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Fast Decompression Of Ultra‐Thin Targets For High‐Energy, High‐Contrast Laser Pulses

P. Antici, J. Fuchs, E. Lefebvre, L. Gremillet, E. Brambrink, P. Audebert, and H. Pépin

AIP Conf. Proc. 1209, pp. 3-6; doi:http://dx.doi.org/10.1063/1.3326315 (4 pages)

Online Publication Date: 3 February 2010

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In the laser‐plasma interaction process, for ultra‐high temporal contrast laser pulses, experimental measurements show that reducing the thickness of solid targets increases the laser‐to‐fast electrons energy conversion and the hot electron temperature. We have performed an experiment using the LULI 100 TW laser facility working in the chirped pulse amplification (CPA) mode at a wavelength λ₀ = 1.057 μm, pulse duration 320 fs, laser spot size FWHM ∼6 μm and intensity ∼ 1×10¹⁸ W/cm² in which the laser pulses were temporal‐contrast enhanced by the use of two plasma mirrors. Shots were performed on Si₃N₄ aluminum coated targets of thickness 30 nm to 500 nm. Spectra of the laser‐accelerated electrons were recorded with a spectrometer and are compared to PIC simulations performed with the CALDER code. The simulations allow an insight into the electron heating process during the laser‐matter interaction.

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52.38.Mf	Laser ablation
42.60.Da	Resonators, cavities, amplifiers, arrays, and rings
52.57.Bc	Target design and fabrication
52.38.Kd	Laser-plasma acceleration of electrons and ions

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Laser Induced Nuclear Fusion, LINF, In Muonic Molecules With Ultrashort Super Intense Laser Fields

Andre D. Bandrauk and Gennady K. Paramonov

AIP Conf. Proc. 1209, pp. 7-10; doi:http://dx.doi.org/10.1063/1.3326326 (4 pages)

Online Publication Date: 3 February 2010

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Muonium molecules where muons replace electrons increase the stability of molecules to ionization at superhigh intensities, I>10²⁰ W/cm². We show furthermore from numerical simulations that in the nonsymmetric series, pdu, dtu, ptu, the permanent dipole moments can be used to enhance LINF, Laser Induced Nuclear Fusion by laser induced recollision of the light nucleus with the heavier nucleus.

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52.57.Bc	Target design and fabrication
23.40.-s	β decay; double β decay; electron and muon capture
23.70.+j	Heavy-particle decay

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Simulation of particle acceleration in the PLASMONX project

Carlo Benedetti

AIP Conf. Proc. 1209, pp. 11-14; doi:http://dx.doi.org/10.1063/1.3326304 (4 pages)

Online Publication Date: 3 February 2010

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In this paper I will present some numerical studies and parameter scans performed with the electromagnetic, rela‐tivistic, fully‐self consistent particle‐in‐cell (PIC) code ALaDyn (Acceleration by LAser and DYNamics of charged particles), concerning electron acceleration via plasma waves in the framework of the INFN‐PLASMONX (PLASma acceleration and MONochromatic X‐ray production) project. In particular I will focus on the modelling of the SITE (Self Injection Test Experiment) which will be a relevant part of the commissioning of the FLAME laser. Some issues related to the quality of the accelerated bunch will be discussed.

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52.38.Mf	Laser ablation
29.20.Ej	Linear accelerators
52.65.Rr	Particle-in-cell method

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Towards Laser‐Driven, Quasi‐Monochromatic Ion Bunches via Ultrathin Targets Nano‐Structuring?

S. Betti, A. Giulietti, D. Giulietti, L. A. Gizzi, M. Vaselli, C. A. Cecchetti, A. Gamucci, P. Koester, L. Labate, N. Pathak, T. Levato, A. A. Andreev, T. Ceccotti, P. Martin, and P. Monot

AIP Conf. Proc. 1209, pp. 15-18; doi:http://dx.doi.org/10.1063/1.3326308 (4 pages)

Online Publication Date: 3 February 2010

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The conditions for achieving the laser acceleration of quasi‐monochromatic ion bunches with present‐day, fs laser systems are theoretically discussed. The study suggests the possibility of achieving quasi‐monochromaticity via irradiation of double‐layer, nano‐structured foils and the conjecture is numerically confirmed by means of two dimensional, Particle‐In‐Cell (PIC) simulations. A feasible setup in order to experimentally validate this approach is thus proposed.

