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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 [ABSTRACT FROM PUBLISHER]

The properties of CdWO4 (CWO) crystals in gamma spectrometry were studied. Several small samples of 10times10times3 mm size, typically used in CT X-ray detectors, were tested and then compared to the performance of a larger crystal of 20 mm in diameter and 20 mm in height. The light output, energy resolution, and nonproportionality of the CWO response versus gamma-ray energy, were measured and compared with those of a small BGO to discuss further the origin of the intrinsic resolution of pure undoped scintillating crystals. A high light output of 6500plusmn200 phe/MeV and a good energy resolution of 6.6plusmn0.2% for 662 keV gamma rays from a 137Cs source were measured for the small samples coupled to an XP3212 photomultiplier. Common nonproportionality curves and consequently common intrinsic resolutions of small CWO and BGO suggest that they represent fundamental characteristics of the heavy oxide scintillating material themselves [ABSTRACT FROM PUBLISHER]

The methodology recently developed by the Nuclear Metrology Laboratory (LMN) from IPEN, in Sao Paulo, Brazil, for simulating all detection processes in a 4pi(betaX)gamma coincidence system by means of the Monte Carlo technique is described. This procedure makes possible to predict the behavior of the observed activity as a function of the 4pibeta detector efficiency. The present paper describes its application to the standardization of a typical beta-gamma radionuclide, namely 134Cs. In this approach, information contained in the decay scheme is used for determining the contribution of all radiations emitted by the selected radionuclide to the measured spectra of each detector. This simulation yields the shape of the coincidence spectrum, allowing the choice of suitable gamma-ray energies for which the activity can be obtained with maximum accuracy. The theoretical work applies the MCNP Monte Carlo code to a gas-flow proportional counter with 4pi detection geometry, coupled to a pair of NaI(Tl) crystals. The calculated extrapolation curve showed good agreement when compared to experimental values obtained at the LMN of IPEN [ABSTRACT FROM PUBLISHER]