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In the first part we have shown that the four potential of electromagnetic fields in a plasma medium can be considered as a massive vector field, where the mass is proportional with the plasma frequency. The plane waves of this »Lánczos-Proca fields« have three orthogonal polarizatons, whose amplitudes satisfy the Klein-Gordon equation. The expression „Klein-Gordon radio” in the title of our talks has been borrowed from the paper by Crandall and Wheeler [1], devoted to the study on a dynamical bound of photon mass. These authors presented the peculiarities of wave propagation in free space, such as the appearance of wake-fields and the special Doppler effect of radio signals from a rapidly receding massy-photon transmitter. We have indicated that similar phenomena are also relevant in the so-called laser wake-field accelerators and in the generation of high harmonics (and attosecond pulses) in a plasma environment. In this second part of the presentation, on the basis of recently found new exact solutions of the relativistic wave equations of charged particles [2], we also show that very high contrast density modulations are generated, serving as »quantum bubbles« to accelerate electrons [3]. We also consider exact analytic solutions of the relativistic equation of motion of a point electron interacting with a high-intensity laser field in vacuum and in a plasma medium [4], and compare the particle dynamics and the radiation properties [5] in these two cases. 
 
References:
[1] Crandall R E, Wheeler N A, Klein-Gordon radio and the problem of photon mass. Nuovo Cim. 80B, 231 (1984).
[2] Varró S, New exact solutions of the Klein-Gordon and Dirac equations of a charged particle propagating in a strong laser field in an underdense plasma. Nucl. Instr. and Methods in Phys. Research A  740, 280-283 (2014).
[3] Varró S, Quantum description of relativistic charged particles interacting with a strong laser field in a plasma, represented by Lanczos-Proca vector bosons. Talk presented at EUCALL Joint Foresight Topical Workshop: Theory and Simulation of Photon-Matter Interactions [ELI-ALPS, 1-6 July 2018, Szeged, Hungary].
[4]Pocsai M A, Varró S and Barna I F, Electron acceleration in underdense plasmas described with a classical effective theory. Laser and Particle Beams 33, 307-313 (2015). E-print: arXiv: 1406.6310 [nucl-th].
[5] Hack Sz, Varró S and Czirják A, Carrier-envelope phase controlled isolated attosecond pulses in the nm wavelength range, based on coherent nonlinear Thomson backscattering. New J. Phys. 20, 073043 (2018).

Web of Science Core Collection is the largest editorially curated citation database.  During this presentation we will show, how Web of Science can help you identify discoveries and research useful to advance your own path to innovation and discovery. We will also show how you can optimize the use of Web of Science, Endnote, Kopernio and other tools available to experience a more efficient workflow, from reading to publishing papers.

In the present talk,  first we show that the four potential of electromagnetic fields in a plasma medium can be considered as a massive vector boson field, where the mass is proportional with the plasma frequency. Similar vector fields has long been known in quantum electrodynamics from the works of Lánczos [1] and Proca [2], but these do not rely on plasma considerations. The „mass-generation mechanism” has been described by Anderson [3] in solid state physics, and the research in particle physics on this subject has recently culminated in the detection of the Higgs particle [4].

The plane waves of the »Lánczos-Proca fields« have three orthogonal polarizatons, whose amplitudes satisfy the Klein-Gordon equation. The expression „Klein-Gordon radio” in the title of the present talk has been borrowed from the paper by Crandall and Wheeler [5], devoted to the study of a dynamical bound on photon mass. These authors presented the peculiarities of wave propagation in free space, such as the appearance of wake-fields and the special Doppler effect of radio signals from a rapidly receding massy-photon transmitter. We show that similar phenomena are also relevant in the so-called laser wake-field accelerators and in the generation of high harmonics (and attosecond pulses) by relativistic electrons, interacting with extremely high intensity laser fields in a plasma environment. On the basis of recently found new exact solutions of the relativistic wave equations of charged particles [6], we also show that very high contrast density modulations are generated, serving as »quantum bubbles« to accelerate electrons [7]. In the last part of the talk we consider exact analytic solutions of the relativistic equation of motion of a point electron interacting with a high-intensity laser field in vacuum [8] and in a plasma medium, and compare the particle dynamics (laser acceleration) and the radiation properties (attosecond light pulse generation) in these two cases. 

 

References.

[1] Lánczos C, Die tensoranalytischen Beziehungen der Diracschen Gleichung. Z. für Physik 57, 447 (1929).

[2] Proca A, Sur la théorie ondulatoire des électrons positifs et négatifs. J. Phys. Radium 7, 347-353 (1936).

[3] Anderson P W, Plasmons, gauge invariance, and mass. Phys. Rev. 130, 439-442 (1963).

