Citation | Distinguished for his contributions to low temperature physics, and particularly to the study of quantum fluids. His pioneering work on superfluid 4He included both the first observation of mutual friction in the uniformly rotating liquid, which provided the first experimental evidence for the quantified vortex line, and the discovery and explanation of effects due to the excitation of vortex waves. He built the first successful 3He-4He dilution refrigerator, using a cycle that he himself invented and which has been used in most subsequent designs; this refrigerator has been of the greatest importance in the recent development of low temperature physics. He has carried out valuable work on the Mossbauer effect, including some pioneering applications in the study of lattice dynamics and diffusion. Most recently he has been responsible for valuable and influential work on superfluid 3-He, both experimental and theoretical, with particular emphasis on orbital dynamics in 3He-A. His work is highly original, and in it he combines a deep understanding of the basis physics with an ability to devise and execute experiments of crucial importance. |