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1
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Special Structures of Graphite Steels After High-Energy Electron Irradiation

100%
Alexandrova N.
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vol. 96
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issue 2
259-262
EN
The effect of high-energy electron irradiation on the structure and properties of the graphite steels have been investigated. It has been shown that single- and multicycle irradiation allows the improvement of hardness and ductility (≈ twice). A partial dissolution of the graphite, carbides redistribution, and refinement of the grain size allow the formation of the favorable surface structure after irradiation.
2
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Current-Voltage Characteristic Features of Diodes Irradiated with 170~MeV Xenon Ions

100%
Poklonski N., Gorbachuk N., Nha V., Tarasik M., Shpakovski S., Filipenia V., Skuratov V., Wieck A., Kołtunowicz T.
Acta Physica Polonica A
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2013
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vol. 123
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issue 5
926-928
EN
Diodes manufactured on the wafers of single-crystalline silicon uniformly doped with phosphorus are studied. The wafer resistivity was 90 Ω cm. Xenon ions were implanted into the diodes from the side of the p^{+}-region (implantation energy 170 MeV, fluence Φp from 5 × 10^7 to 10^9 cm^{-2}). It is shown that the formation of a continuous irradiation damaged layer with the thickness of the order of magnitude of the average projective range creates prerequisites for the negative differential resistance in the current-voltage characteristics of the irradiated diodes.
3
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Effects of Fluences of Irradiation with 107 MeV Krypton Ions on the Recovery Charge of Silicon p^{+}n-Diodes

100%
Poklonski N., Gorbachuk N., Tarasik M., Shpakovski S., Filipenia V., Skuratov V., Wieck A., Kołtunowicz T.
Acta Physica Polonica A
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2011
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vol. 120
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issue 1
111-114
EN
The diodes manufactured on the wafers of single-crystalline silicon uniformly doped with phosphorus are studied. The wafer resistivity was 90 Ω cm. Krypton ions are implanted to the side of the p^{+}-region of diodes (energy 107 MeV, fluence Φp from 5 × 10^7 to 4 × 10^9 cm^{-2}). It is shown that recovery charge Q_{rr} is inversely proportional to the square root of the irradiation fluence value Φp. When the fluence increases, the part of the recovery charge Q_{rrA}, due to the high reverse conductance phase, decreases faster than the value Q_{rr}.
4
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Influence of Defects Introduced by Irradiation with 4-9 MeV Helium Ions on Impedance of Silicon Diodes

100%
Poklonski N., Gorbachuk N., Nha V., Shpakovski S., Filipenya V., Skuratov V., Kołtunowicz T., Kukharchyk N., Becker H., Wieck A.
Acta Physica Polonica A
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2015
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vol. 128
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issue 5
891-893
EN
Silicon diodes irradiated with helium ions with energies of 4.1, 6.8 and 8.9 MeV are studied. It is shown that the mechanism determining the behaviour of frequency dependence of complex electric module and correspondingly the behavior of impedance of diodes irradiated with helium ions in the frequency region 3-200 kHz is a recharging of vacancy complexes localized in the space charge region.
5
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Ortho-Positronium in Alkanes under High Pressure

80%
Goworek T., Zgardzińska B.
Acta Physica Polonica A
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2008
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vol. 113
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issue 5
1379-1383
EN
Phase transitions in n-alkanes were observed by using the positron annihilation lifetime method. In the case of alkanes, application of pressure is equivalent to temperature lowering (1 K corresponds to ≈4 MPa). When argon at high pressure penetrates the sample one observes a non-monotonous dependence of the melting point on pressure. This effect is observed also in even-numbered alkanes, in which there is no rotator phase.
6
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Defect Recovery in α-Fe e^{-}-irradiated at 300 K

80%
Dai G., Li X., Moser P., Moya G., Van Duysen J.
Acta Physica Polonica A
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1993
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vol. 83
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issue 3
277-286
EN
Defect annealing recovery has been studied, by measuring positron lifetime spectra, in high-purity α-iron irradiated at 300 K with 3 MeV electrons to a fluency of 7 × 10^{19} cm^{-2}. Vacancy clusters containing 6-10 single vacancies were observed immediately after irradiation during which they were possibly forming (the so-called "irradiation annealing"). With increasing temperature, the agglomerates continually grow in size at the expense of their concentration, giving rise to the formation of microvoids (> 15 vacancies). Also present were other types of defects, probably immobile vacancies trapped by impurity (e.g. carbon) atoms and dislocation/loops generated presumably from collapse of voids during the relatively high dose irradiation and/or the annealing. The immobile vacancies eventually became movable at around 350 K, supplying the growing clusters and thus leading to a stabilization in their concentration till around 500 K. Between 500 and 700 K, microvoids gradually evaporated, but the dislocation-associated defects were able to survive annealing at temperatures as high as 700 K. The void size and concentration and their evolution have been evaluated on the basis of both the to date theoretical and experimental studies. The temperature dependence was also, observed of positron trapping into vacancy agglomerates of various sizes.
7
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Positronium in Phase IV and Rotator Phase of Long-Chain Alkanes

