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HFBS: planning your measurement
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If you have an idea for a measurement, and want to discuss feasibility
and other practical matters, please contact one of the instrument
scientists. If this is the first time you will be doing an experiment
on HFBS, we strongly encourage you to discuss your plans with one of the local
contacts.
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Applying for beamtime (submitting requests and
proposals)
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To obtain beamtime on the HFBS,
you must submit either a request or a proposal, both of which can be
accessed by clicking here.
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Rough estimate of the time required for measurements
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The following information is presented so that prospective users can
get an idea how long their measurement may take.
A vanadium sample in the form of a hollow cylinder, a 10% scatterer,
was measured with a dynamic range of +/-27 µeV for 100 minutes.
The sample, which was mounted onto the closed cycle refrigerator
but measured at room temperature, was completely illuminated by the
neutron beam. Note that the beam size is 30 mm x 30 mm square.
The average total count rate in a detector was 108 counts/minute and the
signal to background ratio was 400:1. At the end of the 100 minute
count time, the intensity at the peak maximum was about 333 counts per
detector or about 5.5% relative error.
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It is important to note that a larger dynamic range will result in a
proportionately longer measuring time (to achieve the same counting
statistics, same energy bin size). For instance, you would have to
measure about 33% longer at the +/-36 µeV dynamic range to
get the same statistics as in the measurement discussed above.
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Information on
neutron scattering lengths and cross sections can be found here.
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