DIXIE: Web-Based Remote Control of a Medium Resolution Double-Crystal Small-Angle Spectrometer

J.A. Kohl, G.A. Geist II, P.H. Worley, M. Yethiraj
Oak Ridge National Laboratory, Computer Science and mathematics Division

This presentation describes the design of our web-based control interface for DIXIE, a medium resolution double-crystal small-angle spectrometer. DIXIE is one of twelve instruments available for neutron scattering studies at ORNL's High Flux Isotope Reactor.

The DIXIE web interface is the first of its kind for a neutron scattering instrument, and provides remote control, monitoring, and scientific collaboration features. Web-based access allows researchers to use the DIXIE facilities without wasting scarce time and resources for travel and lodging, and also avoids exposing researchers to low-level radiation. It is clear however that geographically-remote users still need to be able to converse and exchange ideas with the scientists who are responsible for the instrument. Our research with the DIXIE interface will help understand how to provide control and monitoring of instruments as well as how to effectively integrate collaborative tools such as electronic notebooks and video conferencing.

Users of the DIXIE interface can access the spectrometer by editing and submitting scan files for specific experiment runs, and then browsing the resulting data in either raw text format or using Java applets that plot the data. The scan files are created by the web interface in a well-defined format, allowing easy interfacing with the instrument and other tools. This scheme also provides an additional layer of security by separating instrument control from direct web access. The scan files are individually parsed and verified by a secure internal tool before actually being submitted to the spectrometer. An electronic notebook system has been integrated into the interface, to provide a persistent record of each experiment. Using this notebook, the results from all spectrometer scans, along with experimenter comments, can be captured into a secure archive. The electronic notebook for a given experiment is optional, and the notebook is automatically created at a user's request.

An authorized administrative user coordinates usage from the web by creating new experiments, assigning access to authorized users, and scheduling the running times for the various experiments. Users of DIXIE are authenticated before being granted entry into the interface, and once inside they can only manipulate (and see information concerning) experiments for which they have been given permission. A safety interrupt feature is also available from the web to request pausing or cancellation of the currently running experiment. Cameras in the instrument room can be remotely controlled from the Web interface, thereby providing a view of ongoing experiments without exposing the users to any radiation. These cameras can also be used for preliminary video conferencing activities with remote collaborators.

The DIXIE interface has been developed to run either as a CGI script or as a web server plug-in, and works on either a Unix or a Mac platform. In the future, the interface could be expanded to work with other instruments, and to incorporate various online data analysis features.

(posted 16-Oct-97 jw)