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Szeged, Hungary

Barna I.F.,Hungarian Academy of Sciences | Barna I.F.,ELI HU Nonprofit Kft. | Pocsai M.A.,Hungarian Academy of Sciences | Pocsai M.A.,University of Pecs | And 3 more authors.
Kerntechnik | Year: 2015

Steam condensation induced water hammer (CIWH) phenomena are investigated and new theoretical results are presented. We use the WAHA3 model based on two-phase flow six firstorder partial differential equations that present one dimensional, surface averaged mass, momentum and energy balances. A second order accurate high-resolution shock-capturing numerical scheme was applied with different kind of limiters in the numerical calculations. The applied two-fluid model shows some similarities to RELAP5 which is widely used in the nuclear industry to simulate nuclear power plant accidents. This model was validated with different CIWH experiments which were performed in the PMK-2 facility, which is a full-pressure thermohydraulic model of the nuclear power plant of VVER-440/312 type in the Energy Research Center of the Hungarian Academy of Sciences and in the Rosa facility of the Japan Atomic Energy Agency. In our present study we show the first part of a planned large database which will give us the upper and lower flooding mass flow rates for various pipe geometries where CIWH can happen. Such a reliable database would be a great help for future reactor constructions and scheming. © Carl Hanser Verlag GmbH & Co. KG. Source

Chen S.N.,CEA Saclay Nuclear Research Center | Chen S.N.,Institute of Applied Physics | Gauthier M.,SLAC | Bazalova-Carter M.,University of Victoria | And 12 more authors.
Review of Scientific Instruments | Year: 2016

Radiochromic films (RCF) are commonly used in dosimetry for a wide range of radiation sources (electrons, protons, and photons) for medical, industrial, and scientific applications. They are multi-layered, which includes plastic substrate layers and sensitive layers that incorporate a radiation-sensitive dye. Quantitative dose can be retrieved by digitizing the film, provided that a prior calibration exists. Here, to calibrate the newly developed EBT3 and HDv2 RCFs from Gafchromic™, we used the Stanford Medical LINAC to deposit in the films various doses of 10 MeV photons, and by scanning the films using three independent EPSON Precision 2450 scanners, three independent EPSON V750 scanners, and two independent EPSON 11000XL scanners. The films were scanned in separate RGB channels, as well as in black and white, and film orientation was varied. We found that the green channel of the RGB scan and the grayscale channel are in fact quite consistent over the different models of the scanner, although this comes at the cost of a reduction in sensitivity (by a factor ∼2.5 compared to the red channel). To allow any user to extend the absolute calibration reported here to any other scanner, we furthermore provide a calibration curve of the EPSON 2450 scanner based on absolutely calibrated, commercially available, optical density filters. © 2016 Author(s). Source

Barna I.F.,Hungarian Academy of Sciences | Varro S.,ELI HU Nonprofit Kft.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2016

We present the general theory for proton nuclei scattering in a bichromatic laser field. As a physical example we consider proton collision on 12C at 49 MeV/amu moderate energies in the field of a titan sapphire laser with its second harmonic. © 2015 Elsevier B.V. All rights reserved. Source

Kroo N.,Hungarian Academy of Sciences | Racz P.,Hungarian Academy of Sciences | Varro S.,Hungarian Academy of Sciences | Varro S.,ELI HU Nonprofit Kft.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2016

Surface plasmons (SPOs) have been excited by intense femtosecond laser pulses on a gold film at room temperature and their near field has been analyzed by the intensity dependent response of an STM and by studying the spectra of multiplasmon emitted electrons. Around 80 GW/cm2 laser intensity, anomalies have been found in both cases, interpreted as the stepping in of electron pairing, transition to a diamagnetic state, and by anomalous Faraday rotation. © 2015 Elsevier B.V. All rights reserved. Source

Barna I.F.,Hungarian Academy of Sciences | Barna I.F.,ELI HU Nonprofit Kft.
Laser Physics | Year: 2014

In our study we consider nonlinear, power-law field-dependent electrical permittivity and magnetic permeability and investigate the time-dependent Maxwell equations with self-similar ansatz. This is a first-order hyperbolic partial differential equation system which can conserve non-continuous initial conditions describing electromagnetic shock. Such phenomena may happen in complex materials induced by the planned powerful Extreme Light Infrastructure laser pulses. © 2014 IOP Publishing Ltd. Source

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