Showing papers by "C.W.E. van Eijk published in 1998"
University of Fribourg1, CERN2, University of Ljubljana3, Boston University4, University of Liverpool5, University of the Mediterranean6, Delft University of Technology7, Royal Institute of Technology8, Paul Scherrer Institute9, University of Ioannina10, DSM11, Aristotle University of Thessaloniki12, University of Coimbra13, Centre national de la recherche scientifique14
TL;DR: The first observation of time-reversal symmetry violation through a comparison of the probabilities of K 0 transforming into K0 and K 0 into K 0 as a function of the neutral-kaon eigentime t was reported in this article.
190 citations
National and Kapodistrian University of Athens1, University of the Mediterranean2, Paul Scherrer Institute3, University of Liverpool4, University of Fribourg5, CERN6, Royal Institute of Technology7, DSM8, Boston University9, Aristotle University of Thessaloniki10, University of Coimbra11, University of Ljubljana12, Delft University of Technology13, University of Ioannina14, Centre national de la recherche scientifique15
TL;DR: In this paper, the EPR-type strangeness correlation in the K0 K 0 system produced in the reaction p p → K 0 K 0 at rest has been tested using the CPLEAR detector.
85 citations
TL;DR: In this article, a reabsorption process is shown to take place in this material, which is responsible for the observed decrease of the light yield when increasing the size of the sample.
Abstract: The system has been shown to be a promising scintillator for medical imaging devices. Recently, efforts were focused on the improvement of its scintillating properties. Several large crystals with various cerium concentrations were grown. Absorption and excitation spectra were measured in a range extending from the visible to the vacuum ultraviolet (VUV). Emission spectra, fluorescence decay times and light yields, both under -ray and x-ray excitation, were measured under various experimental conditions. A reabsorption process is shown to take place in this material. This process is responsible for the observed decrease of the light yield when increasing the size of the sample.
79 citations
TL;DR: In this article, a new measurement of the K L − K S mass difference Δm using the CPLEAR full data sample of neutral-kaon decays to e πν.
40 citations
01 Feb 1998-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, Lu2S3:Ce3+ crystals with corundum structure have been studied and the linear attenuation length of a 511 keV photon is 1.35 cm.
Abstract: Scintillation properties of Lu2S3:Ce3+ crystals are presented. The studied crystals of ∼1 × 1 × 1 mm3 have the corundum structure (density 6.25 g/cm3, effective atomic number 66.8). The linear attenuation length of a 511 keV photon is 1.35 cm. The light yield is 25 000–30 000 photons per MeV and the decay time is rather short, i.e. 32 ns. The emission spectrum is between 550 and 700 nm, peaking at 592 nm. Consequently the scintillation light can be efficiently detected by means of silicon diodes.
39 citations
21 Nov 1998-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, a new method to discriminate thermal neutrons against γ-rays using a radiation damaged LiBaF3, Rb scintillation crystal is presented, which is based on the SCINTillation pulse shape.
Abstract: A new method to discriminate thermal neutrons against γ-rays using a radiation damaged LiBaF3 : Ce, Rb scintillation crystal is presented. Discrimination is based on the scintillation pulse shape which for thermal neutrons is very different than that for γ-rays because different scintillation mechanisms are involved. Efficient suppression of γ-rays with an energy from a few keV to a few MeV is possible.
37 citations
University of Coimbra1, CERN2, University of Ljubljana3, Boston University4, University of Liverpool5, University of the Mediterranean6, Delft University of Technology7, Royal Institute of Technology8, Paul Scherrer Institute9, University of Ioannina10, DSM11, Aristotle University of Thessaloniki12, University of Fribourg13, Centre national de la recherche scientifique14
TL;DR: In this paper, the CPLEAR experiment measured the eigentime-dependent asymmetry in the rates of initially tagged K 0 and K 0 decaying to π 0 π ε 0 ε ε −5 in order to study the interference between the CP-violating K S and the CPconserving K L decay amplitudes.
18 citations
TL;DR: In this paper, a core-valence luminescence was studied in Rb1~ x Cs x Cl ( x "0.02") crystals using X-ray and VUV synchrotron excitation in the temperature range from 7 to 300K.
14 citations
Proceedings Article•
01 Jan 1998TL;DR: In this paper, the 3x3 arrays include N++NP diodes, processed in the -12 pm thick membranes that remain after thinning of 530 pm thick (100) silicon wafers by means of a potassium hydroxide (KOH) solution.
