Scientific Proposal for Enabling Research Project (Max 10 Pages, Excluding Title Page)
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CfP‐ADMIN‐AWP19‐ENR‐01 Scientific proposal for Enabling Research project (max 10 pages, excluding title page) Title Routes to High Gain for Inertial Fusion Energy Principal Investigator Peter A Norreys, Professor of Inertial Fusion Science, University of Oxford Beneficiary CCFE (United Kingdom) Project 24 months duration Abstract The award of the two EUROfusion Enabling Research grants “Towards Inertial Fusion Energy (ToIFE)” from 2014‐2018 enabled our consortium to make significant progress in achieving a fundamental understanding of the physics needed to demonstrate the viability of laser‐driven fusion as an alternative, complementary road towards sustainable, clean and secure energy source. We plan to build on these achievements by further integrating our activities by undertaking a series of collaborative experiments on existing European facilities to qualify new diagnostics, instruments and techniques, in preparation for deployment on the new PETAL/LMJ facility in Bordeaux early in the next decade. We also plan to support these investigations by state of the art theoretical and computational modelling. Our proposal has three main objectives: a) Studying fundamental materials properties and laser‐plasma interactions to acquire new insights into basic physics for ignition on MJ‐scale facilities, including the development of new X‐ray, particle and optical diagnostics on the Vulcan laser facility, in preparation for commissioning on the PETAL/LMJ facility at CEA; b) critically evaluating advanced alternative schemes for the high gain target designs that are required for inertial fusion energy, including the exciting new auxiliary heating approach that was developed under the ToIFE project; c) developing key IFE innovative materials, lasers and target fabrication technologies. The two previously awarded ToIFE grants improved the co‐ordination between the European partners, as indicated by the growing number of collaborative studies, and enabled us to identify more clearly the commonalities between Inertial and Magnetic Confinement Fusion activities, thus providing a route to reinforce links between the two communities. 1 | Scientific Proposal CfP‐ADMIN‐AWP19‐ENR‐01 Introduction. This new “Routes to High Gain for Inertial Fusion Energy” proposal here builds upon the insights and strong collaborations established under the 2014‐2018 “Towards Inertial Fusion Energy (ToIFE)” project1, albeit it with a rotation of the project co‐ordinator from France (S. Jacquemot) to the United Kingdom (P.A. Norreys). From the commencement of the ToIFE project in 2014, thanks to EUROfusion financial support, substantial quantities of high quality experimental data related to inertial confinement fusion experiments at the National Ignition Facility and the Laboratory for Laser Energetics have been made available to the consortium, either through the published literature or through active collaborative contacts with American colleagues. From this data, along with the pioneering work undertaken within the ToIFE grants, we have significantly advanced our scientific understanding of the physics of thermonuclear ignition and have identified a number of critical issues that must be addressed in order to achieve a burning hot‐spot, including the implosion energetics, the pusher adiabat, tamping effects, and extending the inertial confinement time. The new approaches, described here in this proposal, have a new focus on the Vulcan laser facility and the PETAL/LMJ facility in Bordeaux that will enable European leadership for some of these topical questions into the next decade. Objectives and expected outcomes. We propose here to build upon our recent successes to reinforce three main axes: a) Studying fundamental materials properties and laser‐plasma interactions to acquire new insights into basic physics for ignition on MJ‐scale facilities, including the development of new X‐ray, particle and optical diagnostics on the Vulcan laser facility, in preparation for commissioning on the PETAL/LMJ facility at CEA; b) critically evaluating advanced alternative schemes for the high gain target designs that are required for inertial fusion energy, including the exciting new auxiliary heating approach that was developed under the ToIFE project; c) developing key IFE innovative materials, lasers and target fabrication technologies The two previously awarded ToIFE grants improved the co‐ordination between the European partners, as indicated by the growing number of collaborative studies1, and enabled us to identify more clearly the commonalities between Inertial and Magnetic Confinement Fusion activities, thus providing a route to reinforce links between the two communities. Description