The anticipated performance of calorimeter crystals in the environment expected after the planned High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN has to be well understood, before informed decisions can be made on the need for detector upgrades. Throughout the years of running at the HL-LHC, the detectors will be exposed to considerable fluences of fast hadrons, that have been shown to cause cumulative transparency losses in Lead Tungstate scintillating crystals. In this study, we present direct evidence of the main underlying damage mechanism. Results are shown from a test that yields a direct insight into the nature of the hadron-specific damage in Lead Tungstate calorimeter crystals exposed to 24 GeV/c protons.
We report on the performance of a monitoring system for a prototype calorimeter for the BTeV experiment that uses Lead Tungstate crystals coupled with photomultiplier tubes. The tests were carried out at the 70 GeV accelerator complex at Protvino, Russia.
A Cerium Fluoride crystal produced during early R&D studies for calorimetry at the CERN Large Hadron Collider was exposed to a 24 GeV/c proton fluence Phi_p=(2.78 +- 0.20) x 10EE13 cm-2 and, after one year of measurements tracking its recovery, to a fluence Phi_p=(2.12 +- 0.15) x 10EE14 cm-2. Results on proton-induced damage to the crystal and its spontaneous recovery after both irradiations are presented here, along with some new, complementary data on proton-damage in Lead Tungstate. A comparison with FLUKA Monte Carlo simulation results is performed and a qualitative understanding of high-e…
Results are presented of beam tests in which a small electromagnetic calorimeter consisting of lead tungstate crystals was exposed to 50 GeV electrons and pions. This calorimeter was backed up by the DREAM Dual-Readout calorimeter, which measures the scintillation and Čerenkov light produced in the shower development, using two different media. The signals from the crystal calorimeter were analyzed in great detail in an attempt to determine the contributions from these two types of light to the signals, event by event. This information makes it possible to eliminate the dominating source of fl…
A Lead Tungstate crystal produced for the electromagnetic calorimeter of the CMS experiment at the LHC was cut into three equal-length sections. The central one was irradiated with 290 MeV/c positive pions up to a fluence of (5.67 +- 0.46)x10^13 /cm^2, while the other two were exposed to a 24 GeV/c proton fluence of (1.17 +- 0.11) x 10^13/ cm^2. The damage recovery in these crystals, stored in the dark at room temperature, has been followed over two years. The comparison of the radiation-induced changes in light transmission for these crystals shows that damage is proportional to the star dens…
A highly stable monitoring system based on blue and red light emitting diodes coupled to a distribution network comprised of optical fibers has been developed for an electromagnetic calorimeter that uses lead tungstate crystals readout with photomultiplier tubes. We report of the system prototype design and on the results of laboratory tests. Stability better than 0.1% (r.m.s.) has been achieved during one week of prototype operation.
We report on the effects of radiation on the light output of lead tungstate crystals. The crystals were irradiated by pure, intense high energy electron and hadron beams as well as by a mixture of hadrons, neutrons and gammas. The crystals were manufactured in Bogoroditsk, Apatity (both Russia), and Shanghai (China). These studies were carried out at the 70-GeV proton accelerator in Protvino.
Commissioning of the large-scale lead tungstate scintillating calorimeter
Thomas Jefferson National Accelerator Facility（托马斯·杰斐逊国家加速器设施）；University of North Carolina at Wilmington（北卡罗来纳大学温斯顿-塞勒姆分校）；A. I. Alikhanian National Science Laboratory (Yerevan Physics Institute)（A.I.阿利哈尼扬国家科学实验室（埃里温物理研究所））
Studies of the radiation hardness of lead tungstate crystals produced by the Bogoroditsk Techno-Chemical Plant in Russia and the Shanghai Institute of Ceramics in China have been carried out at IHEP, Protvino. The crystals were irradiated by a 40-GeV pion beam. After full recovery, the same crystals were irradiated using a $^{137}Cs$ $γ$-ray source. The dose rate profiles along the crystal length were observed to be quite similar. We compare the effects of the two types of radiation on the crystals light output.
The CMS detector at the LHC is in the final stages of preparation. The high resolution Electromagnetic Calorimeter, which consists of nearly 76000 lead tungstate crystals, will play a crucial role in the coming physics searches undertaken by CMS. The design, status, and initial performance of the calorimeter, in test beams and with cosmic rays, will be reviewed.
