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E. Blain et al.
2 Transmission Measurements
Some of the most common measurements performed at the RPI LINAC facility are
transmission measurements which are used to measure total cross section. These
measurements involve a detector located in the neutron beam which measures the
transmission through a sample material. The ratio of the counts with and without
the sample can be used to determine the total cross section of the sample material.
These measurements are particularly useful since the ratio method eliminates the
need to know the specific detector efficiency and neutron flux since they cancel out
in the calculation. There are several transmission detector setups which span a broad
energy range from thermal up to 20 MeV. The detectors in the thermal to keV region
all employ 6 Li glass. The thermal detector is located at a flight path of 15 m and has a
thickness of 3 mm which allows for excellent energy resolution while maintaining a
high counting rate. Two mid-energy transmission detectors are located at 31 and
100 m, respectively. These 0.5 in. detectors are used to accurately measure the
resonances to higher energy in an attempt to extend the resolved resonance region.
There is an additional EJ-301 detector array at 250 m that is used to measure total
cross section for the neutron energy range from 0.5 to 20 MeV.
Recent transmission results have been achieved for measurements of separated
isotopes of Mo. These measurements combined data taken with both the 31 m transmission detector and the 100 m transmission detector. These measurements resulted
in new measured resonances from all isotopes that could be used to extend the
resolved resonance region. Additionally, new fits were obtained for the unresolved
resonance region (URR). More detailed results for these Mo measurements can be
found in the following references [1, 2].
3 Capture Measurements
In combination with the transmission measurements, capture measurements are also
performed in order to provide a more complete set of experimental data to be
used in evaluations. By simultaneously measuring the capture and transmission the
resonance widths for the neutron and gamma can be fit together to allow for more
accurate resonance parameters. At RPI capture measurements can be performed
from thermal energies up to the low MeV region utilizing one of two capture
detection systems described in the following sections.
3.1 Low Energy Capture
For low energy capture measurements in the thermal to low keV region a capture
multiplicity detector is used. This is a 16-segment NaI(Th) detector which provides
E. Blain et al.
2 Transmission Measurements
Some of the most common measurements performed at the RPI LINAC facility are
transmission measurements which are used to measure total cross section. These
measurements involve a detector located in the neutron beam which measures the
transmission through a sample material. The ratio of the counts with and without
the sample can be used to determine the total cross section of the sample material.
These measurements are particularly useful since the ratio method eliminates the
need to know the specific detector efficiency and neutron flux since they cancel out
in the calculation. There are several transmission detector setups which span a broad
energy range from thermal up to 20 MeV. The detectors in the thermal to keV region
all employ 6 Li glass. The thermal detector is located at a flight path of 15 m and has a
thickness of 3 mm which allows for excellent energy resolution while maintaining a
high counting rate. Two mid-energy transmission detectors are located at 31 and
100 m, respectively. These 0.5 in. detectors are used to accurately measure the
resonances to higher energy in an attempt to extend the resolved resonance region.
There is an additional EJ-301 detector array at 250 m that is used to measure total
cross section for the neutron energy range from 0.5 to 20 MeV.
Recent transmission results have been achieved for measurements of separated
isotopes of Mo. These measurements combined data taken with both the 31 m transmission detector and the 100 m transmission detector. These measurements resulted
in new measured resonances from all isotopes that could be used to extend the
resolved resonance region. Additionally, new fits were obtained for the unresolved
resonance region (URR). More detailed results for these Mo measurements can be
found in the following references [1, 2].
3 Capture Measurements
In combination with the transmission measurements, capture measurements are also
performed in order to provide a more complete set of experimental data to be
used in evaluations. By simultaneously measuring the capture and transmission the
resonance widths for the neutron and gamma can be fit together to allow for more
accurate resonance parameters. At RPI capture measurements can be performed
from thermal energies up to the low MeV region utilizing one of two capture
detection systems described in the following sections.
3.1 Low Energy Capture
For low energy capture measurements in the thermal to low keV region a capture
multiplicity detector is used. This is a 16-segment NaI(Th) detector which provides