3D Crystal Calorimeter: R&D status - HKUST IAS High Energy Physics Conference Jan. 19-21, 2021 - CERN Indico
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3D Crystal Calorimeter: R&D status Yong Liu (Institute of High Energy Physics, CAS), on behalf of the CEPC Calorimeter Working Group HKUST IAS High Energy Physics Conference Jan. 19-21, 2021 Yong Liu (liuyong@ihep.ac.cn)
Motivations (reminder) • Background: future lepton colliders (e.g. CEPC) • Precision measurements with Higgs and Z/W • Why crystal calorimeter? • Homogeneous structure • Optimal intrinsic energy resolution: ~3%/ ۩ ~1% • Energy recovery of electrons: to improve Higgs recoil mass • Corrections to the Bremsstrahlung of electrons • High sensitivity to detect low-energy photons • Capability to trigger single photons • Flavour physics at Z-pole, potentials in search of new physics, … • Fine segmentation • PFA capability for precision measurements of jets 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 2
3D crystal ECAL: past workshops • Ideas firstly proposed: CEPC calorimetry workshop (March 2019) • Follow-up workshop: Mini-workshop on a detector concept with a crystal ECAL • R&D efforts targeting key issues and technical challenges Virtual mini-workshop on a detector concept with a crystal ECAL, July 22-23, 2020, https://indico.ihep.ac.cn/event/11938/ 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 3
R&D efforts targeting key issues and technical challenges • Key issues: performance studies and optimization • Segmentation: in longitudinal and lateral directions • Performance: single particles and jets with PFA -> separation, energy splitting • Impacts from dead materials: upstream tracker, services (cabling, cooling) • Fine timing: e.g. for positioning • Dual-gated or dual-readout techniques (to improve hadronic energy resolution) • Critical technical questions/challenges • Detector unit: crystal options (BGO, PWO, etc.), SiPMs (HPK, NDL, etc.) • Front-end electronics: cornerstone for instrumentation of high-granularity calorimetry • Multi-channel ASIC: high signal-noise ratio, wide dynamic range, continuous working mode, minimal dead time, etc. • Cooling and supporting mechanics design • Calibration schemes and monitoring systems: SiPMs, crystals and ASICs • System integration: scalable detector design (modules), mass assembly, QA/QC 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 4
3D crystal ECAL: 2 major designs Design 1 Design 2 Crystal bars SiPM FE+PCB Cooling + Support Incident particles Incident particles • Long bars: 1×40cm, double-sided readout • Fine segmentation: longitudinal & transverse • Super cell: 40×40cm (24X0 depth) • Single-ended readout with SiPM • Crossed arrangement in adjacent layers • Potentials with PFA • Significant reduction of #channels • Timing at two sides: positioning along bar 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 5
Longitudinal segmentation optimisation Boson Mass Resolution vs #Layer in ECAL PFA Fast Simulation Yuexin Wang (IHEP) Full simulation with SiW ECAL (CDR), by Yukun Shi (USTC) • Full simulation with SiW-ECAL via the benchmark Higgs to 2 gluons • 10 longitudinal layers or more in ECAL can help achieve better than 4% of BMR • Expect small impact from ECAL intrinsic energy resolution (PFA fast simulation) • Guidance for the longitudinal segmentation • Will perform more benchmark studies for crystal ECAL in the CEPC detector simulation 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 6
Longitudinal segmentation: impact from services • Energy resolution with different numbers of sampling layers • 24X0 total depth for crystals: fixed in all scenarios • Used copper to model the inter-layer services (e.g. cooling) • Light materials will be considered for realistic cooling designs: Al, carbon-fibre… Note: energy fluctuations and leakages dominate; impacts of digitization in the next page 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 7
Longitudinal segmentation: with digitisation • Digitisation tool • Photon statistics (crystal and SiPM): reasonably high light yield • Electronics resolution for single photons: taken from the existing ASIC Note: for copper, X0=14.36mm, 1mm Cu = 0.07X0; 6 longitudinal layers in depth: 4X0 crystal/layer for Aluminum, 0.07X0 = 6.2mm (X0=88.97mm) Cu: 0mm/layer Cu: 1mm/layer Cu: 2mm/layer • 0.84X0 copper in total will degrade the stochastic • Require minimum dead materials from mechanics, term to ~2.5% (aim of 3%) cooling, etc. 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 8
3D crystal ECAL: 2 major designs Design 1: short bars Design 2: long bars (current focus) Crystal bars SiPM FE+PCB Cooling + Support Incident particles Incident particles • Advantages • Design optimizations • Fine longitudinal granularity: 24 layers; minimum dead materials • Save #channels: ~15 times less • Transverse: separation power • 3D calorimeter: timing for hit positions for transverse granularity • Longitudinal: impact from dead material • Key issues • Ambiguity: multiple incident particles within one super cell • Neutral pion reconstruction • Separation of nearby showers • Impact on the Jet Energy Resolution (JER) 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 9
