Neutron Imaging at LANSCE—From Cold to Ultrafast

Abstract

(Lujan center), Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutrons and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR) facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns), time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.

On a Method For Reconstructing Computed Tomography Datasets from an Unstable Source

“…This data was collected over a period of several days in December of 2018, in 3 segments (due to the part height and limited beam profile). The panel used was a Perkin-Elmer 1621 panel, with a pixel pitch of 200 microns, with an attached 2.5 mm thick PP + ZnS:Cu scintillator from RC Tritec (for additional details, refer to [ 8 ]). The scintillator was thick, a design choice made to improve detection efficiency, but at the expense of spatial resolution.…”

“…The neutron source was approximately 21 m from the part, and the panel was approximately 10 cm behind the part. The neutron beam was effectively collimated to 3 cm in the vertical direction and 7 cm in the horizontal direction, resulting in an ratio of approximately 700 vertical and 300 horizontal [ 8 ]. Thus, we are able to use a parallel beam approximation in the reconstruction.…”

“…In 1972, the first commercial CT machine was developed by Sir Godfrey Hounsfield [ 4 ], and in the decades that followed, applications of computed tomography using X-rays have been the subject of intense study, both in the medical and industrial fields. In parallel, neutron radiography was developed in the 1930s [ 5 , 6 ] and has been used to successfully produce images of reasonable quality in the subsequent decades [ 7 , 8 ]. Additionally, parametric studies to understand image formation in neutron radiography have been performed (for fast neutrons, for example, see [ 9 ]).…”

Short-Pulse Laser-Driven Moderated Neutron Source

“…For some applications, such as epithermal energy-resolved neutron imaging, allowing to measure isotope densities [10], the resolution available with a shorter flight path is acceptable. The concurrent flux increase from the 1/L 2 ratio of the LANSCE FP5/ERNI beamline [29], where these experiments are presently conducted at around 10 m sample to detector distance, would therefore enable some applications at neutron count times similar to what is required at LANSCE.…”

Wavelength-resolved Neutron Tomography for Crystalline Materials

“…Neutron imaging is a powerful tool for characterizing engineering materials because they can penetrate thick specimens and provide a complimentary contrast to X-rays [1,2]. Driven by the recent advent of spallation (pulsed) neutron sources and the availability of time-of-flight imaging detectors [3], there has been an emergence of wavelengthresolved (WR)/time-of-flight (ToF) neutron imaging instruments [4][5][6][7]. While WR imaging instruments have been used for tomographic characterization of amorphous samples (for example [8]), using them to image samples with single-crystal This manuscript has been authored by UT-Battelle, LLC, under Contract No.…”