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The interaction of two counter-propagating electromagnetic waves in a vacuum is analyzed within the framework of the Heisenberg-Euler formalism in quantum electrodynamics. The nonlinear electromagnetic wave in the quantum vacuum is characterized by wave steepening, subsequent generation of high order harmonics and electromagnetic shock wave formation with electron{positron pair generation at the shock wave front., 5 pages, 2 figures

© 2019 American Physical Society. Guiding of relativistically intense laser pulses with peak power of 0.85 PW over 15 diffraction lengths was demonstrated by increasing the focusing strength of a capillary discharge waveguide using laser inverse bremsstrahlung heating. This allowed for the production of electron beams with quasimonoenergetic peaks up to 7.8 GeV, double the energy that was previously demonstrated. Charge was 5 pC at 7.8 GeV and up to 62 pC in 6 GeV peaks, and typical beam divergence was 0.2 mrad.

Tight focusing of radially- or azimuthally-polarized electromagnetic waves becomes attractive because of the strong field generation in the longitudinal direction. In this paper, we investigate the strength of longitudinal electric field when a radially-polarized femtosecond PW laser pulse is tightly focused by a parabolic surface. From the calculation using the vector diffraction approach, it has been shown that the highest strength of 2.2 × 1013 V/cm can be reached for the longitudinal field with a radially-polarized 11.2-fs, 11.2-J uniform-beam-profile laser pulse. The difference in the strength of longitudinal field with different beam profile and the spectrum of a laser pulse has been also carefully examined. The propagation of a laser spot has been simulated under an extremely-tight-focusing condition (0.25 in terms of f-number) and an achievable field strength for a standing longitudinal field has been examined by colliding two radially-polarized fs PW-level laser pulses.

The impact of stochasticity effects (SEs) in photon emissions on the proton energy spectra during laser-plasma interaction is theoretically investigated in the quantum radiation-dominated regime, which may facilitate SEs experimental observation. We calculate the photon emissions quantum mechanically and the plasma dynamics semiclassically via two-dimensional particle-in-cell simulations. An ultrarelativistic plasma generated and driven by an ultraintense laser pulse head-on collides with another strong laser pulse, which decelerates the electrons due to radiation-reaction effect and results in a significant compression of the proton energy spectra because of the charge separation force. In the considered regime the SEs are demonstrated in the shift of the mean energy of the protons up to hundreds of MeV. This effect is robust with respect to the laser and target parameters and measurable in soon available strong laser facilities.

High power laser science and engineering 7, e54 (2019). doi:10.1017/hpl.2019.36, Published by Cambridge Univ. Press, Cambridge

The P3 installation of ELI-Beamlines is conceived as an experimental platform for multiple high-repetition-rate laser beams spanning time scales from femtosecond via picosecond to nanosecond. The upcoming L4n laser beamline will provide shaped nanosecond pulses of up to 1.9 kJ at a maximum repetition rate of 1 shot/min. This beamline will provide unique possibilities for high-pressure, high-energy-density physics, warm dense matter, and laser–plasma interaction experiments. Owing to the high repetition rate, it will become possible to obtain considerable improvements in data statistics, in particular, for equation-of-state data sets. The nanosecond beam will be coupled with short sub-picosecond pulses, providing high-resolution diagnostic tools by either irradiating a backlighter target or driving a betatron setup to generate energetic electrons and hard X-rays.

Relativistic flying forcibly oscillating reflective diffraction gratings are formed by an intense laser pulse (driver) in plasma. The mirror surface is an electron density singularity near the joining area of the wake wave cavity and the bow wave; it moves together with the driver laser pulse and undergoes forced oscillations induced by the field. A counter-propagating weak laser pulse (source) is incident at grazing angles, being efficiently reflected and enriched by harmonics. The reflected spectrum consists of the source pulse base frequency and its harmonics, multiplied by a large factor due to the double Doppler effect.

Laser-driven ion acceleration attracts large attention due to variety of applications. In order to enhance accelerated proton energy and flux, we investigate the influence of laser-driven relativistic magnetic reconnection on the ion acceleration processes. In this relativistic regime, the longitudinal electric field becomes significantly enhanced and plays an important role in charged particle acceleration. To realize conditions for the magnetic reconnection, two spatially separated relativistic laser beams were used. The results obtained show a shift of high energy proton propagation direction compare to that corresponding to the target normal sheath acceleration scenario as well as enhancement in proton flux.

