Siviero F., 2nd year PhD talk, Torino, 5.26.2020

Development of Ultra-Fast Silicon Detectors for the CMS Mip Timing Detector

Outline

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 2

➢ The CMS Mip Timing Detector○ Endcap Timing Layer○ Ultra-Fast Silicon Detectors

➢ UFSD arrays○ Interpad region measurement○ Optimization of the interpad design○ ETL geometry

➢ Timing resolution measurement○ Fermilab beam test○ Torino beta source setup

➢ Future plans

Outline

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 3

➢ The CMS Mip Timing Detector○ Endcap Timing Layer○ Ultra-Fast Silicon Detectors

➢ UFSD arrays○ Interpad region measurement○ Optimization of the interpad design○ ETL geometry

➢ Timing resolution measurement○ Fermilab beam test○ Torino beta source setup

➢ Future plans

The CMS MIP Timing Detector

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 4

● The MIP Timing Detector (MTD) is a new detector being designed for the Phase 2 of the CMS experiment (~ 2026) → will operate during the High-Luminosity phase of the Large Hadron Collider

● MTD will measure the time of passage of Minimum Ionizing Particles (MIPs)

CMS MTD with ETL & BTL indicated

pp collision

The CMS MIP Timing Detector

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 5

● The MIP Timing Detector (MTD) is a new detector being designed for the Phase 2 of the CMS experiment (~ 2026) → will operate during the High-Luminosity phase of the Large Hadron Collider

● MTD will measure the time of passage of Minimum Ionizing Particles (MIPs) ● MTD is divided in 2 sub-detectors: Endcap / Barrel Timing Layers (ETL & BTL) → only ETL covered in

this talk

pp collision

One side of ETL

ETL will be made of 4 disks (2 for each

endcap region)

The CMS MIP Timing Detector

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 6

● The MIP Timing Detector (MTD) is a new detector being designed for the Phase 2 of the CMS experiment (~ 2026) → will operate during the High-Luminosity phase of the Large Hadron Collider

● MTD will measure the time of passage of Minimum Ionizing Particles (MIPs) ● MTD is divided in 2 sub-detectors: Endcap / Barrel Timing Layers (ETL & BTL) → only ETL covered in

this talk

pp collision

One side of ETL

ETL will be made of 4 disks (2 for each

endcap region)

Why does CMS need a Timing detector to operate at High-Luminosity LHC?

Timing

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 7

● Add timing to position measurement → reconstruct particle tracks overlapping in space but with different times of arrival

High-Luminosity LHC● No Timing: Particle tracks overlap and are

mis-reconstructed → loss of efficiency with respect to present CMS

● Timing: maintain present efficiency of the CMS detector with a luminosity 5 times higher

Tracker:only 1 event?

Tracker + Timing Detector:2 overlapped events !

Timing

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 8

● Add timing to position measurement → reconstruct particle tracks overlapping in space but with different times of arrival

High-Luminosity LHC● No Timing: Particle tracks overlap and are

mis-reconstructed → loss of efficiency with respect to present CMS

● Timing: maintain present efficiency of the CMS detector with a luminosity 5 times higher

Tracker:only 1 event?

Tracker + Timing Detector:2 overlapped events !

● Timing detectors to instrument ETL need to satisfy challenging requirements ○ timing resolution: σt ~ 30-50 ps (comparable to state-of-the-art timing detectors)○ Maintain performances for radiation fluences up to Φ ~ 2*1015 neq/cm2 (harsh radiation environment)

Timing

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 9

● Add timing to position measurement → reconstruct particle tracks overlapping in space but with different times of arrival

High-Luminosity LHC● No Timing: Particle tracks overlap and are

mis-reconstructed → loss of efficiency with respect to present CMS

● Timing: maintain present efficiency of the CMS detector with a luminosity 5 times higher

Tracker:only 1 event?

Tracker + Timing Detector:2 overlapped events !

● Timing detectors to instrument ETL need to satisfy challenging requirements ○ timing resolution: σt ~ 30-50 ps (comparable to state-of-the-art timing detectors)○ Maintain performances for radiation fluences up to Φ ~ 2*1015 neq/cm2 (harsh radiation environment)

The innovative detectors that satisfy such requirements were born here in Torino!

