn vacancy/interstitial defects are absent in all samples, although oxygen vacancy lattice defects are present. Density of oxygen vacancies is much higher in as deposited and irradiated polycrystalline ZnO films as compared to single crystals. This seems to be the determining factor for the presence and absence of RT-FM in ZnO films and single crystals respectively. The observed FM behavior in as deposited and irradiated polycrystalline ZnO films is explained on the basis of spin split impurity band formation from singly and doubly occupied oxygen vacancies which initiates d{sup 0} ferromagnetism. - Highlights: • We report defect controlled ferromagnetism in inert xenon ion irradiated ZnO. • Threshold concentration of O vacancies is essential to trigger ferromagnetism. • Spin imbalance of singly and doubly occupied oxygen vacancies induces ferromagnetism. • We reveal importance of d{sup 0} ferromagnetism in ZnO for future spintronics devices.

  7. Food irradiation in China

    In this paper, the author discussed the recent situation of food irradiation in China, its history, facilities, clearance, commercialization, and with emphasis on market testing and public acceptance of irradiated food. (author)

  8. Economics of food irradiation

    Economic aspects of food irradiation and direct economic benefits accruing from the application of food irradiation are discussed. A formula is presented to estimate the net economic benefit due to radiation processing of food. (M.G.B .)

  9. Degradation of insulating ceramics due to irradiation

    Kobayashi, Tomohiro; Terai, Takayuki; Yoneoka, Toshiaki; Tanaka, Satoru [Tokyo Univ. (Japan). Faculty of Engineering

    1996-10-01

    Radiation-induced electrical degradation was investigated on single crystal alumina under 2.2 MeV electron irradiation with a dose rate of 5.7 x 10{sup 5} Gy/s and an electrical field of 1.6 x 10{sup 5} V/m at 773 K. After irradiation, electrical resistivity both on the surface and in the bulk decreased in the temperature range of 300 to 773 K. Substantial resistivity decreased from the initial value due to the irradiation, the degradation ratio was much smaller than the case of poly-crystalline specimens. On the other hands, surface resistivity decreased with increasing temperature for measurement with an abrupt change by 4 orders of magnitude around 600 K, and it showed thermal hysteresis. (author)

  10. JMTR irradiation handbook

    A wide variety of nuclear irradiation and post-irradiation experiments are available using the JMTR (Japan Materials Testing Reactor, 50 MW) and the multi-cell hot laboratory associated with the JMTR. In this Handbook, an application manual for conducting irradiation and post-irradiation experiments using those facilities is provided. The Handbook is primarily designed to aid the experimenter and to serve as a reference for communications between the experimenter and the Division of JMTR Project. (author)

  11. JMTR irradiation handbook

    A wide variety of nuclear irradiation and post-irradiation experiments are available using the Japan Materials Testing Reactor, 50 MW (JMTR) and the multi-cell hot laboratory associated with the JMTR. In this Handbook, an application manual for conducting irradiation and post-irradiation experiments using those facilities is provided. The Handbook is primarily designed to aid the experimenter and to serve as a reference for communications between the experimenter and the Department of JMTR Project. (author)

  12. Modification of Hydroxyapatite Crystal Using IR Laser

    Satoh, Saburoh; Goto, M; Guan, W; Hayashi, N; Ihara, S; Yamabe, C; Yamaguchi, Y

    2004-01-01

    The first application of laser technology to dentistry was for the removal of caries. However, reports of laser application on improvement of dental surface were emerged, much attention has been focused on the laser’s potential to enhance enamel’s hardness and resistance to acid. Most of the previous reports concentrated on the photo issue interaction. Few research has pursued the photochemical phenomenon occurred during laser irradiation on biological tissues. In order to find a creative method to remineralize the dissociating enamel and exposed coronal of dentine, the authors developed a novel procedure during laser irradiation. Slice of sound molar and artificial HAp pellet were irradiated separately, with CO2 laser under different laser parameters. Tow series of samples covered with saturation calcium ion solution were irradiated separately. To investigate the crystal morphology, XRD pattern were surveyed. The comparison of each cases show that the chemical coating affected the ablation process evidentl...

  13. Polymer Morphological Change Induced by Terahertz Irradiation

    Hoshina, Hiromichi; Suzuki, Hal; Otani, Chiko; Nagai, Masaya; Kawase, Keigo; Irizawa, Akinori; Isoyama, Goro

    2016-06-01

    As terahertz (THz) frequencies correspond to those of the intermolecular vibrational modes in a polymer, intense THz wave irradiation affects the macromolecular polymorph, which determines the polymer properties and functions. THz photon energy is quite low compared to the covalent bond energy; therefore, conformational changes can be induced “softly,” without damaging the chemical structures. Here, we irradiate a poly(3-hydroxybutylate) (PHB) / chloroform solution during solvent casting crystallization using a THz wave generated by a free electron laser (FEL). Morphological observation shows the formation of micrometer-sized crystals in response to the THz wave irradiation. Further, a 10‑20% increase in crystallinity is observed through analysis of the infrared (IR) absorption spectra. The peak power density of the irradiating THz wave is 40 MW/cm2, which is significantly lower than the typical laser intensities used for material manipulation. We demonstrate for the first time that the THz wave effectively induces the intermolecular rearrangement of polymer macromolecules.

  14. Matrix ENDOR of the protonated carboxylic anion radical in γ-irradiated l-alanine. Simulation using a general matrix ENDOR line-shape model and single crystal data

    The matrix ENDOR line from the CH3CH(+NH3)COOOH- radical in γ-irradiated L-alanine powder at 77 K was simulated by using a generalized matrix ENDOR line-shape theory. The input includes hyperfine coupling constants for all protons in the proximity of the radical site as well as the pure dipolar interaction for more distant protons, microwave and radio-frequency magnetic field magnitudes, and nuclear and electron spin-lattice and spin-spin relaxation times. Simulated matrix ENDOR lines were tested against experimental line shapes, line widths, and the intensity of the ENDOR response as a function of the radio-frequency magnetic field. The simulated ENDOR response was found to be very sensitive to the value of the nuclear spin-lattice relaxation time, and a value of 0.15 s satisfactorily reproduces the experimental results. The relevant conclusion from this study is that an angularly independent nuclear relaxation mechanism dominates the ENDOR response

  15. Containers in food irradiation

    The preservation of food by irradiation is promising technology which increases industrial application. Packaging of irradiated foods is an integral part of the process. Judicious selection of the package material for successful trade is essential. In this paper is presented a brief review of important aspects of packaging in food irradiation

  16. Electron microscope study of irradiated beryllium oxide

    The beryllium oxide is studied first by fractography, before and after irradiation, using sintered samples. The fractures are examined under different aspects. The higher density sintered samples, with transgranular fractures are the most interesting for a microscopic study. It is possible to mark the difference between the 'pores' left by the sintering process and the 'bubbles' of gases that can be produced by former thermal treatments. After irradiation, the grain boundaries are very much weakened. By annealing, it is possible to observe the evolution of the gases produced by the reaction (n, 2n) and (n. α) and gathered on the grain boundaries. The irradiated beryllium oxide is afterwards studied by transmission. For that, a simple method has been used: little chips of the crushed material are examined. Clusters of point defects produced by neutrons are thus detected in crystals irradiated at the three following doses: 6 x 1019, 9 x 1019 and 2 x 1020 nf cm-2 at a temperature below 100 deg. C. For the irradiation at 6 x 1019 nf cm-2, the defects are merely visible, but at 2 x l020 nf cm-2 the crystals an crowded with clusters and the Kikuchi lines have disappeared from the micro-diffraction diagrams. The evolution of the clusters into dislocation loops is studied by a series of annealings. The activation energy (0,37 eV) calculated from the annealing curves suggests that it must be interstitials that condense into dislocation loops. Samples irradiated at high temperatures (650, 900 and 1100 deg. C) are also studied. In those specimens the size of the loops is not the same as the equilibrium size obtained after out of pile annealing at the same temperature. Those former loops are more specifically studied and their Burgers vector is determined by micro-diffraction. (author)

  17. Polyamide-6: The effects on mechanical and physicochemical properties by electron beam irradiation at different temperatures

    The electron beam irradiation of polyamide-6 (PA-6) films was carried out in air over a range of 50–1000 kGy at varying temperatures and a dose rate of 5.1 kGy min−1. The effects of the irradiation at temperatures above and below the glass transition temperature (Tg) on the thermal and mechanical properties were studied. Melting and crystallization temperatures decreased significantly with the increase in irradiation dose, whereas percent of crystallinity varied only slightly and Tg slightly increased for irradiated samples respect to non irradiated one with no significant effect of the dose. Mechanical properties were affected by irradiation. The material became more rigid with a direct relationship between the mechanical properties and the irradiation dose. The irradiation above Tg led to a larger variation in the thermal and mechanical properties respect to the irradiation below Tg. The changes in properties were related to the crosslinking produced in the amorphous part of the polymer by the electron beam irradiation. - Highlights: • Electron beam irradiation in polyamide-6 produced higher crosslinking than in polyamide-6,6. • Crosslinking took place mainly in the amorphous phase of the polymer. • Polyamide-6 melting point slightly decreased with the increase in irradiation dose and crystallinity remained practically unchanged. • Mechanical properties were strongly affected by irradiation dose. Irradiation above Tg significantly increased the changes in thermal and mechanical properties respect to irradiation at ambient temperature

  18. Channelling phenomenon in the gamma irradiated Benzo-quinone and other compounds observed under the scanning electron microscope

    Scanning Electron Microscope (S.E.M.), has been used to examine the gamma irradiated pure crystals of Benzo-quinone and other compounds in the polycrystaline form. After gamma irradiation, shallow lines (channels) were observed on the crystal's surfaces when the crystal layers arrangements are parallel to the photons beam direction. Holes were also observed when those layers of the crystals are in the nonparallel case. The phenomenon has been studied and analysed in connected with the H-atom bonds disruption, and H-atoms migration through the crystal's layers. (author)

