C.W.E. van Eijk

High-energy-resolution scintillator: Ce3+ activated LaBr3

The scintillation properties of LaCl3 doped with 10% Ce3+ are presented. Under optical and gamma ray excitation, Ce3+ emission is observed to peak at 330 and 352 nm. The scintillation light output is 46 000±1000 photons/MeV at 662 keV. Forty percent is emitted with a decay time of 26 ns, 30% with 210 ns, and 30% with about 1000 ns. An energy resolution (full width at half maximum over the peak position) of 3.3±0.3% was observed for the 662 keV full absorption peak.

Optical dating of young coastal dunes on a decadal time scale

We explore the use of quartz optically stimulated luminescence (OSL) dating for reconstructing coastal evolution on a time scale of decades to a few hundred years. Samples are taken from the accretionary south-west coast of Texel, a barrier island just offshore of the northern Netherlands. The ages of dune ridges are known from historical sources; an excellent chronology with a decadal accuracy exists for the past 260 years. OSL ages of less than 10 years on the youngest samples indicate that the OSL signal of the quartz grains is very well zeroed prior to deposition and burial. OSL ages of five samples from a 250-year-old dune ridge are indistinguishable, and the OSL ages on 17 out of 20 samples are in excellent agreement with the well-known independent age controls. Our results highlight the potential of OSL dating for high-resolution reconstruction of coastal evolution over the past few centuries.

Afterglow and thermoluminescence properties of Lu2SiO5:Ce scintillation crystals

The afterglow and thermoluminescence (TL) properties of several Ce3+ doped Lu2SiO5 crystals are reported. Both properties are caused by the presence of charge traps in the crystals. At least six different glow peaks are observed in the TL glow curve. Each is related to a specific charge trap. The parameters for these charge traps, such as the trap depth and the frequency factor, were obtained from first-order kinetics peak analysis of the TL glow curve. A charge trap with a depth of 1.0 eV is responsible for the afterglow observed at room temperature. Ce3+ ions appear to be the luminescence centres in the recombination process of the trapped charge carriers. It will be shown that optical excitation in the 5d levels of Ce3+ produces trap filling. The possible nature of the charge traps will be discussed.

Scintillation properties of Lu2Si2O7:Ce3+, a fast and efficient scintillator crystal

Cerium doped lutetium pyrosilicate Lu2Si2O7:Ce3+ (LPS), a new inorganic scintillator, displays particularly promising performance. This material can be readily pulled from the melt. A high light output (average value: 26 300 ph MeV−1), a relatively good energy resolution (9%) and a fast decay time (38 ns) without afterglow make this new scintillator very attractive, in particular for medical imaging. Optical characterizations and scintillation properties of LPS:Ce large single crystals are presented, including timing properties and study of the scintillation yields as a function of incident energy.

First direct observation of time-reversal non-invariance in the neutral-kaon system

Abstract We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of K 0 transforming into K0 and K0 into K 0 as a function of the neutral-kaon eigentime t. The comparison is based on the analysis of the neutral-kaon semileptonic decays recorded in the CPLEAR experiment. There, the strangeness of the neutral kaon at time t=0 was tagged by the kaon charge in the reaction p p → K ± π ∓ K 0 ( K 0 ) at rest, whereas the strangeness of the kaon at the decay time t=τ was tagged by the lepton charge in the final state. An average decay-rate asymmetry 〈 R( K 0 t=0 → e + π − ν t=τ )−R( K 0 t=0 → e − π + ν t=τ ) R( K 0 t=0 → e + π − ν t=τ )+R( K 0 t=0 → e − π + ν t=τ ) 〉=(6.6±1.3 stat ±1.0 syst )×10 −3 was measured over the interval 1 τ S τ S , thus leading to evidence for time-reversal non-invariance.

High efficiency of lutetium silicate scintillators, Ce-doped LPS, and LYSO crystals

We have introduced a new scintillator: cerium doped lutetium pyrosilicate Lu/sub 2/Si/sub 2/O/sub 7/ (Ce: LPS). A high light output (average value: 26,300 ph/MeV), a relatively good energy resolution (10%) and a fast decay time (38 ns) without afterglow make this new scintillator very attractive. We compare its properties to those of another recently developed cerium doped lutetium based silicate, Ce: Lu/sub 2(1-x)/Y/sub 2x/SiO/sub 5/ (LYSO).

Development and characterization of highly efficient new cerium doped rare earth halide scintillator materials

Inorganic scintillators for γ-ray detection are used in many fields from medical-diagnostic imaging to industrial measuring systems. Accordingly they face various demands with respect to e.g. response time, light yield, and energy resolution. The development of the new family of rare-earth halide scintillators LaCl3 ∶ Ce3+, LaBr3 ∶ Ce3+, and LuI3 ∶ Ce3+ is reviewed and their properties are compared to those of the established materials NaI ∶ Tl+ and Lu2SiO5 ∶ Ce3+. Extraordinary properties such as the short lifetime of 15 ns and the narrow energy resolution of 2.6% in LaBr3 ∶ 5% Ce3+, or the high light yield of 95000 photons per MeV in LuI3 ∶ 5% Ce3+ improve the performance of scintillators in existing applications and open the way to novel ones. The development of these new materials was empowered by the close interdisciplinary collaboration between scientists in the fields of inorganic chemistry, optical spectroscopy, and applied physics.

Ce3+ doped inorganic scintillators

Abstract There is a strong interest in the development of inorganic scintillators with a fast response for applications in high-energy physics, medical diagnostics and a number of other fields. One of the main lines of research concerns luminescence from the allowed 5d-4f transitions of lanthanide ions in appropriately chosen host lattices. Results are presented of research on Ce-doped scintillators.

Scintillation and spectroscopy of the pure and Ce3+-doped elpasolites: Cs2LiYX6 (X = Cl, Br)

The optical and scintillation properties of pure and Ce3+-doped Cs2LiYX6 (X = Cl, Br) are presented. X-ray-excited optical luminescence spectra, optical excitation and emission spectra, time-resolved excitation and emission spectra, scintillation pulse height spectra and scintillation decay time spectra of Ce3+-doped Cs2LiYX6 (X = Cl, Br) crystals measured from 10 to 300 K are presented. Factors influencing the scintillation mechanism and the presence of core?valence luminescence are discussed.

Gamma ray spectroscopy with a O19/spl times/19 mm/sup 3/ LaBr/sub 3/:0.5% Ce/sup 3+/ scintillator

Pulse height spectra of various sources covering X-ray and gamma ray energies from 10 keV to 6.1 MeV were measured by the first large O19/spl times/19 mm/sup 3/ LaBr/sub 3/:0.5% Ce/sup 3+/ scintillator. The spectra are compared with that recorded with a same sized NaI:Tl/sup +/ scintillator. Excellent energy resolution pulse height spectra are obtained showing that the scaling up from a small (/spl ap/3/spl times/3/spl times/10 mm/sup 3/) sized LaBr/sub 3/:Ce/sup 3+/ scintillator studied initially up to an /spl ap/6 cm/sup 3/ scintillator does not lead to much deterioration of resolution and light output. Special attention is devoted to the nonproportionality in the response of LaBr/sub 3/:Ce/sup 3+/ and related energy resolution. At high energy LaBr/sub 3/:Ce/sup 3+/ is far superior above NaI:Tl/sup +/ in terms of energy resolution and scintillation speed. At energies below 100 keV, NaI:Tl/sup +/ shows a better energy resolution.