Outlook on Wake Field Acceleration: the Next Frontier

Following the European Strategy Recommendations high gradient projects have to be studied and optimised. This includes CLIC and FCC as well as possible new techniques such as plasma acceleration. The latter is very promising as to a future replacement technology for conventional acceleration techniques. With lasers as driver beams its acceleration gradients in the range of 100GeV/m may be achieved. This corresponds to the Higgs energy over one meter. With the necessity to go beyond the standard model, new avenues leading to 100GeV over a few meters in a single step are among the must-explore list in the near future. To reach this objective, over the past 2-3 years a succession of novel concepts arose that could represent a new wind to the field of laser acceleration and High Energy Particle Physics. To create the wakefield, they rely on large existing national facilities like, the laser PETAL-Megajoule in Bordeaux, ARC at LLNL,the SLAC electron beam at Stanford, or the SPS proton beam at CERN. Along this effort, a new laser driver concept has been designed involving fiber lasers that will provide high repetition rate and efficiency absent on conventional laser systems. In addition to these, more recently the possibility to create a high energy zepto-second pulse in the 10keV regime of photons opens the possibility to generate the wakefield not in a gas but in a crystal leading to a giant gradient in the TeV/cm regime, an even more revolutionary development. To explore these new opportunities, we are proposing to convene the leaders of the field in particle acceleration and High Energy Physics. Following personnalities are invited : Azaiez Faiçal,Biot Jacques, Brechet Yves, Chao Alexander, Cifarelli Luisa, Cohen-Tannoudji Gilles, Dudley John, Fioni Gabriele, Gales Sydney, Gianotti Fabiola, Heuer Rolf-Dieter, Kieffer Jean-Claude, Korn Georg, Le Quéré Patrick, Lee Jongmin, Lerhner Lorant, Leroy Maurice, Levaillant Denis, Massard Thierry, Osvay Karoly, Pacard Franck, Riboulet Gilles, Ros David, Rus Bedrich, Sandner Wolfgang, Sentis Marc, Shiltsev Vladimir, Shin Young-min, Smoot George, Spiro Michel, Stocchi Achille, Suzuki Atsuto, Verwaerde Daniel, Wada Satoshi, Zamfir Victor Preliminary list of invited speakers : Albert Félicie (LLNL), Aleksan Roy (CEA), Assmann Ralph (DESY), Barty Christopher (LLNL), Brocklesby William (ORC), Caldwell Allen (Heisenberg), Chanteloup J.C. (LULI-XCAN), Chen Pisin (LeCOsPa), Chou Weiren (Fermilab), Dantus Marcos (Michigan State U.), Ebisuzaki Toshikazu (RIKEN), Fuchs Julien (LULI), Gorodetzky Philippe (APC), Homma Kensuke (Hiroshima U.), Jaroszinsky Dino (Strathclyde U.), Kuehl Thomas (GSI), Li Ruxin (SIOM), Limpert Jens (IAP), Martin Philippe (CEA), Miquel Jean-Luc (CEA-PETAL), Nakajima Kazuhisa (CoReLs), Nam Chang Hee (CoReLs), Napoly Olivier (CEA), Naumova Natalia (LOA), Parizot Etienne (APC), Pukhov Alexander (HHU-VLPL), Saeki Takayuki (KEK), Sergeev Alexander (IAP), Shin YM (Northen Illinois U.), Specka Arnd (LLR), Uggerhoj Ulrik (Aarhus U.), Yan Xuequing (Peking U.), Zamfir Victor (ELI-NP), Zuegel J. (Rochetser U.)
  • Thursday, 15 October
    • 08:00 08:30
      Welcome - Registration
    • 08:30 08:45
      Introduction by Michel Spiro and Gerard Mourou
    • 08:45 09:45
      FERMI Lecturer
      • 08:45
        Wakefield Acceleration: Ascent toward 100GeV, “TeV on a chip” and Zeptoscience , and to Astrophysics 1h
        At IZEST we have been marshalling the world’s most powerful lasers to drive wakefield acceleration toward 100GeV [1]. Theis asecnt was described by Nakajima et al. [2]. We describe this program. In this Conference we see several talks highlighting on such efforts. An additional frontier of extreme light at Exawatt level is discussed. This frontier has approached to us much closer than we thought till only recently. We now see the possibility to create fs super-PW optical laser pulses from PW lasers [3]. Such laser pulses can be further converted into (1~10) EW (≥10keV) X-ray laser pulses in attoseconds (as) via the known method [4]. Such X-ray laser pulses simultaneously achieve the highest intensity and shortest laser pulses, in fact consistent with the Conjecture [5], opening the new laser frontier at EW multi-keV in as (or perhaps even zeptoseconds). This possibility to amplify laser to such extreme peak power offers a new paradigm unifying the atomic and subatomic worlds, to include nuclear physics, high energy physics, astrophysics and cosmology. This development stimulated the concept of wakefield acceleration in solid materails such as carbon nanotubes [6]. This makes the leap of the electric field from GeV to TeV per cm, the size of the interaction domian decreases from microns to nanometers, the time scales from femtoseconds to zeptoseconds. Recent studies also show that wakefield acceleration is in the work in astrophysical jets of active galactic nuclei (AGN) [7]. Observed phenomenologies from Blazars seem to be consistent with such wakefield mechanism. [1] www.izest.polytechnique.edu [2] K. Nakajima, et al. Phys. Rev. SAB 14, 09130 (2011). [3] G. Mourou, S. Mirnov, E. Khazanov, and A. Sergeev, Eur. Phys. J. Sp. Tpcs. 228, 1181 (2014). [4] N. Naumova, et al. PRL 93, 195003 (2004). [5] G. Mourou and T. Tajima, Science 331, 41 (2011). [6] T. Tajima, Eur. Phys. J. 223, 1037 (2014). [7] T. Ebisuzaki and T. Tajima, Astropart. Phys. 56, 9 (2014).
        Speaker: Toshiki TAJIMA (University of California Irvine, CA 92697 USA)
    • 09:45 12:25
      Applications Physics of Giant Acceleration
      • 09:45
        Extreme Light Infrastructure - Nuclear Physics (ELI-NP): Status and Perspectives 20m
        Extreme Light Infrastructure - Nuclear Physics (ELI-NP) will be a unique research facility to investigate the impact of very intense electromagnetic radiation on matter with specific focus on nuclear phenomena and their applications. The experiments will be based on a 2x10PW Laser Beam and on a very high brilliance Gamma Beam produced by Compton backscattering of light photons on electrons accelerated by a LINAC. The description of the future ELI-NP facility operational in 2018 and of the planned experiments will be presented.
        Speaker: Dr Victor Zamfir (ELI-NP, Bucharest-Magurele, Romania)
      • 10:05
        Ion acceleration and γ-ray beams generation in low density targets using ultra-high intensity lasers 20m
        The intense research being conducted on sources of laser-accelerated ions and their applications, e.g. radiography and the production of warm dense matter (WDM), is motivated by the exceptional properties that have been demonstrated for proton beams accelerated from planar solid targets, such as high brightness, high spectral cut-off, high directionality and laminarity, and short duration (~ps at the source). These ion sources are very promising for a wide range of applications [1,2] ranging from the production of radio-isotopes and the testing of mechanisms of extreme energy particle production in gamma-ray bursts, but also to improve prospects for the necessary gantry for proton therapy or for fast ignition of inertial confinement fusion targets with high gain. The results in [3,4] using low density targets suggest the possibility of enhancing the efficiency and ease of laser acceleration of ions compared to what has been achieved up to now using solid foils. Recently, important progress has been achieved in the production of the short near-critical density gas jets required in this regime [5]. Scaling laser ion acceleration in the low density regime to ultra high intensities (>$10^{22} W / cm^2$) is a challenge as radiation losses and electron positron pair production change the optimization of the acceleration process. Using large-scale Particle-In-Cell simulations including these effects, we have investigated and modeled the transition to this regime in which intense beams of relativistic ions and a large number of MeV photons can be produced. These relativistic ion beams are of great interest for high-energy laboratory astrophysics as they could be used to prepare the first relativistic collisionless shocks experiments in the laboratory using ultra high intensity laser systems like Apollon or ELI. The study of the development of relativistic collisionless shocks is crucial to test specific astrophysical scenarios (for instance for Gamma Ray Bursts models and particle acceleration models in Supernova Remnants). The γ-ray beams produced can be used to study the Breit-Wheeler process in the laboratory [6]. References [1] E. d’Humières (2012). Ion Acceleration by High Intensity Short Pulse Lasers, Laser Pulses - Theory, Technology, and Applications, Prof. Igor Peshko (Ed.), ISBN: 978-953-51-0796-5, InTech, DOI: 10.5772/46137. [2] A. Macchi et al., Rev. Mod. Phys. 85, 751 (2013). [3] E. d'Humières et al., Plasma Phys. Control. Fusion 55, 124025 (2013). M. Gauthier et al., Phys. Plasmas 21, 013102 (2014). [4] E. d'Humières et al., J. Phys. Conf. Ser. 244, 042023 (2010). E. d'Humières et al., Phys. Plasmas 20, 023103 (2013). [5] F. Sylla et al., Rev. Sci. Instrum. 83, 033507 (2012). [6] X. Ribeyre et al. arXiv:1504.07868 (2015).
