1. Conceptual design and performance of high throughput cold spectrometer : MACS Why MACS Layout and key elements Performance Data collection Scientific program Budget and schedule Conclusion Collin Broholm Johns Hopkins University and NIST Center for Neutron Research

2. NSF/NIST 10/19/00 MACS development team Overall instrument design Paul Brand NIST Christoph Brocker NIST Collin Broholm JHU Jeff Lynn NIST Mike Rowe NIST Jack Rush NIST Yiming Qiu JHU Focusing Monochromator Steve Conard JHU Joe Orndorff JHU Tim Reeves JHU Gregg Scharfstein JHU Stephen Smee UMD Shielding Calculations Charles M. Eisenhauer

3. NSF/NIST 10/19/00 Why cold neutrons and double focusing Q and E resolved spectroscopy requires Energy scale J varies more than length scale a To probe a range of materials must vary keeping To probe hard matter with low energy scales Reduce E i. Cold source provides the flux Increase angular divergence before and after sample

4. NSF/NIST 10/19/00 Kinematic limits for neutron scattering E fix and 2  range determine accessible Q-E space

5. NSF/NIST 10/19/00 Comparing TOF to TAS Larger detector solid angle E-scan with “no” moving parts Can use pulsed spallation source peak flux Larger detector solid angle E-scan with “no” moving parts Can use pulsed spallation source peak flux Can focus beams with Bragg optics Can select range of energy transfer Can use reactor CW flux Can focus beams with Bragg optics Can select range of energy transfer Can use reactor CW flux TAS like TOF like

6. NSF/NIST 10/19/00 NCNR Liquid Hydrogen cold source MACS Beam New cold source to be installed in 2001 will double flux

7. Overview of MACS Design by C. Brocker, C. Wrenn, and M. Murbach

8. NSF/NIST 10/19/00 Bragg focusing Source Sample Rowland Circle Focusing Monochromator Focusing Monochromator

9. NSF/NIST 10/19/00 Doubly Focusing Monochromator Design by Stephen Smee, G. Scharfstein et al.

10. NSF/NIST 10/19/00 Blade profile chosen so blades form arc when compressed S. Smee et al. Provisional patent pending (2000)

11. NSF/NIST 10/19/00 Focusing mechanics is out of beam Vertical Horizontal Design by Stephen Smee, G. Scharfstein et al.

12. NSF/NIST 10/19/00 Prototype performance 2 cm JHU IDG photo, prototype, and measurement

13. NSF/NIST 10/19/00 Constrained optimization : crystal mosaic Flux versus mosaic at fixed 0.2 meV energy resolution

14. NSF/NIST 10/19/00 Effects of cystal misalignment

15. NSF/NIST 10/19/00 Projected performance analytical approximation C. Broholm, Nucl. Instr. Meth. A 369 169-179 (1996)

16. NSF/NIST 10/19/00 Monte Carlo Simulation of MACS Y. Qiu and C. Broholm to be published (2000)

17. NSF/NIST 10/19/00 Resolution: Analytical and Monte Carlo simulations. Y. Qiu and C. Broholm to be published (2000)

18. NSF/NIST 10/19/00 Multiplexing crystal analyzer system Design by C. Brocker

19. One of twenty channels BeO filter Be filter PG filter Collimator 2 Collimator 1 8 o vertically focusing Analyzer crystals 8 o vertically focusing Analyzer crystals “TAS” detector Energy integrating Detector Energy integrating Detector Design by C. Brocker

20. NSF/NIST 10/19/00 Fixed vertical focusing of analyzers Double analyzer is “compound lens” efficient vertical focusing

21. NSF/NIST 10/19/00 Constant energy transfer slice kiki kfkf Q

22. NSF/NIST 10/19/00 Assembling slices to probe Q-E volume 0 meV 1 meV 2 meV

23. NSF/NIST 10/19/00 Projected data collection times  Powder sample Q-E map  8 x 30 pts x 0.2 min. = 1:00  Single crystal constant-E slice  8 x 100 pts x 0.5 min. = 6:40  Single crystal complete Q-E Volume  8 x 100 x 10 pts x 0.5 min.= 3 days CuHpCl SCGO

24. NSF/NIST 10/19/00 Scientific Program for NG0 spectrometer  Expanding the scope for Inelastic scattering from crystals:  0.5 mm 3 samples  impurities at the 1% level  complete surveys to reveal spin-wave-conduction electron interactions  extreme environments: pressure and fields to tune correlated systems  Probing short range order  solid ionic conductors, spin glasses, quasi-crystals, ferroelectrics, charge and spin polarons, quantum magnets, frustrated magnets.  Weak broken symmetry phases  Incommensurate charge, lattice, and spin order in correlated electron systems  Excitations in artificially structured solids  Spin waves in magnetic super-lattices  magnetic fluctuations in nano-structured materials

25. NSF/NIST 10/19/00 Probing hole wave function in oxide : 1 D 2D? Y 2-x Ca x BaNiO 5 Xu, Aeppli, Broholm, et al. Science (2000)

26. NSF/NIST 10/19/00 NSF Share (50%) of the Construction of MACS Design & Construction Design Construction & Design Construction & Assembly & Commissioning $k

27. NSF/NIST 10/19/00 Conclusions  Large solid angle access to NCNR cold source enables a unique cold neutron spectrometer.  MACS employs Bragg optics to focus the beam and provide > 10 8 n/cm 2 /s on the sample at 0.2 meV resolution.  The MACS detector concept offers the versatility, resolution, and low background of a TAS with 20 times greater data rate.  The highly efficient constant E mode of MACS will provide a unique capability for probing the structure of fluctuating systems.  MACS will be complementary to the DCS and future SNS TOF spectrometers because of its unique data collection protocol  NSF partnership is needed to realize the potential and make the unique capabilities available to widest possible cross section of the US scientific community