2,954 research outputs found
JASON Winter Study of the National Ignition Campaign
No full text“Esperto invitato” alla JASON Review della National Ignition Campaign, organizzata dalla MITRE Corp. per conto della NNSA (Nuclear National Security Agency) del Department of Energy, La Jolla (California), 14 – 16 gennaio 2009.
Il gruppo JASON è stato affiancato, su richiesta del Department of Energy, da sette esperti (fra cui S. Atzeni), cinque dei quali statunitensi, un inglese e un italiano (S. Atzeni)
Assessing target design robustness for shock ignition using 3D laser raytracing
No full textShock ignition (SI)[1] is a laser direct-drive Inertial Confinement Fusion scheme in which fuel compression and hot spot formation are separated. Shock ignition shows potential for high gain at laser energy below 1 MJ (see review Ref.[2]), and could be tested on present large scale facilities. We produced an analytical model for SI which allows rescaling of target and laser drive parameters starting from a given point design [3]. The goal is to redefine a laser-target configuration increasing the robustness while preserving its performance. We developed a metric for ignition margins specific to SI [4]. We report on simulations of rescaled targets using 2D hydrodynamic fluid model with 3D laser raytracing. The robustness with respect to target fabrication parameters and laser facility fluctuations will be assessed for an original reference design as well as for a rescaled target, testing the accuracy of the ignition margin predictor just developed. Work supported by the Italian MIUR project PRIN2012AY5LEL.
[1] R. Betti, C.D. Zhou et al, PRL 98, 155001 (2007)
[2] S. Atzeni, X. Ribeyre et al, Nucl. Fusion 14, 054008 (2014)
[3] S. Atzeni, A. Marocchino, A. Schiavi and G. Schurtz, New J. Phys. 15, 045004 (2013) [4] S. Atzeni, A. Marocchino, A. Schiavi, EPS Conf. proc. submitted to PPCF (2014
Comment on: "Neutron driven fusion" [Phys. Lett. A 334 (2005) 42]
No full textIt is shown that the scheme suggested by R.L. Liboff [Phys. Lett. A 334 (2005) 42] cannot lead to significant energy production by fusion reactions. A modest energy release (less than 1% of the value claimed by Liboff) is obtained from the reaction n + Li-6 -> T + He-4 + 4.78 MeV, while fusion reactions only occur at negligible rate. (c) 2005 Elsevier
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Comments on: "Neutron driven fusion" [Phys. Lett. A 334 (2005) 42]
Author(s): Atzeni, S (Atzeni, S)
Source: PHYSICS LETTERS A Volume: 342 Issue: 1-2 Pages: 196-197 DOI: 10.1016/j.physleta.2005.05.047 Published: JUL 4 2005
Times Cited: 0 (from Web of Science)
Cited References: 9 [ view related records ] Citation Map
Abstract: It is shown that the scheme suggested by R.L. Liboff [Phys. Lett. A 334 (2005) 42] cannot lead to significant energy production by fusion reactions. A modest energy release (less than 1% of the value claimed by Liboff) is obtained from the reaction n + Li-6 -> T + He-4 + 4.78 MeV, while fusion reactions only occur at negligible rate. (c) 2005 Elsevier B.V. All rights reserved
A GPU based 3D raytracing algorithm for DUED laser fusion code
No full textThese days, graphical processing units (GPUs) deliver performance comparable to that of hundreds of CPU cores. This level of performance allows certain classes of simulations to be run in-house on a standard consumer workstation, eliminating the need for a cluster. In this paper, it is shown that medium-resolution, 2D radiation hydrodynamics simulations for laser-driven inertial confinement fusion with realistic 3D laser raytracing can now be conducted on a single consumer device. A novel raytracing module has indeed been developed for the 2D Lagrangian radiation-hydro-nuclear code DUED (Atzeni 1986 Comput. Phys. Commun. 43 107–24; Atzeni et al 2005 Comput. Phys. Commun. 169 153–9) to leverage the computational power of GPUs. By employing 3D raytracing, more realistic investigations of laser-driven plasmas become feasible, with a particular focus on perturbations resulting from non-uniform laser irradiation
Perspectives for inertial fusion
No full textThe quest for demonstrating ignition and gain in Inertial Confinement Fusion [1] has come to a crucial point, where the long awaited
proof of principle of this approach to fusion still fails to arrive. We present the status of this field of research, both at the international
[2] and european level [3], focussing on the standard approach and on the new strategies in laser fusion.
The path ahead is also indicated, highlighting some of the key points in the design of a fusion reactor. The recent results obtained by
our group on target design for shock ignition [4], optimization of direct-drive irradiation schemes [5], and energy and laser
wavelength scaling models are illustrated [6].
