Status of Neutron Facilities in the US

Transcription

1 Status of Neutron Facilities in the US Dan Neumann with thanks to Peter Gehring

2 Uses of Neutrons Neutron Scattering Neutron Physics Neutron Imaging Activation Analysis Isotope Production Materials Testing Transmutation Doping

3 Why Neutron Scattering 1) Simplicity of the interaction allows easy interpretation of intensities Easy to compare with theory and models 2) Appropriate energy and momentum transfer Geometry of motion 3) Neutrons scatter by a nuclear interaction => different isotopes scatter differently 4) Neutrons have a magnetic moment D C O Si H

4 Why Neutron Scattering 1) Simplicity of the interaction allows easy interpretation of intensities Easy to compare with theory and models 2) Appropriate energy and momentum transfer Geometry of motion 3) Neutrons scatter by a nuclear interaction => different isotopes scatter differently 4) Neutrons have a magnetic moment D C O Si H

5 Total Scattering Cross Sections As compared with x-ray scattering cross sections, which vary as Z 2, neutron scattering cross sections show little systematic variation with atomic number. x-rays (Q=0) neutrons H D C N O Al Si Fe X-ray cross sections vary with scattering angle neutron cross sections do not

6 Solving Multi-Phase Structures Contrast Matching - reduce the number of phases visible r solvent = r core (shell visible) or r solvent = r shell (core visible) The two distinct 2-phase systems can be easily understood

7 Energy Materials Energyefficient gas CH 4 storage JACS 136, 6207 (2014). separations Science 335, 1606 (2012). Superionic conductors First in-situ characterization of the SEI layer Chem. Mater. 24, 2133 (2012). Adv. Energy Mater. 6, (2016).

8 Soft Materials Complex fluids under flow Concentration gradients in a shear-banding fluid PRL 105, (2010). Hydrogels Vitreous humor replacement Nature Biomed. Eng. 1, 0044 (2017). Megasupramolecules Density of the gel phase in concrete Nature Materials 6, 311 (2007) Science 350, 72 (2015).

9 Biology and Biotechnology Structure of voltage-sensing domains in biomembranes Biopharmaceutical Formulations Oncolytic virus T-Vec Nature 462, 473 (2009). Biomolecular complexes Thickness fluctuations in lipid bilayers PRL 109, (2012). Familial hypertrophic cardiomyopathy PNAS 105, (2008). J. Mol. Bio. 377, 1186 (2008).

10 Why Neutron Scattering 1) Simplicity of the interaction allows easy interpretation of intensities Easy to compare with theory and models 2) Appropriate energy and momentum transfer Geometry of motion 3) Neutrons scatter by a nuclear interaction => different isotopes scatter differently 4) Neutrons have a magnetic moment D C O Si H

11 Magnetic Materials Quantum Spin Liquids Skyrmions Nature 492, 406 (2012). Fe-based Superconductors Nature 453, 899 (2008). Science 323, 915 (2009). Magnetic Topological Insulators Nature Materials 16, 94 (2017). J. Phys. Soc. Jpn. 78, (2009). Science 326, 411 (2009). Magnetic Monopoles

12 Uses of Neutrons Neutron Scattering Neutron Imaging Neutron Physics Activation Analysis Isotope Production Materials Testing Transmutation Doping

13 Neutron Imaging Paleontology Sinus evolution in dinosaurs WCNR-10 (2014). Engineering PEM Fuel Cells Cultural Heritage Japanese Swords J. Power Sources 209, 147 (2012). Electrochim. Acta 55, 2734 (2010). Failure Analysis Battery from Dreamliner NTSB-DCA13IA037 Physics Procedia 60, 327 (2014).

14 Neutron Physics emit Most precise measurement of the D coefficient PRL 107, (2011). Neutron Lifetime Phys. Lett. B 605, 72 (2005). PRL 111, (2013). PERKEO Most precise measurement of the A correlation coefficient Testing the Standard Model nedm PRL 110, (2013).

15 Activation Analysis Batteries 3D Li distributions Cultural Heritage 6 th century disc fibula J. Anal. Atomic Spectrom. 28, 1508 (2013). J. Power Sources 287, 226 (2015). Origin of Mayan pottery SRM 1632e The Environment Trace elements in bituminous coal Arqueología 42, 151 (2009).

16 Production of Neutrons with Reactors Neutrons are liberated by fission of 235 U

17 Production of Neutrons with Spallation From Roger Pynn

18 Moderating Neutrons Maxwellian Distribution F ~ v 3 e (-mv2 /2k B T) 1 mev 12 K ¼ THz

19 Hot, Thermal and Cold Neutrons Hot neutrons wavelengths ~ 0.7 Å (170 mev) Thermal neutrons - wavelengths ~ 2 Å (20 mev) Cold neutrons - wavelengths ~ 6 Å (2.3 mev)

20 Neutron Sources in the World

21 2 Research Reactors World-wide

22 Major Neutron Facilities in the World 4

23 Major Neutron Facilities based on Reactors 5

24 Neutron Sources Neutron Scattering Neutron Physics Neutron Imaging Activation Analysis Isotope Production Materials Testing Transmutation Doping Most important aspects of the source 1) FLUX 2) Reliability 3) Capacity 4) Cost-effectiveness

