Large pixel SiPMs for single photon detection in the new LHCb large - PowerPoint PPT Presentation

PIXEL2018 International workshop on Semiconductor Pixel Detectors for Particles and Imaging Large pixel SiPMs for single photon detection in the new LHCb large area scintillating fibre tracker Olivier Girard , Maria Elena Stramaglia, Guido Haefeli Ecole polytechnique fédérale de Lausanne (EPFL), Switzerland On behalf of LHCb SciFi collaboration

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 2 Outline Context • LHCb and the upgrade • The SciFi technology Silicon photomultipliers • Choices for LHCb Characterisation of radiation effects • Random noise • Detection of low photon signals • Photon detection efficiency B. Leverington Module assembly on frame

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 3 LHCb SciFi tracker 3 Tracking station 12 detection layers ✘ Straw tubes + silicon? 320 m 2 total area Read-out box SiPMs, cooling, electronics 2× 2.5 m ✓ SciFi tracker mirrors SciFi module fibre mats + mirrors 2× 3 m

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 3 LHCb SciFi tracker 3 Tracking station 12 detection layers ✘ Straw tubes + silicon? 320 m 2 total area Read-out box SiPMs, cooling, electronics 2× 2.5 m ✓ SciFi tracker mirrors SciFi module fibre mats + mirrors 2× 3 m

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 3 LHCb SciFi tracker 3 Tracking station 12 detection layers ✘ Straw tubes + silicon? 320 m 2 total area Read-out box SiPMs, cooling, electronics 2× 2.5 m ✓ SciFi tracker mirrors SciFi module fibre mats + mirrors • Fibres: 11’000 km • SiPMs: 0.2 m 2 , 490k channels 2× 3 m

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 4 Light detection – challenge VELO upgrade = 220 μ m Collected Signal = O(10k) e - X Noise = O(200) e - X/X 0 = 0.23% on 1 pixel X = 1.35 mm Injection at mirror D V=3.5V Signal = X/X 0 = 0.41% Energy deposit × scint. light yield × light capture × light attenuation × photon det. eff.

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 4 Light detection – challenge VELO upgrade = 220 μ m Collected Signal = O(10k) e - X Noise = O(200) e - X/X 0 = 0.23% on 1 pixel X = 1.35 mm Injection at mirror D V=3.5V Signal = X/X 0 = 0.41% Energy deposit → Amplification × scint. light yield needed! × light capture × light attenuation × photon det. eff.

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 4 Light detection – challenge VELO upgrade = 220 μ m Collected Signal = O(10k) e - X Noise = O(200) e - X/X 0 = 0.23% on 1 pixel X = 1.35 mm Injection at mirror D V=3.5V Signal = X/X 0 = 0.41% Energy deposit → Amplification × scint. light yield needed! × light capture × light attenuation × photon det. eff. Noise Collected from 2-3 ch. = 2-3 × 104 pixels

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 4 Light detection – challenge VELO upgrade = 220 μ m Collected Signal = O(10k) e - X Noise = O(200) e - X/X 0 = 0.23% on 1 pixel X = 1.35 mm Injection at mirror D V=3.5V Signal = X/X 0 = 0.41% Energy deposit → Amplification × scint. light yield needed! × light capture × light attenuation Fibres: max 30kGy Radiation × photon det. eff. SiPMs: 5·10 11 n eq /cm 2 environment Noise Collected from 2-3 ch. = 2-3 × 104 pixels

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 5 SiPM for the SciFi tracker Customised SiPM array produced by Hamamatsu (S13552) 32.54 × 1.625 mm 2 Design choices:  Large pixels  Opaque trenches  Adjusted quenching resistor

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 6 Dark count rate and effect of irradiation Random noise – Dark count rate (DCR) • Thermally-generated e-h pair ~100 kHz/mm 2 • Increased by irradiation 30’000 ×  Overlap of pulses (high signals)  Cooling ( ÷ 2 per 10°C)  Short integration time  Clustering 0.41mm 2 channel T=-40°C 4.5V D V=3.5V neutrons 3.5V protons 2.5V

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 7 Sensitivity for low-light signals after irradiation SPIROC Low light spectrum D V=2V • Gain measurement T=-40°C • Compensation for effects in the electronics due to the high dark current D V=3.5V T=-40°C PACIFIC Non-irradiated -4% 6∙10 11 n eq /cm 2 -7% -11%

