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NMI3 meeting, ISIS, September 26-29, 2005 Contents: Overview of new capabilities of the RESTRAX software Numerical optimizations of TAS parameters Virtual.

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Presentation on theme: "NMI3 meeting, ISIS, September 26-29, 2005 Contents: Overview of new capabilities of the RESTRAX software Numerical optimizations of TAS parameters Virtual."— Presentation transcript:

1 NMI3 meeting, ISIS, September 26-29, 2005 Contents: Overview of new capabilities of the RESTRAX software Numerical optimizations of TAS parameters Virtual TAS experiments - simulations with selected sample kernels Recent developments of RESTRAX Optimization of neutron optics and virtual triple-axis experiments Jan Šaroun 1, Jiří Kulda 2, Vasyl Ryukhtin 1 1 Nuclear Physics Institute, Řež 2 Institute Laue-Langevin, Grenoble RESTRAX homepage::http://omega.ujf.cas.cz/restrax/http://omega.ujf.cas.cz/restrax/

2 SIMRES Version for instrument optimizations - more detailed simulation of TAS components - mapping neutron beam in phase-space - tools for numerical optimization

3 NMI3 meeting, ISIS, September 26-29, 2005 SIMRES - virtual triple axis spectrometer collimator segments source sample crystals detector + setups that can be mapped onto a classical TAS layout (powder and strain diffratometers) multi-purpose components: source: arbitrary energy, spatial and angular distributions via look-up tables crystals: focusing arrays of elastically bent or mosaic crystals (incl. simulated extinction effects, absorption, etc...) collimators: universal components describing: Sollers, curved guides or benders, elliptic or parabolic guides, lobster-eye devices multiplexing: flat-cone multianalyzer and multidetector systems

4 NMI3 meeting, ISIS, September 26-29, 2005 Ray-tracing & numerical optimizations Fixed setup  fast ray-tracing code, 10 3 -10 4 counts/sec  ray-tracing results are used to find extremum of fm numerically. figure of merit, fm(a 1, a 2,...): I... incident intensity  E... energy spread I /  E, I /  E 2... inelastic scattering I / , I /  2... diffraction free parameters, a 1, a 2,... a n crystal curvature, mosaicity, cutting angle, guide dimensions, curvature, divergence,... Speed problem: number of simulations / iteration = 1+2n 2 n  4 acceptable (CPU time < 1 hour)

5 NMI3 meeting, ISIS, September 26-29, 2005 Lobster-eye device & focusing monochromator spatial focusing monochromatic beam + spatial focusing ? Simultaneous optimization of the crystal curvatures and guide parameters –mutual correlations –ray-tracing: realistic model of the instrument components monochromatic focusing

6 NMI3 meeting, ISIS, September 26-29, 2005 Lobster-eye device & focusing monochromator Lobster-eye device 20 (hor.) or 30 (ver.) blades thickness 0.5 mm m=3 supermirror (concave sides) elliptic & parabolic profiles optimization: entry & exit width TAS - IN14 setup cold source straight 58 Ni guide, 6x12 cm 2 monochromator: PG 002, doubly focusing, =4.05 Å target (sample) area: 3x3 mm 2 optimization: crystal curvatures

7 NMI3 meeting, ISIS, September 26-29, 2005 Parabolic guide Focusing on small samples + perfect focusing of a parallel beam - large reflection angle at the entry

8 NMI3 meeting, ISIS, September 26-29, 2005 Focusing on small samples Elliptic guide - parallel beam does not focus to a point + lamellae are parallel at the entry

9 NMI3 meeting, ISIS, September 26-29, 2005 Lobster-eye device & focusing monochromator Optimization in 2 dimensions x Mapping the parameter space horizontal: 1) monochromator: 1/R H 2) guide: exit width vertical: 1) monochromator: 1/R V 2) guide: exit height adjustable parameters: Resolution 32x32 pixels  1024 simulations Number of blades is fixed  adjusting focal distance

10 NMI3 meeting, ISIS, September 26-29, 2005 Mapping of parameter space Elliptic blades Optimization route in 2 dimensions Intensity/  E Intensity horizontalvertical

11 NMI3 meeting, ISIS, September 26-29, 2005 Mapping of parameter space Parabolic blades Optimization route in 2 dimensions Intensity/  E Intensity horizontalvertical

