Fast Timing for Collider Detectors

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1 Fast Timing for Collider Detectors Chris Tully (Princeton University) CERN Academic Training Lectures (2/3) 11 May 2017

2 Outline Detector technologies with fast timing capabilities Readout methods for fast timing layers and calorimeters Fast Timing for Collider Detectors - CERN Academic Training Program 2

3 Time-of-Flight Position Emission Tomography (TOF-PET) LYSO crystals (thick) LOR = Line-of-Response Standard conversion 1ps 300 microns SiPM photodetectors Fast Timing for Collider Detectors - CERN Academic Training Program 3

Silicon Photo-Multiplier (SiPM) Silicon photomultipliers (SiPMs) L < 1um Structure and principles of operation (briefly) Al electrode R quench Al electrode V out Q tot = 2Q Joint R&D effort from ND

common substrate and operated in Geiger mode Each cell has its own quenching resistor (from 100kΩ to several MΩ) Common bias is applied to all cells (~10-20% over breakdown voltage) Cells fire

4 Silicon Photo-Multiplier (SiPM) Silicon photomultipliers (SiPMs) L < 1um Structure and principles of operation (briefly) Al electrode R quench Al electrode V out Q tot = 2Q Joint R&D effort from ND 2-4µ 300µ p-si substrate p-epi layer n + /p junctions SiO 2 +Si 3 N 4 R q Q Q GM-APD substrate V bias > V BD (EDIT-2011, CERN) SiPM is an array of small cells (SPADs) connected in parallel on a common substrate and operated in Geiger mode Each cell has its own quenching resistor (from 100kΩ to several MΩ) Common bias is applied to all cells (~10-20% over breakdown voltage) Cells fire independently The output signal is a sum of signals produced by individual cells For small light pulses (N g <<N pixels ) SiPM works as an analog photon detector The very first metall-resitor-smiconductor APD (MRS APD) proposed in 1989 by A. Gasanov, V. Golovin, Fast Timing for Collider Detectors - CERN Academic Training Program 4

5 Detection Chain Crystal SiPM electronics g Dt q t kth pe = Dt + t k ph + t transit + t SPTR + t TDC Conversion depth Scintillation process Transit time jitter Single photon time spread TDC conversion time Random deletion 1 Absorption Self-absorption Random deletion 2 SiPM PDE Unwanted pulses 1 DCR, cross talk Afterpulses Unwanted pulses 2 DCR P. Lecoq Fast Timing for Collider Detectors - CERN Academic Training Program 5

FBK, 55%PDE 511 KeV 150GeV muons 5MeV deposited 2x2mm 2

6 S. Gundacker et al., CERN TOFPET MIP Timing Layer LSO:Ce,0.4%Ca 2x2x5mm 3, meltmount coupled to 3x3mm 2 NUV SiPM from FBK, 55%PDE 511 KeV 150GeV muons 5MeV deposited 2x2mm 2 section Fast Timing for Collider Detectors - CERN Academic Training Program 6

7 Time Jitter V voltage noise band of signal timing jitter arising from voltage noise timing jitter is much smaller for faster rise-time TIME RESOLUTION V Time resolution expected to improve with signal amplitude: time Fast Timing for Collider Detectors - CERN Academic Training Program 7

8 Detecting a MIP with SiPM Readout (low light) MIP signal with ~60 p.e. in plastic scintilltor (CMS HCAL HE) Landau Peak at ~3000 fc 1 fc ~ 6250 e HCPSS 2016 Calorimetry Lecture 1 8/17/16 8

9 Detecting a MIP with SiPM Readout Pedestal electronic noise RMS ~3 fc Single pe peak (single pixel gain) ~50 fc each 50 * 6250 / (p)e Gain=3*10 5 (3000 fc/50 fc)/5 MeV 3pe/MeV Landau Peak at ~3000 fc 1 fc ~ 6250 e MIP S/N ~ 1000? Not really, single pe firing dominates instrument noise MIP S/N ~ 150 N~ DCR (Dark Count Rate) and the DCR increases with radiation dose) HCPSS 2016 Calorimetry Lecture 1 8/17/16 9

10 MIP S/N in the first ~200ps Test beam data of unirradiated devices show good agreement with simulation Fast Timing for Collider Detectors - CERN Academic Training Program 10