A large sample of cosmic ray events collected by the CMS detector is exploited to measure the specific energy loss of muons in the lead tungstate of the electromagnetic calorimeter. The measurement spans a momentum range from 5 GeV/c to 1 TeV/c. The results are consistent with the expectations over the entire range. The calorimeter energy scale, set with 120 GeV/c electrons, is validated down to the sub-GeV region using energy deposits, of order 100 MeV, associated with low-momentum muons. The muon critical energy in lead tungstate is measured to be 160+5/-6 plus or minus 8 GeV, in agreement w…
Radiation damage in lead tungstate crystals reduces their transparency. The calibration that relates the amount of light detected in such crystals to incident energy of photons or electrons is of paramount importance to maintaining the energy resolution the detection system. We report on tests of lead tungstate crystals, read out by photomultiplier tubes, exposed to irradiation by monoenergetic electron or pion beams. The beam electrons themselves were used to measure the scintillation light output, and a blue light emitting diode (LED) was used to track variations of crystals transparency. We…
Fast hadrons have been observed to cause a cumulative damage in Lead Tungstate and LYSO crystals. The underlying mechanism has been proven to be the creation of fission tracks, which act as scattering centres, thus reducing the light collection efficiency. For calorimetry applications in an environment where large, fast hadron fluences are anticipated, predictions about damage in crystals are of great importance for making an informed choice of technology. In the study presented here, simulations using the FLUKA package have been performed on Lead Tungstate, LYSO and Cerium Fluoride, and their…
Eight production quality PbWO4 crystals of CMS have been irradiated in a 20 GeV/c proton beam up to fluences of 5.4E13cm-2. The damage recovery in these crystals has been followed for over a year. Comparative irradiations with 60Co photons have been performed on seven other crystals using a dose rate of 1 kGy/h. In proton irradiated crystals the light transmission band-edge shifts and the induced absorption length is proportional to the inverse of the 4th power of the wavelength. In gamma-irradiated crystals the band-edge does not shift but formation of absorption bands is seen clearly. The ab…
The resolution and the linearity of time measurements made with the CMS electromagnetic calorimeter are studied with samples of data from test beam electrons, cosmic rays, and beam-produced muons. The resulting time resolution measured by lead tungstate crystals is better than 100 ps for energy deposits larger than 10 GeV. Crystal-to-crystal synchronization with a precision of 500 ps is performed using muons produced with the first LHC beams in 2008.
We present measurements of the reduction of light output by plastic scintillators irradiated in the CMS detector during the 8 TeV run of the Large Hadron Collider and show that they indicate a strong dose rate effect. The damage for a given dose is larger for lower dose rate exposures. The results agree with previous measurements of dose rate effects, but are stronger due to the very low dose rates probed. We show that the scaling with dose rate is consistent with that expected from diffusion effects.
The performance demands of future particle-physics experiments investigating the high-energy frontier pose a number of new challenges, forcing us to find new solutions for the detection, identification, and measurement of final-state particles in subnuclear collisions. One such challenge is the precise measurement of muon momenta at very high energy, where the curvature provided by conceivable magnetic fields in realistic detectors proves insufficient to achieve the desired resolution. In this work we show the feasibility of an entirely new avenue for the measurement of the energy of muons bas…
The operation and general performance of the CMS electromagnetic calorimeter using cosmic-ray muons are described. These muons were recorded after the closure of the CMS detector in late 2008. The calorimeter is made of lead tungstate crystals and the overall status of the 75848 channels corresponding to the barrel and endcap detectors is reported. The stability of crucial operational parameters, such as high voltage, temperature and electronic noise, is summarised and the performance of the light monitoring system is presented.
The energy dependence of the energy and position resolutions of the electromagnetic calorimeter prototype made of lead tungstate crystals produced in Bogoroditsk (Russia) and Shanghai (China) is presented. These measurementswere carried out at the Protvino accelerator using a 1 to 45 GeV electron beam. The crystals were coupled to photomultiplier tubes. The dependence of energy and position resolutions on different factors as well as the measured electromagnetic shower lateral profile are presented.