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52.38.Mf	Laser ablation
52.35.Fp	Electrostatic waves and oscillations (e.g., ion-acoustic waves)
42.70.Hj	Laser materials
52.40.Fd	Plasma interactions with antennas; plasma-filled waveguides

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High‐Charge, Multi‐MeV Electron Bunches Accelerated in Moderate Laser‐Plasma Interaction Regime

C. A. Cecchetti, S. Betti, A. Gamucci, A. Giulietti, D. Giulietti, P. Koester, L. Labate, N. Patak, F. Vittori, O. Ciricosta, and L. A. Gizzi

AIP Conf. Proc. 1209, pp. 19-22; doi:http://dx.doi.org/10.1063/1.3326309 (4 pages)

Online Publication Date: 3 February 2010

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Experiments [1], and simulations[2] have shown that quasi‐monoenergetic electron bunches can be accelerated from the background electron plasma population up to relativistic energies. Theoretical work [3] indicated that with a proper choice of laser, plasma, and injection parameters the acceleration of electron bunches with small energy spread and short bunch length can occur in moderate intensity regime. Here we present the results of an experiment on electron acceleration carried out at the IPCF‐CNR’s Intense Laser Irradiation Laboratory in Pisa [4], within a wide national collaboration leaded by INFN named PLASMONX [5]. High‐charge, multi‐MeV electron bunches were accelerated in moderated intensity regime by focusing the laser beam on a laminar gaseous target produced by a supersonic gas‐jet. The laser‐gas interaction was studied via interferometry, and Thomson scattering while the electron bunches were detected and characterised using a phosphor screen coupled with a magnetic spectrometer or a dosimetric detector. In some cases highly collimated electron bunches with moderate energy spread were observed, while the generation of high‐charge, MeV energies electron bunches were obtained with high reproducibility for each gases tested.

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52.50.Dg	Plasma sources
52.38.Mf	Laser ablation
29.20.Ej	Linear accelerators
42.65.Re	Ultrafast processes; optical pulse generation and pulse compression

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BLISS@CNR‐Pisa: a flexible laser for small scale test experiments on fusion oriented physics

O. Ciricosta, L. Labate, S. Atzeni, A. Barbini, D. Batani, R. Benocci, F. Cornolti, M. Galimberti, P. Gaudio, D. Giulietti, L. A. Gizzi, S. Martellucci, M. Richetta, A. Schiavi, M. Vaselli, et al.

AIP Conf. Proc. 1209, pp. 23-26; doi:http://dx.doi.org/10.1063/1.3326310 (4 pages)

Online Publication Date: 3 February 2010

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By the year 2010 a new laser will be operational at the CNR Campus in Pisa. The laser system will deliver two beams each one providing 1‐ns 50‐joule pulses of high optical quality and full control of phase. The major feature of the system is its spectral and time shape flexibility ranging from narrowband single mode operation to broadband operation with pulse tailoring. According to previous experiments and recent simulations, these features could critically determine the laser‐pellet coupling in the different approaches to laser fusion. The physics involved in the different coupling processes is still not fully investigated experimentally. The BLISS laser, combined with the rest of the ILIL experimental facility, including ultrafast optical probing, time resolved optical X‐ray diagnostics and particle detection could contribute to this investigation with ad hoc small scale experiments. The main features of the innovative BLISS laser front end for broadband operation are shown, together with the amplification chain and the main features of the experimental installation. Data from simulations providing a useful input for future experiments are also presented. BLISS is expected to contribute to the preparatory phase of the large scale European HiPER project.

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52.38.Mf	Laser ablation
52.38.Ph	X-ray, γ-ray, and particle generation
52.38.Kd	Laser-plasma acceleration of electrons and ions
52.35.Qz	Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

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A Theory of Laser Induced Nuclear Reaction in Single Atoms

F. H. M. Faisal and C. Donner

AIP Conf. Proc. 1209, pp. 27-30; doi:http://dx.doi.org/10.1063/1.3326311 (4 pages)

Online Publication Date: 3 February 2010

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An “electron‐bridge” mechanism of nuclear reaction in an atom or ion by ultra‐intense laser fields is presented. A preliminary estimate of the intensity dependence of the rate of disintegration reaction of deuteron nucleus in deuterium atom is made for 800 nm laser fields. For intensities below 5×10²¹ W/cm², the rate of disintegration by the “electron‐bridge” mechanism is found to be small, but it rises sharply and becomes large already for ≈ 10²² W/cm².