        Speaker: Emmanuel d'Humières (Université de Bordeaux)
      • 10:25
        Possibility of pair creation in collision of gamma-ray beams produced with a high intensity laser 20m
        Direct production of electron-position pairs in photon collisions is one of the basic processes in the Universe. The electron-positron production $\gamma$+$\gamma$ to $e^++e^-$ (linear Breit-Wheeler process) is the lowest threshold process in photon-photon interaction, controlling the energy release in Gamma Ray Bursts, Active Galactic Nuclei, black holes and other explosive phenomena [1]. It is also responsible for the TeV cutoff in the photon energy spectrum of extra-galactic sources. The linear Breit-Wheeler process has never been clearly observed in laboratory with important probability of matter creation [2]. Thank with MeV photon source new experimental set-up based on numerical simulation with QED effect is proposed to achieved more than $10^4$ Breit-Wheeler pairs per shot. This scheme offers a possibility of conducting a multi-shot experiment with a reliable statistics on laser systems with pulse energies on the level of a few joules and in a low noise environment without heavy elements. This scheme relies on a collision of relatively low energy (few MeV), intense photon beams. Such beams can be created in interaction of intense laser pulses with thin plastic targets (See Figure). Figure: Experimental setup for the Breit--Wheeler pairs production with MeV colliding photon beams.[5] By colliding two of them in vacuum, one would be able to produce a significant number of electron-positron pairs in a controllable way. We provide details of the experimental setup, estimates from model and numerical simulations of the expected yield of reactions and possible ways of creation of a photon source with requested parameters. The spatial separation of the photon-photon interaction zone seems to be the best way for the detection of the BW pairs emitted in the preferential direction. Thank with MeV photon source [3] and based on numerical simulations with QED effect more than $10^4$ Breit-Wheeler pairs per shot can be acheived [4]. Results from Monte-Carlo simulations will be pressented to proposed a robust experimental design. Moreover, the noise level due to other pair process creation is estimated. We acknowledge the financial support from the French National Research Agency (ANR) in the frame of "The Investments for the Future" Programme IdEx Bordeaux - LAPHIA (ANR-10-IDEX-03-02) - Project TULIMA. This work is partly supported by the Aquitaine Regional Council (project ARIEL). [1] Ruffini, R. et al. Physics Reports 487, 1-140 (2010). [2] Bamber C. et al. Phys. Rev. D, 60, 092004 (1999). [3] Capdessus, R. et al., PRL 110, 215003 (2013). [4] Ribeyre, X. et al., arXiv:1504.07868v1, 29 Apr 2015 [5] http://www.celia.u-bordeaux1.fr/~ribeyre/telechargement/Fig3.png
        Speaker: Xavier Ribeyre (Université de Bordeaux 1)
      • 10:45
        Photo session 10m
      • 10:55
      • 11:25
        Launching magnetized relativistic jets and cosmic ray acceleration by wake field acceleration by strong Alfvenic wave. 20m
        Astrophysical jets which are collimated plasma flows are observed in many astrophysical systems in the universe. The jets from the system of super-massive black hole (M~10^8 solar masses) and accreting gas are known as the active galactic nuclei (AGN) jet. The bulk speed of AGN jet is highly relativistic, i.e., almost speed of light. The physical mechanisms of how the AGN jet is launched and how the AGN jet is accelerated to relativistic speed are not well understood yet. The AGN jet is also known as a strong candidate for the acceleration site of ultra high energy cosmic rays (UHECRs) up to 10^{20}eV. It is not still under debate where is the acceleration site and how UHECRs are accelerated. We study comprehensibly these issues by taking into account a magnetic field, since the magnetic fields play an important role in the accretion disks and launching process of the jet. We have performed 3 dimensional general relativistic magnetohydrodynamic simulations of this system. We observed magnetized outflow is intermittently launched. This jet includes strong magnetic fields. The possibility of UHECRs acceleration by wake field acceleration by relativistic strong Alfven waves inside the jet is discussed.
        Speaker: Akira Mizuta (RIKEN)
      • 11:45
        Accelerating Plasma Mirror to Investigate Black Hole Information Loss Paradox 20m
        Plasma wakefields induced by an intense laser pulse or a particle beam can serve as a relativistic plasma mirror, which, as has been pointed out, can serve to focus light to extremely high intensity. Here we propose a different application of such mirrors. Earlier, Chen and Tajima (1999) invoked the violent acceleration of a single electron by an ultra intense laser as a means to investigate the Unruh effect, whereby the black hole Hawking evaporation may be elucidated in the laboratory. Accelerating mirror has long been a toy model in the investigation of quantum field theory in curved space. It has been shown that, in analogy to the Hawking effect in a bona fide curved space, particles can be created from the vacuum of a flat spacetime with an imbedded accelerating mirror. One critical issue associated with the black hole Hawking evaporation is the information loss paradox, which reveals the conflict between general relativity and quantum field theory. The resolution of this paradox is therefore of fundamental importance to physics. We point out that certain signatures emitted from an accelerating plasma mirror may help to resolve this paradox.
        Speaker: Prof. Pisin CHEN
      • 12:05
        Search for sub-eV dark fields at stimulated laser colliders 20m
        We introduce a novel approach to search for sub-eV resonance states with quasi-parallel photon-photon scatterings in a focused production laser field by further stimulating decay of the produced long-lifetime resonance states with an additional coherent laser field. Therefore, this method can be sensitive to something dark in the Universe [1-3] and be complementary to the well-known methods to search for Axion-Like-Particles. We present the results of the preparatory search [4] and the future prospects [5]. [1] " An approach toward the laboratory search for the scalar field as a candidate of Dark Energy " Yasunori Fujii (Waseda U., RISE), Kensuke Homma (Hiroshima U. & Munich U.). Jun 2010. 10 pp. Published in Prog.Theor.Phys. 126 (2011) 531-553, PTEP 2014 (2014) 089203 DOI: 10.1093/ptep/ptu099, 10.1143/PTP.126.531 e-Print: arXiv:1006.1762 [gr-qc] [2] " Probing the semi-macroscopic vacuum by higher-harmonic generation under focused intense laser fields " K.Homma, D. Habs, and T. Tajima, Published in Applied Physics B (2012) 106, 229 DOI: 10.1007/s00340-011-4567-3 e-Print: arXiv:1103.1748 [hep-ph] [3] " Sensitivity to Dark Energy candidates by searching for four-wave mixing of high-intensity lasers in the vacuum " Kensuke Homma (Hiroshima U. & Ecole Polytechnique). Nov 2012. 32 pp. Published in PTEP 2012 (2012) 04D004, PTEP 2014 (2014) 8, 089201 DOI: 10.1093/ptep/pts073, 10.1093/ptep/ptu100 e-Print: arXiv:1211.2027 [hep-ph] [4] " The first search for sub-eV scalar fields via four-wave mixing at a quasi-parallel laser collider " Kensuke Homma (Hiroshima U. & Ecole Polytechnique), Takashi Hasebe, Kazuki Kume (Hiroshima U.). May 16, 2014. 25 pp. Published in PTEP 2014 (2014) 8, 083C01 DOI: 10.1093/ptep/ptu087 e-Print: arXiv:1405.4133 [hep-ex] [5] " Perspective to search for sub-eV neutral boson resonances with stimulated laser colliders " K. Homma (Hiroshima U. & Ecole Polytechnique). 2014. 7 pp. Published in Eur.Phys.J.ST 223 (2014) 6, 1131-1137 DOI: 10.1140/epjst/e2014-02164-4
        Speaker: Prof. Kensuke Homma
    • 12:25 15:25
      Wakefield Acceleration/Deceleration with existing large Facilities at 100 GeV
      • 12:25
        Prospects for proton-driven plasma acceleration 20m
        Proton beams are the most promising driver of wakefields to accelerate electrons to very high energy in a single plasma cell. After a brief review of the the physical principles, the (AWAKE) experiment at CERN will be described and its current status will be presented. Further considerations for a future proton-driven plasma wakefield accelerator will be discussed.