[4] Higgs P W, Evading the Goldstone theorem. Ann. Phys. (Berlin) 526, 211-213 (2014). [Nobel Lecture, 8 December 2013.]

[5] Crandall R E, Wheeler N A, Klein-Gordon radio and the problem of photon mass. Nuovo Cim. 80B, 231-242 (1984).

[6] Varró S, New exact solutions of the Klein-Gordon and Dirac equations of a charged particle propagating in a strong laser field in an underdense plasma. Nucl. Instr. and Methods in Phys. Research A  740, 280-283 (2014).

[7] Varró S, Quantum description of relativistic charged particles interacting with a strong laser field in a plasma, represented by Lanczos-Proca vector bosons. Talk presented at EUCALL Joint Foresight Topical Workshop: Theory and Simulation of Photon-Matter Interactions [ELI-ALPS, 1-6 July 2018, Szeged, Hungary].

[8] Hack Sz, Varró S and Czirják A, Carrier-envelope phase controlled isolated attosecond pulses in the nm wavelength range, based on coherent nonlinear Thomson backscattering. New J. Phys. 20, 073043 (2018).

Have you ever wondered who writes the description on the wine label sold in supermarkets? If done by experts, they are called sommeliers. They are professional wine experts with wide range of knowledge about wine service and pairing it with food.

One of the hardest things is to master blind tasting. Blind tasting is when a person is served a glass of wine (or other alcohol) and his task is to describe its characteristics, like color, body, acidity, taste, smell etc. Depending on the difficulty of the tasting the person might be further requested to guess the grape variety, vintage, country of origin etc. of that wine based on the features he just described.

This sounds much like a machine learning task: based on a given description of wine characteristics decide what grape was used to produce the wine, in which country, what vintage etc.

The seminar will present a simple application of how data mining and simple supervised machine learning techniques can be applied to create a simple but still powerful code to guess the grape variety of which a bottle of wine was made from.

This work presents an analytic angular differential cross section formula for the electromagnetic radiation field-assisted electron scattering on impurities in semiconductors. These impurities are approximated with various model potentials. The scattered electrons are described with the well-known Volkov wave function, which has been used to describe strong laser field matter interaction for more than half a century, which exactly describes the interaction of the electron with the external oscillating field. These calculations show that the electron conductance in a semiconductor could be enhanced by an order of magnitude if an infrared electromagnetic field is present with 10^11 W/cm^2 < I <10^13 W/cm2^ intensity.

Reference: Imre Ferenc Barna, Mihály András Pocsai, and Sándor Varró, Eur. Phys. J. Appl. Phys. 84, 20101 (2018) https://www.kfki.hu/~barnai/semicond_barna_ApplPhys2018.pdf

SG-II facility consists of four sets of lasers, including the nanosecond, picosecond and femtosecond duration pulses. Researchers can conduct varies physical experiments, such as Inertial Confinement Fusion, laboratory astrophysics and particle acceleration. In the first part of the presentation, we mainly describe our experiments conducted on the SGII facility. It includes the study of suprathermal electrons produced by laser-plasma instabilities, the evolution of filaments and associated magnetic fields produced by Weibel instability in two counterstreaming laser plasmas and proton imaging by the picosecond petawatt laser pulse. In the second part, we will describe our target chamber size and the current diagnostics at the facility, which will help external research teams carry out experiments.

Refractive lenses cannot be applied to short-wavelength region by their inherent strong absorption. Relatively, diffractive optical element (DOE) can be used for EUV and soft X-ray focusing and imaging. As a representative of classical DOE, photon sieve derived from the traditional Fresnel zone plate was first proposed in 2001. Furthermore, it can achieve higher resolution on the same component scale. Compared with the monofocal photon sieve, we proposed Greek-ladder sieves to generate three-dimensional array diffraction-limited foci in 2015. Based on Greek-ladder sieve, we here give a brief overview of our recent research on the phase-shifting X-ray digital holography, multiplanar imaging with different point spread functions and phase-contrast imaging, and do some exploration and research on the meter-scale wavefront measurement.

As the major pioneer devoted to high-power laser technology and inertial confinement fusion (ICF) research in China, the National Laboratory on High Power Laser and Physics (NLHPLP) in Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences has established a multifunctional high power laser experimental platform, which can provide important experimental capabilities by combining different pulse widths of nanosecond, picosecond, and femtosecond scales. We will introduce this multifunctional experimental platform, including the SG-II laser facility, SG-II 9th beam, SG-II upgrade (SG-II UP) facility, and SG-II 5 PW facility, and present the key technologies for the eight-beam nanosecond laser system, the picosecond petawatt system, and femtosecond multi-petawatt system, which have been developed to ensure the performance of the facilities. The multifunctional high power laser experimental platform at NLHPLP is operational and available for interested scientists studying ICF and a broad range of high-energy-density physics. Both the physics experiment cooperation and the laser technology collaboration are welcomed at NLHPLP.

