CARMENES-PLUS: a technical upgrade for CARMENES and the impact on its science

CARMENES is a dual (VIS: 550 to 950 nm; NIR: 950 to 1700 nm) high-resolution spectrograph installed at the 3.5 m telescope at the Calar Alto Observatory (CAHA, Almería, Spain). The NIR channel spectrograph uses the radial-velocity method for detecting exoplanets around low-mass stars. Thus, a high thermal stability is required in the NIR cooling system to achieve a high precision in radial velocities. The cooling system was originally conceived to operate with a discontinuous cryogenic coolant (nitrogen) flow, but within the framework of the project CARMENES-PLUS, I want to show you a challenging and comprehensive upgrade to accomplish a more ambitious thermal stability. The solution proposed is based on a continuous flow and an uninterrupted flow feeding system . The aim is to bring the NIR channel to an outstanding scientific performance, with improved intrinsic radial velocity precision with respect to the preceding performance, both in the short and the long term.