Neutron radiography, or N-ray, is a powerful nondestructive testing method due to the unique properties of neutrons. While the mechanics are similar, N-ray provides a new perspective compared to X-ray due to the different penetration depth of each type of radiation for different materials. While neutron radiography has been underutilized for non-destructive testing and materials research applications due to a lack of access to a powerful enough neutron source, Phoenix’s high flux neutron generators are changing the landscape.

See what new perspectives neutron radiography can offer you:

Aircraft Turbine Blades X-Ray/Neutron Image Comparison

X-ray image
Neutron image

The manufacturing of jet engine turbine blades is one particular industrial niche for neutron radiography. Turbine blades are cast around ceramic molds which form cooling channels that prevent the blades from melting when exposed to the high temperatures of their operating environments. In manufacturing, fragments of ceramic can clog these cooling channels. A blade with clogged cooling channels could break or even melt while in operation, so such flaws must be rooted out with 100% certainty. The X-ray image (left) cannot clearly depict the cooling channels in a batch of blades; however, the channels show up much clearer in a neutron image of the same batch (right).

This cross section of a turbine blade shows off one of the most useful and unique applications of industrial neutron radiography. The only way to reliably detect the ceramic fragments which can be left within a blade’s cooling channels is to wash the blade in a solution containing gadolinium, an element with a high neutron cross section. Once the gadolinium has permeated the ceramic’s porous structure, the fragments will show up in stark contrast on the resulting neutron image even after the solution has been rinsed off of the rest of the blade.

Beretta 92FS Neutron/X-Ray Image Comparison

440kV X-ray imaging
Neutron imaging

Neutron radiography is especially useful for imaging munitions. In this neutron image, neutrons interact with parts within the firearm and show details that a high-energy x-ray would not depict, even the presence and position of gunpowder in the cartridge.

Rotary Telephone X-Ray/Neutron Image Comparison

170kV X-ray imaging
440kV X-ray imaging
Neutron imaging

X-rays and neutrons interact with materials differently, creating unique images. This rotary phone is comprised of many dense and light materials. The lower-energy 170 kV X-ray beam could not penetrate the denser materials of the phone. The higher-energy 440 kV X-ray beam could penetrate the denser materials, but was too high-energy to create an image of the lighter materials. The neutron beam could penetrate dense materials but not light materials, creating an image that shows more detail of the phone’s inner workings than either X-ray image could on its own. This is what makes neutron radiography such a powerful complementary tool to X-ray radiography in materials science, materials research. and non-destructive testing applications.

Flower Neutron Images

Flowers tend to show up very distinctly on both neutron images and X-ray images. However, water has a very high neutron scattering cross section, which makes neutron radiography and tomography useful for studying water uptake within root systems and rooted soil.

Hand Plane X-Ray/Neutron Image Comparison

60kV X-ray imaging
140kV X-ray imaging
200kV X-ray imaging
Neutron imaging

With examples such as this hand plane, it’s “plane” to see how neutron images can show you details that can’t be seen with X-ray radiography. These three X-ray radiographs of varying energies, looked at as a whole, all together show almost as many details as a single neutron picture!

Welding Flux X-Ray/Neutron Image Comparison

Welding flux on a copper plate (photo)
Welding flux on a copper plate (X-ray)
Welding flux on a copper plate (neutron image)

Like gadolinium, boron has an extremely large neutron cross section that makes it useful as a contrast agent in neutron imaging, among other things. In this example, welding flux, which contains large quantities of borax, attenuates neutrons particularly well compared to metals such as copper. This makes neutron imaging useful for assessing the quality of welds and making certain that undesirable remnants of flux do not remain on a welded part.

Fuel Injector X-Ray/Neutron Imaging Comparison

100kV X-ray image
190kV X-ray image
Neutron image

As with the images of the rotary phone, these fuel injectors depict the differences between high and low energy X-ray images as well as neutron imaging. The image taken with 100 kV X-rays misses important details regarding the fuel injectors’ structures because the X-rays cannot easily penetrate the dense outer layers of material. However, the image taken with 190 kV X-rays also misses important details because while the X-rays can pass more easily through the denser material, they also pass too easily through the lighter material as well. Neutron imaging, on the other hand, offers more detail than either of the X-ray radiography images on their own.

