Particle detectors at future collider experiments will operate at high collision rates and thus will have to face high pile up and a harsh radiation environment. Precision timing capabilities can ...help in the reconstruction of physics events by mitigating pile up effects. In this context, radiation tolerant, scintillating crystals coupled to silicon photomultipliers (SiPMs) can provide a flexible and compact option for the implementation of a precision timing layer inside large particle detectors. In this paper, we compare the timing performance of aluminum garnet crystals (YAG: Ce, LuAG: Ce, GAGG: Ce) and the improvements of their time resolution by means of codoping with Mg2+ ions. The crystals were read out using SiPMs from Hamamatsu glued to the rear end of the scintillator and their timing performance was evaluated by measuring the coincidence time resolution (CTR) of 150GeV charged pions traversing a pair of crystals. The influence of crystal properties, such as density, light yield and decay kinetics on the timing performance is discussed.
The best single detector time resolutions are in the range of 23–30ps (sigma) and only achieved by codoping the garnet crystals with divalent ions, such as Mg2+. The much faster scintillation decay in the co-doped samples as compared to non co-doped garnets explains the higher timing performance. Samples of LSO: Ce, Ca and LYSO:Ce crystals have also been used as reference time device and showed a time resolution at the level of 17ps, in agreement with previous results.
Precise timing capability will be a key aspect of particle detectors at future high energy colliders, as the time information can help in the reconstruction of physics events at the high collision ...rate expected there. Other than being used in detectors for PET, fast scintillating crystals coupled to compact Silicon Photomultipliers (SiPMs) constitute a versatile system that can be exploited to realize an ad-hoc timing device to be hosted in a larger high energy physics detector. In this paper, we present the timing performance of LYSO:Ce and LSO:Ce codoped 0.4% Ca crystals coupled to SiPMs, as measured with 150 GeV muons at the CERN SPS H2 extraction line. Small crystals, with lengths ranging from 5 mm up to 30 mm and transverse size of 2×2mm2 or 3×3mm2, were exposed to a 150 GeV muon beam. SiPMs from two different companies (Hamamatsu and FBK) were used to detect the light produced in the crystals. The best coincidence time resolution value of (14.5±0.5)ps , corresponding to a single-detector time resolution of about 10 ps, is demonstrated for 5 mm long LSO:Ce,Ca crystals coupled to FBK SiPMs, when time walk corrections are applied.
The electromagnetic calorimeter (ECAL) of the CMS experiment at the CERN Large Hadron Collider is a hermetic, fine grained, homogeneous calorimeter containing 75848 lead tungstate crystals, completed ...by a silicon preshower installed in front of the endcaps. The main characteristics of the ECAL are reviewed. These include the challenges of calibration and triggering in the LHC environment, as well as the reconstruction and identification of photons and electrons. Several results achieved by the CMS experiment particularly exploit the ECAL excellent performance, here illustrated with reference to specific examples, comprising the Higgs boson search and characterization in the H arrow right gamma gamma and H arrow right ZZ super((*)) decay channels and the search for non-standard phenomena such as high-mass gauge bosons decaying into electrons and long-lived particles with delayed signals in the calorimeter.
Undoped and Ce-doped Lu3Al5O12 (LuAG) and Y3Al5O12 (YAG) single crystal fibers were grown by the micro-pulling down technique (μ-PD) with a purpose to fit the design of new dual-readout calorimeter ...planned to operate in future experiences of high energy physics. Fibers up to 20 cm in length and 1 mm in diameter were grown along 111 direction. Based on the measurements of the attenuation length along the fibers, the growth conditions to improve the fibers quality were selected. Our results showed that the grown fibers have the capability to be used for future detectors.
•Ce-doped YAG and LuAG were grown by μ-PD technique.•The Ce segregation is more strong in LuAG than YAG.•Light propagation losses correspond to self-absorption and reflection losses in the fibers.
Abstract
The barrel section of the novel MIP Timing Detector (MTD)
will be constructed as part of the upgrade of the CMS experiment to
provide a time resolution for single charged tracks in the range ...of
30–60 ps using LYSO:Ce crystal arrays read out with
Silicon Photomultipliers (SiPMs). A major challenge for the
operation of such a detector is the extremely high radiation level,
of about 2 × 10
14
1 MeV(Si) Eqv. n/cm
2
, that will be
integrated over a decade of operation of the High Luminosity Large
Hadron Collider (HL-LHC). Silicon Photomultipliers exposed to
this level of radiation have shown a strong increase in dark count
rate and radiation damage effects that also impact their gain and
photon detection efficiency. For this reason during operations the
whole detector is cooled down to about -35°C. In this
paper we illustrate an innovative and cost-effective solution to
mitigate the impact of radiation damage on the timing performance of
the detector, by integrating small thermo-electric coolers (TECs) on
the back of the SiPM package. This additional feature, fully
integrated as part of the SiPM array, enables a further decrease in
operating temperature down to about -45°C. This leads to a
reduction by a factor of about two in the dark count rate without
requiring additional power budget, since the power required by the
TEC is almost entirely offset by a decrease in the power required
for the SiPM operation due to leakage current. In addition, the
operation of the TECs with reversed polarity during technical stops
of the accelerator can raise the temperature of the SiPMs up to
60°C (about 50°C higher than the rest of the
detector), thus accelerating the annealing of radiation damage
effects and partly recovering the SiPM performance.