12 NMI3 meeting, ISIS, September 26-29, 2005 Lobster-eye device & focusing monochromator Optimization in 3 dimensions horizontal: 1) monochromator: 1/R H 2) guide: entry width 3) guide: exit width vertical: 1) monochromator: 1/R V 2) guide: entry height 3) guide: exit height adjustable parameters: mapping in 3D is not feasible  32768 simulations/map … Number of blades is fixed  adjusting focal distance and spacing between blades

13 NMI3 meeting, ISIS, September 26-29, 2005 Lobster-eye device & focusing monochromator Optimization in 3 dimensions Elliptic blades

14 NMI3 meeting, ISIS, September 26-29, 2005 Lobster-eye device & focusing monochromator Optimization in 3 dimensions Parabolic blades

15 NMI3 meeting, ISIS, September 26-29, 2005 Lobster-eye device & focusing monochromator Optimization in 3 dimensions Focusing monochromator only

16 NMI3 meeting, ISIS, September 26-29, 2005 Lobster-eye device & focusing monochromator Optimization in 3 dimensions Results Total intensity (whole beam) [10 9 /s]: parabolic1.3 elliptic1.6 no3.4

17 RESTRAX Version for TAS resolution simulations and data analysis - simplified TAS setup with faster ray-tracing code - 4D resolution functions + convolution with S(Q,  ) - dynamically loaded modules with S(Q,  ) model - non-linear data fitting

18 NMI3 meeting, ISIS, September 26-29, 2005 Sample “exchanger” in RESTRAX TAS ray-tracing, R(Q,  ) 4D convolution data simulation data fitting dynamically loaded modules, S(Q,  ) Damped harmonic oscillators Damped harmonic oscillators, free dispersion gradient Bond charge model (phonons in Si, Ge,...) Incommensurate fluctuations (diffuse satellites) … others defined by users

19 NMI3 meeting, ISIS, September 26-29, 2005 TAS: conventional arrangement monochromator sample analyzer detector

20 NMI3 meeting, ISIS, September 26-29, 2005 TAS: flat-cone analyzer monochromator sample analyzer detector

21 NMI3 meeting, ISIS, September 26-29, 2005 TAS: flat-cone multianalyzer monochromator sample analyzer detector

22 NMI3 meeting, ISIS, September 26-29, 2005 Sweeping reciprocal space New flat-cone analyzer for ILL TAS instruments, 32 channels IN20: monochromator Si, k i =3 A -1 non-linear scans in rec. lattice a3a3 a4a4

23 NMI3 meeting, ISIS, September 26-29, 2005 Example 1: Incommensurate sattelites Incommensurate sattelites:  E  210210 010 200 210 000 010010 110110 E raw data M.C. ray-tracing & convolution with S(Q,E)

24 NMI3 meeting, ISIS, September 26-29, 2005 Example 1: Incommensurate satellites... and transformed to rec. lattice space

25 NMI3 meeting, ISIS, September 26-29, 2005 Example 1: Incommensurate satellites detail...

26 NMI3 meeting, ISIS, September 26-29, 2005 Example 2: bond charge model (BCM) Model describing phonons in diamond lattice (Si, Ge,  -Sn,...) Eigenvalues & eigenvectors are calculated using coulombic potential of bond charges for each of Q,E points representing simulated TAS resolution function W. Weber, Phys. Rev. B 15 (1977) 4789. phonons in Si

27 NMI3 meeting, ISIS, September 26-29, 2005 Phonons in Si E=10 meVE=20 meV

28 NMI3 meeting, ISIS, September 26-29, 2005 Phonons in Si E=30 meVE=40 meV

29 NMI3 meeting, ISIS, September 26-29, 2005 Phonons in Si E=50 meVE=60 meV

30 NMI3 meeting, ISIS, September 26-29, 2005 E=20 meV Phonons in Si MC simulation for IN20 k f =3A -1, E=20meV 64 channels,  a4=1.25 o 91 steps,  a3=0.75 o convolution with flat-cone resolution simulated by ray-tracing CPU time: 4 hours

31 NMI3 meeting, ISIS, September 26-29, 2005 Summary Numerical optimizations using ray-tracing simulations in numerical optimization is feasible multiple correlated TAS parameters can be optimized with respect to different figures of merit Lobster-eye guides high flux at small samples, leaves space for sample environment vertical and horizontal focusing can be splitted in 2 guide sections alternative to focusing monochromators at quasiparallel beams Dynamically loaded S(Q,  ) modules data simulations and fitting with various sample kernels extensions provided by users RESTRAX homepage::http://omega.ujf.cas.cz/restrax/http://omega.ujf.cas.cz/restrax/

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