Usage of double-layer targets consisting of heavy and light material with modulated interface between them provides a way for laser-driven generation of collimated ion beams. With extensive 2D3V PIC simulations we show that this configuration may result in a development of a relativistic instability with Rayleigh-Taylor and Richtmyer-Meshkov like features. Initially small perturbations are amplified during the laser-target interaction leading to the formation of low-density plasma regions and high-density bunches between them, which are accelerated by the laser radiation pressure as whole compact structures. That results in collimated quasi-monoenergetic proton beam with high average energy. The properties of this proton beam such as its low emittance (one order of magnitude lower compared to that of conventional accelerators) and divergence are discussed. Results are compared with similar acceleration schemes such as double-layer target without corrugation and single-layer target., Comment: 16 pages, 11 figures, section 3.3 with new results added, references added, figures added, introduction and conclusion expanded, previous results unchanged. Supplementary video and web-based interactive 3D application: http://vbl.eli-beams.eu/apps/mm-bunch-video/ http://vbl.eli-beams.eu/apps/demo/simulation-mm/

The focused field and its intensity distribution achieved by the 4π-spherical focusing scheme are investigated within the framework of diffraction optics. Generalized mathematical formulas describing the spatial distributions of the focused electric and magnetic fields are derived for the transverse magnetic and transverse electric mode electromagnetic waves with and without the orbital angular momentum attribute. The mathematical formula obtained shows no singularity in the field in the focal region and satisfies the finite field strength and electromagnetic energy conditions. The 4π-spherical focusing of the transverse magnetic mode electromagnetic wave provides the highest field strength at the focus and the peak intensity reaches 1026 W/cm2 for the laser power of 100 PW at 800 nm wavelength. As an example of using the mathematical formula, the electron-positron pair production via the Schwinger mechanism is analyzed and compared with previous results.

Aerosol nanoparticle injectors are fundamentally important for experiments where container-free sample handling is needed to study isolated nanoparticles. The injector consists of a nebuliser, a differential pumping unit, and an aerodynamic lens to create and deliver a focused particle beam to the interaction point inside a vacuum chamber. The tightest focus of the particle beam is close to the injector tip. The density of the focusing carrier gas is high at this point. We show here how this gas interacts with a near infrared laser pulse (800 nm wavelength, 120 fs pulse duration) at intensities approaching 1016 Wcm−2. We observe acceleration of gas ions to kinetic energies of 100s eV and study their energies as a function of the carrier gas density. Our results indicate that field ionisation by the intense near-infrared laser pulse opens up a plasma channel behind the laser pulse. The observations can be understood in terms of a Coulomb explosion of the created underdense plasma channel. The results can be used to estimate gas background in experiments with the injector and they open up opportunities for a new class of studies on electron and ion dynamics in nanoparticles surrounded by a low-density gas.

Fourfold pulse compression from 840 fs to 192 fs was obtained by inserting a time delay between the ordinary- and extraordinary fundamental pulses prior to type II frequency doubling in a BBO crystal. Despite a conversion efficiency of 26 %, an increase of peak power of nearly 20 % was achieved.

Our paper concerns with simulation of plasma dynamics in hydrogen-filled capillary discharge with circular and square cross sections under the same conditions. External domain with moderate size which is formed by a passive insulator was taken into account to perform these simulations. The general dynamics of plasma inside these capillaries are found to be quite similar to each other.

Within 2017, the ELIMED (ELI-Beamlines MEDical applications) transport beam-line and dosimetric systems for laser-generated beams will be installed at the ELI-Beamlines facility in Prague (CZ), inside the ELIMAIA (ELI Multidisciplinary Applications of laser–Ion Acceleration) interaction room. The beam-line will be composed of two sections: one in vacuum, devoted to the collecting, focusing and energy selection of the primary beam and the second in air, where the ELIMED beam-line dosimetric devices will be located. This paper briefly describes the transport solutions that will be adopted together with the main dosimetric approaches. In particular, the description of an innovative Faraday Cup detector with its preliminary experimental tests will be reported.

Exceptionally high reaction gains of hydrogen protons measured with the boron isotope 11 are compared with other fusion reactions. This is leading to the conclusion that secondary avalanche reactions are happening and confirming the results of high-gain, neutron-free, clean, safe, low-cost, and long-term available energy. The essential basis is the unusual non-thermal block-ignition scheme with picosecond laser pulses of extremely high powers above the petawatt range.

One of the most robust methods, demonstrated up to date, of accelerating electron beams by laser-plasma sources is the utilization of plasma channels generated by the capillary discharges. These channels, i.e., plasma columns with a minimum density along the laser pulse propagation axis, may optically guide short laser pulses, thereby increasing the acceleration length, leading to a more efficient electron acceleration. Although the spatial structure of the installation is simple in principle, there may be some important effects caused by the open ends of the capillary, by the supplying channels etc., which require a detailed 3D modeling of the processes taking place in order to get a detailed understanding and improve the operation. However, the discharge plasma, being one of the most crucial components of the laser-plasma accelerator, is not simulated with the accuracy and resolution required to advance this promising technology. In the present work, such simulations are performed using the code MARPLE. First, the process of the capillary filling with a cold hydrogen before the discharge is fired, through the side supply channels is simulated. The main goal of this simulation is to get a spatial distribution of the filling gas in the region near the open ends of the capillary. A realistic geometry is used for this and the next stage simulations, including the insulators, the supplying channels as well as the electrodes. Second, the simulation of the capillary discharge is performed with the goal to obtain a time-dependent spatial distribution of the electron density near the open ends of the capillary as well as inside the capillary. Finally, to evaluate effectiveness of the beam coupling with the channeling plasma wave guide and electron acceleration, modeling of laser-plasma interaction was performed with the code INF&RNO, 11 pages, 9 figures