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42.65.Re	Ultrafast processes; optical pulse generation and pulse compression
25.45.Hi	Transfer reactions
52.38.Mf	Laser ablation
02.30.Sa	Functional analysis

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High Electron Doses from a GW Laser Interacting with Solid Aluminum Targets

C. Fonseca, C. Mendez, C. Ruiz, F. Fernandez, and L. Roso

AIP Conf. Proc. 1209, pp. 31-34; doi:http://dx.doi.org/10.1063/1.3326312 (4 pages)

Online Publication Date: 3 February 2010

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We report dose measurements of electrons emitted in the interaction of a kHz laser of 1 GW with a solid target of aluminium. By using a microscope objective we are able to obtain high intensities I ∼ 10¹⁶ W/cm⁻², with less of 1 mJ before the objective. For p‐polarized laser pulses and an oblique incidence of 45 degrees, we report high doses of electrons in the specular reflection direction. Energy spectra of the electrons show a bi‐Maxwellian distribution with characteristic energy of T = 13.8 and 60 keV. These distributions are obtained using an array of TLDs placed at different distances from the source. We take advantage of the stopping power of air to estimate the energy distribution.

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52.38.Mf	Laser ablation
42.68.Mj	Scattering, polarization
43.58.Ls	Acoustical lenses and microscopes
78.60.Kn	Thermoluminescence

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The New Fast Ignitor Oriented Target Area in the Vulcan Laser at the CLF

M. Galimberti, S. Bandyopadhyay, R. Bickerton, S. Blake, C. Burton, R. Clarke, J. ollier, V. Dubrovsky, M. Dunne, A. Frackiewicz, S. Hancock, R. Heathcote, C. Hernandez‐Gomez, P. Holligan, R. J. Hooke, et al.

AIP Conf. Proc. 1209, pp. 35-38; doi:http://dx.doi.org/10.1063/1.3326313 (4 pages)

Online Publication Date: 3 February 2010

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During the course of 2008 we have conducted an upgrade to one of the short pulse beam lines of the Vulcan laser and one of the target areas the Target Area West, at the Central Laser Facility . The aim of this upgrade was to provide to the plasma physics communities a facility capable to perform fast ignitor oriented experiments. The final specification of that target area will be to provide 500J at 10ps combined with 6 long pulse beams, with a total energy of 1.5 KJ, and another 100J 1ps pulse. Nevertheless, the target area was planned also to be flexible and it will be able to perform dual short pulse interaction, 100 J 1 ps per each beam. Some experiments have been already been conducted in this target area, with different configurations and laser requirements. We present here the state of this new target area and its capabilities.

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52.38.Mf	Laser ablation
42.65.Re	Ultrafast processes; optical pulse generation and pulse compression
29.40.Vj	Calorimeters

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Laser‐IORT: a laser‐driven source of relativistic electrons suitable for Intra‐Operative Radiation Therapy of tumors

A. Gamucci, N. Bourgeois, T. Ceccotti, X. Davoine, S. Dobosz, P. D’Oliveira, M. Galimberti, J. Galy, A. Giulietti, D. Giulietti, L. A. Gizzi, D. J. Hamilton, L. Labate, E. Lefebvre, J. R. Marquès, et al.

AIP Conf. Proc. 1209, pp. 39-42; doi:http://dx.doi.org/10.1063/1.3326314 (4 pages)

Online Publication Date: 3 February 2010

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In a recent experiment [1] a high efficiency regime of stable electron acceleration to kinetic energies ranging from 10 to 40 MeV has been achieved. The main parameters of the electron bunches are comparable with those of bunches provided by commercial Radio‐Frequency based Linacs currently used in Hospitals for Intra‐Operative Radiation Therapy (IORT). IORT is an emerging technique applied in operating theaters during the surgical treatment of tumors. Performances and structure of a potential laser‐driven Hospital accelerator are compared in detail with the ones of several commercial devices. A number of possible advantages of the laser based technique are also discussed.

