Neutron calibration facility with an Am-Be source for pulse shape discrimination measurement of CsI(Tl) crystals

Abstract

We constructed a neutron calibration facility based on a 300-mCi Am-Be source in conjunction with a search for weakly interacting massive particle candidates for dark matter. The facility is used to study the response of CsI(Tl) crystals to nuclear recoils induced by neutrons from the Am-Be source and comparing them with the response to electron recoils produced by Compton scattering of 662-keV γ-rays from a 137 Cs source. The measured results on pulse shape discrimination (PSD) between nuclear-and electron-recoil events are quantified in terms of quality factors. A comparison with our previous result from a neutron generator demonstrate the feasibility of performing calibrations of PSD measurements using neutrons from a Am-Be source.

Pulse-shape discrimination between electron and nuclear recoils in a NaI(Tl) crystal

“…Similar fits were performed for each 1 keV energy bin from 1 to 14 keV for nuclear and electron recoil events, and figure 3 shows the most probable value and the root mean square (RMS) of ln(MT) for electron and nuclear recoil data. As shown in the plots, the separation power is reduced at low energy, but some PSD capability persists at energies as low as 1 keV, which is even better than CsI(Tl) crystals [50,51].…”

“…This technique has been applied for WIMP searches with CsI(Tl) crystals [28,45,46] and NaI(Tl) crystals [47,48]. In the past, the discrimination power of NaI(Tl) crystals has been much poorer than that of CsI(Tl) crystals [49][50][51]. However recently developed NaI(Tl) crystals grown by Alpha Spectra Inc. provide higher light yields [42,44], and this makes it interesting to study their PSD performance and evaluate their sensitivity.…”

“…[51]. Neutron-induced signals in the neutron detectors are identified by taking advantage of the nuclear and electron recoil PSD capabilities of BC501A liquid scintillator [54,55].…”

Pulse Shape Discrimination of Nuclear Recoil and Electron Recoil Events With a NaI(Tl) Crystal for Dark Matter Search

“…For the neutron-nuclei elastic scattering measurements, we used the neutron calibration facility at Seoul National University [23] consisting of a 300-mCi Am/Be source surrounded by liquid scintillator (LSC), lead, and polyethylene shields. For the target, we used a small 2 cm × 2 cm × 1.5 cm NaI(Tl) crystal made from the same Alpha Spectra-grown ingot as a large crystal (NaI 002) used for background measurements in the Yangyang underground laboratory [15].…”

“…In the past, the discrimination power of NaI(Tl) crystals has been much worse than that of CsI(Tl) crystals [21]- [23]. However, recently developed NaI(Tl) crystal modules provide higher light yields, and that has resulted in much better discrimination power [24].…”