For several decades the capillary discharges have been under intensive investigations due to various promising applications, e.g. for the laser electron accelerators as well as for the X-ray lasers [1,2]. A major portion of the experiments were done with circular cross-section capillaries. An appropriate theoretical and numerical study of circular capillaries can be greatly simplified to a 1D model [3] assuming rotational and axial symmetries of the plasma flow in a long thin channel. On the other hand, studying capillaries with non-circular cross-section [4], which have been attracting substantially less attention, requires more complicated 2D models. Such capillaries, for example, square one, possess several advantages related to their fabrication as well as for plasma diagnostics The aim of our work is to compare the plasma density and temperature distributions formed at the quasistationary stage of the discharge. We present the results of MHD simulations of hydrogen-filled capillary discharges with circular and rectangular cross-sections under almost the same conditions characterizing the initial configurations and the external electric circuit. The simulation parameters are choosen to correspond to the capillary discharge based waveguide for the laser wakefield accelerator [5]. Bibliography [1] Leemans W. P. et al 2014 Phys. Rev. Lett. 113 245002 [2] Benware B. R. et al 1998 Phys. Rev. Lett. 81 5804 [3] Bobrova N. A. et al 2001 Phys. Rev. E 65 016407 [4] Gonsalves A. J. et al 2007 Phys. Rev. Lett. 98 025002 [5] Esarey E. et al 2009 Rev. Mod. Phys. 81 1229

A new generation laser system at ELI beamlines will provide a 10 PW peak power in a 150 fs laser pulse. This opens new possibilities for experiments on laser-electron scattering at extreme intensities. High energy photons (x-rays or gamma-rays) are produced through nonlinear Compton scattering, and they subsequently decay into electron-positron pairs. The pair yield depends on several factors: the electron beam energy, the laser intensity and the duration of the interaction. Prevous studies focused mostly on the short lasers (~ 30 fs). However, using a longer laser pulse (~ 150 fs) can be an advantage, because it increases the effective interaction time and can deliver a higher number of pairs. A powerful tool that supports theoretical studies of laser-matter interactions and helps design of experiments are particle-in-cell (PIC) codes. PIC code OSIRIS has an additional Quantum electrodynamics (QED) module that includes discrete photon emission (non-linear Compton scattering) and Breit-Wheeler electron-positron pair production, as well as macroparticle merging that allows to control the total number of particles in the simulation. In this work, OSIRIS is deployed to model the interaction of short and long lasers of extreme intensities (I>10^22) with electron beams obtained from a laser wakefield accelerator. Measurable experimental signatures are discussed, the number of electron-positron pairs and the overall quality of the newly produced beam.

Electron vortices appear in the wake of a finite length laser pulse propogating in the underdense plasma. Usually they form two chains of vortices with opposite signs of the magnetic fields locked inside an electron cavity. Using 2D PIC simulations, we discuss the effects of evolution of single and binary electron vortices. Single electron vortices, though being in a quasistationary state on electron timescales, evolve on ion timescales, leading to anisotropic multishell ion motion. Binary electron vortices may be subject to complex motions, which can be described by the point-vortex solutions of Hasegawa-Mima equation. When the finite radius effects come into play, we observe effects as magnetic field annihilation with the subsequent fast electron bunch generation and secondary vortex formation.

Summarization: Numerical investigations on high energy proton beam interaction with high density Boron plasma allows to simulate conditions concerning the alpha production from recent experimental measurements. The experiments measure the alpha production due to p11B nuclear fusion reactions when a laser-driven high energy proton beam interacts with Boron plasma produced by laser beam interaction with solid Boron. The alpha production and consequently the efficiency of the process depends on the initial proton beam energy, proton beam density, the Boron plasma density and temperature, and their temporal evolution. The main advantage for the p11B nuclear fusion reaction is the production of three alphas with total energy of 8.9 MeV, which could enhance the alpha heating effect and improve the alpha production. This particular effect is termed in the international literature as the alpha avalanche effect. Numerical results using a multi-fluid, global particle and energy balance, code shows the alpha production efficiency as a function of the initial energy of the proton beam, the Boron plasma density, the initial Boron plasma temperature and the temporal evolution of the plasma parameters. The simulations enable us to determine the interaction conditions (proton beam-B plasma) for which the alpha heating effect becomes important. Παρουσιάστηκε στο: Research Using Extreme Light: Entering New Frontiers with Petawatt-Class Lasers III 2017

HELL is the high energy electron beamline under development at ELI-Beamlines, which is expected to produce GeV electrons at high repetition rate. The aim of HELL is dual: to improve the performances of the laser electron accelerator, and to deliver stable beams for external users. In this work, we present the recent developments towards the delivery of stable and calibrated beams for external users. The design of the HELL User Station will be presented and discussed along with simulations and experimental data collected in different facilities.

