/sup 6/LiI(Eu) in neutron and /spl gamma/-ray spectrometry-a highly sensitive thermal neutron detector

Europium doped ⁶LiI crystals (enriched to 96%⁶ Li) have been studied in neutron detection and gamma-ray spectrometry. Two crystals, 50 mmtimes5 mm and 30 mmtimes3 mm in size were coupled to a calibrated Photonis XP5200 photomultiplier, were tested. The response of ⁶LiI(Eu) to neutrons emitted from a paraffin moderated Pu-Be source has been investigated and the thermal neutron peak has been found at a Gamma Equivalent Energy (GEE) of about 3.5 MeV. The high sensitivity of the ⁶LiI(Eu) crystal is demonstrated by the observation of a neutron peak at a dose equivalent as low as 0.05 muSv/h. Apart from the neutron response, the light output, energy resolution and nonproportionality of the ⁶LiI(Eu) crystals versus gamma-ray energies have been measured. The light yield of 1.5times10⁴ ph/MeV (about 40% of NaI(Tl)) was obtained and the energy resolution at 662 keV (¹³⁷ Cs) of 7.5plusmn0.1% was found for the large crystal. The linearity of the light output with energy has been measured and is better compared to NaI(Tl). Due to the high sensitivity to thermal neutrons and good proportionality against gamma-ray energy, the ⁶ LiI(Eu) crystal was tested with a few samples of nuclear materials. Shielded samples can be recognized via detection of neutrons following spontaneous fission