        Speaker: Allen Christopher Caldwell (Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut) (D)
      • 12:45
        LUNCH 1h 20m
      • 14:05
        PETAL-Megajoule 20m
        Speaker: Jean-Luc miquel
      • 14:25
        Recent results from beam-driven plasma acceleration experiments at FACET 20m
        Recent results from beam-driven plasma acceleration experiments at FACET The field of beam-driven plasma wakefield acceleration has recently seen a rapid experimental progress, in particular with the last few years of running of the FACET facility at SLAC. We present key results recently obtained at FACET. First, the acceleration of a distinct trailing bunch of electrons, at high fields, with high energy efficiency and low energy spread, was demonstrated. Positron behave very differently than electrons in the non-linear blow-out regime studied at FACET. In the experiments, a new regime for positron acceleration, where energy is efficiently transferred from the front to the rear within a single positron bunch was discovered. The self-loading of the wake leads to the formation of a narrow energy spread bunch of the positron bunch.
        Speaker: Erik Adli (University of Oslo (NO))
      • 14:45
        Betatron radiation and laser wakefield acceleration at large scale high energy density science facilities 20m
        The High Energy Density science facilities such as OMEGA, the National Ignition Facility, and in the future the Laser Mega Joule (LMJ), are now uniquely able to recreate in the laboratory conditions of temperature and pressure that were thought to be only attainable in the interiors of stars and planets. To diagnose such transient and extreme states of matter, the development of efficient, versatile and fast (sub-picosecond scale) x-ray probes with energies larger than 50 kilo-electronvolts has become essential for HED science experiments on these specific facilities. We will present results from a recent experiment performed using the Titan laser (150 J, 1 ps) at the Jupiter Laser Facility, LLNL, showing evidence of Betatron x-ray production in the self-modulated regime of laser wakefield acceleration. When a 0.5-1 ps laser pulse with an intensity approaching $10^{20}$ W/cm$^2$ is focused on a gas target (electron density $10^{19}$ cm$^{-3}$), electrons can be accelerated via the self-modulated laser wakefield (SMLWF) regime and the direct laser acceleration (DLA) regime. In SMLWF acceleration, electrons are accelerated by the plasma wave created in the wake of the light pulse, whereas in DLA, electrons are accelerated from the interaction of the laser field with the focusing force of the plasma channel. Experimentally, these two regimes can be distinguished by looking at the laser spectrum transmitted through the gas cell with an optical spectrometer. If the SMLWF mechanism dominates, ($<10^{20}$ W/cm$^2$), the transmitted laser spectrum exhibits intense Raman satellites which measured shifts depend on the electron plasma density. Although Betatron radiation has been observed with picosecond-scale lasers in the DLA regime [1, 2], for normalized vector potentials a0 greater than 10, this experiment constitutes the first observation of Betatron radiation in the SMLWF regime, for a0 ~ 1-3. This was made possible by the addition of a long focal length optics (F/10), favorable for guiding laser pulses in gas targets. We will show a detailed Betatron x-ray source characterization, as well as electron spectra above 200 MeV and forward laser spectra indicating a strongly self-modulated laser wakefield acceleration regime. Perspectives for future experiments on OMEGA-EP, NIF-ARC and LMJ-PETAL will also be discussed. [1] S.P.D. Mangles et al, Phys. Rev. Lett., 94, 245001 (2005). [2] S. Kneip et al, Phys. Rev. Lett., 100, 105006 (2008). *Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344 and supported by the LLNL LDRD program under tracking code 13-LW-076.
        Speaker: felicie albert (Lawrence Livermore National Laboratory)
      • 15:05
        Study on the recovery of the beam energy of International Linear Collider (ILC) by plusma-wakefield deceleration. 20m
        The International Linear Collider (ILC) is the future electron- positron collider machine that will reach the energy frontier of elementary-particle physics at the center-of-mass energy of 500 GeV. The ILC is expected to reveal the precise properties of the Higgs particle and the physics beyond the standard model. The ILC group published the Technical Design Report (TDR) of the machine in June 2013. In the TDR, it is described that the energy consumption of ILC is about 200 MW and the beam energy of electron and positron is 10 MW in total which is dumped after the interaction of beams. In the situation that recent progress of plasma-wakefield physics, we started to study on the recovery of eletron and positron energies at the beam dump by the method of plasma-wakefield deceleration, where the recovered energy will be re-used for the operation of the machine and we can expect less radiation problem at the beam dump. In this article, the recent status of this study will be presented.
        Speaker: Takayuki SAEKI (KEK)
    • 15:25 17:15
      Bridging High Energy Physics and Space technology
      • 15:25
      • 15:55
        Mysteries of Lasers in Space 20m
        Laser–induced plasma jets are an effective and versatile method to reposition space vehicles. Applications include launching, reorbiting and deorbiting. Because spacebased laser systems for this purpose are expensive, it is critical to know the maximum amount of momentum transferred to a vehicle per unit of laser energy. This „momentum coupling coefficient” Cm (N-s/J) mainly depends on five parameters: target material, average ionization state of the plasma jet, and laser intensity, pulsewidth and wavelength. Correctly modeling this peak value as well as the required laser parameters on target can be quite complicated. In this paper we present a simple way to accurately estimate Cm in advance of detailed modeling which depends only on three parameters: target atomic mass, plasma ionization state and laser wavelength. Implicitly, one also chooses the shortest practical wavelength and pulse duration considering diffraction, hardware limitations and existing laser interaction data. In many cases, these considerations lead us to choose the Nd third harmonic at 355nm and 0.1-1ns. We will support predictions with published experimental data. Our second emphasis will be to discuss laser beam arcanities: relativistic electric field intensities that occur with short high energy pulses, and typical errors in calculating intensity delivered at long range L when the Fresnel number F=a2/(Lλ) is near unity. Our third purpose will be to summarize the state of the art in efficient pulsed lasers.
        Speaker: Claude Phipps (Photonic Associates LLC)
      • 16:15
        Demonstration designs for the remediation of space debris from the International Space Station 20m
        We present here designs for a staged implementation of an orbiting debris remediation system comprised of a super-wide field-of-view telescope (EUSO) and a novel high efficiency fibre-based laser system (CAN). Initial proof of concept stages will operate from the International Space Station (ISS) where the EUSO telescope has been designed for operation as a detector of ultra-high energy cosmic rays. Equipped with 2.5 m optics and a field of view of ±30 degrees, the EUSO telescope can also be utilized for the detection of high velocity fragmentation debris in orbit near the ISS. Further tracking, characterisation and remediation is to be performed by a CAN laser system operating in tandem with the EUSO telescope. For full scale versions of both instruments, the range of the detection/removal operation can be as large as 100 km. Utilising a step-by-step approach of increasing scale we present an analysis of implementation of:1) Proof of principle demonstration of the detection by a mini-EUSO and operation of 100-fibre CAN laser technology as an ISS based prototype, 2) Technical demonstrator of debris-removal that consists of the EUSO telescope for the detection and a 10000 fibre CAN laser for tracking and impulse delivery for debris re-entry, and 3) A free-flyer mission dedicated to debris remediation in a polar orbit with the altitude near 800 km. The integration of the two novel technologies aboard the ISS amounts to a novel approach as an immediate response to the serious space debris problem with the existing platform of ISS.