  19. Canadian Food Irradiation Facilities

    Atomic Energy of Canada Limited (AECL) began work on the irradiation of potatoes in 1956, using spent fuel rods as the radiation source. In 1958 the first Gammacell 220, a self-contained irradiator, was designed and manufactured by AECL, and cobalt-60 was then used exclusively in the food irradiation programme. In 1960 the first food and drug clearance was obtained for potatoes. The next stage was to demonstrate to the potato industry that cobalt-60 was a safe, simple and reliable tool, and that irradiation would inhibit sprouting under field conditions. A mobile irradiator was designed and produced by AECL in 1961 to carry out this pilot-plant programme. The irradiator was mounted on a fully-equipped road trailer and spent the 1961/1962 season irradiating one million pounds of potatoes at various points in Eastern Canada. In 1965 the first commercial food irradiator was designed and built by AECL for Newfield Products, Ltd. Whilst the potato programme was under way, AECL initiated co-operative programmes with Canadian food research laboratories, using additional Gammacells. In 1960, AECL constructed an irradiation facility in a shielded room at its own plant in Ottawa for the irradiation of larger objects, such as sides of pork and stems of bananas. During 1963 the mobile irradiator, already a most useful tool, was made more versatile when its source strength was increased and it was equipped with a product cooling system and van air conditioning. Following these modifications, the unit was employed in California for the irradiation of a wide spectrum of fruits at the United States Department of Agriculture Station in Fresno. The Gammacell, mobile irradiator, shielded-room facility, the commercial food irradiator and some of the main food programmes are described in detail. There is an increasing amount of interest in irradiation by the food industry, and prospects are encouraging for future installations. (author)

  20. Welding irradiated stainless steel

    Conventional welding processes produced severe underbead cracking in irradiated stainless steel containing 1 to 33 appm helium from n,a reactions. A shallow penetration overlay technique was successfully demonstrated for welding irradiated stainless steel. The technique was applied to irradiated 304 stainless steel that contained 10 appm helium. Surface cracking, present in conventional welds made on the same steel at the same and lower helium concentrations, was eliminated. Underbead cracking was minimal compared to conventional welding methods. However, cracking in the irradiated material was greater than in tritium charged and aged material at the same helium concentrations. The overlay technique provides a potential method for repair or modification of irradiated reactor materials

  1. THERMAL BEHAVIOUR OF γ-IRRADIATED NYLON 610

    JIN Yan; CHEN Donglin

    1988-01-01

    The thermal behaviour of γ-irradiated nylon 610 was investigated. In DSC (differential scanning calorimetry) thermograms in addition to general features characteristic of γ-irradiation cross-linked crystalline polymers, a typical cold-crystallization phenomenon was observed during the sceond scan for samples that had been subjected to high radiation dose. G-values for crosslinking nylon 610 were estimated from gel fraction measurement and TMA (thermomechanical analysis), From TMA curves it was estimated that the dimensional stability of properly irradiated nylon 610 articles might be raised up to ca. 300℃.

  2. Structure and lyoluminescent reactions of free radicals of irradiated lactose

    To determine mechanisms of processes, resulting in lyoluminescence the structure of fren radicals in γ-irradiated lactose was investigated by the method of electron paramagnetic resonance. Analysis of dependences of different radical content in irradiated crystals and lyoluminescent characteristics of these samples on the period of their storing enabled to confirm suggested earlier luminescence mechanism with lambdasub(max)=630 nm of irradiated carbon-hydrate in neutral and acid media. The possibility of controlling the content of different types of radicals in samples by lyoluminescent method was shown

  3. Effect of gamma irradiation on Korean traditional multicolored paintwork

    Yoon, Minchul; Kim, Dae-Woon; Choi, Jong-il; Chung, Yong-Jae; Kang, Dai-Ill; Hoon Kim, Gwang; Son, Kwang-Tae; Park, Hae-Jun; Lee, Ju-Woon

    2015-10-01

    Gamma irradiation can destroy fungi and insects involved in the bio-deterioration of organic cultural heritages. However, this irradiation procedure can alter optical and structural properties of historical pigments used in wooden cultural heritage paintings. The crystal structure and color centers of these paintings must be maintained after application of the irradiation procedure. In this study, we investigated the effects of gamma irradiation on Korean traditional multicolored paintwork (Dancheong) for the preservation of wooden cultural heritages. The main pigments in Korean traditional wooden cultural heritages, Sukganju (Hematite; Fe2O3), Jangdan (Minium; Pb3O4), Whangyun (Crocoite; PbCrO4), and Jidang (Rutile; TiO2), were irradiated by gamma radiation at doses of 1, 5, and 20 kGy. After irradiation, changes in Commision Internationale d'Eclairage (CIE) color values (L*, a*, b*) were measured using the color difference meter, and their structural changes were analyzed using X-ray diffraction (XRD) analysis. The slightly change in less than 1 dE* unit by gamma irradiation was observed, and structural changes in the Dancheong were stable after exposure to 20 kGy gamma irradiation. In addition, gamma irradiation could be applied to painted wooden cultural properties from the Korean Temple. Based on the color values, gamma irradiation of 20 kGy did not affect the Dancheong and stability was maintained for five months. In addition, the fungicidal and insecticidal effect by less than 5 kGy gamma irradiation was conformed. Therefore, the optical and structural properties of Dancheong were maintained after gamma irradiation, which suggested that gamma irradiation can be used for the preservation of wooden cultural heritages painted with Dancheong.

  4. Crystals channel high-energy beams in the LHC

    CERN Bulletin

    2015-01-01

    Bent crystals can be used to deflect particle beams, as suggested by E. Tsyganov in 1976. Experimental demonstrations have been carried out for four decades in various laboratories worldwide. In recent tests, a bent crystal inserted into the LHC beam halo successfully channelled and deflected 6.5 TeV protons into an absorber, with reduced secondary irradiation.    Quasimosaic crystal for the LHC (developed by PNPI). Bent crystal technology was introduced at CERN and further developed for the LHC by the UA9 Collaboration. For about ten years, experts from CERN, INFN (Italy), Imperial College (UK), LAL (France), and PNPI, IHEP and JINR (Russia) have been investigating the advantages of using bent crystals in the collimation systems of high-energy hadron colliders. A bent crystal replacing the primary collimator can deflect the incoming halo deeply inside the secondary collimators, improving their absorption efficiency. “The bent crystals we have just tested at the world-record en...

  5. Vacancy-type defects in electron and proton irradiated ZnS and ZnTe

    In this contribution we present a study aimed at investigating irradiation induced defects in ZnTe single crystals (3 MeV protons), ZnS single crystals (1 MeV electrons) and ZnS polycrystals (3 MeV protons). In positron annihilation experiments the stability of the induced defects as well as possible clustering mechanisms were investigated. It was found that both electron and proton irradiation caused significant changes in the positron annihilation characteristics. (orig.)

  6. Ribbon Crystals

    Bohr, Jakob; Markvorsen, Steen

    2013-01-01

    A repetitive crystal-like pattern is spontaneously formed upon the twisting of straight ribbons. The pattern is akin to a tessellation with isosceles triangles, and it can easily be demonstrated with ribbons cut from an overhead transparency. We give a general description of developable ribbons...... using planar triangles and cylindrical arcs, and the ribbon structure is shown to arise from a maximization of the end-to-end length of the ribbon, i.e. from an optimal use of ribbon length. The phenomenon is discussed in the perspectives of incompatible intrinsic geometries and of the emergence of long...

  7. Surface modification of multilayer graphene using Ga ion irradiation

    The effect of Ga ion irradiation intensity on the surface of multilayer graphene was examined. Using Raman spectroscopy, we determined that the irradiation caused defects in the crystal structure of graphene. The density of defects increased with the increase in dwell times. Furthermore, the strain induced by the irradiation changed the crystallite size and the distance between defects. These defects had the effect of doping the multilayer graphene and increasing its work function. The increase in work function was determined using contact potential difference measurements. The surface morphology of the multilayer graphene changed following irradiation as determined by atomic force microscopy. Additionally, the adhesion between the atomic force microscopy tip and sample increased further indicating that the irradiation had caused surface modification, important for devices that incorporate graphene

  8. Surface modification of multilayer graphene using Ga ion irradiation

    Wang, Quan, E-mail: wangq@mail.ujs.edu.cn [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shao, Ying; Ge, Daohan; Ren, Naifei [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); Yang, Qizhi [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); State key laboratory of Robotics, Chinese Academy of Sciences, Shengyang 110000 (China)

    2015-04-28

    The effect of Ga ion irradiation intensity on the surface of multilayer graphene was examined. Using Raman spectroscopy, we determined that the irradiation caused defects in the crystal structure of graphene. The density of defects increased with the increase in dwell times. Furthermore, the strain induced by the irradiation changed the crystallite size and the distance between defects. These defects had the effect of doping the multilayer graphene and increasing its work function. The increase in work function was determined using contact potential difference measurements. The surface morphology of the multilayer graphene changed following irradiation as determined by atomic force microscopy. Additionally, the adhesion between the atomic force microscopy tip and sample increased further indicating that the irradiation had caused surface modification, important for devices that incorporate graphene.

  9. Further results on cerium fluoride crystals

    A systematic investigation of the properties of cerium fluoride monocrystals has been performed by the 'Crystal Clear' collaboration in view of a possible use of such crystals for the construction of high precision electromagnetic calorimeters for the future generation of high luminosity accelerators. A large sample of different crystals grown by several producers has been studied. The spectroscopic characteristics, the transmission, luminescence and excitation spectra and the decay time curves are analysed. The light yield of the different crystals is measured with photomultipliers and Si photodiodes and compared to reference standards like BGO and NaI(Tl). The radiation damage behaviour is then presented for γ and neutron irradiations, at different doses and dose rates, including thermal and optical bleaching. (orig.)

