Modeling Radiation Damage to Pixel Sensors in the ATLAS Detector M. - PowerPoint PPT Presentation

PIXEL2018 - Academia Sinica, Taipei Modeling Radiation Damage to Pixel Sensors in the ATLAS Detector M. Bomben, LPNHE & UPD – Paris on behalf of the ATLAS collaboration M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 1

Outline • Introduction • ATLAS Radiation Damage Digitizer Goals • Digitizer: implementation strategy and ingredients • Validation • Predictions • Conclusion & Outlook M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 2

The CERN Large Hadron Collider (LHC) CERN LHC is the largest and most powerful particle accelerator ever built It provides proton-proton collisions at energies up to √s = 13 TeV LHC design luminosity was 1x10 34 cm -2 s -1 Design value has been widely exceeded! M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 3

The CERN Large Hadron Collider (LHC) CERN LHC is the largest and most powerful particle accelerator ever built It provides proton-proton collisions at energies up to √s = 13 TeV LHC design luminosity was 1x10 34 cm -2 s -1 Design value has been widely exceeded! Large dataset integrated over first 2 LHC Runs: > 180 fb -1 M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 4

The CERN Large Hadron Collider (LHC) CERN LHC is the largest and most powerful particle accelerator ever built It provides proton-proton collisions at energies up to √s = 13 TeV ] ] -1 2 / cm Run 2 Delivered Luminosity [fb ATLAS Preliminary 10 150 Updated Oct. 25, 2018 eq n IBL 14 8 B-layer Total Fluence at z = 0 [10 Layer 1 LHC design luminosity was 1x10 34 cm -2 s -1 100 6 Layer 2 Design value has been widely exceeded! 4 50 2 Large fluence integrated over first 2 LHC Runs: > 9x10 14 n eq /cm 2 by the innermost pixel layer 0 0 0 200 400 600 800 1000 1200 Days Since Start of Run 2 M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 5

ATLAS Inner Detector 1 . 4 m 4 Pixel barrel layers 3 Outermost: 250 µm thick 50x400 µm 2 pitch Innermost layer: IBL Inserted in Run2 200 µm thick 50x250 µm 2 pitch M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 6

ATLAS Pixel Detector 1 . 4 m 4 Pixel barrel layers r e h e w r y v e e 3 Outermost: o r s s e n n s n - o n - e l p i x r n a l a P e d u s e a r p o n - n - D 3 250 µm thick e l o v n r e h e w B L I i n η * h i g h a t u t b *outside tracking volume 50x400 µm 2 pitch Innermost layer: IBL Inserted in Run2 200 µm thick 50x250 µm 2 pitch M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 7

Pixel sensors: radiation damage effects Significant decrease of dE/dx and ] or <cluster size> [pixels] • ATLAS Pixel Preliminary 2 cluster size for IBL Data2016 Data 2017 Data 2018 1.8 IBL Similar effect for B-Layer • 1.6 It was necessary to increase the • 1.4 bias voltage and adjust threshold to 1.2 mitigate the negative trend 2 <dE/dx> cm 1 Cluster size φ Occupancy decreasing too • -1 <dE/dx> [MeV g Cluster size z 0.8 HV 80 → 150 V 0.6 HV=80(150) V HV=350 V HV=400 V - - - Thr=2.5ke Thr=2.5ke Thr=2ke - - - ToT=8BCs@16ke ToT=8BCs@16ke ToT=10BCs@16ke 0.4 0 20 40 60 80 100 120 140 160 180 -1 Run-2 Delivered Luminosity [fb ] 0 0 2 2 4 4 6 6 8 8 10 10 14 14 2 2 [1 [1 10 10 n n /cm /cm ] ] Φ Φ × × eq eq M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 8

Pixel Radiation Damage Digitizer* Goals Include all this in ATLAS MonteCarlo Charge carriers will drift toward the collecting electrode due to electric field , which is deformed by radiation damage . Their path will be deflected by magnetic field ( Lorentz angle ) and diffusion . Due to radiation damage they can be trapped and induce/screen a fraction of their charge ( Ramo potential ). Total induced charge is then *Digitization happens after simulated charge deposition digitized and clustered. and before space point reconstruction M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 9

Pixel Radiation Damage Digitizer Goals Include all this in ATLAS MonteCarlo Now ready! Charge carriers will drift toward the collecting electrode due to electric field , which is deformed by radiation damage . Their path will be deflected by magnetic field ( Lorentz angle ) and diffusion . Due to radiation damage they can be trapped and induce/screen a fraction of their charge ( Ramo potential ). Total induced charge is then digitized and clustered. M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 10

Implementation Strategy fluence initial charge Start location trapping constant thermal Lorentz diffusion angle time E-field travelled final charge location final Ramo depth per condition potential per geometry induced End charge per e/h M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 11

