HiPER The proposed European Laser-Driven Fusion Facility is actually being developed as an ESFRI Project with collaboration of many different European (but also international) laboratories. The project was upgraded to the present state of two clear steps in proposing funding for next phase development to arrive finally to a Inertial Fusion Power Plant. In addition to aspect in laser, target (both defining and manufacturing), injection and tracking, CHAMBER design is a key aspect in this new phase in which the project has entered. An overview of the state of art of different options of Chamber, their necessary assessments with the safety and environment considerations will be presented together with proposals for fusion technology experiments. 1. Introduction The HiPER project final goal is to design, after these first years inside the frame of the European ESFRI program, an Inertial Fusion Facility based on Fast Ignition concept where demonstration of ignition and gain (in the range of 44 compression beams giving 200 kJ in 5 ns and a PW beam line of 70 kJ in 10 ps) will be combined with a complementary exploration of longer term research in Inertial Fusion Energy and different spin-off in basic physics, astrophysics, nuclear physics, high density matter, etc. To get those purposes several steps are being envisioned. From already general criteria we will need to consider aspects such as: i) withstand earthquakes; ii) be resistant to debris, radiation, shrapnel and neutrons effects from experiments; iii) maintain deep vacuum and ultra-freezing environments required for experiments; iv) accommodate the many diagnostic instruments, beam lines, and associated optics and equipment; v) maintain as low as possible the activation of the materials component of the chamber in order to induce the minimum radioactivity and make easy the operation and maintenance; vi) take into account tritium permeation, diffusion, contamination in that phase of operation. We will present the main criteria when designing the main chamber: fabrication (thickness of shell, welding...); the installation of penetration in the chamber and vacuum leak checking; chamber shielding and uncertainties in it; and the chamber survey and alignment for location of optics and laser ports. From calculations available in different type of targets we are extracting data of energy yields from debris, X-rays, and neutrons, also considering the different energy spectra. The capsule design will be critical together with the calculation of those numbers, but even with no actual final design for fast ignition, CHAMBER research is imperative. A potential low fraction of X-rays could come from the fact that targets are fully ionized at the end of the burn and bremmstrahlung is the dominant emission. An important difference is also the angular dependence of X-rays, and particles emission (this aspect could be very critical for fast ignition conical targets). A key aspect will appear when considering the repetitive operation in

The production of energetic (multi-GeV) heavy ion beams by acceleration of ultra-thin foils through the application of radiation pressure to a self-generated, imperfect plasma mirror (photon absorption probability {\eta} finite) is studied. To evaluate the foil dynamics a relativistic model was developed for a constant and relativistic invariant value of the phenomenological parameter {\eta}. The achievable efficiency of kinetic energy transfer to the matter has been evaluated as function of the parameters involved ({\eta}, the aimed average foil velocity in unit of the light speed {\beta}, etc.). The expected collimation degree for the generated ion beams, the associated energy range, the self-consistency of the model in view of the {\eta} finite value and the survival to R-T instability were evaluated for initially thin material disks.

Unconventional, promising approaches to intertial fusion energy (IFE) proposed and studied in the framework of IFE keep-in-touch activity at Frascati EURATOM-ENEA Association will be reconsidered for the present more advanced technological context associated to a planned large installations scenario. Then the possibility to generate laser-produced fast heavy-ion sources (e.g., Bi ions, tens GeV) will be explored taking as reference results obtained in the FIGEX experiment scaled toward thermonuclear regimes. A possible dimensioning of such sources will be also given as well as the associated laser requirements.

Ion beams must satisfy quite stringent conditions in terms of power density and total energy for fast-ignition applications. Fast ions are also expected suitable to assist ignition in the injected entropy approach to ICF[1-3]. As demonstrated by the Fast Ions Generation EXperiment (FIGEX) [4], collimated multi-MeV/nucleon ion beams can be generated in the CAM mode (Controlled Amount of Matter) by laser irradiation of ultra-thin causally-isolated disks. Target design and preparatory work was made at ENEA[5]. The experiment, supported by the Associazione EURATOM-ENEA sulla Fusione, was made at CLF of Rutherford Appleton Laboratory. Target design and experimental results are discussed in terms of features of the generated ion beam, with particular regard to possible applications of the method.

In several experiments, faster ions were produced from the backside of solid targets irradiated by powerful laser pulses. The ion acceleration was considered due to the negative electrostatic sheath formed on the backside of the target (TNSA), or to the expansion wave starting at the backside surface, or to the expansion wave and to its embedded electrostatic rarefaction shock. In this experiment, ions have been generated by transferring energy to a controlled amount of mass before the target become transparent by gas dynamic expansion (controlled amount of mass mode (CAM)). The targets used were thin transparent disks causally isolated from the holder to trim down, during the interaction process, unwanted effects due to the surrounding parts. Two kinds of target corresponding to a different set of parameters were designed (LARGE and SMALL). Both targets were conceived to survive, in the actual contrast conditions, to the low power pulse forerunning the giant laser pulse, bigger margin but lower performances being assigned to LARGE. For comparison standard square foils under the same focusing conditions, were also studied (LARGE-LIKE and SMALL-LIKE irradiation).