Ultra-Fast Silicon Detectors

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 10

● Project born in Torino (2013)● Strong collaboration with Fondazione Bruno Kessler (FBK, Trento)● UFSD are thin (50um) silicon sensors based on the Low-Gain Avalanche Diode (LGAD)

technology

a 4x4 UFSD array on its read-out board

Ultra-Fast Silicon Detectors

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 11

● Project born in Torino (2013)● Strong collaboration with Fondazione Bruno Kessler (FBK, Trento)● UFSD are thin (50um) silicon sensors based on the Low-Gain Avalanche Diode (LGAD)

technology● UFSD are optimal timing detectors, with resolution σt ~ 30ps● UFSD are radiation hard: maintain performances up to Φ ~ 3*1015 neq/cm2

a 4x4 UFSD array on its read-out board

Ultra-Fast Silicon Detectors

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 12

● Project born in Torino (2013)● Strong collaboration with Fondazione Bruno Kessler (FBK, Trento)● UFSD are thin (50um) silicon sensors based on the Low-Gain Avalanche Diode (LGAD)

technology● UFSD are optimal timing detectors, with resolution σt ~ 30ps● UFSD are radiation hard: maintain performances up to Φ ~ 3*1015 neq/cm2

→ Ideal for timing at High Luminosity LHC

a 4x4 UFSD array on its read-out board

Ultra-Fast Silicon Detectors

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 13

● Project born in Torino (2013)● Strong collaboration with Fondazione Bruno Kessler (FBK, Trento)● UFSD are thin (50um) silicon sensors based on the Low-Gain Avalanche Diode (LGAD)

technology● UFSD are optimal timing detectors, with resolution σt ~ 30ps● UFSD are radiation hard: maintain performances up to Φ ~ 3*1015 neq/cm2

→ Ideal for timing at High Luminosity LHC → Thanks to the UFSD project, it will be possible to build the ETL detector!

a 4x4 UFSD array on its read-out board

Ultra-Fast Silicon Detectors

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 14

● Project born in Torino (2013)● Strong collaboration with Fondazione Bruno Kessler (FBK, Trento)● UFSD are thin (50um) silicon sensors based on the Low-Gain Avalanche Diode (LGAD)

technology● UFSD are optimal timing detectors, with resolution σt ~ 30ps● UFSD are radiation hard: maintain performances up to Φ ~ 3*1015 neq/cm2

→ Ideal for timing at High Luminosity LHC → Thanks to the UFSD project, it will be possible to build the ETL detector!

a 4x4 UFSD array on its read-out board

My PhD project focuses on the development of UFSD for ETL: in the following, I will present the main results I got

so far

Outline

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 15

➢ The CMS Mip Timing Detector○ Endcap Timing Layer○ Ultra-Fast Silicon Detectors

➢ UFSD arrays○ Interpad region measurement○ Optimization of the interpad design○ ETL geometry

➢ Timing resolution measurement○ Fermilab beam test○ Torino beta source setup

➢ Future plans

UFSD arrays for ETL

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 16

● ETL disks will be instrumented with UFSD arrays with 16x32 pads

Layout of the final 16x32 UFSD

42 mm

21.2 mm

UFSD arrays for ETL

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 17

● ETL disks will be instrumented with UFSD arrays with 16x32 pads● At the beginning of my PhD, the 1st prototype arrays (mainly 2x2 and 4x4) were produced by FBK

and shipped in Torino○ Before that time, only single pad devices had been tested○ One of my 1st tasks was to characterize them

Layout of the final 16x32 UFSD

42 mm

21.2 mm

One of the 2x2 UFSD prototype array tested

Outline

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 18

➢ The CMS Mip Timing Detector○ Endcap Timing Layer○ Ultra-Fast Silicon Detectors

➢ UFSD arrays○ Interpad region measurement○ Optimization of the interpad design○ ETL geometry

➢ Timing resolution measurement○ Fermilab beam test○ Torino beta source setup

➢ Future plans

UFSD arrays: the interpad region

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 19

● Each pad of a UFSD array is separated from the others by an interpad region, needed to isolate the pads

Neighbouring pads of a UFSD array, with “no-gain” region indicated

interpad region

n++

p+

no p+ layer in that region, that’s why sometimes it’s also called

“no-gain”

Pad 1 Pad 2

UFSD arrays: the interpad region

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 20

● Each pad of a UFSD array is separated from the others by an interpad region, needed to isolate the pads