  10. Further results on cerium fluoride crystals

    Anderson, S.; Auffray, E.; Aziz, T.; Baccaro, S.; Banerjee, S.; Bareyre, P.; Barone, L.E.; Borgia, B.; Boutet, D.; Burq, J.P.; Chemarin, M.; Chipaux, R.; Dafinei, I.; D' Atanasio, P.; De Notaristefani, F.; Dezillie, B.; Dujardin, C.; Dutta, S.; Faure, J.L.; Fay, J.; Ferrere, D.; Francescangeli, O.; Fuchs, B.A.; Ganguli, S.N.; Gillespie, G.; Goyot, M.; Gupta, S.K.; Gurtu, A.; Heck, J.; Herve, A.; Hillemanns, H.; Holdener, F.; Ille, B.; Joensson, L.; Kierstead, J.; Krenz, W.; Kway, W.; Le Goff, J.M.; Lebeau, M.; Lebrun, P.; Lecoq, P.; Lemoigne, Y.; Loomis, G.; Lubelsmeyer, K.; Madjar, N.; Majni, G.; El Mamouni, H.; Mangla, S.; Mares, J.A.; Martin, J.P.; Mattioli, M.; Mauger, G.J.; Mazumdar, K.; Mengucci, P.; Merlo, J.P.; Moine, B.; Nikl, N.; Pansart, J.P.; Pedrini, C.; Poinsignon, J.; Polak, K.; Raghavan, R.; Rebourgeard, P.; Rinaldi, D.; Rosa, J.; Rosowsky, A.; Sahuc, P.; Samsonov, V.; Sarkar, S.; Schegelski, V.; Schmitz, D.; Schneegans, M.; Seliverstov, D.; Stoll, S.; Sudhakar, K.; Sven; Crystal Clear Collaboration

    1993-08-15

    A systematic investigation of the properties of cerium fluoride monocrystals has been performed by the 'Crystal Clear' collaboration in view of a possible use of such crystals for the construction of high precision electromagnetic calorimeters for the future generation of high luminosity accelerators. A large sample of different crystals grown by several producers has been studied. The spectroscopic characteristics, the transmission, luminescence and excitation spectra and the decay time curves are analysed. The light yield of the different crystals is measured with photomultipliers and Si photodiodes and compared to reference standards like BGO and NaI(Tl). The radiation damage behaviour is then presented for [gamma] and neutron irradiations, at different doses and dose rates, including thermal and optical bleaching. (orig.)

  11. Pendellösung effect in photonic crystals

    Savo, S.; di Gennaro, E.; Miletto, C.; Andreone, A.; Dardano, P.; Moretti, L.; Mocella, V.

    2008-06-01

    At the exit surface of a photonic crystal, the intensity of the diffracted wave can be periodically modulated, showing a maximum in the "positive" (forward diffracted) or in the "negative" (diffracted) direction, depending on the slab thickness. This thickness dependence is a direct result of the so-called Pendellosung phenomenon, consisting of the periodic exchange inside the crystal of the energy between direct and diffracted beams. We report the experimental observation of this effect in the microwave region at about 14 GHz by irradiating 2D photonic crystal slabs of different thickness and detecting the intensity distribution of the electromagnetic field at the exit surface and inside the crystal itself.

  12. Proton irradiation effect on hydrogen bond material and biological systems

    When the proton beam was irradiated on partially deuterated KH2PO4 single crystal with fluence of 1015ions/cm3, and irradiation energy of 1.0 MeV, the ferroelectric phase transition temperature was significantly raised by 5 K. Increase of the phase transition temperature can be closely related to the structural modification involving the hydrogen-bond geometry, demonstrating that proton irradiation can be adopted as a powerful means of atomic-scale modification of the microscopic structures in hydrogen-bonded ferroelectrics. These results have been published as 'Significant increase of the ferroelectric phase transition temperature in partially deuterated KH2PO-4 by proton irradiation'. We have studied the microscopic structure and dynamics in a proton-irradiated KH2PO4 single crystal. Our 1H and 31P nuclear magnetic resonance measurements indicate that proton irradiation gives rise to a decrease in the local dipolar order of the rigid lattice protons and an increase in interstitial protons as well as structural distortion of the PO4 tetrahedra. While the luminescence was severely weakened by the low-energy irradiation with a high dosage, it was affected only weakly by the high-energy irradiation with a low dosage. The electroluminescence was affected by the irradiation more severely than the photoluminescence was, preserving the external quantum efficiency. While the luminescence spectrum of the severely damaged polymer was broadened with a blue-shift, a weak damage resulted only in a decrease in the luminescence intensity apparently preserving the spectral shape. The change in the luminescence spectra may be explained by chain conformational disorders as well as chain scission induced by the irradiation.

  13. RADIATION-DAMAGE IN NACL .1. OPTICAL-ABSORPTION EXPERIMENTS ON HEAVILY IRRADIATED SAMPLES

    WEERKAMP, JRW; GROOTE, JC; SEINEN, J; DENHARTOG, HW

    1994-01-01

    Results of optical-absorption experiments on heavily irradiated NaCl single crystals are presented. The dose rates were between 4 and 250 Mrad/h; the doses between 1 and 7 Grad. The irradiation temperatures were in the range of 20-150-degrees-C. Because of the intense optical bands, the thickness of

  14. Precipitation and irradiation damage in proton-irradiated palladium-chromium alloys

    Irradiation damage of Pd-Cr alloys containing 15, 20 and 25 at.% Cr was studied over the temperature range 100 to 5500C, primarily in samples irradiated to a dose of 0.7 d.p.a. The solubility limit in this range of temperatures varies from 22 to 38% Cr, and precipitation of a phase having the L12 crystal structure was observed in unirradiated samples of the 25% Cr alloy aged at temperatures as low as 1000C. Octahedrally shaped voids, with faces parallel to {1 1 1}, were found only in the 25% Cr alloy irradiated from 350 to 5500C, but not in the other alloys at any temperature. The undersized chromium atoms migrate to point-defect sinks during irradiation, resulting in solute segregation and, eventually, precipitation under certain conditions. The precipitation of the L12 phase, was irradiation-induced at dislocation loops, voids and grain boundaries in the more concentrated undersaturated alloys. This precipitation was observed in the mid-range and surface regions of the samples containing 20 and 25% Cr, but not in those containing 15% Cr. Comparisons were made with Pd-Fe and Ni-Si alloys, which had also been proton-irradiated, and the similarities and differences noted and discussed. (author)

  15. Biological Macromolecule Crystallization Database

    SRD 21 Biological Macromolecule Crystallization Database (Web, free access)   The Biological Macromolecule Crystallization Database and NASA Archive for Protein Crystal Growth Data (BMCD) contains the conditions reported for the crystallization of proteins and nucleic acids used in X-ray structure determinations and archives the results of microgravity macromolecule crystallization studies.

  16. The crystallisation of irradiated MOX fuel

    Pateman, Richard; Cooke, Richard; Jenkins, Jon [Summit AEA Corp., Tokyo (Japan); Mason, Chris [AEA Technology (United Kingdom)

    2002-02-01

    Two crystallisation tests have been carried out with irradiated MOX fuel solution. In the first test, MOX1, the final temperature of the solution was 10degC. In the second test, MOX2, the final temperature of the solution was 0degC. The conclusions of the tests were as follows. Spontaneous crystallisation of uranyl nitrate hexahydrate (UNH) occurred in both tests at approximately 28degC. This is less than the 32degC observed with pure uranyl nitrate/nitric acid solutions, possibly because of the presence of fission product impurities and plutonium (Pu). The MOX2 test gave, as expected, a higher yield of UNH crystals than the MOX1 test. The U hold-up ratio (U in crystals as a proportion of the total U in the MOX feed to the process) was 0.57 and 0.68 for MOX1 and MOX2 respectively. The hold-up of Pu in the UNH crystals (Pu in crystals by direct analysis as a proportion of the total Pu in the MOX feed to the process) was very low, with values for the final crystals after three scrubs of 8.2E-04 for MOX1 and 1.03E-03 for MOX2. The U concentration in the damp crystals was very similar for both MOX1 and MOX2, at 0.488g/g and 0.484g/g respectively, which is within 2% - 3% of the theoretical stochiometric ratio for pure UNH. The good agreement of the U concentration in the crystals with that for pure UNH indicates that very little liquid was held up in the crystals after filtration. However, the quantity of actinide and fission product impurities scrubbed from the UNH crystals was relatively high, in terms of volumes and concentrations of the filtrate solutions. Therefore scrubbing possibly leached the actinides and fission products from the UNH crystals, rather than diluted and removed liquid held up in the crystals. High decontamination of the UNH crystals from Pu and the main actinide and fission product impurities was achieved by scrubbing. For example, DFs for {sup 241}Am, {sup 244}Cm , {sup 134/137}Cs and {sup 154/155}Eu were generally about 700 to 900 for MOX1 and

  17. The crystallisation of irradiated MOX fuel

    Two crystallisation tests have been carried out with irradiated MOX fuel solution. In the first test, MOX1, the final temperature of the solution was 10degC. In the second test, MOX2, the final temperature of the solution was 0degC. The conclusions of the tests were as follows. Spontaneous crystallisation of uranyl nitrate hexahydrate (UNH) occurred in both tests at approximately 28degC. This is less than the 32degC observed with pure uranyl nitrate/nitric acid solutions, possibly because of the presence of fission product impurities and plutonium (Pu). The MOX2 test gave, as expected, a higher yield of UNH crystals than the MOX1 test. The U hold-up ratio (U in crystals as a proportion of the total U in the MOX feed to the process) was 0.57 and 0.68 for MOX1 and MOX2 respectively. The hold-up of Pu in the UNH crystals (Pu in crystals by direct analysis as a proportion of the total Pu in the MOX feed to the process) was very low, with values for the final crystals after three scrubs of 8.2E-04 for MOX1 and 1.03E-03 for MOX2. The U concentration in the damp crystals was very similar for both MOX1 and MOX2, at 0.488g/g and 0.484g/g respectively, which is within 2% - 3% of the theoretical stochiometric ratio for pure UNH. The good agreement of the U concentration in the crystals with that for pure UNH indicates that very little liquid was held up in the crystals after filtration. However, the quantity of actinide and fission product impurities scrubbed from the UNH crystals was relatively high, in terms of volumes and concentrations of the filtrate solutions. Therefore scrubbing possibly leached the actinides and fission products from the UNH crystals, rather than diluted and removed liquid held up in the crystals. High decontamination of the UNH crystals from Pu and the main actinide and fission product impurities was achieved by scrubbing. For example, DFs for 241Am, 244Cm , 134/137Cs and 154/155Eu were generally about 700 to 900 for MOX1 and 1200 to 2500 for MOX2

