In this Letter of Intent, we describe the experimental program that we want to perform with the FAZIA demonstrator coupled to the INDRA detector at GANIL. This scientific program concerns the exploration of the N/Z (isopin ratio) dependence of the dynamics in dissipative collisions, from evaporation towards vaporization processes. The experimental program requires a charged particle detector array that covers as much as possible of the whole 4p solid angle with high efficiency and also requires the determination of the atomic number Z as well as the atomic mass A for the reaction products. The idea is to initiate a new Physics program focused on the N/Z degree of freedom during the commissioning phase of the FAZIA demonstrator, using incident beams available at GANIL in the Fermi energy domain. Indeed, the good performances obtained with the FAZIA prototypes  during the R&D phase, already allowed us to investigate some aspects of isospin physics, in particular the isospin transport and odd-even staggering [2,3].
In this letter, we will first describe the FAZIA demonstrator specifications and its mechanical coupling with INDRA . Then, the second part will present four physics cases :
a- Isospin and density dependence of the nuclear Equation of State ;
b- Measurement of vaporization event properties to constrain symmetry energy at low density ;
d- Density dependence of the symmetry energy ;
c- Reconstruction of decay chain of excited Quasi-Projectile.