Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

Abstract

Abstract:The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. Here we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolved neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 µm pixel size of the detector used for this study, we found a resolution improvement from~80 µm to~22 µm using pixel centroiding while fully preserving the energy resolution.

Status Report on Development of a Cask to Enable Pulsed Neutron Characterization of Irradiated Fuel

“…This, in turn, enables utilizing the isotope specific imaging contrast of neutron absorption resonances to measure the spatial distribution of isotopes [20,21]. Neutron energies from cold to ~100 eV are suitable at LANSCE for energy-resolved neutron imaging with spatial resolutions up to 100 µm demonstrated for fuel applications (the pixel size of the detector is 55 µm and sub-pixel resolution using pixel-centroiding has been developed [33] but not yet applied to fuels).…”

New perspectives for neutron imaging through advanced event-mode data acquisition

“…Moreover, results were produced from post processed data only. While real-time single-event data-acquisition for neutron imaging was demonstrated on a Timepix quad detector combined with a neutron sensitive Microchannel-Plate (MCP) 10 with successful application to energy-resolved neutron imaging 11 , the detector system in these applications has a fixed FoV based on the active area of 28 × 28 mm 2 . For the work presented here, it was crucial to find a solution that would allow for a variable FoV as it is essential state-of-the-art in neutron imaging today.…”

“…In similar efforts at the China Spallation Neutron Source (CSNS), the ToA capability of the TPX3Cam was utilized to perform energy resolved neutron imaging at small FoVs of 5.4 × 5.4 mm 2 15 . The approach for neutron detection in that work is similar to that of the technique that was applied to the MCP detector 10 for energy-resolved neutron imaging 11 as discussed previously, in that a single CoM algorithm to events observed on the detector is described. However, the crucial difference between the two detector concepts is that for the MCP detector 10 the neutron capture produces a single electron avalanche (initiated by an alpha or 7 Li particle) in the borated MCP pores, providing a prompt cascade of electrons that is detected by the Timepix sensor.…”

Event-Mode Neutron Imaging Using the TPX3Cam - Breaking the Boundaries of Conventional Neutron Imaging Techniques

“…Moreover, results were produced from post processed data only. While real-time single-event dataacquisition for neutron imaging was demonstrated on a Timepix quad detector combined with a neutron sensitive Microchannel-Plate (MCP) [10] with successful application to energy-resolved neutron imaging [11], the detector system in these applications has a xed FoV based on the active area of 28×28mm 2 .…”