and methodology. Axis A. Studying fundamental material properties and laser‐plasma interaction mechanisms The implosion energetics still need to be optimised, of course, in order to achieve a burning hot spot and, beyond that, ignition. In particular, it is necessary to increase the implosion kinetic energy that is available so that there is more thermal energy in the hot spot at stagnation, which is a key limitation at this point in time. This can be done by either enhancing the drive coupling energy or by optimization of the capsule design, e.g. by deploying different ablator materials, studying the variations in mass, along with their dependence on the target thickness. Similarly, the reduction in the pusher adiabat – i.e. the degree of departure of the pressure of the compressed fuel from the ideal Fermi degenerate pressure ‐ can be achieved by controlling both the fast electron and the hard X‐ray preheat, primarily arising from laser‐ plasma instabilities, as well as Rayleigh‐Taylor induced mixing, the latter by reducing the coasting time of the implosion. The increase of the effective disassembly time can be achieved by improvements to the implosion symmetry. Certainly, the recent successes on the National Ignition Facility, such as the 1 The “Towards Inertial Fusion Energy (ToIFE)” project, which started in 2014 with the award of the two EUROfusion Enabling Research grants, was aimed at achieving a fundamental understanding of the physics needed to demonstrate the viability of laser‐driven fusion as an alternative road towards sustainable, clean and secure energy sources. The projects have allowed significant progress to be made in the field of laser‐ plasma interaction physics and inertial fusion energy science, as shown on the pages of the ToIFE website (http://web.luli.polytechnique.fr/IFE‐KiT/ToIFE.htm), which details the major results from the start of the project in 2014 until the latest reporting stage, at the end of 2017. 2 | Scientific Proposal CfP‐ADMIN‐AWP19‐ENR‐01 demonstration of a fusion output energy that is more than twice the total kinetic energy of the imploding fuel with unprecedented yields and stagnation pressures, show that increased capsule performance can indeed be achieved through the mitigation of mix in both the hotspot and the compressed DT fuel [S. Le Pape et al., Phys. Rev. Lett. 120, 245003 (2018)]. A.1 Atomic physics In most capsule designs deployed until now on the National Ignition Facility, mid‐Z elements have been used as dopants (Ge or Si / Cu) to the ablator material (plastic / high density carbon / beryllium) to increase the preheat shielding and to image the shell in‐flight. In the ToIFE grants, we concentrated on the atomic physics associated with this problem, to great success. A series of indirectly‐ driven near‐LTE opacity experiments were performed on the LULI2000 laser facility. Thanks to an inventive twin‐hohlraum target concept and a dual‐channel spectrometer developed at LIDyL, XUV and x‐ray photo‐ absorption spectra of mid‐Z elements (copper and nickel) have been, for the first time, simultaneously recorded [M. Dozières et al., HEDP 17, 231 (2015); F. Thais IFSA2017]. A final campaign on the ELFIE laser facility of the three‐year X‐ray and XUV emission spectroscopy program is being conducted in 2018 on germanium and its analysis, together with the one of the 2nd experiment, postponed to the end of 2017 due to a laser breakdown, will be carried out in order to complement the LULI2000 data and further benchmark the codes. The LiDyL High Energy Density Matter group in Saclay recently had some insight into the relative contributions of electric‐dipole and magnetic‐dipole transitions in highly ionized plasmas. The approach involves the Flexible Atomic Code, using either a detailed or "statistical" approach dealing the transitions within the Unresolved Transition Array formalism. The Wigner Research Centre for Physics has experience in plasma diagnostics, either in light scattering or in x‐ray spectroscopy. Tasks 2019‐2020 – (CEA/LULI, CEA/LIDyL and Wigner Institute). We intend to complete the data analysis of the emission experiments conducted on the ELFIE laser facility in 2019 [ATOM1]. We will also analyze the contribution of various transition types to the radiative processes in low‐electronic‐ density tungsten plasmas present in the divertor of tokamaks. Such plasmas being out of thermodynamic equilibrium, this objective requires to solve large systems of kinetic equations. Among other results, this will help in determining the radiative losses in the tokamak divertor, which may have a strong influence on its operation [ATOM2]. At present a new spectrometer (based on conically bent von Hamos arrangement) is being designed now at the Wigner Institute which allows simultaneous observation of K‐shell lines from different microdots.