Safety interlock and vent system to alleviate potentially dangerous ice blockage of top-loading cryostat sample sticks

A combined solution is presented for minimizing the safety hazards associated with closed cycle cryostats described by Swainson & Cranswick [J. Appl. Cryst.(2010),43, 206–210]. The initial solution is to install a vent tube with one open end deep inside the sample space and a pressure relief valve at the top. This solution works for either a cryogen or a cryogen-free (closed cycle) system. The second approach, which can be combined with the first and is applicable to cryogen-free cryostats, involves electrically interlocking the closed cycle refrigerator compressor to the sample space, so that the system cannot be cooled in the presence of a leak path to air.

Mechanical design of a dual-cryostat instrument for a high-field pulsed magnet

The engineering of a dual-cryostat for a pulsed-magnet instrument at the Advanced Photon Source is presented. The dual-cryostat independently cools the magnet coil (using liquid-nitrogen) and the sample (using a closed-cycle refrigerator). Liquid-nitrogen cooling may allow a repetition rate of a few minutes for peak fields near 30 T. The system is unique in that the liquid-nitrogen cryostat incorporates a double-funnel vacuum tube passing through the solenoid's bore in order to preserve the entire angular range allowed by the magnet bore for scattering studies. Second, the use of a separate refrigerator for the sample allows precise positioning of samples in the bore while minimizing magnet vibrations propagating to the sample during pulsed-field generation.