● The extension of the interpad region determines the “fill factor”:○ fill factor = sensitive area / total area○ Requirement for ETL: ~90% fill factor

● 90% fill factor → interpad region width has to be ≤ 50um

Neighbouring pads of a UFSD array, with “no-gain” region indicated

interpad region

n++

p+

no p+ layer in that region, that’s why sometimes it’s also called

“no-gain”

Pad 1 Pad 2

UFSD arrays: the interpad region

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 21

● Each pad of a UFSD array is separated from the others by an interpad region, needed to isolate the pads

● The extension of the interpad region determines the “fill factor”:○ fill factor = sensitive area / total area○ Requirement for ETL: ~90% fill factor

● 90% fill factor → interpad region width has to be ≤ 50um

→ How can we measure such width?

Neighbouring pads of a UFSD array, with “no-gain” region indicated

interpad region

n++

p+

no p+ layer in that region, that’s why sometimes it’s also called

“no-gain”

Pad 1 Pad 2

TCT setup

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 22

● Interpad region measured with the Transient Current Technique (TCT) setup

○ an IR laser simulates the passage of a ionizing particle in the detector

○ Laser shot position is known with sub-um precision

z

y

x

Laser

you can find the TCT in the Laboratory of Innovative Silicon Detectors (3s, new building)

Interpad region width measurement

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 23

● Get the width by scanning two nearby pads → charge vs position profile

Pad1 Pad2

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 24

● Get the width by scanning two nearby pads → charge vs position profile● Profiles of the 2 pads are s-curves → the width is the distance between the 50% of the profiles

Pad1 Pad2

interpad width

Width is the distance between the 50% of the 2

s-curves

Interpad region width measurement

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 25

● Get the width by scanning two nearby pads → charge vs position profile● Profiles of the 2 pads are s-curves → the width is the distance between the 50% of the profiles● A width of ~40um was measured, proving that UFSD can achieve 90% fill factor as required by ETL

○ This measurement was included in the MTD Technical Design Report

Pad1 Pad2

Width is the distance between the 50% of the 2

s-curves

Interpad region width measurement

interpad width

Outline

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 26

➢ The CMS Mip Timing Detector○ Endcap Timing Layer○ Ultra-Fast Silicon Detectors

➢ UFSD arrays○ Interpad region measurement○ Optimization of the interpad design○ ETL geometry

➢ Timing resolution measurement○ Fermilab beam test○ Torino beta source setup

➢ Future plans

Operation of UFSD arrays

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 27

● The first UFSD arrays could not be operated at the proper voltage, as they suffer from early “breakdown” (large increase of current flowing through the sensor which affects its proper operation)

○ Single-pad sensors worked well

interpad region

Pad 1 Pad 2

Operation of UFSD arrays

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 28

● The first UFSD arrays could not be operated at the proper voltage, as they suffer from early “breakdown” (large increase of current flowing through the sensor which affects its proper operation)

○ Single-pad sensors worked well● Only difference between array and single-pad is the interpad region

(not present in single-pads)

Implants defining the interpad

region design

Pad 1 Pad 2

interpad region

Operation of UFSD arrays

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 29

● The first UFSD arrays could not be operated at the proper voltage, as they suffer from early “breakdown” (large increase of current flowing through the sensor which affects its proper operation)

○ Single-pad sensors worked well● Only difference between array and single-pad is the interpad region

(not present in single-pads)○ We suspected the interpad design to be responsible for early

“breakdown”

Pad 1 Pad 2

interpad region

Implants defining the interpad region design

Operation of UFSD arrays

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 30

● The first UFSD arrays could not be operated at the proper voltage, as they suffer from early “breakdown” (large increase of current flowing through the sensor which affects its proper operation)

○ Single-pad sensors worked well● Only difference between array and single-pad is the interpad region

(not present in single-pads)○ We suspected the interpad design to be responsible for early

“breakdown”● We tried to prove that with 2 innovative tools:

○ the TCT setup (already described)○ the “ORCA 2” CCD camera manufactured by Hamamatsu

Photonics (available in our lab)

“ORCA 2” camera mounted on

a microscope

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 31

TCT measurement of interpad region

Pad1

200V

● Exploiting the high-precision of the TCT setup:○ x-y map of the charge collected by the sensor (colored axis)

