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Striving for Excellence with MACS

Striving for Excellence with MACS. Collin Broholm Johns Hopkins University and NIST Center for Neutron Research. Introduction Virtues and limitations of INS Options for improving performance How MACS will achieve excellence Making best use of the NCNR cold source

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Striving for Excellence with MACS

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  1. Striving for Excellence with MACS Collin Broholm Johns Hopkins University and NIST Center for Neutron Research • Introduction • Virtues and limitations of INS • Options for improving performance • How MACS will achieve excellence • Making best use of the NCNR cold source • Organization of MACS project • Projected performance of MACS • Summary and observations

  2. Contributors to MACS project NIST Center for Neutron Research: G. Baltic, P. C. Brand, C. Brocker, M. English, P. D. Gallagher, C. J. Glinka, P. Kopetka, J. G. LaRock, J. W. Lynn, J. Moyer, N. Maliszewskyj, D. J. Pierce, M. Rowe, J. Rush, and others Johns Hopkins University: R. Barkhouser, C. Broholm, R. Hammond, P. K. Hundertmark, J. Orndorff, T. D. Pike, G. Scharfstein, S. A. Smee, and others

  3. Nuclear scattering Magnetic scattering Inelastic Neutron Scattering

  4. The Dynamic Phase Space for INS MSEL 6/17/04

  5. Spinon excitations in quantum spin chain (a) (b) (c) (d) Disintegration of spin flip into two spinons in uniform Spin-1/2 chain Binding of spinons by An applied staggered field

  6. Free spinons versus “chemical potential” CuPzN Uniform field only Stone et al., PRL (2003)

  7. Spinons form bound states in a staggered field CuCl2DMSO Uniform + staggered field Kenzelmann et al. PRL (2004)

  8. “Solving” Quantum Magnetism

  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 detection efficiency • Position sensitive detectors • Crystal analyzer arrays

  10. Brightness from cooling T=25 K NCNR cold source T=300 K

  11. L0=6.2 m Overview of MACS instrument

  12. The history of MACS • 1993 Discussions about the possibility of a “sub-thermal” TAS on NG0 • 1994 Analytical calculations show efficacy of double focusing at NG0 • Initiate JHU/NIST project to develop conceptual design • 1998 Top level specification for monochromator completed • JHU/NIST project starts to develop Doubly Focusing Monochromator • 2000 Christoph Brocker of NCNR starts engineering design work • NSF grant awarded • MACS monochromator completed at JHU • JHU employs Timothy Pike as project engineer • Concept design presentation at NCNR • 2003 Detailed design work begins • JHU hires Peter Hundertmark as mechanical designer • Don Pierce et al. of the NCNR begin work on beam line shielding • 2004 Receive first beam-line shielding bodies • Preliminary beamline installation • 2005 Spring: First beam on sample • Summer: Start of commissioning • 2006 Open for users through CHRNS

  13. Funding MACS

  14. Block Diagonalization of MACS Detection System (JHU@NIST) Sample positioning system (JHU@NIST) Monochromatic beam transp. (JHU@NIST) White Beam Conditioning System (NCNR) Monochromating system (JHU-IDG) Get Lost pipe (NCNR)

  15. Overview of MACS

  16. The Monochromator Cask Doubly focusing monochromator Collimators to control E-resolution Aperture to control Q-resolution Translation Stage to vary incident energy

  17. The MACS monochromator 357×4 cm2 PG(002) platelets with adjustable surface normal 35 cm 3×Hollow aluminum posts 45 cm 10B:Al shielding 10B:Al shielding Translation Stage Rotation Stage

  18. Worlds brightest monochromatic beam Y. Qiu (2002)

  19. Goals for Detection System • Maximize solid angle at fixed EF • Variable E and Q resolution • Minimize alignment needs • Minimize background and “spurions”

  20. Collimators to vary Q/E resolution Cryo-filters to reduce background 20 × spectroscopic detectors 20 × diffraction detectors 20 × double x-tal PG analyzers 20+20 Channel MACS detection system

  21. The Double Crystal Analyzer Unit • Variable energy 2.5 meV<E<15 meV • Vertically focusing “compound lense” • Background suppressing collimator • All motion controlled by a single stepping motor • Patent pending for Timothy Pike’s design

  22. Constant energy transfer slice kf ki Q

  23. Assembling slices to probe Q-E volume 2 meV 1 meV 0 meV

  24. Comprehensive information on Solid State dynamics 3D quantum liquid • Powder sample Q-E map • 8 x 30 pts x 0.2 min. = 1:00 • Single crystal complete Q-E Volume • 8 x 100 x 10 pts x 0.5 min.= 3 days Stone et al. Frustrated Magnet • Single crystal constant-E slice • 8 x 100 pts x 0.5 min. = 6:40 Lee et al. Pryde et al. Oxides that shrink when heated

  25. When can it start?

  26. Summary and Observations • NCNR/NSF/JHU collaboration has been an effective constellation for new science and instrumentation • MACS will be a formidable tool to probe nano-scale dynamics in condensed matter • Most intense cold neutron beam in the world • Multi-channel detection system • Greatest challenge to the project is availability of NIST instrumentation funding in FY05

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