The lead tungstate crystal (PbWO 4 , PWO) is one of the widely used scintillation materials for electromagnetic calorimeters (EMCs) in high-energy physics experiments. The degradation of the optical ...transmittance in the range of the luminescence spectrum under ionizing radiation leads to losses of the light output resulting in the deterioration of the energy resolution and limiting the lifetime of the calorimeter. A possible way to restore radiation damage is the in situ illumination by visible or near-infrared light of the whole crystal volume. It allows recovering the transmittance losses due to the depopulation of the color centers. Such a kind of stimulated recovery subsystem based on a blue light-emitting diode is considered for the EMC of the PANDA detector at Facility for Antiproton and Ion Research (FAIR) (Darmstadt, Germany). Here, we report on the stimulated recovery studies of the lead tungstate radiation damage induced by external light from laser diodes at different wavelengths. The level of technological development of laser diodes allows increasing the efficiency of the stimulated recovery.
A new inorganic scintillation material based on Ba-Gd silica glass doped with cerium (BGS) is fabricated and studied. With the highest light yield among heavy glasses at the level of 2500 ph/MeV and ...fast scintillation response, the new scintillator ensures a good coincidence time resolution of < 230 ps FWHM for 511 keV γ-quanta from a 22Na source and SiPM readout. In addition to good performance in γ-quanta detection, the material demonstrates capability for efficient detection of low-energetic neutrons. The scintillator is produced by exploiting the standard industrial glass technology, which allows for an unlimited scaling up the conversion of raw material into a high-quality scintillator at a high rate. The glass can be casted in application-specific molds, so minimizing the material losses. The presented glass scintillator has potential for further improvement of its light output and scintillation response time.
The future P¯ANDA experiment with a next generation detector will focus on hadron spectroscopy. It will use cooled anti-proton beams with a momentum between 1.5 GeV/c and 15 GeV/c interacting with ...various targets. This allows to directly form all states of all quantum numbers and measure their widths with an accuracy of a few tens of keV. The experiment will be located at the exceptional Facility for Anti-proton and Ion Research in Germany (FAIR), which is currently under construction. The electromagnetic target calorimeter of the P¯ANDA experiment has the challenging aim to detect high energy photons with excellent energy resolution over the full dynamic range from 15 GeV down to a few tens of MeV within a 2 T solenoid. The target calorimeter itself is divided into a barrel and two endcaps. The individual crystals will be read out with two precisely matched large area avalanche photo diodes. In the very inner part of the forward endcap vacuum phototetrodes will be used instead. To reach the demands of the experiment, improved PbWO4 (PWO) scintillator crystals, cooled down to −25°C have been chosen. They provide a fast decay time for highest count rates, short radiation length for compactness, improved light yield for lowest thresholds and excellent radiation hardness 1. The main part of the 15,740 crystals needed have been produced by the Bogoroditsk Plant of Technochemical Products (BTCP) in Russia. After stopping their business, a new potential producer for the missing 41% of crystals have been found. The company Crytur in Czech Republic provided 150 promising preproduction crystals so far. Except some of the very first produced crystals, all samples exceed the required high quality parameters. Most of them have already been used for the first major assembly stage of assembling one of the 16 barrel slice segments, which will be presented as well.
The application of crystalline materials in ionizing radiation detectors has played a crucial role in the discovery of the properties of matter. However, the experiences gathered at high intensity ...machines such as the LHC have indicated their limitations and underlined the requirements for materials being more tolerable to radiation damage in particular caused by energetic hadrons. Systematic studies of the radiation hardness of inorganic optical and scintillation materials propose both oxide and fluoride crystals composed of atoms with atomic numbers below 60. In this study we report on a cheap glass (BaO*2SiO2) and DSB: Ce glass ceramics even capable for mass production. Admixing gadolinium oxide (Gd3+) even provides a two times larger light yield. Both types of the materials can be produced in a fibre and bulk geometry. This paper summarizes the overall performance and reports on a first test of a 3x3 matrix of large volume samples exposed to energy-marked photons up to 180 MeV.
One of the most critical aspects for the application of a scintillation material in high energy physics is the degradation of properties of the material in an environment of highly ionizing particles ...in particular due to hadrons. There are presently several detector concepts in consideration being based on organic scintillator material for fast timing of charged particles or sampling calorimeters. We have tested different samples of the organic plastic scintillator EJ-260 produced by the company Eljen Technology (Sweetwater, TX, USA). The ongoing activity has characterized the relevant parameters such as light output, kinetics and temperature dependence. The study has focused on the change of performance after irradiation with 150 MeV protons up to an integral fluence of 5·1013 protons/cm2 as well as with a strong 60Co γ-source accumulating an integral dose of 100 Gy. The paper will report on the obtained results.
