Anna Horváth, Balázs Bámer, Gergely Gábor Barnaföldi and Dávid Légrády (2022.01.01 - 2022.07.30)
Wigner Research Centre for Physics

Abstract: We investigate the optical trajectories in non-linear optical medium applying standard description. We apply modern machine learning techniques for the image reconstruction.

Mihály András Pocsai, Imre Ferenc Barna, Gábor Bíró, Gergely Gábor Barnaföldi (2021.10.01 - 2022.01.31)
Wigner Research Centre for Physics

Abstract: In the concept of plasma based particle acceleration, the particles are accelerated in the wakefield generated by a driver pulse, which may be either a beam of charged particles or a short, intense laser pulse, instead of guiding,collimating and them in vacuum with strong electromagnetic fields [1]. The witness bunch is usually injected in the plasma from an external source, but in case of electron acceleration using a laser pulse as a driver pulse, at sufficiently high laser intensities, some of the plasma electrons are being trapped in the wakefield generated by the laser pulse. This phenomenon is referred as self-injection. In the schemes mentioned above, the driver bunches transfer their energy to the witness bunches through the pla...


Forgács-Dajka Emese, Kővári Emese, Kovács Tamás (2022.01.01 - 2022.03.30)
Eötvös Loránd University, Center for Astrophysics and Space Science

Abstract: Mean motion resonances (MMRs) play an important role in shaping the dynamics of the Solar system bodies. MMRs in the Solar system usually occur between a planet and small bodies, e.g. the members of the Hilda group of asteroids are in a 3:2, while the Trojan asteroids are in a 1:1 MMR with Jupiter. Based on the geometrical meaning of the resonance variable, an efficient method has been introduced and described in Forgács-Dajka, Sándor & Érdi (2018), by which mean motion resonances can be easily found without any a priori knowledge of them. The efficiency of this method - named FAIR - is clearly demonstrated by using some known members of different families of asteroids being in mean motion resonances with a planet. The region beyond Neptune contains a significant number of asteroids (TNOs) where diverse orbits can be encountered, so providing this space region an inexhaustible repository of various dynamic problems. Here we can find very elongated orbits, or even very oblique ones, the explanation of which can be very important from the point of view of planetary evolution. In the first part of our research, we will systematically apply the method FAIR to identify the dynamically relevant MMRs between TNOs and Neptune. Our plans also include the construction of an online database listing both the dynamic and physical properties of individual TNOs.


Kővári Emese, Kovács Tamás, Forgács-Dajka Emese (2022.01.01 - 2022.03.30)
Eötvös Loránd University, Center for Astrophysics and Space Science

Abstract: The trans-Neptunian space is of great interest of dynamical studies with an inexhaustible number of intriguing problems to be solved. Our aim is to carry out a large-scale survey of trans-Neptunian objects (TNOs) by means of dynamical maps. In the first part of the research, we concentrate on the dynamical role of mean-motion resonances (MMRs) among the TNOs, and the tools of understanding are dynamical maps of classical chaos indicators. In the second part, our focus becomes the quantification of the chaotic diffusion and that of the stability times of the small bodies. The chaotic diffusion is of fundamental importance for its rate will determine the long-term dynamics of a given celestial system. To estimate the rate of the diffusion (that is, to compute the diffusion coefficients) in the case of the 4125 TNOs selected in the first part of our study, we initiate the use of the Shannon entropy. This latter quantity allows, on the one hand, to measure the extent of unstable regions in the phase space (and thus serves as an indicator of chaos), and also enables the direct measurement of the diffusion coefficients. The characteristic times of stability - in the case of normal diffusion - are then achieved by taking the inverse of the diffusion coefficients. In the knowledge of the chaotic diffusion and stability times for as large a TNO sample as the one indicated above, the overall structure of the trans-Neptunian space might be mapped as well, along with the specification of dynamical classes or the update of the existing ones.


