NOVA’s NeuView™ line of neutron-sensitive MCPs, integrated with suitable readouts, have long been used in a number of different neutron imaging and detection applications in both large and small neutron research facilities worldwide. For example, very important applications have already been demonstrated in areas such as radiographic and tomographic imaging, neutron time-of flight measurement, neutron diffraction, small angle reflectometry, and Bragg edge and resonance absorption.
Our neutron-sensitive MCPs have been used for a wide variety of purposes: composite material characterization, fuel assembly assessment, imaging of water migration through fuel cell membranes, strain mapping in metals, remote temperature mapping, and even dynamic magnetic field imaging inside solid objects.
Neutron Radiography and Tomography.
Neutron radiographic imaging is a very important application, as neutrons will react very differently than X-rays in penetrating through a sample. Neutrons interact strongly with the lightest elements in the periodic table (such as hydrogen-rich or ‘hydrogenous’ materials), whereas X-rays hardly interact with them at all. Thus neutrons are highly complementary to X-rays as probes of materials, and can reveal features and levels of contrast that X-rays are simply unable to resolve.
For example, the ND40 sealed image tube detector incorporating NOVA’s NeuView™ MCP and constructed and sealed by Proxivision in Germany, uses a single 40 mm active area neutron-sensitive MCP coupled with a fast phosphor screen. It effectively provides neutron images when samples or phantoms are placed in close proximity to the front neutron-transparent window. Depending on the level of beam dispersion (L/D) inherent in the neutron beamline, these detectors can provide spatial resolution levels down to ~50 µm.
Neutron tomographic imaging can provide 3-D views of complex structures, revealing fine details of the internal components of a sample. Typically, this 3-D image is built up from a series of separate 2-D neutron radiographs taken at incremental rotation angles. Final 3-D images are then reconstructed using special software. As an illustration of the power of this neutron imaging technique, using a ‘demountable’ or open-face detector, very impressive neutron tomographs of various objects have been made, using a NOVA NeuView™ MCP coupled to a Timepix CMOS-based electronic readout. Two examples are shown here:
A full tomographic reconstruction of a pocket watch can be found at the bottom of our Technology page.
Another way to utilize the NeuView™ MCP for radiography and tomography is to encapsulate it into a sealed image tube with a delay line anode readout (DLA), capacitively coupled through the ceramic backplane of the sealed tube (a schematic diagram is shown near the bottom of our Technology webpage). This arrangement was successfully demonstrated with a prototype ND40DL detection system, using NOVA’s NeuView™ MCPs and produced jointly with Proxivision (sealed image tube and system design) and Surface Concept (readout electronics), both based in Germany. This neutron imager made its successful debut on the CONRAD-2 imaging beamline of the Helmholtz-Zentrum Berlin (HZB).
Below are examples of the detector performance, with a Siemens star and pneumatic cylinder as the samples.
The full tomographic reconstruction done at HZB Berlin is shown in the video below:
Our neutron imagers could be employed as effective training tools for nuclear engineers and students interested in neutron detection and imaging, facilitating a fundamental understanding of neutron imaging. Moreover, it would be ideal for laboratory demonstrations. For example, students can set up small experimental tests and perform neutron radiography for a variety of applications using thermal or cold neutron beams in a research reactor. This might also be of particular interest to students from developing countries – where there may exist local and relatively modest neutron imaging facilities that could benefit from detector upgrades, and where there might be only limited travel funds to the few major neutron research facilities in the developed world. Furthermore, the latter often tend to be oversubscribed, with very tight constraints on available beam time for instruction.
Many nuclear engineering programs have ongoing research oriented towards measurements with neutrons. Some examples of university and national laboratory research with neutron radiography and scattering include:
- water transport across fuel cell membranes
- combustion nozzle spray analysis
- defects in silicon nitride ceramics
- imaging refrigeration components for behavior of lubricating oils
- detection of corrosion and entrapped moisture in structures
- plant transpiration
- studying debonding of carbon fiber composites
- measuring boron concentrations in shielding materials
- composite materials
- measuring effectiveness of moisture repelling agents in materials
- imaging shock waves in gases
- analysis of distribution of electro-transported hydrogen in palladium
- quantitative evaluation of nuclear fuel pin structural features
- imaging fluid spray patterns and dynamics
- imaging of wetting front instabilities in porous media
- boron neutron capture therapy (BNCT)
- and other applications