ATLAS tile calorimeter calibration

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ATLAS Tile calorimeter calibration and PMT response

ATLAS Tile calorimeter calibration and PMT response

E-mail: djamel.boumediene@cern.ch Abstract: The ATLAS Tile Calorimeter (TileCal) is the central section of the hadronic calorimeter of the ATLAS experiment at the Large Hadron Collider. It provides important information for reconstruction of hadrons, jets, hadronic decays of tau leptons and missing transverse energy. This sampling calorimeter uses steel plates as absorber and scintillating tiles as active medium. Scintillating light is transmitted by wavelength shifting fibres to photomultiplier tubes (PMTs) in the rear girders of the wedge-shaped calorimeter modules. Photomultiplier signals are then digitized at 40 MHz and stored on-detector in digital pipelines. Event data are transmitted off-detector upon a first level trigger acceptance, at a maximum rate of 100 kHz. The readout is segmented into about 5000 cells, each read out by two PMTs on opposite sides of the cells. To calibrate and monitor the stability and performance of each part of the readout chain during the data taking, a set of calibration systems is used. The TileCal calibration system comprises Cesium radioactive sources, a laser, a charge injection system and an integrator based readout system. Combined information from all systems allows the calorimeter response to be monitored and equalised at each stage of the signal production, from scintillation light to digitisation. After exposure to scintillator light for almost 10 years, variations in gain have been observed when the PMTs are exposed to large light currents. These variations have been studied and correlated to some intrinsic properties of the PMTs, including the quantum efficiency, as well as operation conditions like the High Voltage. Latest results and conclusions are presented.
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ATLAS Tile calorimeter calibration and monitoring systems

ATLAS Tile calorimeter calibration and monitoring systems

Constant term is within expected 3%. IV. C ONCLUSION The ATLAS Tile Calorimeter is an important sub-detector of the ATLAS detector at the LHC. It is the hadronic sampling calorimeter made of steel plates which act as absorber and scintillating tiles as active medium. Control of its energy is essential to measure the energy of jets, hadronically decaying tau leptons and missing transverse energy. The TileCal cali- bration system consists of Cesium radioactive sources, laser, charge injection components, and an integrator based readout system. Combined information from all systems allows for an efficient monitoring and correction of fine instabilities of TileCal cells response. Intercalibration and uniformity are monitored with isolated charged hadrons and cosmic muons. Data quality in physics runs is monitored extensively and continuously. All problems are reported and addressed. The data quality efficiency achieved was 99.6% in 2012, 100% in 2015, 98.9% in 2016 and 99.4% in 2017. The stability of the absolute energy scale at the cell level was maintained to better than 1% during LHC data-taking. Following the experience gained during LHC Run-I, all calibration systems were improved for Run-II. TileCal performance during LHC Run-II, (2015-2018), including calibration, stability, absolute energy scale, uniformity and time resolution show that the TileCal performance is within the design requirements and has given essential contribution to reconstructed objects and physics results.
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The Laser calibration of the Atlas Tile Calorimeter during the LHC run 1

The Laser calibration of the Atlas Tile Calorimeter during the LHC run 1

1.2 Detector readout Each fibre bundle, usually corresponding to one side of a cell, is read out by a photomultiplier tube: each standard cell is thus read out by two PMTs, the E cells being read out by a single PMT. Therefore, there are 9852 PMTs in total. The electric pulses generated by the PMTs are shaped [4] and digitised [5] at 40 MHz with two different gains, with a ratio of 64, in order to achieve a good precision in a wide energy range. These samples are then stored in a pipeline memory until the level-1 trigger decision is taken (ATLAS has a three-level trigger system, the first level giving a decision in 2.5 µs during which the data are kept in the front-end electronics). If the decision is positive, seven samples, in time with the signal and with appropriate gain giving the best precision on the pulse amplitude, are sent to the off-detector electronics (Read Out Drivers or RODs [6]). The amplitude of the signal is reconstructed as the weighted linear combination of the digitised signal samples, using an optimal filtering method [7, 8].
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The ATLAS Tile Calorimeter performance in the LHC Run 2 and its upgrade towards the High-Luminosity LHC

The ATLAS Tile Calorimeter performance in the LHC Run 2 and its upgrade towards the High-Luminosity LHC

bunch crossing. Figure 9 shows the average jet energy resolution as a function of hµi. This figure shows that the jet kinematics in very high pile-up conditions can be reconstructed at the HL-LHC with nearly equal precision as in Run 2. The jets used here are reconstructed from topo-clusters using the anti-kt algorithm [ 4 ] with a distance parameter of R=0.4. The jet calibration scheme

