The CEA’s Military Applications Division (DAM) is responsible for the design, manufacture, through-life support and  dismantling  of the  nuclear  warheads  that equip  France’s  sea-  and  airborne deterrence forces.  Since  1996,  France  has  relied  on  the  Simulation  Program  to  guarantee  the  operational performance and safety of its nuclear weapons throughout their lifetime. The program is based on a usual  scientific  approach  that  implies  hundreds  of  scientists  and  major  facilities  for  solving  and validating the equations used to model the functioning of thermonuclear weapons: supercomputers (EXA1, DIF), X-ray machines (EPURE, Valduc) and the MegaJoule Laser (LMJ, CESTA).
 
The talk will open with an historical review of the development of the French nuclear deterrence that highlights the pioneering work of CEA’s teams of scientists. Since the definitive ending of nuclear tests, the  DAM  constantly  streamlined  its  organizational  structure:  five  main  programs  are  currently managed  in  five  military  centers:  nuclear  warheads,  nuclear  reactors  for  submarines  and  aircraft carriers, strategic materials, prevention of proliferation, conventional defence.
 
To  meet  the  challenge  of  guaranteeing  the  reliability  of  nuclear  warheads  under  the  Simulation Program, the Laser MegaJoule is a crucial tool for the experimental validation of the physical dynamics involved in the nuclear phase of weapon functioning. Once fully commissioned, 176 laser beams will deliver  a  maximum  power  of  400  TW  of  UV  light  on  the  target.  Among  all  experiments,  Inertial Confinement  Fusion  (ICF)  sets  the  most  stringent  specifications  on  LMJ’s  features,  as  the  aim  is  to initiate nuclear fusion reactions by compressing and heating targets filled with a Deuterium-Tritium fuel. To measure the different phenomena, the LMJ presently offers several diagnostics operating in multiple X-visible-UV wavelengths ranges as well as particles diagnostics. The last part of the talk will be dedicated to one of these plasma diagnostics: the near-backscatter imaging (NBI) system. The NBI measures the stimulated Brillouin and Raman scattered light around two laser quads of the upper LMJ hemisphere and contributes to the estimation of energy balance.
 
 Coffee and pastries will be served at 11:00 in the hall.