The laser-driven Undulator X-ray source (LUX) is designed to be a user beamline providing ultra-short EUV photon pulses with a central wavelength tuneable in the range of 0.4 to 4.5 nm and a peak brilliance of up to 10 21 photons/(s.mrad 2 .mm 2 .0.1% B.W.), which makes this source comparable with modern synchrotron sources. The source shall provide a focal spot size well below 10 μm and a range of auxiliary beams for complex pump-and-probe experiments and it is also an important experimental milestone towards a future laser driven Free Electron Laser. Unique femtosecond nature of the laser-plasma electron acceleration in combination with extremely small transverse emittance of the electron beam is the major advantage of the LWFA technique. Preservation of the electron beam quality is a complicated task for a dedicated electron beam line, which has to be designed to transport the electron beam from the LWFA source up to the undulator. In this report we discuss main requirements on the LWFA source and the electron beam optics of the LUX source and solutions to produce required quality photon beam in the undulator and we also discuss the effect of realistic setup parameters on the quality of the electron beam in the undulator within the range of systematic errors.

Electron vortices appear in the wake of a finite length laser pulse propogating in the underdense plasma. Usually they form two chains of vortices with opposite signs of the magnetic fields locked inside an electron cavity. Using 2D PIC simulations, we discuss the effects of evolution of single and binary electron vortices. Single electron vortices, though being in a quasistationary state on electron timescales, evolve on ion timescales, leading to anisotropic multishell ion motion. Binary electron vortices may be subject to complex motions, which can be described by the point-vortex solutions of Hasegawa-Mima equation. When the finite radius effects come into play, we observe effects as magnetic field annihilation with the subsequent fast electron bunch generation and secondary vortex formation.

Nowadays the innovative high power laser-based ion acceleration technique is one of the most interesting challenges in particle acceleration field, showing attractive characteristics for future multidisciplinary applications, including medical ones. Nevertheless, peculiarities of optically accelerated ion beams make mandatory the development of proper transport, selection and diagnostics devices in order to deliver stable and controlled ion beams for multidisciplinary applications. This is the main purpose of the ELIMAIA (ELI Multidisciplinary Applications of laser-Ion Acceleration) beamline that will be realized and installed within 2018 at the ELI-Beamlines research center in the Czech Republic, where laser driven high energy ions, up to 60 MeV/n, will be available for users. In particular, a crucial role will be played by the on-line diagnostics system, recently developed in collaboration with INFN-LNS (Italy), consisting of TOF detectors, placed along the beamline (at different detection distances) to provide online monitoring of key characteristics of delivered beams, such as energy, fluence and ion species. In this contribution an overview on the ELIMAIA available ion diagnostics will be briefly given along with the preliminary results obtained during a test performed with high energy laser-driven proton beams accelerated at the VULCAN PW-laser available at RAL facility (U.K.).

Extreme laser pulses driving non-equilibrium processes in high density plasmas permit an increase of the fusion of hydrogen with the boron isotope 11 by nine orders of magnitude of the energy gains above the classical values. This is the result of initiating the reaction by non-thermal ultrahigh acceleration of plasma blocks by the nonlinear (ponderomotive) force of the laser field, in addition to the avalanche reaction that has now been experimentally and theoretically manifested. The design of a very compact fusion power reactor is scheduled to produce then environmentally fully clean and inexhaustible generation of energy at profitably low costs. The reaction within a volume of cubic millimetres during a nanosecond can only be used for controlled power generation., 10 pages, 5 fugures

The paper examines the prospects of using laser plasma as a source of high-energy ions for the purpose of hadron beam therapy — an approach which is based on both theory and experimental results (ions are routinely observed to be accelerated in the interaction of high-power laser radiation with matter). Compared to therapy accelerators like synchrotrons and cyclotrons, laser technology is advantageous in that it is more compact and is simpler in delivering ions from the accelerator to the treatment room. Special target designs allow radiation therapy requirements for ion beam quality to be satisfied. (reviews of topical problems)

We identify the physical scenarios of nonlinear spatiotemporal dynamics of extreme-power laser fields enabling compression of a broad-beam ultrafast multipetawatt laser output to subexawatt few-cycle light pulses focusable to pulse intensities up to 10 25 W/cm 2 . We show that, with a careful control over the key limiting physical effects, which include dispersion, pulse self-steepening, small-scale self-focusing, and ionization effects, enhanced self-phase modulation of multipetawatt laser waveforms in a solid medium can provide spectral bandwidths compressible to few-cycle pulse widths with output beam profiles focusable to ultrarelativistic intensities.

The interaction of high intensity laser radiation with mass-limited target exhibits significant enhancement of the ion acceleration when the target is surrounded by an underdense plasma corona, as seen in numerical simulations. The self-generated quasistatic magnetic field squeezes the corona causing the intensification of a subsequent Coulomb explosion of the target. The electric field intensification at the target edges and plasma resonance effects result in the generation of characteristic density holes and further contributes to the ion acceleration.The interaction of high intensity laser radiation with mass-limited target exhibits significant enhancement of the ion acceleration when the target is surrounded by an underdense plasma corona, as seen in numerical simulations. The self-generated quasistatic magnetic field squeezes the corona causing the intensification of a subsequent Coulomb explosion of the target. The electric field intensification at the target edges and plasma resonance effects result in the generation of characteristic density holes and further contributes to the ion acceleration.

