A means and a method to cool down an MRI magnet, in a cryostat that is designed for a maximum pressure of about 0.2 MPa, are described which use cold helium output from a Brayton cycle refrigerator at a pressure of about 0.8 MPa to exchange heat with helium in the MRI cryostat in a coupling heat exchanger that is located removeably in or proximate the neck tube of the MRI cryostat. A circulator drives helium from the MRI cryostat through the coupling heat exchanger.
