Influence Of Radiation Damage Research Articles

Thermally induced phase decomposition and nanocrystal formation in murataite ceramics

Synthetic murataite, an isometric derivative of the fluorite structure, has been proposed as a host phase for the immobilization of lanthanides and actinides. In this study, murataite polytypes have been synthesized in the system Ca–Ti–U–Mn–Al–Zr–Fe–Ce–O by melting oxide mixtures at 1400–1600 °C followed by crystallization under slightly oxidizing conditions. The phase and structural compositions of the synthetic murataite ceramics were characterized by energy dispersive spectroscopy and transmission electron microscopy (TEM). The thermal stability was studied by in-situ heat treatment under TEM observation. The influence of radiation damage as a result of alpha-decay events of the incorporated actinides on the thermal stability of the synthetic murataite ceramics was simulated by 1 MeV Kr+ irradiation. A thermally induced, Fe-rich phase decomposition and nanocrystal formation was observed in murataite ceramics under vacuum above 573 K. Ce was closely associated with the Fe-rich phase in the Ce-incorporated murataite ceramics. Ion beam irradiation-induced amorphization inhibited the process of phase decomposition. The effects of thermally induced phase decomposition on the radiation resistance of murataite ceramics utilized as potential nuclear waste forms for the immobilization of actinides and, particularly plutonium, were also analyzed.

Electron Binding to Nucleic Acid Bases. Experimental and Theoretical Studies. A Review

An in-depth knowledge of an excess electron binding mechanism to DNA and RNA nucleobases is important for our understanding of radiation damage influence on the biological functions of nucleic acids, as well as for the possible use of DNA molecules as wires in molecular electronic circuits. The of anions created by electron attachment to individual nucleic acid bases is discussed in detail. The principles of the experimental and theoretical approaches to the description of these anions are outlined, and the available results concerning valence- and dipole-bound anions of nucleic acid bases are reviewed. A review with 167 references.

Evaluation of Irradiation Effect on Fatigue Performance of Copper Alloys for High Heat Flux Applications

ABSTRACTThe influence of radiation damage on the fatigue performance of two selected copper alloys, a dispersion-strengthened CuAl-25 alloy and a precipitation-hardened CuCrZr alloy, was analyzed. The fatigue lives of the two alloys were predicted using their tensile properties before and after irradiation by the Universal Slopes method. The predicted lives are compared with experimental results, and the feasibility of using tensile properties to predict fatigue lives following irradiation is examined. The fatigue performance of these two copper alloys was degraded due to radiation exposure, but the radiation effect on the fatigue performance was not as severe as on the tensile properties. The life prediction agrees reasonably well with the measured fatigue response.

Device simulations of silicon detectors: a design perspective

Device simulation allows for accurate analysis of device behavior, accounting for several physical details that cannot easily be taken into account within compact, equivalent-circuit models. This is especially true for some issues typical of the design of silicon radiation detectors, where silicon properties are exploited in a non-conventional way and radiation damage raises severe reliability concerns. In this paper, a couple of significant applications of device simulation to the investigation and design of advanced solid-state radiation sensors are presented. More specifically, (i) radiation damage influence on detectors operating at cryogenic temperatures is successfully modeled and (ii) features of an innovative scheme for CMOS active pixel sensors are analyzed by means of mixed-mode simulation tools. From these examples, the usefulness and potentiality of advanced simulation techniques in the perspective of radiation detectors can be appreciated.

Influence of radiation damage on the performance of a lead/scintillator calorimeter investigated with 1–6 GeV electrons

The influence of radiation damage on energy resolution, linearity and uniformity of an electromagnetic lead/scintillator calorimeter was studied experimentally with 1–6 GeV electrons. Plastic scintillators and wavelength shifter bars were irradiated uniformly with γ rays. Both were identical with those of the ZEUS uranium calorimeter. The attenuation length of the scintillators was determined from bench tests of single scintillator tiles and from beam tests of the whole calorimeter. After exposure to a dose of 10 kGy the attenuation length of the scintillators decreased by a factor of 2. The experimental results show that the irradiation of the nearly 2 m long wavelength shifter bars affects the calorimeter much more than the damage of the scintillators which were only 19 cm long. Damaged and undamaged sections of the calorimeter were scanned with a moving radioactive γ source ( 60Co). The results demonstrate that the 60Co monitor system is a very precise tool to detect radiation damage in a sampling calorimeter.

