| The Multi-Axis Crystal
Spectromenter takes advantage of the large solid angle view of the cold
source to deliver a high intensity neutron beam at sample position. The
large doubly focusing PG monochromator can deliver up to 5x108 neutrons/cm2/s
in a 2 cm x 4 cm area at sample position, providing one of the highest
neutron beam in the world. Between the monochromator and the
sample there is a focusing super-mirror guide that enhances the flux on
sample by approximately 20%. Upstream of the monochromator there is a
variable beam aperture that controls the overall angular distribution of
neutrons that is incident on the sample. There are also radial
collimators that control the energy resolution. It is a remarkable
aspect of MACS that the Q and E resolution can be controlled virtually
independently through these remote controlled devices. The detection
system for MACS consists of twenty independent monochromatic channels
with variable final energy. There is also an energy integrating detector
in each channel. These channels operate simultaneously and in doing so
provide 0.15 Sr monochromatic detection plus 0.15 Sr diffraction
detection. This is more than an order of magnitude gain in detection
efficiency for surveys as compared to a conventional TAS. |
Actual MACS configuration: Incident energy: 2.3 to
17 mev
Energy resolution: 0.02 to 1.4 meV (FWHM)
Monochromator: Doubly focusing PG002
Analyzer: 20 analyzers vertically focusing PG(002)
providing 0.15 Sr of detection. Fixed Be filters and 90' collimators
before the analyzers.
Detector: 40 He detectors (20 spectroscopic and 20
diffraction detectors)
Flux at sample: 5x108
neutrons/cm2-s at 12meV
open collimators
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