Measurements are presented of the reduction of signal output due to radiation damage for plastic scintillator tiles used in the hadron endcap (HE) calorimeter of the CMS detector. The tiles were exposed to particles produced in proton-proton (pp) collisions at the CERN LHC with a center-of-mass energy of 13 TeV, corresponding to a delivered luminosity of 50 fb$^{-1}$. The measurements are based on readout channels of the HE that were instrumented with silicon photomultipliers, and are derived using data from several sources: a laser calibration system, a movable radioactive source, as well as …
Application of sequence learning for predicting radiation damage of the CMS electromagnetic calorimeter
Facultad de Ciencias, Universidad Nacional Autónoma de México（墨西哥国立自治大学理学院）；Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México（墨西哥国立自治大学核科学研究所）
The CMS hadron Calorimeter is made of alternating layers of scintillating tiles and metals, such as brass or iron. The original photo detectors were hybrid units with a single accelerating gap called Hybrid Photo Diodes (HPD). Scintillating light was transmitted to the HPDs by means of optical fibers. During data taking at the Large Hadron Collider (LHC), the signal strength of scintillator tiles of detector units in the forward region degraded significantly due to the damage related to the amount of radiation to which the scintillator was exposed to. Scintillators suffer damage when exposed t…
Scintillating crystals are used for calorimetry in several high-energy physics experiments. For many of them, performance has to be ensured in very difficult operating conditions, like a high radiation environment and large particle fluxes, which place constraints on response and readout time. An overview is presented of the knowledge reached up to date, and of the newest achievements in the field, with particular attention given to the performance of Lead Tungstate crystals exposed to large particle fluxes.
Hadrons emerging from high-energy collisions, as it is the case for protons and pions at the CERN Large Hadron Collider, can produce a damage to inorganic crystals that is specific and cumulative. The mechanism is well understood as due to bulk damage from fragments caused by fission. In this paper, the existing experimental evidence for lead tungstate, LYSO and cerium fluoride is summarised, a study using FLUKA simulations is described and its results are discussed and compared to measurements. The outcome corroborates the confidence in the predictive power of such simulations applied to inor…
The electromagnetic calorimeter of PANDA at the FAIR facility will rely on an operation of lead tungstate (PWO) scintillation crystals at temperatures near -25 deg.C to provide sufficient resolution for photons in the energy range from 8 GeV down to 10 MeV. Radiation hardness of PWO crystals was studied at the IHEP (Protvino) irradiation facility in the temperature range from room temperature down to -25 deg.C. These studies have indicated a significantly different behaviour in the time evolution of the damaging processes well below room temperature. Different signal loss levels at the same do…
Kinetics of radiation damage of the PWO crystals under irradiation and recovery were studied. Crystals were irradiated with dose corresponding to average one expected in the electromagnetic calorimeter (working dose irradiation). Radiation damage and recovery were monitored through measurements of PWO optical transmission. An approach is proposed which allows evaluating the influence of the PWO crystals properties on the statistical term in the energy resolution of the electromagnetic calorimeter. The analysis also gives important information about the nature of the radiation damage mechanism …
The PANDA detection system at FAIR, Germany, is designed to study antiproton-proton annihilations, in order to investigate among others the realm of charm-meson states and glueballs, which has still much to reveal. The yet unknown properties of this field are to be unraveled through studying QCD phenomena in the non-perturbative regime. The multipurpose PANDA detector will be capable of tracking, calorimetry, and particle identification, and is foreseen to run at high luminosities providing average reaction rates up to 20 Million interactions/s. The envisaged physics program requires measureme…
Eight PbWO4 crystals produced for the electromagnetic calorimeter of the CMS experiment at LHC have been irradiated in a 20 GeV/c proton beam up to fluences of 5.4 E13 p/cm2. The damage recovery in these crystals, stored in the dark at room temperature, has been followed for over a year. Comparative irradiations with 60Co photons have been performed on seven other crystals using a dose rate of 1 kGy/h. The issue whether hadrons cause a specific damage to the scintillation mechanism has been studied through light output measurements on the irradiated crystals using cosmic rays. The correlation …