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87.56.bg	Radioactive sources
52.38.Mf	Laser ablation
29.20.Ba	Electrostatic accelerators
87.19.xj	Cancer

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Phase‐Contrast Imaging of Nanostructures with Incoherent Femtosecond Laser Driven Soft X‐Ray Source

Sergei Gasilov, Tatiana Pikuz, Anatoly Faenov, Yuji Fukuda, Masaki Kando, Hideyuki Kotaki, Takayuki Homma, Keigo Kawase, Takashi Kameshima, Igor Skobelev, Hiroyuki Daido, Yoshiaki Kato, and Sergei Bulanov

AIP Conf. Proc. 1209, pp. 43-46; doi:http://dx.doi.org/10.1063/1.3326316 (4 pages)

Online Publication Date: 3 February 2010

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Application of polychromatic (1.5–15 nm) soft X‐ray emission of a spatially large (>0.1 mm) bright femtosecond laser driven plasma source for propagation based phase contrast imaging of nanometer thick foils and biological samples is considered. Diffraction and phase contrast effects increased quality and contrast of the experimental images, registered by LiF crystal X‐ray detector with submicron resolution.

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52.38.Mf	Laser ablation
52.38.Ph	X-ray, γ-ray, and particle generation
42.65.Re	Ultrafast processes; optical pulse generation and pulse compression
32.30.Rj	X-ray spectra

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Proton Radiography of a Laser‐Driven Cylindrical Implosion

R. Jafer, L. Volpe, D. Batani, M. Koenig, S. Baton, E. Brambrink, F. Perez, F. Dorchies, J. J. Santos, C. Fourment, S. Hulin, P. Nicolai, B. Vauzour, K. Lancaster, M. Galimberti, et al.

AIP Conf. Proc. 1209, pp. 47-50; doi:http://dx.doi.org/10.1063/1.3326317 (4 pages)

Online Publication Date: 3 February 2010

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A recent experiment was performed at the Rutherford Appleton Laboratory (UK) to study fast electron propagation in cylindrically compressed targets, a subject of interest for fast ignition. This experiment was performed in the framework of the experimental road map of the Hiper project (the European High Power laser Energy Research facility Project). In this experiment, protons accelerated by a pecosecond laser pulse have been used to radiograph a 220 μm‐diameter, 20 μm‐wall cylinder filled with 0.1 g∕cc foam, imploded with ∼200 J of green laser light in 4 symmetrically incident beams of pulse length 1 ns. Point projection proton backlighting was used to measure the compression degree as well as the stagnation time. Results were compared to those from hard X‐ray radiography. Finally, Monte Carlo simulations of proton propagation in the cold and in the compressed targets allowed a detailed comparison with 2D numerical hydro simulations.

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87.59.B-	Radiography
52.58.Hm	Heavy-ion inertial confinement
52.65.Pp	Monte Carlo methods
87.64.kd	X-ray and EXAFS

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Low‐Divergent, Energetic Electron Beams from Ultra‐Thin Foils

T. Kluge, M. Bussmann, S. A. Gaillard, K. A. Flippo, D. C. Gautier, B. Gall, T. Lockard, M. E. Lowenstern, J. E. Mucino, Y. Sentoku, K. Zeil, S. D. Kraft, U. Schramm, T. E. Cowan, and R. Sauerbrey

AIP Conf. Proc. 1209, pp. 51-54; doi:http://dx.doi.org/10.1063/1.3326318 (4 pages)

Online Publication Date: 3 February 2010

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In this work we report on a recent experiment where an energetic, well‐collimated electron beam has been observed in the laser direction following the short pulse (600 fs) high‐intensity laser interaction with ultra‐thin solid foils. These results are in contrast to the typical low‐energy divergent electrons accompanying ions in the target normal direction usually seen in solid targets. We observe the foils being preheated and expanded by ASE prior to the main pulse which makes them transparent for the laser. The experimental evidence as well as 2D particle‐in‐cell simulations suggest the excitation of a wakefield that can accelerate electrons to energies of tens of MeV.

