The next step after ITER is to demonstrate the viability and generation of electricity by a future fusion reactor (DEMO). The specifications required to operate an NBI system on DEMO are very demanding. The system has to provide a very high level of power and energy, (~100MW of D0 beam at 1 MeV), including high wall-plug efficiency (η>65 %). For this purpose, a new injector concept, called Siphore, is under investigation between CEA and French universities. Siphore is based on the stripping of the high energetic negative ions by photo-detachment provided by several Fabry-Perot cavities (1-2 MW of light power per cavity) implemented along the D beam. The beamline is designed to be tall and narrow in order that the photon flux overlaps the entire negative ion beam. The paper will describe the present R&D at CEA which addresses the development of an ion source and pre-accelerator prototypes for Siphore, the main goal being to produce an intense negative ion beam sheet. Cybele is based on a magnetized plasma column where hot electrons are emitted in the source center. Parametric studies of the source are performed using Langmuir probes in order to characterize the plasma under different aspects and to compare with numerical models under developments in French universities.