Studies on physics requirements: reminder Yuexin Wang (IHEP) • Estimate the multiplicity level of jets: fast simulation • Detailed studies with incident particles (from a jet) hitting the hottest tower 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 10
Jets in Event Display Di-jet events from → • Impressions of topology of EM/hadron showers within jets • Intuitive guidance for the reconstruction development • Current strategy: first studies with (close-by) EM showers, then hadron showers (due to the intrinsic complexity) Multiple gammas and a charged pion Multiple gammas and hadrons 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 11
Reconstruction with 2 incident particles Patterns in event display: 2 photons Shower profiles: 2 photons Longitudinal Profile 3 cm Lateral Profile: timing 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 12
Shower profiles studies in simulation • Key question: how to separate two close-by EM showers • EM shower profiles in 3D with highly granular cells: ongoing studies • Input to the weights for energy splitting Lateral shower profile: 100GeV electrons 1 ( , ) = + 1 − ( ) ( ) Longitudinal profile: 100GeV electrons Distance along radial direction from shower axis (scaled in Moliere radius) 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 13
Separation studies: 2 close-by gammas • Key question: how to separate two close-by EM showers • Benefits of fine granularity • Energy weighted positions (near shower maximum): useful to separate close-by showers 2 gammas separated by 40mm in both X and Y 2 gammas (10 GeV) Side View: fine granularity Dashed lines as directions of incident gammas 20mm distance in X,Y 10mm distance in X,Y 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 14
Latest progress in the new CEPC software Fangyi Guo, Baohua Qi (IHEP) • Crystal calorimeter in CEPCSW (common framework) • Geometry of long crystal bars: implementation in DD4HEP (done) • Digitisation: based on the Geant4 full simulation of a single crystal bar (done) • Reconstruction with single particles and two close-by showers: ongoing Crystal ECAL geometry (barrel) in CEPCSW 400×10×10 mm3 BGO Crystal SiPM muon ESR wrapping SiPM Time stamps of Time stamps of 1st photons detected photons Geant4 full simulation established 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 15
Latest progress in CEPCSW Fangyi Guo (IHEP) • Barrel ECAL implemented Inner radius = 1.8 • BGO crystal bars: 1cm × 1cm × ~40cm Length along beam line = 4.6 • Every 2 layers of vertically intersected bars Total depth = 28 • Readout at two ends • General information BGO: 0 = 1.12 , = 2.23 • 8 identical staves (trapezoids) • Avoid projectile cracks pointing to the IP − • Ideal layout: excluding electronics and mechanics • Gaps identified Gaps in − and z-x planes Minimum Δ = 0.85° • DD4Hep used for geometry construction z− Minimum Δ = 0.89° 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 16
Reconstruction algorithm in CEPCSW Fangyi Guo (IHEP) General flow-chart: work in progress • Sort out information to feed PFA • Used the knowledge on the traditional crystal calorimeter (e.g. BESIII EMC) • Working on the implementation in CEPCSW • Performance check to be done 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 17
Critical questions for 3D crystal ECAL: technical part • Detector unit: crystal options (BGO, PWO, etc.), SiPMs (HPK, NDL, etc.) • Front-end electronics • Cornerstone for successful instrumentation of high-granularity calorimetry: e.g. CALICE prototypes, CMS HGCAL project • Multi-channel ASIC: high signal-noise ratio, wide dynamic range, continuous working mode, minimal dead time, etc. • Cooling and supporting mechanics design • Power consumption (solid inputs from electronics) • Impacts of cooling structure to performance • Calibration schemes and monitoring systems • For SiPMs, crystals and ASICs in the long term • System integration: scalable detector design (modules), mass assembly, QA/QC 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 18
Test stand for crystal-SiPM readout • Key questions • To quantify performance of crystal bars and SiPMs (esp. timing) • Validation of Geant4 full simulation, used for digitization • Infrastructure mostly ready, mechanics for long crystals in production • To test with different SiPMs (types, vendors) and wrapping foils BGO crystals 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 19
