| EPSRC Reference: |
GR/N20225/01 |
| Title: |
SUPRATHERMAL PHONON SPECTRUM |
| Principal Investigator: |
Wyatt, Professor A |
| Other Investigators: |
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| Department: |
Physics |
| Organisation: |
University of Exeter |
| Scheme: |
Standard Research (Pre-FEC) |
| Starts: |
29 October 2000 |
Ends: |
28 April 2004 |
Value (£): |
286,516
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| No relevance to Underpinning Sectors |
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Summary on Grant Application Form |
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This year, 1999, it has become apparent that large parts of the established picture of phonon dynamics in liquid helium are fundamentally wrong. Much of the knowledge of phonons has been acquired through measurements of phonon pulses and some of these have been plausibly misinterpreted for many years. We wish to correct this situation. Our recent work shows that the dynamics of phonons in anisotropic distributions are qualitatively different to those in isotropic distributions and as pulses are always anisotropic their behaviour must be interpreted correctly. We have developed a theory which successfully describes the behaviour of short phonon pulses and explains how a low temperature (1K) group of phonons can convert more than half its energy to high energy (10K) phonons. In long pulses the low and high energy phonons occupy the same space and from the theory we make the remarkable prediction that the density of high energy phonons becomes supra-thermal, i.e. the number density of high energy phonons is orders of magnitude greater than the equilibrium density at the temperature of the low energy phonons. This proposal is to experimentally verify this theoretical prediction and so establish the correct picture of phonon dynamics in liquid helium.
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Key Findings |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Potential use in non-academic contexts |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Impacts |
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| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
| Summary |
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| Date Materialised |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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| Project URL: |
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| Further Information: |
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| Organisation Website: |
http://www.ex.ac.uk |