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FATALIC: A fully integrated electronics readout for the ATLAS tile calorimeter at the HL-LHC

FATALIC: A fully integrated electronics readout for the ATLAS tile calorimeter at the HL-LHC

Abstract The ATLAS Collaboration has started a vast program of upgrades in the context of high-luminosity LHC (HL-LHC) foreseen in 2024. The current readout electronics of every sub-detector, including the Tile Calorimeter, must be upgraded to comply with the extreme HL-LHC operating conditions. The ASIC described in this document, named Front-end ATlAs tiLe Integrated Circuit (FATALIC), has been developed to fulfill these requirements. FATALIC is based on a 130 nm CMOS technology and performs the complete signal processing (amplification, shaping and digitization) over a large dynamic range. A dedicated channel for low current is also designed to perform the detector calibration with a radioactive cesium source. The design and performances of FATALIC are described including test beam data analysis.
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The High Voltage distribution system of the ATLAS Tile Calorimeter and its performance during data taking

The High Voltage distribution system of the ATLAS Tile Calorimeter and its performance during data taking

In 2016, among these three channels, one remained stable with the same large offset of ≈ 10 V while the two others became unstable. It must be noted that whatever the offset is, as long as the value is stable it does not affect the performances of the energy measurement. Indeed, the high voltage values are not used in the energy computation, the energy scale being set by the Cesium calibration [ 20 ]. However, a large offset may be the hint of a serious problem in the regulation loop and it is useful for the maintenance. The total number of problematic channels, unstable or with a large offset, was 27 in 2015 and 19 in 2016. They correspond to 0.3% and 0.2% of the investigated channels in the two periods.
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Measurement of pion and proton response and longitudinal shower profiles up to 20 nuclear interaction lengths with the ATLAS Tile calorimeter

Measurement of pion and proton response and longitudinal shower profiles up to 20 nuclear interaction lengths with the ATLAS Tile calorimeter

The signal calibrated with the CIS- and the Cs-system is converted to an absolute energy using a calibration factor (F pC→GeV ) that is obtained using electrons. This calibration factor defines the “electromagnetic scale”. The re- sponse of the TileCal cells of about 10% of the TileCal modules installed in the ATLAS detector has been studied using electron test-beams in 2002 and 2003 [ 18 ]. The average response of high energetic electrons impinging at a po- lar angle of 20 o on the TileCal divided by the beam energy is defined as the F pC→GeV calibration factor 14 . It is measured to be F pC→GeV = 1.050 ± 0.003 pC/GeV. The cell response variation is 2.4 ± 0.1% [ 18 , 16 ]. The dominant part of the residual cell non-uniformity of about 2% for electrons is due to differences in the optical properties of the tiles and the read-out fibres (intra-cell) 15 .
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A Complete Readout Chain of the ATLAS Tile Calorimeter for the HL-LHC: from FATALIC Front-End Electronics to Signal Reconstruction

A Complete Readout Chain of the ATLAS Tile Calorimeter for the HL-LHC: from FATALIC Front-End Electronics to Signal Reconstruction

Abstract—The ATLAS Collaboration has started a vast pro- gramme of upgrades in the context of high-luminosity LHC (HL-LHC) foreseen in 2024. We present here one of the front- end readout options, an ASIC called FATALIC, proposed for the high-luminosity phase LHC upgrade of the ATLAS Tile Calorimeter. Based on a 130 nm CMOS technology, FATALIC performs the complete signal processing, including amplification, shaping and digitisation. We describe the full characterisation of FATALIC and also the Optimal Filtering signal reconstruction method adapted to fully exploit the FATALIC three-range layout. Additionally we present the resolution performance of the whole chain measured using the charge injection system designed for calibration. Finally we discuss the results of the signal reconstruction used on real data collected during a preliminary beam test at CERN.
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ATLAS Calorimeter: Run 2 performance and Phase-II upgrades