Kovács Tamás, Kővári Emese, Forgács-Dajka Emese (2022.01.01 - 2022.03.30)
Eötvös Loránd University, Center for Astrophysics and Space Science

Abstract: The long-term dynamical evolution is a crucial point in recent planetary research. Although, the amount of observational data is continuously growing and the precision allows us to obtain accurate planet orbits, the canonical stability analysis still requires N-body simulations and phase space trajectory investigations. We propose a method for stability analysis of planetary motion based on the generalized Rényi entropy obtained from a scalar measurement. The radial velocity data of the central body in gravitational three-body problem is used as the basis of a phase space reconstruction procedure. Then, Poincaré's recurrence theorem contributes to find a natural partitioning in the reconstructed phase space to obtain the Rényi entropy. High performance computing of phase space reconstruction and matrix manipulations allows us to investigate large data sets and long time series. It turns out that the entropy-based stability analysis is in good agreement with other chaos detection methods.


Gábor Bíró, Gábor Papp, Gergely Gábor Barnaföldi, Balázs Majoros (2021. 06.01 – 2022.03.30)
Wigner Research Centre for Physics and Eötvös University

Abstract: At the world largest particle accelerators such as the Large Hadron Collider at CERN or the Relativistic Heavy Ion Collider at BNL, hundreds of thousands of interesting interactions may occur in every second. A special subset of these events are the high-energy heavy-ion collisions, aiming to investigate the birth of the Universe itself. These experimental measurements are always accompanied by numerical calculations, such as Monte Carlo event generators. However, these calculations are computationally very intensive: even with a state-of-the-art desktop machine many CPU hours (days, weeks sometimes) are needed to simulate only a few seconds of real experimental data. Additionally, with the future improvements of the LHC it will be an even bigger challenge to catch up computationally. The HIJING++ framework is the next generation of high-energy heavy-ion Monte Carlo event generators. Equipped with the latest theoretical models, it is designed to perform precise calculations in a flexible, fast, CPU parallel way. Using multicore architectures, a decent speedup can be achieved, reducing the necessary computational time and the additional costs as well.


Ernő Dávid, Dávid El-Saig, Zoltán Lehóczky and Gergely Gábor Barnaföldi (2021.12.01 - 2022.04.30)
Wigner RCP and Lombiq Technologies Ltd. cooperation

Abstract: Hastlayer by Lombiq Technologies allows software developers of the .NET platform to utilize FPGAs as compute accelerators. It converts standard .NET constructs into equivalent hardware implementations, automatically enhancing the performance while lowering the power consumption of suitable algorithms. Developers keep writing .NET programs as usual, no hardware design knowledge is required.

Hastlayer needs dedicated firmware and software components for each supported hardware platforms. In collaboration with Wigner RC there are already several supported platforms (like Microsoft Catapult cards and the Xilinx Alveo FPGA card family). The aim of the next development phase is to enable Hastlayer support for embedded platforms like FPGA cards based on the Xilinx Zynq family members.

Wigner's task is to develop the necessary firmware framework to run the Hastlayer-generated hardware cores and if there is a need then customize the Linux operating system running on the embedded ARM CPU cores.

István Csabai, Ákos Gellért, Balázs Pál (2022.01.01 - 2022.03.30)
ELTE Department of Physics of Complex Systems

Abstract: The COVID-19 epidemic created an extraordinary situation for the whole humanity, claiming millions of lives and causing a significant economic setback. At the same time, the international research community has rapidly generated an order of magnitude larger data set than ever before, which can contribute to understanding the evolution and dynamics of the epidemic, to its containment and to the prevention of similar pandemics. The GISAID and COVID-19 Data Portal databases contain millions of complete SARS-CoV-2 genomes. The genetic sequences can be obtained relatively easily and quickly thanks to modern genome sequencers, but it is very difficult to tell how rapidly a given variant will spread or how serious disease will it cause, solely based on the genetic sequences and the mutations. The genetic information is transcribed into proteins, and the spatial structure, charge distribution and interaction of the proteins with the host proteins determine the function of the virus, the so called phenotype. In summary, the genotype-phenotype problem is the estimation of the behaviour of a virus based on genetic information.

