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Spectator invariance test in the study of the Li-6,Li-7 fusion reactions via the Trojan Horse Method
Pizzone, R. G.; Lamia, L.; Bertulani, C. A.; Mukhamedzhanov, A.; Spitaleri, C.; Blokhinstev, L.; Burjan, Václav; Cherubini, S.; Hons, Zdeněk; Kiss, G. G.; Kroha, Václav; La Cognata, M.; Li, C.; Mrázek, Jaromír; Piskoř, Štěpán; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tumino, A.
2011 - English
Fusion reactions play a crucial role for several astrophysical scenarios. At the low energies typical of such environments direct measurements of reaction cross sections are very difficult, and even sometimes impossible. In such cases the use of indirect methods can give a substantial help. The Trojan Horse Method (THM) is based on the quasi-free break-up of a nucleus, which can be described in terms of a cluster structure. In such applications the independence of THM results with different break-up schemes, was tested using the quasi free(3)He(Li-6,alpha alpha)H and He-3(Li-7,alpha alpha)H-2 reactions. Results were then compared with the direct behaviours obtained from available data as well as with the cross sections extracted from previous indirect investigations of the same binary reactions using a different nuclide as a Trojan Horse nucleus.
Keywords:
fusion reactions; indirect methods; cross section
Available at various institutes of the ASCR
Spectator invariance test in the study of the Li-6,Li-7 fusion reactions via the Trojan Horse Method
Fusion reactions play a crucial role for several astrophysical scenarios. At the low energies typical of such environments direct measurements of reaction cross sections are very difficult, and even ...
Characterization of the Nanostructured Nickel Oxide Layers Prepared by Ion Beam Sputtering
Horák, Pavel; Bejšovec, Václav; Lavrentiev, Vasyl; Khun, J.; Vrňata, M.
2011 - English
Nanostructured nickel oxide layers (thickness cca 100 nm) were prepared by bombardment of nickel foil with ion beam created from a mixture of argon and oxygen. Different volume ratios of argon:oxygen mixture were used, ranging from 4:1 to 1:3. Composition of the resulting layers was analyzed by RBS, morphology by AFM and main crystal orientation of the sample by XRD. The electrophysical properties (resistivity, concentration of charge carriers) were measured by four point Van der Pauw technique and Hall measurement respectively. Prepared samples were characterized in as-deposited state and after annealing with varying temperature of treatment. Chemical composition (i.e. stoichiometry) of the as-deposited samples with different argon: oxygen ratio was related to their electrophysical parameters. Hall measurements are showing majority charge carriers to be electrons - surface concentration (0.5 - 2.3) x 10(21) m(-2) - suggesting prevailing metallic conductivity. Resistivity of the sample is increasing with higher amount of oxygen in gas mixture. The as-deposited layer is almost amorphous with no visible grains on AFM.
Keywords:
Nickel oxide; Ion Beam Sputtering; Van der Pauw
Fulltext is available at external website.
Characterization of the Nanostructured Nickel Oxide Layers Prepared by Ion Beam Sputtering
Nanostructured nickel oxide layers (thickness cca 100 nm) were prepared by bombardment of nickel foil with ion beam created from a mixture of argon and oxygen. Different volume ratios of argon:oxygen ...
High accuracy O-18(p, alpha)N-15 reaction rate in the 8 . 10(6)-5 . 10(9) K temperature range
La Cognata, M.; Spitaleri, C.; Mukhamedzhanov, A.; Banu, A.; Cherubini, S.; Coc, A.; Crucilla, V.; Goldberg, V.; Gulino, M.; Irgaziev, B.; Kiss, G. G.; Lamia, L.; Mrázek, Jaromír; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tabacaru, G.; Trache, L.; Tribble, R. E.; Trzaska, W.; Tumino, A.
2011 - English
The O-18(p, alpha)N-15 reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as F-19, O-18 and N-15. In this work, a high accuracy O-18(p, alpha) N-15 reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2(+) resonance. Since Gamma similar to 100 - 300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T similar to 0.510(9) K based over our new improved determination of its resonance parameters.