Finite terms Hylleraas- and Kinoshita-type variational wave functions are considered for three-body systems.

For calculation of the energies the stochastic variational method is applied. This approach leads to significant decrease of the number of terms present in the trial wave function.

In Coulombic case local properties of wave functions are restricted by the Kato's cusp conditions. It is showed that Kato's cusp conditions restrict the possible terms in variational calculations. Constraints for the linear expansion coefficients are also derived and a recursion type solution is given. Local and global properties of wave functions with correct cusp conditions are studied, finally the double-electron photoionization is considered.

In our latest study new sets of functions with arbitrary large finite cardinality are constructed for two-electron atoms. Functions from these sets exactly satisfy the Kato's cusp conditions. The new functions are special linear combinations of Hylleraas- and/or Kinoshita-type terms. Standard variational calculation, leading to matrix eigenvalue problem,  can be carried out to calculate the energies of the system.

There is no need for optimization with constraints to satisfy the cusp conditions.

Today’s materials research is unthinkable without the analytical tools that allow studying structure and dynamics from the subatomic to the macroscopic level.

Among those tools neutron scattering occupies a prominent position given the particular properties of the neutron as a probe.

Recent progress in instrumentation has contributed to reinforcing the role of neutron scattering making it accessible to an even wider range of users.

In this presentation modern neutron scattering as a tool for materials investigations will be briefly introduced. Then, by highlighting recent scientific results, the scientific potential of neutron scattering will be illustrated. The topics will range from fundamental questions in magnetism to structural biology.

In order to make the talk accessible to a broad audience the accent will be placed on the scientific impact of the experiments avoiding technical details.

Ultrafast Coherent Multidimensional Electronic Spectroscopic belongs to the family of ultrafast nonlinear optical spectroscopy, and is an improvement over conventional ultrafast pump probe (transient absorption) spectroscopy, as it has the ability to resolve both the excitation and detection frequencies in an ultrafast experiment while still maintaining femtosecond time resolution. We will describe our efforts in the development and applications of these techniques to the study of excitation energy transfer (EET) processes in photosynthetic light-harvesting antenna systems.

Laser-plasma particle acceleration is a non-traditional acceleration technique that could lead to a significant downsizing of future high-energy accelerators [1-2].  Recently we conducted laser-plasma electron acceleration research in Shanghai, China. Experiments were based upon a newly-installed 200 TW 30 fs Ti:sapphire laser. We performed a few types of laser wakefield acceleration (LWFA) experiments; the first was based on the self-injection of electrons in 4 mm long He plasma interacted with 30 TW laser pulses (a0 ~1.2). We observed ~120 MeV electron beams with ~ 40 % energy-spread [3]. In order to improve the electron beams we conducted a second type of experiments where we employed the ionization-injection mechanism, by which we observed a significant enhancement of the beam energy up to 400 MeV and a reduction of the energy-spread to 4% [4]. In a follow-up experiment on ionization injection, and in order to boost the electron energy and quality, we employed ~ 120 TW laser pulses and 1 cm-scale plasma. Here we observed narrow energy-spread beams (7 %) with 1.2 giga-electron volts peak energy; see Fig. 1 [5]. The experimental results and the involved physics were all verified by 3D-PIC simulations using OSIRIS code. Additionally, we have measured the emission of synchrotron x-rays (due to the betatron oscillations) from the accelerated relativistic electrons; few mrad, hard x-ray beams with energy up to 100 keV were observed [6]. Finally, by the electrodynamics process of bremsstrahlung we have observed electron-position pairs with energies of 100 MeV and 10 MeV gamma ray beams [7]. In my talk, some of those topics [8] will be discussed in details.

The catalytic activity of proteins is a function of structural changes. Very often these are as minute as protonation changes, hydrogen bonding changes and amino acid side chain reorientations. To resolve these, a methodology is afforded that not only provides the molecular sensitivity but allows to trace the sequence of these hierarchical reactions at the same time. I will showcase results from time-resolved IR spectroscopy [1,2] which was applied to channelrhodopsin [3].  Channelrhodopsin represents the first light-activated ion channel to found the basis of the new and exciting field of optogenetics [4]. I shall also provide an outlook towards novel experimental approaches like THz pump / IR probe spectroscopy or near-field IR nanoscopy (see figure below) that are currently developed in my lab [5]. We believe that some of these approaches have the potential to provide new science.

