Dátum: December 14.
Előadó: Ujhelyi Ferenc (Semilab)
Előadás címe: Developing optical metrology for semiconductor industry
The most important optical metrology methods developed by Semilab will be presented. Challenges and competences of the development will be outlined, together with possible collaboration fields.
Dátum: December 1.
Előadó: Jiwuer Jilili
Előadás címe: Perovskites oxides: electronic structure, transport dynamics, and spin exchange
The development of growth techniques of perovskites and latest advances in terahertz field sources for probing the ultrafast magnetism enable researchers to discover and control the exotic electronic and magnetic properties in perovskites. For instance, control of the spin dynamics in DyFeO3 at femtosecond time scale at low temperature has been demonstrated, magnetism at the CaRuO3/CaMnO3, BiMnO3/SrTiO3 interfaces[2,3], metallicity and/or superconductivity at the LaAlO3/SrTiO3 interface have been found. Interfacial magnetism is of particular interest due to potential applications on spintronics, optoelectronics and for fundamental science. In magnetic interfaces, induced orbital reconstruction results in modified exchange interaction, and thus substantially affects spin transport and associated dynamics. Probing and controlling the ultrafast spin flip processes make it possible to engineer useful perovskite interfaces for suitable applications.
In this work using first principles calculations, we investigate formation of an interface with a pseudo-half-metallic character as a possible route to enhance the thermoelectric behaviour of SrTiO3-based oxide materials. Doping, strain, O defects are major factors that influence the functional properties of these materials. We study the effects of O vacancy on the local electronic structure of BiMnO3/SrTiO3 and demonstrate for n-type interface, a substantially high figure of merit. We identify the underlying spin transfer through ferromagnetic dynamics in these class of materials, and associate spin currents through the transport channels in response to a thermoelectric bias. In another perovskite, Co doped SrTiO3 shows large thermoelectric properties due to doping induced insulator to half-metalic transition, this property has promising application potential on spin-caloritronics.
We further discuss LaNiO3/CaMnO3, another new superlattice where thickness related metal-insulator transition has been found experimentally along with the observation of the interfacial magnetism. It is important to investigate its thickness dependent electronic, structural properties as
well as the effect of the spin exchange on the the coexistence and commutation of the two spin channels which result in interesting and tunalble spin dynamics. Experimentally probing and contrlolling the spin flip process in perovskite materials opens a new era of magnetic materials with tailored magnetic behaviour. We examine how the interplay and dynamics of interface spin plays major role in the performance of such interfaces.
Fig. 1. Schematic structure of the (LaNiO3)2/(CaMnO3)8 superlattice (left) and spin ordering for different LaNiO3 thicknesses (right)
 A. V. Kimel et al, Nature, 345, 655 (2005).
 K. S. Takahashi et al, Appl. Phys. Lett. 79, 1324 (2001).
 M. Salluzzo et al, Phys. Rev. Lett. 111, 087204 (2013).
 M. Upadhyay Kahaly et al, J. Mater. Chem. A, 1, 8406 (2013).
Dátum: október 13.
Előadás címe: Perspectives of Ion Acceleration
Experiments on ion acceleration driven by high intensity lasers over the past ∼15 years have demonstrated the generation of multi-10s of MeV proton and ion beams with remarkable properties such as ultrashort burst emission, high brilliance, and low emittance over a wide range of laser and target parameters.
Nowadays accessible intensities, beyond 1020 W/cm2, have provided for the first time the opportunity to extend scaling laws for the acceleration process, and to access new ion acceleration regimes. After short survey of relevant background, this presentation will discuss the recent experimental findings and also on ion acceleration obtained on PW laser. In most laser-driven ion acceleration studies the sheath field established by relativistic electrons at target surface accelerates ions, via the so-called Target Normal Sheath Acceleration (TNSA). A separate mechanism, Radiation Pressure Acceleration (RPA), has attracted extensive theoretical attention in recent years. Radiation pressure is exerted via laser ponderomotive force on a foil surface, which results in local electron-ion displacement, and ion acceleration via the ensuing space-charge field. In newly found scenario at PW laser power, which offers more favorable proton energy scaling with laser intensity than “ordinary” TNSA, the ions are accelerated in the electrostatic field of charged cavity created by relativistic laser pulse at the target front and in the enhanced sheath field at the target rear.
These developments have stimulated the emergence of a new ideas and advanced diagnostic development for measuring plasma effects and secondary source emission with high dynamic range, spatial and spectral resolution, on a single shot basis, also in order to benchmark simulations. We will discuss the comprehensive on-line diagnostic systems allowing an extensive and thorough research of laser-plasma processes, providing essential information on their complex dynamics, characterization of the ion emission and accelerated beam properties.
This presentation is closely related to recent development or imminently anticipated development of laser technology to bring the existing laser systems to a multi-PW level. Recent findings pave a way to achieving an ion source and beam desire parameters and they encourage further activities for optimisation of laser plasma-based accelerators.
Dátum: szeeptember 29.
Előadó: Horváth Péter (Szegedi Biológiai Kutatóközpont / Institute for Molecular Medicine, Finland)
Előadás címe: Stimulated emission, multiphoton processes and attosecond science viewed from a historical perspective
Life beyond the pixels: phenotyping using machine learning and image analysis methods
I will give an overview of the computational steps in the analysis of a single cell-based large-scale microscopy experiments. First, I will present a novel microscopic image correction method designed to eliminate vignetting and uneven background effects. Single-cell image segmentation methods will then be presented using energy minimization methods. I will discuss the Advanced Cell Classifier (ACC) (www.cellclassifier.org), a machine learning software tool capable of identifying cellular phenotypes based on features extracted from the image. It provides an interface for a user to efficiently train machine learning methods to predict various phenotypes. Our recently developed single-cell isolation methods, based on laser-microcapturing and patch clamping, utilize the selection and extraction of specific cell(s) using the above machine learning models.
Caicedo, J. C., ..., Molnar, Cs., ..., Horvath, P., Linington, R. G., Carpenter, A. E. (2017)
Data-analysis strategies for image-based cell profiling.
Piccinini, F., Balassa, T., Szkalisity, A., Molnar, Cs., Paavolainen, L., Kujala, K., Buzas, K., Sarazova, M., Pietiainen, V., Kutay, U., Smith K., Horvath, P. (2017)
ACC: Discovery software for phenotypic image analysis.
Horvath, P., Aulner, N., Bickle, M., Davies, A., Del Nery, E., Ebner, D., Montoya, M., Ostling, P., Pietiainen, V., Price, L., Shorte, S., Turcatti, G., von Schantz, C., Carragher, N. (2016)
Screening out irrelevant cell-based models of disease
Nature Reviews Drug Discovery
Molnar, Cs., Jermyn, I., Kato, Z., Rahkama, V., Ostling, P., Mikkonen, P., Pietiainen, V., Horvath, P. (2016)
Accurate Morphology Preserving Segmentation of Overlapping Cells based on Active Contours
Koos, K., Molnar, J., Kelemen, L., Tamas, G., Horvath, P. (2016)
DIC image reconstruction using an energy minimization framework to visualize optical path length distribution.
Smith K., Li Y., Piccinini F., Csucs G., Balazs C., Bevilacqua A., Horvath, P. (2015)
CIDRE: an illumination-correction method for optical microscopy.
Dátum: szeptember 15.
Előadó: Varró Sándor
Előadás címe: Stimulated emission, multiphoton processes and attosecond science viewed from a historical perspective
The process of stimulated emission of radiation will be discussed, first in the context of black-body radiation, as it appeared more than hundred years ago in the works of Planck and Einstein. Later results concerning negative absorption, amplification and laser action will also be reviewed, including multiphoton processes which take place during the interaction of very-large-intensity lasers with various constituents of matter. These high-order processes result in large spectral broadening, and may lead to extreme temporal localization of the signals, thus yielding e.g. attosecond light pulses. The development of theoretical methods, interpretations and some examples of basic experimental achievements will be analysed. At the centenary of the first publications on the concept of stimulated emission, we attempt to build a bridge between the early thoughts and recent studies of attosecond and strong-field science.
Dátum: Szeptember 8.
Előadó: Prof. Hans-Jörg Kull (Institute for Theory of Statistical Physics, Laser Physics Group, RWTH Aachen University)
Előadás címe: Electron dynamics in strong laser fields
Strong and short laser pulses provide new experimental techniques to study electronic motion on atomic scales. In above threshold ionization of atoms, the energy gain of photoelectrons is increased by electron-ion collisions. Heating of plasmas by inverse bremsstrahlung absorption is based on electron-ion collisions correlated by the laser field. In this talk we will review and extend theories and computations on electron-ion collisions and above threshold ionization in strong laser fields. Starting from classical instantaneous collisions, we illustrate time-dependent behaviour by a classical binary collision model. The quantum-mechanical behaviour is then studied in terms of numerical solutions of the time-dependent Schrödinger equation and by analyzing the evolution of the corresponding Wigner quasi-probability in phase space[2, 3].
 G. Rascol, H. Bachau, V. T. Tikhonchuk, H.-J. Kull, T. Ristow, Phys. Plasmas 13, 103108 (2006).
 H.-J. Kull, New J. Phys. 14, 055013 (2012).
 C. Baumann, H.-J. Kull, and G.M. Fraiman, Phys. Rev. A 92, 063420 (2015).
Dátum: május 12.