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52.38.Mf	Laser ablation
52.38.Ph	X-ray, γ-ray, and particle generation
52.40.Fd	Plasma interactions with antennas; plasma-filled waveguides
52.65.Rr	Particle-in-cell method

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Measurements of Self‐Generated Magnetic Fields Influence on Electron Heat Conduction in Dense Plasmas

L. Lancia, C. Fourment, M. Nakatsutsumi, S. Hulin, S. Bastiani‐Ceccotti, J. J. Santos, M. Gauthier, M. Le Gloahec, J.‐L. Feugeas, Ph. Nicolaï, G. Schurtz, P. Audebert, J. Fuchs, and M. Migliorati

AIP Conf. Proc. 1209, pp. 55-57; doi:http://dx.doi.org/10.1063/1.3326319 (3 pages)

Online Publication Date: 3 February 2010

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Proton radiography measurements of self generated magnetic fields developing in long pulse (ns), high‐power laser plasma interactions were employed to investigate the influence of these fields on the propagation of heat flow in dense plasmas. During the experiments, the heat wave propagation speed was measured simultaneously with the fields. These two coupled measurements could give an insight on the limitations of current numerical models of heat transport. They suggest that non locality of heat transport and diffusion of magnetic fields are important to model correctly the interaction.

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52.25.Kn	Thermodynamics of plasmas
52.75.Fk	Magnetohydrodynamic generators and thermionic convertors; plasma diodes
44.40.+a	Thermal radiation
52.38.Ph	X-ray, γ-ray, and particle generation

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Fabrication of 3‐μm diameter pin hole array (PHA) on thick W substrates

T. Levato, N. C. Pathak, C. A. Cecchetti, O. Ciricosta, P. Koester, L. Labate, A. Giulietti, D. Giulietti, F. De Angelis, E. Di Fabrizio, P. Delogu, and L. A. Gizzi

AIP Conf. Proc. 1209, pp. 59-62; doi:http://dx.doi.org/10.1063/1.3326320 (4 pages)

Online Publication Date: 3 February 2010

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Pin‐hole arrays are used for a variety of applications including, for example, X‐ray imaging of laser‐plasmas for fusion relevant studies [1]. More recently, a novel X‐ray imaging technique has been proposed (this conference L. A. Gizzi et al.) within the High Power Laser Energy Research Facility (HiPER) to obtain spectrally resolved X‐ray imaging [2] using single photon detection [3]. This technique requires a large number of images or, alternatively, large arrays of pin‐holes, possibly with very small diameter (≪10 μm) [4]. In view of this, a technique was implemented for the fabrication of large arrays of pin‐holes in thick metal substrates. Here we report on the optimizations of the laser‐matter interaction process to obtain high aspect ratio cylinder‐like pin‐hole on heavy metal substrate by using a frequency‐doubled Ti:Sa femtosecond laser pulses operating at 10 Hz. The influence of an air breakdown and a (ns)prepulse, on the drilled pin‐hole, is showed by means of SEM images both for surface effects and internal quality of the channels, with evidence of micro and nano‐sized structures. The holes drilled at an intensity just below the laser breakdown threshold for plasma creation in air, have an internal diameter of about 3 μm on a W substrate of 70 μm thickness, a micro‐cylinder‐like shape and no detectable deviations of the axis from a straight line. Arrays of up to 800 pin‐holes were produced with the pin‐hole properties being highly stable across the array. The final X‐ray transmission is showed by using a μ‐focus X‐ray source.

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52.65.Yy	Molecular dynamics methods
52.38.Mf	Laser ablation
52.38.Ph	X-ray, γ-ray, and particle generation
68.37.Hk	Scanning electron microscopy (SEM) (including EBIC)
42.65.Re	Ultrafast processes; optical pulse generation and pulse compression

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Dynamics of Radiation Pressure Acceleration

A. Macchi, C. Benedetti, F. Pegoraro, and S. Veghini

AIP Conf. Proc. 1209, pp. 63-66; doi:http://dx.doi.org/10.1063/1.3326321 (4 pages)

Online Publication Date: 3 February 2010

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We describe recent theoretical results on Radiation Pressure Acceleration of ions by ultraintense, circularly polarized laser pulses, giving an insight on the underlying dynamics and suggestions for the development of applications. In thick targets, we show how few‐cycle pulses may generate single ion bunches in inhomogeneous density profiles. In thin targets, we present a refinement of the simple model of the accelerating mirror and a comparison of its predictions with simulation results, solving an apparent paradox.