UFSD design prones to early “breakdown”:we focused the TCT on the central region,

where 4 pads join

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 32

Pad1

Pad1 Pad1

200V

260V250V

● Exploiting the high-precision of the TCT setup:○ x-y map of the charge collected by the sensor (colored axis)

● We observed a large increase of charge in pads’ corners with voltage (look at the pink circles), causing in turn an increase of current flowing through the sensor→ Proof that early breakdown occurs in the interpad region (pads’ corners are too sharp)

TCT measurement of interpad region

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 33

● 2nd measurement performed with a different tool: the “ORCA 2” camera○ Designed to perform Ultra-Low Light Imaging

250 V 260 V200 V

“ORCA 2” camera

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 34

● 2nd measurement performed with a different tool: the “ORCA 2” camera○ Designed to perform Ultra-Low Light Imaging

● Focusing the camera on the area where 4 pads join

250 V 260 V200 V

Same UFSD array measured with the TCT: the camera is focused on the region where 4 pads join

“ORCA 2” camera

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 35

● 2nd measurement performed with a different tool: the “ORCA 2” camera○ Designed to perform Ultra-Low Light Imaging

● Focusing the camera on the area where 4 pads join: observation of a strong emission of visible photons (yellowish region)

250 V 260 V200 V

photons emitted in the interpad (corners, in particular)

“ORCA 2” camera

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 36

● 2nd measurement performed with a different tool: the “ORCA 2” camera○ Designed to perform Ultra-Low Light Imaging

● Focusing the camera on the area where 4 pads join: observation of a strong emission of visible photons (yellowish region) → due to the high current flowing through

○ cannot be done by a normal CCD camera, since the amount of light is very low

250 V 260 V200 V

“ORCA 2” camera

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 37

● 2nd measurement performed with a different tool: the “ORCA 2” camera○ Designed to perform Ultra-Low Light Imaging

● Focusing the camera on the area where 4 pads join: observation of a strong emission of visible photons (yellowish region) → due to the high current flowing through

○ cannot be done by a normal CCD camera, since the amount of light is very low

250 V 260 V200 V

This measurement confirmed that the interpad design caused the early “breakdown”

“ORCA 2” camera

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 38

Optimization of interpad design

● Using the results of our study, FBK processed a new production of UFSD arrays exploring different interpad designs

● An extensive measurement campaign of the new arrays led to the definition of an improved design, preventing the early “breakdown” issue

● See my talk at TREDI 2020 for a complete description of the measurement campaign

UFSD array from the latest production, without early “breakdown”: regions with

strong emission of photons are not present, as expected

260 V

Outline

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 39

➢ The CMS Mip Timing Detector○ Endcap Timing Layer○ Ultra-Fast Silicon Detectors

➢ UFSD arrays○ Interpad region measurement○ Optimization of the interpad design○ ETL geometry

➢ Timing resolution measurement○ Fermilab beam test○ Torino beta source setup

➢ Future plans

The ETL Geometry

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 40

● Using our R&D studies on the sensors, combined with studies by other ETL groups (electronics, mechanical engineering), it was possible to design the “ETL module”:

○ building block of the whole detector○ Made of two 16x32 UFSD + Front-end electronics +

Support structures

Exploded view of ETL module ¼ ETL disk: grey squares are the ETL modules

The ETL Geometry - 2

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 41

● Once the ETL module was designed, I became responsible for the implementation of the ETL detector within the Simulation software of CMS

The ETL Geometry - 2

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 42

● Once the ETL module was designed, I became responsible for the implementation of the ETL detector within the Simulation software of CMS

● I firstly implemented the ETL module, then I combined many modules to build the final detector

ETL module implemented in the simulation software (UFSD arrays in red)

2 disks composing one side of the ETL detector, as implemented in

the simulation software

The ETL Geometry - 2

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 43

● Once the ETL module was designed, I became responsible for the implementation of the ETL detector within the Simulation software of CMS

● I firstly implemented the ETL module, then I combined many modules to build the final detector → thanks to this work, since January 2020 it is possible to perform simulations of the CMS experiment using the timing information provided by ETL

● Results presented at the 2020 CMS Timing Days

ETL module implemented in the simulation software (UFSD arrays in red)

