Effect of gamma irradiation on undoped and uranium doped calcium fluoride crystals

Color centers in undoped and U³⁺-doped CaF₂ crystals induced by γ-irradiation with different doses were studied by differential absorption and Raman spectra. Multiple color centers and conversion among them were caused in undoped CaF₂ with the creation of radiation defects. In U³⁺:CaF₂ crystal, trivalent uranium was demonstrated to act as hole trap in the process of γ-irradiation, which was ionized to tetravalent. This process was accompanied by the formation of F₂⁺ centers, but without additional background absorption due to radiation defects.     

Effect of irradiation history on the preparation of laser induced periodic microstructure on polyimide surface

Although UV laser is proved to be an effective tool to prepare microstructure on polymer surface, laser ablation accompanied by the formation of laser induced periodic surface structure (LIPSS) limits its application in many fields. The purpose of this report is to investigate the effect of pre-irradiation in advance, using a low-fluence laser, on the LIPSS formation. The properties of pre-irradiated PI films were characterized by X-ray photoelectron spectroscopy (XPS), surface tension based on the contact angle measurements and UV-vis spectra. It was found that pre-irradiation at low fluence led to the changes in surface property such as chemical components though no LIPSS was formed. As a result, threshold of LIPSS formation on such pre-irradiated PI film decreased and fine LIPSS with deeper amplitude was obtained.     

Effect of amplitude and frequency of ultrasonic irradiation on morphological characteristics control of calcium carbonate

We have previously reported on the morphological control of calcium carbonate by changing synthetic conditions such as temperature, pH and degree of supersaturation in liquid reaction. The present study reports the effect of amplitude and frequency of ultrasonic irradiation on the particle size of calcium carbonate using a horn type ultrasonic apparatus at two different frequencies. The calcium carbonate precipitated by mechanical stirring had a particle size of about 20 μm. By contrast, the particle size of vaterite formed under ultrasonic irradiation was about 2 μm, with a specific surface area of 25–30 m²/g. The major polymorph of calcium carbonate formed by ultrasonic irradiation was vaterite with some calcite present. For 40 kHz ultrasonic irradiation, the specific surface area of the calcium carbonate increased with increasing amplitude. The particle size of vaterite formed at this frequency was about 2 μm, and its distribution was sharper than that obtained at 20 kHz. The mode diameter of the synthesized vaterite was found to decrease with increasing amplitude at 40 kHz.     

Effects of low temperature irradiation with heavy ions on superconductor niobium

To study the effects of heavy ion irradiation at low temperature on type II superconductor Nb, the transition temperatureT _c , the normal state residual resistivityρ _B , the transition widthΔT _ph using oxygen ions of 25 MeV and subsequent thermal annealing were measured. The samples were held at temperatures <20 K during irradiation in a cryostat for in situ measurements. The maximum oxygen fluence was about 2·10¹⁵ cm^?2 corresponding a relatively high defect concentration. The heavy ion irradiation experiments are described. The critical temperatureT _c decreases with increasing residual resistivityρ _B . In agreement with the theory and experiments, the gap anisotropy parameter is 〈a ²〉=0.008, subsequent annealing shows a hysteresis ofT _c versusρ _B . The resistivity saturation value Δρ_BS = 2.55 μΩ cm was obtained and different recovery stages were found. Significant broadening of transition width during irradiation was observed.T _c andΔT _ph anneal to 60% in the temperature interval of (60–90) K. Oxygen induced effects as a simulation method of high neutron damage are compared with irradiation measurements using neutrons and deuterons.     

Photoluminescence of irradiation induced defects on CR-39

A gamma-irradiated poly allyl diglycol carbonate solid state nuclear track detector is studied by means of photoluminescence. The irradiation is done using a ⁶⁰Co cell with a dose rate of 7.5 kGy/h. Photoluminescent radiation is recorded with excitation radiation of wavelength 346 nm. A broad luminescent band shows a possible dosemetric property for γ-radiation in the dose range 0.1–8.0 MGy. High-dose irradiation by γ-rays introduces donor and acceptor levels in the forbidden energy gap. The broad band may be attributed to the number of overlapping emissions caused by transitions between these acceptor and donor levels.     

Precipitation of calcium carbonate by ultrasonic irradiation

Supersaturated solution of calcium carbonate ([Ca²⁺]=1.2 mmol/L, [HCO₃⁻]=3.2 mmol/L, pH=8.8, T=30±0.5 °C), a scale forming component, was irradiated by an ultrasonic homogenizer (24 kHz, 15–250 W/cm²) to study the factors that affect its precipitation rate. The factors of (1) depth of horn immersion, (2) ultrasonic intensity and horn tip size and (3) cavitation, which can affect the precipitation rate were investigated in this study. Ultrasonic irradiation was observed to accelerate the precipitation of calcium carbonate and it was found that there exists an optimum range of horn immersion depth for maximizing the precipitation rate. The experimental data also established that the precipitation rate was proportional to ultrasonic intensity and diameter of horn tip. These findings were correlated to the effects of physical mixing, that arises due to ultrasonic irradiation. However, the effect of cavitation in accelerating the precipitation rate was found to be small. Thus it is forwarded that the physical mixing effect, especially macrostreaming is the main factor that accelerates the precipitation rate of calcium carbonate during ultrasonic treatment. Further, neither the morphology nor the size of the calcium carbonate crystals formed were found to be affected by the ultrasonic irradiation.     

