The ATLAS Tile Calorimeter performanceand its upgrade towards theHigh-Luminosity LHC
Ammara Ahmad(On behalf of the ATLAS Collaboration)
Lomonosov Conference on Elementary Particle Physics
19-25 August 2021

The ATLAS Tile Calorimeter• The Tile Calorimeter (TileCal) is the central hadronic
calorimeter of the ATLAS experiment.
• Composed of layers of steel as absorber medium
interleaved with layers of scintillators as activemedium.
• The TileCal has four longitudinal sections (two centraland two extended barrels), each containing 64modules.

Dimensions• Weight : 2900 T• Length : 12 m
• Diameter: 8.5 m

Basic Principle• Measure light produced by the charged particles inplastic scintillators (tiles).

TileCal purpose• Perform precise measurements of hadrons, jets,
missing transverse energy as well as provide input
signal to Level 1 calorimeter trigger.

20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

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Tile Calorimeter Readout• Every scintillating tile is readout by 2 wavelength
shifting fibres (WLS).
• Fibres go along both sides of every module andare grouped into pseudo-projective geometry cells
in 3 layers.
• TileCal has a total of 5182 cells:• each cell is readout by wavelength shifting
fibres (WLS) and two Photomultiplier tubes(PMTs)• Each module hosts up to 45 PMTs
• Total 9852 Photomultipliers in 256 modules
3865 mmd=0,0D00,10,20,40,3D10,60,5D3D20,80,7

1,00,91,3D4D6D5BC1 BC2 BC3BC4BC5BC61,21,1BC7BC81,4C10B11B9B12B15B14B131,5E11,6A12280 mm
0~A2 A3500A4A51000A6A7A81500 mm

A9A10E2A12 A13A14A15A16E3E4beam axis

• Readout is organised in 4partitions• Barrel divided into 2partitions LBA for η > 0and LBC for η < 0• Extended barrels into 2partitions EBA and EBC

20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

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Calibra4on Systems• Dedicated calibration system at each level of TileCal signal reconstruction to monitor the behaviour ofdifferent detector components.
• The reconstructed energy of each TileCal channel:✦ E[GeV ] = A[ADC] .C1 . C2 . C3 . C4
• A[ADC] the signal amplitude 𝐴 is reconstructed in units of ADC counts using the Optimal Filter algorithm.
• C1 = photoelectrons per GeV (characteristic of scintillator and cell) obtained during test beam.
• C2 = picocoulomb per photoelectron (characteristic of the PMT).
• C3 = volts per picocoulomb (characteristic of the amplifier).
• C4 = ADC counts per volt.

• Cesium System (CCs): Calibrates the entire optic components and the PMTs by providing calibration
constant (CCs) for C2, C3 and C4.

• Laser System(Claser): Calibrates and monitors the PMTs and front-end electronic components used forcollision data in between cesium calibrations by providing calibration constant (Claser) for C2 and C3• Charge Injection System (CIS) (CADC→pC): calibrates the front-end electronics i.e. C3 and C4.
• Minimum Bias System (MB): uses the integrator readout of Physics events to calibrate
the PMT and monitor the full detector response.
Integrator Readout(Cs & Particles)

Particles

CalorimeterTiles

PhotomultiplierTubes
Digital Readout(Laser & Particles)137

Cs source

Laser light

Charge injection (CIS)

20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

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Cesium and Charge Injec4on System• A moveable 137Cs radioactive source passes throughthe calorimeter body few times a year:• the source emits γ− rays with well known energy of662 keV.
• calibrates the entire optical chain i.e., scintillators,fibres and PMTs
• The precision of the Cs calibration in one typical cell is~0.3%• Deviation in the response of cells is caused by the PMT
gain variation and scintillator degradation• By the end of Run 2 the mostirradiated cells in A layer drifted downby 18% while central cells at outer Dlayer drifted up by 2%
Deviation from expected Cs response [%]Cesium System

105ATLAS Preliminary
Tile Calorimeter
Run 2Layer A
Layer BC
Layer D0<5<10<15Jul 15 Jan 16 Jul 16 Dec 16Jul 17 Dec 17 Jul 18 Dec 18
Date [month and year]

