1 IF/P7-3 Theoretical and Computational Studies on Targets for Inertial Fusion Ig- nition Demonstration at the HiPER Facility * S. Atzeni 1), J.R. Davies 2), L. Hallo 3), J.J. Honrubia 4), P.H. Maire 3), M. Olazabal-Loum´ e 3), J.L. Feugeas 3), X. Ribeyre 3), A. Schiavi 1), G. Schurtz 3), J. Breil 3), Ph. Nicola¨ ı 3) 1) Universit` a di Roma “La Sapienza” and CNISM, Italy 2) Instituto Superior Tecnico, Lisbon, Portugal 3) CELIA, Universit´ e Bordeaux 1, Talence, France 4) E.T.S.I. Aeron´ auticos, Universidad Polit ´ ecnica de Madrid, Spain * e-mail contact of main author: stefano.atzeni@uniroma1.it Abstract. Recently, a European collaboration has proposed the High Power Laser Energy Research (HiPER) facility, with the primary goal of demonstrating laser driven inertial fusion fast ignition. HiPER is expected to provide 250 kJ in multiple, 3ω (wavelength λ =0.35 μm), nanosecond beams for compression and 70 kJ in 10-20 ps, 2ω beams for ignition. The baseline approach is fast ignition by laser-accelerated fast electrons; cones are considered as a means to maximize ignition laser-fuel coupling. Earlier studies led to identify an all-DT shell, with a total mass of about 0.6 mg as a reference target concept. The HiPER main pulse can compress the fuel to a peak density above 500 g/cm 3 and an areal density ρR of about 1.5 g/cm 2 . Ignition of the compressed fuel requires that relativistic electrons deposit about 20 kJ in a volume of radius of about 15 μm and depth of less than 1.2 g/cm 2 . The ignited target releases about 13 MJ. In this paper, additional analyses of this target are reported. An optimal irradiation pat- tern has been identified. The effects on fuel compression of the low-mode irradiation non-uniformities have been studied by 2D simulations and an analytical model. The scaling of the electron beam energy required for ignition (vs electron kinetic energy) has been determined by 2D fluid simulations including a 3D Monte-Carlo treatment of relativistic electrons, and agrees with a simple model. Hybrid (fluid and PIC) simulations show that beam-induced magnetic fields can reduce beam divergence. As an alternative scheme, shock ignition is studied. 2D simulations have addressed optimization of shock timing and absorbed power, means to increase laser absorption efficiency, and the interaction of the igniting shocks with a deformed fuel shell. 1. Introduction HiPER (High Power Laser for Energy Research) is a proposed facility aiming at the demon- stration of the feasiblity of fast ignition [1, 2]. We recall that fast ignition [3, 4], is an approach to inertial confinement fusion in which the stages of fuel compression and ignition are sepa- rated. The fuel is first compressed to high density by a suitable driver; the precompressed fuel is ignited by a second ultraintense driver. To achieve its goal HiPER will deliver a 3ω multi- beam pulse of about 250 kJ in about 10 ns, and a 2ω or 3ω ignition pulse of about 70 kJ in 15-20 ns. (Here ω refers to the fundamental frequency of the Nd:glass laser, with wavelength of 1.053 μm.) The baseline approach is fast ignition by laser-accelerated fast electrons; cones [4] are considered as a means to maximize ignition laser-fuel coupling. A reference fusion capsule concept for HiPER was identified by previous studies [2, 5, 6]. Capsule and laser pulse were then designed on the basis of 1-D simulations of irradiation and implosion. Care was taken to limit both plasma and hydrodynamic (Rayleigh-Taylor, RTI) instabilities. Preliminary 2D simu- lations addressed cone-guided implosion. Ignition of the precompressed fuel by electron beams was studied by 2D simulations. Sensitivity to pulse shaping and to variation of some of the igniting beam parameters was also addressed [7]. A key issue for the feasibility of the scheme is the efficient transfer of the energy ultra-intense laser beam to the hot spot, which involves laser absorption, fast electron generation, and fast electron transport and energy deposition, and