Boron-rich benzene and pyrene derivatives for the detection of thermal neutrons

Abstract

A synthetic methodology is developed to generate boron rich aromatic small molecules based on benzene and pyrene moieties for the detection of thermal neutrons. The prepared aromatic compounds have a relatively high boron content up to 7.4 wt%, which is important for application in neutron detection as 10B (20% of natural abundance boron) has a large neutron induced reaction cross-section. This is demonstrated by preparing blends of the synthesized molecules with fluorescent dopants in poly(vinyltoluene) matrices resulting in comparable scintillation light output and neutron capture as state-of-the art commercial scintillators, but with the advantage of much lower cost. The boron-rich benzene and pyrene derivatives are prepared by Suzuki conditions using both microwave and traditional heating, affording yields of 40–93%. This new procedure is simple and straightforward, and has the potential to be scaled up.

Plastic scintillators modifications for a selective radiation detection

“…A very high density was observed (1.56), equal to the Pb-loaded plastic scintillator cited before. Light output was estimated to be close to 3,100 ph/MeV, with a decay time of 3.0 ns, and preliminary results for n/γ discrimination of a PuBe radioactive source were somehow modest but exist (Figure 12), as due to small dimensions of the sample, energy deposition of highly energetic electron from beta decay of 16 N and 19 O is weak.…”

“…Usually the carborane molecule is used as dopant in the plastic scintillator series, thanks to its extremely high content of boron inside the whole molecule. However, the use of pyrene modified with pinacolyl borate on four positions [16].The boron-rich pyrene (and benzene) derivatives are prepared by Suzuki conditions using both microwave and traditional heating, affording yields of 40-93%. Plastic scintillators with boron loading as high as 5 wt% are thus obtained.…”

“…So herein the large decay time difference between the two dyes is exploited, as the singlet fluorophore displays a 13 ns decay time and the triplet fluorophore a 370 µs decay time. A collaboration between Polish and French teams has led to a proof-of-concept of fast neutron/gamma discrimination using the energy threshold of the reactions n( 19 F, 16 N)α or n( 19 F, 19 O)H + for photofission prompt neutron detection [31]. Indeed, the energetic gap allows discriminating neutrons with E > 2.5 MeV with less energetic neutrons and gamma.…”

Neutron Response of the EJ-254 Boron-Loaded Plastic Scintillator

“…For slow neutrons (below approximately 1 keV), the number of photons produced by recoil protons becomes negligibly small. Neutron moderation via downscattering in the scintillating volume results in an increased probability of capture on 10 B: 10 B + n → 7 Li + 4 He Q = 2.792 MeV, 6% 7 Li + 4 He + γ(477.6 keV) Q = 2.310 MeV, 94%.…”

“…The 7 Li and 4 He nuclei produced in the reaction transfer energy to the system via Coulombic interactions, and the scintillation response is dominated by α excitation due to the ionization quenching effect. For neutrons with energies < 100 keV, the residual 7 Li nucleus is populated in its first excited state with a 94% branching ratio [21], which decays by prompt γ emission with E γ = 477.6 keV.…”