Előadó: prof. Udo Schwingenschlögl
Előadás címe: Exotic topological phase transitions in TlBiS2 and monolayer AsSb
The potential of TlBiS2 to exhibit topological phase transitions is addressed by computational methods based on parity and surface state analyses. Zero, one, and four Dirac cones are found for the (111) surface under growing hydrostatic pressure. The Dirac cones at the points are anisotropic with large out-of-plane spin component. TlBiS2 realizes normal, topological, and topological crystalline insulator phases, thus being the first compound to exhibit a phase transition between topological and topological crystalline insulators. While monolayer As and AsSb are semiconductors (direct band gap at the point), fluorination results in Dirac states at the points. Fluorinated monolayer As shows a band gap of 0.16 eV due to spin-orbit coupling and fluorinated AsSb a band gap of 0.37 eV due to inversion symmetry breaking. Calculations of the edge states of nanoribbons by the tight-binding method demonstrate that fluorinated monolayer As is topologically nontrivial in contrast to fluorinated monolayer AsSb.
Dátum: április 21.
Előadó: Dr. Martina dell’Angela (Istituto Officina dei Materiali, ELETTRA Trieste, Italy)
Előadás címe: Femtosecond soft X-ray Spectroscopy for Femtochemistry and Photovoltaics
The study of charge dynamics in chemical processes at surfaces by measuring in real time the changes of the electronic structure of the materials is nowadays possible thanks to the advent of free-electron lasers FELs. We studied photocatalytic reactions at surfaces by recording electronic structure changes in the femtosecond and picosecond timescale after an optical excitation. I will briefly present our time resolved resonant x-ray emission (RXES) study at FELs of the first picoseconds in CO desorption and oxidation reactions triggered by optical pulses [1, 2]. Besides photon in-photon out probing techniques like RXES, photon in-electron out techniques like PES can also be employed for the electronic structure study. I will discuss the advantages and limitations on the usage of time resolved photoemission (PES) for such measurements at FELs . I will present a preliminary time resolved PES experiment performed at a synchrotron facility to explore the charge dynamics induced by sunlight in donor/acceptor molecular systems and describe the set-up for optical pump- PES probe we are are currently building at ALOISA beamline of the Elettra synchrotron.
Dátum: március 24.
Előadó: Budai Judit (Ultragyors nanotudomány csoport, Tudományos alkalmazások osztálya)
Előadás címe: Measurement of Nanoplasmonic Field Enhancement with Ultrafast Photoemission
The measurement of nanoplasmonic near fields is a fundamental question of nanooptics. A new method  was introduced at the beginning of this year that utilizes ultrafast photoemission from plasmonic nanostructures and is capable of probing the maximum nanoplasmonic field enhancement.
In this talk I will give a short introduction to plasmonic structures, present the details of the new method and give insight into the finite-difference time-domain simulations that were performed at ELI-ALPS for the validation of the field enhancement values measured by applying the novel approach.
Dátum: március 9.
Előadó: Todd Jaeger
Előadás címe: Presentation and interactive discussions on New Laser Glass Materials and Components, Manufacturing and Coating of Ultraprecise Laser Glass Components
Laser use is ubiquitous in everyday life. What was once a solution seeking a problem is now present in the production of nearly everything we touch. New applications need new materials to address the broad range of today’s technology. Laser glass, once perceived as useful only in complex scientific applications, is now finding its way into a wide array of commercial, medical and consumer-based uses. Brought about by advances over the last several years in new formulations of laser glass created by SCHOTT, these new gain materials move advanced laser technology from the hands of highly skilled technicians and PhDs and into robust commercial uses. Of particular interest are SCHOTT’s latest formulations: BLG-80 and LG960 Laser Glass.
There are many difficulties involved in the manufacture of ultraprecise glass components and coatings that have the durability to withstand laser radiation with very high power density. These include how best to polish and clean the glass, how to minimize subsurface damage, the ideal approach to coating, the right materials to use, how to increase the Laser Induced Damage Threshold (LIDT), and the many tradeoffs involved.
Dátum: január 13.
Előadó: Petar Lambrev (a Szegedi Biológiai Kutatóközpont Fotoszintetikus Membrán Csoport vezetője)
Előadás címe: Multidimensional Electronic Spectroscopy of Energy Transfer in Photosynthetic Systems
Photosynthesis is initiated by capturing photon energy and creating electronic excitations in the photosynthetic light-harvesting complexes. The overall efficiency of photosynthesis depends on the ability to transfer the excitation energy to the photochemical reaction centre without losses. Resolving energy transfer, which involves many ultrafast steps between molecules with near-identical spectral properties, is a challenging experimental task. Two-dimensional electronic spectroscopy (2DES) is a powerful experimental technique that can map energy transfer pathways by correlating the excited state energies of the donor and acceptor states and following the process in time. Multistep energy transfer can directly be probed by three-dimensional spectroscopy (3DES) that, in turn, correlates the energies of the donor, intermediate and acceptor states and the respective energy transfer time scales. Our 2DES and 3DES experiments on plant light-harvesting complex II reveal the pathways and dynamics of energy transfer in extraordinary detail.
Dátum: november 25.
Előadó: Sándor Varró
Előadás címe: Wide-angle interference of a single-photon emitter for measuring its position on nanometer scale
Single-photon wide-angle intereference phenomena have been studied theoretically for glass-diamond-oil and glass-diamond-air layered structures. As a single optical emitter (of wavelength e.g. 637 nm) one nitrogen-vacancy center (NV-center) has been assumed, which is placed close to the upper side of a diamond plate, and it was represented by a Hertzian dipole of arbitrary orientation. The interference fields can be imagined as resultans of superposition of rays emanating from the NV-center directly upwards and from those which are emanating downwards and undergo total internal reflection at the lower surface of the diamond plate of thickness e.g. 0.1mm = 100000 nm . The direct and the reflected rays recombine on the upper side, and we have proved that also the far-field interference pattern is sensitive to the vertical position of the NV-center (see illustration in Figure 1). As is seen, e.g. 2nm difference in distance of the emitter from the upper surface of the diamont results in an angular shift of order 0.01 degree of the pattern, which should already be a measurable effect.
Dátum: október 11.
Előadó: Prof. Matthias Bickelhaupt (Amsterdam Center for Multiscale Modeling, Vrije Universiteit Amsterdam, and Radboud University, Nijmegen, The Netherlands
Előadás címe: Hypervalent Carbon, or How to Freeze the SN2 Transition State
Silicon in [Cl-SiH3-Cl]– is hypervalent whereas carbon in [Cl-CH3-Cl]– is not. The latter species is a first-order saddle point, a transition state for bimolecular nucleophilic substitution (SN2) reaction, which connects two stable, tetra-valent carbon species. In this talk, I show how the different behavior of silicon and carbon can be understood in terms of the Ball-in-a-Box (BiaB) model, based on modern Kohn-Sham molecular orbital (KS-MO) theory. The illustration below is an artist's impression of the essence of the BiaB. It holds the clue to answering the question about the different bonding capabilities of C and Si.
Proceeding from the insights emerging from KS-MO analyses and the above BiaB, I will develop a strategy for creating a stable species involving a truly hypervalent, five-coordinate carbon atom. If successful, this quest would come down to a violation of the octet rule for carbon! One might conceive this also as "freezing" the SN2 transition state, turning the otherwise labile species into a stable equilibrium structure.
Dátum: Szeptember 26.
Lecturer: Molnár István
Előadás címe: The Intellectual Property Policy of ELI-HU Ltd, and the management of IPs at ELI-HU Ltd.
Topics to be addressed:
a) Introduction of the IP Policy at ELI;
b) The objectives of the IP Policy;
c) The subject matter IP according to the IP Policy;
d) The employees and agents subject to the IP Policy;
e) Remuneration of the inventors according to the IP Policy;
f) Procedures and responsibilities: invention disclosure, IP prosecution, technology-transfer;
g) Valuation of IP;
Dátum: Szeptember 9.
Lecturer: Papp Dániel
Előadás címe: Modeling and experimental benchmarking of a high repetition rate laser-plasma hard x-ray source
Laser-plasma based high repetition-rate hard (6 keV+) x-ray sources were the subject of extensive studies, with such systems implemented at research facilities and available commercially. Such x-ray sources are used in diverse pump-probe experiments and also have prospective biomedical imaging applications. The operational regime of such sources can be extended into the ultrafast (10-50 fs) range with a tabletop setup, with few-cycle driving lasers and suitable target selection.
In this talk I will discuss the physical processes in the generation of hard x-rays in such sources. These processes were modeled using the EPOCH Particle-In-Cell and GEANT4 Monte-Carlo code packages. Experiments were conducted on an ultrashort pulse, 1 kHz repetition-rate laser using solid targets at the CLPU laser facility in Salamanca, Spain. The obtained experimental results were used for benchmarking the simulation.
Dátum: szeptember 2.
Lecturer: Polner Mónika
Előadás címe: Scattering of ultrashort electromagnetic pulses on a system of two parallel current sheets: the role of the radiation reaction and of the time delay
The reflection and transmission of a few-cycle laser pulse impinging on two parallel thin metal layers have been analyzed. Our model is an extension of the one-layer scattering problem described in [1-3], and the analysis is based on classical electrodynamics and mechanics. The two layers, with thickness much smaller than the skin depth of the radiation field, are represented by current sheets, which are embedded in three dielectrics, all with different index of refraction. The dynamics of the surface currents and the complete radiation field are described by the coupled system of Maxwell-Lorentz equations.
In our analysis particular attention has been paid to the role of the radiation reaction and of the time delay. There are several sources of time delay in the extended system: due to the angle of incidence of the impinging laser pulse and due to the propagation time between the two surface current sheets. In this presentation we show the analytic solution of the resulting coupled delay differential-difference system of equations when the three dielectrics have the same index of refraction, besides, we show some numerical studies of the most general case. The main emphasis is on the effect of the delay on the dynamics of the system.
Dátum: július 8.