First studies NDL-SiPM: new generation Light yield studies NDL-SiPMs Latest prototype 11-3030C-S Parameters NDL 22-1313-15S Breakdown Voltage 27.5 V 19 V Pixel Pitch 10 µm 15 µm Peak PDE 31% @420nm 45% @400nm Pixels 90k 7.4k ~16.6 p.e./MIP with Sensitive Area 3×3 mm² 2.6×2.6mm² 2.6x2.6mm²SiPM MIP response with 11-3030C-S 19.5 p.e./MIP 16.6 p.e./MIP 10x10x45 mm³PWO bar • Tests made for a NDL-SiPM prototype of the latest generation • Many improvements: lower dark-count noise, higher PDE,… • Cosmic muon tests: light yield to be improved • Further tests planned with new NDL-SiPMs PbWO crystal (SIC), • High density: 3×3 mm², 6µm, 245k pixels, PDE~30% (e.g. for BGO) 10x10x45 mm³ • Large area: 6×6 mm², 15µm, 170k pixels, PDE~40% (e.g. for PWO) 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 20
Crystal studies: near-future plans • BGO and PWO crystal samples: varying dimensions, surface treatment • With a major focus on timing performance: e.g. Cherenkov photons Two long BGO bars ready (1×1 ×40 cm³) Short BGO bars with different dimensions and surface treatment PWO crystals (SIC) also ready BGO crystal samples already delivered to IHEP (photo by courtesy of Junfeng Chen, SIC-CAS) 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 21
Front-end electronics for SiPM readout U. Heidelberg, IHEP • ASIC “KLauS”: developed within the CALICE collaboration • Designed by U. Heidelberg (KIP), originally for CALICE AHCAL • Promising candidate: 36-channel, low-power • Excellent S/N ratio: stringently required by high-dynamic SiPMs (small pixels) • Continuous working mode: crucial for circular colliders (no power pulsing) • Need to quantitatively verify its performance and power consumption Wire-bonded Klaus5 chip Klaus5 in BGA 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 22
Klaus5 tests with NDL-SiPM Single photon calibration • NDL-SiPM features: high pixel density (>10k pixels/mm²) and high PDE • Requires high S/N ratio in electronics to resolve single photons, due to the low intrinsic gain of small pixel pitches • Klaus5 tested and proved to be able to resolve the single photons (32fC/p.e.) • Benefits from its high S/N ratio and high resolution Single photon spectrum in 12-bit ADC mode: after corrections NDL-SiPM: nominal gain 2 × 105 with 10µm pixels Single photon spectrum in 10-bit ADC mode: can not be resolved 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 23
Klaus5 dynamic range: charge injection Dynamic Range • Testing of all 36 channels • Different working modes (high gain and low gain) • Dynamic range: ~550pC as the maximum charge (preliminary results) With 5nF capacitor With 1pF capacitor Adapter PCB to inject charge pulses injection to 36 channels ADC after pedestal subtraction ADC after pedestal subtraction (mid High Gain mode) (ultra Low Gain mode) 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 24
Klaus5 dead time measurements Potential for continuous mode Injection Pulses (from an Arbitrary Function Generator) Time Interval X: 200ns/div Y: 100mV/div Pulses from ASIC probe: after preamp + shaper, before ADC Tested at IHEP (at 20 ℃) X: 200ns/div Y: 200mV/div Results also at arXiv:2005.08745 • Varying time interval between 2 injection pulses: 100ns - 10µs • When time interval > 500ns, 100% efficiency of separating the two pulses • Promising feature for 100% duty cycle ( required by circular colliders) Note: tests were made for a single channel; further tests with all 36 channels will be performed 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 25
Summary • 3D crystal ECAL: highly segmented crystals • Aim to achieve optimal energy resolution and PFA performance • Key issues for optimization and technical challenges identified • R&D progress ongoing • Simulation studies on the detector layout with long crystal bars • Geometry and digitization implemented in CEPCSW • Developing reconstruction algorithm, shower studies in Geant4 • Technical developments • SiPMs and crystals • Characterisations of SiPM-dedicated low-power readout ASIC (KLauS) • Welcome broader collaborations: synergies expected • Early R&D stage, many open questions/issues • Work in the common software framework (Gaudi, Key4HEP, DD4HEP, …) 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 26
Backup slides 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 27
Studies on physics requirements Yuexin Wang (IHEP) • Estimate the multiplicity level of jets: fast simulation Hottest 40cm×40cm tower • Mean ~4 particles within the hottest tower Particle E > 0.2GeV 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 28
Shower lateral profile: layer-wise • EM shower lateral profiles • Histograms stored for each longitudinal layer • “Normalised” to the shower maximum • Need to locate the shower axis beforehand • Assign weights for energy splitting in the same bar • Other trials • Tried to use models to fit the curves Average radial energy profiles 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 29
Crystal calorimeter: simulation and digitization Fangyi Guo (IHEP)
• Simulation performed with Geant4 in CEPCSW
• Electromagnetic interactions (current focus)
i
• Digitization for each long crystal bar { − , − } { + , + }
• Readout at two ends: charge Q and time T
• Contribution from the i-th G4step
L
±zi
• Qi± = E0 ∙ exp(− 2
); T±i = T0 + Gaus(z±
i
/v, σT )
LAtt
• For a full bar:
• Q ± = σstep Qi±
• T± = T±k | σki=1 Qi± > ϵQtot
± , ϵ = 5%.