FERMI is an externally seeded FEL source, based on the high-gain harmonic generation scheme (HGHG). FERMI has two FEL line, FEL-1, which covers the wavelength range between 100 and 17 nm and FEL-2 in the range between 17 and 4 nm. The shortest pulses delivered by FEL-1 ad FEL-2 have respectively a duration of 40-90 fs and 20-30 fs according to pulse duration scaling with the wavelength.

Controlling pulse duration, and, more generally, the temporal intensity profile of free-electron laser (FEL) pulses, would permit to resolve faster processes, as electronic rearrangements and exploration of electronic motions and nuclear phenomena. This possibility would extend the experiments targeted by FERMI.

In this talk I present the methods that could be used to reduce the pulse length in FERMI and explain how we measure the pulse shape of an extreme ultraviolet externally seeded FEL operating in high-gain harmonic generation mode.

Nanoplasmas formed from doped helium nanodroplets by irradiation with intense laser pulses feature peculiar properties. In the NIR range, a helium ionization avalanche is triggered by tunnel ionization of the dopant cluster at comparatively low light intensities (~1014 W/cm2). Subsequent light absorption is enhanced by resonances due to nanoplasma anisotropies [PRL 107, 173402 (2011)] and expansion [NJP 14 075016 (2012)]. Consequently, dopant and helium atoms charge up to high charge states [J. Mod. Opt. 64, 1061 (2017)], and energetic ions and electrons are emitted by Coulomb explosion. Surprisingly, recent single-shot velocity-map images of nanoplasma electrons display sharp electron energies peaked at ~1 eV energies. Prospects for probing helium nanoplasmas driven by intense MIR and XUV laser pulses are discussed.

An existing CPA high power laser pulse such as a commercially available PW laser could be readily converted into a single-cycled laser pulse in the 10PW regime without significant loss of energy through the compression. We will describe a way to attain this goal heralding a new set of fascinating applications to science, including medicine, environmental and material science. These include a laser ion accelerator, called single-cycle laser acceleration (SCLA), and bow wake electron acceleration. In addition, in the X-ray regime, single-cycled laser pulses may be readily converted through relativistic compression into a single cycled, X-ray laser pulse. We argue that it could be the quickest and very innovative way to ascend to the EW (Exawatt) and zs (zeptosecond) regime. In this talk we will cover the generation of single-cycled pulse and its numerous and revolutionary applications

An overview discussion about Spectra-Physics Lasers, capabilities, products and applications.  Emphasis on laser technologies designed for research laboratories, particularly large laser infrastructure facilities including pump lasers, short pulse ultrafast oscillators and amplifiers and advanced technologies such as CEP and laser synchronization accessories.

National Energetics is developing high intensity lasers from few tens of Terawatts to 10 Petawatts for scientific applications. These are CPA laser systems based on classic Ti:Sapphire as well as mixed glass, using novel technology for augmented repetition rate at kJ level. Moreover, NE is also providing full remote controls system integrated with the infrastructure.

The presentation will focus on the 10 PW (1500J in 150 fs at 1 shot/minute) laser under construction for ELI-Beamlines. This is a hybrid system with a high contrast OPCPA front-end (4J@5Hz) with spectral shaping capabilities followed by Nd doped-glass amplification for high output energy with split-disk, liquid-cooled technology.

Characteristics of high temporal contrast hybrid system based on short pulse OPCA and classic Ti:Sa amplifiers at 800 nm will also be presented.

By deriving the correct formula of the spectral energy density of black-body radiation, Max Planck (1858-1947) discovered in 1900 the fourth fundamental physical constant h, the elementary quantum of action. On the occasion of Planck’s 160th birthday, and the centenary of his receiving the Nobel Prize, we keep track of Planck’s lesser known original thoughts concerning the black-body radiation problem. We point out that, Planck has also solved various other important problems in physics, and his methods and interpretations still may have relevance even today. We shall deal with his so-called second theory, which already contained the concept of induced emission and zero-point energy. We shall also show Planck’s original derivation of the natural system of units (Planck length, mass, time and temperature), which plays a distinguished role in cosmological physics.

[1] G. Rascol, H. Bachau, V. T. Tikhonchuk, H.-J. Kull, T. Ristow, Phys. Plasmas 13, 103108 (2006).

[2] H.-J. Kull, New J. Phys. 14, 055013 (2012).

[3] C. Baumann, H.-J. Kull, and G.M. Fraiman, Phys. Rev. A 92, 063420 (2015).

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.

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.

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.

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.

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.

References:

1. H. Vincenti, S. Monchocé, S. Kahaly, Ph. Martin and F. Quéré“Optical properties of relativistic plasma mirrors” - Nature Communications5, 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)

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