We present the results of experiments on the interaction of laser radiation with low-density porous targets performed on the ABC facility at the ENEA Research Centre (Frascati, Italy). Porous plastic targets with densities of 5 and 20 mg cm-3 were irradiated by a focused neodymium-laser beam at the fundamental frequency (λ = 1.054 μm) at a radiation intensity of 1013 W cm-2 at the target. The beam was preliminarily allowed to pass through an optical system intended to spatially smooth the radiation intensity over the beam cross section. The use a smoothed beam was important to discover in the plasma and in the accelerated dense material the features related to the porous structure of the target under conditions which rule out the effect of the inhomogeneities of the heating beam itself. The spatial plasma structure in the laser beam—target interaction region and at the rear side of the target were investigated by using optical schlieren plasma photography. The time dependent transmission of the laser radiation through the target was also investigated by imaging the target in transmitted radiation to a properly masked photodiode.

Irradiation of solid targets by short laser pulses can result in a production of fast ions. In this paper, two production modes are discussed: the controlled amount of matter mode (CAM) and the open amount of matter mode (OAM). The CAM mode is based on laser energy transfer to a controlled amount of matter before the target becomes transparent to the laser light due to the gas-dynamical expansion. For the CAM mode, it is presented a model that allows determining the target parameters, the focusing conditions, and the pulse duration as a function of the laser pulse energy, of the aimed energy per nucleon and of the energy transfer efficiency to the target. The conditions to be this mode experimentally addressed are indicated. The OAM mode relies on the irradiation of a target with large ion content by a short laser pulse; in this case, a small amount of fast ions is emitted from the rear and lateral sides of the target depending on the laser pulse and focusing parameters. For this mode, observed in several experiments, a theoretical discussion is presented. Special attention is devoted to the target normal sheath acceleration (TNSA) and to expansion wave (EW) mechanisms. The EW process is discussed in the framework of a two-temperature isothermal model and some peculiar hydrodynamic processes are discussed.

The present 28th ECLIM in Rome is a continuation of the series of conferences that started in Frascati, Italy in 1966. These conferences deal with the interdisciplinary subjects of laser interaction with matter, related not only to basic science but also to a wide range of applications. ECLIM is an independent scientific conference, free of any institutional or political influence, keeping science without boundaries.

Targets of the "Laser Greenhouse" (GH) type are very promising ones for direct laser compression(1). The key feature of this type of targets is the presence of a layer of low-density volume structured medium, which surrounds a thermonuclear cell and acts as the laser radiation absorber. Some methods to achieve highly symmetrical compression of these targets by small (e.g. two) number of laser beams (or beam clusters) have been presented earlier(2). Simulations of compression of targets for total laser pulse energy of 100 kJ and 2.1 MJ have proved, that this type of targets allows one to achieve combustion and effective bum. In the paper we introduce the results of 2D simulations of some processes, which are specific to this design of targets. The attention is paid to the problem of symmetry of compression. We also have performed calculations of neutron yield of the target designed for compression by two beams with full energy of 2.6 kJ, and series of 2D simulations to model some microscopic processes in the absorber. The experiments on compression of the targets at energy level of 2.6 kJ can be performed on a number of present laser installations.

The Laboratory for ICF Physics and Technology of the CR ENEA in Frascati is currently performed activity for the development for potential drivers for Inertial Fusion Energy. The system being considered for a possible future development is a diode-pumped neodymium glass laser (HAP-4) dimensioned to deliver 100/spl divide/400 J in pulses of 1/spl divide/5 ns at a rate of 1/spl divide/10 Hz. The name of this system is ABCD, after ABC, the name the two beam, flash lamp pumped laser currently used for experiments on Inertial Fusion Energy (IFE) in Frascati. The main ABCD amplifier architecture is based on a 5-pass cavity that includes a system of 7 sub-amplifiers formed by assembling two modules.

The possibility of efficient and symmetric compression of a target with a low-density structured absorber by a few laser beams is considered. An equation of state is proposed for a porous medium, which takes into account the special features of the absorption of high-power nanosecond laser pulses. The open version of this target is shown to allow the use of ordinary Gaussian beams, requiring no special profiling of the absorber surface. The conditions are defined under which such targets can be compressed efficiently by only two laser beams (or beam clusters). Simulations show that for a 2.1-MJ laser pulse, a seven-fold gain for the target under study is achieved.

Evaluations of the energy for thermonuclear ignition of a compressed deuterium-tritium mixture contaminated by a high- Z material are presented. Mixing at the atomic level is considered and the results are given as a function of the contaminant fraction. The reference situation is that of cone-focused fast ignition (CFFI). The numerical 2 D simulations for this study were performed by a Lagrangian 2 D hydrocode that includes real matter EoS, real matter opacity coefficients, and packages for finite-range energy deposition by reaction products and the relative in-flight reactions. A simple estimate is presented for the effects of high- Z material blobs on the ignition energy (macroscopic mixing). Possible sources for fuel contamination in CFFI are discussed.

