Qualification and development of fast neutron imaging scintillator screens

Fast Neutron Imaging with Semiconductor Nanocrystal Scintillators

“…The kinetic energy of these recoil nuclei is then deposited as ionized charge carriers in the detector material, which can excite a scintillator to emit visible range photons detectable by conventional imaging devices such as a CCD camera. 12 The energy transfer efficiency for elastic collisions is highest for two bodies of equal mass, thus the proton in a hydrogen atom is the best nucleus for fast neutron scattering. In conjunction with the relatively high interaction cross section of a proton with fast neutrons (Figure 1b), hydrogen-rich materials have been widely used in fast neutron detectors.…”

“…24−26 The latter type has shown the most success to date, 12,27 with screens consisting of ZnS:Cu in a PP matrix, denoted hereafter as ZnS:Cu(PP), showing a good combination of light output and spatial resolution that has led to their commercialization by RC Tritec AG. 12,28 However, long exposure times are still required to obtain high-quality images even under high fast neutron fluxes, while spatial resolution decreases substantially with thickness of the scintillator plate, 28 likely due to light scattering at the phosphor−plastic interface, as the typical size of phosphor inclusions are larger than the emission wavelength. Another fundamental drawback is the afterglow of the ZnS:Cu phosphor, which exhibits a several minute decay under fast neutron beam exposure, 28 problematic for the short repeated exposures required for computed tomography and precluding the use of such screens in pulsed neutron experiments with high repetition rates.…”

Highly Concentrated, Zwitterionic Ligand-Capped Mn2+:CsPb(BrxCl1–x)3 Nanocrystals as Bright Scintillators for Fast Neutron Imaging

“… 1 , 13 − 15 Traditionally, the community has utilized standard phosphors as the indirect detectors for recoil protons generated by scattering of fast neutrons. 10 , 11 , 16 …”

Fast Neutron Imaging with Semiconductor Nanocrystal Scintillators

“…Fast neutron imaging is a complementary technique that enables investigation of largerscale samples of dense, mixed-Z compositions, for which imaging with X-rays, γ-rays, or even thermal neutrons would not provide sufficient penetration. 12 Fast neutron imaging widens the scope of potential imaging applications to include cargo contraband detection or imaging of large archeological specimens or irradiated nuclear fuel. 13−16 However, this technique has thus far been underutilized due to the limited number of fast neutron sources, and more critically the significant challenge of efficiently detecting fast neutrons.…”

“…Consequently, there are two common types of fast neutron imaging detectors: an integrated liquid or plastic scintillator which provides both high proton density and light emission, 7,20−23 or a two-part detector consisting of a hydrogen-dense matrix (often a plastic or polymer such as polypropylene (PP) or high-density polyethylene) and a scintillator material such as ZnS:Ag, ZnS:Cu, or Gd 2 O 2 S:Tb. 24−26 The latter type has shown the most success to date, 12,27 with screens consisting of ZnS:Cu in a PP matrix, denoted hereafter as ZnS:Cu(PP), showing a good combination of light output and spatial resolution that has led to their commercialization by RC Tritec AG. 12,28 However, long exposure times are still required to obtain high-quality images even under high fast neutron fluxes, while spatial resolution decreases substantially with thickness of the scintillator plate, 28 likely due to light scattering at the phosphor−plastic interface, as the typical size of phosphor inclusions are larger than the emission wavelength.…”