11 Larger, thinner crystals Optimizition for ~25ps Fast Timing for Collider Detectors - CERN Academic Training Program 11

12 Crystal Pulse Reconstruction Lots of signal, AC coupling possible Acts like capacitive divider for S and N (N~ DCR) Electronics sees low input capacitance if a shunt capacitor is used TDC (or waveform digitizer) of Fast Comparator Output Fast Timing for Collider Detectors - CERN Academic Training Program 12

13 } SiPMs: increase of dark current and dark rate Dark Count Rate (DCR) drops with Temperature } Acceptable in the barrel: small-pixels SiPMs (production ready FBK/HPK) } Total power consumption from 291 k (5x5 mm 2 ) SiPMs: } ~7 kw (~12 kw) at -29 o C (-23 o C) A.Heering et al. 16 THIS TECHNNOLOGY IS NOT VIABLE IN THE ENDCAPS Fast Timing for Collider Detectors - CERN Academic Training Program 13

14 End-of-life S/N is an optimization of crystal size, SiPM PDE and DCR growth from irradiation (at low temp) Fast Timing for Collider Detectors - CERN Academic Training Program 14

15 Silicon Sensors with Gain Favorable technology in the push for higher radiation hardness, as is needed at high eta and within calorimeters Important parameters of silicon: 100micron/ns (when drift velocity saturated at ~30kV/mm E-field) and 73 e-h pair per micron for MIP MIP timing of ~30ps requires high S/N and uniform charge collection largely driven by E-field geometry and Landau fluctuations Fast Timing for Collider Detectors - CERN Academic Training Program 15

Silicon Timing: Deep-Deplet Different Gain/E-Field Geometries are under study (RD50): Reach-Through and Deep-Depleted

suppliers (CNM, FBK, HPK) Silicon is biased, image charge read out Gain layer and drift region overlap Mesh serves to

ps resolution achieved on 8x8mm2 nonirradiated device No conclusive results yet for irradiated devices Fast Timing for

16 Silicon Timing: Deep-Deplet Different Gain/E-Field Geometries are under study (RD50): Reach-Through and Deep-Depleted Deep depleted APD read out through capacitatively coupled mesh Low-Gain Avalanche Detectors (LGAD) gain O(10) 3 suppliers (CNM, FBK, HPK) Silicon is biased, image charge read out Gain layer and drift region overlap Mesh serves to stabilize E-field shape over large area for good performance over whole device Operates at high gain / high voltage 20 ps resolution achieved on 8x8mm2 nonirradiated device No conclusive results yet for irradiated devices Fast Timing for Collider Detectors - CERN Academic Training Program 16 Deep-Depleted Avalanche Photo-Diodes (DD-APD) gain O(500) 1 supplier (RMD)

17 E-Field Geometries are very different Fast Timing for Collider Detectors - CERN Academic Training Program 17

18 Uniform E-Field DD-APD achieves uniform E-field with a mesh Placed on Top Surface LGAD achieves uniform E-field with a wide implant Wide implant Narrow implant y [mm] Ew [1/mm] y [mm] Ew [1/mm] x [mm] b) x [mm] Fast Timing for Collider Detectors - CERN Academic Training Program 18

Transient Current Technique Time [ns] LGAD signal looks like a current that flows across a capacitor for the time it takes the deposited charge to traverse the thickness of the device takes roughly 1.

19 Transient Current Technique Time [ns] LGAD signal looks like a current that flows across a capacitor for the time it takes the deposited charge to traverse the thickness of the device takes roughly 1.4ns to traverse 140 microns LGAD now prefers 50 micron thickness DD-APD is coming from a ~40 micron avalanche region and is narrower Fast Timing for Collider Detectors - CERN Academic Training Program 19

20 Electronics Readout Schemes Current Amplifier (BBA) S Current Amplitude [mv] t r V th Time I in C d Charge Sensitive Amplifier (CSA) Time [ns] Vth Comparator Sensor Pre-amplifier Time measuring circuit H. Sadrozinski, A. Seiden, N. Cartiglia 4-Dimensional Tracking with Ultra-Fast Silicon Detectors Fast Timing for Collider Detectors - CERN Academic Training Program 20

Landau fluctuations in LGAD geometry Non uniform charge deposition along the track This is a physical limit to time resolution: beat it with thin detectors and low comparator threshold.