Ingredients: fluence and trapping time Fluence prediction taken from FLUKA & Pythia ] (z=0) [%] -1 ATLAS Preliminary /fb 7 120 2 s = 13 TeV /cm FLUKA prediction validated with leakage Φ eq 6 Si 1 MeV n (z) / 100 current and Hamburg model* simulation Φ Relative data fluence 5 80 12 Absolute fluence [10 Ø 15% difference in the central region 4 60 3 Insertable B-layer (IBL) 40 Predicted by Pythia (A2) + FLUKA Trapping constants from literature**: 2 Predicted by Pythia (A3) + FLUKA Predicted by Pythia (A3) + Geant4 20 Predicted by Pythia (A3) + Geant4 (n + p + π only) 1 Ø β e = (4.5±1.5)x10 -16 cm 2 /ns Extracted from Hamburg Model + Leakage Currents 0 0 30 20 10 0 10 20 30 − − − Distance along stave [cm] Ø β h = (6.5±1.5)x10 -16 cm 2 /ns ** ATLAS pixel coll. , JINST 3 (2008) P07007 G. Kramberger et al., Nucl. Instrum. Meth. A481 (2002) 297 O. Krasel et al., IEEE Trans. on Nucl. Sci. 51 (2004) 3055. G. Alimonti et al., ATL-INDET-2003-014 (2003) * M. Moll, DESY-THESIS-1999-040 M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 12

Ingredients: electric field (planar sensors) Radiation damage induced defects deform the electric field distribution in the bulk We use TCAD simulation tools to make predictions of electric field in the bulk A 2 trap model due to CMS collaborators* has been used with Silvaco tools** 20000 E. Field [V/cm] Model chosen because: 18000 V bias = 150 V Φ = 0 14 2 = 1 10 n /cm Φ × eq 16000 developed on n-on-n pixels 14 2 • = 2 10 n /cm Φ × eq 14 2 = 5 10 n /cm Φ × 14000 eq irradiated at CERN w/ 24 GeV/c p • 12000 built on testbeam data • 10000 predicts type inversion at right fluence • 8000 6000 4000 Main feature: double peak electric field 2000 0 0 50 100 150 200 Bulk Depth [ m] µ *V. Chiochia et al., Nucl. Instr. and Meth A 568 (2006) 51-55 ** https://www.silvaco.com/products/tcad.html M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 13

Ingredients: electric field mod. uncertainties E A E D σ A,D & σ D σ A N A N D Fluence T T e h h TCAD radiation damage ( 10 14 cm − 3 ) ( 10 14 cm − 3 ) ( 10 − 15 cm 2 ) ( 10 − 15 cm 2 ) (eV) (eV) model parameters come ( 10 14 n eq / cm 2 ) ± 0 . 4% ± 0 . 4% ± 10% ± 10% ± 10% ± 10% 3.6 5 1 with no uncertainties E C -0.52eV E V +0.48eV 6.60 1.65 6.8 10 2 5 14 34 [V/cm] [V/cm] So we had to explore the 14000 14000 Nominal Nominal z 12000 z 12000 E 14 2 E 14 2 Φ = 1 × 10 n /cm Φ = 1 × 10 n /cm sensitivity of electric field on eq eq g A + 10% energy + 0.4% int 10000 10000 V = 80 V V = 80 V A bias g - 10% bias energy - 0.4% int each defect parameter: 8000 8000 6000 6000 4000 4000 concentration 2000 2000 • 0 0 20 40 60 80 100 120 140 160 180 20 40 60 80 100 120 140 160 180 energy • Bulk Depth [ µ m] Bulk Depth [ µ m] [V/cm] [V/cm] 14000 14000 electron and hole capture • Nominal Nominal z 12000 z 12000 E 14 2 E 14 2 Φ = 1 × 10 n /cm Φ = 1 × 10 n /cm eq eq + 10% + 10% σ σ cross sections e h 10000 10000 V = 80 V V = 80 V bias σ - 10% bias σ - 10% e h 8000 8000 6000 6000 Trends are compatible with 4000 4000 2000 2000 expectations 0 0 20 40 60 80 100 120 140 160 180 20 40 60 80 100 120 140 160 180 Bulk Depth [ m] Bulk Depth [ m] µ µ M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 14

Ingredients: annealing Annealing not modeled in TCAD 140 [V] ATLAS Preliminary depl IBL 120 Effective correction to TCAD: rescale defects V Hamburg Model Simulation concentration in TCAD to match the average 100 Simulation Uncertainty (constant) space charge concentration Data with Bias Voltage Scan 80 predicted by Hamburg Model 60 Hamburg model predictions based on bias 40 voltage scans 20 9 × 10 ] 3 0 Space Charge [e/cm 4000 02/07/2015 01/01/2016 01/07/2016 31/12/2016 Date 2000 14 2 = 2 10 n /cm Φ × eq 0 V = 80 V bias 2000 − IBL stayed cold most of the time 4000 − è small correction Chiochia − 6000 Hamburg More important effect for B-Layer TCAD with eff. annealing 8000 − 20 40 60 80 100 120 140 160 180 Bulk Depth [ m] µ M. Bomben - Pixel 2018, 10-14 December, Academia Sinica, Taipei, Taiwan 15