MODELING AND SIMULATION OF AN ULTRA-STABLE CRYOSTAT FOR NAHUAL

NAHUAL is a cryogenic high resolution near infrared echelle spectrograph for the GTC (Gran Telescopio de Canarias). The main goal of the instrument is to deliver high-precision radial velocities for cool stars at IR wavelengths. NAHUAL is conceived as a highly specialized instrument, capable of finding habitable planets around red dwarfs (Martin 2008). IR instruments must operate under ultra-cold temperatures in temperature-controlled vacuum containers called dewars or cryostats to reduce disruption by heat noise. The use of LN2 instead of mechanical coolers to cool the instrument is mandatory to avoid noise vibrations. NAHUAL concept is adapted from GIANO@TNG, with a requirement of thermal stability in the optical bench a factor 10 above GIANO's one: similar to 0.1 K. The modeling and simulations carried on at NAHUAL's conceptual design are presented in this paper.