Előadó: Jörg Pawelke (OncoRay – National Center for Radiation Research in Oncology, Dresden, Germany; Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden; and Helmholtz-Zentrum Dresden-Rossendorf)
Előadás címe: Beam transport and monitoring of laser-driven particle beams
Particle acceleration by high intensity lasers promises more compact and cost effective ion sources as well as electron beams of very high energy for radiotherapy application. In contrast to pencil-like, monoenergetic, and (quasi) continuous beams from conventional accelerators, laser-driven beams are characterized by short pulses of very high particle flux, low repetition rate, broad energy spectrum, large divergence and significant pulse-to-pulse fluctuation. In consequence, a future medical application requires not only a high power laser system and laser target to generate particle beams of therapeutic quality but also new technical solutions for suitable beam detection and dosimetry, beam transport, dose delivery including treatment planning along with research on the radiobiological consequences of short radiation pulses with ultra-high pulse dose rate. The status of the ongoing joint translational research project onCOOPtics of several institutions in Germany will be presented with an emphasis on beam detection and beam transport via pulsed magnets.
Dátum: július 1.
Előadó: Lécz Zsolt
Előadás címe: Short Wavelength Radiation in Laser-Plasma Interactions
Interaction of relativistically intense laser pulses with matter involves highly nonlinear processes and produces energetic charged particles and photons with unique properties. Numerous mechanisms have been identified for ion acceleration or for high harmonic acceleration, but their efficiency is usually very low. Our primary goal is to increase the energy conversion efficiency from laser pulse into higher harmonics. The synchrotron radiation emitted by relativistic electrons oscillating in magnetic undulators is a powerful source of short wavelength X-ray radiation. Electrons oscillate at the laser-plasma interface as well, where they have complicated trajectory and can emit synchrotron-like coherent or incoherent radiation, depending on the plasma density and surface structure. In this work we investigate such interactions with solid density cylindrical targets or flat foils equipped with nanorods or microdots on their surfaces. In the presentation we show results of 2D/3D particle in cell simulations, which are helpful tools in modeling of such non-linear phenomena.
Dátum: június 10.
Előadó: Dombi Péter
Előadás címe: Towards ultrafast, nanoscale optical switching
Nano-optical near fields, generated, for example, by plasmon oscillations have several unique properties. Hundred-times electric field enhancement and few-nanometer field localization of a laser pulse can be easily achieved. If we induce plasmon oscillations with ultrashort pulses, high spatiotemporal localization and highly nonlinear interactions are possible. Both are prerequisites for ultrafast, nano-integrated optical devices. As first steps in this direction, I will show new methods to characterize nano-optical near fields with nanometer resolution and ways to generate nonlinear interactions with low-energy laser pulses.
Dátum: május 27.
Lecturer: Janáky Csaba
Előadás címe: Chemical and Materials Aspects of Ultrafast Dynamics in Semiconductors: State-of-the-Art and Future Opportunities
Various photoinduced processes in semiconductors occur at distinctly different timescales. Ultrafast laser spectroscopy has been long the tool for examining mechanistic aspects of light induced processes in semiconductors as well as at semiconductor interfaces. So far, most of the work has focused mainly on transient absorption spectroscopy, at relatively long timescales (typically ns-ms, sometimes ps), where charge transfer, recombination, and different surface reactions occur. On the other hand, much less is known about the photo-excitation process itself, carrier cooling and trapping, which occurs at the femtosecond timescale.
We aim to understand the peculiar conduction mechanisms (including photoinduced charge carrier formation, exciton dissociation, recombination, etc.) in different classes of semiconductors; such as organic semiconductors (conjugated polymers), different 1D and 2D inorganic semiconductors (this latter group is also called topological insulators, such as MoS2 and NbSe2), and organic-inorganic hybrid materials (for example organic lead halide perovskites). While these materials play an impressively increasing role in different practical applications, very little is known about the fundamentals of the mechanism of (photo)conductivity (which forms the basis of most applications) observed in these materials.
In this talk I will first present the background of the research and some of the previous achievements of the PI. Subsequently, I will summarize the state-of-the-art how ultrafast laser pulses can be employed as tools to characterize the above listed phenomena in different nanomaterials. Among others, I will focus on the physico-chemical implications of temporally (and spatially) resolved two-photon ultraviolet photoelectron spectroscopy, and the nanoscale aspects of time-resolved HZ spectroscopy, from the Chemists’ perspective. Finally, I will highlight some of our future plans.
Előadó: Mousumi Upadhyay-Kahaly
Előadás címe: Probing the structure and dynamics of nanomaterials and molecules
Modern technology entails the manipulation of matter on ultrashort scales, and measurement of the dynamic processes in ultrafast domain. Thus "ultrafast science" impacts multiple areas of modern physics, chemistry, biology, materials science, engineering etc. Formation and breaking of chemical bonds occur in femtosecond time scale, and thus, elementary molecular processes can be observed and utilised by freezing the transition states of chemical processes at ultrashort time scale, even shorter than the vibrational and rotational periods in matter. Along with the technological advances, ultrafast lasers, such as in ELI-ALPS, are employed to probe the molecular systems, to understand their time evolution and, to investigate intricate details of the time-resolved behavior of matter.
However limitations in controlling the experimental parameters and data processing requires theoretical tools to support and complement while probing the evolution of the electronic structures post controlled excitation in the time domain. In the presentation, we will discuss structure-function relationships in materials using first principles quantum mechanical calculations based on density functional theory and time dependent density functional theory, touching upon different aspects of novel material synthesis, energetics, lower dimensional systems, organometallic substances etc. We will show how theoretical modeling can be efficiently used to explain/predict the functionalities and material response of nanostructures, solids and molecules, with specific focus on their physical properties under interaction with electromagnetic fields and the dynamics associated with the electronic motions of the structure.
Előadó: Huabao Cao
Előadás címe: Polarization Encoded Chirped Pulse Amplification in Ti:Sapphire – a Way towards Few Cycle PW Lasers
We proposed and demonstrated the broadband amplification of short pulses in a polarization encoded (PE) Ti:Sa amplifier. Unlike previous methods based on making a deep in the spectral amplitude of the seed pulse, here the achievable bandwidth is considerably broader along with a lossless overall amplification process. It was shown in our experiments that the PE amplification preserved a bandwidth close to 90 nm of a top hat spectral profile while increasing of the spectral width of a Gaussian pulse by 40%. It was also shown that an additional polarization rotation takes place during the pulse amplification and we suggested to mitigate it with thicker decoding quartz so as to ensure good efficiency, which has been experimentally proved. Because the PE amplifier usually introduces dip in the spectrum, an additional conventional Ti:Sa amplifier was built to smooth the spectrum and also promote the energy. The compressibility of the amplified pulse after the PE amplifier has also been verified by experiment.
According to the simulations, the high energy polarization encoded Ti:Sa amplifiers predicts an amplification bandwidth of 200 nm, making it a promising technique for intermediate and final amplifiers of high field Ti:Sa CPA-laser systems. This technique may pave the way to PW class Ti:Sa lasers with tens of Joule few cycle laser pulses.
Dátum: április 1.
Előadó: Vladimi Chvykov
Előadás címe: High Repetition Rate for Ultra-High Peak Power Laser Systems
Combination of the large aperture Ti:Sa crystals with EDP-technology of the energy extraction in final amplifiers of ultra-high peak power CPA laser systems allowed to achieve recently the record output of 5 PW. 10 PW laser systems under construction right now in the frame of the ELI project and its final goal 200 PW is on the roadmap. Nevertheless, the increasing repetition rate of the laser systems to 10 Hz even with 1-2 PW of the output power (ELI-ALPS) still is a big challenge for laser technology. In our research we have suggested to add to EDP Ti:Sa combination the third element, namely Thin Disk crystal geometry (EDP-TD) to overcome the limitations associated with thermal cooling of crystal and transverse amplified spontaneous emission in high average power laser systems based on Ti:Sa amplifiers. In this talk we will discuss the possible benefits of this idea, as well as the results of proof-of-principal experiments where first time, according to our knowledge, the scheme of EDP-TD was tested.
Dátum: március 18.
Előadók: Csendes Tibor, Bánhelyi Balázs és Csete Mária (Szegedi Tudományegyetem)
Előadás címe: Optimization and simulation for the development of advantageous plasmonic structures
New techniques will be introduced to design tiny optical sensors applying the Matlab based COMSOL simulation program and cleverly formulated constrained nonlinear optimization problems. In this way we could find good solutions that are favorable also with respect to practical realization. We illustrate our methodology on some real life examples. Details of the technique will be highlighted also regarding the limitations, the huge computational complexity, and the evaluation of the results obtained.
Dátum: március 9.
Előadó: Christos Kamperidis
Előadás címe: Ionisation induced electron trapping in the linear regime of a laser wakefield accelerator
The scheme of Laser Wakefield electron acceleration (LWFA) has rapidly matured over the past decade, from proof-of-principle experiments to real life applications, such as non-destructive X-ray imaging. The scheme involves the use of >1 TW laser systems and > 1mm long gaseous targets. In this seminar, we will describe the basic principles of LWFA, show how ionisation injection relaxes the laser requirements to achieve stable relativistic electron beams and outline the potential of these ultra-compact relativistic accelerators.
Dátum: február 26.
Lecturer: Gergely Árpád László
Előadás címe: Gravitational waves: prediction, discovery, prospects
101 years ago the concept of Newtonian gravitational force was replaced by space-time curvature. Matter tells space-time how to curve and space-time tells matter how to move. These effects however are not instantaneous. Gravity propagates with the speed of light. The propagating curvature modulations on the background curvature are the gravitational waves. They are easily produced in the regions of the universe, where the energetics is violent, for example, when black holes collide. Such gravitational waves produced 1.3 billion years ago were detected for the first time on September 14th, 2015 by both Advanced LIGO detectors. During their travel through the Universe, the waves weakened such that they produced a deformation of one part of a thousand of the size of the proton, hence the detection by laser interferometry has been an engineering success. The Advanced LIGO detectors will undergo further improvements, and other similar detectors are on the verge of completion. New types of gravitational wave detectors, either space-born or based on radio interferometry are also envisaged. The era of gravitational wave astronomy has begun, a new window to the Universe has opened.
