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The ISIS
facility near Oxford, England is a spallation neutron source, based upon a linear particle
accelerator. Housed there is the
Thermal Original Spectrometer
with Cylindrical Analyzers (TOSCA),
see Figure 1. TOSCA is an indirect geometery, time-of-flight spectrometer.
TOSCA works in the following matter. The linear particle accelator collides highly energetic particles
with a heavy metal source creating a pulse of neutrons. The neutrons enter the beam tubes and the time
of departure is recorded.
The pulse of neutrons passes through a pair of choppers which select neutrons
of a specific velocity/energy. The monoenergetic pulse interacts with the sample and are scattered. The
scatter neutrons are filtered and counted by Helium-3 detectors. With each neutron counted the time of
arrival is also recorded.
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Figure 1: Schematic of the TOSCA spectrometer.
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Figure 2: Diagram of the path of a neutron.
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