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

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FACILITY DEVELOPMENT 2008 ANNUAL REPORT
Detector Systems
ORNL NEUTRON SCIENCES neutrons.ornl.gov
The Detector Group is responsible for
developing, assembling, calibrating,
installing, and commissioning neutron
detectors for the HFIR and SNS beam
lines. Detectors count the number of
incoming neutrons and, more important,
record the position and arrival
time (i.e., energy) of each neutron
seen by the detectors. Ongoing efforts
are under way to count neutrons
more efficiently, at higher
rates, and at finer spatial resolution
to increase the capacity and
resolution of all the neutron scattering
instruments. To assemble
and calibrate detectors, the group
maintains three detector laboratories,
two 35-microgram 252 Cf
neutron sources, three smaller
check sources, and the interim
HB-2DS Detector Test Station
at HFIR.
In 2008 we continued to support
the needs of operating
instruments and to calibrate
and install detector systems
on new instruments. A
major highlight of the year
was achieving 1-millimeter
resolution with the Anger
camera system. The detector
team focused on three
areas to reach this goal:
camera optics, enhanced calibration procedures, and
lower-noise packaging. The camera housing was integrated
with the electronics to reduce electronic noise
and to ensure that the cameras could be mounted in
spherical arrays.
Additional highlights were development of novel
8-pack packaging schemes and a new prototype for
reflectometers called an incline detector. A technology
transfer agreement for 8-pack production was
established with GE Reuter Stokes (see “Year in
Review”).
Support for Operational Instruments
Continuing work on operational instruments has led
to new developments and substantially improved
operations. Efforts focused on increasing reliability
and stability within all the detector systems, particularly
the larger ones (ARCS has more than 900
detectors). Improving communications within detector
arrays and fine tuning of power-up sequencing
have significantly enhanced performance for all the
operating instruments. At the beginning of the year,
approximately 15% of the detectors had communication
issues at any given time. By the end of the year,
however, all systems were operating dependably.
Development of a “flat field correction” resulted
in more uniform responses for some detectors. This
improvement will increase the dynamic range of the
experiments on the reflectometers and will improve
the position resolution of the detectors for SNAP.
Bruce Hannan, Detector Group, inspects an optical sensor from the scintillator
detector for VULCAN, an engineering materials diffractometer at SNS.