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 8 Light yield with irradiated SiPMs Electron injection in the fibres • Comparative photon detection efficiency Noise “Light yield” Measurement • Correction for DCR contribution SPIROC • 5% measurement uncertainty D V=3.5V • Light yield variation observed: T=-40°C ±4% up to 6∙ 10 11 n eq /cm 2

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 9 Conclusion & outlook SciFi technology • Cost-efficient solution to cover large surface with good spatial resolution (<100 μ m for 2.5 m, better for small size) • Particularly interesting for applications with no radiations • Can provide timing information ~0.5 ns How can we make the SciFi technology radiation-harder? Photodetector: • SiPMs: improve structure and implementation • Use a pixel sensor with amplification for visible light detection? • Improve light collection: microlenses Fibre: • Improve scintillation light yield in the green, reduce attenuation and improve radiation hardness • Light transport outside the radiation environment with clear interface with optical fibre?

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 15 Backup LHCb & the SciFi tracker

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 16 LHCb upgrade Timescale during LS2 in 2019-2020 Goal extend physics reach with:  Higher luminosity (5 ×)  Better trigger efficiency for a wide range of decay channels  Design for 50 fb -1 integrated luminosity Run1+2 (2011-now): 7 fb -1 Downstream tracker is replaced: Detector changes silicon strips (IT) + straw tubes (OT) →  40 MHz read-out + flexible trigger (in scintillating fibre (SciFi) tracker software) modules  Detector hardware: cope with  High hit detection efficiency increased occupancy and read-out rate  Fine granularity  Low mass (homogenous distribution)

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 17 SciFi tracker Tracking station 4 detection layers (stereo angles 0, ± 5°) o Total area of 320 m 2 Read-out box 5·10 11 n eq /cm 2 o 11’000 km fibres ( Ø 250 SiPMs, cooling, µ m) arranged in mats electronics SciFi module fibre mats + 6 layers mirrors 2× 2.5 m 1.35 mm o 4000 multi-channel mirror s Silicon PhotoMultipliers 30 kGy (SiPMs) for a total of 524k read-out channels 2× 3 m

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 18 Radiation environment Total ionising dose at the end of the lifetime of the SciFi tracker [Gy] SiPMs F 50 to 100 Gy Simulation of the cumulated radiation after the + neutrons i design integrated luminosity (50 fb -1 ) b r e 30 kGy s Fibres: SiPMs  In the central region: 30 kGy M1 replaced by polyethylene SiPMs: Calorimeter with 5% boron (10-20cm thick)  Dominated by neutrons SciFi tracker  Neutron shielding between SciFi tracker and calorimeter  Fluence expected: 5 ·10 11 n eq /cm 2 SiPMs Effect on the performance:  Reduced transparency of the fibres "𝑥𝑗𝑢𝑖 𝑡𝑖𝑗𝑓𝑚𝑒𝑗𝑜𝑕"  Increase in SiPM noise Neutron fluence: ratio "𝑜𝑝 𝑡𝑖𝑗𝑓𝑚𝑒𝑗𝑜𝑕"

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 19 SciFi tracker Kuraray SCSF-78MJ blue emitting fibre Cold box cross-section FE electronics connection Cold-warm feed-through Challenges and design choices: Cold box  Signal time spread: scintillator isolation decay time and light transport 3D-printed Ti  Attenuation length: ~ size cooling pipe  Large size: flatness and SiP mechanical stability with low M Vacuum insulated material budget Fibres distribution pipes  Radiation environment (fibres and 3D-printed SiPMs): detection efficiency Ti cooling  SiPM cooling (-40°C) pipe Enclosure

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 20 Integration of SiPMs in LHCb SciFi Cold- Vacuum insula-  SiPM gluing to cooling pipe and optical box ted connections alignment Cooling pipe  3D printed Ti cooling pipe with alignment pins, thermal expansion and isolation are the main challenges  Integration into a vapour tight cooling Multi-channel SiPM enclosure, vacuum insulated cooling pipes Enclosure with feed-through  Cooling with single phase liquid chiller (Novec or C 6 F 14 )  Front-end electronics with custom read-out chip (Pacific)  Zero suppression (clusterisation) based on 3 threshold sampling  Optical transmission, zero suppression on FPGA and GBT transmission  Common off detector electronics TELL40

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 21 IEEE NSS MIC 2017

O. Girard – PIXEL2018, Academia Sinica, Taipei, Taïwan – 14 December 2018 22 Backup SiPM