2 disks composing one side of the ETL detector, as implemented in

the simulation software

Outline

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 44

➢ The CMS Mip Timing Detector○ Endcap Timing Layer○ Ultra-Fast Silicon Detectors

➢ UFSD arrays○ Interpad region measurement○ Optimization of the interpad design○ ETL geometry

➢ Timing resolution measurement○ Fermilab beam test○ Torino beta source setup

➢ Future plans

Fermilab beam test

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 45

● Timing resolution is the key measurement on UFSD● The 1st measurement was performed during a beam test

at Fermilab (Chicago, USA) using 120 GeV/c protons● Ideal facility to test our sensors:

○ Precise tracker → reconstruct hit position○ Climate chamber → perform measurement at -30°C

(LHC condition)○ Fully automated data acquisition → huge amount of

good data taken in only 2 weeks

ETL rack @ Fermilab Test Beam Facility

Fermilab beam test: Timing resolution

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 46

● ETL requirements: σ = 30-50 ps for radiation fluences up to Φ ~ 1015 neq/cm2

Fermilab beam test: Timing resolution

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 47

● ETL requirements: σ = 30-50 ps for radiation fluences up to Φ ~ 1015 neq/cm2

● UFSDs irradiated at different fluences have been measured → they all reached at least 50ps timing resolution

Radiation levels of tested sensors

even the most irradiated sensor reached 50ps

Fermilab beam test: Timing resolution

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 48

● ETL requirements: σ = 30-50 ps for radiation fluences up to Φ ~ 1015 neq/cm2

● UFSDs irradiated at different fluences have been measured → they all reached at least 50ps timing resolution

→ UFSD fulfill the requirements for ETL!

Radiation levels of tested sensors

even the most irradiated sensor reached 50ps

Details on results were presented here

Torino beta setup

● We built and commissioned our own setup last summer → 1st of this kind in our department

● Mounted in the medical physics lab (old building)

● Data acquisition fully automated● Fast data analysis using a dedicated

script

Lecroy 9404HD 40 Gs/s

Dark box

CAEN HV

PC for DAQ & Analysis

LV

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 49

“In-house” setup to measure timing resolution without beam test

A result from our beta setup: Timing resolution

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 50

● Measurement performed on a single-pad 1x3 mm2

● σUFSD = 33ps

Sensor used for this measurement

resolution of 2 UFSDs, divide by sqrt(2) to get σUFSD

A result from our beta setup: Timing resolution

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 51

● Measurement performed on a single-pad 1x3 mm2

● σUFSD = 33ps ● Our homemade setup reached the best timing resolution

achievable with UFSD

Sensor used for this measurement

resolution of 2 UFSDs, divide by sqrt(2) to get σUFSD

A result from our beta setup: Timing resolution

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 52

● Measurement performed on a single-pad 1x3 mm2

● σUFSD = 33ps ● Our homemade setup reached the best timing resolution

achievable with UFSD○ Torino will be able to fully characterize the final ETL sensors!

→ only a few other institutes will be able to do that

Sensor used for this measurement

resolution of 2 UFSDs, divide by sqrt(2) to get σUFSD

Outline

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 53

➢ The CMS Mip Timing Detector○ Endcap Timing Layer○ Ultra-Fast Silicon Detectors

➢ UFSD arrays○ Interpad region measurement○ Optimization of the interpad design○ ETL geometry

➢ Timing resolution measurement○ Fermilab beam test○ Torino beta source setup

➢ Future plans

What’s next

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 54

● The 16x32 UFSD prototypes will be delivered by FBK this summer○ First laboratory tests of large arrays will come soon○ Beam test at Fermilab next winter to measure them already scheduled○ then, the final production of ETL sensors will start

● In parallel, we will make the first tests using a front-end chip that is being developed at Fermilab

What’s next

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 55

● The 16x32 pads UFSD prototypes will be delivered by FBK this summer○ First laboratory tests of large arrays will come soon○ Beam test at Fermilab next winter to measure them already scheduled○ then, the final production of ETL sensors will start

● In parallel, we will make the first tests using a front-end chip that is being developed at Fermilab● Improvement of beta setup:

○ Climate chamber (just arrived) → measurements at -30°C○ Read-out 16 channel using a digitizer (instead of a 4ch oscilloscope) → test large sensors