Keywords:
nuclear reactions; nycleosynthesis; abundances
Available at various institutes of the ASCR
High accuracy O-18(p, alpha)N-15 reaction rate in the 8 . 10(6)-5 . 10(9) K temperature range
The O-18(p, alpha)N-15 reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as F-19, O-18 and N-15. In this work, a high accuracy ...
Vertex Couplings in quantum Graphs: Approximations by Scaled Schrödinger Operators
Exner, Pavel
2011 - English
We review recent progress in understanding the physical meaning of quantum graph models through analysis of their vertex coupling approximations.
Keywords:
quantum graphs; vertex coupling; tube networks
Available at various institutes of the ASCR
Vertex Couplings in quantum Graphs: Approximations by Scaled Schrödinger Operators
We review recent progress in understanding the physical meaning of quantum graph models through analysis of their vertex coupling approximations.
Výpočet dynamiky chování microtronu MT 25 a jeho rychlá simulace
Krist, Pavel; Bíla, J.; Chvátil, David
2011 - Czech
Článek se zabývá návrhem matematického modelu, který je vyvíjen z důvodu nastavení a testování fuzzy řídicího systému mikrotronu MT 25. Mikrotron MT 25 je cyklický urychlovač elektronů. Tento typ urychlovače je doposud řízen pouze manuálně operátorem. Matematický model je založen na výpočtu pohybu elektronů v urychlovací dutině a ve vakuové komoře urychlovače. Simulace urychlovače je pak provedena v prostředí Matlab – Simulink. This paper presents the design of a mathematical model and its fast simulation developed for the setup of the control system of the MT 25 microtron, which is a cyclic electron accelerator. This type of accelerator has been controlled manually until now. The mathematical model is based on calculations of the electron motion in the accelerating cavity and vacuum chamber. The simulation diagram was created in Matlab – Simulink.
Keywords:
Microtron; electron accelerator; electron source; LaB6; beam simulation
Available at various institutes of the ASCR
Výpočet dynamiky chování microtronu MT 25 a jeho rychlá simulace
Článek se zabývá návrhem matematického modelu, který je vyvíjen z důvodu nastavení a testování fuzzy řídicího systému mikrotronu MT 25. Mikrotron MT 25 je cyklický urychlovač elektronů. Tento typ ...
Using constraint programming in anytime path planner
Zerola, Michal
2011 - English
Path planning in one of the critical tasks for autonomous robots. We will study the problem of finding the shortest path for a robot collecting waste spread over the area such that thet robot has a limited capacity and hence during the route it must periodically visit depost/collectors to empty the collected waste.
Keywords:
Logistika; Autonomní roboti
Available at various institutes of the ASCR
Using constraint programming in anytime path planner
Path planning in one of the critical tasks for autonomous robots. We will study the problem of finding the shortest path for a robot collecting waste spread over the area such that thet robot has a ...
K problematice řízení klasického typu mikrotronu a využití fuzzy logiky
Krist, Pavel; Bíla, J.
2011 - Czech
Práce se zabývá problematikou řízení klasického typu mikrotronu s Kapitzovým urychlovacím rezonátorem. Zde je využito fuzzy regulátoru. Hlavním problémem, který vede k použití takovéhoto regulátoru, je problematické měření velikosti urychlovacího napětí. Toto napětí musí být nastaveno velmi pečlivě, jinak nedojde ke splnění urychlovacích podmínek. This work deals with control problems of the classical microtron with Kapitza type of the accelerating cavity. Fuzzy controller is used. The main problem, which led to use this type of controller, is a problematical measurement of the radio-frequency electric field inside accelerating cavity. Careful setting of this electric field is necessary for accelerating condition fulfillment.
Keywords:
Microtron; Electron accelerator; Accelerator controller; Fuzzy logic
Available at various institutes of the ASCR
K problematice řízení klasického typu mikrotronu a využití fuzzy logiky
Práce se zabývá problematikou řízení klasického typu mikrotronu s Kapitzovým urychlovacím rezonátorem. Zde je využito fuzzy regulátoru. Hlavním problémem, který vede k použití takovéhoto regulátoru, ...
