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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. 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.

  13. 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

  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. 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

  16. 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.

  17. 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

  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. 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.

  17. 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

  18. 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

  19. 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

  20. 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.

  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. 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

  13. 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)

  14. 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.)

  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. 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

  8. 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.

  9. 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

  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. 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

  3. 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.

  4. 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

  5. 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.

  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. 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.)

  9. 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.

  10. 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)

  11. 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

  12. 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...

  13. 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...

  14. 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)

  15. 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)

  16. 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.

  17. 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

  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. 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.)

  11. 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.)

  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

    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.

  18. 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.

  19. 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.

  20. 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

  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. 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

  3. 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.)

  4. 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.

  5. 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.

  6. 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...

  7. 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.

  8. 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)

  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. 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

  15. 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%.

  16. 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

  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. 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

  2. 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

  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. 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

  5. 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)

  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. 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...

  10. 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

  11. 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

  12. 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.

  13. 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

  14. 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

  15. 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

  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. 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

  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. 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).

  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. 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.

  2. 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)

  3. 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.

  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. 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

  1. 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

  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. 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

  15. 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%.

  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. 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

  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. 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...

  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. 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

  2. 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

  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. 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

  3. 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

  4. 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

  5. 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

  6. 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.).

  7. 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.)

  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.