Measured highly elevated gains of proton–boron (HB11) fusion (Picciotto et al., Phys. Rev. X 4, 031030 (2014)) confirmed the exceptional avalanche reaction process (Lalousis et al., Laser Part. Beams 32, 409 (2014); Hora et al., Laser Part. Beams 33, 607 (2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh acceleration above $10^{20}~\text{cm}~\text{s}^{-2}$ for plasma blocks was theoretically and numerically predicted since 1978 (Hora, Physics of Laser Driven Plasmas (Wiley, 1981), pp. 178 and 179) and measured (Sauerbrey, Phys. Plasmas 3, 4712 (1996)) in exact agreement (Hora et al., Phys. Plasmas 14, 072701 (2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell’s stress tensor by the dielectric properties of plasma leading to the nonlinear (ponderomotive) force $f_{\text{NL}}$ resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. This is supported also by other experiments with very high HB11 reactions under different conditions (Labaune et al., Nature Commun. 4, 2506 (2013)).

The interaction of high intensity laser radiation with an underdense plasma may lead to the formation of electron vortices. Though being quasistationary on the electron timescales, these structures tend to expand on a proton timescale due to Coulomb repulsion of ions. Using a simple analytical model of a stationary vortex as an initial condition, 2D PIC simulations are performed. A number of effects are observed such as vortex boundary field intensification, multistream instabilities at the vortex boundary, and bending of the vortex boundary with the subsequent transformation into smaller electron vortices.

Gravitational wave generation by a strong shock wave in the interaction of high power laser with matter is analyzed in linear approximation of gravitational theory. The analytical formulas and estimates are derived for the metric perturbations and the radiated power of the generated gravitational waves. Furthermore the characteristics of polarization and the behavior of test particles are investigated in the presence of gravitational wave which will be important for the detection., Comment: 10 pages, 5 images

The ELIMED (MEDical and multidisciplinary application at ELI-Beamlines) beamline is being developed with the aim of transport and select in energy proton and ion beams accelerated by laser-matter interaction at ELI-Beamlines (Extreme Light Infrastructure) user facility in the Czech Republic [1] . The beamline will be a key part of the ELIMAIA (ELI Multidisciplinary Application of laser-Ion Acceleration) user beamline, where experiments will be carried out with the purpose of investigating the feasibility of using laser-driven beams for multidisciplinary applications, including medical ones [2] . A Monte Carlo simulation of the ELIMED beamline has been developed for the following purposes: to support the design of the beamline in terms of particle transport efficiency, to optimize the beam parameters at the irradiation point in air and, finally, to predict the transport elements parameters to deliver dose distributions of possible clinical relevance [3] . The application has been developed with the Geant4 Monte Carlo toolkit. It has been designed in a modular way in order to easily switch on/off geometrical components according to different experimental setups. The application has been preliminary validated comparing particle tracks to results obtained with reference codes for transport of particles in magnetic fields, with a good agreement. Specifically, energy distributions, lateral beam profiles and longitudinal dose distributions in the in-air final section were simulated for proton beams with energies ranging between 5 and 60 MeV. A transmission efficiency of more than 10% was calculated at 60 MeV, which implies the delivery of up to tens of cGy per pulse at the sample irradiation point. Assuming a repetition rate of 1 Hz, between 1 and 10 Gy/min can be potentially achieved in such conditions. These results are of great importance to assess the possibility of carrying out in vitro and in vivo radiobiology experiments aiming to demonstrate the possible future use of optically accelerated beams for therapeutic purposes.

Using quantum electrodynamics particle-in-cell simulations, we optimize the gamma flare ($\gamma$-flare) generation scheme from interaction of high power petawatt-class laser pulse with tailored cryogenic hydrogen target having extended preplasma corona. We show that it is possible to generate an energetic flare of photons with energies in the GeV range and total flare energy being on a kilojoule level with an efficient conversion of the laser pulse energy to $\gamma$-photons. We discuss how the target engineering and laser pulse parameters influence the $\gamma$-flare generation efficiency. This type of experimental setup for laser-based $\gamma$ source would be feasible for the upcoming high power laser facilities. Applications of high intensity $\gamma$ ray beams are also discussed., Comment: 11 pages, 7 figures

ELI (Extreme Light Infrastructure) multidisciplinary applications of laser-ion acceleration (ELIMAIA) is one the user facilities beamlines of the ELI-Beamlines facility in Prague. It will be dedicated to the transport of laser-driven ion beams and equipped with detectors for diagnostics and dosimetry, in order to carry out experiments for a broad range of multidisciplinary applications. One of the aims of the beamline is also to demonstrate the feasibility of these peculiar beams for possible medical applications, which means delivering controllable and stable beams, properly monitoring their transport parameters and accurately measuring the dose per shot. To fulfil this task, innovative systems of charged particle beam diagnostics have been realized and alternative approaches for relative and absolute dosimetry have been proposed. Concerning the first one, real-time diagnostic solutions have been adopted, involving the use of time-of-flight techniques and Thomson parabola spectrometry for an on-line characterization of the ion beam parameters, as well as radiochromic films, nuclear track detectors (typically CR39), and image plates for single shot measurements. For beam dosimetry, real-time beam/dose monitoring detectors have been realized, like the secondary emission monitor and a double-gap ionization chamber, which can be cross calibrated against a Faraday cup, used for absolute dosimetry. The main features of these detectors are reported in this work together with a description of their working principle and some preliminary tests.

