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

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FACILITY DEVELOPMENT 2008 ANNUAL REPORT
Sample Environment
ORNL NEUTRON SCIENCES neutrons.ornl.gov
The Sample Environment Group provides
users with equipment and support
for temperature, pressure, magnetic
field, and controlled-atmosphere environments
for experiments. Capabilities
have grown substantially during
the past year, making an increasing
range of environments available
to scientists at SNS and HFIR.
Several workhorse temperature
environments were commissioned
this year, including four liquid
helium cryostats and six closedcycle
refrigerator (CCR) systems.
Many of these systems have
undergone extensive in-house
customization to optimize their
performance. For example,
low-background, sample-invacuum
configurations have
been implemented on the
SNS ARCS, SEQUOIA, and
CNCS spectrometers. “Hot
exchange gas” CCRs have
been developed to cover a
wide temperature range
(7 to 500 kelvin) while
ensuring minimal temperature
gradient along the
sample. And specialized
sample sticks have been designed with features such
as sample rotation and gas loading.
In addition, the world’s first self-shielded magnet for
neutron scattering, a 5-Tesla vertical field system,
was commissioned at SNS in May (see “Year in
Review”), and a much stronger 16-Tesla system is
scheduled for delivery in the summer. The magnetic
field profile of these new shielded systems not only
eliminates interference but also enhances the ability
to use polarized neutron beam techniques. Meanwhile,
older magnet systems are being updated and
recommissioned. A 4.5-Tesla horizontal field magnet
has been upgraded and dedicated to the HFIR
GP-SANS instrument, and two vertical field magnets
(5 and 6 Tesla) continue to serve as mainstays at
HFIR.
We now have a substantial inventory of pressuregenerating
devices that includes large inert gas rigs
(10 kilobars) and compact trolleys for liquids and
gases ranging from 0.2 to 7 kilobars. Aluminum
gas pressure cells rated to 4 kilobars have been
purchased, and cells of various materials are under
development through collaborative research and
development. These include a single-crystal sapphire
cell that is well suited for measurements on the
SNS Backscattering Spectrometer and a titanium
zirconium “null scattering” alloy cell for diffraction
studies. Anvil pressure cells and related items have
Matthew Collins, Sample Environment Group, operates the
crane in the SNS Target Building, lowering a sample environment
to its needed beam line.