| 摘要 |
A thermal barrier is disclosed, comprising by a porous material impregnated with a fluid. The fluid is preferably helium, the porous material may be an epoxy resin impregnated cloth. An anisotropic thermal barrier between two regions 2 and 3 is also disclosed, wherein the thermal conductivity in a direction parallel to the interface between the barrier and one of the regions is greater than the thermal conductivity in a direction substantially normal to the barrier. This may be achieved with layers of two materials 4 and 5, preferably a metal and a polymer. A further thermal barrier is disclosed, comprising a solid state composite that undergoes a magnetic phase change at temperatures below 10K, the composite is preferably gadolinium oxysulphide. These thermal barriers are preferably used in a MRI scanner. Conduits for carrying cooling fluid through the barrier may also be supplied. |
