Ponente
Descripción
Neutron imaging constitutes a valuable technique for the examination of the internal structures of high density and/or metallic materials [1]. As an emerging non-destructive testing (NDT) technique, it offers several advantages over conventional methods involving X-rays or ultrasounds. A significant part of the development of a neutron scanner for NDT is the design and proper characterisation of the detection system. In this work we present some recent, initial results on gamma- and neutron-based radiography and tomography using a simple and compact imaging system consisting of a scintillating sheet and a CMOS camera. The tests were carried out at a high activity 60Co irradiator at the Universidade de Santiago de Compostela, Spain, and at the HiSPANoS neutron beamline [2,3] at the Centro Nacional de Aceleradores (CNA) in Seville, Spain. The samples were mostly metal parts produced by additive manufacturing techniques. Internal and external structures were observed with a spatial resolution of about 1 – 3 mm. Further tests were performed at the CNA using a similar imaging system [4]. In the context of neutron imaging for industrial applications, the future DONES facility will provide unique opportunities for neutron imaging with both thermal and fast neutrons at its R160 irradiation area, which was identified of interest at the 2nd DONES Users Workshop. The high neutron flux and collimation capabilities of this facility will allow high-resolution neutron imaging at shorter exposure times and enable other techniques such as phase contrast imaging [5] or dynamic radiography [6]. In this way, the expertise obtained at the above facilities can be transferred to IFMIF-DONES.
We also propose the use of a self-built gaseous spectroscopic detector based on electroluminiscence detection for neutron spectroscopy. Bragg-edge transmission techniques provide information on both the material composition and microstructural characteristics of the sample, such as strains or inclusions, by analysing the Bragg edges in the neutron transmission spectrum [7]. The proposed dectector can provide time-resolved particle counting and, in addition to spectroscopic data, the spatial localisation of interactions. One of the most relevant features of the detector is its blindness to gamma radiation, which is typically the most intense source of background noise in charged particle and neutron detection. Such a detector could therefore complement imaging measurements in the context of neutron NDT. In this respect, the unique characteristics of the DONES facility would allow the evaluation of the detector performance at high fluxes of both thermal and fast neutrons.
References:
[1] INTERNATIONAL ATOMIC ENERGY AGENCY, Neutron Imaging: A Non-destructive Tool for Materials Testing, IAEA-TECDOC-1604 (2008).
[2] J. Gómez-Camacho et al., Research facilities and highlights at the Centro Nacional de Aceleradores (CNA), Eur. Phys. J. Plus 136 271 (2001).
[3] M.A. Millán-Callado et al., Continuous and pulsed fast neutron beams at the CNA HiSPANoS facility, Rad. Phys. Chem. 217 111464 (2024).
[4] M.A. Millán-Callado et al., Combining neutron/gamma radiography and tomography at CNA [Conference talk; available online], ND2022 (2022).
[5] M. Ostergaard et al., Polychromatic neutron phase-contrast imaging of weakily absorbing samples enabled by phase retrieval, J. Appl. Cryst. 56 673-682 (2023).
[6] C. Gruenzweig, Visualization of a fired two-stroke chain saw engine running at iddle speed by dynamic neutron radiography, SAE Technical Paper 2010-32-0013 (2010).
[7] K. Iwase et al., Bragg-edge transmission imaging of strain and microstructure using a pulsed neutron source, Nuc. Instr. Meth. Phys. Res. A 605 1-4 (2009).
