status of jra6 - mcnsi kim lefmann nmi3, isis, 28/9-05
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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
• HMI, NPI, Risø, PSI, ISIS, ILL, INFM (+SNS, +ANSTO)
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)
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
Packages III .
Optimization of optics:
• Guide dimensions (VITESS)• Beam focusing device
(RESTRAX; automatic optimization)
50 cm30 cm
50 cm
8 cm
0.0 0.2 0.4 0.670
80
90
100
110
120
V [m-1
]
exit
heig
ht [m
m]
Packages IV: The grid
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
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)
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)
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!
Virtual experiments, IV .
• Realistic sample simulation (multiples, sample environment)
• FOCUS @ PSI; McStas
• New component: Isotropic S(q,ω); concentric
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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