Charge injection System• Calibrates the response of ADCs (electronics),
digital gains and linearities in dedicated runs
taken twice per week.
• Simulates physics signals in the TileCal
channels by injecting a known charge into theADC and measuring the electronic response.
• Precision of 0.7%, stability over time of 0.03%
Detector-wide CIS constants averages of all HG ADCs
5
20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

Laser System
Average PMT Drift [%]• Laser light pulses (532 nm) sent to each PMT indedicated runs taken twice per week.
• Pulses also sent during collisions (in empty bunches)to calibrate timing and to study PMT non-linearity.
• PMT response variation evaluated w.r.t last Cesium
scan.
• Precision of the measurement is better than 0.5%.
ATLAS Preliminary
Tile Calorimeter
0.00.1

0.2

6

ATLAS Preliminary
Tile Calorimeter
4Run 2160

Layer A
Layer BC
Layer D

140

Start of pp collisions
Luminosity

120

2

100
080
−260

−440
20

−60.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

eta

01/01
201601/07
2016

31/12
201602/07
2017

31/12
201702/07
2018

Integrated Delivered Luminosity [fb-1]

Evolution of the mean relative response as afunction of time

0Time [dd/mm and year]

1.2D0-.18D1-.19D2-.20D3-.95C7-1.33C8-1.51D5-1.31
C10 -1.58

B1B2 B3 B4B5B6B7B8-1.13 -1.17 -1.18 -1.25 -1.25 -1.19 -1.33 -1.51

B9-1.44E1 B11 B12-2.35 -1.63 -1.56

A1 A2 A3 A4 A5 A6 A7A8A9-1.76 -1.76 -1.79 -1.69 -1.71 -1.91 -1.79 -1.82 -1.86

A10-1.80

A12 A13E2 -1.81-2.11-3.11C1C2C3-1.13 -1.17 -1.18C4C5-1.25 -1.25

C6-1.19E3-3.59<-5.0%-2.5%0%

run 280965, 2015-10-04.

2.5%

>5.0%

1.3

D4-1.51

E4-4.53

D6-.59B13-1.47
A14-1.92

1.4

B14-1.10
A15-1.58

B15-.811.6✦ Larger drifts observed in PMTs of A-cells
and E-cells which are the cells withhighest energy deposits (ie, due todepletion of photocathode, activationof iron)A16-1.36

Mean gain variation as a function eta
and radius of the TileCal PMTs coveringentire 2018 pp collision period

20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

6Minimum Bias Systems and Combined Calibra4ons
Minimum Bias System• Measures the response of Minimum bias events(soft parton interactions during high energy ppcollisions).
• Measures integrated PMT signals over a large
time (~10 ms) by using the same the integrator
readout system as for the Cs system.
• Monitors the full optical chain.

200
5ATLAS Preliminary
Tile Calorimeter

Laser
CesiumLuminosity

Run 2 - A13 cell

1801600140120−510080− 1060

Response variation of A13-cell to Minimum Biasand Laser w.r.t D6 cell during 2017 data taking

Combined Calibrations• Comparison between the cell response toCesium/Minimum Bias events and Laser
measurements• Allows to isolate the relative response ofscintillators and fibres.

40− 1520− 20Integrated Delivered Luminosity [fb-1]

Average Response Deviation [%]• Monitors the instantaneous luminosity andprovides an independent measurement given an
initial calibration (luminosity coefficient).

01/01
2016

01/07
2016

31/12
2016

02/07
2017

31/12
201702/07
2018

0Time [dd/mm and year]• Differences between Cesium/MB and laser
measurements are interpreted as ascintillator aging due to irradiation.
7

20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

Time calibra4on and noise• Time calibration is calculated using jets from pp
collisions and monitored during physics data.
• A precise time calibration is crucial forreconstruction of cell energy.
• Adjusts a digitiser sampling clock to the peakof signal produced by the particle travelingfrom the interaction point.