In the last year, the rapidly developing artificial intelligence approach has achieved a milestone that can significantly help genotype-phenotype research. Using the Alphafold2 method, the spatial structure of large proteins can be determined with sufficient accuracy in a reasonable time. The machine learning-based Alphafold2 method requires significant computational, mainly GPU, capacity.

We are collaborating with EMBL-EBI on the development of a SARS-CoV-2 genetic archive in the framework of a H2020 project. We aim to complement this with 3D structures of proteins of as many variants as possible and to use these structures to advance the genotype-phenotype question.


Marcell Stippinger, András Telcs (2022.01.01 - 2022.03.30)
Wigner Research Centre for Physics

Abstract: The aim of the project is to develop a framework in which causal connection between time series can be explored. The core concept of the project is the investigation of Markov properties of different conditioned time series. The core of the method is the collection of result of large amount of conditional independence tests. The results then lead to a simple conclusion via a simple decision tree.


Sudár Ákos, Varga-Kőfaragó Mónika, Barnaföldi Gergely Gábor és Légrády Dávid (2021.07.01 - 09.30)
Wigner Research Centre for Physics és BME Institute of Nuclear Techniques

Abstract: The goal of development of proton computed tomography is the accurate measurement of the relative stopping power (RSP) distribution of the patient, which is necessary to reduce safety zones around the tumor in proton therapy. During the pCT imaging the patient is imaged by protons, which has determined direction and energy before they go into the patient, and their direction and energy is measured after they come out of the patient. From this information the most likely path (MLP) and the energy deposition in the patient can be determined. The 3D image is reconstructed from the measured data with the use of order suppressed expectation maximalization (OSEM) algorithm, which is an accelerated version of maximum likelihood expectation maximalization (ML-EM) algorithm. The goal of the current project is to develop an image reconstruction code, which runs in parallel threads of CPU and use GPU as well to minimize the image reconstruction time. This software will be used in the future to reconstruct the measured data of a pCT detector developed by the Bergen pCT Collaboration. This work would be contribution to the work of the group and their later publications.


Dr. Papp Gábor (ELTE), Bíró Gábor (Wigner FK), Feiyi Liu (ELTE), Xiangna Chen (CCNU, Wuhan), Dudás Bence (ELTE), Misur Patricia (ELTE) (2021.06.01-08.31)

Abstract: One effective way to kill localized cancerous tumors that are not accessible by surgery is radiation treatment with a proton (or heavier ions as He or C, respectively). In the process, one treatment is usually sufficient compared to conventional radiation therapy, since the proton is very well focused, (with an accuracy of 1 mm, heavier ions with even greater accuracy). However, because the in matter penetration profiles of proton and gamma rays are different, CT tomography does not calibrate the proton beam and does not allow accurate device alignment, resulting in practice in treatment that is far less accurate than the theoretical limit. Greater accuracy can be achieved by proton tomography using a proton beam used for treatment at a higher energy. To detect particles passing through the patient, we developed a detector system based on ALPIDE chips and CERN technology in the framework of the international pCT collaboration ( Because processing of the detector signals is a time-consuming process, we want to speed it up by using a neural network: the goal is to develop and train a neural network that can tell the direction and energy of protons leaving the body based on detector signals. By measuring these at several angles, a tomographic image of the examined area can be obtained and the data required for the treatment can be calculated.

Emese Forgács-Dajka*, István Balla** (2021.05.01-2021.11.31)

* Eötvös University, Dept. of Astronomy
** Solar Physics and Space Plasma Research Centre (SP2RC), Department of Applied Mathematics, The University of Sheffield

Abstract: We investigate the nature and properties of shock waves propagating in an oblique direction to the ambient magnetic field in a partially ionised plasma modelling the plasma of solar prominences. In particular, we aim to analyse the observational signature of these shocks and investigate how our results can explain the recent observations of propagating bright blobs in solar prominences by Lin et al. (2012).