Dátum: február 19.
Előadó: Füle Miklós
Előadás címe: Reaction microscope and data analysis with GO4
Understanding of the three dimension structure, photochemical dynamics and fragmentation of molecules has improved substantially by variety of spectroscopic method. One of those techniques is the photoelectron spectroscopy in which the high energy photon absorbed by the molecule and an electron ejected subsequently from the atomic system. Based on the new technology development in the last two decades concerning the ultrafast laser technology and time-resolved spectroscopic technology and also the single-particle imaging technology a new powerful spectroscopic imaging method has emerged. Measuring the momentum and angular distribution of photofragment the reaction microscope has become the “bubble chambers of atomic and molecular physics”. In this presentation I am going to give a brief introduction to this technique what will be the one of the end stations of ELI-ALPS HR GHHG systems too.
Dátum: február 19.
Előadó: Csizmadia Tamás
Előadás címe: Introduction to the low density matter end station at FERMI
The FERMI free-electron laser connected to the Elettra synchrotron storage ring at Trieste (Italy) is one of ELIs strategic partners, which provides ultrashort (10-100 femtosecond) pulses with high brightness in the ultraviolet and soft x-ray wavelength ranges. The tuneable, fully coherent pulses of FERMI open up opportunities for exploring transient electron dynamics and controlling electronic wave packets during a photoionization process in gases. During the seminar, I would like to introduce the Low Density Matter end station at FERMI, the operation of its angularly resolved photoelectron spectrometer during experimental runs, and the methods for data collection, processing and interpretation.
Dátum: február 19.
Előadó: Fatemeh Aeenehvand
Előadás címe: An overview of attosecond pulse generation
The first part of this talk is focused on theoretical analysis of high-harmonic generation in solids and comparison with gas. The effects of strength field intensity is considered, the results show a simple approximate cutoff law for HHG in solids. The HHG process using the saddle point approximation is also investigated.
The second part describes the generation and application of attosecond pulse and VIS/NIR probe pulses. Concerning the characterization of the probe pulses, the temporal duration and the carrier-envelope phase (CEP) stability is investigated, finally, the measurement of charge migration in the amino acid Phenylalanine is demonstrated, and it shows that attosecond science offers the possibility to elucidated process ultimately leading to charge localization in complex molecule.
Dátum: február 12.
Előadó: Tőkési Károly
Előadás címe: Classical Trajectory Monte Carlo method – „Watching quantum physics in real time”
Attosecond physics is a new and rapidly developing field driven by recent advances in laser technology. Attosecond science holds the promise to observe and to control the motion of electrons on their natural time scale. It is now possible to take snapshots of electrons in motion in atoms, molecules, and solids. The long-lasting dream of chemists and physicists to watch and to control in real time the formation and breaking of chemical bonds or electrons leaving an atom is now closer to realization than ever. These experimental advances pose considerable challenges for theory.
Time-resolved photoemission experiments employing attosecond streaking of electrons emitted by an extended ultraviolet pump pulse and probed by a few-cycle near-infrared pulse found a time delay of about 100 as between photoelectrons from the conduction band and those from the 4f core level of tungsten. We present a microscopic simulation of the emission time and energy spectra employing a classical transport theory. Our calculations reproduced well both the emission spectra and streaking images. We found delay times near the lower bound of the experimental data.
Photoemission spectra feature also complex correlation satellite structures signifying the simultaneous excitation of single or multiple plasmons. The time delay of the plasmon satellites relative to the main line can be resolved in attosecond streaking experiments. Time-resolved photoemission thus provides the key to discriminate between intrinsic and extrinsic plasmon excitation. We demonstrate the determination of the branching ratio between intrinsic and extrinsic plasmon generation for simple metals.
Dátum: február 10.
Előadó: Franck Lépine
Előadás címe: XUV induced ultrafast mechanisms in molecular structures: from attosecond physics … to astrochemistry
Short XUV pulses combine 2 advantages for physicists and chemists, which are motivating the development of intense research programs worldwide. First, high-energy photons allow the generation of highly excited species and second, short duration gives access to ultrafast phenomena in realtime.
In molecules, short XUV pulses can trigger complex dynamics that can be followed in real-time using pump-probe schemes, down to the attosecond time-scale. Due to high photon energy excitation, induced processes imply interaction between all the particles constituting the molecule (so-called: electron correlation, non-adiabatic couplings etc…). Therefore a theoretical description requires state-of-the-art many-body quantum theories.
Being able to perform such “realtime” experiments, combined with accurate theoretical quantum description in increasingly complex systems is a major challenge for the development of the emerging field of attosecond molecular physics. Although challenging, it is expected that this research activity would have major impact in other fields and would nourish analytical chemistry, molecular electronics, astrophysics and fundamental aspects of quantum mechanics in general.
In this talk, I will present the research program developed in my group to extend XUV induced molecular science to the investigation of increasingly large molecular systems.
Dátum: február 4.
Előadó: Mati Péter
Előadás címe: Soft photon resummation in QED and the Bloch-Nordsieck model
Infrared (IR) singularities in massless gauge theories are known since the foundation of quantum field theories. The root of this problem can be tracked back to the very definition of these long-range interacting theories such as QED. We will briefly review the basics of QED: Lagrangian formalism, Feynman rules, etc... The IR catastrophe and its resolution by cancelling these divergences will be also discussed. The Bloch-Nordsieck model provides the IR limit of QED and in its framework all the radiative corrections to the electron propagator can be fully summed. However, perturbation theory does not provide the right tool for this operation: the exact Dyson-Schwinger (DS) equation needed to be solved with the aid of the Ward-Takahashi identities. Solving the DS equation at finite temperatures is also possible and will be presented in the talk.
Dátum: január 29.
Előadó: Bohus János
Előadás címe: Report on development of an all reflective polarization rotator and an Yb:CaF2 thin disk amplifier
We present a conceptual design of an RDPR (Reflective device for polarization rotation) as a preferable alternative to conventionally used HWPs (halfwave plates). An RDPR has the advantage over HWPs of better accuracy of the polarization angle of the beamline. Furthermore, the spectral transfer function is widely selectable, due to the purely reflective design. Moreover, the device is scalable in size and the damage threshold is only limited by the mirrors, which is considerably higher than for HWPs. Additionally, in comparison to those, RDPRs create no prepulses leading to postpulses generated in the subsequent high-power short-pulse laser chain. Hence, RDPRs are also suitable for the manipulation of the polarization of compressed, and therefore ultra-short laser pulses.
Furthermore we report on development of a thin disk energetic amplifier based on Yb:CaF2. Results of gain, thermal lensing, depolarisation loss, temperature distribution measurements carried out at Institute of Optic in Paris are presented.
Dátum: január 29.
Előadó: Papp Dániel
Előadás címe: Hard x-ray generation experiments on the 1 kHz 22 fs CEP laser at CLPU
The talk would describe initial experiments on the 1 kHz CEP laser at CLPU, Salamanca. The laser setup operated at an intensity of 1×1016 Wcm-2. During the campaign, a liquid target setup suitable for 100kHz repetition-rate applications were investigated. A solid copper target on a high-speed target stage was also installed to test x-ray diagnostics, and the installed delay scheme to provide a controlled laser pre-pulse. The controlled laser prepulse allowed a 4-fold increase in Cu K-α hard x-ray yield. The laser-to-x-ray yield was found to be anomalously low compared to expectation based on similar experiments and simulations.
Dátum: január 29.
Előadó: Mathieu Dumergue
Előadás címe: Circularly polarized XUV attosecond pulse trains generated in aligned CO2 molecules
High order Harmonic Generation (HHG) in gases is the subject of numerous studies since its discovery in 1987-1988. The mechanism of HHG is quite well known in the case of an atomic target, leading to the generation of a linearly polarized XUV attosecond pulse train (or single attosecond pulses under some conditions) with linearly polarized generation field. Unfortunately, the same mechanism forbids the generation of circularly polarized attosecond pulses with atoms and a circularly polarized generation field. In order to overcome this difficulty, several different techniques have been used (two colour HHG, two pulses with opposite helicity, molecular target …).
During this talk, I’ll present an experiment conducted at the FORTH institute in Heraklion, Greece, about the generation of such circularly polarized XUV pulses by HHG in aligned CO2 molecules with circularly polarized generation pulses. Former studies have shown that lower harmonics (the 3rd) can exhibit highly elliptical polarization in the same conditions. The goal of the experiment was to show that higher order harmonics have the same behaviour. I’ll start with a short explanation of the phenomenon and the conditions leading to the generation of circularly polarized XUV pulses, followed by the description of the experimental setup, and finishing with some preliminary results and possible ideas for the improvement of the experiment.
Dátum: január 22.
Előadó: Krasznahorkay Attila (MTA-ATOMKI)
Előadás címe: Perspectives for photofission research at the ELI - Nuclear Physics facility
The perspectives for photofission experiments at the new Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility will be discussed from a point of view of the necessary detector developments.
Photofission measurements enable selective investigation of extremely deformed nuclear states in the light actinides and can be utilized to better understand the landscape of the multiple-humped potential energy surface (PES) in these nuclei. High resolution studies will be performed on the mass, atomic number, and kinetic energy distributions of the fission fragments following the decay of states in the first, second and third minima of the PES in the region of the light actinides. We aim at investigating the heavy clusterization and the predicted cold valleys of the fission potential. Moreover, a special focus on the fission dynamics and clusterization effects in super- (SD) and hyperdeformed (HD) compound states will be addressed. Such fission barrier parameters are crucial inputs also for cross section calculations in the Thorium-Uranium fuel cycle of 4th generation nuclear power plants.
