Prompt gamma NAA
Macroscopic boron analysis in various samples is carried out at the
prompt gamma neutron activation analysis (PGNAA) facility. A beam
of thermal neutrons is extracted from beneath the MITR-II core and filtered
by single crystal sapphire ingots. The filtered beam is then diffracted
by a set of specially aligned graphite crystals that are designed to focus
thermal neutrons at the sample position. The activation photons
that result from thermal neutron capture in the sample are collected by
a nearby high purity germanium (HPGe) photon spectrometer and analyzed
to determine the boron content of the sample.
The shielding surrounding
the detector and sample is specially designed to reduce the background
arising from unwanted activation and improve the sensitivity to emissions
from the sample. The high sensitivity achieved with this facility
allows for small samples (0.5 ml) containing only 10 ug/g of 10
B to be measured in three minutes or less. Samples can be analyzed
directly without preparation. The PGNAA technique is non-destructive,
so samples can be preserved after analysis for future measurement.
Several other elements besides boron can be analyzed via PGNAA with varying
sensitivities, including gadolinium, cadmium, samarium, chlorine and indium.
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