The equations of compressional single-fluid magnetohydrodynamic (MHD) equations are reduced with the help of a multiple scaling method to a well-known Burgers equation whose coefficients depend on the propagation angle of shock waves, plasma-β and the ionisation degree of the plasma. Our model is well-adapted for the separate discussion of shock waves arising from the nonlinear steepening of slow or fast magnetoacoustic waves. Using the standard jump conditions across the shock front (assuming a weak dissipation) we determine the jump in thermodynamic quantities that will be useful for comparison with observations.

Using the Cole-Hopf transform we solve the governing equation as an initial value problem of a diffusion-like equation and investigate the time necessary for a Gaussian initial wave profile to evolve into a shock, whose thickness is of the order of a few ion mean free path.

István Papp, Larissa Bravina, Mária Csete, Igor N. Mishustin, Dénes Molnár, Anton Motornenko, Leonid M. Satarov, Horst Stöcker, Daniel D. Strottman, András Szenes, Dávid Vass, Tamás S. Biró, László P. Csernai, Norbert Kroó (2020.10.16 - 2021.12.31)

Publication: Laser Wake Field Collider

Abstract: Inertial Confinement Fusion is a promising option to provide massive, clean, and affordable energy for humanity in the future. The present status of research and development is hindered by hydrodynamic instabilities occurring at the intense compression of the target fuel by energetic laser beams. NAno-Plasmonic, Laser Inertial Fusion Experiments (NAPLIFE) were proposed, as an improved way to achieve laser driven fusion. The improvement is the combination of two basic research discoveries:
(i) The possibility of detonations on space-time hyper-surfaces with time-like normal (i.e. simultaneous detonation in a whole volume)[1] and
(ii) to increase this volume to the whole target, by regulating the laser light absorption using nano-shells or nano-rods as antennas [2].
These principles can be realized in an in-line, one dimensional configuration, in the simplest way with two opposing laser beams as in particle colliders [3]. Such, opposing laser beam experiments were also performed recently. Here we study the consequences of the Laser Wake Field Acceleration (LWFA) if we experience it in a colliding laser beam set up. These studies can be applied to laser driven fusion, but also to other rapid phase transition, combustion, or ignition studies in other materials.

[1] L. P. Csernai and D. D. Strottman, “Volume ignition via time-like detonation in pellet fusion,” Laser Part. Beams. 33 (2), 279--282 (2015).
[2] L. P. Csernai, N. Kroo, and I. Papp, “Radiation dominated implosion with nano--plasmonics,” Laser Part. Beams. 36 (2), 171--178 (2018).
[3] L.P Csernai, M. Csete, I.N. Mishustin, A. Motornenko, I. Papp, L.M. Starov, H. Stöcker, N. Kroó, "Radiation dominated implosion with flat target", Physics of Wave Phenomena, 2020, accepted for publication.

David Legrady, Gabor Tolnai, Tamas Hajas, Előd Pázmán (2021.06.01 - 2022.04.30)
BME Institute of Nuclear Techniques

Publication: Full Core Pin-Level VVER-440 Simulation of a Rod Drop Experiment with the GPU-Based Monte Carlo Code GUARDYAN

Abstract: The GUARDYAN (GPU Assisted Reactor Dynamic Analysis, developed at BME Institute of Nuclear Techniques) Monte Carlo code directly follows the time evolution of the neutron field in a nuclear reactor. Contrary to the conventionally applied deterministic (i.e. non-Monte Carlo) or Monte-Carlo based techniques relying on quasistatic approximations modelling errors are minimal for GUARDYAN. For a fast evolving („hard”), localized transients even the magnitude of the modelling errors posed by conventional techniques can hardly be estimated, and experimental confirmation due to nuclear hazards is out of question. Therefore, simulations with GUARDYAN could be set as a gold standard for other computational methods. The project aims at the simulation of a rod ejection transient in a full-scale currently operational nuclear power plant type (VVER-440) using the code GUARDYAN.