Zusammenfassung Aus einem von 65 Bestanden mit einem Sterben junger Saugferkel ohne Erkrankungen erwachsener Schweine wurde ein Virus isoliert, das bei der Ubertragung auf 15–20 kg schwere Absatzferkel lediglich geringe Temperaturerhohung ohne Immunitatsbildung gegen Schweinepest verursachte. Durch Virulenzsteigerung im Verlauf von Tierpassagen entwickelte sich von der 3. Passage an eine immunisatorische Wirksamkeit mit gleidizeitiger Verlangerung der Periode erhohter Temperatur. Bei weiteren Passagen wurde ein Tier zum Kummerer. In der 9. und den folgenden Passagen trat das klare pathologisch-anatomische Bild der Schweinepest auf. Die Virulenzsteigerung erfolgte im Verlauf der Passagen kontinuierlich. Um eine Virulenzsteigerung zu erreichen, erwies es sich als notwendig, das Viruspassagematerial an den ersten Tagen der Erkrankung zu gewinnen. Nachdem laut Vorbericht in 2 von 65 (d. h. 3%) Bestanden mit Ferkelsterben, wo altere Ferkel uberlebten, Schweinepest festgestellt wurde, mus man damit rechnen, das sich die Virulenz schwachvirulenter nicht immunisierender Schweinepestvirusstamme auch im naturlichen Seuchengeschehen durch Tierpassagen besonders uber Jungtiere bis zum Auftreten erkennbarer Schweinepesterkrankungen steigern kann. Hinsichtlich des Verbreitungsweges solcher sehr schwachvirulenter nicht immunisierender Schweinepestvirusstamme wird auf die diaplacental Ubertragung und das bei der Schweinepest bestehende Persistieren des Virus hingewiesen. Summary Demonstration of a very weakly virulent non-immunising swine fever virus after increased virulence by animal passage From 1 of 65 herds in which young sucking pigs were dying without any signs of illness in the adults, a virus was isolated which when transferred to 15–20 kg. fattening pigs caused very slight rise in temperature and no immunity to swine fever. After increasing its virulence by animal passage there developed from the third passage onwards an ability to immunise and a simultaneous increase in the period of pyrexia. By further passage one animal developed symptoms. In the ninth and subsequent passages the typical pathological picture of swine fever developed. Increase in virulence developed continuously in the course of passage. To produce increased virulence it seems to be necessary to collect virus in the first days of the infection. In the light of the history of 2 out of 65 herds (3%) with deaths in piglets in which older pigs survived, one may have to contend with weakly virulent non-immunising swine fever virus strains in the field which may be passaged, particularly through young animals, so as to cause recognisable swine fever in other age groups. As to the method of spread of such weakly virulent non-immunising strains, transmission by the placenta and the question of virus persisting may well be concerned. Resume Mise en evidence d'un virus de la peste porcine tres faiblement virulent et non immunisant dont la virulence a ete exacerbee au cours de divers passages sur animaux Un virus a ete isole de l'une des 65 exploitations ou l'on constatait la mort des porcelets sans que les animaux adultes ne tombent malades et qui, transmis a des porcs sevres de 15 a 20 kg ne provoquait chez ceux-ci qu'une legere augmentation de temperature sans formation aucune d'immunite contre la peste porcine. Apres que la virulence de la souche ait ete augmentee au cours des passages sur animaux, un effet immunisant s'est manifeste a partir du 3eme passage, tandis que la periode febrile chez les animaux infectes se trouvait prolongee. Au cours des passages ulterieurs, un animal a ete fortement atteint. A partir du 9eme passage, le tableau anatomo-pathologique etait clairement celui de la peste porcine. L'exacerbation de la virulence a continuellement progresse au cours des passages. Pour obtenir une augmentation de la virulence, il s'est avere necessaire de recolter le virus de passage dans les premiers jours qui suivent le debut de la maladie. Vu que dans deux des 65 (c'est-a-dire 3%) exploitations ou l'on observait la mort des porcelets, alors que les animaux plus âges survivaient, on diagnostiquait la peste porcine, il faut admettre que la virulence de certaines souches pestiques, faiblement pathogenes et non immunisantes, peuvent aussi dans le terrain etre exacerbees par le passage au travers de jeunes porcelets a tel point qu'apres ces passages les souches provoquent des affections pestiques manifestes dans les porcheries. Pour ce qui concerne les voies de dissemination de telles souches pestiques, tres faiblement virulentes et non immunisantes, on evoque la transmission transplacentaire et le probleme du virus persistant. Resumen Identificacion de un virus de la peste porcina muy debilmente virulento y no inmunizante tras aumento de su virulencia en el curso de pases por animales De un cerdo de entre 65 explotaciones con una mortandad de lechones jovenes, crecido sin enfermedad alguna, se aislo un virus que con su transmision a cochinillos destetados de 15–20 kg de peso solo producia una ligera hipertermia sin formar inmunidad frente a la peste porcina. Por medio de aumento de la virulencia en el curso de pases por animales, se desarrollo una actividad inmunitoria con prolongacion concomitante del periodo de temperatura elevada a partir del tercer pase. Tras otros pases mas, el animal se transformo en cria desmedrada. En el noveno y sucesivos pases aparecio la clara imagen anatomopatologica de la peste porcina. El aumento de la virulencia sucedia de manera progresiva. Para conseguir la exaltacion de la virulencia se comprobo la necesidad de obtener en los primeros dias de enfermedad el material virosico de pase. Puesto que con arreglo al informe previo en 2 de 65 (es decir en un 3% de) efectivos ganaderos con mortandad de lechones, donde sobrevivian cochinillos mayores, se diagnostico peste porcina, debe contarse con que la virulencia de cepas de peste porcina escasamente virulentas y no inmunizantes tambien se pueden exaltar en el devenir epizootico natural mediante pases por animales, en especial a traves de animales jovenes, hasta la aparicion de enfermedades cognoscibles de peste porcina. Con respecto a la via de difusion de tales cepas de virus de peste porcina tan debilmente virulentas y no inmunizantes, se llama la atencion sobre la transmission diaplacentaria y sobre la cuestion persistencia de virus que existe en la peste porcina.