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52.38.Mf	Laser ablation
43.25.Qp	Radiation pressure
42.65.Re	Ultrafast processes; optical pulse generation and pulse compression

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Toward a new nanoLIFT transfer process

C. Mézel, L. Hallo, A. Souquet, A. Bourgeade, J. Breil, D. Hébert, F. Guillemot, and O. Saut

AIP Conf. Proc. 1209, pp. 67-70; doi:http://dx.doi.org/10.1063/1.3326322 (4 pages)

Online Publication Date: 3 February 2010

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The Laser Induced Forward Transfer (LIFT) is a direct‐write technique used to print biological materials such as living cells or molecules. During the LIFT process, the biomaterial to be printed is deposited on a target submitted to a nanosecond laser shot, and the ejecta are collected onto a receiving substrate. Despite the several advantages of this technique (control of the propelled quantity, no spoiling of the substrate), it remains difficult to be employed due to the high sensitivity of its control parameters. Recently, Duocastella published some experimental results which exhibit the real‐time jet formation process, under conditions similar to those present in the LIFT process [1].

In the first Section, a typical experimental setup for LIFT process is presented. Then, simulations of Duocastella’s and Guillemot’s [2] experiments are carried out to model the jet formation in water when irradiated by an ultraviolet nanosecond laser pulse. The 2D axisymmetric hydrodynamic code CHIC (Code d'Hydrodynamique et d’Implosion du CELIA) [3] is used for these simulations with included equations of state (EOS) to take into account the behavior of water under standard conditions. Finally, an improvement of the LIFT technique which consists in using femtosecond lasers instead of nanosecond ones, is presented. It would allow to process smaller bioelements and to control the jet diameter, as it is directly related to the laser beam waist.

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79.20.Ds	Laser-beam impact phenomena
52.38.Mf	Laser ablation
42.50.Hz	Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift

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Study of target heating induced by fast electrons in mass limited targets

Morace Alessio, Magunov Alexander, Batani Dimitri, Redaelli Renato, Fourment Claude, Santos Joao Jorge, Malka Gerard, Boscheron Alain, Casner Alexis, Nazarov Wigen, Vinci Tommaso, Okano Yasuaki, Inubushi Yuichi, Nishimura Hiroaki, Flacco Alessandro, et al.

AIP Conf. Proc. 1209, pp. 71-74; doi:http://dx.doi.org/10.1063/1.3326323 (4 pages)

Online Publication Date: 3 February 2010

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We studied the induced plasma heating in three different kind of targets: mass limited, foam targets and large mass targets. The experiment was performed at Alisé laser facility of CEA∕CESTA. The laser system emitted a ∼1‐ps pulse with ∼10 J energy at a wavelength of ∼1 μm. Mass limited targets had three layers with thickness 10 μm C₈H₈, 1 μm C₈H₇Cl, 10 μm C₈H₈ with size 100 μm×100 μm. Detailed spectroscopic analysis of X‐rays emitted from the Cl tracer showed that it was possible to heat up the plasma mass limited targets to a temperature ∼250 eV with density ∼ 10²¹ cm⁻³. The plasma heating is only produced by fast electron transport in the target, being the 10 μm C₈H₈ overcoating thick enough to prevent any possible direct irradiation of the tracer layer even taking into account mass‐ablation due to the pre‐pulse. These results demonstrate that with mass limited targets is possible to generate a plasma heated up to several hundreds eV. It is also very important for research concerning high energy density phenomena and for fast ignition (in particular for the study of fast electrons transport and induced heating).

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52.50.Gj	Plasma heating by particle beams
52.38.Mf	Laser ablation
52.58.Hm	Heavy-ion inertial confinement
42.79.Dj	Gratings

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Anharmonic resonance in intense laser‐matter interaction: Key to collisionless absorption

P. Mulser and D. Bauer

AIP Conf. Proc. 1209, pp. 75-78; doi:http://dx.doi.org/10.1063/1.3326324 (4 pages) | Cited 1 time

Online Publication Date: 3 February 2010

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Superintense laser beam absorption in dense matter is governed by collisionless processes. During the last two decades various attempts have been made to explain the high degrees of absorption found in experiments and computer simulations and partial successes have been achieved. Here we present the model of anharmonic resonance and show its capability to explain the underlying physics of collisionless absorption in all its essential aspects, in particular the origin of the phase shift between driver field and induced current and the origin of prompt fast electrons.