ATLAS Calorimeter: Run 2 performance and Phase-II upgrades

The Tile calorimeter [4] is a non-compensating sampling calorimeter where steel is used as ra- diator and scintillating tiles as an active medium. The light from the tiles is read out via fibers and transmitted to photo-multiplier tubes (PMTs). The TileCal readout follows several steps [5]: shap- ing, amplification and digitization of PMT signals. The digitized samples are stored in a pipeline memory and sent to the back-end through optical fibers if a L1 trigger is received. The cell re- sponse can evolve in time because of unstability of PMTs high-voltage, PMTs stress induced by high light flux or optics ageing. Several calibration systems [6] are used to monitor the stability of these elements and provide per channel calibration. The calibration of Tile optic components and PMTs is performed with movable Cesium radioactive gamma source. The Calibration of phototube gains is performed weekly with custom Laser calibration system. With a similar frequency, cali- brations of digital gains and linearities is performed with charge injection system (CIS) integrated on module front-ends. Finally, monitoring of beam conditions and TileCal optics is possible using the so-called integrator system. These systems are used in conjunction to monitor and correct in- stabilities affecting the channels gain like PMT drifts, induced by high instantaneous luminosity or to identify the small fraction of pathological channels as illustrated on Figure 3. Thanks to regular maintenance, the fraction of inefficient cells is kept at a typical level of 1%.
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FATALIC: A novel CMOS front-end readout ASIC for the ATLAS Tile Calorimeter

FATALIC: A novel CMOS front-end readout ASIC for the ATLAS Tile Calorimeter

To ensure stable measurements, TileCal incorporates three calibration systems. A Charge Injection System (CIS) [ 10 ] is used to monitor the response of the FE electronics to known injected charge, but also to derive the conversion factors between the electronic responses and the input charge. Next, the Cesium (Cs) system [ 11 , 12 ] uses a radioactive 137 Cs γ-source, hydraulically circulated through a system of tubes that traverses every row of scintillating tiles. The illumination of the tiles with 0.662 MeV γ produces a uniform, low current signal at the PMT anodes that allows inter-calibration of the detection chains (scintillators, WLS fibres, PMTs, FE electronics). After initial adjustment of the PMT gains, the Cs system is used to measure the small variations among the read-out responses, which are used to derive the necessary calibration coefficients with respect to a unique reference value. Lastly, the laser system [ 13 ] injects light pulses to the PMTs for frequent monitoring of the gains between Cs scans.
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Upgrade of the Laser Calibration System of the Atlas Hadron Calorimeter

Upgrade of the Laser Calibration System of the Atlas Hadron Calorimeter

I. I NTRODUCTION HE Tile Calorimeter (TileCal) [1] is the barrel and endcap hadronic sampling calorimeter of the ATLAS experiment at the CERN LHC. It uses plastic scintillator as active material and low-carbon steel (iron) as absorber. Wavelength shifting fibers connected to the tiles collect the produced light and are readout by photomultiplier tubes (PMTs). PMT response drift is one of the main sources of systematic uncertainty in estimating the calorimeter energy scale: a continuous, percent- level calibration of each cell is then required to maintain the overall performance within 4%.
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The ATLAS hadronic tile calorimeter: from construction toward physics

The ATLAS hadronic tile calorimeter: from construction toward physics

During the equalization procedure, the photo-multiplier gains are adjusted to measure about 1.2 pC/GeV for electrons incident on the inner longitudinal cells of the calorimeter. The precise value of the electromagnetic calibration factor obtained with this procedure is then measured using electron beams of energies ranging from 20 to 180 GeV. The movable table allows one to measure this calibration factor over all the cells, with the beam entering from different angles. The distribution of the calibra- tion factors obtained for various cells, configurations, energies and different modules is plotted in Fig. 6. This distribution gives a mean calibration factor equal to 1.21 pC/GeV and a root mean square equal to 0.04, resulting in a cell-to-cell uniformity of the electromagnetic scale better than 3.5%. In fact, this should only be considered as an upper limit, since finer offline adjustments are still to be applied, depending on the details of the signal re- construction algorithm used. The equalization for the inner cells are checked using muon beams. These studies also show that the uniformity is within a few percent.
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Operation and performance of the ATLAS Tile Calorimeter in Run 1

Operation and performance of the ATLAS Tile Calorimeter in Run 1

b Additional special runs were taken with low integrated luminosity where the number of colliding bunches was increased to 1842 in 2011. using the Gluon String Plasma model, and the Bertini intra-nuclear cascade model is used for lower- energy hadrons [ 21 ]. The input to the digitisation is a collection of hits in the active scintillator material, characterised by the energy, time, and position. The amount of energy deposited in scintillator is divided by the calorimeter sampling fraction to obtain the channel energy [ 22 ]. In the digitisation step, the channel energy in GeV is converted into its equivalent charge using the electromagnetic scale constant (Section 4 ) measured in the beam tests. The charge is subsequently translated into the signal amplitude in ADC counts using the corresponding calibration constant (Section 4.3 ). The amplitude is convolved with the pulse shape and digitised each 25 ns as in real data. The electronic noise is emulated and added to the digitised samples as described in Section 3.2 . Pile-up (i.e. contributions from additional minimum-bias interactions occurring in the same bunch crossing as the hard-scattering collision or in nearby ones), are simulated with Pythia 6 [ 23 ] in 2010–2011 and Pythia 8 [ 24 ] in 2012, and mixed at realistic rates with the hard-scattering process of interest during the digitisation step. Finally, the same reconstruction methods, detailed in Section 3 , as used for the data are applied to the digitised samples of the simulations.
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ATLAS Tile Calorimeter upgrades for HL-LHC

