Characterization of two extraordinary AmLi neutron sources

First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment

“…The tritium source is important for understanding the response to low energy ER events, the most prominent background component in the run. Localized NR calibration events are created using a deuterium-deuterium (DD) generator that emits monoenergetic 2.45 MeV neutrons [39][40][41] along a conduit through the water tank and AmLi sources [42] deployed between the walls of the cryostat vessels.…”

Design and characterization of AmLi neutron sources for the LZ experiment

“…Table 4 shows the yields of all three AmLi sources. They are found to be somewhat lower than 1.5•10 −6 n/𝛼, reported in [6,32]. The chosen sandwich geometry of our sources probably contributes here.…”

“…The LZ data acquisition system (DAQ) [5], which is designed with the goal of saving maximal information for each triggered event, cannot handle high event rates exceeding approximately 1000 events/s. Furthermore, since the commercial vendors often use the same facility to build different (𝛼, n) sources, impurities might be included [6]. Hence, three sources were built at the University of Alabama (UA) as per LZ requirements.…”

“…High energy gamma search Previous publications on AmLi sources [6] identified unwanted high-energy events, created by contamination of the source with beryllium, resulting in secondary nuclear reactions. A dedicated GeIII detector run with reduced amplifier gain was performed to search for the 4.439 MeV 𝛾-radiation emitted in the de-excitation of 12 C after the reaction 9 Be(𝛼, n) 12 C * .…”

“…As in the case of the AmBe source, the spectrum of the neutrons emitted by the AmLi sources is not known. Plausible AmLi energy spectra were taken from the literature [6,27] or derived from the GEANT4 package SaG4n [28,29]. However, SaG4n does not allow the implementation of complex geometries; hence neutron transport through the source encapsulations for the various spectra was performed in G 4 with the "ShieldingLEND" physics list.…”