  18. Destruction of graphite monocrystals and pseudomonocrystals under low temperature irradiation

    Studied was the effect of reactor irradiation at temperature of 700 deg C (fluence 2.7x1020 neutr/cm2, E>0.18 MeV) upon the structure of single crystals of graphite grown by spontaneous crystallization of a hypereutectoid Fe-C melt and upon the structure of pseudo-single crystals produced by thermomechanical working of high-perfection pyrolitic graphite at 2800-3000 deg C. Structure variations were determined by the Laue method. A discrete character of structure variations related to polygonization of coarse crystallites, accompanied, probably, by twinning was suggested

  19. Color centers aggregation kinetics in lithium fluoride after gamma irradiation

    Lithium fluoride crystals are irradiated at various doses by gamma rays at 77 K. The time evolution of photoluminescence signals from aggregated F2+, F2, F3+ and F3 color centers, and of the absorption intensity of primary F centers are measured at various annealing temperatures. The lifetimes of anionic vacancies υa and F2+ centers, the characteristic times of concentration growth of F2, F3+ and F3 centers, and also the activation energies of diffusion of vacancies and F2+ centers together with various processes of aggregation are determined. It is found that lifetime decreases for vacancies while increases for F2+ centers by increasing the irradiation dose. It is also shown that, after irradiation during annealing, vacancies are formed as a result of the reaction F2++H→υa+Fl−, where Fl− is a fluorine ion in a lattice site and H is a fluorine interstitial atom. Then these vacancies participate in color centers aggregation kinetics. The presence of F− centers in the irradiated crystal is established, and the processes which lead to the formation of F2, F3+ and F3 centers after irradiation, are unveiled. -- Highlights: • Experimental investigation of color centers in LiF crystals after gamma irradiation. • Study of formation kinetics for F, F2, F3 and F3+ centers after irradiation at 77 K. • Lifetimes of anionic vacancies and F2+ centers at few irradiation doses. • Aggregation rates of F2, F3 and F3+ centers and their reciprocal influence. • Estimates of activation energies for color center diffusion

  20. Crystallization of modified hydroxyapatite on titanium implants

    Golovanova, O. A.; Izmailov, R. R.; Ghyngazov, S. A.; Zaits, A. V.

    2016-02-01

    Carbonated-hydroxyapatite (CHA) and Si-hydroxyapatite (Si-HA) precipitation have been synthesized from the model bioliquid solutions (synovial fluid and SBF). It is found that all the samples synthesized from the model solutions are single-phase and represent hydroxyapatite. The crystallization of the modified hydroxyapatite on alloys of different composition, roughness and subjected to different treatment techniques was investigated. Irradiation of the titanium substrates with the deposited biomimetic coating can facilitate further growth of the crystal and regeneration of the surface.

  1. Irradiation effects on polycaprolactone

    The structure and some physical properties of γ-irradiated polycaprolactone (PCL), a semi-crystalline linear saturated polyester, were studied as function of the irradiation dose level. The critical dose level for gel formation is 26 Mrad and above this irradiation dose the number of scission events is similar to the number of crosslinking events. G.p.c. results show that the initial rather narrow molecular weight distribution gradually widens with increasing dose in the pre-gelation region. A significant difference between first and second d.s.c. scans of irradiated PCL is shown and explained. Scission and crosslinking reactions associated with the irradiation process occur preferentially in the non-ordered regions. Small irradiation doses, 2 to 5 Mrad, are shown to have a dramatic effect on the tensile elongation at break by converting ductile PCL samples into brittle materials. (author)

  2. Thermoluminescence studies in lead doped KCl and KBr crystals

    Lead is known to enter substitutionally in divalent state when doped in alkali halides. When irradiated at room temperature these lead centers (Pb++) act as traps for electrons knocked off from the halogen ions and become Pb+ and Pb0 (for large doses of irradiation). These changes could be followed in the optical absorption studies. These lead-doped crystals after X-ray irradiation yield a thermoluminescence output smaller than that observed in 'pure' crystals. However, two new glow peaks are observed in additions to those due to F-centers. In KCl : Pb and Kbr : Pb crystals part of the F-center glow preceds the new glow peaks. The new peaks are attributed to the Pb+ and Pb0 centers. The glow peak temperatures and trap depths for these peaks an obtained by total-curve fitting method are reported. (author)

  3. Identification of irradiated chicken

    Frozen chicken and chicken parts were irradiated at a dose of 5 kGy with Co-60. The irradiated chicken and chicken parts were identified by determination of three radiation-induced hydrocarbons from the lipid fraction. Isolation was carried out by high-vacuum distillation with a cold-finger apparatus. The detection of the hydrocarbons was possible in all irradiated samples by gaschromatography/mass spectrometry. (orig.)

  4. Preparation of ZnO nanocrystals via ultrasonic irradiation

    Qian, D.; Jiang, Jianzhong; Hansen, P. L.

    2003-01-01

    A simple and rapid process has been developed for the preparation of nanometer-sized ZnO crystals via ultrasonic irradiation, by which pure ZnO nanocrystals with an average size of 6 nm and narrow size distribution can be synthesized in a short time and without using any solvents for the...... precipitation of ZnO....

  5. Irradiation application of electronic beam accelerator NBL-1010

    The application of electronic beam accelerator NBL-1010 in semiconductor denature, gem coloring, waster treatment, chemical synthesize of radiation, degrading of agricultural waster, sterilization of one-off medical treatment, sterilization of herbs, food preservation, crystal coloring and preservation of commodities was studied for its effects equaled with cobalt gamma irradiation

  6. Present status of studies on special irradiation of materials

    The study on radiation damage under severe irradiation condition has been developed in connection with the materials for fusion reactors. This paper is a report of a study meeting concerning the radiation damage. The free migration of interstitial atoms is discussed on the basis of the measurement of internal friction. The point defects of pure iron irradiated by reactor neutrons at low temperature, the 304 stainless steel and FeSiB amorphous alloy irradiated by He ions at room temperature were studied by the measurement of Moessbauer effect. The study on radiation defect by X-ray diffuse scattering is reported. Discussion on the lattice defects in insulating crystals is presented. Sputtering by high density electron excitation, and the behavior of T, D and H atoms in low temperature solids are discussed. Other topics presented in this report are neutron irradiated FCC metal crystals, the radiation effects on cadmium halide crystals and impurity metal ions, and the effects on the properties of semi-conductors by irradiation. The reports on the joint meeting of International Cryogenic Material Conference and Cryogenic Engineering Conference of U.S.A., and the IAEA meeting on the nuclear data for radiation damage and safety are presented. (Kato, T.)

  7. Gamma irradiation devices

    The main parameters and the preparation procedures of the gamma radiation sources frequently applied for irradiation purposes are discussed. In addition to 60Co and 137Cs sources also the nuclear power plants offer further opportunities: spent fuel elements and products of certain (n,γ) reactions can serve as irradiation sources. Laboratory scale equipments, pilot plant facilities for batch or continuous operation, continuous industrial irradiators and special multipurpose, mobile and panorama type facilities are reviewed including those in Canada, USA, India, the Soviet Union, Hungary, UK, Japan and Australia. For irradiator design the source geometry dependence of the spatial distribution of dose rates can be calculated. (V.N.)

  8. Irradiation of food

    A committee has on instructions from the swedish government made an inquiry into the possible effects on health and working environment from irradition of food. In this report, a review is presented on the known positiv and negative effects of food irradiation Costs, availabilty, shelf life and quality of irradiated food are also discussed. According to the report, the production of radiolysis products during irradiation is not easily evaluated. The health risks from irradiation of spices are estimated to be lower than the risks associated with the ethenoxid treatment presently used. (L.E.)

  9. Food irradiation. An alternative

    In order to start a food irradiation program, one needs to perform some tests, such as: local handling problems, consumer acceptance and government licenses. At this point the cost of a special food irradiator can be considered a too high investment. It is proposed that for the irradiation of a few tons of several food items, a commercial irradiator for medical products sterilization be employed. With the use of an ''experimental loop'' and some special positions inside the irradiation chamber, it is possible to irradiate even potatoes and onions, at doses ranging from 100 Gy to 200 Gy. The quantities, depending on the source activity, can be around 300 kg per hour. For doses near 10 kGy, the normal procedure used for sterilization of medical products can be employed, while changing the cycle on the machine. In the case of an experimental loop within a JS-7400 (AECC) irradiator at a dose rate of 20 Gy per minute, around 200 kg of potatoes per hour can be irradiated. The experimental positions inside the chamber have a dose rate of 60 Gy per hour, and the batch capacity is 250 kg, so that 250 kg can be irradiated each 1,5 hour

  10. The influence on the crystallization of Ag doped Gd2 O3-MoO3-B2 O3 glass induced by 250 kHz,800 nm femtosecond laser irradiation%Ag掺杂对高重复频率飞秒激光诱导Gd2 O3-MoO3-B2 O3玻璃析晶的影响

    韩咏梅; 易传祥; 刘丽萍; 张子辰; 钟敏建; 马洪良

    2014-01-01

    We report the influence of the Ag doping on the crystallization ofβ′-Gd2 (MoO4 )3 crystal in the Gd2 O3-MoO3-B2 O3 glasses induced by femtosecond laser irradiation.The fs laser pulses were focused on the surface of Ag-doped Gd2 O3-MoO3-B2 O3 glasses and non-doped Gd2 O3-MoO3-B2 O3 glasses,and the effect of silver on crystallization of b¢-Gd2 (MoO4 )3 crystals in glasses were analyzed.The results indica-ted that the silver greatly enhanced the crystallization of the glass during the fs pulses irradiation.The responsible mechanism for the observed phenomenon can be explained as follows:The glass oxygen bonds are broken by mlti-photon absorption during the femtosecond irradiation,which results in the non-bridging oxygen holes and free electrons.The Ag+ ions capture free electrons to form Ag atoms. Ag atoms move and aggregate to form nanoclaster owning to the thermal driving.Ag nanoclusters act as nuclear and greatly promote the crystallization of the glass.%将800 nm高重复频率250 kHz的飞秒激光分别聚焦到掺Ag和没有掺Ag的Gd2 O3-MoO3-B2 O3玻璃表面,研究掺 Ag对飞秒激光诱导析晶的影响。对激光辐照的区域显微拉曼分析发现对于没掺 Ag 玻璃,诱导玻璃析晶需要的激光功率和辐照时间比掺了 Ag的玻璃要大要长,这说明 Ag的掺入促进了玻璃的析晶。其机理可能为飞秒激光的多光子吸收效应,导致玻璃基质中桥氧键断裂,产生非桥氧空穴和自由电子,玻璃中的 Ag离子捕获电离出来的电子被还原成 Ag 原子,Ag 原子在热动力的驱动下移动聚集形成银纳米颗粒,形成的银纳米团簇作为核促进了钼酸盐玻璃的析晶。

  11. Doping of monocrystalline silicon with phosphorus by means of neutron irradiation at the IEA-R1 research reactor

    The first neutron irradiation experiments with monocrystal silicon in the IEA-R1 research reactor of IPEN are related. The silicon is irradiated with phosphorus producing a N type semiconductor with a very small resistivity variation throughout the crystal volume. The neutrons induce nuclear reactions in Si-30 isotope and these atoms are then transformed in to phosphorous atoms. This process is known as Neutron Transmutation Doping. In order to irradiate the silicon crystals in the reactor, a specific device has been constructed, and it permits the irradiation of up to 2.5'' diameter monocrystals. (author)

  12. Neutron irradiation influence on magnesium aluminium spinel inversion

    Skvortsova, V.; Mironova-Ulmane, N.; Ulmanis, U.