Beam test, simulation, and performance evaluation of PbF$_2$ and PWO-UF crystals with SiPM readout for a semi-homogeneous calorimeter prototype with longitudinal segmentation
Exploring the limits of high-energy proton-pion separation in granular calorimeters
University of Tennessee, Knoxville（田纳西大学诺克斯维尔分校）；Universidad de Oviedo（奥维耶多大学）；CERN, European Organization for Nuclear Research（欧洲核子研究组织（CERN））；University of Padova, Department of Physics and Astronomy（帕多瓦大学物理与天文学系）；Luleå University of Technology（吕勒奥理工学院）；Istituto Nazionale di Fisica Nucleare, Sezione di Padova（意大利国家核物理研究所帕多瓦分部）
Throughout the year 2011, the Large Hadron Collider (LHC) has operated with an instantaneous luminosity that has risen continually to around 4x10^33cm-2 s-1. With this prodigious high-energy proton collisions rate, efficient triggering on electrons and photons has become a major challenge for the LHC experiments. The Compact Muon Solenoid (CMS) experiment implements a sophisticated two-level online selection system that achieves a rejection factor of nearly 106. The first level (L1) is based on coarse information coming from the calorimeters and the muon detectors while the High-Level Trigger …
Lutetium-Yttrium Orthosilicate doped with Cerium (LYSO:Ce), as a bright scintillating crystal, is a candidate for calorimetry applications in strong ionizing-radiation fields and large high-energy hadron fluences as are expected at the CERN Large Hadron Collider after the planned High-Luminosity upgrade. There, proton-proton collisions will produce fast hadron fluences up to ~5E14/cm^2 in the large-rapidity regions of the calorimeters. The performance of LYSO:Ce has been investigated, after exposure to different fluences of 24 GeV/c protons. Measured changes in optical transmission as a functi…
Enhancing Electromagnetic Calorimeter Signal Reconstruction with Machine Learning-Based Noise Discrimination
High Energy Nuclear and Particle Physics Division, Saha Institute of Nuclear Physics - a CI of Homi Bhabha National Institute（萨哈核物理研究所高能核与粒子物理系（霍米·巴巴国立学院下属机构））；Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole polytechnique, Institut Polytechnique de Paris（勒普朗斯-林盖特实验室，法国国家科学研究中心/法国国家粒子物理研究所，巴黎综合理工学院，巴黎理工学院）；Department of Physics and Astronomy, Stony Brook University - SUNY（纽约州立大学石溪分校物理与天文学系）；University of Virginia（弗吉尼亚大学）；Department of High Energy Physics, Tata Institute of Fundamental Research（塔塔基础研究所高能物理系）
We employed two independent methods to study possible damage to the scintillation mechanism in lead tungstate crystals due to irradiation by a 34 GeV pion beam. First, 10 crystals were irradiated simultaneously over 30 hours by a narrow beam, so that only a small region of each crystal was affected. We studied the effect of the irradiation on the light output non-uniformity. If a localized degradation was observed, it would indicate damage to the scintillation mechanism. Secondly, we detected light output using two phototubes attached to sides of a crystal. Since these phototubes detect scinti…
High-Luminosity running at the LHC, which is planned for 2022 and beyond, will imply an order of magnitude increase in radiation levels and particle fluences with respect to the present LHC running conditions. The performance evolution of the CMS electromagnetic calorimeter (ECAL), comprising 75,848 scintillating lead tungstate crystals, indicates that an upgrade of its endcaps will be needed for HL-LHC running, to ensure an adequate performance. Results from LHC collision periods, beam tests and laboratory measurements of proton-irradiated crystals are combined to predict the performance of t…
The CMS electromagnetic calorimeter (ECAL) is a high-resolution, hermetic, and homogeneous calorimeter made of 75,848 scintillating lead tungstate crystals. Following the discovery of the Higgs boson, the CMS ECAL is at the forefront of precision measurements and the search for new physics in data from the LHC, which recently began producing collisions at the unprecedented energy of 13 TeV. The exceptional precision of the CMS ECAL, as well as its timing performance, are invaluable tools for the discovery of new physics at the LHC Run 2. The excellent performance of the ECAL relies on precise …
The electro-magnetic calorimeter at the BaBar detector, part of the asymmetric B Factory at SLAC, measures photons in the energy range from 20 MeV to 8 GeV with good resolution. The calorimeter is calibrated at the low energy end with 6.13 MeV photons obtained from a liquid source system. During the calibration, a fluorine-rich liquid is activated via a neutron generator and pumped past the front of the calorimeter's crystals. Decays that occur in front of the crystals emit photons of well-defined energy, which are detected in the crystals with the regular data acquisition system. The liquid s…
Radiation damage of new heavy LFS-3 scintillating crystals has been studied using powerful $^{60}Co$ source at the dose rate of 4 Krad/min. No deterioration in optical transmission of LFS-3 crystals was observed after irradiation with the dose of 23 Mrad.