These studies call for developments of state-of-the-art fission detectors to exploit the unprecedented properties of the high-flux, Compton backscattered γ-beams having a very small beam spot size. A multi-target detector array will be discussed, which is under development at MTA Atomki, consisting of position sensitive gas detector modules based on the state-of-the-art THGEM technology. For the measurement of the mass and atomic number distribution of the fission fragments a highly-efficient, five-folded, Frisch-gridded twin-ionization chamber (used as Bragg ionization chamber), which is also under development at Atomki, will be discussed. The chamber will be equipped with double-sided Si strip detectors in order to measure light particle emission probability from the highly-deformed compound state and to detect ternary particles from fission. Atomic numbers will be extracted by tracking the range of the fragments using fast digitizers and advanced digital signal processing (DSP) techniques.
Dátum: január 8.
Előadó: Ughy Bettina
Előadás címe: Exploration of molecular biological effect of laser driven ionizing radiations
Understanding of the biological effect of laser driven ionizing radiation is essential for safe and effective therapies. Comparison of the molecular biological effect of laser accelerated ionizing beams to that resulted in using conventional photon and electron is highly important. Investigations in the radiation sciences mainly concentrated on the identification and quantification of types of DNA damage induced by radiation. Nowadays there are increasing interest for development of personalized therapies that are based on the combination of molecular targeted therapy and radiotherapy, which needs deeper understanding of the molecular effect of ionization radiations. Reactive oxygen species (ROS) act as a second messenger in cell signalling and are essential for various biological processes in normal cells. In the case of redox imbalance ROS could be involved in cancer development. On the other hand ionizing radiation induces the formation of free radicals and ROS that could trigger cell death and this way could be used for killing cancerous cells. Because of the double-edged sword property of ROS understanding of ROS production and the related molecular mechanisms is extremely important.
Dátum: október 30.
Előadó: Subhendu Kahaly
Előadás címe: Attosecond Light Sources using Plasma Optics
State of the art high-power femtosecond lasers have allowed us to achieve light induced coherent control of relativistic matter1, thus opening novel vistas for basic sciences, as well as for scientific and societal applications. The usual trend in this research field has been to attain the highest possible laser intensities on target, by focusing Fourier-Transform Limited ultrashort laser pulses up to their diffraction limit. Such focussed ultrashort intense light can transform any solid surface into an instantly ionised plasma reflector. This type of exotic plasma optics can operate at ultra-high intensities making them extremely attractive and also the only optics available at such high light fields.
We demonstrate that they can act as tuneable reflective2 or diffractive3 elements which can be controlled for surface sharpness2, shape1,4, structure3,5,6 and can be driven over ultrafast timescales to relativistic motion in phase with the driving laser field1,2. The last property lets it also act as a coherent XUV light emitter7 having tremendous potential as an isolated attosecond light source8 for further scientific applications9.
In this presentation I would introduce different exciting schemes to accomplish plasma optics at high intensity and control their various properties that we developed over time1,2,3. In continuation, I would be providing several examples to show that shaping the laser field in space can lead to novel and far-reaching physical effects. Finally I would summarise few of our recent examples to show how these properties permit one innovative applications which are not possible otherwise10.
1. H. Vincenti et.al “Optical properties of relativistic plasma mirrors”, Nature Communications 5, 3403 (2014)
2. S. Kahaly et al. “Direct observation of density-gradient effects in harmonic generation from plasma mirrors”, Phys. Rev. Lett. 110, 175001 (2013)
3. S. Monchoce et al. “Optically controlled solid-density transient plasma gratings”, Phys. Rev. Lett. 112, 145008 (2014)
4. Nakatsutsumi, M. et al. “Fast focusing of short-pulse lasers by innovative plasma optics toward extreme intensity”, Opt. Lett. 35, 2314 (2010).
5. S. Kahaly et al. “Near-complete absorption of intense, ultrashort laser light by sub-λ gratings”, Phys. Rev. Lett. 101, 145001 (2008)
6. M. A. Purvis et al. “Relativistic plasma nanophotonics for ultrahigh energy density physics”, Nature Photonics 7, 796 (2013)
7. C. Thaury and F. Quere “High-order harmonic and attosecond pulse generation on plasma mirrors: basic mechanisms”, J. Phys. B. 43, 213001 (2010)
8. Jonathan A. Wheeler et.al. “Attosecond lighthouses from plasma mirrors”, Nature Photonics 6, 829–833 (2012)
9. Maurizio Reduzzi et.al. “Advances in high-order harmonic generation sources for time-resolved investigations”, Journal of Electron Spectroscopy and Related Phenomena, Review article in press, (2015)
10. A. Leblanc et.al. “Ptychographic measurements of ultrahigh-intensity laser-plasma interactions” Nature Physics, article in press (2015).
Dátum: október 9.
Előadó: Hideghéty Katalin
Előadás címe: Potential application of laser driven ionizing radiation in radiation oncology- radiobiology experiments
There are growing evidence word wide with hadron therapy of more then 100.000 patients on the superiority of charged particle treatment over conventional photon irradiation, due to its physical characteristics represented by the Bragg peak of the depth dose curve. The consequent high physical selectivity of the dose delivery allows dose escalation in the tumours without increasing the risk of late complication in the surrounding tissues. Furthermore the biological effectivity of certain charged particles could be 4 times higher then the photon beam. Therefore the patients suffering from well circumscribed locally growing tumors with radiosensitive tissues around could have a benefit from charged particle therapy (CPT). The clinical experiences with CPT of eye-, skull base-, CNS-, childhood tumors, prostate carcinoma, breast-, lung-, head and neck malignancies will be briefly summarized. The planned laser-driven ionizing beams at ELI-ALPS have the unique property of ultra-short ion pulses, and high repetion rate which may introduce a new approach in the radiation therapy. Toward the development of laser accelerated particle therapy for the clinic, intensive experimental research on the biological effect of laser driven CPT is essential. An onverview will be provided on the published results of preclinical radiobiology investigations on laser accelerated paricles and on the planned biological experiments at ELI-ALPS. The actual research of our group on special dosimetry and development of appropriate models (tissue cultures of various tumor cells, wild type and transgenis zebrafish embryos, small animals) and methods (detection of survival, functional-, analytic-, cellular-, subcellular- and molecular changes) for comparison of the effect of laser accelerated ionizing beams to that resulted in using conventional photon and electron beams will be presented.
Dátum: október 2.
Előadó: Porosz Péter - Elsevier
Előadás címe: Fact-based Research Management at ELI-ALPS: an Elsevier Workshop
Today's R&D landscape requires research managers to devise better ways to measure the quality and impact of their institution's research projects. Working with leading research institutions worldwide, Elsevier aims to provide solutions and support the development of research projects at ELI-ALPS.
Elsevier provides research intelligence thorugh Scopus and SciVal, both of which are quickly becoming the accepted global standards by which research programs are planned and evaluated and the result are showcased.
Scopus is the largest abstract and citation database of peer-reviewed literature: scientific journals, books and conference proceedings. Delivering a comprehensive overview of the world's research output in the fields of science, technology, medicine, social sciences, and arts and humanities, Scopus features smart tools to track, analyze and visualize research.
SciVal offers quick, easy access to the research performance of 5,500 research institutions and 220 nations worldwide. A ready-to-use solution with unparalleled power and flexibility, SciVal enables you to visualise research performance, benchmark relative to peers, develop collaborative partnerships and analyze research trends.
In this workshop, we will explore how Elsevier research intelligence can support ELI-ALPS, so that the program can reach its maximal research potential.
Dátum: szeptember 18.
Előadó: Carlo Callegari - Italian Free Electron Laser FERMI, Trieste
Előadás címe: The Low Density Matter beamline at the Italian Free Electron Laser FERMI
In this talk the current status and recent results of the Low Density Matter (LDM) beamline at the FERMI Free Electron Laser in Trieste, Italy will be presented.
Free Electron Lasers fulfill the need for soft and hard X-ray radiation with extremely high brilliance, a high degree of (transverse and longitudinal) coherence, and duration in the femtosecond time domain. FERMI covers the spectral range from 100 down to 4 nm and has been designed as a Users’ facility providing stable operation, high spectral purity, full tunability, variable polarization, and low timing jitter. Since the beginning of Users’ operation in December 2012, FERMI has received ~200 proposals, and allocated ~1/3 of them. Three beamlines are open to users (Diffraction and Projection Imaging; Elastic and Inelastic Scattering-TIMEX; Low Density Matter) and three more are scheduled to open in 2016.
The LDM beamline caters to the atomic-, molecular-, and cluster-physics community, offering an endstation for photoelectron, photoion, and photon-scattering spectroscopy of supersonic jets (notably, of helium droplets, which can be used to transport and cool large molecules). Beyond its standard spectrometers (Velocity Map Imaging; ion Time of Flight; photon scattering) the end-station has accommodated user-supplied instruments, for Users’ experiments as well as FERMI characterization experiments.
Dátum: szeptember 9.
Előadó: Virginijus Barzda - Chemical and Physical Sciences, University of Toronto
Előadás címe: Nonlinear Microscopy and Applications for Biological Imaging
Advanced optical microscopy is experiencing a renaissance by breaking the diffraction limit of spatial resolution, providing imaging at video frame rates and achieving deep tissue imaging. Significant advancements in microscopy are realized by employing nonlinear light-matter interactions. Many biological structures, when exposed to high intensity femtosecond laser radiation, exhibit harmonic generation effects, and hence, do not require labeling with dyes that can potentially disrupt the functionality of the system. The harmonic imaging is free of photobleaching and carries structural information beyond diffraction limited resolution. Laser scanning harmonic generation microscopy is a versatile imaging technique which can be used to visualize nanostructures, interfaces between materials and ordered biological aggregates. The use of nonlinear microscopy for structural investigations of protein assemblies in cells and biological tissue will be overviewed, and examples of imaging applications in plant biology, tissue pathology in cancer diagnostics, and study of muscle contraction dynamics will be presented.
Dátum: július 17.