    2002-05-01

    Grown by the Verneuil method MgO · nAl 2O 3 single crystals and natural spinel crystal have been studied using X-ray diffraction and photoluminescence spectra. The fast neutron irradiation of magnesium aluminium spinel leads to the lattice parameter decrease. The bond lengths of Mg-O and Al-O vary with the u-parameter and the lattice parameter. On the other hand, the bond lengths are related with the inversion parameter. Using changes of the lattice parameter during irradiation we have calculated the inversion parameter, which is 15-20%. In the luminescence spectra, the fast neutron radiation (fluence 10 16 cm -2) produces an increase in the intensity ratio of the N- to R-lines by 5-20%. Taking into account that intensity of the N-lines is closely associated with the inversion parameter, it is possible to state that the neutron irradiation causes the increasing of the spinel inversion.

  13. Neutron irradiation influence on magnesium aluminium spinel inversion

    Grown by the Verneuil method MgO · nAl2O3 single crystals and natural spinel crystal have been studied using X-ray diffraction and photoluminescence spectra. The fast neutron irradiation of magnesium aluminium spinel leads to the lattice parameter decrease. The bond lengths of Mg-O and Al-O vary with the u-parameter and the lattice parameter. On the other hand, the bond lengths are related with the inversion parameter. Using changes of the lattice parameter during irradiation we have calculated the inversion parameter, which is 15-20%. In the luminescence spectra, the fast neutron radiation (fluence 1016 cm-2) produces an increase in the intensity ratio of the N- to R-lines by 5-20%. Taking into account that intensity of the N-lines is closely associated with the inversion parameter, it is possible to state that the neutron irradiation causes the increasing of the spinel inversion

  14. Technique for writing of nonlinear optical single-crystal lines in glass

    The technique for the writing of crystal lines in glass by Nd:YAG laser irradiation, selective atom heat processing, is applied to rare-earth (Sm3+, Dy3+) barium borate glasses, and nonlinear optical β-BaB2O4 (β-BBO) crystal lines with a width of ∼5 μm are fabricated. The crystal lines show uniform colors in polarized optical microscope and second-harmonic generation (SHG) measurements. The azimuthal dependence of SHG signals in the crystal lines is the same as that in commercially available β-BBO bulk single crystals. It is demonstrated that the crystal lines written by YAG laser irradiations are β-BBO single crystals with the c-axis orientation along the laser scanning direction

  15. Facts about food irradiation: Chemical changes in irradiated foods

    This fact sheet addresses the safety of irradiated food. The irradiation process produces very little chemical change in food, and laboratory experiments have shown no harmful effects in animals fed with irradiated milk powder. 3 refs

  16. Mobile irradiation robot - computer modelling of the irradiation process

    For irradiation of cultural objects, which are damaged by wood-destroying insects or fungi, with the automatized irradiation robot, the computer code MOBROB1 for irradiation planning was developed and is presented. (author)

  17. Cation disorder in high-dose, neutron-irradiated spinel

    The objective of this effort is to determine whether MgAl2O4 spinel is a suitable ceramic for fusion applications. Here, the crystal structures of MgAl2O4 spinel single crystals irradiated to high neutron fluences [>5·1026 n/m2 (En > 0.1 MeV)] were examined by neutron diffraction. Crystal structure refinement of the highest dose sample indicated that the average scattering strength of the tetrahedral crystal sites decreased by ∼ 20% while increasing by ∼ 8% on octahedral sites. Since the neutron scattering length for Mg is considerably larger than for Al, this results is consistent with site exchange between Mg2+ ions on tetrahedral sites and Al3+ ions on octahedral sites. Least-squares refinements also indicated that, in all irradiated samples, at least 35% of Mg2+ and Al3+ ions in the crystal experienced disordering replacements. This retained dpa on the cation sublattices is the largest retained damage ever measured in an irradiated spinel material

  18. Auto-oscillations of temperature and defect density in ordered binary alloys under irradiation

    A manifestation of antistructural defects created by nuclear irradiation in ordered binary alloys is investigated. Calculations show that the concentration of such defects can be large at typical values of the intensity of irradiation and temperature. The appearance of structural defects can cause instability in a crystal during irradiation. The instability is connected with the acceleration of antistructural defect relaxation due to the heat which releases during this relaxation. The instability leads to the appearance of self-oscillations of the defect density and temperature of a crystals. The manifestation of self-oscillations is investigated

  19. Photopolymerization of C60 crystal synthesized from organic solution

    We have been developing a novel process to synthesize C60 polymers as superior functional materials. Polymerization reactions of C60 precipitated from organic solution were investigated under Free Electron Laser (FEL) irradiation. The two processes: a liquid-liquid interfacial precipitation (LLIP) method and an evaporation technique from supersaturated solution, were studied with a respect of crystal structure and/or Raman spectrum for the precipitates before and after FEL irradiation. It was found that the photopolymerization reaction took place effectively in the LLIP precipitate because of its highly packed molecular crystal structure.

  20. Spatially selected synthesis of LaF3 and Er3+-doped CaF2 crystals in oxyfluoride glasses by laser-induced crystallization

    Oxyfluoride glasses with a small amount of NiO are prepared using a conventional melt quenching technique, and the spatially selected crystallization of LaF3 and CaF2 crystals is induced on the glass surface by irradiations of continuous wave lasers with a wavelength of λ=1064 or 1080 nm. Dots and lines including LaF3 crystals are patterned by heat-assisted (300 deg. C) laser irradiations (λ=1064 nm) with a power of P=1 W and an irradiation time of 10 s for dots and a scanning speed of S=5 μm/s for lines. Lines consisting of CaF2 crystals are also patterned in an ErF3-doped oxyfluoride glass by laser irradiations (λ=1080 nm) with a power of P=1.7 W and a scanning speed of S=2 μm/s, and the incorporation of Er3+ ions into CaF2 crystals is confirmed from micro-photoluminescence spectrum measurements. It is proposed that the lines patterned by laser irradiations in this study are consisted of the composite of LaF3 or CaF2 nanocrystals and SiO2-based oxide glassy phase. It is demonstrated that a combination of Ni2+-dopings and laser irradiations is effective in spatially selected local crystallizations of fluorides in oxyfluoride glasses. - Graphical abstract: This figure shows the polarization optical and confocal scanning laser micrographs for lines obtained by laser irradiations with a laser power of P=1.7 W and a scanning speed of S=2 μm/s in an oxyfluoride glass. It is proposed that the line consists of the composite of CaF2 nanocrystals and oxide glassy phase. This is the first demonstration on the patterning of fluoride crystals in glass by laser irradiations

  1. Irradiation damage in superconductors

    Most superconductors are quite sensitive to irradiation defects. Critical temperatures may be depressed, critical currents may be increased, by irradiation, but other behaviours may be encountered. In compounds, the sublattice in which defects are created is of significant importance. 24 refs

  2. Materials modified by irradiation

    Application of radiation in pharmaceutical sciences and cosmetology, polymer materials, food industry, environment, health camre products and packing production is described. Nanotechnology is described more detailed, because it is less known as irradiation using technology. Economic influence of the irradiation on the materials value addition is shown

  3. Materials modified by irradiation

    Application of radiation in pharmaceutical sciences and cosmetology, polymer materials, food industry, environment, health camre products and packing production is described. Nano-technology is described more detailed, because it is less known as irradiation using technology. Economic influence of the irradiation on the materials value addition is shown

  4. Food irradiation control

    A brief review is given of the control and monitoring of food irradiation with particular emphasis on the UK situation. After describing legal aspects, various applications of food irradiation in different countries are listed. Other topics discussed include code of practice for general control for both gamma radiation and electron beam facilities, dose specification, depth dose distribution and dosimetry. (U.K.)

  5. Food Irradiation in Japan

    Since 1967 research activities on food irradiation in Japan have been carried out under the National Food Irradiation Programme by the Japanese Atomic Energy Commission. The programme has been concentrated on the technological and economical feasibility and wholesomeness testings of seven irradiated food items of economic importance to the country, i.e. potatoes, onions, wheat, rice, “kamaboko” (fish-paste products), “Vienna” sausages and mandarin oranges. By now most studies, including wholesomeness testings of these irradiated food items, have been completed. In Japan, all foods or food additives for sale are regulated by the Food Sanitation Law enforced in 1947. Based on studies made by the national programme, irradiated potatoes were given “unconditional acceptance” for human consumption in 1972. At present, irradiated potatoes are the only food item which has so far been approved by the Minister of Health and Welfare. Unless the Minister of Health and Welfare has declared that items are not harmful to human health on obtaining comments from the Food Sanitation Investigation Council, no irradiated food can be processed or sold. In addition, the import of irradiated foodstuffs other than potatoes from foreign countries is prohibited by law.

  6. Phase stability under irradiation

    Experimental evidences of radiation induced instability are described then it is shown what theoretical approaches are relevant. Radiation induced segregation and precipitation in alloys irradiated at constant chemical composition, precipitate re-solution, order-disorder transition under irradiation and amorphization are examined

  7. Radiation does response of calcium carbonate crystal in marine shells samples

    Changkian, S.; Kaewtubtim, P.