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52.38.Mf	Laser ablation
52.65.Rr	Particle-in-cell method
52.20.-j	Elementary processes in plasmas

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Double Acceleration of Ions and Application in Biomaterials

Antonella Lorusso, Maria Vittoria Siciliano, Luciano Velardi, and Vincenzo Nassisi

AIP Conf. Proc. 1209, pp. 79-82; doi:http://dx.doi.org/10.1063/1.3326325 (4 pages)

Online Publication Date: 3 February 2010

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Ions of different elements were generated by laser‐induced‐plasma and accelerated by a two adjacent cavities. Therefore, the ions undergo a double acceleration imparting a maximum ion energy of 160 keV per charge state. We analyzed the extracted charge from a Cu target as a function of the accelerating voltage. At 60 kV of total accelerating voltage, the maximum current peak was of 5.3 mA. The ion flux resulted of 3.4×10¹¹ ions/cm². The normalized emittance measured by pepper pot method at 60 kV was of 0.22 π mm mrad. By means of this machine, biomedical materials as UHMWPE were implanted with carbon and titanium ions. At a total ion flux of 2×10¹⁵ ions/cm² the polyethylene surface increased its micro hardness of about 3‐hold measured by the scratch test. Considering the ion emission cone dimension, we estimated a total extracted charge per pulse of 200 nC.

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52.40.Fd	Plasma interactions with antennas; plasma-filled waveguides
52.38.Mf	Laser ablation
52.70.Ds	Electric and magnetic measurements

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Present status and future prospect of Fast Ignition Realization Experiment (FIREX) Project at ILE, Osaka

H. Nishimura, H. Azechi, K. Mima, Y. Fujimoto, S. Fujioka, H. Homma, T. Jitsuno, T. Johzaki, M. Koga, J. Kawanaka, T. Kawasaki, N. Miyanaga, H. Murakami, M. Murakami, H. Nagatomo, et al.

AIP Conf. Proc. 1209, pp. 83-86; doi:http://dx.doi.org/10.1063/1.3326327 (4 pages)

Online Publication Date: 3 February 2010

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Thermonuclear ignition and subsequent burn are key physics for achieving laser fusion. In fast ignition, a highly compressed fusion fuel generated with multiple ns‐laser beams is rapidly heated with a large energy, ps‐laser pulse in prior to core disassembly. This scheme has a high potential to achieve ignition and burn since driver energy required for high fusion gain is predicted to be about one tenth of that needed for the central ignition scheme. In Japan, Fast Ignition Realization Experiment (FIREX) project has been started to clarify the physics of energy transport and deposition in the core plasma and to demonstrate fuel temperature of above 5 keV. After the success, FIREX‐I will be followed by the second phase of the project (FIREX‐II) to demonstrate ignition and burn. LFEX laser, designed to deliver a laser pulse of 10 kJ in 10 ps, are operational and the first phase of FIREX experiments has been stated. A new target is proposed to attain dense compression of fuel and improve laser‐core coupling efficiency by adopting double‐cone structure, a low‐density inner liner, low‐Z outer coating, and Br‐doped fuel shell. In this paper, present status and near term prospects of the FIREX‐I project will be reported together with activities on target designing, laser development, and plasma diagnostics.

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52.38.Dx	Laser light absorption in plasmas (collisional, parametric, etc.)
52.50.Gj	Plasma heating by particle beams
52.25.Fi	Transport properties
52.65.Rr	Particle-in-cell method

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Target Normal Sheath Acceleration at ultrahigh intensities: a theoretical parametric investigation

Matteo Passoni, Luca Bertagna, and Alessandro Zani

AIP Conf. Proc. 1209, pp. 87-90; doi:http://dx.doi.org/10.1063/1.3326328 (4 pages)

Online Publication Date: 3 February 2010

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Ions can be effectively accelerated during the interaction of an ultra‐intense ultra‐short laser pulse irradiating a thin solid target via the so‐called Target Normal Sheath Acceleration (TNSA) mechanism. One of the crucial issues at this stage of the research is how to predict the properties of the accelerated ions, both from a fundamental point of view and in the light of foreseen applications. Thus, it is desirable to have a simple but reliable description, to be used to extrapolate current results to regimes likely to be reached in the near future, thanks to developments in laser technology. In this work we theoretically investigated the maximum ion energy achieved in TNSA as a function of laser properties, with special focus to the ranges I_L (pulse intensity) 10²⁰–10²² W/cm² and E_L (pulse energy) 1–30 J, which appear to be the most interesting for future facilities. Particular attention will be devoted to elucidate the effective dependence of the maximum ion energy on the laser intensity for different combinations of laser parameters.

