ESPRESSO VCS: Vacuum and cryogenic Controller System (VCS) for a Spectrograph

In this paper the authors present a concept, design, implementation and results of a vacuum and cryogenic system for the ESPRESSO VLT instrument. The system is comprised of two major control functionalities: vacuum and cryogenics. The Vacuum system is a shared manifold for five chambers, and includes a pre-pump and a turbo molecular pump as vacuum sources. The Cryogenic System is based on a continuous circulation of Liquid Nitrogen (LN2). One shared LN2 line is used for supply and control of the cool down of two detector cryostats and two sorption pumps (also called cryopumps). The Cryopumps are a passive vacuum pumps to compensate for the outgassing of the big vacuum chamber (volume approx. 10 m(3)), minimizing vibrations during operation. The control of the Vacuum System is PLC-based, whereas the Cryogenic is PPC (Program and Process Control) and Lakeshore 336 based. There is special emphasis on the temperature stability of the detector cryostat (goal < 10 mK RMS). Result data for the operation shown are from ESPRESSO commissioning in late 2017.