Előadó: Pankotai Tibor - SZTE TTIK Biokémiai és Molekuláris Biológiai Tanszék
Előadás címe: Beyond the DNA damages: DNA error types, repairs and diseases
At recent days the understanding of cancer development and progression is one of the highest challenge for the medical sciences. The cases of cancerous malformations show increasing tendency and they affect a huge number of populations. For example, over 30 million new patients were documented in 2013, which means one person is affected out of 200 people all around the world. During cancer development one of the earliest steps is the failure of the DNA repair pathways. If the DNA repair does not function properly or the rate of DNA damage exceeds the repair capacity of the cell, the accumulation of errors can overwhelm the cells, which is resulted in early senescence, apoptosis, or cancer. Until now, mutations of 40 different proteins, involved in different DNA repair pathways, have been reported to increase the rate of cancer formation.
In my talk, I will focus on the introduction of DNA damaging agents and sources, types of DNA damages and cancer hallmarks affected by proteins involved in DNA repair pathways. Additionally, I will give an overview how we could study the course of action of electromagnetic waves surrounding our life (ionizing radiations, microwaves, ultraviolet light, radio waves) by using short pulse laser.
Dátum: július 10.
Előadó: Várallyay Zoltán
Előadás címe: Fiber lasers and amplifiers
We briefly review the operation and types of optical fibers. Nonlinear and dispersive pulse propagations in optical fibers are discussed which both can be advantageous or disadvantageous for some applications. Keeping in mind these properties and using rear-earth doped optical fibers one can build fiber lasers which regarding the arrangement and basic operation of them are very similar to solid state lasers however they are considered environmentally more stable and financially more rewarding. The question is whether we can reach similar power levels and similar short pulse widths (few-cycle femtosecond laser pulses) from these fiber light sources? The presentation is aiming to show recent efforts reaching these goals which seem to be successful since the High Repetition Rate laser system which are going to be built for the Extreme Light Infrastructure - Attosecond Light Pulse Source (ELI-ALPS) in Hungary is based on this technology.
Dátum: június 19.
Előadó: Subhendu Kahaly
Előadás címe: Recording Real Time “µm-fs” Movies Inside Laser Generated Extreme Plasmas
Visible matter predominantly exists in the form of plasma, be it in the interior of the stars, magnetically confined devices or intense laser generated. Laser induced plasmas can be extremely dense (ne ~ 1017-1025 cm-3), hot (Te ~ 0.1-100 keV) and short-lived (~ fs-ns). The laser produced laboratory plasmas can be over-dense (Solid Plasma Mirrors1 or special Gas-jets2) or under-dense (Gas-jets) and are home to world’s largest magnetic fields, smallest particle accelerators and tiniest sources of the shortest known attosecond XUV pulses. They also form test-beds for studying laboratory astrophysics and exotic plasma science.
In this seminar I would discuss how astrophysical conditions3,4,5 can be recreated inside the laboratory elucidating the metrology schemes that lets us probe these systems. I would present a glimpse of how space-time resolved movies in µm-fs domain can unravel rich dynamics of electrons in relativistic laser plasma accelerators4,5.
1. H. Vincenti, S. Monchocé, S. Kahaly, Ph. Martin and F. Quéré “Optical properties of relativistic plasma mirrors” - Nature Communications 5, 3403 (2014)
2. F. Sylla, M. Veltcheva, S. Kahaly, A. Flacco and V. Malka “Development and characterizarion of very dense submillemetric gas jets for laser plasma interaction” - Review of Scientific Instruments 83, 033507 (2012)
3. F. Sylla, A. Flacco, S. Kahaly, M. Veltcheva, E. d’Humières, I. Andriyash, V. Tikhonchuk and V. Malka “Short intense laser pulse collapse in near-critical plasma ” - Physical review letters 110, 085001 (2013)
4. S. Kahaly, S. Mondal, G. Ravindra Kumar, S. Sengupta, A. Das and P.K. Kaw “Polarimetric detection of laser induced ultrashort magnetic pulses in overdense plasma” - Physics of Plasmas 16, 043114 (2009)
5. A. Flacco, J. Vieira, A. Lifschitz, F. Sylla, S. Kahaly, M. Veltcheva, L. O. Silva and V. Malka “Persistence of magnetic driven by relativistic electrons in a plasma” - Nature Physics 11, 409-413 (2015)
Dátum: június 12.
Előadó: Kecskés Tamara
Előadás címe: Safety System of ELI-ALPS
The active, passive elements of the radiation protection system, protocols and the personnel safety system of ELI-ALPS will be described in this presentation detailed.
Laser safety includes the safe design, use and implementation of lasers to minimize the risk of laser accidents, especially those involving eye injuries. Radiation protection aims at reducing human exposure to radiation through the proper management and disposal of all radioactive materials utilized in research activities. In both cases - radiation protection and laser safety - policies and procedures will assist in the safe handling of radioactive materials.
During the implementation and operation phases the Safety and Security Group is responsible for providing and maintaining safe and healthy working conditions, equipment and systems of work for its staff, together with effective management of health and safety risks including effective information, instruction, training and supervision. In accordance with national law and legislation our group is responsible for the health, safety and welfare of all employees and for the health and safety of users/visitors to ELI-ALPS sites and others who may be affected by ELI-ALPS’s activities. The responsible and professional management of arising hazards (laser, radiation, biological, chemical, electrical, etc.) makes the ELI-ALPS a safe place to work for staff, contractors, visitors and facility users. The safety professionals of the group are responsible for ensuring that there are simple and effective safety systems for managers and staff to employ - maintaining and/or improving safety performance.
Dátum: május 22.
Előadó: Czirják Attila
Előadás címe: Optical tunneling and quantum entanglement
Optical tunneling  has a fundamental role in attosecond physics : a sufficiently strong low frequency laser pulse enables an electron to tunnel out from its atomic bound state into the continuum, which is the first step of the very successful three-step model  underlying our understanding of HHG . Recent progress in experimental techniques opened the possibility of measuring quantum processes with attosecond time resolution . This new quantum metrology demands more theoretical knowledge about fundamental features of tunneling , e.g. tunneling time and exit momentum.
The above fundamental process also creates an entangled pair of quantum particles, which opens the possibility to control the pair entanglement by the features of the generating laser pulse .
We address the above problems by simulating a hydrogen atom interacting with a linearly polarized few-cycle laser pulse in 3 spatial dimensions, and we compare our new results with earlier works based on different 1D atomic model potentials [8, 9], using quantum phase space methods [8-10].
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Dátum: május 15.
Előadó: Groma Géza, MTA Szegedi Biológiai Kutatóközpont, Biofizikai Intézet
Előadás címe: Ultrafast spectroscopy on bacteriorhodopsin and coenzymes
Bacteriorhodopsin – the single protein in the purple membrane of Halobacterium salinarum – utilizes light energy for building proton gradient across the membrane. The electrochemical potential created by this way is then used by ATPases for the synthesis of ATP molecule. The first part of my talk will focus on the characterization of the early processes of the energy transduction by femtosecond spectroscopy. We found that the purple membranes can be macroscopically oriented, leading to a non-centrosymmetric sample of high second-order susceptibility. The corresponding resonant optical rectification process is observable in the form of coherent emission in the mid-infrared and THz region. Monitoring these radiations makes possible to follow the time evolution of the light-induced intramolecular electron translocation in the retinal chromophore, as well as that of the accompanying coherent nuclear vibrations and the subsequent early proton transport processes. In the second part of my talk I will outline the capabilities of our laboratory for measuring and analysing time-resolved fluorescence kinetics in the 100 fs – 10 ns time range, and show our results in the characterization of the different conformational states of coenzymes FAD and NADH.
Dátum: május 14.
Előadó: Eleftherios Goulielmakis, Max-Planck-Institut für Quantenoptik, Garching, Németország
Előadás címe: Attosecond Physics in the Condensed Phase: From the Bloch Oscillator to Electronic Dephasing in Solids
With the fastest optical1,2,3 and soft x-ray fields4 as a part of its repertoire, attosecond physics has opened up new avenues for exploring ultrafast electronic processes in atoms5,6, molecules7, surfaces8 or nanostructures9. I will discuss how recent efforts towards advancement of the toolbox of attosecond science allow, for the first time, the exploration and control of fundamental electronic phenomena in condensed matter. Electron motion in bulk media, driven by intense, precise-sculpted, optical fields gives rise to controllable electric currents, the frequency of which extends to the multi-ten-Petahertz range9, advancing lightwave electronics10 to new realms of speed and precision. Coherent extreme ultraviolet radiation emerging in these coherent charge oscillations9 offers direct insight into structural and dynamical properties of the underlying medium, previously inaccessible to conventional solid-state spectroscopies. By endowing essential x-ray spectroscopies of solids with attosecond temporal resolution, optical half-optical cycle fields, combined with extreme ultraviolet pulses, offer, for the first time, access into the attosecond dephasing of electronic excitation of highly-correlated, condensed phase electronic systems11. We anticipate these new capabilities to result in far reaching implications to fundamental and applied, electronic and photonic sciences.
 Goulielmakis E. et al., Science 305, 1267 (2004)  Wirth A. et al., Science 334, 195 (2011).  Hassan M. Th et al., Nature submitted ( 2014)  Goulielmakis E.et al., Science 320, 1614 (2008). Goulielmakis E. et al., Nature 466, 739 (2010).  Kienberger R. et al., Nature 427, 817 (2004) , Smirnova et. al, Nature 460,972(2009)  Cavalieri A L et al., Nature 449,1029 (2007) Krueger M et al. Nature 475,78 (2011)  Luu T.T. et al., Nature Submitted (2014).  Goulielmakis E. et al., Science 317, 769 (2007).  Moulet A. et al., in preparation (2014).
Dátum: május 8.
