Jun 13 – 17, 2022
Berkeley, CA
US/Pacific timezone

New Advances in C$^7$LYC

Not scheduled
Berkeley, CA

Berkeley, CA

Lawrence Berkeley National Laboratory
Oral Poster Presentations Poster Session


P. Chowdhury (University of Massachusetts Lowell)


We report on new advances in simulation, characterization and fabrication of the $^7$Li-enriched dual neutron-gamma scintillator C$^7$LYC. Detailed GEANT4 simulations have been performed, with specific focus on (n,p) and (n,$\alpha$) reactions on $^{35}$Cl that are primarily responsible for the fast neutron response of C$^7$LYC. The simulations are compared to experimental data to separate contributions of the different reaction channels. In addition, new C$^7$LYC crystals with square cross-sections have been fabricated for exploring compact close-packed geometries.

To identify features of the different neutron reaction channels, the neutron and $\gamma$ response for 1" x 1" and 3" x 3" C$^7$LYC detectors of cylindrical cross-section were simulated in GEANT4 choosing physics models in the code for high precision neutron transport below 20 MeV. The scintillation light output for a 1" x 1" C$^7$LYC was simulated using Birk's equation [1], with Birk's constant for C$^7$LYC deduced from experiment. This allowed a comparison of the quenching of the scintillation light output for protons and $\alpha$ particles. The GEANT4 simulations were compared with initial MCNP results for consistency and subsequently benchmarked against experimental inelastic neutron scattering data from a $^{12}$C target.

The experimental data were obtained at the Los Alamos LANSCE facility using a white neutron beam generated by bombarding a thick W spallation target with 800 MeV pulsed protons. An array of 1"x1" C$^7$LYC detectors was placed radially ~20 cm from a $^{12}$C scatterer. Incident neutron energies were extracted by measuring their arrival time across a ~20-m flight path from the spallation target to the $^{12}$C, and then to the detectors, with appropriate recoil corrections for the different detector angles. The scattered neutron energies were measured as pulse heights in the C$^7$LYC detectors, which reflects the inherent spectroscopic resolution of the scintillator, and allows a mapping of the energy-dependent response of C$^7$LYC to mono-energetic neutrons. Prominent features of the experimental spectra are reproduced remarkably well in the simulations with the primary $^{35}$Cl(n,p) and $^{35}$Cl(n,$\alpha$) reactions, and help identify the features where the data overlap from the different neutron reaction channels. In addition, resonances in the $^{35}$Cl(n, p) cross-section as a function of incident neutron energy below 3 MeV, recently measured through the detection of the outgoing proton [2], were directly observed in C$^7$LYC with similar resolution.

To assess the efficacy of C$^7$LYC as a viable scintillator for close-packed geometries, four 1" x 1" x 3" C$^7$LYC crystals, with square cross-sections, square photo-tubes and minimal surrounding material, have been acquired. Both efficiency and cross-talk of fast neutrons are being investigated, and initial results will be presented.

The work is supported by the U.S. Department of Energy.

[1] J.B. Birks, The Theory and Practice of Scintillation Counting (Pergamon, New York, 1964).
[2] S.A. Kuvin et al, Phys. Rev. C102, 024623 (2020).

Primary authors

S. Saha (University of Massachusetts Lowell) P. Chowdhury (University of Massachusetts Lowell) M. Devlin (Los Alamos National Laboratory) A.M. Rogers (University of Massachsuetts Lowell) P.C. Bender (University of Massachusetts Lowell) T. Brown (University of Massachusetts Lowell) E. Doucet (University of Massachusetts Lowell) N. D'Olympia (University of Massachusetts Lowell) N. Fotiades (Los Alamos National Laboratory) J.A. Gomez (Los Alamos National Laboratory) C.J. Lister (University of Massachusetts Lowell) C. Morse (University of Massachusetts Lowell) G.L. Wilson (University of Massachusetts Lowell)

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