21 Landau fluctuations in LGAD geometry Non uniform charge deposition along the track This is a physical limit to time resolution: beat it with thin detectors and low comparator threshold. 300 micron thick Nicolo Cartiglia, INFN, Torino - ETL review 2/03/17 Vth [mv]! Set the comparator threshold as low as you can! Use thin sensors 50 micron thick Fast Timing for Collider Detectors - CERN Academic Training Program 21 40

22 LGAD timing The resolution correct with gain 50 micron value thickness icolo Cartiglia, INFN, Torino - ETL review 2/03/17 Charge non uniformity: ~ constant with gain Jitter term: scales with gain (dv/dt) H. Sadrozinski, TREDI 2017 Our measurements show that the ETL target time resolution of ~ 30 ps can be reached with gain ~ The time resolution is determined by charge non-uniformity The working point will be determined by the interplay with the electronics Fast Timing for Collider Detectors - CERN Academic Training Program 22

23 Sensor R&D LGAD sensor fill factor wafer-level process Cartiglia, INFN, Torino - ETL review 2/03/17 Sensor fill factor: what is the minimum distance between pads? High fields require special terminations at the edge of each pad Currently ~ 30 micron! Goal: ~ 20 micron Fast Timing for Collider Detectors - CERN Academic Training Program 23

24 LGAD gain layer doping sensitivity high Nicolo Cartiglia, INFN, Torino - ETL review 2/03/17 Gain vs gain layer doping Unfortunately, the gain is very sensitive to the doping level Small decrease in doping: 10% Large decrease in gain: 80% 27 Fast Timing for Collider Detectors - CERN Academic Training Program 24

25 Radiation issue: Initial acceptor removal Radiation dose effects on p-doping This term indicates the removal of the initially-present p-doping. For UFSD this is particularly problematic as it removes the gain layer Irradiation! Defects! Boron becomes interstitial Nicolo Cartiglia, INFN, Torino - ETL review 2/03/17 B B B The boron doping is still there, only it has been moved into a different position and it does not contribute to the doping profile, it is inactive Fast Timing for Collider Detectors - CERN Academic Training Program 25 29

26 Initial acceptor removal: mitigation Gallium doping and Carbonated Boron Gallium doping: Irradiation! defects! Gallium has lower diffusivity Ga Ga Ga Nicolo Cartiglia, INFN, Torino - ETL review 2/03/17 Ga Ga Ga Ga Ga Carbonated Boron: Irradiation! defects! Carbon fills interstitial states C C C C C C C C C C C C C C C C C Fast Timing for Collider Detectors - CERN Academic Training Program 26 C B Ga 30

27 Maintaining gain at high fluence Collected charge as a function of bias voltage in a 50-micron thick sensor for different fluences Collected Charge [e] 100,000 80,000 60,000 40,000 Increasing fluence Fluence: 5e14 neq/cm2, Active doping = 63% Fluence: 3e14 neq/cm2, Active doping = 76% Fluence: 1e14 neq/cm2, Active doping = 91% Unirradiated Charges needed for good timing measurement 20, Bias [V] Fast Timing for Collider Detectors - CERN Academic Training Program 27

28 Time resolution for irradiated LGAD maximum gain with neutron fluence H. Sadrozinski, TREDI 2017 J. Lange, Torino - ETL review 2/03/17 W5 2e15 n/cm 2 W3, W7 6e14 n/cm 2 ~ 42 ps W5 pre-rad Fast Timing for Collider Detectors - CERN Academic Training Program 28

29 Summary Lecture 2 Fast timing is possible with both light and charge collection technologies Dimensions matter a lot! Fast timing in colliders is possible because we have the technical capability to tile sq. meters of surface with small, thin tiles (1-100 mm 2 ) and have electronics with an analog bandwidth and low noise thresholds on a high S/N MIP Radiation fluence is a fierce foe as usual. More on this tomorrow. Fast Timing for Collider Detectors - CERN Academic Training Program 29

