Probing phonons in plutonium
Plutonium (Pu) is well known to have complex and unique physico-chemical properties [1]. Notably, the pure metal exhibits six solid-state phase transformations with large volume expansions and contractions along the way to the liquid state: {alpha} {yields} {beta} {yields} {gamma} {yields} {delta} {yields} {delta}' {yields} {var_epsilon} {yields} liquid. Unalloyed Pu melts at a relatively low temperature {approx}640 C to yield a higher density liquid than that of the solid from which it melts. Detailed understanding of the properties of plutonium and plutonium-based alloys is critical for the safe handling, utilization, and long-term storage of these important, but highly toxic materials. However, both technical and safety issues have made experimental observations extremely difficult. Phonon dispersion curves (PDCs) are key experimental data to the understanding of the basic properties of Pu materials such as: force constants, sound velocities, elastic constants, thermodynamics, phase stability, electron-phonon coupling, structural relaxation, etc. However, phonon dispersion curves (PDCs) in plutonium (Pu) and its alloys have defied measurement for the past few decades since the discovery of this element in 1941. This is due to a combination of the high thermal-neutron absorption cross section of plutonium and the inability to grow the large single crystals (with dimensions of a few millimeters) necessary for inelastic neutron scattering. Theoretical simulations of the Pu PDC continue to be hampered by the lack of suitable inter-atomic potentials. Thus, until recently the PDCs for Pu and its alloys have remained unknown experimentally and theoretically. The experimental limitations have recently been overcome by using a tightly focused undulator x-ray micro-beam scattered from single-grain domains in polycrystalline specimens. This experimental approach has been applied successfully to map the complete PDCs of an fcc {delta}-Pu-Ga alloy using the high resolution inelastic x-ray scattering (HRIXS) capability on ID28 [2].
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15013614
- Report Number(s):
- UCRL-PROC-201576; TRN: US0600194
- Resource Relation:
- Conference: Presented at: Symposium on Actinides: Science and Technology, Boston, MA, United States, Dec 01 - Dec 03, 2003
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
43 PARTICLE ACCELERATORS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACTINIDES
ALLOYS
CROSS SECTIONS
ELECTRON-PHONON COUPLING
MONOCRYSTALS
NEUTRONS
PHASE STABILITY
PHASE TRANSFORMATIONS
PHONONS
PLUTONIUM
SAFETY
SCATTERING
STORAGE
THERMODYNAMICS
TOXIC MATERIALS
WIGGLER MAGNETS