What’s next

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 56

● The 16x32 pads UFSD prototypes will be delivered by FBK this summer○ First laboratory tests of large arrays will come soon○ Beam test at Fermilab next winter to measure them already scheduled○ then, the final production of ETL sensors will start

● In parallel, we will make the first tests using a front-end chip that is being developed at Fermilab● Improvement of beta setup:

○ Climate chamber (just arrived) → measurements at -30°C○ Read-out 16 channel using a digitizer (instead of a 4ch oscilloscope) → test large sensors

● We’re working on the medical Linac of our department to set up our own beam test facility

Summary & Outlook

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 57

● UFSD have been chosen by CMS to instrument the MTD Endcap Timing Layer○ born in Torino○ 30ps timing resolution → comparable to state-of-the-art timing detectors○ A factor 10 more radiation-hard than other precise timing detectors

Summary & Outlook

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 58

● UFSD have been chosen by CMS to instrument the MTD Endcap Timing Layer○ born in Torino○ 30ps timing resolution → comparable to state-of-the-art timing detectors○ A factor 10 more radiation-hard than other precise timing detectors

● My PhD activities so far:○ Measurement of the interpad region width to assess “fill-factor” of UFSD arrays○ Measurement campaign that led to the definition of the optimal design of UFSD arrays○ Implementation of the ETL geometry within the CMS Simulation software○ We proved that UFSD meet the ETL requirements during a beam test @ Fermilab○ We built and commissioned a beta source setup (comprising DAQ and data analysis) in our

department, proving that we can fully characterize ETL sensors

Summary & Outlook

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 59

● UFSD have been chosen by CMS to instrument the MTD Endcap Timing Layer○ born in Torino○ 30ps timing resolution → comparable to state-of-the-art timing detectors○ A factor 10 more radiation-hard than other precise timing detectors

● My PhD activities so far:○ Measurement of the interpad region width to assess “fill-factor” of UFSD arrays○ Measurement campaign that led to the definition of the optimal design of UFSD arrays○ Implementation of the ETL geometry within the CMS Simulation software○ We proved that UFSD meet the ETL requirements during a beam test @ Fermilab○ We built and commissioned a beta source setup (comprising DAQ and data analysis) in our

department, proving that we can fully characterize ETL sensors● In the future, we will define the final UFSD design, further improve our beta setup and perform the first beam

tests right here in Torino

Thank You!

BACKUP

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 61

Towards High-Luminosity LHC

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 62

● 2024-2026: major upgrades of the Large Hadron Collider (LHC) → High-Luminosity LHC (HL-LHC)● A factor 5-7 increase in number of concurrent proton-proton collisions (“pile-up events”) :

○ spatial overlaps of tracks produced in the collisions○ the present CMS detectors cannot resolve so many tracks → upgrade to Phase 2 of CMS

Why so special?

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 63

● LGAD: p+ layer implanted under n++ electrode generating an high electric field → multiplication of

charges produced by the passage of an ionizing particle → Internal gain

● Gain: Improve Signal-to-Noise ratio● 50um-thick: Fast signal (short signal rise-time)

Ingredients for precise timing

● Thanks to their design + LGAD technology, UFSD maintain their performances after large radiation doses → other precise timing detectors (SiPM, for instance) are a factor 10 less radiation resistant

UFSD vs traditional silicon sensor:

the p+ layer locally generates an high E field,

allowing charge multiplication

Fermilab beam test: Timing resolution

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 64

UFSD cold box:tUFSD

Trigger:provides reference timestamp

ttrigger

proton beam

tracker

● Timing resolution: σ of the gaussian distribution Δt = tUFSD - tTrigger

● Trigger is a scintillator with few ps resolution → negligible contribution to the total resolution

Siviero F., 2nd year PhD talk, Torino, 5.26.2020 65

Fermilab beam test: large-area sensor

● 1st large-area UFSD ever tested at a beam test● The sensor operated as expected for several hours● 100% hit efficiency on the whole active area

efficiency drops in no-gain regions

Torino beta setup - 2● Specific structure for alignment● Trigger placed below the sensor to measure

timing resolution ( σ of the gaussian distribution Δt)

● Fast read-out board designed by University of Santa Cruz (USA)

DUT

TriggerBeta trajectory

66Siviero F., 2nd year PhD talk, Torino, 5.26.2020

Fast read-out board