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[en] A high-yield, room temperature, double-shell target design using a Nd : glass laser driver at the fundamental frequency 1ω is developed for hybrid inertial fusion-fission energy generation (Moses et al 2009 Fusion Sci. Technol. 56 547). The associated 4-10x fission energy gain relaxes the gain requirements of the fusion driver, enabling the prospect of a volume-ignition target with high thermonuclear burn fraction, simplified (1ω) laser operations from a quasi-impulsive power history, room temperature fielding, minimal shock-timing requirements and reduced risk of plasma-mediated laser backscatter with a vacuum hohlraum.
[en] Complete text of publication follows. The recently launched HiPER (High Power laser Energy Research facility) project is a European initiative to offer a credible way to demonstrate the possibility of opening up Inertial Fusion Energy as a commercial process for energy generation. One baseline target design includes cone geometries and there are significant technical and scientific challenges in the production of these cones to the required specification in the required numbers for the facility. There are also a large number of research projects that are investigating cone performance and are re-designing the cone to have novel features and specifications. We review the production of a number of different geometries and also the ability to mass produce such items.
[en] The first wall armour for the reactor chamber of HiPER will have to face short energy pulses of 5 to 20 MJ mostly in the form of x-rays and charged particles at a repetition rate of 5-10 Hz. Armour material and chamber dimensions have to be chosen to avoid/minimize damage to the chamber, ensuring the proper functioning of the facility during its planned lifetime. The maximum energy fluence that the armour can withstand without risk of failure, is determined by temporal and spatial deposition of the radiation energy inside the material. In this paper, simulations on the thermal effect of the radiation-armour interaction are carried out with an increasing definition of the temporal and spatial deposition of energy to prove their influence on the final results. These calculations will lead us to present the first values of the thermo-mechanical behaviour of the tungsten armour designed for the HiPER project under a shock ignition target of 48 MJ. The results will show that only the crossing of the plasticity limit in the first few micrometres might be a threat after thousands of shots for the survivability of the armour.
[en] Complete text of publication follows. In practice, there are many serious obstacles complicating the classical direct drive IFE scheme - even putting in doubts its practical feasibility. Among the most serious ones is the insufficient predictability of the injected pellets's trajectories resulting from their expected interactions with remnants of previous fusion explosions due to the considered 5-10 Hz repetition rate. This is one of the reasons why the indirect drive scheme - despite its higher demand on laser energy - seems to be currently considered a more serious IFE candidate. The corresponding hohlraum targets are by three orders of magnitude heavier compared to their direct drive counterparts, thus allowing for more reliable prediction of their trajectories. In this contribution, a recent progress achieved in the stimulated Brillouin scattering (SBS) phase conjugating mirror (PCM) based inertial fusion energy (IFE) approach proposed recently as an alternative to the IFE classical approach mentioned above, will be reported. By taking care of automatic self-navigation of every individual laser beam on injected pellets with no need for any final optics adjustment, this technology is of a particular importance to the direct drive scheme. Conceptual design of one typical laser driver will be shown and its features discussed. Three distinct stages of this process can be identified: (i) at the right moment (determined by careful tracking), when the injected pellet is approaching its best interaction position, low energy seeding laser pulse (glint) is sent to illuminate the pellet; (ii) reflected seeding laser pulse is collected by the focusing optics and amplified on its way to the SBS PCM cell; (iii) amplified pulse is reflected by the SBS PCM cell, amplified once again on its return, converted to higher harmonic (being now above threshold of this non-linear process), and automatically aimed at the moving pellet by the target displacement compensation system for its final high power pellet irradiation. This is a completely passive system having its optical components appropriately designed for every individual channel taking advantage of their index of refraction dependence on the wavelength. In comparison with the earlier design, an upgraded scheme was developed with the low energy illumination laser beam entering the reactor chamber through the same entrance window as used by the corresponding high energy irradiation laser beam. The pellet survival conditions in the period between its low energy illumination and subsequent high energy irradiation were studied and the upper limits on the allowed energies absorbed for both DD and DT fuels were found. Results of experimental verification of this improved design will be reported. In these experiments for the first time a complete setup including the pellet (realized by the static steel ball) was employed. Issues of the pellets with cones and parasitic effects of perpendicular SBS will be also discussed. Acknowledgements. This research was supported by International Atomic Energy Agency Research Contracts No. 13781 and 13758.
[en] An analysis of the design space available to laser fusion power plants has been carried out, in terms of design key parameters such as target gain, laser energy and laser repetition rate, the number of fusion react ion chambers, and plant size. The design windows of economically attractive laser fusion plants is identified with the constraints of key design parameters and the cost conditions. Especially, for achieving high repetition rate lasers, we have proposed and designed a diode-pumped solid-state laser driver which consists of water-cooled zig-zag path slab amplifiers. (author)
[en] During the next ten years the National Ignition Facility (NIF) will be completed and substantial fusion gains are likely to be achieved with the NIF megajoule class solid state laser. A facility very similar to NIF is being constructed by the French nuclear weapons program. Technological advances promise to make ICF increasingly attractive as a practical energy source. These advances include very high gain targets (e.g., the fast ignitor), petawatt lasers, diode pumped solid state lasers, and advanced heavy ion accelerators. Beyond the next ten years an experimental inertial fusion (IF) reactor will be needed to take the major step from NIF to a practical fusion power plant. A key question: how is this IF experimental reactor to be funded? A 100 MWe scale IF reactor could produce several kilograms per year of low cost tritium for DOE Defense Programs. Tritium produced by competing fission reactor and accelerator/spallation options is estimated to cost more than one hundred million dollars per kilogram, much more than the cost of tritium produced by a fusion reactor. Tritium production provides a defense funded option for IF's next step beyond NIF
[en] Three-dimensional simulations of plasma liner implosion using smoothed particle hydrodynamics (SPH) code have been performed. The study of spherical plasma liner implosions with velocities ∼10-60 km/s is important for plasma liner-driven magneto-inertial fusion (MIF). This concept uses a dynamically fanned plasma shell with a spherically converging velocity to drive a magnetized fuel to ignition. In this work, we have simulated plasma liner implosion without the effect of target. The mass of the plasma liner is taken to be ∼0.4 mg and the velocity is ∼60 km/s. The sensitivity of implosion pressure (typically of the order of 0.5 GPa) on plasma non-uniformity in the liner for different initial velocities is analyzed. We have compared our simulation results with published simulation and experimental results. Good agreement in results are found. We also found that the effect of thermal conduction and radiation are insignificant during the implosion phase. This paper describes the details of the simulated system, SPH model and the comparison of our 3D results with various published results. (author)