80%
Zgardzińska B., Goworek T.
Acta Physica Polonica A
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2008
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vol. 113
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issue 5
1551-1555
EN
Ortho-positronium lifetime and intensity was measured as a function of temperature and pressure for some n-alkanes in which so-called "phase IV" appears. This phase is characterized by slightly increased ortho-positronium lifetime compared to low-temperature phases. It was found that the effect of quenching positronium by light does not appear in all phases from phase IV upwards. The lifetime in the rotator phases becomes equal to that in liquids, and only the change of positronium formation intensity allows to detect the solid-liquid transition in positron lifetime measurements.
8
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Content available

Primary Chemical Reactions Induced by Transformation of Radioactive Nuclei in Solids at Low Temperatures. Investigation by Means of the Emission Mössbauer and Positron Spectroscopies

80%
Byakov V., Kulikov L., Perfil'ev Y., Stepanov S.
Acta Physica Polonica A
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2005
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vol. 107
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issue 5
792-798
EN
A set of early chemical reactions in grapes of ionization (blobs) arising in tracks of fast electrons and positrons in liquids as well as formed by the Auger electrons in frozen aqueous media around decaying Mössbauer ^{57}Co or ^{119m}Sn nuclei is suggested. The mechanism predicts a correlated variation of the formation probabilities of intrablob final products, namely Fe^{2+}-Fe^{3+} or Sn^{2+}-Sn^{4+} ions, positronium atom and molecular hydrogen with variation of temperature, degree of crystallinity, concentration of electron scavengers. These correlations indicate on similarity of chemical processes as in blobs created by ^{57}Co and ^{119m}Sn after their decay as well as in blobs produced in tracks of fast positrons and electrons.
9
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Magnetic Properties of Biocompatible Magnetic Fluid after Electron Irradiation

80%
Tomašovičová N., Haysak I., Koneracká M., Kováč J., Timko M., Závišová V., Okunev A., Parlag A., Fradkin A., Sakhno V., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1302-1304
EN
The magnetic particles in the water-based magnetic fluids were sterically stabilized by natrium oleate to prevent their agglomeration and consequently the adsorption of poly-ethylene-glycol (PEG) was carried out to improve the biocompatibility of the magnetic particles. Two sets of samples were prepared. The first set of the samples was with different molar weight of PEG (Mw = 400, 1000, 10000 and 20000) at the constant weight ratio of PEG/Fe_3O_4 = 0.25 and the second one was with different weight ratio of PEG/Fe_3O_4 and constant molar weight of PEG (Mw = 1000). The samples were irradiated with 20 Gy. The same reduction of saturated magnetization (about 10%) after electron irradiation with 20 Gy was observed for all prepared samples.
10
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Doppler Broadening and Positron Lifetime Measurements of Well-Characterized Sandstone and Limestone Rocks

80%
Urban J. M., Quarles C. A., Salaita G. N.
Acta Physica Polonica A
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1995
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vol. 88
|
issue 1
241-248
EN
We measured the S parameter for samples of well-characterized rocks. Some samples were cleaned while others contained natural hydrocarbons. We also saturated some samples with oil. Preliminary results show a difference in the S parameter for sandstone and limestone samples. There is also a significant difference between samples when clean and when containing natural hydrocarbons or when saturated with light oil. We also measured the lifetime spectrum for the same samples in dry, fresh water-saturated, and brine-saturated condition. The observed lifetime spectra could be described with two or three components. While a detailed understanding of the physical processes responsible for the lifetime spectra is still under study, several interesting results have been obtained. The average lifetime is correlated with the S parameter. The porosity of the samples is correlated with the intensity of the third lifetime component. The average lifetime, as well as the second lifetime component, is systematically longer in the sandstone than limestone samples, and in water or brine-saturated samples. The intensity of the third lifetime component is generally larger in the water or brine-saturated samples.
11
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XRD Analysis of Synthetic Diamond Powders Irradiated with Electrons