The main direction proposed by the community of experts in the field of laser-driven ion acceleration is to improve particle beam features (maximum energy, charge, emittance, divergence, monochromaticity, shot-to-shot stability) in order to demonstrate reliable and compact approaches to be used for multidisciplinary applications, thus, in principle, reducing the overall cost of a laser-based facility compared to a conventional accelerator one and, at the same time, demonstrating innovative and more effective sample irradiation geometries. The mission of the laser-driven ion target area at ELI-Beamlines (Extreme Light Infrastructure) in Dolní Břežany, Czech Republic, called ELI Multidisciplinary Applications of laser-Ion Acceleration (ELIMAIA), is to provide stable, fully characterized and tuneable beams of particles accelerated by Petawatt-class lasers and to offer them to the user community for multidisciplinary applications. The ELIMAIA beamline has been designed and developed at the Institute of Physics of the Academy of Science of the Czech Republic (IoP-ASCR) in Prague and at the National Laboratories of Southern Italy of the National Institute for Nuclear Physics (LNS-INFN) in Catania (Italy). An international scientific network particularly interested in future applications of laser driven ions for hadrontherapy, ELI MEDical applications (ELIMED), has been established around the implementation of the ELIMAIA experimental system. The basic technology used for ELIMAIA research and development, along with envisioned parameters of such user beamline will be described and discussed.

Charged particle acceleration using ultra-intense and ultra-short laser pulses has gathered a strong interest in the scientific community and it is now one of the most attractive topics in the relativistic laser-plasma interaction research. Indeed, it could represent the future of particle acceleration and open new scenarios in multidisciplinary fields, in particular, medical applications. One of the biggest challenges consists of using, in a future perspective, high intensity laser-target interaction to generate high-energy ions for therapeutic purposes, eventually replacing the old paradigm of acceleration, characterized by huge and complex machines. The peculiarities of laser-driven beams led to develop new strategies and advanced techniques for transport, diagnostics and dosimetry of the accelerated particles, due to the wide energy spread, the angular divergence and the extremely intense pulses. In this framework, the realization of the ELIMED (ELI-Beamlines MEDical applications) beamline, developed by INFN-LNS (Catania, Italy) and installed in 2017 as a part of the ELIMAIA beamline at the ELI-Beamlines (Extreme Light Infrastructure Beamlines) facility in Prague, has the aim to investigate the feasibility of using laser-driven ion beams in multidisciplinary applications. ELIMED will represent the first user’s open transport beam line where a controlled laser-driven ion beam will be used for multidisciplinary and medical studies. In this paper, an overview of the beamline, with a detailed description of the main transport elements, will be presented. Moreover, a description of the detectors dedicated to diagnostics and dosimetry will be reported, with some preliminary results obtained both with accelerator-driven and laser-driven beams.

Laser wakefield acceleration (LWFA) is able to produce high quality electron bunches interesting for many applications ranging from coherent light sources to high energy physics. The blow-out regime of LWFA provides excellent accelerating structure able to maintain small transverse emittance and energy spread of the accelerating electron beam if combined with localised injection. A modulation of the back of a self-injected electron bunch in the blowout regime of Laser Wakefield Acceleration appears 3D Particle-in-Cell simulations with the code OSIRIS. The shape of the modulation is connected to the polarization of the driving laser pulse, although the wavelength of the modulation is longer than that of the pulse. Nevertheless a circularly polarized laser pulse leads to a corkscrew-like modulation, while in the case of linear polarization, the modulation lies in the polarization plane.