Előadó: Sergei Kühn
Előadás címe: Surface excitons on ZnO
Most semiconductors with a direct band gap exhibit strong excitonic features in their optical absorption and photoluminescence spectra. Excitons, which are correlated electron-hole pairs, can exists as freely moving or localized quasiparticles. The energetic position and shape of their excitonic resonances hold clues about the specific type of the exciton and its nanoscopic environment.
Zinc oxide (ZnO) has received much attention because its wide bandgap (3.5 eV) and high exciton binding energy (60 meV) make it a promising candidate for short-wavelength optoelectronic applications. The study of ZnO nanostructures revealed a strong signature of excitons that are localized near the semiconductors surface, the so-called surface exciton (SX). We investigate the SX on a single-crystalline ZnO surface using a high-resolution near-field scanning optical microscope (NSOM) at a temperature of 4 K. The results are discussed in terms of the physics and technological applications of hybrid materials that consist of an inorganic and an organic semiconductor material.
In the second part of the seminar I will briefly report about my recent secondment to FORTH-IESL, the developer’s site of the GHHG user beam line driven by the Sylos laser at ELI-ALPS.
Dátum: április 24.
Előadó: Szász Péter
Előadás címe: Scientific Computing at ELI-ALPS
The Scientific Computing Group (a.k.a. SciComp) is part of the Scientific Engineering Division of ELI-ALPS with various responsibilities. On the one hand SciComp takes its part in the construction of the ELI-ALPS by defining and developing the scientific computing aspects of the future user facility, on the other hand provides services and support in the current phase for the scientist and researcher colleagues in connection with scientific software and scientific programming tasks.
We will present the current state of each area. As part of the presentation we go through the list of the available software licences and open source tools and also present examples of collaboration between SciComp and researcher teams.
Dátum: április 17.
Előadó: Pocsai Mihály, HHAS Wigner Research Centre of Physics, Dept. of High-energy Physics
Előadás címe: Electron Acceleration by a Chirped Laser Pulse in Underdense Plasmas
An effective theory of laser–plasma based particle acceleration is presented. Here we treated the plasma as a continuous medium with an index of refraction nm in which a single electron propagates. Because of the simplicity of this model, we did not need to perform PIC simulations in order to study the properties of the electron acceleration. We studied the properties of the electron motion due to the Lorentz force and the relativistic equations of motion were numerically solved and analysed. We compared our results to PIC simulations and experimental data. As a recent feature, we improved our model for bichromatic laser fields.
Dátum: április 17.
Előadó: Barna Imre
Előadás címe: Laser Assisted Proton Collision on Light Nuclei at Moderate Energies
We present analytic angular differential cross section model for laser assisted proton nucleon scattering on a Woods-Saxon optical potential where the nth-order photon absorption is taken into account simultaneously. As a physical example we calculate cross sections for proton-12C collision at 49 MeV in the laboratory frame where the laser intensity is in the range of 107-1021 W/cm2 at optical frequencies. The upper intensity limit is slightly below the relativistic regime. As a recent feature we perform calculations for bichromatic laser fields as well.
Dátum: április 10.
Előadó: Börzsönyi Ádám
Előadás címe: Enhancement and shaping of the amplification bandwidth in OPA through implementation of multibeam pumping
Within the frame of ELI-ALPS laser R&D projects, I visited the Vilnius Universtity Laser Research Center (VU LRC), where the sub-task NLO 3.5 is being implemented. My talk will summarize the progress of this research project. Coherent and incoherent combining is a relatively widely used approach by developers of semiconductor or fiber lasers trying to obtain higher radiation brightness or simply power total power from the aforementioned light sources. On the other hand, the technique of coherent combining has not gained a broad recognition in nonlinear optics yet. An example of coherent combining is multibeam pumped optical parametric amplification which is a method of energy transfer to a single signal beam from more than one pump sources. VU LRC pioneered experiments on multibeam pumping starting from early applications to nanosecond optical parametric oscillators and continuing on various different setups, including amplification of broadband chirped pulses. The planned research is aimed at the generation of broadband chirped laser pulses in the infrared (IR) region above 2 um wavelength and its further parametric amplification by utilizing two pump beams with the emphasis on enhancement and shaping of the signal spectrum.
Dátum: április 10.
Előadó: Bohus János
Előadás címe: Report on development of a thin disk Yb:YAG regenerative amplifier for pumping OPCPA systems
Yb:YAG as a laser gain material has the advantage of very high quantum efficiency (~91%) therefore low heat generation when pumped with diodes at 940nm, high absorption bandwidth (~10nm), therefore low requirements at the pump diodes, high heat conduction and stress resistance, long upper state lifetime (~1ms) and high emission bandwidth (~6nm). Disk lasers are ideally suited for large average powers as well as high peak powers combined with high beam quality at low demand on pump diode brightness. The seminar reports on progress of development of a thin disk amplifier at TRUMPF Scientific Lasers.
Dátum: március 27.
Előadó: Nicholas Matlis, Lawrence Berkeley National Laboratory, Acceleration and Fusion Research Division
Előadás címe: Micromanaging laser-plasma interactions for fast accelerator science
Laser plasma accelerators (LPAs) hold great promise as ultra-compact electron sources because of their high acceleration gradients (~GeV/cm) and flexible format, but have yet to gain wide-spread acceptance due to limitations in their tunability and stability. These limitations, caused by the fluid nature of the accelerator formation, have required the development of sophisticated new techniques tailored to manage the microscopic dynamics of the laser-plasma interaction. This talk will highlight recent work aimed at addressing the unique control challenges of this accelerator format, including the use of multiple-pulse collisions to trigger electron injection, the use of tomography to see through walls, the use of spectroscopic imaging to track gas-plume and laser evolution and the use of chirped-pulse interferometry to resolve wake-induced Raman shifts. These methods provide a tremendous wealth of in-situ, shot-by-shot information from within the accelerator, enabling control of and shining new light on what has previously been a black box accessible primarily by simulation.
Dátum: február 23.
Előadó: Luca Volpe, CLPU, Salamanca
Előadás címe: The Salamanca project
Dátum: február 13.
Előadó: Börzsönyi Ádám
Előadás címe: Linear interferometric tools for ultrafast pulse diagnostics
Spatiotemporal compression of ultrashort pulses is one of the key issues of chirped pulse amplification (CPA), the most common method to achieve high intensity laser beams. Successful shaping of the temporal envelope and recombination of the spectral components of the broadband pulses need careful alignment of the stretcher-compressor stages. Several diagnostic techniques have been developed so far for the characterization of ultrashort pulses. Some of these methods utilize nonlinear optical processes, while others based on purely linear optics, in most cases, combined with spectrally resolving device.
In this seminar I provide a review on the capabilities and limitations of the latter category of the ultrafast diagnostic methods. I give a general description on the background of spectrally resolved linear interferometry and demonstrate various schematic experimental layouts for the detection of material dispersion, angular dispersion and carrier-envelope phase drift. Precision estimations and discussion of potential applications are also provided.
Dátum: február 4.
Előadó: Wolfgang Sandner, ELI-DC
Előadás címe: Future perspective of ELI
Dátum: január 30.
Előadó: Lengyel Krisztián, Wigner Fizikai Kutatóközpont Szilárdtestfizikai és Optikai Intézet
Előadás címe: Crystals and lasers
One of the great scientific projects nowadays is the ELI with many possibilities for laser physics experiments in the future. The operation of devices in these plans is usually based on an optical crystal. In this lecture the growth, preparation and qualification of non-linear optical crystals produced in the Crystalphysics Group of Wigner Research Centre and having important laser applications will be shown. First, three kinds of growth methods and different technics to investigate the composition and homogeneity of bulk crystals will be described. Specific requirements of applications, in particular acousto-optic modulator, harmonic generation and THz generation, will be discussed together with their consequencies for crystal growth and preparation.
Dátum: jaruár 23.
Előadó: Varró Sándor
Előadás címe: Notes on the notion and description of phase in quantum optics
We discuss the old problem of the quantum phase of an oscillator, which may represent for instance the phase of a quantized mode of the radiation field. After reviewing the main approaches have so far been applied to solve this problem, we shall offer a new solution. Our method is based on a new ‘polar decomposition’ of the quantum amplitude of the field components. With the help of this decomposition we have defined an analogon of the quantum saw-tooth phase operator . In the frame of the present approach a generalized spectral decomposition of the phase operator and projectors can be derived in a natural way, and they can be expressed by dyads of SU(1,1) coherent states . Besides, we have found that these new sampling states (generalized projectors) for phase measurements can be generated by an experimentally realizable nonlinear interaction whose coupling strength depends on the intensity. The possible extension of our method to a multimode description may be useful in studying the quantum phase properties of extreme radiation fields, like few–cycle or attosecond light pulses.
Dátum: január 16.
Előadó: Brockhauser Sándor
Előadás címe: The Scientific Engineering Division
The Scientific Engineering Division (SED) is responsible for providing engineering and technician support for in-house and external researchers as well as user groups during the implementation and operation phases of ELI-ALPS research facility. The long term goal is to built safely and robustly usable beamlines which will offer possibilities to be carried out unique scientific experiments. In the implementation phase, SED has responsibilities like following the building construction, design Beam Transport system parts, following LaSo/SeSo procurements with providing engineering support, working on the integration of LaSo-s, SeSo-s and End Stations, elaborating the Personal Safety System and other safety rules, establish the electrical, mechanical and optical workshops. In the operational phase SED will provide engineering support for each experiment such as preparatory discussions and design with user groups, manufacturing of unique items or installation of experiments.
Dátum: január 9.