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52.38.Mf	Laser ablation
52.40.Kh	Plasma sheaths
43.25.Qp	Radiation pressure

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Diode‐Pumped Yb³⁺:YLF and Yb³⁺:CaF₂ Laser Performance

Angela Pirri, Daniele Alderighi, Guido Toci, Martin Nikl, Hiroki Sato, Mauro Tonelli, and Matteo Vannini

AIP Conf. Proc. 1209, pp. 91-94; doi:http://dx.doi.org/10.1063/1.3326329 (4 pages)

Online Publication Date: 3 February 2010

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We report an extensive comparison of the laser performances of diode‐pumped Yb³⁺:YLF (30% at.) and Yb³⁺:CaF₂ (5% at.) crystals, lasing at room‐temperature and operating in two different operation modes, i.e. Continuous Wave (CW) and quasi‐CW. An in‐depth investigation of the crystals behavior by changing the pump power, clearly shows that the crystal absorption depends on the lasing conditions. Therefore, we report an unambiguous evaluation of the slope efficiency calculated taken into account the real measured crystal absorption under laser action. Finally, we present a study of problems related to thermally induced losses which are expected influencing the laser performance.

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42.55.Px	Semiconductor lasers; laser diodes
51.20.+d	Viscosity, diffusion, and thermal conductivity
61.72.J-	Point defects and defect clusters
42.65.Yj	Optical parametric oscillators and amplifiers

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Ramsey‐type spectroscopy in the XUV spectral region

A. Pirri, E. Sali, C. Corsi, M. Bellini, S. Cavalieri, and R. Eramo

AIP Conf. Proc. 1209, pp. 95-98; doi:http://dx.doi.org/10.1063/1.3326330 (4 pages)

Online Publication Date: 3 February 2010

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We report an experimental and theoretical investigation of Ramsey‐type spectroscopy with high‐order harmonic generation applied to autoionizing states of Krypton. The ionization yield, detected by an ion‐mass spectrometer, shows the characteristic quantum interference pattern. The behaviour of the fringe contrast was interpreted on the basis of a simple analytic model, which reproduces the experimental data without any free parameter.

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42.65.Ky	Frequency conversion; harmonic generation, including higher-order harmonic generation
32.10.Bi	Atomic masses, mass spectra, abundances, and isotopes
32.80.Zb	Autoionization
41.60.Ap	Synchrotron radiation
41.85.Si	Particle beam collimators, monochromators

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Observation of Quasi Mono‐Energetic Protons in Laser Spray‐Target Interaction

B. Ramakrishna, A. Andreev, M. Borghesi, D. Doria, G. Sarri, L. Ehrentraut, P. V. Nickles, W. Sandner, M. Schnürer, S. Steinke, and S. Ter‐Avetisyan

AIP Conf. Proc. 1209, pp. 99-102; doi:http://dx.doi.org/10.1063/1.3326331 (4 pages)

Online Publication Date: 3 February 2010

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Laser driven ion acceleration arises from charge separation effects caused by an ultrahigh intensity laser pulse. Limited mass targets confine the accelerated electrons within the target size and prevent the large area spreading seen in extended foil targets. Furthermore, if the target size is smaller than the laser wavelength and focal spot diameter, homogeneous heating of the target is ensured. Observation of quasi‐monoenergetic protons in the interaction of a high intensity high contrast laser pulse at 5×10¹⁹ W/cm² with 150 nm−diameter water droplets is investigated. An ensemble of such objects is formed in a spray. Quasi mono energetic proton bursts of energy E∼1.6 MeV are observed and are associated with a specific ionization and explosion dynamics of the spheres.

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52.38.Mf	Laser ablation
41.75.Fr	Electron and positron beams
29.30.Aj	Charged-particle spectrometers: electric and magnetic
29.30.Ep	Charged-particle spectroscopy
52.38.Dx	Laser light absorption in plasmas (collisional, parametric, etc.)

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