| 摘要 |
<p>An insert for a horizontal cryostat penetration includes a plurality of foam particles or spheres between which are disposed disks of high thermal conductivity. The spheres or particles are disposed in an annular volume defined by two concentric, thin-wall, low thermal conductivity conduits. This foam filled insert provides thermal insulation and significantly reduces the formation of coolant vapor convection currents in the penetration which would otherwise significantly increase the rate of coolant evaporation from the cryostat. The insert is constructed so that the foam particles are ejected from the penetration upon the buildup of excessive internal pressure. The insert has also preferably one or more string-like lengths of sealing material disposed in a helical pattern about the outer one of the concentric conduits. Accordingly, when this insert is placed within a third conduit, a helical coolant vapor path is formed for insert cooling and exterior ventilation.</p> |