        Speaker: Dr Ebisuzaki Toshikazu (RIKEN)
      • 16:35
        Mini-Euso: how to recognize a small debris from the ISS altitude. 20m
        Mini-Euso is a small telescope to be installed in the ISS by the end of 2017. It looks at earth through a UV window on the Russian segment, with two 25 cm Fresnel lenses. It is a pathfinder to Jem-Euso, pathfinder dedicated to assess the technology and look during the night at luminous events like storms, meteors, etc. It detects single photo-electrons with large dynamics. At (ISS) sunset and sunrise, the earth for 5 mn is in the dark, while ISS is sun illuminated. This makes 10 mn every 90 mn. We will observe debris just under the ISS (300 to 400 km altitude) by their brightness. They will look as a track on the focal surface. It is the first step to observe the [1-10 cm] debris, before using a satellite big enough to set a CAN laser to shoot at it.
        Speaker: Dr Philippe Gorodetzky (APC / Paris Diderot university, CNRS)
      • 16:55
        The EuPRAXIA Project - A European Plasma Accelerator 20m
        Speaker: Ralph ASSMANN
    • 17:15 17:55
      • 17:15
        150 Joules in 15 femtoseconds What would you do with a 10-PetaWatt laser ? 40m
        The APOLLON-10P laser system is a Ti:Sa based laser that will deliver 150 J in 15 femtosecond pulses (10 PW); after focusing, intensities up to 2x1022 W/cm2 will be delivered to the experimentalists. This will allow reaching the so-called “ultra-relativistic regime” where both the electrons and ions are expected to be relativistic and thus allowing for the exploration of novel matter properties. Four beams (10-PW, 1-PW, uncompressed, and a probe) can be directed into the main experimental chamber or the auxiliary chamber for particle beam – laser interactions or long focal length optics experiments. We will operate APOLLON-10P laser as a User’s Facility and we aim to attract new user communities, national and international.
        Speaker: Sophia N. CHEN (LULI, École polytechnique, CNRS, CEA, UPMC, Palaiseau, France)
      • 17:15
        A Palmtop Synchrotron-like Radiation Source 40m
        Synchrotron radiation sources are immensely useful tools for scientific researches and many practical applications. Currently, the state-of-the-art synchrotrons rely on conventional accelerators, where electrons are accelerated in a straight line and radiate in bending magnets or other insertion devices. However, these facilities are usually large and costly. Here, we propose a compact all-optical synchrotron-like radiation source based on laser-plasma acceleration either in a straight or in a curved plasma channel.
        Speaker: Dr Min Chen (Shanghai Jiao Tong University)
      • 17:15
        Amplification of short laser pulses by Stimulated Brillouin Backscattering 40m
        Since high-power laser beams are needed as a driver for future laser plasma accelerators, there is an ongoing quest for novel techniques to obtain ever higher laser intensities. In this field of research, plasma amplification has drawn much attention. This approach benefits from the fact that a plasma can sustain much higher intensities than a solid state amplifier. In a plasma, energy can be transferred from one laser pulse (pump) to another (seed), either via a high-frequency plasma electron wave (stimulated Raman backscattering, SRS) or via a low-frequency ion acoustic wave (stimulated Brillouin backscattering, SBS [1,2]). In this contribution, we report on two experiments on amplification by SBS using pump and seed pulses counterpropagating in a preformed plasma. At the ELFIE laser facility (LULI, Palaiseau, France), short (700 fs, 35 mJ) seed pulses were amplified by longer high-energy (3...6 ps, 9 J) pump pulses. The seed was amplified in the sc-SBS (strong coupling) regime where the plasma wave is a nonlinear oscillation forced by the pump laser. We observed that the process is less sensitive to competing mechanisms in this regime. We also intend to report on a recent experiment at the ARCTURUS Ti:Sapphire laser system (ILPP, Düsseldorf, Germany). Its objective is to study the process for ultrashort seed pulses (30...200 fs) which simulations have shown to be favorable for amplification [3]. For the first time, we will also investigate the lower limit for the seed pulse duration for which the seed remains short. [1] L. Lancia et al., Phys. Rev. Lett. 104, 025001 (2010) [2] C. Riconda et al., Phys. Plasmas 20, 083115 (2013) [3] S. Weber et al., Phys. Rev. Lett. 111, 055004 (2013)
        Speaker: Thomas Gangolf (ILPP, Universität Düsseldorf, 40225 Düsseldorf, Germany)
      • 17:15
        Interferometric measurement of electron density in plasma medium for laser wakefield acceleration 40m
        Recent interferometric measurement of electron density distribution of plasma driven by petawatt laser, which is important for studying laser wakefield acceleration process will be presented.
        Speaker: Dr Junghun Shin (Advanced Photonics Research Institute, Gwangju Institute of Science and Technology)
      • 17:15
        Muon-colliders by particle chirping 40m
        Abstracts Chirping is a frequently used expression in laser physics indicating separately amplifying different frequency components of the laser pulse. For muon collider we propose chirping in similar sense for particle beams creating distinct classes of particles and manipulating them specifically in order to provide possibility for creation aggregated united systems with peculiar outstanding qualities. The main ingradients of the proposed system are the following: a) Parent energy gain: 50 GeV proton beam  5 TeV LHC beam =100 times more muon/pulse b) Instead of one shot collider  100 turn synchrotron=100 times more luminosity c) jet-chirping for ,K production d) muon-chirping e) laser generated micron wide currents in streamer plasma lenses for focusing f)rapid cycling superconducting magnet switches for synchrotrons The proposed schemes: HIGGS125 factory, Colliders (0.5+0.5 and 10+10 TeV) in the present tunnels, Colliders in FCC (50+50 TeV, p-antip) tunnel, PetaelectronVolt muon beams for ICAN linear collider with calotracker detectors, the new Rutherford-experiment.
        Speaker: Prof. Gyoegy Vesztergombi (Wigner RCP)
      • 17:15
        Radiation damping effects in the interaction of cluster mediums with ultraintense laser fields 40m
        With the recent development of ultrashort high power lasers, the intensity of laser light is reaching to the regime of $10^{22-24}\:{\rm W/cm}^{2}$. Such intense laser fields can accelerate electrons to relativistic velocities within a few laser cycle period which results high energy radiation emission from the accelerated electrons in the energy level of gamma-ray. Accordingly, damping of electron motion by the radiation reaction becomes not negligible in the interaction dynamics [1]. Here, the state and/or structure of target material is a key ingredient in determining the interaction. Besides gas and solid, cluster and cluster medium, i.e., a medium composed of multi-clusters, are interested owing to its high energy absorption resulted from large ratio of surface to volume, unique optical properties, e.g., high harmonic generation and laser propagation via cluster polarization, and energetic ion generation via the Coulomb explosion of clusters [2]. These studies for laser-cluster interaction have been so far conducted mainly in the intensity regime under $10^{21}\:{\rm W/cm}^{2}$. In our previous study, we investigated the fundamental interaction with lasers and ion acceleration process in cluster mediums in the laser intensity regime of $10^{22-24}\:{\rm W/cm}^{2}$ based on the fully-relativistic particle-in-cell code EPIC3D [3]. The effects of internal clustered structure were observed in the significant enhancements of energy absorption and maximum ion energy associated with the radiation pressure acceleration in the cluster mediums compared with a uniform solid foil. Due to such a stronger interaction of ultraintense laser field with clusters than uniform plasmas, the effect of radiation reaction will be of specific importance in cluster mediums. Based on this idea, we here study the effects of radiation reaction to the interaction dynamics assuming cluster mediums with various cluster sizes irradiated by the laser of intensity regime $10^{22-23}\:{\rm W/cm}^{2}$ in the PIC simulation including the radiation reaction force [4]. By considering various cluster sizes with a fixed total mass, we found that the incident laser can penetrate into the cluster medium and accelerate a number of electrons inside of the medium that results higher energy conversion rate from laser to radiations. In the case of laser normalized amplitude $a_{0}=200$, around 35% of the input energy is converted to radiation loss in the cluster medium, which is significantly increased compared to the radiation loss rate of a spatially-uniform plasma. As a result, the energy absorption rate by electrons and then ions, which shows higher values in cluster mediums than the uniform plasma in the case where radiation reaction is not taken into account, is found to be reduced by the radiation reaction to the same level as that in the uniform plasma. Effects of the radiation damping of electrons to the ion maximum energy will be also discussed. [1] A. Zhidkov et al., Phys. Rev. Lett. 88, 185002 (2002); J. Koga, Phys. Rev. E 70, 046502 (2004). [2] Y. Fukuda et al., Phys. Rev. Lett. 103, 165002 (2009); T. Tajima et al., Phys. Plasmas 6, 3759 (1999); T. Ditmire et al., Nature 398, 489 (1999). [3] N. Iwata, Y. Kishimoto, R. Matsui and Y. Fukuda, to be published in Proc. IFSA 2013. [4] N. Iwata et al., to be published in Proc. 14th Symp. Advanced Photon Research.
