Reflectometry in DANSE Paul Kienzle 1 and John F. Ankner 2 1 NIST Center for Neutron Research 2 Spallation Neutron Source, ORNL

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Reflectometry in DANSE August 15, 2006 Reflectometry M1 M2 detector θ 2θ Beam Image apertures

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 3 Reflectometry in DANSE August 15, 2006 Specular reflectivity layer models r0r0 tLtL Parratt recursion formula

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 4 Reflectometry in DANSE August 15, 2006 Challenge #1  Challenge: Fitting even a relatively simple specular reflectivity curve requires hours of effort by a skilled user  Solution: Direct methods and data inversion

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Reflectometry in DANSE August 15, 2006 Fitted Data

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Reflectometry in DANSE August 15, 2006    Landscape (d 3 vs d 2 )

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 7 Reflectometry in DANSE August 15, 2006 Challenge #2  Challenge: SNS data rates will exceed those of current instruments by factors of , enabling extensive parametric studies in both thermodynamic variables and time. We must self-consistently invert/model entire data sets.  Solution: Apply or develop appropriate multi-data-set minimization routines

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Reflectometry in DANSE August 15, 2006 Flexibility of DANSE framework Model 1 Model 2 Model 3... Model k Parameters Sum X 2 Nelder Mead Simplex Levenberg Marquardt Genetic Algorithms Multiple data-set refinement

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 9 Reflectometry in DANSE August 15, 2006 Challenge #3  Challenge: Improve “lines of communication” between simulation techniques (MD, micro-magnetics, etc.) and neutron scattering data  Solution: Develop the appropriate software

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 10 Reflectometry in DANSE August 15, 2006 Molecular dynamics and reflectivity

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 11 Reflectometry in DANSE August 15, 2006 Challenge #4  Challenge: SNS instruments will feature gnarly resolution functions  Solution: Fit/model data as it looks to the instrument. Don’t reduce data so much as simulate it. Possibly more natural way to incorporate MD simulation as well.

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 12 Reflectometry in DANSE August 15, 2006 Wavelength vs. tof Choppers set to deliver 2.5 Å < < 6 Å

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 13 Reflectometry in DANSE August 15, 2006 Challenge #5  Challenge: Next-generation reflectometers will be capable of measuring an extensive off-specular Q range. We lack robust modeling capability for this type of data.  Solution: Adapt/develop (2+1)D modeling algorithms and make them user-friendly

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 14 Reflectometry in DANSE August 15, 2006 Reflection geometries Specular α i  α f θ  0 Off-Specular α i  α f θ  0 GISANS α i  α f α i, α f  α c θ  0 Specular: Q = 4π  sinα  λ

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 15 Reflectometry in DANSE August 15, 2006 The SNS Liquids Reflectometer [Manufactured by JJ X-Ray] 0 ≤ α liquid ≤ 5.5° 0 ≤ 2α ≤ 90° 0 ≤ 2θ ≤ 30°

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 16 Reflectometry in DANSE August 15, 2006 Adapt NIST Reflpak to tof at SNS Reduction Analysis Common Platform

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Reflectometry in DANSE August 15, 2006 Current Capabilities Simulat e Reduce Fit Model Analytic Freefor m User

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Reflectometry in DANSE August 15, 2006 Planned Capabilities Simulat e Reduce Fit Model Analytic Structur al Freefor m User OOMM F NAMD GROM ACS Invert

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Reflectometry in DANSE August 15, 2006 Reflectometry DANSE project status First SNS reflectometer beam July 2006 Have initial data viewer for SURF First data October 2006 Fit program already in use for TOF neutron and fixed- neutron and X-ray data Users include undergrads from NIST summer research program Current developers are UMD undergrads Will hire developer, postdoc and grad student in Y1

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Reflectometry in DANSE August 15, 2006 Interface Builder ModelInterface Text field Graph Button Data Title CountsVector Methods TransformData Component Network...

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 21 Reflectometry in DANSE August 15, 2006 Simulated SNS reflectometer performance 10 Å SiO 2 /Si Q = 4π sinα / λ