Neutron Sciences 2008 Annual Report - 17.79 MB - Spallation ...

56
FACILITY DEVELOPMENT 2008 ANNUAL REPORT
Instruments
Spallation Neutron Source
Four new instruments were completed in 2008 and
are now being commissioned: SNAP, CNCS, SE-
QUOIA, and FNPB. The new instruments are performing
well and are expected to continue to expand
in reliability and capability. Some initial experiments
have been performed during commissioning.
ORNL NEUTRON SCIENCES neutrons.ornl.gov
SNS instrument development and construction
continues at a fast pace, and progress is on schedule
for five more instruments to be completed and begin
commissioning during 2009:
› EQ-SANS: Extended Q-Range Small-Angle
Neutron Scattering Diffractometer, beam line 6
› POWGEN: Powder Diffractometer,
beam line 11A
› VULCAN: Engineering Materials
Diffractometer, beam line 7
Valeria Lauter, SNS Magnetism
Reflectometer.
› TOPAZ: Single-Crystal Diffractometer,
beam line 12
› NSE: Neutron Spin Echo Spectrometer,
beam line 15
Two “SNS Instruments—Next Generation” (SING)
projects will add seven more instruments to the SNS
lineup between 2010 and 2014. SING I—a suite of
five instruments—is more than 50% complete. The
construction, commissioning, and schedule for the
current SNS instrument suite is shown in the “Facts
and Figures” section.
A World’s First: Magnetism Reflectometer Fitted With Helium
Neutron Analyzer with Online Pump-Up Polarization
In July 2008, the experimental team of Hal Lee, Andre Parizzi, Richard Goyette,
Hailemariam Ambaye, Lee Robertson, and Valeria Lauter successfully
installed the world’s first 3 He (helium isotope) neutron analyzer with on-line
pump-up polarization. Neutrons have magnetic spin, and a device of this
type allows researchers to detect the intensities and orientations of the individual
spins (up or down) of scattered neutrons (i.e., polarization). “The
data on the polarization of scattered neutrons provide unique information
about the nature of magnetic interactions within a sample,” said Valeria
Lauter, lead instrument scientist for the Magnetism Reflectometer at SNS.
The best way to detect the neutrons’ polarization after they have scattered from the sample is to again
scatter them from another magnetically polarized substance. For this device, 3 He was used in the analyzer cell, which
was constructed at the National Institute of Standards and Technology. During testing, the ORNL team was able to achieve an
impressive 76% polarization (i.e., 76% of the 3 He atoms inside the analyzer were polarized one way—spin up or spin down). A trial study
carried out with an iron-chromium multilayer demonstrated that the new analyzer performed well. “With future improvements and modifications, we
anticipate that we will be able to carry out important studies of the magnetic properties of new nanoscale materials,” Lauter said.