Screen shot of the SliceView prototype.
Introduction
The SANS group at the University of Tennessee is part of the NSF funded DANSE project to develop software to enable new science to be extracted from neutron scattering experiments. The goal of our group is to provide new advanced data analysis tools to the SAS user community.The DANSE/SANS group is committed to involving the community as early as possible in the software engineering process, by taking a stepwise approach, with frequent releases, and soliciting feedback along the way. Below you will find analysis areas we are interested in and applications we hope to provide. If you have ideas, requests, please feel free to contact us. Contribution are also welcome.
The path forward
Our group plans to provide analysis functionality through three applications. Those applications will be incrementally developed throughout the life of the project. The computational functionality will be developed first. Once sufficient computational functionality exists, prototype applications, implementing that functionality, will be developed and distributed in order to gather feedback and refine the requirements. Finally, the first limited versions of the applications will be delivered, and again refined based on feedback. The following is a list of the main areas of development:- Basic modeling
Provide basic 1D and 2D models for SANS. Models for specific systems (like rods, spheres, core-shell cylinder) will be made available, in addition to system-independent models for standard fitting (like Guinier fitting).Status: Complete - A large variety of model independent, 1D and 2D models are available.
- Simulation of real-space systems
Provide functionality to simulate systems made of basic shapes arranged in real-space. The scattering intensity will be calculated for those systems, both for oriented systems (2D scattering intensity) and rotationally averaged systems (1D scattering intensity).Status: Basic 1D simulation available. 2D simulation started but on hold.
- Interface with community software
IGOR is one of the primary platforms for U.S. SAS community data analysis. DANSE will provide an interface to IGOR to facilitate the integration and use of the analysis functionality we are developing. This will allow early access to DANSE code while applications are being developed. Additionally, code sharing with the NIST IGOR analysis software will be developed and the international canSAS standard format effort will be supported.Status: 2D modeling is available as a prototype XOPS; C level code sharing between NIST IGOR and SANS/DANSE; HFIR reader for NIST IGOR to complement ANSTO, ILL, and HANARO readers made available; support for canSAS 1D standard format as well as most 1D ASCII formats.
- Inversion to P(r)
Provide functionality to invert 1D data to pair density distribution function P(r).Status: Complete
- Ab initio/shape reconstruction modeling
Status: cancelled. Not deemed of sufficiently high priority at this time. This may be picked up once the software transitions to its long term maintenance and development mode.
- Experimental planning and optimization
Status: Begun, but further development halted. Not deemed of sufficiently high priority to warrant compexity at this time. This may be picked up once the software transitions to its long term maintenance and development mode.
- Interface to MC simulation
- Series analysis and simultaneous fitting
- Constrained fitting
Status: Cancelled. Other parallel efforts such as SASSIE seem to be more appropriate for this task.
Status: Complete
Status: Complete. Using interface to PARK, another DANSE product
As the computational functionality becomes available, we will provide prototype applications for our users to try out. Those prototypes will enable us to gather requirements from the community and better plan for our releases. The following is a list of the applications we expect to provide:
- Prototype: Simulation of real-space systems
This prototype was made available to a selected community of testers in mid-2007 to investigate the construction of real-space systems from basic shapes. The user interface is built around an empty 3D canvas on which users can place objects. P(r) and I(q) are then simulated for the systems represented on the canvas.This prototype has served its requirement gathering purpose and was retired during the summer of 2007. A new version called SimView has been available since March 2008.
Status: released
- Prototype: 2D modeling [SliceView]
SliceView is a prototype that allows users to compare oriented models to NIST-compatible data. Users can select slices of the 2D image and compare them to data. Polydispersity and averaging over angular distributions is also available.Status: released
- Prototype: model-independent fitting
This prototype will allow users to fit 1D scattering intensity distributions to system-independent models. The most common are Guinier analysis, Porod analysis and power-law fits. This prototype will correspond to a new major release of SliceView.Status: released
- Prototype: Experiment planning tools
Status: On hold
- Application: Model fitting analysis
The SansView application will allow the user to calculate the 1D and 2D scattering patterns for rotationally averaged, partially, or fully oriented systems, using analytical functions for various shapes. Optimization against 1D or 2D reduced data will include standard parameter optimizations as well as constrained optimizations on the models. the application will also include simple linear analysis, peak shape analysis, correlation length analysis, etc. Batch mode operation and parametric analysis will also be included.Status: released v. 2.0. This application has become the single flagship application produced by the project and incorporates all the mature features including P(r)
- Application: Model-independent real-space analysis
This application will allow the calculation of the pair density distribution function [P(r)] or the so called "ab-initio" or "shape reconstruction" from 1D reduced SANS data. Additionally, it will allow for the construction and maniputlation of 3D real space objects, including loading of PDB files, and invert to produce corresponding scattering patterns. Patterns can then be compared to 1D or 2D reduced SANS data and optimized against some real space parameters.Status: Cancelled for now. P(r) funtionality incorporated into SansView application. "ab-intio" is not deemed a current high priority and proper real space simulation may be more appropriate to other projects such as SASSIE
- Application: Experiment planning tools
Given source and instrument parameters, this application will allow simulation of the raw data collected as a function of experimental parameters (e.g. time, sample thickness, and size) including some system dependent background such as incoherent scattering from the sample. This will make use of the models developed for the previous applications and convolute them with the instrument specific parameters (e.g. beam flux).Status: On hold due to the computational portion being on hold