In particular, two of the fuel injectors have been clogged with condiments, which show up as white blockages in the plugs in the N-ray image and do not show up at all in the X-ray images. This shows the value of neutron radiography in rooting out defective parts and other non-destructive testing applications!

Interactive N-Ray/X-Ray Comparison

100kV X-Ray Image: Fuel Injectors Neutron Image: Fuel Injectors
190kV X-Ray Image: Fuel Injectors Neutron Image: Fuel Injectors

Click and drag on the vertical line to compare X-ray radiography and neutron radiography images. One advantage neutron imaging offers over the X-ray images is that details that did not show up on either the high-energy or low-energy X-rays, such as blockages within the fuel injectors, are visible.

Proxivision Ball Bearings X-Ray/Neutron Imaging Comparison

225kV X-ray image
400kV X-ray image
Neutron image

Interactive N-Ray/X-Ray Comparison

225kV X-Ray Image: Ball Bearings Neutron Image: Ball Bearings

Click and drag on the vertical line to compare X-ray and N-ray images.

Hard Disk Drives

Because of the way neutrons pass easily through denser metals, the neutron image of the 3.5″ hard disk drive on the left mainly shows the less dense plastic components of the hard drive’s internals. the 2.5″ external hard drive on the right is entirely encased in a plastic shell which is more opaque, but not entirely opaque, to neutrons.

Interactive N-Ray/X-Ray Comparison

X-Ray Image: Hard Drive Neutron Image: Hard Drive

Click and drag on the vertical line to compare X-ray and N-ray imaging. To neutrons, most of the metal parts of the hard disk drive, such as the faceplate, the read/write heads, and the disks themselves, are completely transparent, allowing a clearer look at some components that are not as visible, if at all, in the X-ray image.

Bats

We’re batty for neutron radiography at Phoenix! Unlike X-rays, neutrons are attenuated heavily by flesh and muscle, giving a unique perspective to the radiographic image of these bat specimens. That is one of several reasons why your dentist probably isn’t interested in shooting neutron radiation at your teeth during your dental check-up.

Consumer Electronics

Neutron radiography can provide an interesting look into consumer electronics. As in the hard drive images, the plastic tends to be more opaque to neutrons in the neutron beam than most of the electronic components, providing a unique view of the structures of these items.

Personal Safe X-Ray/Neutron Imaging Comparison

Photograph
X-ray image
Neutron image

Your secrets aren’t safe from X-ray vision or neutron vision, but both forms of radiography show quite different perspectives in these images. Plastic components, which are rich in hydrogen, are particularly opaque on the neutron images but much more transparent on the X-ray images due to the high neutron attenuation of plastics and other hydrogen compounds. A closeup of the Honeywell safe shows that neutron imaging could even pick up on the details of the embossed logo on the door to the safe!

Flashlight X-Ray/Neutron Imaging Comparison

Neutron image
X-ray image

Both neutron radiography and X-ray radiography can offer distinct advantages over each other. In these images, both depict unique features of the flashlight in question. Phoenix is currently working on a method to seamlessly combine the data from X-ray and neutron imaging together into hybrid images, which would allow for an unparalleled look into an object’s inner working for cases in which both X-ray radiography and neutron radiography provide indispensable data.

Jar of Staples

X-Ray Image: Jar of Staples with Toy Neutron Image: Jar of Staples with Toy

Click and drag on the vertical line to compare X-ray and neutron imaging. For a rather offbeat comparison of the strengths and weaknesses of X-ray and neutron imaging, we filled a glass jar with staples and a single plastic figurine. In the X-ray image, only the staples are visible. With neutron imaging, the staples are far less visible, but the figurine hidden within is entirely visible as the neutrons interact more heavily with the plastic.

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