Several important components of a cryostat are described in this chapter. The method of vacuum sealing in low temperature, the design of piping system of a cryostat, the technical points on windows for optical measurement or X-ray diffraction experiments, and the thermal problems on the signal lead wires and the current leads for superconducting magnets are discussed from the view point of their thermal processes of heat generation and cutting heat inputs. The two main sample-cooling-processes (gas cooling and contact cooling) in cryostat are also discussed. Effective use of evaporated helium gas is the most important method for the reduction heat input to low temperature region. It is also necessary to optimize cryostat design taking into account of total thermal balance in a cryostat with all components.