The possibility of efficient and symmetric compression of a target with a low-density structured absorber by a few laser beams is considered. An equation of state is proposed for a porous medium, which takes into account the special features of the absorption of high-power nanosecond laser pulses. The open version of this target is shown to allow the use of ordinary Gaussian beams, requiring no special profiling of the absorber surface. The conditions are defined under which such targets can be compressed efficiently by only two laser beams (or beam clusters). Simulations show that for a 2.1-MJ laser pulse, a seven-fold gain for the target under study is achieved.

The results of a preliminary experiment on laser foam interaction performed at the ABC installation of the Associazione EURATOM-ENEA sulla Fusione are presented. Plastic foams with density of 5 - 20 mg/cm3 were irradiated with light produced from the neodymium laser of ABC (λ = 1.054 μm) and processed through a proper optical system to produce near field ISI smoothed radiation at ≈1013W/cm2 on the target. The use of a smoothed beam was essential to detect in the plasma and in the accelerated dense phase evolving features related to the target foam structure without mixing with those of the irradiating beam. Structures in the plasma corona and in the dense phase were detected by optical shadography of foam slabs. In the same experiment time-dependent transmission of laser light through slabs of foams was measured by target imaging and masking on a photodiode (bandwidth of the system 5 GHz).

The processes of the weak shock wave generation end propagation in the solid targets are studied by analytical and numerical methods. The impact of the laser pulse with wavelength lambda = 1.06 mum and the pulse intensity I = 10(10) - 10(12)W/cm(2) was considered as a wave source. The resulting wave with pressure about 1 - 100 kBar is studied in a solid medium 0.5 - 1 mm thick. The results of modeling compared with experimental data shows correctness of hydrodynamical approximations for a given problem.

This paper reports some of the studies on nonconventional ICF approaches performed at the ICF Physics and Technology Laboratory of the AEEF in Frascati, Italy. Having as reference potential difficulties associated to the conventional central spark ignition (fuel mixing) and to the usual approach to fast ignition by laser (transfer and coupling of the energy pulse, fast electrons energy tuning), we have made explorative work on possible alternatives. The performances of targets ignited near stagnation by pulses of heavy ion beams (HIB) or by macroparticle impact were previously studied. The needed driver energy, the power, and the beam quality requirements, as well as the level of synchronization the implosion and the igniting pulse have been found. More recently, to relax some requirements on the HIB beam parameters set by the previous approach, the injected entropy approach (IE) has been introduced. In this method, the conditions for spark formation are set in the final stages of the implosion, when the spark fuel size is a few times the final size at stagnation (volume a few tens of the final). Energy is injected at this time to set the spark fuel on a high adiabat. In this paper, for illustration and comparison purposes, some relevant results we previously obtained for near-stagnation ignition are first introduced and critically reviewed. The new IE method, after a short analytical introduction, is presented and illustrated by the results of extensive 2-D numerical simulations. The considered cases refer to imploding cylinders of finite length. As required by this approach, one or two opposing beams axially injected additional energy, whereas the acceleration stage of the cylindrical low-entropy implosion was assumed driven by a different driver. Heavy ion beams, soft X-rays (SXR), and laser generated light ion beams were considered as vectors for the entropy injection. Issues related to the feasibility of these generators are discussed. The study was made for various initial conditions leading to different ignition modes and burn propagation. The most recent results on the injected entropy method to the ignition of high gain targets are included.

The most recent results on the injected entropy method to the ignition of high gain targets are presented. The base of the method is the ignition of high gain targets by energy injection in the final stages of the fuel implosion. In this scheme most of the energy needed to form the ignition spark is still provided by the work of the imploding target itself, as in the standard ICF scheme. The injected energy is used to set on a higher adiabat that small portion of the fuel destined to become the ignition spark. After a short analytical introduction to the method, the result of extensive numerical simulations by a 2D code are presented. The considered cases refer to imploding cylinders of finite length. The additional energy was injected axially by one or two opposing beams, whereas the acceleration stage of the cylindrical low-entropy implosion was assumed driven by a different driver. Heavy ion beams, soft x-rays and laser generated light ion beams were considered as vectors for the entropy injection. Issues related to the feasibility of these generators are discussed. The study was made for various initial conditions leading to different ignition modes and burn propagation.

The direct (fast) ignition of the compressed DT and DD fuels of ICF targets by the light ions of laser-produced plasma flows is proposed. Plasma flow, with necessary parameters, is generated as result of laser-produced thermal explosion of a thin separate foil, placed near ICF target. The foil thickness must be less than energy deposition length of the fast electrons inside the produced plasma. It ensures the volume explosion of such a target-generator along all of its thickness in the process of multiple fast electron crossings of the foil. In such a condition the light ions energy may be controlled at the optimal laser energy coupling in the target-generator. Direct ignition method by laser-produced plasma flow is more preferable in comparison with the method by laser-produced fast electrons beam on the reason that the complex procedure of a boring of ICF target plasma doesn 't need.