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 packages a) Enable users to simulate new instruments (FRM-2, ISIS TS2, FZJ, ANSTO, J-PARC, SNS, …) b) Understand/upgrade existing instruments c) Lay the foundation for all simulation activities Why not just one package? a) Scientific; intercomparisons reveal subtle errors b) Innovative; good ideas survive and spread

5. Packages III. Optimization of optics: Guide dimensions (VITESS) Beam focusing device (RESTRAX; automatic optimization) 50 cm 30 cm 50 cm 8 cm 12.5 0.00.20.40.6 70 80 90 100 110 120  V [m ] exit height [mm]

6. Packages IV: The grid

7. Code validation I Cold neutron powder diffractometer DMC @ PSI McStas vs. Real exp. Sample Na 2 Ca 3 Al 2 F 14 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 model c) Input from instrument control program d) Data analyzed by standard data analysis programs What can virtual experiments be used for? a) Virtual tests of proposed instruments b) Feasibility studies of planned experiments c) 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)