Direct Access 3He Cryostat

Details of the design and construction of a 3He cryostat in which the experimental chamber can be reached directly from the outside are described. Main features of the system are (i) the use of a copper-to-copper conical joint to lock thermally at 1.2 K the structural and electrical parts that will reach the low temperature experimental chamber, and (ii) the use of epoxied joints that can be easily opened to allow for the use of different geometries. This avoids the magnetic flux trapping associated with the presence of superconductive solder in the low temperature region. The refrigerator is capable of operating down to 0.32 K for at least 10 h as a one shot system and to 0.41 K with continuous circulation of the 3He.