        Speaker: Dr Natsumi Iwata (ILE, Osaka University)
      • 17:15
        Universal mechanism of pulse shortening and implications for the LWFA in solids 40m
        The fields to accelerate charged particles within the framework of the Laser Wake Field Acceleration scheme are created by the charge separation effect in the laser pulsed field. To intensify the field and boost the acceleration rate, one may increase the plasma density (say, toward the solid state density) as long as the charge separation in denser plasmas results in higher fields. However, the use of denser plasma would require shorter laser pulse to produce the wake field wave of a shorter wavelength. That is why we discuss the ways to produce the shorter laser pulse, which, particularly can be achieved with the recently proposed laser pulse compression scheme [1]. The scheme is designed to reach the laser pulse as short as the single wave period (i.e. of duration of about 1 fs) combined with an extremely high focused intensity amounting to 10$^{24}$ W/cm$^2$. Particle-in-cell simulations give us a hint that the further compression toward $\sim$ 1 as durations may be achieved in reflection of such pulses from plasma targets of proper density. In the presentation we will discuss the model related to this pulse compression. It accounts for the effect of phase difference on the wave interference, which poses the important restriction on the pulse compression capability, as long as the waves reflected, for example, from the front and rear sides of a plasma foil, may extend the reflected pulse and/or reduce its amplitude, due to their interference. [1] G. Mourou, S. Mironov, E. Khazanov, A. Sergeev, Eur. Phys. J. Special Topics 223 (2014) 1181
        Speaker: Natalia Naumova (LOA, ENSTA ParisTech, CNRS, Ecole polytechnique, Université Paris-Saclay, 91762 Palaiseau, France)
    • 18:45 23:00
      DINER 4h 15m
  • Friday, 16 October
    • 08:30 09:10
      Bridging High Energy Physics and Space technology (NEXT)
      • 08:30
        Applications of filaments generated by high-power spaceborne lasers 20m
        A novel concept for global atmosphere monitoring was studied and will be presented. The concept relies on laser pulse filamentation in the atmosphere from a powerful laser embarked in an Earth-orbiting satellite. Filamentation leads to white light generation. Light reflected by different species of air at different altitudes is collected by a space-borne receiver and analyzed. The concept is tantamount to a multispectral LIDAR technique to measure pollutants in the atmosphere from space. Combined with a controllable altitude for the generation filaments, it provides a global solution with broad degree of freedom to analyze the dependence of the density of air constituents upon altitude, time and location. The white light source generated by filamentation covers a large number of absorption bands of air species and atmospheric pollutants while the spaceborne moving source enables to globally monitor the atmosphere. Numerical simulation of femtosecond filamentation in the atmosphere provides a range of laser parameters such as power, pulse duration and initial beam diameter for generation of white light at predefined height. Numerical investigation also provided the spectral width of generated supercontinuum which spans from 300 nm to 1200 nm. Another potential application of spaceborne high-power laser will be discussed, relying on the fact that filamentation is accompanied by plasma generation and local heating of air. This effect, combined with the long range propagation property of filaments can be used to generate waveguides in the atmosphere so as to facilitate high-average-power beam propagation through air and increase laser beam pointing stability. This radiation can be further collected and focused onto space debris to deorbit them. Waveguides can be designed in various ways so as to guide beams of different wavelengths, fired from the surface of the earth. The proposed applications of spaceborne laser filamentation require a high efficiency, lightweight, durable laser which could produce high energy and high repetition femtosecond pulses. The ICAN laser concept fulfills these requirements.
        Speaker: Dr Vytautas Jukna (LOA, ENSTA-ParisTech, CNRS, Ecole Polytechnique, Université Paris Saclay, 91762 Palaiseau cedex, France)
      • 08:50
        Lasing in the sky 20m
        A short and intense IR femtosecond laser pulse launched in atmosphere undergoes filamentation, with the emergence of a long thin plasma column in the wake of the laser pulse. We will show that this plasma column acts as an efficient optical amplifier in the UV and can form a cavity-less laser. The origin of this optical gain will be discussed. Depending on the polarization of the femtosecond laser pulse (circular or linear), stimulated emission stems from an inversion of population either between excited and ground triplet states of the neutral nitrogen molecule or between excited and ground states of the singly ionized nitrogen molecule. The mechanism responsible for population inversion in both cases will be discussed.
        Speaker: Prof. Andre Mysyrowicz (LOA ENSTA école polytechnique Palaiseau)
    • 09:10 12:00
      Acceleration with micro and nanostructures
      • 09:10
        Nano-Engineered Xtal (Crystal) Technology for Accelerator Revolution (NEXTAR) - Feasibility Study of TeV/m Nano-Crystal Acceleration 20m
        The development of high gradient acceleration and tight phase-space control of high power beams is a key element for future lepton and hadron colliders since the increasing demands for higher energy and luminosity significantly raise costs of modern HEP facilities. Atomic channels in crystals are known to consist of 10 – 100 V/Å potential barriers capable of guiding and collimating a high energy beam and continuously focused acceleration with exceptionally high gradients (TeV/m). However, channels in natural crystals are only angstrom-size and physically vulnerable to high energy interactions and these factors have prevented crystals from being applied to high power accelerators. Synthetically manipulated nano-crystals (in particular those based on carbon composites, such as carbon-nanotube (CNT) and graphene) have a large degree of dimensional flexibility and thermomechanical strength. Such features could be suitable for high gradient acceleration and high intensity beam control. Nano-channels of the synthetic crystals can accept a few orders of magnitude larger phase-space volume of channeled particles with much higher thermal tolerance than natural crystals. Our preliminary simulations identified an energy gain and focusing effect of plasma wakefields in an effective nano-channel model. However, it is important to experimentally identify a wakefield generated in a quasi-ionized crystalline solid, when it is optically or electronically pumped by a high energy source (x-ray laser or particle-beam), and to examine the properties such as amplitude, phase-velocity, de-phasing length and so on. The experimental verification is a prerequisite before the idea is further explored. This report will present simulation results and discuss our plan on feasible experiments to test the nanostructured crystals at a high energy physics (HEP) facility (e.g. Fermilab Accelerator Science and Technology (FAST)) and possible collaborations on the opportunity.
