Brent FultzProf. Materials Science and Applied Physics
California Institute of Technology
• ARCS Project• Inelastic Scattering• Scope of Software Project• Project Management • Project Status
/Users/btf/ARCS/arcs.swf
ARCS Project Budget
Hardware: 10.0 M$
Contingency: 2.0 M$
Software: 2.9 M$
Software effort is 0.58 M$/year postdoctoral fellows, graduate students, professionalsA relatively small amount for hardware
Software Engineering -- Scope and Style
• Data Stream and Component Design
• Server/Client Development (GUI)
• Platform and OS Support
• Work on NeXus
• Doing Python/C++ by hand
• CVS Repository, Documentation, www
Scientific Scope
• Data Reduction -- traditional approach to S(Q,E)
• Model Calculations of S(Q,E)
• Simulations of Data
• Interactions of Above
Diffraction: (coherent, elastic)
Dynamics in space and time
Diffraction misses the time dependence
(incoherent, inelastic) vs. (coherent, inelastic)
Diffraction E=0
F[I(Q)] = P(r)
Inelastic
F F [I(Q,E)] = Γ(r, )tQE
Software Roadmap v. 1.0
Data Reduction
• Account for incident flux• Remove background• Convert from time to energy• Correct for detector efficiency• Bin into rings of constant scattering angle• Convert from angle to momentum • Subtract multiphonon and multiple scattering• Correct for absorption
Baseline Simulations for the ARCS Project.
1. Lattice dynamics with a Born--von Karman model (periodic structure)
2. Spinwave dynamics with a Heisenberg hamiltonian on a periodic structure
3. Lattice dynamics on a disordered structure, using a moments analysis of the dynamical matrix
4. Spin dynamics in a paramagnetic model
Crystal model C1XX, C1XY…
Calculate force constant matrix Phi_{alpha beta}(0 l_ kappa kappa_)
Sweep reciprocal space
End?
Calculate dynamical Matrix D(q)
Diagonalize D(q)
Update DOS histogram
Output DOS
Powell minimization of force-constantsguess
Compare with experimental DOS
RMS Converged
?
Powellminimize
n
yOuput
f.c.
Milestones
Software Baseline Design January, 2003
Software First Build July, 2004
Software Beta Release March, 2005
Software Release 1.0 February, 2006
End ARCS Project September, 2006
Software Development
Software Project Schedule
Data Reduction
• Account for incident flux• Remove background• Convert from time to energy• Correct for detector efficiency• Bin into rings of constant scattering angle• Convert from angle to momentum • Subtract multiphonon and multiple scattering• Correct for absorption
Suggestions for Planning a Sub-Project
1. Users Input (use telephone)
2. Use a Workshop to Prioritize Tasks
-- Cannot neglect standard approaches
-- Vision for new approaches is important and fun
3. Select P.I. (the workshop coordinator?)
4. Sub-Proposal in the next month or so…
End of Presentation
ARCS Hardware Project