CILAS - CEA Programs - Megajoule Laser

THE MEGAJOULE LASER

The CILAS CEA [French Atomic Energy Commission] Programmes Department is proud to be participating in an exceptional project: the MegaJoule laser. The MegaJoule laser consists of 240 laser beams comprising 30 chains and 8 beams, each of which will be installed inside a structure with a total volume of 40,000 m², as long as the Eiffel Tower and as high as the Arc de Triomphe.

Introduction

The 240 laser beams will converge and concentrate their energy on a microbead just a few millimetres in diameter containing deuterium and tritium. By concentrating energy of approximately two megajoules on this microbead for a time window of just a few billionths of a second, the pressure and temperature conditions of the microbead (several millions of degrees) will make it possible to re-create the conditions under which thermonuclear fusion takes place.

This laser, the most powerful in the world, is currently being installed in the southwest of France on the CEA CESTA site between Bordeaux and Arcachon. The sheer physical dimensions of this exceptional laser and the capacity of its instruments will be used, to simulate the conditions of a thermonuclear explosion under laboratory conditions.

Following the signature of the treaty formalising a complete ban on nuclear testing, the French government has entrusted the CEA with the development of a simulation programme to guarantee the reliability and security of the French nuclear dissuasion arsenal.

The MegaJoule laser (LMJ) is one of the tools involved in this simulation programme. The laser will be able to create, within a miniscule area, heat and pressure conditions comparable to those at the core of the sun, and will provide us with information to further our understanding of thermo-nuclear reaction phenomena.
Open to civil research, the laser also opens new fields of investigation in a host of sectors such as plasma physics, atomic physics, laser radiation/materials interactions, and the thermodynamics of irreversible processes.

Involvement of CILAS

CILAS’ participation in this project consists of supplying CEA-DAM with two essential MegaJoule components: laser amplifiers and deformable mirrors.

Laser amplifiers

CILAS will be providing a total of 60 laser amplifiers, each weighing 19 tonnes. The purpose of the amplifier is to amplify a small laser impulse using 180 flash lamps (2 m in length and 5 cm in diameter) which illuminates 72 glass plates laced with neodymium. The amplifiers are currently in the industrialisation phase, and line production is scheduled to run from 2008 to 2014.

Deformable mirrors

As the laser beam is being amplified, it bounces off deformable mirrors (400 mm x 400 mm) located at the bottom of the laser cavity. During this beam reflection, the mirror surface, deformed using 48 actuators located behind the mirror, will correct any laser beam imperfections. 240 mirrors of this type will be used.

Cleanliness engineering

CILAS has over 20 years experience in engineering projects in cleanliness (including work on Phébus, the forerunner of the MegaJoule). In this project, CILAS is participating in the installation of equipment in both the cleanroom and laser hall, working in collaboration with CEA-DAM teams.
This bears well for a long and fruitful participation in the exciting work of installing and operating the MegaJoule laser for the next 30 years.

Installing the splitting blade

Laser plate cartridge