ATLAS Tile Calorimeter upgrades for HL-LHC

8. Calibration Systems The TileCal incorporates three calibration systems to ensure accurate and stable measurements. First, the Charge Injection System (CIS), implemented on each FE card, injects the read- out electronics with known charge, allowing constant monitor- ing but also mapping of the FE response (ADC counts) to the input charge (pC). For the HL-LHC, the CIS will be updated to cover the input range of the new FE electronics. Next, the Cesium (Cs) system allows calibration of the full optical chains (scintillating tiles, WLS fibres, PMTs, FEs) by means of a mov- able 137 Cs γ-source, hydraulicaly circulated through a system
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Test Generation from Recursive Tile Systems

Test Generation from Recursive Tile Systems

This would be the end of this test. 6 Conclusion This paper presented an account on recursive tile systems, a general model of IOLTSs allowing for recursion. It pro- vided algorithms to produce sound, strict and exhaustive test suites, either off-line or on-line. These algorithms enable to employ test purposes (even, for the on-line case) which are a classical way to drive tests towards key properties. The precision of these tests with respect to test purposes has been established. Moreover precise assessments of the complexities of involved operations have been provided.

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Thermal stresses in mortar-tile systems

Thermal stresses in mortar-tile systems

The axial stress of porcelain-mortar composites as a function of volume ratio of the components created by changing temperature were calculated. A 60°C deg temperat[r]

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Tile-Packing Tomography Is NP-hard

Tile-Packing Tomography Is NP-hard

A tile packing of the m × n grid using T — or T -packing, in short, if m and n are understood from context — is a disjoint partial covering of the grid with translated copies of T . Formally a T -packing is defined by a set D of translation vectors such that all translated copies T + (i, j), for all (i, j) ∈ D, are contained in the m × n grid and are pairwise disjoint. We stress here that we do not require the tiles to completely cover the grid — such packings, in the literature, are sometimes called partial tilings. Without loss of generality, throughout the paper we will be assuming that the tile T used in packing is in a canonical position in the upper-left corner of the grid, that is min {x : (x, y) ∈ T } = min {y : (x, y) ∈ T } = 0.
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Test Generation from Recursive Tile Systems

Test Generation from Recursive Tile Systems

6 Conclusion In this paper we have presented recursive tile systems, a general model of IOLTS allowing for recursion. We have provided algorithms to produce sound, strict and exhaustive test suites, either off-line or on- line. These algorithms enable to employ test purposes (even, for the on-line case) which are a classical way to drive tests towards sensitive properties. We have also established the precision of our tests with respect to test purposes. Moreover we have provided precise assessments of the complexities of involved operations. In fact even though our approach enables to model infinite state objects, the algorithms are not significantly more costly.
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A status report on the NRC sealed water calorimeter

A status report on the NRC sealed water calorimeter

The NRC sealed water calorimeter (March, 1999) 15 inum resistor probes, which are used for temperature monitoring, are connected to a remotely controlled scanning system (based on a Keithley 2001 multimeter equipped with a scanner card). The bridge balancing resistor, the lock-in amplier and the multimeter are all con- nected to a PC using a GPIB interface card, thus allowing each to be controlled and read out remotely. The software allows the bridge to be balanced, the characteristics of the lock-in amplier to be changed, the acquisition of data according to a preselected scheme and the calculation of the extrapolation curves and the dose. In addition, the stirrer, valve system and bath can be remotely controlled.
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Robust tile-based texture synthesis using artificial immune system

Robust tile-based texture synthesis using artificial immune system

tile set composed of only eight tiles will draw undesirable repetitive patterns in a large synthesis image. Two methods are proposed in [1] to overcome this artifact. One way is to pick two patches from the input for each original tile. This method doubles the number of the tiles but assumes at least two choices for each tiling step. However, it can only partly eliminate the repetitive patterns in the tiling. We should not neglect the repetitive patterns caused by the central parts of the sample patches. As shown in the rightmost column of Fig. 2(b), the central pattern of the sample patch still pos- sesses an important role in the tiling. To solve this problem, we develop an effective method to directly increase the num- ber of the sample patches which are used to form the in- termediate 𝜔 -tiles, without losing the characteristics of the whole tile set. The other way used in [1] to eliminate repe- tition is to increase the tiles number by using more arrange-
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