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1、Striving for Excellence with MACS,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,Collin Broholm Johns Hopkins Un
2、iversity and NIST Center for Neutron Research,MSEL 7/8/04,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
3、 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,MSEL 7/8/04,Inelastic Neutron Scattering,MSEL 7/8/04,The Dynamic Phase Space for INS,MSEL 6/17/04,MSEL 7/8/04,Spinon excitations in quantum spin
4、 chain,Disintegration of spin flip into two spinons in uniform Spin-1/2 chain,Binding of spinons by An applied staggered field,MSEL 7/8/04,Free spinons versus “chemical potential”,Stone et al., PRL (2003),CuPzN,Uniform field only,MSEL 7/8/04,Spinons form bound states in a staggered field,Kenzelmann
5、et al. PRL (2004),CuCl2DMSO,Uniform + staggered field,MSEL 7/8/04,“Solving” Quantum Magnetism,MSEL 7/8/04,Expanding Applicability of a Powerful Probe,Increase source brightness Increase spectral brightness by cooling neutrons Increase temporal brightness in pulsed neutron source Improve beam deliver
6、y system Match solid angle to wave vector resolution requirements Match bandwidth to energy resolution requirements Increase detection efficiency Position sensitive detectors Crystal analyzer arrays,MSEL 7/8/04,Brightness from cooling,NCNR cold source,T=300 K,T=25 K,MSEL 7/8/04,Overview of MACS inst
7、rument,MSEL 7/8/04,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 pr
8、oject 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
9、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,MSEL 7/8/04,Funding MA
10、CS,MSEL 7/8/04,White Beam Conditioning System (NCNR),Monochromating system (JHU-IDG),Get Lost pipe (NCNR),Monochromatic beam transp. (JHUNIST),Sample positioning system (JHUNIST),Detection System (JHUNIST),Block Diagonalization of MACS,MSEL 7/8/04,Overview of MACS,MSEL 7/8/04,The Monochromator Cask,
11、Collimators to control E-resolution,Aperture to control Q-resolution,Doubly focusing monochromator,Translation Stage to vary incident energy,MSEL 7/8/04,The MACS monochromator,MSEL 7/8/04,Worlds brightest monochromatic beam,Y. Qiu (2002),MSEL 7/8/04,Goals for Detection System,Maximize solid angle at
12、 fixed EF Variable E and Q resolution Minimize alignment needs Minimize background and “spurions”,MSEL 7/8/04,20+20 Channel MACS detection system,MSEL 7/8/04,The Double Crystal Analyzer Unit,Variable energy 2.5 meVE15 meV Vertically focusing “compound lense” Background suppressing collimator All mot
13、ion controlled by a single stepping motor Patent pending for Timothy Pikes design,MSEL 7/8/04,Constant energy transfer slice,MSEL 7/8/04,Assembling slices to probe Q-E volume,MSEL 7/8/04,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.
14、= 3 days,3D quantum liquid,Frustrated Magnet,Comprehensive information on Solid State dynamics,Single crystal constant-E slice 8 x 100 pts x 0.5 min. = 6:40,Stone et al.,Lee et al.,Pryde et al.,Oxides that shrink when heated,MSEL 7/8/04,When can it start?,MSEL 7/8/04,Summary and Observations,NCNR/NS
15、F/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,