Abstract The CMS detector will be upgraded for the HL-LHC to include a MIP Timing Detector (MTD). The MTD will consist of barrel and endcap timing layers, BTL and ETL respectively, providing ...precision timing of charged particles. The BTL sensors are based on LYSO:Ce scintillation crystals coupled to SiPMs with TOFHIR2 ASICs for the front-end readout. A resolution of 30–60 ps for MIP signals at a rate of 2.5 Mhit/s per channel is expected along the HL-LHC lifetime. We present an overview of the TOFHIR2 requirements and design, simulation results and measurements with TOFHIR2 ASICs. The measurements of TOFHIR2 associated to sensor modules were performed in different test setups using internal test pulses or blue and UV laser pulses emulating the signals expected in the experiment. The measurements show a time resolution of 24 ps initially during Beginning of Operation (BoO) and 58 ps at End of Operation (EoO) conditions, matching well the BTL requirements. We also showed that the time resolution is stable up to the highest expected MIP rate. Extensive radiation tests were performed, both with x-rays and heavy ions, showing that TOFHIR2 is not affected by the radiation environment during the experiment lifetime.
CMS results are presented on the measurement of properties of the Higgs-like particle discovered last summer with a mass in the range of 125-126 GeV, based on the full statistics of about 25 fb ...super(?1), collected in 2011 and 2012 at 7 and 8 TeV respectively. Five decay channels are considered for these studies, namely the ZZ, yy, WW, TT, and bb modes. The mass of the new boson is measured to be 125.7 + or - 0.4 GeV. The event yields measured by the different analyses, targeting specific decay modes and production mechanisms, are consistent with those expected for the standard model (SM) Higgs boson, with an overall best-fit signal strength of 0.80 + or - 0.14 at the measured mass. A discussion on the measurement of the couplings and the spin-parity properties of this new particle is presented, using
A large sample of cosmic ray events collected by the CMS detector has been exploited to measure the muon stopping power in the lead tungstate (PbWO4) of the electromagnetic calorimeter. The events ...were recorded in October-November 2008, during commissioning runs of the CMS detector with the solenoid at the nominal field strength of 3.8 T. The measurement spans a momentum range from 5 to 1000 GeV/c. The results are consistent with the expectations over the entire range. A comparison of collision losses with radiative losses allowed for a first experimental determination of muon critical energy in lead tungstate, measured to be 160+5−6 (stat.) ± 8 (syst.) GeV, in agreement with expectations.
The progresses in the micropulling-down technique allow heavy scintillating crystals to be grown directly into a fibre geometry of variable shape, length and diameter. Examples of materials that can ...be grown with this technique are Lutetium Aluminum Garnets (LuAG, Lu sub(3)Al sub(5)O sub(12)) and Yttrium Aluminum Garnets (YAG, Y sub(3)Al sub(5)O sub(12)). Thanks to the flexibility of this approach, combined with the high density and good radiation hardness of the materials, such a technology represents a powerful tool for the development of future calorimeters. As an important proof of concept of the application of crystal fibres in future experiments, a small calorimeter prototype was built and tested on beam. A grooved brass absorber (dimensions 26cmx7cmx16cm) was instrumented with 64 LuAG fibres, 56 of which were doped with Cerium, while the remaining 8 were undoped. Each fibre was readout individually using 8 eightfold Silicon Photomultiplier arrays, thus providing a highly granular description of the shower development inside the module as well as good tracking capabilities. The module was tested at the Fermilab Test Beam Facility using electrons and pions in the 2-16 GeV energy range. The module performance as well as fibre characterization results from this beam test are presented.
DSB:Ce3+ scintillation glass for future Auffray, E; Akchurin, N; Benaglia, A ...
Journal of physics. Conference series,
02/2015, Letnik:
587, Številka:
1
Journal Article
Recenzirano
Odprti dostop
One of the main challenges for detectors at future high-energy collider experiments is the high precision measurement of hadron and jet energy and momentum. One possibility to achieve this is the ...dual-readout technique, which allows recording simultaneously scintillation and Cherenkov light in an active medium in order to extract the electromagnetic fraction of the total shower energy on an event- by-event basis. Making use of this approach in the high luminosity LHC, however, puts stringent requirements on the active materials in terms of radiation hardness. Consequently, the R&D carried out on suitable scintillating materials focuses on the detector performance as well as on radiation tolerance. Among the different scintillating materials under study, scintillating glasses can be a suitable solution due to their relatively simple and cost effective production. Recently a new type of inorganic scintillating glass: Cerium doped DSB has been developed by Radiation Instruments and New Components LLC in Minsk for oil logging industry. This material can be produced either in form of bulk or fiber shape with diameter 0.3-2mm and length up to 2000 mm. It is obtained by standard glass production technology at temperature 1400°C with successive thermal annealing treatment at relatively low temperature. The production of large quantities is relatively easy and the production costs are significantly lower compared to crystal fibers. Therefore, this material is considered as an alternative and complementary solution to crystal fibers in view of a production at industrial scale, as required for a large dual readout calorimeter. In this paper, the first results on optical, scintillation properties as well as the radiation damage behaviour obtained on different samples made with different raw materials and various cerium concentrations will be presented.
PDF