Abstract: In developing position sensitive radiation sensors, e.g. for medical imaging, low-gain silicon well sensors were made for the detection of scintillation light. The 3x3 arrays include N++NP diodes, processed in the -12 pm thick membranes that remain after thinning of 530 pm thick (100) silicon wafers by means of a potassium hydroxide (KOH) solution. A comparison is made for the light detection efficiency of these diodes with that of a 500 pm thick PIN photodiode. E p substrate
11 citations
01 Jan 1998
TL;DR: In this paper, the 3/spl times/3 arrays include N/sup ++/NP diodes, processed in the /spl sim/12 /spl mu/m thick membranes that remain after thinning of 530 /spl polysilicon wafers by means of a potassium hydroxide (KOH) solution.
Abstract: In developing position sensitive radiation sensors, e.g. for medical imaging, low-gain silicon well sensors were made for the detection of scintillation light. The 3/spl times/3 arrays include N/sup ++/NP diodes, processed in the /spl sim/12 /spl mu/m thick membranes that remain after thinning of 530 /spl mu/m thick [100] silicon wafers by means of a potassium hydroxide (KOH) solution. A comparison is made for the light detection efficiency of these diodes with that of a 500 /spl mu/m thick PIN photodiode.
10 citations
21 May 1998-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the authors present results of a study of the gas gain and the maximum anode-cathode potential for anode widths running from 4 to 15 μ m and SiO2 strip widths between 6 and 30 μ m.
Abstract: The microgap couter (MGC) is a promising development in the field of small gas-filled position sensitive detectors. In the MGC the anode strips are carried by small insulating ridges of SiO2 or polyimide, that are mounted on top of the cathode strips. The exact widths of the anode and the insulator strips can play an important role in the maximum attainable gas gain. We present results of a study of the gas gain and the maximum anode–cathode potential for anode widths running from 4 to 15 μ m and SiO2 strip widths between 6 and 30 μ m. For the realisation of these micro-structures in standard IC technology, we use a wafer stepper machine with a step size of 1×1 cm 2 . Despite this surface limitation, we have managed to enlarge the MGC to an active area of 5×5 cm 2 . Details about this project will be highlighted.
TL;DR: In this paper, the role of the Eu 2+ ions to the trapping process and possible models to explain the observed thermoluminescence was discussed. But, the authors did not consider the effect of UV photons.
National and Kapodistrian University of Athens1, University of the Mediterranean2, Paul Scherrer Institute3, University of Liverpool4, University of Fribourg5, CERN6, Royal Institute of Technology7, University of Coimbra8, Aristotle University of Thessaloniki9, DSM10, Boston University11, University of Ioannina12, University of Ljubljana13, Delft University of Technology14, Centre national de la recherche scientifique15
TL;DR: In this paper, the CP violation parameter is determined through the eigentime-dependent asymmetry in the rates of initially tagged kzerob and kzero decaying to pizero \pizero.
TL;DR: In this paper, the core-valence luminescence (CVL) caused by radiative recombination of electrons from the 3pCl valence band and 5pCs core holes was investigated.
11 Jun 1998-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: A LaF 3 :Nd(10%) scintillator crystal has been placed in a microgap gas chamber to obtain a position-sensitive detector for γ-rays as discussed by the authors.
Abstract: A LaF 3 :Nd(10%) scintillator crystal has been placed in a microgap gas chamber to obtain a position-sensitive detector for γ-rays. Directly on the crystal a thin layer of nickel is evaporated and on top of that a thin semi-transparant CsI photocathode. γ-rays absorbed in the scintillator crystal produce a UV-light flash, which liberates electrons in the photocathode. These electrons are multiplied and detected in the microgap chamber. By comparing the spectrum measured when this detector is irradiated with 511 keV γ-rays with a spectrum that is computed in a Monte Carlo simulation it is concluded, that the probability that a UV-light photon created in the scintillator produces a photoelectron in the photocathode, is about 2.5%. The signals from this detector can be distinguished better from the background than when a similar crystal is mounted on a standard photomultiplier tube.
TL;DR: A review of recent developments in instrumentation for detection of radiation is presented in this paper, focusing on new inorganic scintillators for gamma ray and thermal neutron detection, light sensors, and silicon sensors for detecting X rays and low energy gamma rays.
Abstract: A review is presented of some recent developments in instrumentation for detection of radiation. The focus is on new inorganic scintillators for gamma ray and thermal neutron detection, light sensors, and silicon sensors for detection of X rays and low energy gamma rays. Both non-position-sensitive and position-sensitive detectors are discussed.