[1] J.D. Lindl, Physics of Plasmas 2, 3933 (1995).
[2] J.D. Lindl, E.I. Moses, Physics of Plasmas 18, 050901 (2011).
[3] M. Dunne, Nature Physics 2, 2 (2006).
[4] S. Atzeni, A. Schiavi, A. Marocchino, Plasma Physics and Controlled Fusion 53, 35010 (2011).
[5] A. Schiavi, S. Atzeni, A. Marocchino, Europhysics Letters 94, 35002 (2011).
[6] S. Atzeni, A. Marocchino, A. Schiavi, G. Schurtz, New J. of Physics 15, 045004 (2013)
Cromatismo, ritmo, memoria: sulla narrativa di Sergio Atzeni
No full textSergio Atzeni’s works are many and really heterogeneous, both in style and contents. But if we dig up deeply into his texts, we discover that the currents followed by the author are always the same, and that texts that are apparently different have actually significant common aspects.Le opere di Sergio Atzeni sono numerose e molto eterogenee, sia nello stile che nei contenuti. Ma se andiamo a scavare nel profondo, ci rendiamo conto che i filoni seguiti dall’autore sono sempre gli stessi, e che esiti testuali apparentemente distinti hanno in realtà importanti aspetti in comune
Shock ignition targets: gain and robustness vs ignition threshold factor
No full textShock ignition
[1] is a laser direct-drive inertial confinement fusion scheme, in
which the stages of compression and hot spot formation are partly
separated. The hot spot is created at the end of the implosion by
a converging shock driven by a final “spike” of the laser pulse.
Several shock-ignition target concepts have been proposed and relevant
gain curves computed (see, e.g. [2]). Here, we consider both
pure-DT targets and more facility-relevant targets with plastic ablator.
The investigation is conducted with 1D and 2D hydrodynamic simulations.We determine ignition threshold factors ITF’s (and their
dependence on laser pulse parameters) by means of 1D simulations
[3]. 2D simulations indicate that robustness to long-scale perturbations
increases with ITF. Gain curves (gain vs laser energy), for
different ITF’s, are generated using 1D simulations.
∗Work partially supported by Sapienza Project C26A15YTMA,
Sapienza 2016 (n. 257584), Eurofusion Project AWP17-ENR-IFECEA-
01.
†Student.
‡Student.
1R. Betti et al., Phys. Rev. Lett. 98, 155001 (2007).
2S. Atzeni et al., Nucl. Fusion 54, 054008 (2014).
3S. Atzeni, A. Marocchino, and A. Schiavi, Plasma Phys. Controll.
Fusion 57, 014022 (2015)
The relational model is dead‚ SQL is dead‚ and I don’t feel so good myself
No full textWe report the opinions expressed by well-known database researchers on the future of the relational model and SQL during a panel at the International Workshop on Non-Conventional Data Access (NoCoDa 2012), held in Florence, Italy in October 2012 in conjunction with the 31st International Conference on Conceptual Modeling. The panelists include: Paolo Atzeni (Università Roma Tre, Italy), Umeshwar Dayal (HP Labs, USA), Christian S. Jensen (Aarhus University, Denmark), and Sudha Ram (University of Arizona, USA). Quotations from movies are used as a playful though effective way to convey the dramatic changes that database technology and research are currently undergoing
Inertial confinement fusion with advanced ignition schemes: Fast ignition and shock ignition
No full textEssential ingredients of inertial confinement fusion (ICF) are fuel compression to very high density and hot spot ignition. In the conventional approach to ICF both fuel compression and hot spot formation are produced by the implosion of a suitable target driven by a time-tailored pulse of laser light or X-rays. This scheme requires an implosion velocity of 350-400 km/s. In advanced ignition schemes, instead, the stages of compression and hot spot heating are separated. First, implosion at somewhat smaller velocity produces a compressed fuel assembly. The hot spot is then generated by a separate mechanism in the pre-compressed fuel. The reduced implosion velocity relaxes issues concerning hydrodynamic instabilities, laser-plasma instabilities and preheat control. In addition, it can lead to higher target energy gain (ratio of fusion energy to driver energy). Fast ignition and shock ignition are promising advanced ignition schemes. In fast ignition the hot spot is created by either relativistic electrons or multi-MeV protons or light-ions, produced by a tightly focused ultra-intense laser beam. In shock ignition, intense laser pulses drive a converging shock wave that helps creating a hot spot at the centre of the fuel. These advanced schemes are illustrated in the present chapter. Motivation, potential advantages and issues are described. Research needs and perspective are also briefly discussed
Burning plasma surprise
No full textIn a burning plasma, fusion-born α particles
are the dominant source of heating. In such
conditions, the deuterium and tritium
ion energy distribution deviates from the
expected thermal Maxwellian distribution
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