The 75,848 lead tungstate crystals in CMS experiment at the CERN Large Hadron Collider are used to measure the energy of electrons and photons produced in the proton-proton collisions. The optical transparency of the crystals degrades slowly with radiation dose due to the beam-beam collisions. The transparency of each crystal is monitored with a laser monitoring system that tracks changes in the optical properties of the crystals due to radiation from the collision products. Predicting the optical transparency of the crystals, both in the short-term and in the long-term, is a critical task for…
Istituto Nazionale di Fisica Nucleare Sezione di Torino（意大利国家核物理研究所都灵分部）；Thomas Jefferson National Accelerator Facility（托马斯杰斐逊国家加速器设施）；Istituto Nazionale di Fisica Nucleare, Sezione di Genova e Dipartimento di Fisica dell’Università（意大利国家核物理研究所热那亚分部及大学物理系）；Istituto Nazionale di Fisica Nucleare, Sezione di CATANIA（意大利国家核物理研究所卡塔尼亚分部）；University of Glasgow（格拉斯哥大学）；Institut de Physique Nucléaire, CNRS/IN2P3, Université Paris-Saclay（巴黎萨克雷大学CNRS/IN2P3核物理研究所）；Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tor Vergata and Dipartimento di Fisica dell’Università di Roma Tor Vergata（意大利国家核物理研究所罗马托维加塔分部及罗马托维加塔大学物理系）
Hadronic Forward(HF) detector is one of the sub-detectors of the CMS. It plays an important role in the measurement of forward jets and missing energy. HF is situated on both sides of the CMS interaction point, at about $\pm$11 m, covers the very forward angles of CMS, in the pseudorapidity range (3.0 < | $η$ | < 5.0), leaving only clearance for the beam pipes. This calorimeter consists of quartz fibers embedded in the iron absorber. Cherenkov light created by the charged particles is transmitted to PMTs by the fibers. Fibers due to the proton-proton collisions are exposed to high radiation. T…
The Phase-2 ATLAS upgrade for the High Luminosity Large Hadron Collider (HL-LHC) has motivated progressive redesigns of the ATLAS Tile Calorimeter (TileCal) read-out link and control board (Daughterboard). The Daughterboard (DB) communicates with the off-detector electronics via two 4.6 Gbps downlinks and two pairs of 9.6 Gbps uplinks. Configuration commands and LHC timing is received through the downlinks by two CERN radiation hard GBTx ASICs and propagated through Ultrascale+ FPGAs to the front-end. Simultaneously, the FPGAs send continuous high-speed readout of digitized PMT samples, slow c…
Conceptual Design of a Novel Highly Granular Crystal Electromagnetic Calorimeter for Future Higgs Factories
Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；State Key Laboratory of Particle Detection and Electronics（粒子探测与电子学国家重点实验室）；University of Chinese Academy of Sciences（中国科学院大学）；China Center of Advanced Science and Technology（中国高等科学技术中心）；Institute of Nuclear and Particle Physics, School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院核物理与粒子物理研究所）；Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交通大学李政道研究所）；National Key Laboratory of Dark Matter Physics, Shanghai Key Laboratory for Particle Physics and Cosmology, Key Laboratory for Particle Astrophysics and Cosmology (MoE)（暗物质物理全国重点实验室、粒子物理与宇宙学上海市重点实验室、粒子天体物理 cosmology 教育部重点实验室）
To make precision measurements with a CsI(Tl) calorimeter in a high luminosity environment requires that the crystals are well calibrated and continually monitored for radiation damage. This should not effect the total integrated luminosity which is particularly important for the \babar calorimeter to enable it to make CP violation measurements in the $B$ meson system. To achieve this goal a fibre-optic light pulser system was designed using xenon flash lamps as the light source. A novel light distribution method was developed using an array of graded index microlenses. Some initial results fr…
Hamamatsu photomultiplier tubes (PMT) and various PMT window materials were exposed to gamma irradiation. Tests were performed with absorbed doses of 1 krad and 120 krad. Initial recommendations on PMT types to use in the BTeV electromagnetic calorimeter are stated.
