Neutron Scattering under Extreme Conditions at the Spallation Neutron Source

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1 Neutron Scattering under Extreme Conditions at the Spallation Neutron Source Jamie Molaison Oak Ridge National Laboratory International Workshop on Synchrotron High Pressure Mineral Physics and Materials Science Argonne National Laboratory -

2 Collaboration John Parise - Stony Brook University H.-k. Mao, R. J. Hemley - Carnegie Institution of Washington Gene Ice - Oak Ridge National Laboratory Darren Locke, Lars Ehm, Dave Martin - Stony Brook University Ian Swainson, R. Rogge, L. Cranswick - NRC CNBC Chalk River

3 Neutrons and Neutron Sources You can work in extreme sample environments (T, P,...) e.g. He cryostat (Shull & Wollan) and penetrate into dense samples Sensitivity to a wide range of properties, both magnetic and structural The magnetic and nuclear cross-sections are comparable, nuclear cross-sections are similar across the periodic table uc/rfg

4 EXAMPLE: Spin Reorientation in α-fe 2 O 3 up to 70 kbar at room temperature C2 (NRC), WAND Intensity of (111) peak drops with increasing pressure 70 kbar z EOS and transitions in ice used to deter. P x y Hexagonal structure, vectors indicate spin directions along the c axis above 70 kbar Remaining Ice VI Ice VII [110] peak of transformed sample Spin vector angle w.r.t c-axis Ice VI 1600 Ice VI Intensity GPa (545 bar) 2.58 GPa (600 bar) 3.69 GPa (700 bar) 4.40 GPa (800 bar) 5.23 GPa (900 bar) 5.85 GPa (990 bar) 6.41 GPa (1050 bar) Ice VI Ice VII magnetic peaks nuclear peaks theta (degrees)

5 Pressure Ranges and Neutron Scattering Adapted from N. W. Ashcroft E-F School Verenna Italy 2001 Pressure (Atm) 1E28 1E18 1E E-12 1E-22 1E-32 P at center of neutron star P at center of white-star P cosmic microwave BG non-equilibrium P of hydrogen in intergalactic space Metallic Hydrogen P at center of Earth (~350 GPa) P where H2O freezes at 100 o C Pressure at greatest ocean depth Atm P at sea level Vapor P of water at triple point Sound at threshold of pain Radiation P at Sun Existing Pressure Devices core-mantle boundary (100 GPa) PIA in quartz densification of silica PIA in ice high pressure X'll forms Chemsitry under pressure high pressure (compound/bio) Available at Current Neutron Sources 1 Atm = 1 bar, 10 kbar = 1 GPa 100 Gpa = 1 Mbar

6 SNAP Pressure Cells Paris-Edinburgh (P-E) Design Panoramic Design Beijing-Washington First Gen Design Second Gen First Gen Second Gen Large volume: ~80 mm 3 Sample size = 100 µm (linear) to 1 mm 3 Large volume: mm 3

7 SNAP Research Cell Testing Pair Distribution Function Densification process glassy water. Tulk, et al. PRL, 97, 2006 K.W. Chapman, P.J. Chupas, D. Locke, J.B. Parise 2006 in preparation CaSiO 3 glass up to 90 kbar, x-ray data, L. Ehm, D. Locke, et al. rhombohedral orthorhombic tetragonal cubic 250 BaTiO3 Q(S(Q)-1) Xe Hydrate, in situ measurement 3.5 GPa 2.6 GPa I(Q) Atomic Form Factor GPa GPa Q (angstroms^-1) Q (angstroms^-1) N. C. Hyatt (Sheffield), J. A. Hriljac (Birmingham), et al. Studies of guest cluster geometry in high pressure clathrate hydrates

8 The Spallation Neutron Source SNS construction finished in 2006, $ 1.4 billion construction cost Full power = 1.4 MW. SNS is now producing neutrons at approximately ISIS power levels, plans to increase power. It is a short drive to HFIR, a reactor source with a flux comparable to the ILL

9 Target Building and Instrument Layout Beam Line 11A Powder Diffractometer Beam Line 12 Single Crystal Diffractometer (TOPAZ) Beam Line 7 Engineering Diffractometer (VULCAN) Beam Line 4B Liquids Reflectometer Beam Line 17 Chopper Spectrometer (SEQUOIA) Beam Line 18 Chopper Spectrometer (ARCS) Proton Beam Beam Line 4A Magnetism Reflectometer Beam Line 3 High Pressure Diffractometer (SNAP) Beam Line 2 Backscattering Spectrometer

10 SNAP Overview and Status Support labs & mezzanine Enclosure Ceiling & Hatch Stacked Shielding Choppers & Supports Shutter & Core Vessel Insert Beam Stop Instrument Enclosure Sample Position & Detectors Flight Tube Assembly P-I-P Shielding

11 View at the Sample Position

12 Instrument Enclosure

13 Instrument Components in the Field

14 Focusing Mirrors: The KB Concept Two curved neutron super mirrors - One focusing vertically - One focusing horizontally

15 Bending is Practical Option for SNAP Mirrors Monolithic figuring ~$400K not in SNAP budget bending moments mirror bending moments Differential deposition Not right scale for neutron mirrors (too thick) Bending Widely used-cost effective leaf spring bending moments mirror bending moments

16 Micro beams for high pressure neutron scattering Doubly Focused Prototype micro-focusing mirrors NRU reactor at CRL (NRC) Measured spot size ~ 110 x 110 µm Signal saturated at Tulk, Ice, Locke, Xu, Parise, et al. (2004), ORNL, NRC, Stony Brook and Carnegie Institution.

17 Measuring the Spot Size 109 microns in the Horizontal 111 microns in the Vertical

18 Microdiffraction from Free-standing Crystal 300 x 300 x 700 µm irregular forsterite (Mg 2 SiO 4 ) single crystal Rotated 360 o in 20 o steps about Φ Focused run gave 701 reflections, unfocused gave 368 (196 common) Avg. peak int./scatt. vol. (counts/µm 3 ) focused beam unfocused beam rotation angle (degrees)

19 Pressure cells coupled with mirrors at CNBC-Chalk River Looks very much like an x-ray hutch at a synchrotron facility - utilize sample alignment - utilize sample HT-LT environment techniques

20 Microdiffraction from pressurized sample 200 x 500 µm FeO single crystal in panoramic cell at ~7 GPa 700 µm sample 90 µm beam 200 µm sample

21 Advanced K-B Mirrors for SNAP Nested geometry can be farther from sample Theoretical increase of ~2.5 in flux vs. standard K-B geometry

22 THANK YOU!