80%
Shishonok E., Luhin V., Koltunowicz T.
Acta Physica Polonica A
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2015
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vol. 128
|
issue 5
912-914
EN
Powders of synthetic diamond with low strength were sorted on sets with a different grain size. The synthetic diamond sets had various crushing strengths and morphology. They were irradiated with high energy electrons (6.5 MeV, D=2×10¹⁹ cm¯²) and analyzed using X-ray diffraction (Cu K_α) before and after irradiation. As established from nonlinearity of the a(Θ)=f{R(Θ)} dependences and observed extra splittings in X-ray diffraction patterns (in addition to α₁-α₂ doublets), crystal lattice of synthetic diamond from different sets was variously distorted. Irradiation led to decreasing distortions more significantly, the higher the initial strength of the set was. The made conclusions coincide well with our previous results on synthetic diamond powders which were irradiated under various softer conditions with direct measurements of synthetic diamond crushing strength without X-ray diffraction analysis. X-ray diffraction allows to presort synthetic diamond of critically low relative mechanical strength as well as evaluate resistance of diamond crystal lattice against heavy irradiation and other external impacts.
12
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Temperature Dependent Variations of Properties of Polymer-Like Carbon Coatings Treated with High Energy Electrons

80%
Plaipaitė-Nalivaiko R., Vigricaitė L., Adlienė D., Rutkūnienė Ž.
Acta Physica Polonica A
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2015
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vol. 128
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issue 5
915-917
EN
Polymer-like carbon coatings can be used for the protection of micro-electromechanical devices functioning in chemically or radiation harsh environment due to their beneficial properties. Properties of carbon coatings depend on the method of synthesis, initial gas mixture, admixture of additives, temperature and other technological parameters. Modification of carbon structures is possible applying high energy electrons. Coating mechanical properties become almost stable after their pretreatment with some doses of high energy electrons. Polymer-like carbon coatings were synthesized from acetylene gas plasma on n-type silicon substrates in the RF plasmotron system at temperatures in the range 293-673 K using plasma enhanced chemical vapor deposition method. Series of samples were prepared and irradiated with high energy (6 MeV) electrons in a medical linear accelerator. The ellipsometric method was used for estimation of some optical parameters and thickness of synthesized coatings. Structural changes of polymer-like carbon coatings were evaluated using the Raman spectroscopy and surface morphology was assessed by atomic force microscopy. Electron beam induced structural changes in the coatings were analyzed using the obtained results. The relations between the synthesis temperature and samples structure and surface morphology are discussed.
13
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Relationship between Enhanced Positronium Formation and Enhanced Positron Trapping in Polymers at Low Temperature

80%
Kansy J., Suzuki T.
Acta Physica Polonica A
|
2006
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vol. 110
|
issue 5
593-604
EN
Positron annihilation lifetime spectroscopy is used for investigation of low-density polyethylene and ethylene-methyl methacrylate copolymers of 1.45, 3.0, and 5.4 mole% of methyl methacrylate. The lifetime spectra are collected at 30 K, one by one, as a function of elapsed time. In the computer analysis a new theoretical model is developed, which enables separating the annihilation from positron free state, its trapped state and bound state in positronium. The positron trapping rateμ and the enhanced positronium formation rateκ are determined. The calculated values of μ andκ turned out to be linearly correlated. This correlation presumably originates from an influence of trapped electrons on the trapping of positrons. The dependences ofκ on measurement time are determined for low-density polyethylene and ethylene-methyl methacrylate of different methyl methacrylate content. A theoretical model describing quantitatively the dependences is proposed. The model considers the processes of electron-ion recombination, electron trapping, and electron scavenging by dipolar carbonyl groups supplied by methyl methacrylate additives.
14
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Content available

Experimental Verification of the Blob Model and Delayed Formation of Ps

80%
Dauwe C., Van Waeyenberge B., De Baerdemaeker J.
Acta Physica Polonica A
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2005
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vol. 107
|
issue 4
623-628
EN
Stepanov and Byakov's blob model for the formation of positronium can be considered as an extension of the spur model. However, it offers many extra possibilities and is more sound from the radiation chemistry point of view. A full coding of this model leads to non-exponential lifetime spectra, and standard multi-component analysis is no longer adequate for materials such as polymers. Age momentum correlation experiments were performed on linear PMMA at different temperatures and were analyzed with the non-exponential blob model. We show the adequacy of this model, and moreover an alternative explanation for the young-age broadening and delayed formation of positronium.
15
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Content available