The PANDA collaboration at FAIR, Germany, will focus on undiscovered charm-meson states and glueballs in antiproton annihilations to study QCD phenomena in the non-perturbative regime. For fixed ...target experiments at the storage ring HESR a 4π-detector for tracking, particle ID and calorimetry is under development and construction to operate at high annihilation rates up to 20 MHz. The electromagnetic calorimeters are composed of a target spectrometer (EMC) based on PbWO4 crystals and a shashlyk-type sampling calorimeter at the most forward region. The EMC, comprising more than 15,000 crystals, is operated at a temperature of −25°C and read-out via large-area avalanche photo-diodes or vacuum phototriodes/tetrodes. The photo sensor signals are continuously digitized by sampling ADCs. More than 50 of the high quality PWO-II crystals are delivered and tested. The excellent performance with respect to energy, time and position information was determined over a shower energy range from 10 MeV up to 15 GeV by operating several prototype detectors. In addition, the concept of stimulated recovery has been investigated to recover radiation damage on- and off-line during the calorimeter operation. Besides the overall concept of the target spectrometer the response function of the shashlyk spectrometer down to photon energies even below 100 MeV is presented.
Lead Tungstate (PbWO 4 , PWO) has become presently the most commonly used scintillator material for electromagnetic calorimetry in medium and high-energy physics. There exists substantial demand for ...future calorimeters such as the completion of the PANDA electromagnetic compatibility (EMC) as well as various detector projects under discussion at Jefferson Lab or Brookhaven National Laboratory in the United States. Nearly, 6700 crystals are missing for the barrel section of the PANDA-EMC since the successful mass production of PWO using the Czochralski method was stopped after bankruptcy of the Bogoroditsk Technical Chemical Plant (BTCP) in Russia. Intermediate research and development efforts with the Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai, China, as an existing producer exploiting the modified Bridgman method could not reach the required quality in a consistent manner. End of 2014, the CRYTUR (Turnov, Czech Republic) has restarted the development of lead tungstate based again on the Czochralski method with impressive progress. The modified and optimized technology has already produced full size samples of PWO-II quality. This paper will present a detailed status report on a first preproduction run of 89 crystals focusing on the achieved optical performance, light yield, kinetics, and temperature dependence and radiation hardness.
Performance of the prototype of the electromagnetic calorimeter for PANDA Kavatsyuk, M.; Bremer, D.; Dormenev, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2011, Letnik:
648, Številka:
1
Journal Article
Recenzirano
The PANDA collaboration at FAIR, Germany, will employ antiproton annihilations to investigate yet undiscovered charm-meson states and glueballs. The aim is to study QCD phenomena in the ...non-perturbative regime and to unravel the origin of hadronic masses. A multi-purpose detector for tracking, calorimetry and particle identification is presently being developed to run at high luminosities providing up to 2×107 interactions/s. One of the crucial components of the PANDA spectrometer is the Electromagnetic Calorimeter, composed of cooled PbWO4 crystals. This paper describes construction and performance of a fully functioning prototype of this calorimeter. The performance was determined from measurements exploiting cosmic muons and high-energy tagged photons from the MAMI-C electron accelerator. The response measurements were carried out using sampling ADCs and, for comparison, charge-integrating ADCs. The achieved results validate the usage of sampling ADCs with a moderate sampling frequency, provide the energy resolution as foreseen in the Technical Design Report of the full calorimeter, and secure event correlation by achieving a good timing resolution through digital analysis of the sampled signals.
The early impact behaviour of single and multi-ply Kevlar
® 129 fabric armour systems is investigated using an explicit finite element code, TEXIM, developed in-house. This numerical model is ...carefully validated using continuous temporal data obtained from an instrumented experimental setup. The model is then used to explore the loss in ballistic efficiency of woven fabric targets, as experienced early in the impact event, when either the number of layers in the panel or the yarn denier is increased.
Recently, a new scintillation material DSB: Ce3+ was announced. It can be produced in a form of glass or nano-structured glass ceramics with application of standard glass production technology with ...successive thermal annealing. When doped with Ce3+, material can be applied as scintillator. Light yield of scintillation is near 100 phe/MeV. Un-doped material has a wide optical window from 4.5eV and can be applied to detect Cherenkov light. Temperature dependence of the light yield LY(T) is 0.05% which is 40 times less than in case of PWO. It can be used for detectors tolerant to a temperature variation between -20° to +20°C. Several samples with dimensions of 15x15x7 mm3 have been tested for damage effects on the optical transmission under irradiation with γ-quanta. It was found that the induced absorption in the scintillation range depends on the doping concentration and varies in range of 0.5-7 m−1. Spontaneous recovery of induced absorption has fast initial component. Up to 25% of the damaged transmission is recuperated in 6 hours. Afterwards it remains practically constant if the samples are kept in the dark. However, induced absorption is reduced by a factor of 2 by annealing at 50°C and completely removed in a short time when annealing at 100°C. A significant acceleration of the induced absorption recovery is observed by illumination with visible and IR light. This effect is observed for the first time in a Ce-doped scintillation material. It indicates, that radiation induced absorption in DSB: Ce scintillation material can be retained at the acceptable level by stimulation with light in a strong irradiation environment of collider experiments.
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