arXiv subjects

B. Kiss

Publications and source records attributed to B. Kiss.

5 recordsLinked to original sources

arXiv2022

Preliminary Thesis on the First and Second Part of the ALLEGRO CFD Benchmark Exercise

At BME (Budapest University of Technology and Economics) NTI (Institute of Nuclear Technics), a 7 pin rod bundle test section has been built in order to investigate the hydraulic behavior of the coolant in such design and to develop CFD models that could properly simulate the flow conditions in the ALLEGRO core. PIROUETTE (PIv ROd bUndlE Test faciliTy at bmE) is a test facility, which was designed to investigate the emerging flow conditions in various nuclear fuel assembly rod bundles. The measurement method is based on Particle Image Velocimetry (PIV) with Matching of Index of Refractory (MIR) method. In the test loop, it was necessary to install a flow straightener that was able to condition the velocity field before the rod bundle. The results of CFD simulations could be used to improve the understanding of the inlet conditions in the rod bundle test section.The second part of the benchmark deals with the 3D CFD modeling of the velocity field within the 7 pin rod bundle placed in the test section. The geometry of the test section will be given to the participants in an easy-to-use 3D format (.obj, .stp or .stl).

physics.flu-dyn↗

arXiv2022

Report on a pre-earthquake signal detection by enhanced E\"otv\"os torsion balance

More than 30 minutes before the earthquake event in Florina, Greece at 21:43:47(UTC) on 9th January 2022 an enhanced E\"otv\"os torsion balance registered unidentified signals in the J\'anossy Underground Research Laboratory in Budapest, Hungary. These signals were not visible on the seismograms, although seismic noises are continuously recorded by a side-by-side broadband seismometer. Moreover, seismological stations did not detect anything unusual, they presented a negative confirmation of the events. Our observation suggests that torsion balances might effectively detect precursory earthquake signals from a considerable distance. Such a finding could trigger the development of new observational devices and networks and can provide novel knowledge about the origin and mechanism of earthquake phenomena.

physics.geo-ph↗

arXiv2021

Single-shot electron imaging of dopant-induced nanoplasmas

We present single-shot electron velocity-map images of nanoplasmas generated from doped helium nanodroplets and neon clusters by intense near-infrared and mid-infrared laser pulses. We report a large variety of signal types, most crucially depending on the cluster size. The common feature is a two-component distribution for each single-cluster event: A bright inner part with nearly circular shape corresponding to electron energies up to a few eV, surrounded by an extended background of more energetic electrons. The total counts and energy of the electrons in the inner part are strongly correlated and follow a simple power-law dependence. Deviations from the circular shape of the inner electrons observed for neon clusters and large helium nanodroplets indicate non-spherical shapes of the neutral clusters. The dependence of the measured electron energies on the extraction voltage of the spectrometer indicates that the evolution of the nanoplasma is significantly affected by the presence of an external electric field. This conjecture is confirmed by molecular dynamics simulations, which reproduce the salient features of the experimental electron spectra.

physics.atm-clus↗

arXiv2021

High-order phase-dependent asymmetry in the above-threshold ionization plateau

Above-threshold ionization spectra from cesium are measured as a function of the carrier-envelope phase (CEP) using laser pulses centered at 3.1 $\mu$m wavelength. The directional asymmetry in the energy spectra of backscattered electrons oscillates three times, rather than once, as the CEP is changed from $0$ to $2\pi$. Using the improved strong-field approximation, we show that the unusual behavior arises from the interference of few quantum orbits. We discuss the conditions for observing the high-order CEP dependence, and draw an analogy with time-domain holography with electron wave packets.

physics.atom-ph↗

arXiv2018

Sub-cycle quantum electrodynamics in strongly laser-driven semiconductors

Electrodynamical processes induced in complex systems like semiconductors by strong electromagnetic fields, have traditionally/conventionally been described using semi-classical approaches. Although these approaches, allowed the investigation of ultrafast dynamics in solids culminating in multi-petahertz electronics, they do not provide any access in the quantum optical nature of the interaction as they treat the driving-field classically and unaffected by the interaction. Here, using a full quantum-optical approach, we demonstrate that the sub-cycle electronic response in a strongly driven semiconductor crystal is imprinted in the quantum-state of the driving-field resulting in non-classical light-states carrying the information of the interaction. This vital step towards strong-field ultrafast quantum electrodynamics unravels information inaccessible by conventional approaches and leads to the development of a new class non-classical light sources.

physics.optics↗