Organic semiconductor interfaces: Discrimination between charging and band bending related shifts in frontier orbital line-up measurements with photoemission spectroscopy

Gaq 3 is a promising luminescent organic semiconductor for applications in organic light emitting diodes. The frontier orbital alignment at the tris (8-hydroxyquinolinato) gallium (Gaq3)/Pt organic Schottky contact was determined by combined x-ray and ultraviolet photoemission spectroscopy (XPS, UPS) measurements. A Gaq3 thin film was deposited in several steps on a previously Ar+ sputtered pure Pt foil. After each growth step, the sample was characterized by XPS and UPS. The combination of XPS and UPS measurements allows the precise evaluation of the interface dipole independent from the simultaneously occurring band bending at the interface and charging artifacts. The measurements show that the Pt/Gaq3 interface has a strong dipole of 0.71 eV indicating the transfer of negative charge from Gaq3 to Pt. Due to the large work function difference between Pt and Gaq3, strong band bending occurred. At Gaq3 coverages higher than 128 Å strong charging shifts occurred in the overlayer related emission lines which were identified by measuring the high binding energy cutoff (secondary edge) of both the XP and UP spectra. Due to the several magnitudes difference between the x-ray and ultraviolet source photon intensities, differences between the high binding energy cutoff positions of both measurements allow to pinpoint charging shifts with high sensitivity. In order to investigate the possible influence of radiation damage to the Gaq3 film, a single growth step control film of Gaq3 of the same thickness as in the multi-step orbital line-up procedure was deposited. The comparison of XPS peak intensities and positions suggest that no significant chemical alteration occurred during the photoemission spectroscopy measurements of the multi-step deposition experiment. However, the doping level of the layer may have changed due to the radiation exposure during the measurements.

Influence of radiation damage on BGO scintillation properties

Aboard INTEGRAL, the next medium-size γ-ray mission of the European Space Agency (ESA), a high-resolution Ge-spectrometer array with a BGO anticoincidence shield and imaging capability will be flown. The influence of the radiation damage on the photoelectron yield of the BGO scintillators due to the radiation environment in the orbit, i.e. γ-rays, electrons and protons from the radiation belts and the cosmic diffuse radiation, was investigated. Irradiation tests with doses equivalent to the orbit conditions were performed and the photoelectron yields of different BGO crystals were measured. It was found that for equal doses the reduction of the photoelectron yield varies strongly for the crystals of different manufacturers. Furthermore, electromagnetic radiation affects the photoelectron yield much stronger than particle radiation. A possible explanation is given by interpreting the effect due to γ-rays primarily as damage of the electronic structure of the BGO, whereas the particle radiation damages mainly the crystal structure.

Anomalous Dispersion with Edges in the Soft X-ray Region: First Results of Diffraction from Single Crystals of Trypsin Near the K-Absorption Edge of Sulfur

Anomalous dispersion of X-ray diffraction at wavelengths near the X-ray K-absorption edge of sulfur at wavelengths around 5 A has been applied to single crystals of trypsin obtained from an ammonium sulfate solution. The multiwavelength anomalous-dispersion method based on 775 unique reflections (+183 Bijvoet mates) measured at three wavelengths near the K-absorption edge of sulfur in trypsin (two methionines and disulfide bridges of six cystines) reproduces the known features of the trypsin structure of a resolution of 4 A. It appears that there is anisotropic anomalous scattering from the disulfide bridges of cystine. The multiwavelength anomalous solvent contrast shows up at wavelengths near the K-absorption edge of the sulfate ions, which is shifted by 10 eV to higher energies with respect to that of sulfur in trypsin. The influence of the complex contrast of trypsin in 2.5 M ammonium sulfate on the dispersion of a low-order reflection is analyzed. The measurement of anomalous dispersion of X-ray diffraction at long wavelengths beyond 5 A requires a special diffractometer, the features of which are presented. An outstanding one is a detector system consisting of four multiwire proportional counters. Its efficiency is compared with that of imaging plates. The influence of radiation damage with soft X-ray diffraction from single crystals of trypsin is presented and possible remedies are discussed.

Low-temperature interlaminar shear strength of reactor irradiated glass-fibre-reinforced laminates

Glass-fibre-reinforced plastics (GFRPs) are candidate insulating materials for superconducting magnet coils in future fusion reactors. Therefore, the influence of radiation damage (gamma and fast neutrons) especially on the interlaminar shear behaviour of these materials has to be investigated carefully. Different types of GFRP laminate (two-dimensional E- or S-glass fibre reinforcements, epoxy or polyimide resins) have been irradiated at room temperature in the TRIGA reactor (Vienna, Austria) and at 5 K in the FRM Munich (Garching, Germany) up to a neutron fluence of 5 × 10 22m −2 ( E > 0.1 MeV) prior to short-beam-shear (SBS) testing at 77 K. After low-temperature irradiation, half of the samples were subjected to a warm-up cycle to room temperature before testing at 77 K. Results on the influence of different radiation sources, irradiation temperatures and annealing cycles as well as the boron content of some laminates on the interlaminar shear strength (ILSS) are compared and discussed, together with microstructural observations made with a scanning electron microscope.