Influence of Positron Irradiation on Positronium Formation in n-Alkanes

80%
Pietrow M., Zgardzińska B.
Acta Physica Polonica A
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2006
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vol. 110
|
issue 5
641-648
EN
Positronium formation probability was investigated as a function of irradiation time and temperature for some long-chain saturated hydrocarbons (alkanes). Intensity of ortho-positronium component in the lifetime spectrum depends on the concentration of trapped excess electrons, but also on concentration of radicals and ions acting as electron scavengers. The results indicate the existence of two kinds of electron traps; those which are not emptied by thermal treatment disappear after several days of positron irradiation.
16
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Role of Trapped and Solvated Electrons in Ps Formation

80%
Stepanov S., Byakov V., He C., Hirade T., Mikhin K.
Acta Physica Polonica A
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2005
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vol. 107
|
issue 4
642-650
EN
Role of trapped and solvated electrons in Ps formation is discussed. Combination of thermalized positron with such electrons is possible from the viewpoint of the energy balance and may results in Ps formation. This process proceeds during all e^+ lifetime in matter. Fitting of raw experimental e^+ - e^- annihilation spectra has to be based on an adequate physical input, which often leads to necessity of nonexponential deconvolution of the spectra. We have interpreted the Ps formation data in polyethylene, ethylene-methylmethacrylate and polymethylmethacrylate in dark and in light vs. time of the measurement and temperature. Parameters characterized accumulation of trapped electrons and their recombination with counter ions and positrons are obtained.
17
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Application of Electron Beam Radiation to Modify Crosslink Structure in Rubber Vulcanizates and Its Tribological Consequences

80%
Stępkowska A., Bieliński D., Przybytniak G.
Acta Physica Polonica A
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2011
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vol. 120
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issue 1
53-55
EN
The aim of this work was the modification of crosslink density and structure of rubber vulcanizates in order to control surface energy, mechanical strength under static as well as dynamic conditions and in consequence, tribological properties of the materials. Sulphur vulcanizates of styrene-butadiene rubber, filled with carbon black, were subjected to electron beam radiation in the range from 150 to 200 kGy. Changes in crosslink density and structure were determined applying the method of selective swelling of rubber in "hard" and "soft" solvents. The modification influences the ability of material of energy dissipation and its surface wettability. The changes are discussed from the friction and abrasion of rubber point of view.
18
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Revision of the Model of Formation of Radiolytic Products in Aqueous Solutions

80%
Stepanov S., Byakov V.
Acta Physica Polonica A
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2005
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vol. 107
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issue 4
651-660
EN
Mathematical model of formation of radiolytic products (e^-_{aq}, H, OH, H_2, H_3O^+, OH^-, Ps) in water is developed. It takes into account (1) reactions between dissolved scavengers of thermalized and hydrated electrons as well as epithermal ones; (2) ambipolar diffusion expansion of the intratrack species; (3) additional channels of Ps and H_2 formation due to appearance of weakly trapped electrons. Good agreement is obtained with experimental data on kinetics of accumulation of the products in pure water and their concentration variations in aqueous solutions.
19
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Investigation of Sulphur Nanoclusters in Ageing Ni-S System after Irradiation and Thermal Treatment by Positron Annihilation

80%
Perminov D., Druzhkov A., Arbuzov V., Danilov S.
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vol. 125
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issue 3
729-732
EN
The pure Ni and Ni-S ageing systems, thermally aged and also irradiated by 5 MeV electrons at 270 K with subsequent annealing, are studied by means of positron annihilation spectroscopy. The formation of ultrafine S-rich precipitates (clusters) is observed in Ni-S during thermal ageing at about 650 K. It is assumed that these clusters do not contain vacancy-type defects and they are coherent to the Ni matrix. The positrons localize in sulphur clusters that is due to affinity-induced confinement. In irradiated Ni-S system, the mobile vacancy-S atom complexes are formed at post-irradiation annealing above 350 K (stage III). These complexes form the three-dimensional vacancy clusters (nanovoids) decorated with S atoms. The radiation induced nucleation of S-rich clusters occurs when nanovoids dissociate.
20
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Ortho-Positronium in Some n-Alkanes; Influence of Temperature and Pressure

80%
Zgardzińska B., Pietrow M., Goworek T., Wawryszczuk J.
Acta Physica Polonica A
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2006
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vol. 110
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issue 5
747-753
EN
Positron lifetime spectra were measured for a series of odd-numbered n-alkanes from C_{11}H_{24} to C_{19}H_{40} as a function of temperature and pressure. The ortho-Ps lifetimes in the rotator phase and the increase in intensity at the transition to that phase can be explained by location of Ps in the vicinity of kink-type conformers. The relation between o-Ps lifetime and molecule length can be described in the framework of extended Tao-Eldrup model. One can eliminate the effect of intensity rise in time by sample illumination or by application of high pressure. A decrease in temperature by 1 K is equivalent to an increase in pressure by about 4 MPa.
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