Noise [MeV]• For Ecell > 4 GeV, resolution is better than 1 ns.
9007006005004003001001020

ATLAS Preliminary
Tile Calorimeter
201512016
2017
2018

0.50

<0.5020406080

100120Noise20001.5

Cell energy [GeV]ATLAS Preliminary
Tile Calorimeters=13 TeV
Data MCEBAA13B13
D6E3800

The mean cell time in jet events as a function ofcell energy
Mean cell time [ns]Time Calibration

30

4050
<µ>

TileCal noise dependence with the average numberof Interactions per bunch crossing• Total noise per cell includes:• Pile-up contribution: multiple interactions duringsame/previous/following bunch crossing events.
• Electronic noise: below 20 MeV. Measured
regularly during dedicated calibration runs withno signal in detector.
• Regions with highest exposure (A-cells, E-cells)
has largest noise

20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

8Performance Studies

dE/<dE>
dx dx

1.6
1.4

ATLAS Preliminary
Tile Calorimeter
Cosmic data 2015

0.8
0.6
0.4
0.2
−2.5

−20.9

ATLAS Preliminary

Data 2015, Low-〈µ〉
Pythia MinBias

Tile Calorimeters = 13 TeV, 1.6 nb-1

0.8
0.7
0.6
0.50.41.1
1.00.9051015202530
p [GeV]• Isolated muons from cosmic rays
are used to study inter calibration ofTile cells and verifies the measured
energy at EM scale.

1−31.0Cosmic- ray Muons

All layers

1.20〈E/p 〉• The TileCal energy response can be probed using
single hadrons and jets.
• The ratio < E/p > of single hadrons is used toevaluate uniformity and linearity during datataking.
• E - calorimeter energy at EM scale• p - track momentum measured by ATLAS
inner detector system.
• < E/p > < 1 : since TileCal is non-compensating
calorimeter• Jets further calibrated to Jet energy scale.

Calorimeter response to single isolated charged hadrons,characterised by < E/p > as a function of p

Data/MCSingle Particle Response

−1.5

−1

−0.5

0
φ [rad]• ~5% non-uniformity in the η and<1% in ϕ response to cosmicmuons.

Ratios of the truncated means of the distributions of the energy deposited in the layer cells by cosmic-ray muons per unit ofpath length dE/dx, obtained using 2015 data as a function of the azimuthal angle ϕ20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

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High-Luminosity LHC upgrade & TileCal
LHC Schedule• High Luminosity upgrade of theLHC in 2027
• increase the instantaneous
luminosity by a factor up to 7.5
provide 4000 fb−1 dataset.
• up to 200 collisions per crossing

LS3 : Phase-2 upgrade
LS2 : Phase-1 upgrade
TileCal during Phase-1 upgrade• Crack scintillators (E3/E4) andtrigger scintillators are replaced• Maintenance of the detectorelectronics done

TileCal plans for Phase-2 upgrade• Full electronics replacement, both on and off detector.
• New modular mechanics : 4 mini-drawers instead of
one super drawer.
• 10% of the PMTs replacement associated to the mostexposed cells.
• New low voltage and high voltage power supplies
systems due to higher radiation requirements.
• Data and power redundancy to improve systemstability

20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

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The new Readout architecture of HL-LHC TileCal

OFF-detector and On-detector electronics replacement• Higher trigger rate (1-4 MHz),• extended data pipelines (35s, moved off detector)• Higher radiation levels, improved reliability and robustness of electronics• Increased bandwidth: 4096 up-links and 2048 down-links
Shaping done in the front-end board located in thePMT block, digitisation on the Mainboard, highspeed communications on the Daughterboard.
20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

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Electronics layout of the HL-LHC TileCal
TileCal Phase-2 upgrade electronics shouldwithstand:• High luminosity environment (~200 collisions perbunch crossing)• Higher ambient radiation
TileCal Phase-2 upgrade electronics should provide:• Low latency• High frequency (40 MHz)• Fully digital input for ATLAS trigger system

Mini-drawer

Mini-Drawer (MD) hosts upto 12channels by means of:• 12 PhotoMultipliers (PMTs) to turnlight pulses to electric signals• 12 Front-End Boards (FEBs) named
FENICS (Front-End ElectroNICS) to
shape and condition the PMTsignals.
• a MainBoard (MB) to continuously
sample and digitise two gains of
the PMT signals. MB also provides
controls and power for the FENICS.
• a DaughterBoard to distribute LHC
synchronized timing, configurationand control to the front-end andcontinuous read-out of the digital
data from all the MB channels tothe Off-detector systems.

