March 1999

User in mind

Thom Mason guides the ‘neutron end of the SNS machine’

Thom Mason
Thomas Mason
Many neutron sources were originally designed for some other purpose. The SNS is an opportunity to meet the specific needs of scientific users.
During his career, Thom Mason has used neutron sources for his studies of the magnetic properties of high-temperature superconductors and other materials. Now the SNS’s scientific director is trying to make sure that the needs of scientific users of the Spallation Neutron Source will be met.

The proposed SNS, which will produce the world’s most powerful pulsed beams of neutrons for research on materials, will provide opportunities for experiments to up to 2000 researchers a year from industry, universities, and other laboratories throughout the world. As the SNS project’s deputy project manager for neutron sciences, Mason is responsible for the R&D program for and design and construction of the SNS target and scientific instruments, or as he puts it, “the neutron end of the SNS machine.” He also represents the interests of the scientific community in ensuring that the overall project meets the requirements of the academic, industrial and government research community.

“Many neutron sources were originally designed for some other purpose such as radioisotope production, so the idea of doing neutron scattering research at these sources was an afterthought,” Mason says. “The SNS collaboration offers the opportunity to design a neutron source specifically optimized to meet the needs of the scientific users.”

That collaboration, seen as a key to realizing the project’s completion, includes with ORNL the Los Alamos, Argonne, Brookhaven and Lawrence Berkeley national laboratories.

The scientific instruments are being designed jointly by Argonne and ORNL, and many of the ORNL scientists involved will do the early development work at Argonne before returning to ORNL. Kent Crawford of Argonne is the senior team leader for instruments.

Concerning scientific instruments, Mason says his job involves being “a voice for the user community to make sure that decisions made during instrument design and construction have the user community in mind.”

He also provides a conduit for communication among members of the SNS collaboration and the scientific user community by organizing workshops. In November 1998, he co-chaired the SNS Instruments Workshop and the Oak Ridge Neutron Users Meeting at the Hyatt Regency Hotel in Knoxville, Tennessee.

The current plan is to design 10 instruments for 10 of the 18 neutron beam lines planned for one target station. Eight beam lines will be reserved for additional instruments, some of which will be used by collaborating research teams. A second target station may be added later if the completed facility is upgraded.

The instruments will count the neutrons and measure their energies and the angles at which they are scattered from a sample, which could be a novel plastic, a metallic alloy, or proteins. Neutron spectrometers will be built to measure interactions among atoms and molecules in the sample under changing conditions. Neutron diffractometers will be used to determine the arrangement of atoms and other structural characteristics in various materials.

Mason earned a bachelor of science degree in physics in 1986 from Dalhousie University in Halifax, Nova Scotia, and a doctorate in condensed matter physics in 1990 from McMaster University in Hamilton, Ontario. In 1990 and 1991, he conducted research as a postdoctoral fellow at AT&T Bell Laboratories in Murray Hill, N.J. From 1991 to 1993, he worked at Risø National Laboratory near Copenhagen, Denmark. From 1993 until May 1998 when he came to ORNL, Mason was a member of the faculty of the University of Toronto’s physics department.

He lives in Oak Ridge with his wife, Jennifer MacGillivray, and their two sons. When asked about the Tennessee climate, the Nova Scotia native remarks that “Toronto has had more than six feet of snow since Jan. 1 and I haven’t missed shovelling it.”—reported by Carolyn Krause