NDT
HYDROGEN HELP
Aluminum is very transparent to neutrons
and for purer materials, when they have a very
small percentage of other elements to give
improved properties, x-rays are a more effective
method for analyzing a material. “For pure
aluminium, there’s not much of an advantage
compared to x-rays. If you have a pure material, then
often x-ray is better suited,” says Mannes. The difficulty
neutrons have with such materials is that for them the
space between atoms is vast. Most neutrons will pass
through those spaces without interacting with nuclei.
The easier materials to image have a lot of hydrogen
within them. This light element has small atomic nuclei
that are packed much closer together, atom-to-atom, and
this hydrogen lattice, which can be found for example in
water, means the neutron is more likely to interact with
nuclei. As water has the hydrogen that helps neutron
imaging, corrosion studies are an area of work for the
neutron imaging. Rittenhouse says, “We definitely have
seen some interesting applications for corrosion. But for
things like munitions, it’s not necessarily just water,
there’s a lot of hydrogen-rich materials in there.”
60 MARCH 2020 \\ AEROSPACETESTINGINTERNATIONAL.COM
COMPACT NEUTRON GENERATOR TECHNOLOGY
Developed with the support of the US Army and aerospace companies,
Phoenix’s neutron generator technology uses deuterium-deuterium
(DD) and deuterium-tritium (DT) nuclear fusion reactions to generate a
stable and high neutron flux.
Phoenix says its fusion-based neutron generators can produce a yield
of tens of trillions of neutrons per second for industrial applications,
such as radiation effects testing, neutron imaging, nuclear fuel assay,
ion implantation, medical isotope production, and more.
The company’s neutron imaging system uses compact electricallydriven
particle accelerators to drive an ion beam into custom targets to
generate neutrons for the purpose of neutron imaging. The company’s
Alectryon neutron generator has a gaseous deuterium or tritium target
for high neutron yields and can be configured to support neutron
imaging. The company’s Thunderbird system offers a high neutron
yield using deuterium-deuterium reactions, but does not produce
enough neutrons for imaging applications. It is suitable for applications
such as mobile IED detection and neutron activation analysis.
All of Phoenix’s neutron generation systems can be installed on-site
anywhere in the world and on the factory floor for high volume
product makers.
TECHNOLOGICAL INNOVATION
With a growing variety of applications and greater
demand for existing applications, more investment is
being made into improving neutron radiography,
particularly around digital imagery. “There’s lots of R&D
going on to improve neutron imaging,” says
MacGillivray. “At some point, we’re not going to have
film available to do this kind of work and we’re going to
need to be doing it digitally.”
One aspect of this transition to digital is having
agreed standards on image quality. Digital alternatives
use charge-coupled device (CCD) detectors. “We’ve got a
way to go around the standards to measure the image
quality and to be able to get a resolution comparable to
film,” MacGillivray says.
Mannes says, “There’s a lot of national laboratories
and universities playing around with various aspects of
this technology. A lot of it is on the detector side.”
At the Oak Ridge National Laboratory (ORNL) in
California one goal for neutron imaging development is
to use neutrons to create highly detailed 360˚ internal
images of parts. Oak Ridge researcher Hassina Bilheux is
an instrument researcher in the neutron imaging facility.
Her team uses a microchannel boron plate detector as
3 // The Spallation Neutron
Source at the Oak Ridge
National Laboratory
contains more than 1000
control points
(Photo: ORNL)
4 // Phoenix’s neutron
generators can produce a
high neutron flux and also
have a high neutron yield
(Photo: Phoenix)
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