Determining the 6Li doped side of a glass scintillator for ultra cold neutrons

Abstract

Ultracold neutron (UCN) detectors using two visually very similar, to the microscopic level, pieces of optically contacted cerium doped lithium glasses have been proposed for high rate UCN experiments. The chief difference between the two glass scintillators is that one side is 6 Li depleted and the other side 6 Li doped. This note outlines a method to determine which side of the glass stack is doped with 6 Li using AmBe and 252 Cf neutron sources, and a Si surface barrier detector. The method sees an excess of events around the α and triton energies of neutron capture on 6 Li when the enriched side is facing the Si surface barrier detector.

Response of a Li-glass/multi-anode photomultiplier detector to collimated thermal-neutron beams

“…The cross section for the n (25 meV) + 6 Li → 3 H (2.73 MeV) + α (2.05 MeV) capture reaction is 940 b, which yields a detection e ciency of ∼75% for the 1 mm sheet. The average ranges of the 3 H and α-particle in the GS20 are 34.7 µm and 5.3 µm, respectively [46]. The 4.78 MeV capture reaction results in a ∼6600 scintillation photon full-deposition peak [21] (roughly equivalent to 20-30% of anthracene) peaked at ∼390 nm [47].…”

Response of a Li-glass/multi-anode photomultiplier detector to focused proton and deuteron beams

“…e capture process produces a 2.73 MeV 3 H (average range in GS20 of 34.7 µm) and a 2.05 MeV α-particle (average range in GS20 of 5.3 µm) [49]. e 6600 photon scintillation-light yield [9] corresponding to a thermal-neutron interaction (4.78 MeV) is quoted as 20-30% of anthracene and the emission spectrum peaks at 390 nm [50].…”

Response of a Li-glass/multi-anode photomultiplier detector to α-particles from 241Am

“…6 Li has a thermal-neutron capture cross section of ∼940 b at 25 meV, so that a 1 mm thick wafer of GS20 detects ∼75% of incident thermal neutrons. The process produces a 2.05 MeV α-particle and a 2.73 MeV triton which have mean ranges of 5.3 µm and 34.7 µm respectively [34] in GS20. Using the present αparticle source, scintillation light was generated overwhelmingly within ∼15 µm of the upstream face of the scintillating wafer.…”