SCANS: Software for computer aided neutron scattering

• Research unit: EU RFP
• Project number: 00.0208

Key words (English)

Monte Carlo simulation; neutron scattering instruments; instrument design

Alternative project number (English)

EU project number: HPRI-1999-50013

Research programs (English)

EU-programme: 5. Frame Research Programme - 4.1.1 Research training networks

Short description (English)

See abstract

Further information (English)

Full name of research-institution/enterprise:
Paul Scherrer Institut PSI / ETH Zürich
Labor für Neutronenstreuung

Partners and International Organizations (English)

Uppsala University, Uppsala (S), Risø National Laboratory, Roskilde (DK), Technische Universiteit Delft (NL), CLRC, RAL, Didcot (UK), Hahn-Meitner-Institut GmbH, Berlin (D), Res. Inst. for Solid State Physics and Optics, Budapest (HU), Nuclear Physics Institute, Rez - Praha (CZ), Istituto Nazionale per la Fisica della Materia, Genova (I)

Abstract (English)

The main objective of the SCANS project is the development of software that enables more efficient and effective use of European neutron scattering facilities, either in terms of instrument design or experiment design and execution. Priority will be given to the development and extension of the existing Monte Carlo simulation packages for neutron scattering instruments, MCSTAS and VITESS.
A common data format is essential for exchanging and comparing the results. For this purpose an international team of scientists and computer programmers from neutron and X-ray facilities has developed the NeXus data format. The main part of the Swiss participation in SCANS will be the further development of the NeXus software as well as providing documentation and help for adding this standard into the simulation packages.
After intense discussions on a combined NeXus/SCANS workshop in march 2001 at PSI, Villigen, the NeXus API was extended to support flushing and unlimited dimensions. This was done for the ANSI-C, F77 and F90 API. A Java-API for NeXus was designed and implemented using the Java native methods interface. Working groups were established for the refinement of the NeXus dictionary for instrument definitions.
NeXus is based on HDF version 4 as the physical file format. The implementors of HDF, NCSA, now promote a new, incompatible, version of HDF, HDF5. HDF5 supports file sizes larger then 2GB and lifts HDF-4's limit on the number of objects possible in a file. Therefore it became necessary to provide a NeXus-API for HDF5 as well. For the implementation of this new API we strived to achieve two main goals: The first is maximum compatibility at the API level in order to minimize changes to existing code. The second goal was support for both HDF-4 and HDF5. The new API is available since June 2001 and can be built to support HDF-4 or HDF5 only or to support both HDF-4 and HDF5. The goal of maximum API compatibility was achieved with the exception of compressed data set writing. A new API function became necessary for the creation of compressed datasets due to limitations in the HDF5 API. In the meantime the new API is not only supported for the C programming language but also for Fortran 77 and Java. Both NXdict and NXbrowse have also been adapted to work with the new API version. Some initial work has been done in order to add NeXus support into the Monte Carlo simulation package Vitess. Work is in progress on a new tutorial for NeXus.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 00.0208