    2002-01-01

    A study of the evolution of element, crystal structure and thermoluminescence signal versus gamma irradiation dose were carried out for calcite shells samples. The composition of element was studied by X-ray fluorescence spectrometer. As identified by X-ray diffraction and SEM/EDS analysis, two polymorphs of calcium-carbonate were extracted: calcite and aragonite. The evolution of TL signal versus gamma irradiation dose using the TL reader (Harshaw 2000) was initially dependent on crystal str...

  8. A preliminary investigation of cell growth after irradiation using a modulated x-ray intensity pattern

    In this study we have investigated a spatial distribution of cell growth after their irradiation using a modulated x-ray intensity pattern. An A549 human non-small cell lung cancer cell line was grown in a 6-well culture. Two of the wells were the unirradiated control wells, whilst another two wells were irradiated with a modulated x-ray intensity pattern and the third two wells were uniformly irradiated. A number of plates were incubated for various times after irradiation and stained with crystal violet. The spatial distribution of the stained cells within each well was determined by measurement of the crystal violet optical density at multiple positions in the plate using a microplate photospectrometer. The crystal violet optical density for a range of cell densities was measured for the unirradiated well and this correlated with cell viability as determined by the MTT cell viability assay. An exponential dose response curve was measured for A549 cells from the average crystal violet optical density in the uniformly irradiated well up to a dose of 30 Gy. By measuring the crystal violet optical density distribution within a well the spatial distribution of cell growth after irradiation with a modulated x-ray intensity pattern can be plotted. This method can be used for in vitro investigation into the changes in radiation response associated with treatment using intensity modulated radiation therapy (IMRT)

  9. A preliminary investigation of cell growth after irradiation using a modulated x-ray intensity pattern

    Bromley, Regina; Davey, Ross; Oliver, Lyn; Harvie, Rozelle; Baldock, Clive

    2006-08-01

    In this study we have investigated a spatial distribution of cell growth after their irradiation using a modulated x-ray intensity pattern. An A549 human non-small cell lung cancer cell line was grown in a 6-well culture. Two of the wells were the unirradiated control wells, whilst another two wells were irradiated with a modulated x-ray intensity pattern and the third two wells were uniformly irradiated. A number of plates were incubated for various times after irradiation and stained with crystal violet. The spatial distribution of the stained cells within each well was determined by measurement of the crystal violet optical density at multiple positions in the plate using a microplate photospectrometer. The crystal violet optical density for a range of cell densities was measured for the unirradiated well and this correlated with cell viability as determined by the MTT cell viability assay. An exponential dose response curve was measured for A549 cells from the average crystal violet optical density in the uniformly irradiated well up to a dose of 30 Gy. By measuring the crystal violet optical density distribution within a well the spatial distribution of cell growth after irradiation with a modulated x-ray intensity pattern can be plotted. This method can be used for in vitro investigation into the changes in radiation response associated with treatment using intensity modulated radiation therapy (IMRT).

  10. A preliminary investigation of cell growth after irradiation using a modulated x-ray intensity pattern

    Bromley, Regina [Northern Sydney Cancer Centre, Radiation Oncology, Royal North Shore Hospital, Sydney, NSW 2065 (Australia); Davey, Ross [Institute of Medical Physics, School of Physics, Sydney University, NSW 2006 (Australia); Oliver, Lyn [Northern Sydney Cancer Centre, Radiation Oncology, Royal North Shore Hospital, Sydney, NSW 2065 (Australia); Harvie, Rozelle [Institute of Medical Physics, School of Physics, Sydney University, NSW 2006 (Australia); Baldock, Clive [Bill Walsh Cancer Research Laboratories, Department of Medical Oncology, Royal North Shore Hospital, Sydney, NSW 2065 (Australia)

    2006-08-07

    In this study we have investigated a spatial distribution of cell growth after their irradiation using a modulated x-ray intensity pattern. An A549 human non-small cell lung cancer cell line was grown in a 6-well culture. Two of the wells were the unirradiated control wells, whilst another two wells were irradiated with a modulated x-ray intensity pattern and the third two wells were uniformly irradiated. A number of plates were incubated for various times after irradiation and stained with crystal violet. The spatial distribution of the stained cells within each well was determined by measurement of the crystal violet optical density at multiple positions in the plate using a microplate photospectrometer. The crystal violet optical density for a range of cell densities was measured for the unirradiated well and this correlated with cell viability as determined by the MTT cell viability assay. An exponential dose response curve was measured for A549 cells from the average crystal violet optical density in the uniformly irradiated well up to a dose of 30 Gy. By measuring the crystal violet optical density distribution within a well the spatial distribution of cell growth after irradiation with a modulated x-ray intensity pattern can be plotted. This method can be used for in vitro investigation into the changes in radiation response associated with treatment using intensity modulated radiation therapy (IMRT)

  11. Issues in food irradiation

    This discussion paper has two goals: first, to raise public awareness of food irradiation, an emerging technology in which Canada has the potential to build a new industry, mainly oriented to promising overseas markets; and second, to help build consensus among government and private sector decision makers about what has to be done to realize the domestic and export potential. The following pages discuss the potential of food irradiation; indicate how food is irradiated; outline the uses of food irradiation; examine questions of the safety of the equipment and both the safety and nutritional value of irradiated food; look at international commercial developments; assess the current and emerging domestic scene; and finally, draw some conclusions and offer suggestions for action

  12. Irradiation of goods

    Mechanical handling apparatus is adapted to handle goods, such as boxed fruit, during a process of irradiation, in palletized form. Palletized goods are loaded onto wheeled vehicles in a loading zone. Four vehicles are wheeled on a track into an irradiation zone via a door in a concrete shield. The vehicles are arranged in orthogonal relationship around a source of square section. Turntables are positioned at corners of the square shaped rail truck around the source selectively to turn the vehicles to align then with track sections. Mechanical manipulating devices are positioned in the track sections opposed to sides of the source. During irradiation, the vehicles and their palletized goods are cylically moved toward the source to offer first sides of the goods for irradiation and are retraced from the source and are pivoted through 900 to persent succeeding sides of the goods for irradiation

  13. Ultra fast melting process in femtosecond laser crystallization of thin a-Si layer

    In this paper, we investigated the mechanism of crystallization induced by femtosecond laser irradiation for an amorphous Si (a-Si) thin layer on a crystalline Si (c-Si) substrate. The fundamental, SHG, THG wavelength of a Ti:Sapphire laser was used for the crystallization process. To investigate the processed areas we performed Laser Scanning Microscopy (LSM), Transmission Electron Microscopy (TEM) and Imaging Pump-Probe measurements. Except for 267 nm femtosecond laser irradiation, the crystallization occurred well. The threshold fluences for the crystallization using 800 nm and 400 nm femtosecond laser irradiations were 100 mJ/cm2 and 30 mJ/cm2, respectively. TEM observation revealed that the crystallization occurred by epitaxial growth from the boundary surface between the a-Si layer and c-Si substrate. The melting depths estimated by Imaging Pump-Probe measurements became shallower when the shorter wavelength was used.

  14. Tailoring crystallinity and configuration of silica nanotubes by electron irradiation

    Taguchi, Tomitsugu, E-mail: taguchi.tomitsugu@jaea.go.jp; Yamaguchi, Kenji

    2015-05-01

    Highlights: •Single-crystal SiO{sub 2} nanotubes were successfully synthesized for the first time. •The single-crystal SiO{sub 2} was α-crystobalite. •Desired area of single-crystal nanotube can be changed to amorphous by electron irradiation. •The configuration of nanotube can be controlled using the focused electron irradiation technique. -- Abstract: SiO{sub 2} nanotubes show potential in applications such as nanoscale electronic and optical devices, bioseparation, biocatalysis, and nanomedicine. As-grown SiO{sub 2} nanotubes in the previous studies always have an amorphous wall, and here we demonstrate the successful synthesis of single-crystal nanotubes for the first time by the heat treatment of SiC nanotubes at 1300 °C for 10 h under low-vacuum conditions. According to TEM observations, the single-crystal SiO{sub 2} was α-cristobalite. We also demonstrate that single-crystal SiO{sub 2} nanotubes can be transformed into amorphous SiO{sub 2} nanotubes by electron beam irradiation. Moreover, we synthesized a crystalline/amorphous SiO{sub 2} composite nanotube, in which crystalline and amorphous SiO{sub 2} coexisted in different localized regions. In addition, for biomedical applications such as drug delivery systems, controlling the configuration of the open end, the diameter, and capsulation of SiO{sub 2} nanotubes is crucial. We can also obturate, capsulate, and cut a SiO{sub 2} nanotube, as well as modify the inner diameter of the nanotube at a specific, nanometer-sized region using the focused electron beam irradiation technique.

  15. Tailoring crystallinity and configuration of silica nanotubes by electron irradiation

    Highlights: •Single-crystal SiO2 nanotubes were successfully synthesized for the first time. •The single-crystal SiO2 was α-crystobalite. •Desired area of single-crystal nanotube can be changed to amorphous by electron irradiation. •The configuration of nanotube can be controlled using the focused electron irradiation technique. -- Abstract: SiO2 nanotubes show potential in applications such as nanoscale electronic and optical devices, bioseparation, biocatalysis, and nanomedicine. As-grown SiO2 nanotubes in the previous studies always have an amorphous wall, and here we demonstrate the successful synthesis of single-crystal nanotubes for the first time by the heat treatment of SiC nanotubes at 1300 °C for 10 h under low-vacuum conditions. According to TEM observations, the single-crystal SiO2 was α-cristobalite. We also demonstrate that single-crystal SiO2 nanotubes can be transformed into amorphous SiO2 nanotubes by electron beam irradiation. Moreover, we synthesized a crystalline/amorphous SiO2 composite nanotube, in which crystalline and amorphous SiO2 coexisted in different localized regions. In addition, for biomedical applications such as drug delivery systems, controlling the configuration of the open end, the diameter, and capsulation of SiO2 nanotubes is crucial. We can also obturate, capsulate, and cut a SiO2 nanotube, as well as modify the inner diameter of the nanotube at a specific, nanometer-sized region using the focused electron beam irradiation technique

  16. Crystallization Behavior of M97 Series Silicone Cushions

    Chien, A.; DeTeresa, S.; Cohenour, R.; Schnieder, J.; LeMay, J.; Balazs, B.