In the framework of the ELI-Beamlines project, the HELL (High energy ELectron by Laser) platform will host an electron beamline with a dual aim: to explore innovative concepts of laser driven electron acceleration and to deliver a stable and reliable electron beam to external users, according to their specific needs. Because of this, it is crucial to identify the possible applications and their respective range of parameters. In order to accomplish this goal, Monte Carlo simulations of electron radiography and radiotherapy are performed and discussed. Once identified those parameter spaces, a beam transport line is studied and presented for each energy range. Finally, beam diagnostics are discussed.

Radiation reaction radically influences the electron motion in an electromagnetic standing wave formed by two super-intense colliding laser pulses. Depending on the laser intensity and wavelength, the quantum corrections to the electron motion and the radiation reaction force can be independently small or large, thus dividing the parameter space into 4 regions. When radiation reaction dominates, the electron motion evolves to limit cycles and strange attractors. This creates a new framework for high energy physics experiments on the interaction of energetic charged particle beams and colliding super-intense laser pulses.

Relativistic solitons arising from the interaction of an intense laser pulse with underdense plasmas are investigated. We show the formation and evolution of the relativistic solitons in a collisionless cold plasma with two dimensional particle-in-cell simulations. Such a kind of solitons will evolve into postsolitons if the time scale is longer than the ion response time. Generally, a substantial part of the pulse energy is transformed into solitons during the soliton formation. This fairly high efficiency of electromagnetic energy transformation can play an important role in the interaction between the laser pulse and the plasma. The energy exchange between the electromagnetic field and the kinetic energy of the soliton is discussed. In homogeneous plasmas, the solitons tend to stay close to the region where they are generated and dissipate due to the interaction with surrounding particles eventually. While the laser pulse propagates through inhomogeneous plasmas, the solitons are accelerated along the plasma density gradient towards lower density.

With the continuing development of laser systems, new important and so-far unexplored fields of research related to interaction of ultra-intense laser beams with matter are opening. At intensities of the order of 1022 W=cm2, electrons may be accelerated in the electromagnetic field of the laser wave and achieve such a high energy that they can enter the regime affected by the radiation reaction. Due to the non-linear Thomson and Compton scattering the accelerated electrons emit photons. The interaction of emitted photons with the laser field may result in effective generation of electron-positron pairs by means of the Breit-Wheeler process. In this work we study the influence of laser pulse polarization on gamma-ray generation during interaction of two colliding and tightly focused laser pulses with a low density target composed of electrons. This paper focuses on evolution of electron trajectories and key parameters χe (probability of photon emission) and χγ(probability of pair generation) in the laser field. These interactions are studied using 2D PIC simulations. It is shown that in the case of circularly polarized and tightly focused laser beams, electrons are not following circular trajectories at the magnetic node of the standing wave established in the focus, which leads to lowering the radiation emission efficiency.

An alternative way may be possible for igniting solid density hydrogen- 11 B (HB11) fuel. The use of >petawatt-ps laser pulses from the non-thermal ignition based on ultrahigh acceleration of plasma blocks by the nonlinear (ponderomotive) force, has to be combined with the measured ultrahigh magnetic fields in the 10 kilotesla range for cylindrical trapping. The evaluation of measured alpha particles from HB11 reactions arrives at the conclusion that apart from the usual binary nuclear reactions, secondary reactions by an avalanche multiplication may cause the high gains, even much higher than from deuterium tritium fusion. This may be leading to a concept of clean economic power generation.

A low contrast nanosecond laser pulse with relatively low intensity (3 × 1016 W cm–2) was used to enhance the yield of induced nuclear reactions in advanced solid targets. In particular the "ultraclean" proton-boron fusion reaction, producing energetic alpha-particles without neutron generation, was chosen. A spatially well-defined layer of boron dopants in a hydrogen-enriched silicon substrate was used as target. The combination of the specific target geometry and the laser pulse temporal shape allowed enhancing the yield of alpha-particles up to 109 per steradian, i.e 100 times higher than previous experimental achievements. Moreover the alpha particle stream presented a clearly peaked angular and energy distribution, which make this secondary source attractive for potential applications. This result can be ascribed to the interaction of the long laser pre-pulse with the target and to the optimal target geometry and composition.

The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions. This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes this species an interesting candidate for the laser driven ion source. Two mechanisms (Magnetic Vortex Acceleration and hole-boring Radiation Pressure Acceleration) of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He3 ions, having almost the same penetration depth as He4 with the same energy per nucleon, require less laser power to be accelerated to the required energy for the hadron therapy., Comment: 8 pages, 3 figures, 1 table

Ultra-short bursts of hard X-ray radiation are generated by interaction of high-contrast femtosecond laser pulses with a jet of liquid Ga. The X-ray emission shows a strong dependence on the angle of incidence and polarization of the laser beam, consistent with the processes of resonant absorption and vacuum heating. As much as 60% of the total X-ray emission consists of [Ga]Kα radiation (9.22–9.25 keV) with a photon flux of 6×109 photons/(s srad). Using this novel X-ray source, static diffraction patterns from a GaAs(111) crystal were recorded with an acquisition time of 2 s.