  Detectors for direct dark matter search using noble gases in liquid phase as
detection medium need to be coupled to liquefaction, purification and
recirculation systems. A dedicated cryogenic system has been assembled and
operated at the INFN-Naples cryogenic laboratory with the aim to liquefy and
purify the argon used as active target in liquid argon detectors to study the
scintillation and ionization signals detected by large SiPMs arrays. The
cryogenic system is mainly composed of a double wall cryostat hosting the
detector, a purification stage to reduce the impurities below one part per
billion level, a condenser to liquefy the argon, a recirculation gas panel
connected to the cryostat equipped with a custom gas pump. The main features of
the cryogenic system are reported as well as the performances, long term
operations and stability in terms of the most relevant thermodynamic
parameters.