        Speaker: Prof. YOUNG-MIN SHIN (Northern Illinois University)
      • 09:30
        Propagation of ultra-intense laser pulses in near-critical plasmas: depletion mechanisms 20m
        Although the weakly nonlinear regime of LWFA is known to be the optimal for reaching the highest possible energy of electrons for a laser pulse of given energy, the capabilities of upcoming grand laser systems will provide the possibility of running highly nonlinear regimes of laser pulse propagation in underdense or near-critical plasmas. These regimes could open new routes towards various applications, including the reaching of unprecedentedly high electron currents and the creation of unique gamma and X-ray sources. Here we show that such regimes can be implemented with external guiding for a relatively long distance of propagation. This provides a way for the stable transformation of laser energy into several channels, including the kinetic energy of a large number of electrons and their incoherent emission. We use an extended PIC model that takes into account all the relevant physics and reveal the relative contribution of various channels of energy depletion for the laser pulse. In particular, our study shows that up to intensities of the order of (at least) $10^{26} W/cm^2$ a stable structure, similar to the one known for LWFA, is formed and propagates through the plasma for a long distance. This is despite the fact that the high intensity of the laser pulse triggers a number of new mechanisms of energy depletion, which we investigate in our study. Firstly, the electrons, being pushed by the leading edge of the laser pulse, not only take away the kinetic energy gained due to the light pressure, but also transfer a relatively large portion of energy into incoherent emissions. Secondly, some of these electrons are found to be captured by the effect of radiation reaction trapping in the front part of the laser pulse. Apart from this, the electromagnetic energy of the laser pulse is redistributed within the bubble in a sophisticated way that includes irregular detachment and the deviation to the sides of new small bubble-like structures (non-linear solitons) formed at the front edge. This process, however, does setup but for different intensities. We perform a systematic analysis by accounting separately for the channels by not break the main structure quickly. To reveal the relative contribution of the various channels of energy depletion we perform simulations for a particular realistic which energy can leave the system, and switching on and off different basic physical phenomena (radiation reaction and ion motion), as well as using different models for their description (a stochastic QED-based routine and a classical radiation reaction force).
        Speaker: Arkady Gonoskov (Chalmers University of Technology)
      • 09:50
        Generation of an ultrashort monoenergetic proton bunch in an instability-free regime by a single-cycle laser pulse 20m
        Prompted by the possibility1 to produce high energy single cycle laser pulse in the tens of PW intensity (1024W=cm2), we have investigated laser-matter interaction in the few optical cycle and ultra relativistic intensity regime. A particularly interesting instability-free regime for ion production was revealed leading to the efficient production of short(fs) monoenergetic ions with a peak energy greater than GeV. Of paramount importance, the interaction is absent of RTI and hole boring plaguing techniques as Target Normal Sheath Acceleration (TNSA) and Radiation Pressure Acceleration (RPA).
        Speaker: Xuequing YAN (State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education, CAPT, Peking University, Beijing, China, 100871)
      • 10:10
      • 10:40
        Dynamics of electric field during high intensity laser pulses with snow whiskers 20m
        Dynamics of electric field during high intensity laser pulses with snow whiskers M. Botton1, A. Zigler1, E. Schleiffer1, D. Gordon2, P. Sprangle2, Z. Henis1 1. Racah Institute of Physics, The Hebrew University, Jerusalem, 91904, Israel 2. Plasma Physics Division, Naval Research Lab, Washington, D.C., 20375, USA Abstract Enhanced acceleration of protons to high energy by relatively modest high power ultra-short laser pulses, interacting with snow micro-structured targets was recently demonstrated. A notably increased proton energy was attributed to a combination of three mechanisms: First is localized enhancement of the laser field intensity near the tip of one micron size snow whisker, inducing electron cloud formation near the tip. Second is the mass-limited like phenomenon, and third is the Coulomb explosion of the positively charged whisker, adding longer time acceleration. All these mechanisms are function of the shape, dimensions and local density profile of the snow whisker, the geometry of the irradiation and the laser intensity. Particle in cell simulations were conducted to study protons, electrons and oxygen ions acceleration from snow whiskers with different sizes, aspect ratios, planar and ellipsoid shapes, from step-like solid density to under-dense plasma with smooth Gaussian density gradients for different laser intensities. A strong correlation is found between the charged particles motion and the spatial and temporal evolution of the charge separation electric field. At the early stages of their motion, the electric field is dominated by the electrons motion and follows their distribution, showing larger values around the tip of the whisker, and associated with the spherically expanding electrons. After the protons start moving, the electric field has a double shell structure, associated with the front of the accelerated protons - outer shell, and oxygen ions - inner shell. At late times this motion occurs at approximately constant velocity. The temporal behavior of the peak of the electric field was compared to an analytic model of plasma expansion.
        Speaker: arie zigler (Hebrew University)
      • 11:00
        Vacuum laser acceleration of relativistic electrons using plasma mirror injectors 20m
        Vacuum Laser Acceleration (VLA) [1] is a promising method for accelerating electrons to very high energy in very short distances. The method is appealing because of its conceptual simplicity and most fundamental nature: electrons interact with an intense laser field in vacuum and exchange energy with the field. With intensities exceeding $10^{19} W/cm^{2}$, the laser electric field reaches >10 TV/m, providing the highest fields that can be produced in the laboratory. These enormous fields can then be used to accelerate charged particles with extreme accelerating gradients. While the theoretical literature on VLA has been extremely prolific, there have been no experimental results so far showing unambiguously the acceleration of electrons to relativistic energies by VLA. This is probably because VLA occurs efficiently only for electrons injected in the laser field with specific initial conditions that are extremely challenging to fulfill experimentally. Indeed, in order to stay in phase with the laser field, electrons need to have initial velocities close to c along the laser propagation axis. In addition, they should start interacting with the intense laser beam already close to its spatial and temporal maxima, and even be injected at appropriate phases of this field. Thus, the proper injection of electrons into the intense laser field has proven difficult to solve experimentally. We will show how by using a plasma mirror, we have been able to solve this long-standing problem. A plasma mirror is an overdense plasma with a very sharp density gradient ($L<\lambda/10$) at its front surface [2]. The interaction of an intense laser pulse with such a plasma mirror leads to the production of energetic electrons at specific phases of the field and collinear to the reflected laser pulse. This interaction provides electrons with initial conditions that are ideal for injecting electron into the reflected field and permits efficient vacuum laser acceleration. Our experimental results clearly discriminate for the first time electrons that have explored many laser cycles and thus experienced ponderomotive scattering, from those that have remained within a given laser period and been efficiently accelerated by VLA. Simulations show that these VLA electrons surf a single laser cycle and gain about 10 MeV in a 80 µm distance. The accelerated charge in the 10 MeV beam is very large: up to 3 nC, showing that this process is quite efficient [3]. In this talk, we will explain the concept and the physics of plasma mirrors as electron injectors. We will show how our experimental results can be clearly interpreted in terms of VLA, providing clear evidence that an electron beam with a large charge can be efficiently accelerated to relativistic energies using this process. REFERENCES 1. E. Esarey et al., Phys. Rev. E 52, 5443 (1995) 2. C. Thaury et al., Nat. Phys. 3, 424 (2007) 3. M. Thévenet et al., submitted for publication
        Speaker: Fabien Quere (CEA)
      • 11:20
        Plasma structures for coherent acceleration 20m
        By using our full electromagnetic relativistic particle-in-cell (PIC) simulation code equipped with ionisation module, we simulate the laser fields dynamics in the periodic structures of different materials. We study how the dynamic ionization influences the field structure.
        Speaker: Alexander Pukhov (University of Dusseldorf)
      • 11:40
        Dielectric Laser Acceleration of Sub-relativistic Electrons – Towards Realization of an Accelerator on a Chip 20m
        We report on recent experimental progress in the field of dielectric laser acceleration (DLA) of electrons, with a focus on our recent results at sub-relativistic energies. This novel concept utilizes principles established in RF technology but scales down the size of the analogous accelerator components by several orders of magnitude, driven by the high achievable acceleration gradients of several GeV/m at dielectric structures excited with laser light. Our research aims towards the development and demonstration of individual parts of the accelerator infrastructure (laser-driven accelerating, diagnostic, steering and focusing components) and towards the multi-stage operation necessary for achieving high energy gains. We will also discuss the broader scope and current status of the field of dielectric laser acceleration.
