Investigation of effects associated with thermal counterflow in rotating superfluid helium

The mutual friction force between the normal and superfluid components of He II has been studied by measuring the temperature and chemical potential gradients which arise when thermal counterflow is imposed tranverse to an array of quantized vortex lines. A very sensitive temperature gradiometer system has been developed in order to measure the extremely small temperature gradient which is produced. The magnitude of the mutual friction force as determined by the temperature gradient measurements was found to be in reasonable agreement with the results of others using a widely different technique. A devise capable of direct chemical potential difference measurements is described. Using this device, the chemical potential gradient associated with vortex line motion has been observed. In addition, effects which are attributable to vortex line pinning have been seen. Some of the more interesting results obtained under turbulent flow conditions are also described