Influence of radiation damage in graphite and beryllium materials on hydrogen retention

In the present work, based on a thermodynamic analysis of hydrogen-beryllium interaction, a new approach for hydrogen behaviour in beryllium is presented. This approach is based on the assumption that "true" solubility of hydrogen in beryllium is extremely low and endothermic trapping in impurities and gas filled bubbles is responsible for hydrogen inventory in beryllium at temperatures higher than 700 K. Hydrogen implanted into beryllium at elevated temperatures is assumed to be retained as H-atoms trapped at impurities and as molecular H2 inside pores and bubbles.The Langmuir type adsorption and dangling sp2-bonds relaxation are proposed for the hydrogen-graphite interaction. Three kinds of traps are proposed: carbon interstitial loops with an adsorption enthalpy of −4.4eV/H2 (Trap 1); graphite network edge atoms with an adsorption enthalpy of −2.3eV/H2 (Trap 2); basal planes adsorption sites with enthalpy of +2.43eV/H2 (Trap 3). The sorption capacity of every kind of graphite could be described with its own unique set of traps. The irradiation with neutrons or energetic carbon ions increases the number of traps. At damage level of ~1 dpa under room temperature irradiation the concentration of traps 1 and 2 reaches 1500 and 500 appm respectively.Estimations of hydrogen inventory for ITER conditions for both beryllium and graphite are provided.

Influence of radiation damage on the hyperfine field of triton irradiated nickel foils

The recently observed Mossbauer effect in63Ni enables the study of the hyperfine field in nickel with high resolution. In the present paper, the line broadening of the Mossbauer resonance is analyzed in order to study the influence of radiation damage on the magnetic hyperfine field in64Ni foils. Each of these foils was irradiated by tritons at 15 K with a total current integral of 2.4 μA h in order to produce the short-lived63Co sources (T1/2=27 s). An upper limit of 4.6 kG was estimated for the standard deviation of the magnetic hyperfine field distribution which resulted from the accumulated radiation damage. For the annealed absorber material the standard deviation of the magnetic field is less than 53 G.

Radiation-induced damage and its recovery to thermoluminescence sensitivity of LiF:Mg, Cu, P crystal

Abstract Lif:Mg, Cu, P polycrystal suffers a serious damage to its thermoluminescence (TL) sensitivity when exposed to high-level dose of 60Co gamma rays. After an exposure up to 106 Gy, the relative TL response of the peak (210°C) per unit absorbed dose is only 1.40 × 10−6 as compared with that exposed to low dose. While the residual peak is eliminated by annealing at 400°C, the thermoluminescent sensitivity is about 14% of the original one for a test dose of 0.01 Gy. High temperature annealing procedures have been investigated to remove the influence of radiation damage on its sensitivity at low dose. Results show that after annealing at 600°C for 30 min, the TL sensitivity of the samples exposed to high-level dose can be restored. The procedure of thermal treatment is described in detail. A possible explanation for the recovery is discussed.

Tensile strength of fiber reinforced plastics at 77 K irradiated by various radiation sources

The influence of radiation damage on the mechanical properties of fiber reinforced plastics (FRPs) has been investigated. Three aspects of our results will be discussed in detail. The first is related to an assessment of the tensile strength and its radiation dependence under the influence of strongly varying radiation conditions; the second to low temperature (~ 5 K) reactor irradiation of selected materials. In this case, identical sets of tensile test samples were transferred into the tensile testing machine, one without warming-up to room temperature and the other after an annealing cycle to room temperature. Finally, a comparison between the radiation response of different materials shows that the tensile properties of a three-dimensionally reinforced bismaleimide degrade least under all irradiation conditions.

Localized anodic oxide films on Si: preparation and properties

The anodic oxidation of silicon in a 0.04 N solution of potassium nitrate in ethylene glycol with small amounts of water is a hole consuming process. Therefore, n-type silicon, anodically biased, behaves in the dark in many respects as a reverse biased diode. Under steady-state conditions a certain, in general a very low electrochemical reaction rate is established. If the sample is locally implanted with ions or locally illuminated the ion implanted or illuminated regions can serve as an additional source of minority carriers and show a faster oxidation rate than the nonimplanted or nonilluminated areas. The influence of radiation damage as well as of a focused laser beam (radius 4 μm) on the local oxidation of anodically biased n-type silicon is discussed. The electrophysical properties of the silicon/anodic oxide interface are investigated by forming Metal/Oxide/Semiconductor (MOS) structures.

