C.W.E. van Eijk

Bio: C.W.E. van Eijk is an academic researcher from Delft University of Technology. The author has contributed to research in topics: Scintillation & Luminescence. The author has an hindex of 50, co-authored 392 publications receiving 10483 citations. Previous affiliations of C.W.E. van Eijk include University of Coimbra.

High-energy-resolution scintillator: Ce3+ activated LaBr3

Abstract: The scintillation properties of LaBr3 doped with 0.5% Ce3+ are presented. Under optical and gamma ray excitation, Ce3+ emission is observed to peak at 356 and 387 nm. The scintillation light output is 61 000±5000 photons/MeV at 662 keV. More than 90% is emitted with a decay time of 35 ns. An energy resolution (full width at half maximum over the peak position) of 2.85%±0.05% was observed for the 662 keV full absorption peak. A time resolution of 385 ps was obtained using BaF2 as second scintillator and gamma rays of 60Co.

Non-proportionality in the scintillation response and the energy resolution obtainable with scintillation crystals

Abstract: A review and new data are presented on the absolute photon yield emitted by "classical" (NaI(Tl/sup +/), CsI(Tl/sup +/), CsI(Na/sup +/), CaF/sub 2/(Eu/sup 2+/), Bi/sub 4/Ge/sub 3/O/sub 12/, and CdWO/sub 4/) and "modern" (BaF/sub 2/, Gd/sub 2/SiO/sub 5/(Ce/sup 3+/), YAlO/sub 3/(Ce/sup 3+/), Lu/sub 2/SiO/sub 5/(Ce/sup 3+/), Lu/sub 3/Al/sub 5/O/sub 12/(Sc/sup 3+/), and K/sub 2/LaCl/sub 5/(Ce/sup 3+/)) scintillation crystals after absorption of X-rays and /spl gamma/-rays of energies ranging from 5 keV to 1 MeV. Factors influencing the energy resolution with which high energy photons can be detected with scintillator-photomultiplier combinations are reviewed. Attention is especially focused on the effects of nonproportionality in the scintillation response on the energy resolution.

Scintillation properties of LaBr3:Ce3+ crystals: fast, efficient and high-energy-resolution scintillators

Abstract: The scintillation properties of LaBr 3 doped with different Ce concentrations, studied by means of optical, X-ray, and γ-ray excitation are presented. Under optical and γ-ray excitation, Ce 3+ emission is observed peaking at 356 and 387 nm. For pure LaBr 3 and LaBr 3 doped with 0.5%, 2%, 4% and 10% Ce 3+ we measured a light yield of 17,000±2000, 61,000±5000, 48,000±5000, 48,000±5000 and 45,000±5000 photons per MeV (ph/MeV) of absorbed γ-ray energy, respectively. The scintillation decay curve of LaBr 3 :Ce 3+ can be described by a single exponential decay function with a decay time of 30±5 ns. It represents over 90% of the total light yield. An energy resolution (FWHM over peak position) for the 662 keV full energy peak of, respectively, 2.9±0.1%, 3.8±0.4%, 3.5±0.4% and 3.9±0.4% was observed for LaBr 3 :0.5%, 2%, 4% and 10% Ce 3+ .

Phosphors in phosphor-converted white light-emitting diodes: Recent advances in materials, techniques and properties

Abstract: Phosphor-converted white light-emitting diodes (pc-WLEDs) are emerging as an indispensable solid-state light source for the next generation lighting industry and display systems due to their unique properties including but not limited to energy savings, environment-friendliness, small volume, and long persistence. Until now, major challenges in pc-WLEDs have been to achieve high luminous efficacy, high chromatic stability, brilliant color-rending properties, and price competitiveness against fluorescent lamps, which rely critically on the phosphor properties. A comprehensive understanding of the nature and limitations of phosphors and the factors dominating the general trends in pc-WLEDs is of fundamental importance for advancing technological applications. This report aims to provide the most recent advances in the synthesis and application of phosphors for pc-WLEDs with emphasis specifically on: (a) principles to tune the excitation and emission spectra of phosphors: prediction according to crystal field theory, and structural chemistry characteristics (e.g. covalence of chemical bonds, electronegativity, and polarization effects of element); (b) pc-WLEDs with phosphors excited by blue-LED chips: phosphor characteristics, structure, and activated ions (i.e. Ce 3+ and Eu 2+ ), including YAG:Ce, other garnets, non-garnets, sulfides, and (oxy)nitrides; (c) pc-WLEDs with phosphors excited by near ultraviolet LED chips: single-phased white-emitting phosphors (e.g. Eu 2+ –Mn 2+ activated phosphors), red-green-blue phosphors, energy transfer, and mechanisms involved; and (d) new clues for designing novel high-performance phosphors for pc-WLEDs based on available LED chips. Emphasis shall also be placed on the relationships among crystal structure, luminescence properties, and device performances. In addition, applications, challenges and future advances of pc-WLEDs will be discussed.

Tests of quantum gravity from observations of γ-ray bursts

Abstract: The recent confirmation that at least some γ-ray bursts originate at cosmological distances1,2,3,4 suggests that the radiation from them could be used to probe some of the fundamental laws of physics. Here we show that γ-ray bursts will be sensitive to an energy dispersion predicted by some approaches to quantum gravity. Many of the bursts have structure on relatively rapid timescales5, which means that in principle it is possible to look for energy-dependent dispersion of the radiation, manifested in the arrival times of the photons, if several different energy bands are observed simultaneously. A simple estimate indicates that, because of their high energies and distant origin, observations of these bursts should be sensitive to a dispersion scale that is comparable to the Planck energy scale (∼1019 GeV), which is sufficient to test theories of quantum gravity. Such observations are already possible using existing γ-ray burst detectors.