Előadó: Ashutosh Sharma
Előadás címe: Laser ion acceleration in plasmas
Laser acceleration of ions from both solid and gaseous target attracts a great attention because of its potential medical applications including the hadron therapy. The recent development of ELI-ALPS facility which will host the laser system capable of generating ultra-short pulses in the multiterawatt or even petawatt power range at high repetition rate, which is crucial for the investigation of new regimes of laser-matter interactions, especially laser proton acceleration. The most stable and well understood mechanism is the TNSA (Target Normal Sheath Acceleration), which usually requires long pulse duration in order to reach high cut-off energy. Since at ELI-ALPS the short pulses are in the center of interest, we have to consider different mechanisms, where the RPDA (Radiation Pressure Dominant Acceleration) is the driving process. The schemes of interest are the collision-less Shock Wave Acceleration and Magnetic Vortex Ion Acceleration, which is more efficient in near-critical density plasma.
Dátum: december 5.
Előadó: Chikán Viktor, Kansas State University, Dept. of Chemistry
Előadás címe: Building a Better Nanoparticle
Semiconductor quantum dots exhibit fascinating and important physical and chemical properties that can hold the potential to play crucial role in transforming the photovoltaic industry, creating new business opportunities and producing electricity to address the increasing global energy needs. Producing relatively efficient solar cells from quantum dots has been already demonstrated by many research groups. An important goal is to better equip these quantum dots for photovoltaic cells by controlling their electrical properties via chemical doping. Prof. Chikan research focuses on the synthesis and optical characterization of colloidal nanoparticles. The research talk will address the challenge of doping of colloidal semiconductor particles for the purpose of improving electrical properties of these particles! Prof. Chikan has an expertise on wide variety of spectroscopic techniques (terahertz, ultrafast laser experiments, and single particle fluorescence spectroscopy) to characterize extrinsic and intrinsic defects formation in colloidal doped CdSe quantum dots and nanorod structures.
Dátum: november 28.
Előadó: Drozdy András
Előadás címe: Fully fiber integrated all-normal dispersion ring oscillator
Passively mode-locked fiber oscillators are widely used sources where ultrashort pulses are required like in applications such as micromachining, nonlinear microscopy, terahertz optics. Although some setups are reported where the laser cavity contains only polarization maintaining (PM) components to improve environmental stability, non-PM setups are still popular as the required parts are less expensive and the achievable pulse duration can be shorter. For self starting and for stable operation all of the non-PM setups need to include polarization controllers otherwise the setups won't start, or can run in unwanted operation regimes such as CW, noise-like or Q-switched. Although in-line polarization controllers are commercially available, not many setups are reported where these components are used for stabilization [1,2,3,4].
At FETI (Furukawa Electric Technology Institute) such a fully fiber integrated all-normal dispersion Yb based fiber oscillator has been built. This presentation is about the oscillator scheme and the experimental characterization of the operating regimes of such a fiber laser oscillator. An attempt to stabilize the operation of the system with the use of an active feedback system is also discussed.
Dátum: november 21.
Előadó: Barna Imre
Előadás címe: Contribution of the Wigner Research Centre to the CERN AWAKE Proton Wake Field Acceleration Experiment
In our talk we outline the idea of the planned CERN AWAKE experiment which will be similar to the planned ELI particle accelarator experiments. We explain the experimental and theoretical contributions of the Wigner Research Institute which are important for AWAKE. In the end we briefly mention our future plans.
Dátum: november 14.
Előadó: Fülöp Lajos
Előadás címe: The first prototype of the Integrated Control System
The first prototype of the integrated control system includes hundreds of very simple simulated devices of four laser sources and four secondary sources, which run in a distributed environment. The prototype also provides operator user interfaces to these beamlines. The prototype is based on the TANGO Controls framework that provides the communication interface, the device configuration database and several toolkits for the rapid development of device drivers, user interfaces and other components. The major goal of the prototype is to clarify the requirements and the architecture.
Dátum: november 11.
Előadó: Farkas Balázs
Előadás címe: Imaging of high harmonic focal spot (Secondment to Lund from 13 July to 30 August)
In this talk the high intensity HHG beamline at Lund Laser Center and first results of XUV spot size imaging will be presented.
Dátum: október 31.
Előadó: Vladimir Chvykov
Előadás címe: Development of Petawatt-class CPA laser at the University of Michigan (Solution of several bottleneck problems)
SThe 0.3-PW short pulse solid-state laser system was developed and investigated in University of Michigan. The world record laser intensity of 2⋅10²² Watt/cm² and the temporal contrast of the record value 1015 were reached. Several new methods for solving bottleneck problems of the CPA lasers were suggested and implemented during the laser construction. Most of them will be presented in this report, among them:
• The method for increasing extracted energy from multipass amplifiers. Method was successfully applied in the other laboratories and allowed to achieve the record output power 2 PW .
• New optical system for improvement of temporal contrast up to the record value of 1011.
• New method for the alignment of the Petawatt compressor with 10-6 rad accuracy.
• First demonstrated the compression of 30 TW laser pulses from 30 down to 14 fs via spectral broadening by self-phase modulation.
Dátum: október 17.
Előadó: Papp Dániel
Előadás címe: Laser Polarimetry of High Energy Density Plasmas
Current High Energy Density Plasma Research focuses on several fields, like Inertial Confinement Fusion, properties of Materials under Extreme Conditions, Laboratory Astrophysics, and novel laser-driven photon/particle sources. Proper diagnostics of these plasmas are crucial to understand physical processes and to benchmark numerical codes. Laser probing is widely available, offers good spatial and temporal resolution, and is one of the few methods that can be used to determine magnetic fields present in such plasmas. I will introduce the physics behind laser probing, discuss the methods it can be used (shadowgraphy, interferometry, polarimetry). Two applications of these principles will be presented. The first would be z-pinch generated plasmas probed by ns lasers to determine current distribution within the z-pinch. The second application would be the probing of fs laser-generated plasmas to determine the temporal evolution of the self-generated magnetic field. Z-pinch experiments were conducted at Nevada Terawatt Facility, Reno, NV, USA. Ultrafast laser experiments were conducted at CELIA, Bordeaux, France.
Dátum: október 10.
Előadó: Tóth Zoltán
Előadás címe: Mechanical engineering
Mirror mount design, Beamline node design, Polarization rotator equipment design
Dátum: október 3.
Előadó: Lécz Zsolt
Előadás címe: Possible laser-driven proton acceleration mechanisms at the ELI-ALPS, Hungary
Laser acceleration of ions from both solid and gaseous target attracts a great attention because of its potential usage in many scientific and medical applications, including hadron therapy. The presentation consists of two parts: first a brief summary of the CERN School of Computing is given, and its relevance to the high performance computing at ELI-ALPS is discussed. Secondly several laser ion acceleration mechanisms in plasmas are presented, which could be realized with ultra-short laser pulses provided by the HF laser system of the future ELI-HU facility. The currently investigated Shock Wave Acceleration, driven by the radiation pressure of the laser pulse, is presented in more details. Particle in Cell simulations show promising results, which gives us the confidence for initiating experimental campaign, where this regime can be tested.
Dátum: szeptember 26.
Előadó: Luca Volpe
Előadás címe: Laser-driven fast electron transport in matter and/or plasmas. State of the art from experimental and theoretical point of view
When high power (> 1 TW) laser is focused on solid targets, the electrons of the target are accelerated to relativistic velocities. The laser-driven electron beam starts to travel into the target transporting and depositing part of the laser energy in the over-dense region of the target.
The electron dynamic into the target depends both on the collisions and on the electro-magnetic interactions. Electrons lose energy both by collisional and resistive stopping power and they change their divergence via inelastic scattering and magnetic field collimation.
The physics of fast electron transport has been studied intensively in the last two decades mainly connected to fast ignition (thick foils) and proton acceleration (thin foils) schemes.
Theoretically the process can be separated in two parts: i) the first (generation) describes the laser-matter interaction and electron generation by neglecting collisions (based on the integration of the Vlasov--Maxwell system i.e Particle in Cell Code), ii) the second (transport) describes the propagation of the relativistic beam in the target with collisions (based on the integration of the Fokker-Plank--Maxwell system i.e kinetic code).
An introduction of the topic will be presented with particular attention to the time fs regime which is relevant for ELI-ALPS. Numerical simulations by using the kinetic code M1 are shown.
Dátum: szeptember 19.
Előadó: Varró Sándor
Előadás címe: Electromagnetic wake-fields and rectangular waves, generated by strong laser fields on thin plasma layers or on graphene
The generation of broad-band radiation an short pulses relies on the highly nonlinear processes induced by the intense laser fields . Carrier-envelope phase difference effects  are also important concerning short pulses. In the present talk we show that the collective radiation back-reaction of (relativistic) surface currents driven by a laser field can cause extreme nonlinearities and a violent distortion in the scattered radiation. This phenomenon has already been considered by us, for the reflection of laser pulses on thin conducting (plasma) nano-layers [3-4], where the appearance of attosecond pulses and giant quasistatic wakefields has been predicted. We report also on new recent results [5-6], and discuss examples for the temporal behaviour of the reflected signals. In the case of graphene the reflected signal may contain only a radiation reaction term which is proportional with the velocity of the (convection) surface current, if the laser pulse impinges at Brewster angle on a graphene layer. The existence of such a reflected component cannot come out from the usual Fresnel formulae. Due to the ultrarelativistic kinematics of the electrons, the maximum signal is reached already at the rising part, and this ‘saturation’ causes a sort of ‘relativistic clipping’, which results in a rectangular temporal shape. These rectangular trains (approximating Rademacher functions) may perhaps serve as a clock signal being 100 000 times faster than a 10 gigahertz clock.
Dátum: szeptember 5.
Előadó: Mohamed Tarek
Előadás címe: Trapping of High Power Laser Pulses for Interaction with Low Density Targets
The design, construction and test of an optical storage devices for trapping a high power laser pulse will be presented in this talk. With the help of these devices, the repetition rate of the used high power laser system can reach the order of 100 MHz and the average power increases by a factor of 25. The aim of the optical devices is to increase the efficiency of using a high power laser pulse in different applications that need high laser repetition rate.