    2000-09-07

    M97 series siloxanes are poly(dimethyl-diphenyl) siloxanes that are reinforced through a mixture of precipitated and fumed silica fillers which are blended in through the addition of a short chain polydimethylsiloxane processing aid. M97 silicones exhibit crystallization at -80.25 C by thermal (modulated differential scanning calorimetry) and mechanical (dynamic mechanical analysis) techniques. Isothermal dynamic mechanical analysis experiments illustrated that crystallization occurred over a 1.8 hour period in silica-filled systems and 2.8 hours in unfilled systems. The onset of crystallization typically occurred after a 30 minute incubation/nucleation period. {gamma}-radiation caused the crystallization rate to decrease proportionally with dosage, but did not decrease the amount of crystallization that ultimately occurred. Irradiation in vacuum resulted in slower overall crystallization rates compared to air irradiation due to increased crosslinking of the polymer matrix under vacuum. Modulated differential scanning calorimetry contrasted the crystallization and melting behavior of pure PDMS versus the M97 base polymer and helped determine which component of the composite was the origin of the crystallization phenomena.

  17. Nanodot formation induced by femtosecond laser irradiation

    The femtosecond laser generation of ZnSe nanoscale features on ZnSe surfaces was studied. Irradiation with multiple exposures produces 10–100 nm agglomerations of nanocrystalline ZnSe while retaining the original single crystal structure of the underlying material. The structure of these nanodots was verified using a combination of scanning transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. The nanodots continue to grow hours after irradiation through a combination of bulk and surface diffusion. We suggest that in nanodot formation the result of ultrafast laser induced point defect formation is more than an order of magnitude below the ZnSe ultrafast melt threshold fluence. This unique mechanism of point defect injection will be discussed.

  18. Thermal diffusivity of neutron-irradiated ceramics

    Fourteen candidate ceramics (eleven oxides and three nitrides) were irradiated in EBR-II to dose between 0.3 and 2.3 x 10 22 n/cm2 (E/sub n/ > 0.1 MeV) at 925, 1015, and 1100 K. Thermal diffusivity (which is approximately proportional to thermal conductivity) was subsequently measured at room temperature by a xenon flash technique. Diffusivity usually decreased sharply as a function of fluence at low doses, but tended toward saturation at higher doses. In most cases lower irradiation temperatures resulted in greater degradations in thermal diffusivity. The magnitude of reduction varied greatly with the ceramic tested, ranging from single-crystal MgAl2O4 (approx. 3%) to polycrystalline silicon oxynitride (93%). In most materials tested the reductions were great enough to raise thermal stresses significantly in low temperature, high thermal flux applications

  19. Onion irradiation - a case study

    Onion irradiation prevents sprouting associated with long term storage. Under the climatic conditions of Central Europe, only that part of onions should be irradiated which is needed to supply the domestic market during the months of May to July. Two types of irradiation plants, a bulk-irradiation and a multipurpose large-scale irradiation plant are used for onion irradiation. Technical data, throughput, cost-related parameters of onion irradiation are discussed. Onion irradiation for long term storage is beneficial to the national economy as well as to the business management. (author) 13 refs.; 11 tabs

  20. Research and Development of Crystal Purification for Product of Uranium Crystallization Process

    and that they make no eutectoid with UNH. On the other hand, it is confirmed that sweating and melting-filtration operations were effective in principle by the experiment with uranium and simulated FP system. After that, its effects verified by beaker scale experiments with the system including plutonium and irradiated fuel. Additionally, engineering scale tests were carried out with a Kureha Crystal Purifier (KCP) type testing device to evaluate that its performance was suitable for UNH purification. This work was supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT). (authors)

  1. Irradiation of fusion materials

    In collaboration with the EFDA (European Fusion Development Agreement), SCK-CEN irradiates several materials in the BR2 reactor at different temperatures and up to different doses to study their mechanical and physical properties during and after the irradiation. These materials are candidates for the construction of different parts of the ITER (International Thermonuclear Experimental Reactor) fusion reactor and of the long-term DEMO (DEMOnstration) reactor. The objectives of research at SCK-CEN in this area are: (1) to irradiate RAFM (Reduced Activity Ferritic Martensitic) steel joints and RAFM ODS (Oxide Dispersion Strengthening) at 300 degrees Celsius up to 2 dpa; (2) to irradiate RAFM steel and different FeCr alloys at 300 degrees C above 1.5 dpa; (3) to irradiate Beryllium and Tungsten specimen at 300 degress C up to 0.75 dpa; (4) to irradiate copper/stainless steel joints at 150 degrees C up to 0.1 dpa; (5) to perform in-situ creep-fatigue tests with CuCrZr specimens under neutron irradiation

  2. Food irradiation 2009

    Food irradiation principles; its main applications, advantages and limitations; wholesomeness, present activities at Ezeiza Atomic Centre; research coordinated by the International Atomic Energy Agency; capacity building; and some aspects on national and international regulations, standards and commercialization are briefly described. At present 56 countries authorize the consumption of varied irradiated foods; trade is performed in 32 countries, with about 200 irradiation facilities. Argentina pioneered nuclear energy knowledge and applications in Latin America, food irradiation included. A steady growth of food industrial volumes treated in two gamma facilities can be observed. Food industry and producers show interest towards new facilities construction. However, a 15 years standstill in incorporating new approvals in the Argentine Alimentary Code, in spite of consecutive request performed either by CNEA or some food industries restricts, a wider industrial implementation, which constitute a drawback to future regional commercialization in areas such as MERCOSUR, where Brazil since 2000 freely authorize food irradiation. Besides, important chances in international trade with developed countries will be missed, like the high fresh fruits and vegetables requirements United States has in counter-season, leading to convenient sale prices. The Argentine food irradiation facilities have been designed and built in the country. Argentina produces Cobalt-60. These capacities, unusual in the world and particularly in Latin America, should be protected and enhanced. Being the irradiation facilities scarce and concentrated nearby Buenos Aires city, the possibilities of commercial application and even research and development are strongly limited for most of the country regions. (author)

  3. Economics of Food Irradiation

    This paper reviews and evaluates current developments relating to the prospects for commercial food irradiation within the United States. The study, recognizes that one cannot generalize about the prospects for food irradiation either by process or product. Both technical and economic potentials vary widely for different food products subjected to the same or different types of treatment. Food irradiation processes and products are evaluated. Recent studies concerned with the economics of food irradiation are briefly reviewed and evaluated and findings and conclusions relating to economic potentials summarized. Industry reactions to a proposed pilot plant meat irradiator, sponsored by the U.S. Army and U.S. AEC and coordinated by the Department of Commerce, are discussed and factors which will determine the future direction, extent and commercial success of food preservation by ionizing irradiation are analysed. Developments in all these categories are essential for success, and if not achieved would be limiting factors. Nevertheless, the successful and profitable marketing of irradiated foods must finally be dependent upon customer acceptance and favourable cost versus benefit relations. Benefits will include lower costs and higher profits through spoilage reductions, extensions of shelf-life and shipping distances, market expansions, and quality Improvements. Ultimately, the economic success of this new technology must depend upon the clear demonstration that these benefits will exceed the additional processing costs by a margin sufficient to induce the necessary private investments and willingness to accept related risks in this new field. (author)

  4. Robustness Test of a Silicon Strip Crystal for Crystal-Assisted Collimation Studies in the LHC

    Lechner, A; Di Castro, M; Lendaro, J; Loprete, F; Losito, R; Maglioni, C; Masi, A; Montesano, S; Perillo-Marcone, A; Roguet, P S; Wollmann, D; Sancho, J B; Burkart, F; Scandale, W; Gavrikov, Y; Guidi, V; Mazzolari, A

    2013-01-01

    Over the past years, the UA9 experiment has successfully demonstrated the viability of enhancing the collimation efficiency of proton and ion beams in the SPS by means of bent crystals. An extension of UA9 to the LHC has been recently approved. The conditions imposed by the LHC operational environment, in particular the tremendous energy density of the beam, require a reliable understanding of the crystal integrity in view of potential accident scenarios such as an asynchronous beam dump. For this purpose, single pulse irradiation tests have been performed at the CERN-HiRadMat facility to examine the mechanical strength of a silicon strip crystal in case of direct beam impact. The tests were carried out using a 440 GeV proton beam of σ=0.5 mm transverse size. Individual pulse intensities reached up to 3×1013 protons, where a significant fraction is assumed to have impacted on the crystal. First visual inspections revealed no macroscopic damage to the crystal. Complementary post-irradiation tests are foresee...

  5. Gamma irradiation of corn starches with different amylose-to-amylopectin ratio

    Corn starches with different amylose-to-amylopectin ratio (waxy, normal, Hylon V, and Hylon VII) were treated with five doses of gamma irradiation (1, 5, 10, 25, and 50 kGy). The effects of gamma irradiation on the physico-chemical properties of starch samples were investigated. Waxy samples showed an increase of amylose-like fractions when irradiated at 10 kGy. The reduction in apparent amylose content increased with amylose content when underwent irradiation at 25 and 50 kGy. Low amylose starches lost their pasting ability when irradiated at 25 and 50 kGy. Results from thermal behavior and pasting profile suggested that low level of cross-linking occurred in Hylon VII samples irradiated at 5 kGy. Severe reduction in pasting properties, gelatinization temperatures and relative crystallinity with increasing irradiation intensity revealed that waxy samples were affected more by gamma irradiation; this also indicated amylopectin was the starch fraction most affected by gamma irradiation. Alteration level was portrayed differently when different kind of physico-chemical properties were investigated, in which the pasting properties and crystallinity of starches were more immensely influenced by gamma irradiation while thermal behavior was less affected. Despite the irradiation level, the morphology and crystal pattern of starch granules were found remain unchanged by irradiation. (author)

  6. Pressure cryocooling protein crystals

    Kim, Chae Un; Gruner, Sol M.

