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Past and Future Insights from Neutron Scattering

Past and Future Insights from Neutron Scattering. Collin Broholm * Johns Hopkins University and NIST Center for Neutron Research. Virtues and Limitations of Neutron Scattering New Sources and Instrumentation Capabilities of New Instrumentation Conclusions. * supported by NSF DMR-0074571.

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Past and Future Insights from Neutron Scattering

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  1. Past and Future Insights from Neutron Scattering Collin Broholm* Johns Hopkins University and NIST Center for Neutron Research • Virtues and Limitations of Neutron Scattering • New Sources and Instrumentation • Capabilities of New Instrumentation • Conclusions * supported by NSF DMR-0074571

  2. Zachary Fisk and Neutron Scattering • More than 70 papers on neutron scattering: • Heavy Fermion Systems • Kondo Insulators • Valence Fluctuating systems • High TC superconductors • Neutrons used to probe • Magnetic order and Fluctuations • Structure and sample quality • Thermal Expansion • Phonons

  3. Spin Fluctuations in U2Zn17 Broholm et al. PRL (1987)

  4. Structure of YbInCu4 a probe of sample quality Intensity (103 counts/ms) Flux-grown crystal d-spacing (A) • Contrast between elements with similar Z • Sensitivity to light atoms in heavy matrix Lawrence et al PRB (1996)

  5. Magnetic Structure of CeRhIn5 Bao et al PRB (2000)

  6. Probing Spin Density Distribution UBe13 UPt3 U 5f, 6d, and -7f spin polarization Pt polarized as well Only U polarized Neumann, Brown, et al. Physica B (1991)

  7. Electronic Interactions in La2CuO4 Coldea et al PRL (2001)

  8. What makes it hard • 150 MeV thermal energy per neutron (fission) • a factor Z2 less than X-ray scattering • Limitations of current instrumentation • dynamics in samples < 1 mm3 • dynamics in nano-structured solids • Lateral surface structure • complex materials with weak signals • Signals from impurities at low concentration • Spatial and temporal resolution • Pressure above 25 GPa

  9. Expanding Applicability of a Powerful Probe • Increase source brightness • Increase spectral brightness by cooling neutrons • Increase temporal brightness in pulsed neutron source • Improve beam delivery system • Match solid angle to wave vector resolution requirements • Match bandwidth to energy resolution requirements • Increase solid angle of detection system • Position sensitive detectors • Crystal analyzer arrays

  10. New Instrumentation and Sources • NIST cold source and instrument upgrade 2002-4 • HFIR cold source and instrument upgrade 2002 • LANSCE source and instrument upgrade 2002 • US Spallation Neutron Source 2006 • German high flux research reactor 2004 • Australian high flux research reactor 2005 • Japanese Spallation Neutron Source 2006 • European Spallation Neutron Source ? • Chinese Advanced Research reactor ?

  11. New Instruments for CMP at NIST Instrument Begin DE (meV) Condensed Matter Science Enabled FANS 1999 1-3 Phonon Density of States Spin Echo 2000 10-5 Flux lattice dynamics Dynamic Correlations in Glasses Back Scattering 1999 10-3 Critical Phenomena Quantum Tunelling Disc Chopper 2001 10-2-1 Quantum Critical phenomena Phonon density of states MACS 2004 10-2-1 Structure of fluctuating systems Impurity dynamics Inelastic Scattering from small samples

  12. Intensity from Focusing MACS monochromator 1428 cm2 PG(002) MC Simulation Qiu and Broholm (2001)

  13. Upgraded Neutron Scattering Facilities at HFIR, ORNL

  14. Upgraded Neutron Scattering Facilities at LANSCE

  15. Aug 7 2001 May 2001

  16. Instruments for CMP at SNS

  17. Neutrons in the 21 century • Chemical and magnetic structure at the interfaces of nano-scale artificially structured systems • Excitations in materials patterned on the nano-scale • Protein structure (including D-positions) and dynamics • Complete 4 D Q-E mapping of dynamic correlation function for spin and lattice in large single crystals 0<E<100 meV • Systematic access to order parameters of weak or complex broken symmetry phases • Inelastic neutron scattering as a super-susceptometer for screening new materials • Parametric and complete information about structure of matter under extreme conditions

  18. Conclusions • Neutrons are great but we don’t have enough yet • New sources and instrumentation should produce a renaissance for the technique • New facilities must be easily accessible to non-neutron-experts to broaden the science program

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