20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

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Test Beam measurements• TileCal modules equipped with Phase-II upgrade electronics together with modules
equipped with the legacy system were exposed to different particles and energies inseven test-beam campaigns at SPS during 2015-2018.
• Next campaigns in September 2021!
• Overall good performance has been demonstrated• Agreement between legacy and new electronics in terms of energy calibration.
• Improvement in signal to noise ratio by a factor of ~2.
• Response of each hadron type compatible with previous measurements.
Data to MonteCarlo responsewith hadrons

Data to MonteCarlo responsewith muons

0.8

Simulation

0.2

MC

ATLAS Preliminary
Tile Calorimeter

0.76

A layer

0.74

1.050.72

Ebeam = 100 GeV: (101.28± 0.02) GeV, σ = (4.66 ± 0.01) GeV

0.950.7

MC: (100.98± 0.05) GeV, σ = (4.69 ± 0.02) GeV

0.9
A-2A-3A-4A-5A-6A-7

A-8

A-9Cell

20406080100120

140
E [GeV]

Determine the EM scale of thecalorimeter in pC/GeV and verify
linearity.

0.68

A-10

Verifies the new electronics
performance.
Review and improve the detector
calibration procedure.

Δ E raw

A-1

0.05
00Datam = 0.782 ± 0.004

1.1

MC: (50.58± 0.03) GeV, σ = (3.14 ± 0.02) GeV

0.1Protons

A = -0.522 ± 0.006

1Ebeam = 50 GeV: (50.02± 0.02) GeV, σ = (3.30 ± 0.01) GeV0.15MC

Electron Data

MC: (20.16± 0.02) GeV, σ = (1.71 ± 0.01) GeV〈dE/dl〉t0.25 Ebeam = 20 GeV: (19.72± 0.01) GeV, σ = (1.79 ± 0.01) GeVATLAS Preliminary
Tile Calorimeter

0.78

Tile Calorimeter
Data

ATLAS Preliminary〈dE/dl〉t

Entries normalised to area

REraw

Data to MonteCarlo responsewith electrons

0.04
0.02
0−0.02−0.04

E beam [GeV]

1618202224262830

E beam [GeV]

To validate and improve the modellingof the jets energy characterisation ofthe ATLAS simulation.

20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

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Summary and Conclusions▸ Tile Calorimeter is an important part of ATLAS detector at LHC; contributes to themeasurement of the 4-vectors of jets and missing energy.
▸ Each step of the signal production, from scintillation light to digital signal amplitude
is monitored and calibrated using dedicated calibration systems.
▸ The stability of the absolute energy scale at the cell level was maintained to bebetter than 1% during Run2 data taking.
▸ During ongoing shutdown replacement of crack scintillators and maintenance of
TileCal electronics have been performed.
▸ All TileCal on- and off- detector electronics will be replaced in 2024-2026 during
the ATLAS Phase II upgrade for the HL-LHC era▸ R&D is done, initial tests demonstrate good performance.
▸ Readout resolution and sensitivity are improved slightly.
▸ Many components of the mechanics and front-end electronics have enteredpre-production or production.
20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

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Backup15
20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

Signal Readout and Reconstruc4on▸ PMT signals are shaped and amplified in twogains (low/high ratio 1:64) for high/low signals.
▸ Amplified signal is digitised every 25 ns
by a 10-bit ADC.
▸ Signal amplitude A and time τ determinedfrom a 7 signal samples.
▸A=7aS∑ i ii

1 7
τ=biSi▸A∑i▸ Energy is reconstructed from signal amplitudes using calibration factors.

16
20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad

Calibra4on system17
20th Lomonosov Conference on Elementary Particle Physics | August 2021 | Ammara Ahmad