    2011-10-04

    Preparation of cryocooled protein crystal is provided by use of helium pressurizing and cryocooling to obtain cryocooled protein crystal allowing collection of high resolution data and by heavier noble gas (krypton or xenon) binding followed by helium pressurizing and cryocooling to obtain cryocooled protein crystal for collection of high resolution data and SAD phasing simultaneously. The helium pressurizing is carried out on crystal coated to prevent dehydration or on crystal grown in aqueous solution in a capillary.

  7. Irradiation in action

    The extent to which food irradiation takes place and the regulations governing the process in America, Brazil, Chile, and European countries is reported. The development and operation of a pilot plant built in Holland to test the application of the process to the sterilization of medical supplies and certain foods and the setting up and operation, by Gammester, of a special food irradiation plant in 1982, is described. In this plant 36 foods, mainly dry ingredients such as spices, dried vegetables, egg powder and blood proteins are irradiated. Research looks promising for the future. The implementation of international legal acceptance and more public information is stressed. (U.K.)

  8. Alaskan Commodities Irradiation Project

    The ninety-ninth US Congress commissioned a six-state food irradiation research and development program to evaluate the commercial potential of this technology. Hawaii, Washington, Iowa, Oklahoma and Florida as well as Alaska have participated in the national program; various food products including fishery products, red meats, tropical and citrus fruits and vegetables have been studied. The purpose of the Alaskan study was to review and evaluate those factors related to the technical and economic feasibility of an irradiator in Alaska. This options analysis study will serve as a basis for determining the state's further involvement in the development of food irradiation technology. 40 refs., 50 figs., 53 tabs

  9. A comparison of the magnetic properties of radiation damaged or Co implanted ZnO single crystals

    Werner, Z. [National Centre for Nuclear Research, Otwock (Poland); Gosk, J. [Faculty of Physics, Warsaw University, Warsaw (Poland); Faculty of Physics, Warsaw Technical University, Warsaw (Poland); Twardowski, A. [Faculty of Physics, Warsaw University, Warsaw (Poland); Barlak, M.; Pochrybniak, C. [National Centre for Nuclear Research, Otwock (Poland)

    2015-09-01

    Highlights: • Co implantation in ZnO single crystal introduces paramagnetic and ferromagnetic phases. • Electron and proton irradiations have no effect on crystal magnetic properties. • Co ions seem to stabilize the radiation defects. - Abstract: To elucidate the interaction between defects and transition metal impurities in creating magnetic properties in wide band-gap semiconductors, single crystals of ZnO were irradiated with high-energy electrons, protons and Co ions. Magnetization of samples was measured before and after room temperature irradiation. The measurements reveal that only Co implantation creates measurable magnetization, which is related to the simultaneous introduction of defects. Consequences of the experimental results are discussed.

  10. Low temperature irradiation effects on iron boron based amorphous metallic alloys

    Three Fe-B amorphous alloys (Fe80B20, Fe27Mo2B20 and Fe75B25) and the crystallized Fe3B alloy have been irradiated at the temperature of liquid hydrogen. Electron irradiation and irradiation by 10B fission fragments induce point defects in amorphous alloys. These defects are characterized by an intrinsic resistivity and a formation volume. The threshold energy for the displacement of iron atoms has also been calculated. Irradiation by 235U fission fragments induces some important structural modifications in the amorphous alloys

  11. Field ion microscopy of defects in tungsten caused by 140 keV proton irradiation

    The disturbances in the crystal structure of tungsten during its bombardment with 140 KeV protons (the integral dose of irradiation is 2.1016 protons/cm2, the specimens were irradiated out of the microscope at a room temperature) with the auto-ionic helium microscope operating at 78 deg K were investigated. The random pinpoint defects and small pores in the irradiated specimens were observed. The reasons for discrepancy between the estimated concentration of single displaced atoms and the concentration determined by reference to the autonomous images of the irradiated specimens are discussed

  12. Facts about food irradiation: Irradiated foods and the consumer

    This fact sheet discusses market testing of irradiate food, consumer response to irradiated products has always been positive, and in some countries commercial quantities of some irradiated food items have been sold on a regular basis. Consumers have shown no reluctance to buy irradiated food products. 4 refs

  13. Scintillation efficiency of CsI(Tl) crystals

    We have a program to survey the absolute scintillation efficiency and the energy resolution of popular scintillation crystals such as NaI(Tl), CsI(Tl), CdWO4 and BGO for gamma ray irradiation to obtain scintillation crystals with better energy resolution. It has been said that, among the popular scintillation crystals, NaI(Tl) is the best in energy resolution and is one of the largest in photon output and that CsI(Tl) crystals have the similar energy resolution and similar light output to those of NaI(Tl). We already reported the scintillation efficiency and the energy resolution of NaI(Tl) crystals elsewhere. CsI(Tl) crystal is less fragile and less deliquescent that NaI(Tl) crystal. Recently we started the study of the CsI(Tl) crystals and found that the light output is no less than that of NaI(Tl) crystals, though the result is preliminary. In this report we will describe the method of experiment and give the light output of CsI(Tl) crystals in term of Ws values, the average energy to produce one scintillation photon. (author)

  14. Microstructural characterization of second phase irradiated Zircaloy-4 particles

    X-ray diffraction diagrams of neutron irradiated Zircaloy-4 were obtained at the LNLS with the aim to obtain bulk information about the amorphization process in which the Zircaloy-4 second phase particles (SPPs) undergoes due to neutron irradiation. Owing to the low concentration of the SPPs in the alloy (∼0.4 V %), no data regarding to the bulk were obtained until now. The synchrotron experiences allowed to detect five of the more intense lines of the phase C 14 (SPPs structure) in unirradiated Zircaloy-4: (110) θ, (103) θ, (112) θ, (201) θ and (004) θ in the 34 degrees ≤ θ2≤45 degrees Bragg angle range and others of minor intensity. The diagrams of the samples irradiated at moderate doses (1020n/cm2) show these lines even in the as received samples. In contrast, none of these lines are observed for high fluence samples (∼1022neutrons/cm2). In addition, in similar high fluence samples annealed 24 h or 72 h at 600 C degrees the intensity rises just at the 2q range where the C 14 lines were observed, showing a wide peak. That peak is interpreted as a result of the superposition of unresolved diffraction lines corresponding to the Zircaloy SPPs which are in a reconstitution process of crystallization. Analytical Electron Microscopy techniques were used, in order to study the effects on the Zircaloy-4 SPPs and compared with samples of the same material without irradiation. Spots in SAD patterns of non irradiated SPPS, evidences the presence of a C 14 structure, but in irradiated SSP SAD patterns evidences the beginning of an amorphization process. Another important feature to point out is the different Fe / Cr ratio presented in both irradiated and non irradiated SSPs. In non irradiated precipitates the Fe / Cr ratio is approximately 1.5, while in irradiated precipitates the Fe / Cr ratio becomes near 1.0. (author)

  15. The pushing gate in a planar Coulomb crystal using a flat-top laser beam

    We propose a pushing gate for entangling two ions in a planar Coulomb crystal in the view of realizing large-scale quantum simulations. A tightly focused laser is irradiated from the direction perpendicular to the crystal plane and its spatial intensity profile generates a state-dependent force. We analyze the error sources in this scheme and obtain low infidelity.

  16. Modulation Instability in Biased Photorefractive-Photovoltaic Crystals

    LU Ke-Qing; ZHAO Wei; YANG Yan-Long; SUN Chuan-Dong; GAO Hong-Wen; LI Jin-Ping; ZHANG Yan-Peng

    2004-01-01

    @@ We show the modulation instability of broad optical beams in biased photorefractive-photovoltaic crystals under steady-state conditions. This modulation instability growth rate depends on the external bias field, the bulk photovoltaic effect, and the ratio of the optical beam intensity to that of the dark irradiance. Under appropriate conditions, this modulation instability growth rate is the modulation instability growth rate studied previously in biased photorefractive-nonphotovoltaic crystals, and the modulation instability growth rate in open- and closed-circuit photorefractive-photovoltaic crystals can be predicted.

  17. Liquid crystal photoalignment material based on chloromethylated polyimide

    We report a liquid crystal photoalignment material with high photosensitivity and excellent thermal stability. The chloromethylated aromatic polyimide exhibited defect-free homogeneous alignment of liquid crystals upon irradiation of polarized deep ultraviolet (UV) for 50 s. The aligning ability of the film was retained up to 210 deg. C, and the cell containing liquid crystals could be stored at 85 deg. C for more than 14 days without any deterioration. FT-IR and UV-vis spectra confirmed that the alignment was induced by photodecomposition of polyimide, drastically accelerated by the introduction of chloromethyl side group

  18. Proton and gamma radiation tests on nonlinear crystals

    We report on the results of proton and gamma irradiation tests performed on nonlinear crystals for second- (SHG) and third-harmonic generation. β-barium borate (BBO), lithium triborate (LBO), and KTP crystals were exposed to three different energies of proton radiation (8, 70, and 300 MeV) and incremental doses of gamma radiation (up to 139 krad) in order to investigate the change in SHG performance and transmission spectra. BBO and LBO crystals turned out to be a suitable choice for SHG under radiative conditions

  19. Defect transformation in GSGG crystals during chromium ion activation

    Absorption and induced absorption spectra, dose dependence of induced absorption, thermoluminescence of GSGG crystals, nominally pure and activated with chromium and neodymium ions in different concentrations, are investigated. It is shown that it is chromium ion presence in large concentration that decreases the induced coloration in GSGG crystals after γ-irradiation at 300 K. Optimum concentration of chromium ions for the minimum of induced coloration are found. The mechanism of decrease of induced coloration consisting in Fermi level displacement by chromium ion activation is established. Defect concentration and localization and recombination possibilities of electrons and holes in GSGG crystals are estimated by computer simulation

  20. Laser-induced assembly of gold nanoparticles into colloidal crystals

    Micron-sized colloidal crystals comprised of gold nanospheres have been synthesized directly from a gold nanoparticle/methyl methacrylate colloid by application of a 514 nm laser at 500 mW. An array of colloidal crystals can be created by translation of the glass substrate under the laser beam, after 2 min of irradiation at each site. We demonstrate through a series of control experiments and calculations that plasmon-induced, localized heating of the gold nanoparticles contributes to the mechanism responsible for the formation of these colloidal crystals