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Wyszukujesz frazę "positron beam" wg kryterium: Temat


Wyświetlanie 1-5 z 5
Tytuł:
Slow positron beam at the JINR, Dubna
Autorzy:
Horodek, P.
Kobets, A. G.
Meshkov, I. N.
Sidorin, A. A.
Orlov, O. S.
Powiązania:
https://bibliotekanauki.pl/articles/147134.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
positron beam
positron injector
Opis:
The Low Energy Positron Toroidal Accumulator (LEPTA) at the Joint Institute for Nuclear Research (JINR) proposed for generation of positronium in flight has been adopted for positron annihilation spectroscopy (PAS). The positron injector generates continuous slow positron beam with positron energy range between 50 eV and 35 keV. The radioactive 22Na isotope is used. In distinction to popular tungsten foil, here the solid neon is used as moderator. It allows to obtain the beam intensity of about 105 e+/s width energy spectrum characterized by full width at half maximum (FWHM) of 3.4 eV and a tail to lower energies of about 30 eV. The paper covers the characteristic of variable energy positron beam at the LEPTA facility: parameters, the rule of moderation, scheme of injector, and transportation of positrons into the sample chamber. Recent status of the project and its development in the field of PAS is discussed. As an example, the measurement of the positron diffusion length in pure iron is demonstrated.
Źródło:
Nukleonika; 2015, 60, No. 4, part 1; 725-728
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies of stainless steel exposed to sandblasting
Autorzy:
Horodek, P.
Eseev, M. K.
Kobets, A. G.
Powiązania:
https://bibliotekanauki.pl/articles/147075.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
stainless steel
sandblasting
defects
positron beam
Opis:
The influence of sandblasting on surface and subsurface of stainless steel is investigated using variable energy positron beam (VEP), positron annihilation spectroscopy (PAS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Samples of stainless steel were blasted using 110 μm particles of Al2O3 under different pressure and time duration. In the case of sandblasting for 90 s, the reduction of positron diffusion length depending on the applied pressure was observed. Sandblasting during 30 s leads only to the reduction of positron diffusion length to about 60 nm for all samples. Positron lifetimes close to 170 ps measured using positrons emitted directly from the source point to the presence of vacancies on the dislocation lines. SEM and AFM images show that surface roughness depends rather on pressure of sandblasting than time of exposition.
Źródło:
Nukleonika; 2015, 60, No. 4, part 1; 721-724
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Ultraviolet Absorber on Photo-Degradation of Epoxy Coating Studied by Slow Positron Beam
Autorzy:
Wang, Zheng
Liu, Fuwei
Li, Jingjing
He, Chunqing
Peng, Xiangyang
Huang, Zhen
Fang, Pengfei
Powiązania:
https://bibliotekanauki.pl/articles/1033239.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
epoxy coating
photo-degradation
ultraviolet absorber
slow positron beam
microstructure
Opis:
The photo-degradation progress of epoxy coating and the effect of ultraviolet absorber under UV-B irradiation have been investigated in slow positron beam and by the Fourier transform infrared spectrometer. After 120 h of irradiation, the value of S parameter in sample bulk is reduced while compared with the virgin sample. The result is mostly due to post-cure process happening in this initial irradiation stage. As the irradiation time increases to 360 h, the S parameter decreases sharply. This is due to the growth of carbonyl group and the generation of free radical. After 528 h or longer time of irradiation, a very low S value was obtained near sample surface, indicating the formation of a dead surface layer. Positron results also reveal that the addition of ultraviolet absorber suppresses the development of the dead layer after long-term UV-B irradiation. Ultraviolet absorber has a suppressing effect on generation of polar groups towards sample bulk. The addition of ultraviolet absorber is a key factor that affects the photo-degradation of epoxy coating.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1523-1526
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Estimate of the Crystallite Size for Nanocrystalline AISI 316L Stainless Steel and Armco Iron Processed by Hydrostatic Extrusion Using Variable Energy Positron Beam
Autorzy:
Sarnek, M.
Dryzek, E.
Horodek, P.
Pachla, W.
Powiązania:
https://bibliotekanauki.pl/articles/1033950.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
stainless steel
Armco iron
plastic deformation
hydrostatic extrusion
variable energy positron beam
X-ray diffraction
Opis:
The paper presents the results of research of nanocrystalline AISI 316L type stainless steel and nanocrystalline Armco pure iron processed by severe plastic deformation using hydrostatic extrusion method. Surface and subsurface of the steel samples extruded at different pressure were investigated using variable energy positron beam. It enabled us to determine the positron diffusion length and compare its values with those for annealed AISI 304 stainless steel. Furthermore positron lifetime and microhardness were measured for all the samples and X-ray diffraction was used to estimate the crystallite size.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1598-1601
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PF-6 an effective plasma focus as a source of ionizing radiation and plasma streams for application in material technology, biology and medicine
Autorzy:
Gribkov, V.
Dubrovsky, A.
Scholz, M.
Jednorog, S.
Karpiński, L.
Tomaszewski, K.
Paduch, M.
Miklaszewski, R.
Pimenov, V.
Ivanov, L. I.
Dyomina, E. V.
Maslyaev, S. A.
Orlova, M. A.
Powiązania:
https://bibliotekanauki.pl/articles/147424.pdf
Data publikacji:
2006
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
dense plasma focus (DPF)
ion beam
plasma beam
X-ray beams
surface damage
microlithography
radioenzymology
positron emission tomography (PET)
Opis:
A review of results on the design and operation of the new efficient Dense Plasma Focus device PF-6 of medium size (transportable) having bank energy of ca. 7 kJ and possessing a long lifetime is presented. New data on the interaction of the pulsed fast ion beams and dense plasma streams generated at this apparatus with various materials are given. These results are compared with the analogous information received at the biggest facility PF-1000. It is shown that it is possible to have about the same power flux density (in the range of 105 109 W/cm2) in both devices however in different areas. Doses of soft X-rays produced by the device within the resists for the goals of microlithography and micromachining appear to be several times less that it is with the conventional X-ray tube. In biological application of this device, medium- and hard-energy X-rays are exploited in the field of radioenzymology. It was found that the necessary dose producing activation/inactivation of enzymes can be by several orders of magnitude lower if used at a high-power flux density in comparison with those received with isotope sources. In medicine, short-life isotope production for the goals of the positron emission tomography (medicine diagnostics) is possible by means of the fast ions generated within DPF. All these experiments are discussed in the framework of pulsed radiation physics and chemistry in its perfect sense thereto the criteria are formulated.
Źródło:
Nukleonika; 2006, 51, 1; 55-62
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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