Effect of a displaced atom on a bulk surface topography induced by ion beam irradiation

The formation of a ripple topography on the surface of an amorphous solid at a small (subcritical) incidence angle of ions was studied by the statistical tests method. It was found that a pattern is formed if the sputtering of atoms in the uppermost layer of the target is taken into account along with the processes occurring in the bulk. In particular, the movement of the atoms displaced during the development of a cascade of impacts must be considered for the formation of a ripple topography with crests and valleys oriented along the beam projection onto the target surface.     

Effect of irradiation with intermediate-energy ions on structure and electrophysical properties of silicon dioxide films in a mos system

Conclusions In addition to the well-known advantages, ensuring intensive introduction of ion-beam doping in present-day semiconductor technology, this method allows the principal parameters of MOS systems to be controlled. Implantation is an effective method of low-temperature passivation of SiO₂-Si systems. The application of ion-beam doping for controlled charges in the parameters of MOS systems will make it possible to enhance the stability and quality of semiconductor devices and integrated circuits.The author wishes to express his gratitude to Professor P. T. Oreshkin for participating in the discussion of the work and for his useful remarks.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 34–39, December, 1978.     

Distribution of DNA fragment sizes after irradiation with ions

Ionizing radiation is responsible for production of double-strand breaks (DSBs) in a DNA structure. In contrast to sparsely ionizing radiation, densely ionizing radiation produces DSBs that are non-randomly distributed along the DNA molecule and can form clusters of various size. The paper discusses minimalistic models that describe observable patterns of fragment length in DNA segments irradiated with heavy ions and applies the formalism to interpret the recent experimental data collected by use of atomic force microscope (AFM).     

Electron-impact induced fragmentation of fullerene ions

The C2 fragmentation of fullerene ions C(q+)(60) (q = 1,2,3) induced by electron impact was studied for the first time. The cross sections for the loss of a C2 fragment indicate the presence of two different processes. At low electron energies the projectile electron leads to the direct excitation of the giant plasmon resonance. At electron energies larger than 100 eV the fragmentation of the fullerene ions can be described as an unsuccessful ionization. Only this second part of the cross section shows a dependence on the charge state q of the precursor ion.     

Effect of 100 MeV O7+ ions irradiation on ethanol sensing response of nanostructures of ZnO and SnO2

Tin dioxide nanoparticles and zinc oxide nanorods were synthesized chemically and thick film gas sensors on alumina substrates were fabricated of these materials. Morphology and crystallite size of synthesized powders were investigated by TEM. The fabricated sensors were irradiated with 100 MeV O⁷⁺ ions at fluences of 1×10¹¹, 1×10¹² and 1×10¹³ ions/cm². The X-ray diffraction analysis of the samples before and after ion bombardment was performed for structural characterization. The sensing response to ethanol before and after irradiation was carried out for each fabricated sensor. Investigation revealed that irradiated SnO₂ based sensor’s response and response time increased significantly. Results show that ZnO based sensor exhibit strong resistance to damage caused by ion irradiation which might be due to defects annihilation.     

Isotope effects induced by the action of ions on the surface of solids

We report on the results of study of isotope effects induced in solids by ion sputtering and ion implantation. The experiments are carried out using secondary ion mass spectrometry and secondary ion energy-mass spectrometry on molybdenum and copper-implanted nickel samples, as well as a number of titanium modifications. General regularities are revealed in the variation of the isotope composition in various processes. The mechanisms of isotope effects are discussed.     

Effect of electron irradiation on the oxidation of indium

The oxidation kinetics of indium is studied for two cases, namely, during continuous electron irradiation (E _p = 1800 eV) and without electron irradiation, as a function of the time of exposure to an oxygen medium at a partial oxygen pressure of 10⁻⁴ Pa and room temperature. The initial oxygen exposure was 50 L. The kinetic curves recorded upon continuous electron irradiation have two inflection points, and they can be attributed to the following three states of oxidation: physical adsorption, chemisorption with the formation of a nonstoichiometric oxide layer, and the growth of a homogeneous oxide layer. Only the first inflection point is observed during oxidation without electron irradiation, and further exposure does not lead to the second inflection point within the experimental time.     

Dependence of thermoluminescence response of calcium sulphate activated by dysprosium on the temperature irradiation

Radiation dosimetry is a very important issue in space research and in experiments that try to simulate chemical processes that may occur in cometary nucleus, interstellar grains, and other extraterrestrial environments, due to their irradiation by cosmic rays. The temperature effect is an important factor that has not been considered in many of these experiments. In this work, this effect was studied in TLD dosimeters exposed to gamma rays. The irradiations were done from 77 to 298 K in a Gamma cell unit with a dose rate of 1.0 Gy/s. Results obtained for CaSO₄:Dy show that there is a considerable effect in the evaluation of the dose as function of the irradiation temperature.     

Effects of O 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 × 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.