Speaker
Description
Direct measurements of astrophysical nuclear reactions require the detection of extremely low event rates and therefore benefit greatly from the ultra-low-background conditions available in deep underground laboratories. For neutron-producing reactions, sensitivity can be further limited by the lack of neutron-energy information provided by many conventional high-efficiency detectors, complicating the discrimination of signal neutrons from environmental or target-induced backgrounds. In the study of the 10B(a,n)13N using irradiation-resistant 10B enriched boron carbide (10B4C) targets, 13C within the target material introduces a competing, 13C(α,n)16O neutron source. Because traditional high-efficiency detectors such as 3He counters lack energy resolution [1], they cannot distinguish neutrons originating from a primary reaction from those produced by target contaminants or environmental backgrounds. This limitation necessitates the use of scintillator detectors with spectroscopic capabilities, which allow for the determination of neutron energies to confidently isolate the reaction of interest.
As part of the ERC NUCLEAR programme [2], we are investigating the 10B(a,n)13N reaction. Using EJ-301D deuterated liquid scintillators [3]. Unlike conventional proton-based scintillators, which yield a featureless recoil continuum, deuterated scintillators produce a characteristic, peaked pulse-height response due to neutron-deuteron scattering [4]. This distinct structure allows the incident neutron energy spectrum to be reliably reconstructed through spectrum unfolding, utilizing the detector response matrix and the Maximum Likelihood Error Minimization (MLEM) [5] approach. Crucially, this capability eliminates the need for Time-of-Flight (ToF) techniques, offering a significant advantage for continuous-beam experiments or compact laboratory setups where long flight paths are unfeasible.
This talk will present the first characterization of these deuterated scintillators in an underground setting. I will report on preliminary measurements conducted at the Laboratori Nazionali del Gran Sasso (LNGS) within the Laboratory for Underground Nuclear Astrophysics (LUNA) facility [6]. Finally, I will demonstrate the strategic advantages of using EJ-301D detectors to measure the 10B(a,n)13N reaction in the presence of events from natural/ambient background and/or target contaminants.
[1] Csedreki, L., Ciani, G. F., Balibrea-Correa, J., et al. (2021). Characterization of the LUNA neutron detector array for the measurement of the 13C(α, n)16O reaction. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 994, 165081. https://doi.org/10.1016/j.nima.2021.165081
[2] https://www.erc-nuclear.uk
[3] Becchetti, F. D., Raymond, R. S., Torres-Isea, R. O., Di Fulvio, A., Clarke, S. D., Pozzi, S. A., & Febbraro, M. (2016). Deuterated-xylene (xylene-d10; EJ301D): A new, improved deuterated liquid scintillator for neutron energy measurements without time-of-flight. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 820, 112–120. https://doi.org/10.1016/j.nima.2016.02.058
[4] Febbraro, M., Lawrence, C. C., Zhu, H., Pierson, B., Torres-Isea, R. O., Becchetti, F. D., Kolata, J. J., & Riggins, J. (2015). Deuterated scintillators and their application to neutron spectroscopy. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 784, 184–188. https://doi.org/10.1016/j.nima.2014.10.072
[5] Pehlivanovic, B., Avdic, S., Marinkovic, P., Pozzi, S. A., & Flaska, M. (2013). Comparison of unfolding approaches for monoenergetic and continuous fast-neutron energy spectra. Radiation Measurements, 49, 109–114. https://doi.org/10.1016/j.radmeas.2012.12.008
[6] https://luna.lngs.infn.it/index.php/new-about-us