Charakteristika neutronových toků na mikrotronu MT25
Chvátil, David; Králik, M.; Granja, C.; Krist, Pavel
2011 - Czech
Mikrotron je malý cyklický urychlovač elektronů. Jestliže má být využit jako zdroj neutronů, urychlené elektrony musí být konvergovány na neutrony pomocí jaderných reakcí. K měření spekter neutronů produkovaných vysokoenergetickým gama zářením v olověném a uranovém terči byla použita sada Bonnerových koulí vybavených pasivními detektory termálních neutronů. Výtěžek neutronů z uranového terče je přibližně dvakrát vyšší než z terče olověného. Microtron is a small cyclic electron accelerator. When it is used as a source of neutrons, electrons must be converted to neutrons by means of nuclear reactions. Spectra of neutrons produced by high energy X-ray photons in lead and uranium targets installed on the microtron MT25 were measured by the Bonner sphere spectrometer with passive detectors of thermal neutrons. Neutron yield from uranium target was nearly two times higher than from the lead one.
Keywords:
Microtron; electron accelerator; neutron source; U target; Pb target; Bonner sphere; NAA; Mn foil
Available at various institutes of the ASCR
Charakteristika neutronových toků na mikrotronu MT25
Mikrotron je malý cyklický urychlovač elektronů. Jestliže má být využit jako zdroj neutronů, urychlené elektrony musí být konvergovány na neutrony pomocí jaderných reakcí. K měření spekter neutronů ...
Emergent Phenomena, Morphomatics and Theory of Complexity
Bíla, J.; Krist, Pavel
2011 - English
This paper is devoted to knowledge and symbolical environments for grasping of emergent phenomena. Respecting the fact that the origin of shapes of nature has its essence in emergencies the paper turns attention to formalisms for direct work with such “shapes” (Morphomatics). There are described three environments for grasping of emergent phenomena especially environment 2 as a cognitive tool and environment 3 as dynamic relation between Macrostructure and Microstructure emphasizing their mutual interactions. As an example of formalism developed from synthesis of the introduced three environments is illustrated the use of theory of matroids (dual of Fano matroid) for case of supergravity D=11.
Keywords:
emergent phenomena; sign model; semantic space; macrostructure; microstructure; matroids
Available at various institutes of the ASCR
Emergent Phenomena, Morphomatics and Theory of Complexity
This paper is devoted to knowledge and symbolical environments for grasping of emergent phenomena. Respecting the fact that the origin of shapes of nature has its essence in emergencies the paper ...
Neutron diffraction analysis of residual strain/stress distribution in the vicinity of high strength welds
Mráz, Ľ.; Karlsson, L.; Hamak, I.; Vrána, Miroslav; Mikula, Pavol
2010 - English
Residual stresses resulting from non homogeneous heat distribution during welding process belong to most significant factor influencing behavior of welded structures. These stresses are responsible for defect occurrence during welding and they are also responsible for crack initiation and propagation at the either static or dynamic load. The significant effect of weld metal chemical composition as well as the effect of fatigue load and local plastic deformation on residual stress distribution and fatigue life have been recognized for high strength steels welds. The changes in residual stress distribution have then positive effect on cold cracking behavior and also on fatigue properties of the welds [1-3]. Several experimental methods, both destructive and non-destructive, such as hole drilling method, X-ray diffraction, neutron diffraction and others, have been used to examine residual stress distribution in all three significant orientations in the vicinity of the welds. The present contribution summarizes the results of neutron diffraction measurements of residual stress distribution in the vicinity of single-pass high-strength-steel welds having different chemical composition as well as the influence of fatigue load and local plastic deformation. It has been observed that the chemical composition of the weld metal has a significant influence on the stress distribution around the weld. Similarly, by aplying both cyclic load or pre-stress load on the specimens, stress relaxation was observed even in the region of approximately 40 mm far from the weld toe.
Keywords:
residual stress; neutron diffraction
Available at various institutes of the ASCR
Neutron diffraction analysis of residual strain/stress distribution in the vicinity of high strength welds
Residual stresses resulting from non homogeneous heat distribution during welding process belong to most significant factor influencing behavior of welded structures. These stresses are responsible ...
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