National and Kapodistrian University of Athens1, University of the Mediterranean2, Paul Scherrer Institute3, University of Liverpool4, University of Fribourg5, CERN6, Royal Institute of Technology7, University of Coimbra8, Aristotle University of Thessaloniki9, DSM10, Boston University11, University of Ioannina12, University of Ljubljana13, Delft University of Technology14, Centre national de la recherche scientifique15
TL;DR: In this paper, ππ correlations in the exclusive reaction pp → 2π+2π− at rest measured by the CPLEAR experiment were studied. And the physical implications of bosonic symmetrization for the properties of the pion source, in particular its radius, are briefly discussed.
Abstract: We study ππ correlations in the exclusive reaction pp → 2π+2π− at rest measured by the CPLEAR experiment. Avoiding the introduction of an arbitrary reference sample, we analyse differential distributions for equal charge pion pairs removing the phase-space factor event by event. A peak at small relative momenta is most pronounced for large total momentum of the pair. The physical implications of bosonic symmetrization for the properties of the pion source, in particular its radius, are briefly discussed. The two extremes considered are the chaotic Hanbury-Brown-Twiss mechanism and the coherent Skyrmion model.
21 Dec 1998-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the authors present data on the variation of the positive ion collection by the drift electrode versus drift field at several pressures up to 6 bar using a Kr-CO 2 mixture and the influence of the drift field in the pulse rise time is also considered.
Abstract: One of the main drawbacks of the use of microgap structures when used at high pressure (6 bar) at high count rates (∼10 6 s −1 mm −2 ) is the limited maximum safe gain at which they can be operated. The use of a preamplification device such as the GEM (gas electron multiplier) can overcome this limitation; however, secondary space charge effects due to charge accumulation at the non-metallic surfaces cannot be neglected and should be minimised. These positive charges are due to the intrinsic multiplication of the GEM device and also to the drift of ions from the anode of the main detector. In this study we present data on the variation of the positive ion collection by the drift electrode versus drift field at several pressures up to 6 bar using a Kr–CO 2 mixture. Data were collected with microgaps having several anode and insulator widths. The influence of the drift field in the pulse rise time is also considered.
08 Nov 1998
TL;DR: Simulation of a saw tooth configuration with p/ sub x/=250 /spl mu/m, p/sub y/=200 /splMu/M, and /spl alpha/=60/spl deg/ showed that potential gutters with a depth of 80 mV will be produced assuming a drift field of 250 V/cm.
Abstract: Recently it has been experimentally shown that saw tooth shaped p/sup +/ strips allows confinement of drifting electrons in the lateral direction. This is achieved by means of potential gutters induced by an appropriate saw tooth design of p/sup +/ cathodes. The saw tooth period p/sub x/ (=anode pitch) is the parameter mainly determining the maximal capacity of confined charge. Up-to-now the confinement effect was experimentally observed with a saw tooth detector with p/sub x/=500 /spl mu/m. The final detector is intended to have an anode pitch of 250 /spl mu/m. The simulation of a saw tooth configuration with p/sub x/=250 /spl mu/m, p/sub y/=200 /spl mu/m, and /spl alpha/=60/spl deg/ showed that potential gutters with a depth of 80 mV will be produced assuming a drift field of 250 V/cm. We will give experimental evidence of these shallow charge confining potential gutters.
TL;DR: In this article, the authors describe the design and the optimisation of a gamma-ray tomography tool to be used for the measure of the particle density in fluidised beds. But the set-up consists of a radioactive line source (35 cm long) perpendicular to the axis of the bed (15 cm diameter) and a standard medical gamma camera equipped with a lead collimator (~ 0.02 rad acceptance angle).
Abstract: This paper describes the design and the optimisation of a gamma-ray tomography tool to be used for the measure ment of the particle density in fluidised beds. The set-up consists of a radioactive line source (35 cm long) perpendicular to the axis of the bed (15 cm diameter) and a standard medical gamma camera equipped with a lead collimator (~ 0.02 rad acceptance angle). An optimum gamma-ray energy of ~ 200 keV is deduced. It is shown that no corrections for imperfect collimation are necessary given the small acceptance angle of the collimator. It is estimated that the density profile can be obtained with an absolute accuracy of ± 25 kg/m3 and a spatial resolution of 2.5 mm. The maximum source strength is limited by the maximum count rate of the gamma camera. With a 75Se source of 130 mCi the measuring time for a density profile under the assumption of cylinder symmetry is in the order of 150 s.
Journal Article•
TL;DR: In this article, ππ correlations in the exclusive reaction at rest with complete reconstruction of the kinematics for each event were studied, showing that the signal is strongest when the π 0 energy is large and much weaker when this energy is small.