Search results for "Instrumentation"
showing 10 items of 4914 documents
Study of the background on a ZnS(Ag) alpha counter with a plastic veto detector
2006
Alpha counters based on the scintillation of ZnS(Ag) have been used widely to measure total alpha activity in environmental samples. The main difficulties for this kind of detectors consist of having a reasonable low background, i.e., around 10−3 counts/s. It is assumed that the background comes from natural sources (mainly radon) and there is no contribution from cosmic, beta or gamma rays since the efficiency for these sources is extremely low. However, the study of the background using a thin plastic veto detector shows that the cosmic ray contribution to the alpha background is about 5–50%, whereas the estimated gamma contribution is below 10%. Therefore, this anti-coincidence set-up ca…
Liquid-scintillation detection of preseparated 257Rf with the SISAK-system
2005
Abstract The fast liquid–liquid extraction system SISAK with continuous liquid scintillation detection was coupled to the Berkeley Gas-filled Separator to enable studies of the chemical properties of α -decaying transactinide elements. The preseparated transactinide 257Rf (4.7 s), was transported via a He/KCl-jet directly into the scintillation solution. This permitted the first unambiguous detection of transactinide atoms by the means of the α -liquid scintillation detectors of the SISAK-system. During the experiment, 89 257Rf atoms were observed. The type of events observed correspond well with the expectations based on half-lives, decay branches and transport- and hold-up times. The succ…
Dependency of Energy-, Position- and Depth of Interaction Resolution on Scintillation Crystal Coating and Geometry
2008
Options for optimizing the energy and spatial resolution of gamma-ray imaging detectors based on thick, monolithic crystals shaped like flat-topped pyramids were studied. Monte Carlo simulations were made of the scintillation light transport for evaluating the effect of four parameters on the energy resolution, the spatial resolutions, and the depth of interaction (DOI) resolution of the gamma-ray imaging detector. These four parameters are: the reflectivity of the surface coating; the scatter mean free path; the absorption mean free path of the scintillation light; and the angle that defines the inclination of the sides of the pyramidal frustum. In real detectors, the values for the mean f…
Electromagnetic calorimetry with PbWO/sub 4/ in the energy regime below 1 GeV
2003
The study of the performance and application of PbWO/sub 4/ in electromagnetic calorimetry at energies far below 1 GeV has been continued. The significantly improved optical and scintillation properties of 15 cm long Nb/La-doped crystals, optimized for the ECAL/CMS calorimeter, are documented. The lineshape, energy and time response of a 5/spl times/5 matrix are tested with monoenergetic photons up to 790 MeV energy and compared to previous measurements. First attempts have been made to enhance the scintillation yield by suitable dopants (Mo,Tb) for applications at very low photon energies. As a first large scale project at medium energies, the proposed concept for a compact photon spectrom…
Maximum likelihood positioning for gamma-ray imaging detectors with depth of interaction measurement
2009
Abstract The center of gravity algorithm leads to strong artifacts for gamma-ray imaging detectors that are based on monolithic scintillation crystals and position sensitive photo-detectors. This is a consequence of using the centroids as position estimates. The fact that charge division circuits can also be used to compute the standard deviation of the scintillation light distribution opens a way out of this drawback. We studied the feasibility of maximum likelihood estimation for computing the true gamma-ray photo-conversion position from the centroids and the standard deviation of the light distribution. The method was evaluated on a test detector that consists of the position sensitive …
Inverted-conical light guide for crosstalk reduction in tightly-packed scintillator matrix and MAPMT assembly
2015
Abstract In this paper we present the Inverted-Conical light guide designed for optical crosstalk reduction in the scintillator-MAPMT assemblies. The research was motivated by the 30% crosstalk observed in UFFO X-ray telescope , UBAT, during the preliminary calibration with MAPMTs of 64 2.88 × 2.88 mm2 pixels and identically gridded YSO crystal matrices. We began the study with the energy and crosstalk calibrations of the detector, then we constructed a GEANT4 simulation with the customized metallic film model as the MAPMT photocathode . The simulation reproduced more than 70% of the crosstalk and explained it as a consequence of the total reflection produced by the photocathode. The result…
Cooling of radioactive ions with the Penning trap REXTRAP
2005
Abstract Cooling of radioactive ion beams in a Penning trap is an essential component of the post-accelerator REX-ISOLDE at CERN. Prior to their charge-breeding and acceleration, ions from the on-line mass separator ISOLDE are accumulated, cooled and bunched with REXTRAP. This beam preparation provides short ion pulses with low emittance, key ingredient for a high efficiency of REX-ISOLDE. Two different cooling techniques have been investigated with REXTRAP. Both rely on the use of a buffer gas as the coolant but differ in the way the transversal compression of the stored ion cloud is achieved. Sideband cooling with a light buffer gas as coolant is the standard technique used at REXTRAP so …
Digital pulse-shape analysis with a TRACE early silicon prototype
2014
[EN] A highly segmented silicon-pad detector prototype has been tested to explore the performance of the digital pulse shape analysis in the discrimination of the particles reaching the silicon detector. For the first time a 200 tun thin silicon detector, grown using an ordinary floating zone technique, has been shown to exhibit a level discrimination thanks to the fine segmentation. Light-charged particles down to few MeV have been separated, including their punch-through. A coaxial HPGe detector in time coincidence has further confirmed the quality of the particle discrimination. K.; 2014 Elsevier B.V. All rights reserved
A dedicated decay-spectroscopy station for the collinear resonance ionization experiment at ISOLDE
2013
A newdecay-spectroscopystation(DSS)has been developed to be coupled to the collinear resonance ionization spectroscopy (CRIS) beam line at CERN-ISOLDE. The system uses a rotatable wheel with ten 20 mg=cm2 carbon foils as beam implantation sites for the efficient measurement of charged decay products. Silicon detectors are placed on either side of the carbon foil in an optimal geometry to cover a large solid angle for detecting these charged particles. In addition to the silicon detectors at the on-beam axis position, a second pair of off-beam axis detectors are placed at the wheel position 108 deg. away, allowing longer-lived species to be studied. Up to three high purity germanium detector…
The ISOLDE Silicon Ball
2003
The development of new spectroscopy devices with the capability of detecting charged particles and precisely determining their energy, angular distribution and nature has become one of the requirements for the investigation of weakly bound nuclei close to the particle driplines. With this aim the ISOLDE Silicon Ball is under construction. It is a charged particle spectroscopy device allowing for the investigation of the exotic nuclei produced at ISOLDE and at other similar facilities. Very high geometrical efficiency and broad energy range coverage are required. In order to allow for particle identification the simultaneous use of the Time of Flight and Pulse Shape Discrimination techniques…