Local temperature measurements in supercritical counterflow in liquid helium II

In order to investigate the validity of appending the Gorter-Mellink friction term to the equations of motion of liquid helium, the temperature was measured along the axis of a channel carrying a supercritical heat current. A single thermomenter on a traversing assembly was used permitting local measurements both in the interior of the channel and in the jet formed in the free fluid. The temperature gradient in the interior of the channel is found to be in agreement with the Gorter-Mellink law up to the lambda point, but goes to zero within a channel radius, in the free jet. The Gorter-Mellink A (T ) was also measured up to the lambda point. A much stronger divergence is found as T λ is approached than was indicated by previous measurements.