30 Backup Fast Timing for Collider Detectors - CERN Academic Training Program 30

31 Effect of the scintillation photon arrival at the photo detector we refer to as Optical Transit Time Spread. Calorimeter timing measurements Experimental program to explore ultimate timing resolution, in particular the impact of the optical transit time spread. x x EM shower propagation snapshot γ MIP Timing Layer γ Scintillation light propagation c S < c t 1 t 2 Time evolution of a shower from photon in CMS ECAL PbWO crystal (25 cm long). 100 GeV γ 23 cm [ns] 3 Fast Timing for Collider Detectors - CERN Academic Training Program 31 Adi Bornheim, Calor 2016, Calorimeter Precision Timing 3

Long Crystal timing measurements CMS ECAL current timing performance -t 2 )[ns] 1 γ(t Timing resolution of CM S ECAL better then 1 ns was not foreseen in the original design, despite this: :

32 Long Crystal timing measurements CMS ECAL current timing performance -t 2 )[ns] 1 γ(t Timing resolution of CM S ECAL better then 1 ns was not foreseen in the original design, despite this: : excellent timing resolution already achieved in 2012 (LHC TeV). 1 Z æ ee events. CMS Preliminary - Run1 E in EB [GeV] γ(t) = A N eff /γ n EB Z study γ N = 33.2 ± 2.0 ns 2C C = ± ns Timing resolution estimated from fit to: t channel 1 t channel 2. Take the two most energetic channel for each electron cluster A eff /γ n Simone Pigazzini Precision timing with PbWO crystals CALOR / 12 Fast Timing for Collider Detectors - CERN Academic Training Program 32

33 Improvements CMS ECAL current expected timing with performance clock distribution T iming resolution improves for channels of the same cluster. Further gain when considering channels that belongs to the same readout unit. Channelsin the same shower but different readout units. Channelsin the same shower and same readout units. Fast Timing for Collider Detectors Simone Pigazzini - CERN Academic Training Program Precision timing with PbWO crystals CALOR / 12 33

34 Less CMS shaping ECALand electronics higher foranalog HL-LHC bandwidth Improvements: Noise from APD leakage current. : increased by long exposure to radiation. Allow higher trigger rates. Mitigat e pileup from previous and following bunch crossings. Mitigat e signal contamination from concurrent interactions in the same bunch crossing (through timing). Test beam: digitized APD signal Different solut ions are under evaluat ion. Current ECAL electronics with faster shaping time could satisfy the requirements. : Shorter signal : Larger Amplitude/ noise : Better timing resolution. Simone Pigazzini Precision timing with PbWO crystals CALOR / 12 Fast Timing for Collider Detectors - CERN Academic Training Program 34

35 TIA Filter ADC Digital output Rg March 2nd 2017 MD - MIP timing layer review 7 Fast Timing for Collider Detectors - CERN Academic Training Program 35

~ 300 kv/cm High field obtained by (1) adding an extra doping layer (2) by external VBias High field Gain layer The LGAD

36 LGAD Avalanche Region is localized Low Gain Avalanche Detectors (LGADs) Nicolo Cartiglia, INFN, Torino - ETL review 2/03/17 The LGAD concept has been proposed and manufactured first by CNM (National Center for Micro-electronics, Barcelona) Field needed: E ~ 300 kv/cm High field obtained by (1) adding an extra doping layer (2) by external VBias High field Gain layer The LGAD project has been developed initially by the RD50 collaboration Fast Timing for Collider Detectors - CERN Academic Training Program 36 3

37 Light generation in scintillators 5d Rare Earth 4f Fast Timing for Collider Detectors - CERN Academic Training Program 37

Hot intraband luminescence Wide emission spectrum from UV to IR Ultrafast emission in the ps range Independant of temperature Independant of defects Absolute Quantum Yield W hn /W phonon = 10-8

38 Hot intraband luminescence Wide emission spectrum from UV to IR Ultrafast emission in the ps range Independant of temperature Independant of defects Absolute Quantum Yield W hn /W phonon = 10-8 /( ) 10-3 to 10-4 ph/eh pair Higher yield if structures or dips in CB? Interesting to look at CeF3 More details in SCINT2013 paper TNS M. Korzhik, P. Lecoq, A. Vasil ev Fast Timing for Collider Detectors - CERN Academic Training Program 38

A timing layer for charge particles in CMS

A timing layer for charge particles in CMS Is it possible to build a tracker with concurrent excellent time and position resolution? Barrel Can we provide in one, or in combination Endcap Timing resolution