Preparation and Realization of European Shock Ignition Experiments


Introduction and goals of the project

The project, funded by Eurofusion (European Consortium for the Development of Fusion Energy), aims at realizing a European research program on Shock Ignition (SI), a promising approach to Inertial Confinement Fusion proposed by R. Betti. SI is based on the separation of the compression phase of the thermonuclear target from the ignition phase, which is realized by a high-intensity laser beam (up to 1016 W/cm2 in a spike of several hundreds picoseconds). The feasibility of SI relies on the capacity of such spike to produce a very strong converging shock (at least 300 Mbar at the ablation front). Being substantially compatible with present-day laser technology (used to build NIF and and LMJ), SI could be tested within the next decade.

Time-resolved SRS spectrum from 3w irradiation and SRS spectrum from 1w irradiation, recently acquired at PALS facility

The beginning of operation of the LMJ/PETAL laser facility and its academic opening to Civilian Research done by European Academic groups opens, for the first time, the possibility of performing “inertial fusion experiments” at full-scale in Europe.
In order to prepare such future experiments, the participants to this project will perform experiments in Europe at Prague Asterix Laser System (PALS) and at the laser facility Omega at the University of Rochester, with the goal of both answering some open physical questions related to SI and consolidating a European research community directly working on inertial fusion experiments with big lasers. Other planned experiments, coordinated by the ILIL laboratory, will be carried on at  Vulcan / CLF laser and at GEKKO XII laser in Osaka.
The main physical questions, which we want to address, aim 1) at investigating the generation of hot electrons in the intensity regime relevant for SI and their effects on shock generation and dynamics, and at evaluating to what extent hot electrons are an essential ingredient for reaching shock pressures ≥ 300 MBar, and 2) at evaluating the need for uniformity in the laser spike, and the eventually assessing the possibility of realizing a “bipolar irradiation” of the target (which would be immediately compatible with machines built to realize indirect drive, like NIF and LMJ).
Apart answering these physical questions, the final output of the project will also be the preparation of a proposal for a joint experiment on the bipolar irradiation scheme to be performed on LMJ/PETAL.

The role of ILIL research group

The group, previously involved in the European HiPER project, has proven skills in the experimental study of laser solid interactions and, in particular, has significant expertise in characterizing laser plasma interaction mechanisms. In this project, the ILIL group contributes to experimental campaigns, often coordinating the experiments with Principal Investigators. Its work includes both the characterization of hot electron  (including GEANT Montecarlo simulations) and, overall, the investigation of parametric instabilities. In SI interaction regime, in fact, the role of Stimulated Brillouin Scattering (SBS), Stimulated Raman Scattering (SRS) and Two Plasmon Decay (TPD) is central both for the significantly degraded laser-plasma coupling due to a strong reflection of light (SBS and SRS), and for the generation of hot electrons (SRS and TPD), which may preheat the fuel or affect the shock pressure.

The team

The project leader is D.Batani (Centre Laser Intense and Apllications, CELIA). The team is composed by several research groups widespread across Europe, including both theoretical and experimental expertise, which have already contributed to research on Shock Ignition. Many of such groups were already in the European HiPER project, dedicated to demonstrating laser driven fusion as a future energy source. The research groups involved are:

  • Our ILIL laboratory from Pisa. The responsible of the research unit is G.Cristoforetti.
  • Prague team (IoP, ELI, , PALS, CTU Prague) – Group Leader: Stefan Weber
  • University of Rome “La Sapienza” – Group Leader: Stefano Atzeni
  • UK shock ignition collaboration – Group Leader: Robbie Scott
  • Universidad de Las Palmas de Gran Canaria (ULPGC) – Group Leader: Ricardo Florido
  • IPPLM, Warsaw – Group Leader: Tadeusz Pisarczyk
  • Wigner Research Centre for Physics of the Hungarian Academy of Sciences – Group Leader: István Földes
  • Polytechnic University of Madrid, Spain – Group Leader: Javier Honrubia