Enhancement Effect of Fused Double Benzene-Ring Structure on the Light Output of Carborane-Loaded Toluene- and Pseudocumene-Based Scintillators

• Published in: IEEE transactions on nuclear science 2016-06, Vol.63 (3), p.1750-1761
• Main Authors: Chang, Zheng, Okoye, Nkemakonam C., Urffer, Matthew J., Miller, Laurence F.
• Format: Article
• Language: English
• Subjects: Birks factor; carborane-loaded organic scintillator; Chemicals; Energy exchange; light output; neutron detection; Neutrons; Periodic structures; Photonics; scintillation efficiency; Solvents
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2016.2547840

Four sample groups were prepared by adding different concentrations of naphthalene (NP) or of 2,6-diisopropylnaphthalene (DIN) as a secondary solvent ({{\rm S}_2}) in carborane-loaded toluene (TL)- and pseudocumene (PC)-based scintillators. The pulse-height spectra of the samples in response to ^{137}{\rm Cs}\ \gamma -rays and to thermal neutrons were collected to study the light output (L) enhancement effect of {{\rm S}_2}. It is found that for all sample groups, L increases to a plateau with the concentration of secondary solvent ([{{\rm S}_2}]). As [{{\rm S}_2}] is increased from 0 to saturation concentration, L increases by 31-45% and 34-53% in response to ^{137}{\rm Cs}\ \gamma -rays and to thermal neurons, respectively. A first-order approximation model is proposed to fit to the experimental data. The enhancement factor ({k_h}) and maximum L of each sample group are obtained from curve fitting. The Birks factor ( kB ) and electron equivalent energy ( keVee ) of each sample are calculated by a numerical method based on Birks formula. The L enhancement is discussed according to the percent changes of these parameters. In conclusion, the enhancement effect is attributed mainly to the fused double benzene-ring structure of NP and DIN, which has more delocalized electrons, and provides faster Förster resonance energy transfer paths than the single benzene-ring structure of TL and PC. Adding NP or DIN leads to a significant increase in absolute scintillation efficiency (S) and a slight decrease in kB for both scintillators. It is believed that DIN has