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