Detail Project and Funding

Abstract: The most recent results from the National Ignition Facility (NIF) show significant increase in neutron yield and progress towards alpha-particle dominated heating and ignition. NIF uses indirect drive, in which the laser energy is converted to a highly uniform near-thermal soft X-ray source. This benefits from drive uniformity, yet for future inertial fusion energy (IFE) we need more efficient and higher gain schemes. The emphasis of this project is to complement the NIF approach by addressing the physics of higher-gain directdrive (DD) techniques. Our preferred DD scheme is Shock Ignition (SI). This scheme separately compresses the target and then launches a strong shock (>300 Mbar) igniting the thermonuclear fuel. This shock is driven by a high-intensity laser spike of several-hundred picosecond towards the end of compression. The SI approach is compatible with existing laser technology (used in NIF and LMJ) and, with some modifications, target areas. In this respect, SI is one of the few IFE schemes that can be tested at ignition-scale within the next decade. Indeed, with the opening of the French LMJ/PETAL facility to academic civilian research, European groups will, for the first time, have the opportunity to perform inertial fusion experiments at ignition-scale in Europe.
The present project builds on physics and community building successes of our previous Enabling Research project CfP-AWP17-IFE-CEA-01 “Preparation and Realization of European Shock Ignition Experiments”. We will continue this work bringing in new research teams to explore novel ideas that emerged over the last two years. Our project benefits enormously from a fruitful collaboration with Rochester University. During the project, we plan to perform experiments in Europe (accessing PALS, Vulcan, Phelix and LMJ/PETAL) and overseas. Non-European experiments include using the Omega direct-drive facility at Rochester and facilities in Asia (Gekko in Japan, Shen Guang II and III in China). Our goals are to consolidate a European community working on DD experiments with big lasers and to answer physics questions related to DD and SI. A particular focus will be the experimental, computational and theoretical study of hydrodynamic and laserplasma instabilities associated to DD and SI, including novel diagnostics developments. More specifically, the key questions are to: 1) investigate the generation of hot electrons at SI laser intensities and their effects on shock generation, 2) evaluate to what extent hot electrons are needed for reaching shock pressures above 300 MBar, 3) evaluate the impact of parametric instabilities and crossbeam energy transfer in DD and SI in particular, 4) evaluate the impact of hydrodynamic instabilities and how uniformity can be maintained in the compression and SI phases, 5) assess the feasibility of using existing facilities (NIF and LMJ) for SI, in particular by using a “bipolar irradiation” of the target.

INO’s Experiments/Theoretical Study correlated:
Laser-plasma interaction in a regime relevant for laser-fusion via shock-ignition

The Scientific Results:
1) Laser-Plasma Instabilities with chirped pulses at the Vulcan TAW facility
2) Half-integer harmonics: a powerful tool for investigating Stimulated
Raman Scattering and Two Plasmon Decay in Shock Ignition irradiation

regime
3) Laser-Plasma Instabilities in the Shock Ignition regime at the

Vulcan TAW facility
4) Investigation of Laser Pulse Interaction in Shock Ignition regime at Vulcan TAW facility
5) Preliminary results from the LMJ-PETAL experiment on hot electrons characterization in the context of shock ignition
6) Hot electron retention in laser plasma created under terawatt subnanosecond irradiation of Cu targets
7) Bremsstrahlung cannon design for shock ignition relevant regime