| Popis: |
The Critical Dynamics in Microgravity Project (DYNAMX), which is in competition for flight aboard the International Space Station in the year 2004, will study heat transport through a column of liquid 4He as the liquid helium transitions from its superfluid to its normal-fluid state. Stray heat will be controlled to within 10 pW, and temperatures will be measured with a resolution of better than 300 pK, over the course of the measurements on orbit. The most closely controlled heat conduction measurements in physics have been performed on Earth to support these planned flight measurements (Day, 1998; Moeur, 1997). The alignment of the gravitational acceleration g with the heat flux Q in the Earth-based laboratory is essential in order to make the experiment a pseudo one-dimensional system that is tractable to analysis (Duncan, 1998). This alignment must be achieved to within two mrad in an absolute sense, and it should be held constant to the best degree possible throughout the duration of the measurements... |