25 Source Improvement is Evolutionary

26 Instruments for Neutron Scattering Brockhouse invented the triple-axis spectrometer in the 1950 s Bertram Brockhouse The NRU reactor is still operational and still has triple-axis instruments reactors haven t changed much Data rates on triple-axis instruments have increased by 4 orders of magnitude

27 Instrument Improvements 1) Beam Optics 2) Detectors 3) Better Devices

28 Better Optics - Monochromators Large focusing monochromators 60 cm vs 10 cm

29 Better Optics Neutron Guides Converging Guide

30 Slide due to P. Böni Advanced Neutron Guides q cni = 1⁰/nm l q c = mq cni m = 8

31 Advanced Neutron Guides

32 Better Optics Wolter Optics Faint x-ray sources (nebula, etc.) need to be focused for good imaging CHANDRA mirrors are coated on 2 cm thick glass substrates NASA has developed a new fabrication technique to create Wolter Optics from nested Ni-foil mirrors light for space telescopes and perfect for neutrons Reflection is achromatic, Wolter Optics have reasonable off-axis properties Focusing may yield 100x gain

33 Wolter Optics

34 Instrument Improvements 1) Beam Optics 2) Detectors 3) Better Devices

35 Large Analyzer Area 12 m 2 Si analyzer on a backscattering instrument 20 Analyzer channels on a descendant of the Brockhouse instrument

36 Large Detector Area Scattering chamber on LET at ISIS. This chamber accommodates 4 m tall position sensitive detectors

37 Energy Dispersive Detectors

38 Energy Dispersive Detectors

39 More Ideas for Multiplexed Analyzers

40 Instrument Improvements 1) Beam Optics 2) Detectors 3) Better Devices

41 Advances in Neutron Research Progress in the science pursued at neutron facilities over the past 50 years has been driven primarily by major improvements in neutron beam instrumentation. More advances are on the horizon so we expect this to continue.

42 US and Europe 2007 By basically any measure, the US neutron scattering community was 35% of that in Europe. This includes publications in high-impact journals

43 Instrumentation A 2009 APS report on access to facilities states To improve access and to enable the user community to grow it is critically important to increase the number of instruments at major facilities in the US. The size of the US user community is currently limited by the number of instruments. It also states: Scientifically successful access today, especially for new users, depends on the active assistance and collaboration of facility instrument scientists at a scientific level.

44 Instrumentation The 2002 OSTP report emphasized that the expense of building and operating neutron sources requires that they be fullyinstrumented and that the instruments be well-staffed. It also pointed out that the SNS alone cannot meet US needs for neutron scattering capability.

45 SNS - 19 Beam Instruments 5 thermal instruments 14 cold instruments 1 under construction

46 HFIR - 15 Beam Instruments 8 thermal instruments 7 cold instruments 1 under construction

47 NIST - 28 Beam Instruments 7 thermal neutron instruments 21 cold neutron instruments 2 under construction MACS BT1 PD NIF DARTS BT7 TAS BT5 usans BT4 FANS/TAS CHRNS NG7 Refl SPINS NIOFa NIOF PBR CANDoR NSE NDP PHADES PGAA MAGIk HFBS nsoft MDM DCS NG7 SANS 30m SANS Neutron Lifetime vsans PHYS CNI

48 Neutron Scattering Instruments

49 Neutron Sources in the World

50 Number of Instruments neutron scattering instruments world-wide 48 neutron scattering instruments in the USA Europe dominates in number of instruments number of users scientific productivity

51 Major Neutron Facilities in the World

52 Number of Instruments 2017 Neutron scattering and imaging instruments at major facilities fed by a reactor 10 MW or a spallation source 280 neutron scattering instruments world-wide 140 in Europe 45 in the USA

53 Major Neutron Facilities based on Reactors 5

54 Number of Instruments at Reactors % of neutron scattering instruments at major facilities are at reactors rather than spallation sources 200 instruments 60% of neutron scattering instruments in the USA are at NIST and HFIR 27 instruments

55 Major Neutron Facilities in the World

56 Major Neutron Facilities in the World

57 Number of Instruments Neutron scattering and imaging instruments at facilities fed by a reactor 10 MW or a spallation source 240 neutron scattering instruments world-wide 110 in Europe 45 in the USA

58 2 Research Reactors World-wide

59 Research Reactors: HEU and LEU 3

60 Major Neutron Facilities based on Reactors 5

61 6 HEU and LEU

62 HEU and LEU Potential 20 MW LEU Reactor compared to current NIST HEU Reactor

63 HEU and LEU IF a reactor can go critical using LEU, the loss on conversion from HEU to LEU typically does not significantly affect performance for beam experiments. The NCNR will lose about 10%. New D 2 cold source to compensate 1 year instrument improvement

64 Neutron Capabilities

65 C & E News Feb. 22, 2010 Vol. 88 Issue 8 "As far as I'm concerned, neutrons are the most powerful structural probe that inorganic and materials chemists have to characterize their materials, Robert Cava/Princeton The crystal structure of PbMn 5 (SO 4 ) 6 incorporates chains of alternating MnO 6 -Pb polyhedra surrounded by Mn 2 O 9 dimers and SO 4 tetrahedra.