        Speaker: Dr Kozak Martin (Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Staudtstr. 1, D-91058 Erlangen, Germany)
    • 12:00 16:50
      Frontiers in laser technology
      • 12:00
        Apollon multi-PW laser facility: Presentation and Scientific Program 20m
        Designed in collaboration between CNRS, CEA, Ecole Polytechnique, the Paris Saclay University and their industrial partners, the upcoming "Apollon" laser facility on the plateau of Saclay, South of Paris (France), is expected to reach for the first the 10 Petawatt power level. At the heart of the opportunities offered by the facility will be compact particle acceleration, in particular testing new schemes for future generations of high-energy accelerators, but also a wide range of other applications, from the generation of highly energetic radiation that can complement what is produced on the latest generation X-ray sources, or the production of high-energy-density matter states, allowing e.g. laboratory investigation of extreme astrophysical phenomena. The facility will comprise two short-pulse laser beams (F1 at 10 PW nominal, with a first step at 5 PW, andF2 at 1 Pw, both at 15 fs duration), a chirped laser pulse (up to 250 J, 1 ns) and a probe beam (up to 100 mJ, 20fs minimum), all available at a repetition rate of one shot per minute at full power and in stable manner. Two target areas will be serviced by these laser beams in alternate mode: LFA, dedicated to long-focal length focusing experiments, and SFA, dedicated to short-focusing (f/2.5) and development of the highest intensity on target. The facility will be open to users following the current access mode of the LULI facilities (ELFIE, LULI2000), i.e. to Europe as well as international users.
        Speaker: S.N. CHEN (LULI, École polytechnique, CNRS, CEA, UPMC, Palaiseau, France)
      • 12:20
        LUNCH 1h 40m
      • 14:00
        Development of 10 GeV electron acceleration with 4-PW laser 20m
        Laser-plasma interactions in relativistic regime brought a tremendous advancements of compact particle accelerators and radiation sources. Rapid progresses of ultashort high-power laser technology has reached to output power of PW, which can provide a chance to explore new regime of relativistic laser-plasma interactions. We have developed two PW Ti:Sapphire laser beamlines with the peak powers of 1.0 PW and 1.5 PW [1], which were succesfully applied to generate a 3-GeV electron [2] and 93-MeV proton beams [3]. Here, we will present the progresses of electron acceleration with PW laser pulses and the plans for development of 10 GeV electron beam driven by 4 PW laser pulses. We are in the progress of upgrading our PW laser to reach 4-PW peak power with 20-fs pulse duration and 80-J energy, which can provide a chance to accelerate electron beam beyond 10 GeV. The developmen of laser-plasma accelerator beyond 10 GeV will advance the applications of laser-plasma electron accelerators to high-energy gamma-ray generation, pair production and laser-based photo-nuclear physics. [1] J. H. Sung, S. K. Lee, T. J. Yu, T. M. Jeong, and J. Lee, Opt. Lett. 35, 3021 (2010). [2] H. T. Kim, K. H. Pae, H. J. Cha, I J. Kim, T. J. Yu, J. H. Sung, S. K. Lee, T. M. Jeong, and J. Lee, Phys. Rev. Lett. 111, 165002 (2013). [3] I J. Kim et al., Arxiv 1411.5734.
        Speaker: Prof. Chang Hee NAM (Center for Relativistic Laser Science, Institute for Basic Science)
      • 14:20
        Coherent Amplification network (CAN) : taking high energy physics and space physics to a new level 20m
        1 - Introduction and context For the last decade, ytterbium-doped fiber amplifiers have been demonstrating their strong potential to amplify ultrashort pulses at high average powers, close to the kilowatt level [2]. Indeed, the low quantum defect of the ytterbium ion and the high surface-to-volume ratio of the fiber geometry provide a very good thermal handling, allowing the amplification of pulse trains up to several tens of MHz. In addition, the fiber technology presents numerous practical advantages such as compactness, robustness and ease-of-use, which bring strong benefits to most of the laser sys- tems requiring high average powers. However, the counterpart related to the fiber geometry is the tight confinement of the laser beam inside the fiber core over long interaction lengths. This leads to strong accumulations of nonlinear effects, especially Self-Phase Modulation (SPM) encountered in the femtosecond regime, which distort the output pulse temporal profile and limit the maximum peak power achievable. Large Mode Area (LMA) fibers, exhibiting Mode Field Diameters (MFD) ranging typically from ∼ 30 µm (bendable) to ∼ 80 µm (rod-type), allow to reach higher energies while preserving the temporal pulse quality. Along with Chirped-Pulse Amplification (CPA), energies up to the mJ and peak powers beyond the GW levels have been demonstrated from a single fiber amplifier [3]. However, scaling the core size in LMA fibers inevitably leads to multimode operation that affects the spatial profile of the beam. Moreover, even in a quasi-single-mode operation, the generation of high average powers in very large mode area fibers as rod-type fibers leads to modal in- stabilities, evolving in a manner quite difficult to predict. During the last few years, novel fiber amplification architectures involving Coherent Beam Combining (CBC) have demonstrated new records in terms of pulse energy and peak power. Although CBC presents a high potential to scale the energy of femtosecond fiber systems, historical Ti:Sa systems are still the only ones that can provide very high peak powers and short pulse durations. However, the performances of a larger scale CBC system involving femtosecond fiber amplifiers could theoretically compete with these systems, providing in addition multi-kHz repetition rates and much higher wall plug efficiencies. These last features could allow femtosecond sources to address new applications, mostly in the high intensity regime as particle beam acceleration, XUV photolithography, nuclear waste transmutation, or space debris removal [4]. To reach the high peak/average powers and efficiency requirements for these applications, the CBC of thousands of fiber amplifiers was envisaged [5]. Active phase locking, which is compatible with a large number of fibers, involves phase detection, calculation of the correction and compensation of the phase of each amplifier [6]. To explore the coherent combining of thousands of fiber amplifiers, a massively scalable phase measurement technique must be developed. In this context, the Ecole Polytechnique and Thales now collaborate through the XCAN project in order to explore, demonstrate and improve the efficiency and reliability of femtosecond laser systems based on the CBC of a scalable number of fiber amplifiers. 2 - The XCAN design The principle of CBC is to divide a single source into several independent channels, each with a dedicated fiber amplifier. The outputs of the N amplified channels are coherently combined in free space into one single beam, which carries N times the power of a single fiber. Therefore, coherent fiber beam combining architecture is a parallel amplification architecture. In the femtosecond regime, the Coherent Amplification Network (CAN) laser is inserted inside a CPA architecture. After a master oscillator, the femtosecond pulse is chirped to decrease the peak power before amplification. The power of the chirped pulse is then divided into N fibers. Each fiber is amplified. In the so-called tiled aperture configuration, the outputs of the N fibers are arranged in an array and collimated in the near field of the laser output. The N beamlets then interfere constructively in the far field, and give a bright central lobe, when all the beams are in phase. The output beam then propagate in free space, is compressed and recombined whereas a small fraction of the total field is sampled and redirected to a phase-matching feedback loop. The XCAN architecture is made of 61 channels, allowing an hexagonal arrangement of the beams that provides higher combination efficiency compared to a classical square layout. Due to phase noise perturbations induced by fiber amplifiers, the phase of each fiber needs to be precisely controlled. Phase fluctuations caused by intrinsic perturbations of the fiber amplifiers and environment changes such as temperature or pressure have a bandwidth in the range of the 100 Hz [6]. Moreover, in the case of femtosecond, the difference of length between all the fibers has to be corrected so that all the pulses arrive at the same time. Controlling both the phase and the delay of the pulses is then compulsory for this CAN architecture [7]. An interferometric technique, based on the analysis of an interference pattern of the output beams recorded on a camera, performs a collective phase measurement of the beams from a single image. This method is a promising candidate towards very large channel counts applications, and the largest reported number of combined fiber amplifiers uses this technique [8]. Moreover, this phase control architecture is highly scalable and could combined thousands of fibers with conventional hardware at bandwidth compatible with fiber amplifiers noise [9]. However, previous experiments were realized in continuous regime. In the XCAN project, this interferometric technique will be adapted to femtosecond regime integrating pulse synchronization measurement and control. The performances expected are set to 10 mJ pulses of 350 fs duration at 50 kHz repetition rate, whose realization is to be expected in the next three years. The system