Influence of radiation damage on the cyclic crack resistance of austenitic steels and alloys (review)

The results of experimental investigations of the cyclic crack resistance of austenitic steels and nickel alloys in the annealed and cold-worked conditions at various temperatures with various dosages of radiation damage are analyzed and summarized. In the absence of rheological processes at a crack tip irradiation reduces crack growth in cyclic loading and for steels a correlation of this effect with the degree of radiation strengthening is observed. In weld joints after irradiation the cyclic crack resistance may drop. High-temperature aging of annealed steels promotes a decrease in crack growth rate and preliminary cold working does not play a significant positive role in preservation of cyclic crack resistance after irradiation in loading at reduced temperatures and has a negative influence at temperatures above 600°C. A decrease in loading frequency or the presence of holds in the cycle with a stress intensity factor equal to Kmax significantly reduces fatigue crack growth resistance and radiation damage strengthens this effect.

Influence of radiation damage on Mössbauer effect probability

We calculate the dependence of the Mossbauer-effect probability on the concentration of the amorphised phase in irradiatede materials. The calculated dependence is compared with experimental data for ferrite-garnets irradiated by fast neutrons. A nice agreement has been found between the theory and the experimental results.

Hydrogen trapping and transport in carbon

The present paper reviews phenomena associated with the implantation of hydrogen isotopes into graphite and carbonized layers, with particular emphasis on the implanted layer, i.e. the depth range where the injected atoms are deposited. Different modifications of graphite and carbonaceous layers are characterized with respect to their structure, and the influence of radiation damage is treated. Recent evidence is demonstrated for the occurrence of local hydrogen and methane molecule formation, and the diffusion of these molecules through the bulk. The ‘saturated layer’ formed during hydrogen implantation is modelled by a dynamic balance between ion deposition and trapping, thermal or ion-induced detrapping, and local recombination and molecular diffusion. Corresponding calculations yield satisfactory fits to monoenergetic implantation and thermal effusion experiments. The inventory in the saturated layer is only a small contribution to the total hydrogen inventory of carbon walls in fusion machines. Some recycling phenomena can be explained by the physics of the implanted layer, whereas others, like wall pumping, require different mechanisms for their explanation.

The influence of radiation damage on the superconducting properties of thin film YBa/sub 2/Cu/sub 3/O/sub 7- delta /

The authors report measurements of the effects of high-energy ( approximately 60 MeV) H and He ion irradiation of thin films of YBa/sub 2/Cu/sub 3/O/sub 7- delta / produced by plasma-arc spray and laser evaporation, and of low-energy ( approximately 10 MeV) B and N ion irradiation of laser evaporated films. The observed changes in the resistance versus temperature behavior for H and He ion irradiation of the plasma-arc spray films are much more dramatic than that observed for films produced by other techniques and resembles, qualitatively, a bond percolation threshold. In contrast, high-energy H and He ion irradiation of the laser-evaporated films resulted in a negligible change in the resistance-temperature behavior. Low-energy B and N ion irradiation of laser-evaporated films gradually lowered the completion temperature of the superconducting transition. >

Influence of irradiation defects on the properties of incommensurate insulators

Abstract This paper is a short review on experiments on the influence of radiation damage in incommensurate insulators. The main results are discussed on the basis of existing models.

Another view of the control of the isotopic composition of initial DT plasmas in tokamaks

The present paper reviews phenomena associated with the implantation of hydrogen isotopes into graphite and carbonized layers, with particular emphasis on the implanted layer, i.e. the depth range where the injected atoms are deposited. Different modifications of graphite and carbonaceous layers are characterized with respect to their structure, and the influence of radiation damage is treated. Recent evidence is demonstrated for the occurrence of local hydrogen and methane molecule formation, and the diffusion of these molecules through the bulk.The ‘saturated layer’ formed during hydrogen implantation is modelled by a dynamic balance between ion deposition and trapping, thermal or ion-induced detrapping, and local recombination and molecular diffusion. Corresponding calculations yield satisfactory fits to monoenergetic implantation and thermal effusion experiments.The inventory in the saturated layer is only a small contribution to the total hydrogen inventory of carbon walls in fusion machines. Some recycling phenomena can be explained by the physics of the implanted layer, whereas others, like wall pumping, require different mechanisms for their explanation.