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Status of JRA6 - MCNSI

Status of JRA6 - MCNSI. Kim Lefmann NMI3, ISIS, 28/9-05. What is MCNSI ?. Monte Carlo Simulations for Neutron Scattering Instruments Development of packages , Vitess, ResTrax, and McStas Cross comparison between codes and with exp. Tools for virtual experiments

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Status of JRA6 - MCNSI

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  1. Status of JRA6 - MCNSI Kim Lefmann NMI3, ISIS, 28/9-05

  2. What is MCNSI ? • Monte Carlo Simulations for Neutron Scattering Instruments • Development of packages, Vitess, ResTrax, and McStas • Cross comparison between codes and with exp. • Tools for virtual experiments • HMI, NPI, Risø, PSI, ISIS, ILL, INFM (+SNS, +ANSTO)

  3. Packages I • RESTRAX, NPI/ILL, version 4.8 (April 2005)+ both ray-tracing and data analysis- continuous sources only • VITESS, (HMI), version 2.6 (June 2005)+ polarization included, also pulsed sources- • McStas, Risø/ILL, version 1.9 (October 2005, beta yesterday!)+ detailed samples++ , also pulsed sources- no polarisation (yet)

  4. Packages II • Use of MC packagesa) Enable users to simulate new instruments (FRM-2, ISIS TS2, FZJ, ANSTO, J-PARC, SNS, …) b) Understand/upgrade existing instrumentsc) Lay the foundation for all simulation activities • Why not just one package?a) Scientific; intercomparisons reveal subtle errorsb) Innovative; good ideas survive and spread

  5. Packages III . Optimization of optics: • Guide dimensions (VITESS) • Beam focusing device (RESTRAX; automatic optimization) 120 110 8 cm 100 exit height [mm] 90 12.5 80 50 cm 70 30 cm 0.0 0.2 0.4 0.6 50 cm -1  [m ] V

  6. Packages IV: The grid

  7. Code validation I • Cold neutron powder diffractometer DMC @ PSI • McStas vs. Real exp. • Sample Na2Ca3Al2F14 • Background from V can • Very good agreement!… but intensity scaling • Many other efforts, e.g. OSIRIS@ISIS; FOCUS@PSI; ILL; FRM2

  8. Virtual experiments I • What is a ”true” virtual experiment?a) Simulation of a complete instrument, source to detector b) …including a realistic sample modelc) Input from instrument control programd) Data analyzed by standard data analysis programs • What can virtual experiments be used for?a) Virtual tests of proposed instrumentsb) Feasibility studies of planned experimentsc) Understanding of data (background, multiples)d) Teaching (Students, general public)

  9. Virtual experiments, II • REXTRAX model of IN20@ILL with 32 analyzers in flat-cone geometry • Sample: phonons in Si • Q-map at constant-E (20 meV)

  10. Virtual experiments, III • Course on neutron scattering • Univ. Copenhagen, 2005 • 9 students, 3 groups • 4th year undergraduates • 3 virtual experiments • 1 real experiment (PSI) • VERY good learning progress!

  11. Virtual experiments, IV . • Realistic sample simulation (multiples, sample environment) • FOCUS @ PSI; McStas • New component: Isotropic S(q,ω); concentric

  12. MCNSI - prospects • Packages: • Standard modules: truly reliable and user friendly • Approaching detailed sample description • Still few major features and many details missing • Virtual experiments: • Proof of concept performed • Potentially a very powerful tool (training, data analysis, …) • Much work needed! (in collaboration with facilities)

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