will be all-fibered from the oscillator to the final combination step, which is necessarily performed in free space. The use of a tiled-aperture combination geometry sets some practical constraints in order to avoid any congestion along the combined beam propagation path. In particular, forward pumping of the power amplifiers is preferred at first, and the use of bendable LMA fibers of moderate MFD allows to lighten the congestion constraints at the fiber entrances. These two arguments tends to lower the output energy available from a single channel for a given nonlinearity level. Once the XCAN architecture will be demonstrated, efforts will be made on investigating backward-pumped rod-type fibers in such a geometry to scale further the CBC potential. Moreover, parallel studies on beam shaping will be followed in order to optimize the pupil filling and increase the achievable maximum combination efficiency. References 1. G.A. Mourou, D. Hulin and A. Galvanauskas, ¡◦ The road to High Peak Power and High Average Power Laser: Coherent Amplification Network (CAN), AIP Conference Proceedings, Third International Conference on Superstrong Fields in Plasmas, 827, Dimitri Batani and Maurizio Lontano, 152 (2006) 2. T. Eidam, S. Hanf, E. Seise, T.V. Andersen, T. Gabler, Opt. Lett. 35, 94 (2010) 3. F. Ro¨ser, T. Eidam, J. Rothhardt, O. Schmidt, D.N. Schimpf, J. Limpert, A. Tu¨nnermann, Opt. Lett. 32, 3495 (2007) 4. C. Jauregui, J. Limpert, A. Tu¨nnermann, Nature Photonics 7, 861 (2013) 5. G. Mourou, B. Brocklesby, T. Tajima, J. Limpert, Nature Photonics 7, 258 (2013) 6. T.Y. Fan, IEEE J. Sel. Top. Quantum Electron. 11, 567 (2005) 7. L. Daniault, M. Hanna, L. Lombard, Y. Zaouter, E. Mottay, D. Goular, P. Bourdon, F. Druon, P. Georges, Opt. Lett. 36, 621 (2011) 8. J. Bourderionnet, C. Bellanger, J. Primot, A. Brignon, Opt. Express 19, 17053 (2011) 9. M. Antier, J. Bourderionnet, C. Larat, E. Lallier, J. primot, A. Brignon, IEEE J. 20, 5 (2014)
        Speaker: Dr Louis Daniault (Ecole Polytechnique)
      • 14:40
        Laser-plasma amplification of short laser pulses based on ion waves 20m
        Plasma-based laser amplification has been recently receiving much attention. Using a plasma as an amplifying medium opens new possibilities in manipulating laser light at high intensities since it overcomes solid state based technology that is limited by the damage threshold of optical components. A plasma amplifier is based on the interaction and energy exchange between a long moderate-intensity pump pulse providing the energy, and a short less energetic seed pulse that is amplified. This energy redirection is made possible due to the coupling that is fulfilled by the response of the plasma medium. A scheme based on the Brillouin Backscattering mechanism in the regime of strong coupling will be presented, with experimental demonstration that this mechanism is suited to amplify a 400 fs, few mJ seed pulse. It allows for absolute amplification in plasma, showing that such plasma amplifiers indeed hold promises. Finally, perspectives in investigating on the role of higher frequency electron modes of the plasma will be discussed as they can (especially at short seed durations) contribute to the amplification process in a mode-mixing scheme.
        Speaker: Julien Fuchs
      • 15:00
        COFFEE BREAK 20m
      • 15:20
        Towards exawatt pulses using advanced methods in stimulated Raman backscattering 20m
        The maximum extractable energy of conventional chirped pulse amplification (CPA) laser technology is limited by the damage threshold of laser components, which is in the order of $10^{12} W/cm^2$. Amplification by Stimulated Raman Back Scattering (SRBS) in plasma has the potential to overcome these limitations allowing theoretically maximum intensities of $10^{16}$ – $10^{17} W/cm^2$, which is the prerequisite for realizing exawatt-class laser systems. Amplification is achieved when two counter propagating beams overlap in plasma is such a way that a plasma density echelon is produced by the beat wave to allow scattering of the “pump” pulse into a “seed” pulse. To achieve the highest possible conversion efficiency it is necessary to overcome a few bottlenecks, and present solutions which also work for not always ideal operation conditions of the laser system: i) The bandwidth of linear growth SRBS is limited and does not support the generation of very short pulses. However with Vlaslov Code simulation we have identified conditions for the laser pulses (chirp and intensity) and the plasma parameters to provide broad band amplification, The predictions have been verified in an experiment showing amplification over a spectral range sufficient for generating sub-20 fs pulses ii) To counteract instabilities in the plasma, the red-shifted seed pulses need to surpass certain energy levels. In another series of experiments we employed Raman up-shifting in a molecular gas with Bessel shaped beam for realizing energetic red-shifted seed pulses with an excellent beam quality, and is very robust against fluctuation of the energy and beam profile of the laser iii) Amplification with SRBS has been demonstrated mainly with pump pulse energies in the multi-J range. As it has been discussed in the literature, a large volume uniform plasma is necessary for further increasing the pump pulse In a recent experimental campaign at PHELIX/GSI we studied the possibility of energy scaling of SRBS. Special emphasis was laid onto the gas target and the role of an additional ionizing pulse to create a uniform plasma, also for a fluctuating laser. Preliminary results of the energy scaling experiment with fast ionization control at PHELIX/GSI will be presented at the conference. Summing up, SRBS is a promising route for the generation of exawatt laser pulses. As it will be shown in our contribution, a few of the problems have been solved, but further efforts are necessary to realize the next generation high intensity laser systems.
        Speaker: Björn Landgraf
      • 15:40
        Single cycle and Exawatt Lasers 20m
        Efficient multistage compression of petawatt laser pulses, such as those becoming available at laser facilities around the world, holds the promise of exawatt, X-ray pulses. A shorter route to the generation of Schwinger intensities with current day technology is now envisioned with the capability of producing high energy radiation and particle beams of extremely short, sub-attosecond timescales. The energies and timescales involved are far from traditional laser regimes and offer a new intersection of laser technology with the study of the structure of vacuum and numerous applications to subatomic physics. With this vision in mind, the two-stages of the planned petawatt pulse compression scheme shall be presented and the early work studying their feasibility discussed.
        Speaker: Dr Jonathan WHEELER (Ecole Polytechnique - IZEST)
      • 16:00
        The "Nexawatt": A Path to Exawatt Capability Enabled Fusion Laser Technology 30m
        Existing high peak power, chirped pulse amplification (CPA) systems are limited by intensity dependent damage of final optics, i.e. intensity-depended damage of final compressor gratings and downstream focusing optics. For kJ-class pulse production these systems are further limited in the amount of energy that can be safely extracted from the laser amplifier by the limited duration of the stretched pulse during amplification. The duration of this pulse is ultimately set by the physical delay that can be produced by the finite size of the compressor gratings. For 1 meter gratings used in the highest energy CPA systems today, this stretched pulse duration is of order 1.5 ns and the extracted energy from the amplifier is less than 1/10th of that potentially available. This presentation will introduce the concept of chirped beam amplification (CBA) and will show how the combination of chirped pulse amplification and chirped beam amplification can be used to effectively create a 20-ns duration pulse prior to amplification and compression and in doing so enable the full extraction of the stored energy from a modern, Nd:Glass laser beam line such as those that are part of the 192 beam, 2MJ, fusion laser system at the National Ignition Facility. Chirped pulse juxtaposed with beam amplification (CPJBA) creates the potential for production of 20 kJ, sub-100-fs pulses from single laser amplifier. The novel compressor architecture required to recompress these chirped beam pulses will be described as well as techniques for creation of diffraction limited output, circumvention of final optics damage and application of these systems to dipole focusing architectures. The "NIF exawatt" or "Nexawatt" architecture requires only existing fabrication technologies and optics operated below established damage limits. This architecture is fully compatible with high efficiency diode-pumped laser architectures that have been developed for laser inertial fusion power plant concepts. Sub-scale versions these fusion energy laser concepts are currently being constructed and demonstrated at the 100's of J scale. Such lasers will ultimately produce from a single amplifier, diffraction-limited, >10 kJ, <100-fs pulses at repetition rates of >10 Hz and with wall plug efficiencies of > 20%. As such, the "Nexawatt" short pulse amplification architecture presents new opportunities for practical extension of laser-wakefield field accelerator schemes to well beyond 100 GeV in a single stage at high overall electrical efficiency.
        Speaker: Dr Christopher Barty (Lawrence Livermore National Laboratory)
    • 16:50 17:00
      Conclusion 10m