Abstract
We reported in a previons paper that, in a wide aperture liquid helium dewar, the largest facter among heat losses is the radiant heat input from the top surface and that it can be reduced by painting aquadag on the inner wall.
In this paper, we investigate several kinds of surfaces instead of aquadag as durable treatment, for example, sulfarized, oxidized or sandblasted surface. In the case of sandblasted surface, its rough surface was approximated by sine-wave and a computer simulation was applied to the thermal analysis.