• Considering a simplified scenario: no light
attenuation along bars (LAtt = ∞), Q ± ∝ Etot
2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 30Hit reconstruction in CEPCSW Fangyi Guo (IHEP) • Hit reconstruction: locating hits in 2 crossed bars. ( + ) • Position: ( , , ) 2 • Energy: use energy distributed in crossed bars as a energy fraction: • = × + × , where = , = Σ • MC-Truth level hits: merge G4steps in each 1*1*1 cm3 cube as a truth hit. 1− 2 • Time information: = + . 2 • Match with to veto ghost hits. Reconstruction 2 layers of 1 × 1 × 40 cm3 1 layer of 1 × 1 × 2 3 crystal bars (40+40) 3 crystal cells (40 × 40 ) 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 31
Geant4 full simulation for a single crystal bar Baohua Qi (IHEP) SiPM1 SiPM2 • Information extracted from G4 BGO crystal Muon • Energy deposition: mean ~10 MeV/MIP, determined by crystal thickness • #scintillation photons • #detected photons at either SiPM • Time stamp of each detected photon • T0: shooting of the primary particle (muon) • Included: scintillation time (~hundreds ns), propagation time (a few ns) within the crystal bar • Excluded: timing uncertainties from SiPMs and electronics • Digitization • Timing: Choose the time stamp of the 1st photon detected at each SiPM • #detected photons : proportional to energy deposition 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 32
EM shower studies with crystal bars in Geant4 • Two sets of reconstructed positions • Hits (energy weights) and timing difference • Reconstructed positions from hits • Fine granularity: 10mm • Even layers: Y • Odd layers: X • Reconstructed positions from timing • Complementary to hit positions Gammas • Even layers: X (10 GeV) • Odd layers: Y • Constraints from timing resolution 2 gammas separated by 40mm in both X and Y Side View (one quarter ) 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 33
Studies with PWO crystal bar and NDL-SiPM • Firsts tests with a PWO crystal using cosmics PbWO Crystal • Read out with a 3x3mm²SiPM, 90k pixels (not ideal sensor) SiPM • SiPM designed by Novel Device Lab (NDL) in Bejiing Normal University Bottom Trigger muons #events Example of pre-cut Tyvek paper MIP response: ~20pe/MIP with 3x3mm²SiPM Wrapped with Tyvek paper and ESR PbWO crystal (produced by SIC), 10x10x45 mm³ #p.e. at SiPM NDL-SiPM 3x3mm²with 10um pixels Note: a larger SiPM (e.g. 6x6mm²or larger) can be used for better light collection efficiency 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 34
Geant4 full simulation for a single crystal bar Baohua Qi (IHEP) • To quantify the timing resolution at different hitting positions • To provide input for the digitization model in CEPCSW 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 35
Patterns with jets in Event Display 3. Reconstructed hits with • Patterns for first impression, but still complex… energy information • Need further studies on positioning and energy splitting 2.Reconstructed hits using timing Red: high E → Purple: low E 4. Reconstructed hits with energy > 4MIPs 2021/1/20 Yong Liu (liuyong@ihep.ac.cn) HKUST IAS High Energy Physics Conference 36
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