Application of WaveCatcher & SAMPIC digitizers for the readout of a plastic scintillator based ToF detector

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LAL Orsay, 7/02/2018 1

Application of WaveCatcher & SAMPIC digitizers for the readout of a plastic

scintillator based ToF detector

Alexander Korzenev

University of Geneva, DPNC

on behalf of the Timing Detector group of SHiP

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Beam dump

(target) Active muon filter

_

spectrometer

Hidden Sector spectrometer Vacuum vessel

~150 m

The SHiP Experiment is a new general-purpose fixed target facility at the CERN SPS to search for hidden particles as predicted by a very large number of recently elaborated models of Hidden Sectors which are capable of accommodating dark matter, neutrino oscillations, and the origin of the full baryon asymmetry in the Universe

SHiP experiment in CERN SPS (approval in 2020)

Timing Detector

Purpose: reduction of combinatorial background by tagging particle belonging to a single event

Source of background: products of  and  interactions Detector can be used for PID of few GeV particles

Time resolution < 100 ps Active surface: 5 m x 10 m

Material: plastic scintillator; light readout: array of SiPMs or PMT Trigger-less readout DAQ => SAMPIC based system is proposed

400 GeV

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10 m

5 m

SAMPIC mini-crates

PMT-based readout SiPM-array based readout

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Two options for the readout have been considered in TP

Array of large area SiPMs directly coupled to the bar

plastic scintillator

Advantage of SiPM-array vs PMT

Compactness: 1 cm vs 20 cm Low bias voltage: 50 V vs few kV

High photon detection efficiency: 40% vs 25%

Easily scalable system. In general any SiPM shape can be ordered from a producer company Can be directly attached to a scintillator surface. No need in a complex shape light-guide which provides an adiabatic connection

Can be used in magnetic environment. PMT requires ferromagnetic housing which make the construction bulky

Lower cost

. .

Readout by PMTs which coupled

to the bar via lightguide

plastic scintillator

PMMA lightguide

~20 cm

JINST 12 (2017) P11023 NIM A877(2018)9

~1 cm

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Plastic scintillator counter

–

PVT based material: EJ-200

–

Size: 3 m x 11 cm x 2.5 cm

●

Light collection from two ends by 2'' PMT R13089

●

Objective of study is the time resolution

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as a function of distance w.r.t. phototube

–

WaveCatcher vs SAMPIC

–

Linear interpolation vs fit of the rising edge

Test-beam for a 3 m long bar

and PMT readout

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6 3 m bar, EJ-200

3 m bar, EJ-200 3 m bar, EJ-200 3 m bar, EJ-200

Trigger system (2x2 cm Trigger system (2x2 cm²²)) Trigger system (2x2 cm Trigger system (2x2 cm²²))

Acquisition Module Acquisition Module WAVECATCHER or WAVECATCHER or

SAMPIC SAMPIC

Acquisition Module Acquisition Module WAVECATCHER or WAVECATCHER or

SAMPIC SAMPIC

DAQ notebook DAQ notebook DAQ notebook DAQ notebook

Test-beam at T9 / Est Area CERN PS, June 2016

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DAQ modules: SAMPIC and WAVECATCHER

WAVECATCHER ans SAMPIC ASICs developed by LAL and IRFU teams since 1992 Technology employs a circular buffer based on arrays of switched capacitors (SCA) WAVECATCHER: sampling rate 0.4 – 3.2 GS/s, buffer 1024 cells, commercial ADC for charge, dead time 120 us

SAMPIC: sampling rate 1.6 – 10.2 GS/s buffer 64 cells, on-chip ADC, dead time 1.5 us, all channels are self-triggered (trigger-less readout DAQ)

SAMPIC WAVECATCHER

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Waveform recorded by SAMPIC and WAVECATCHER

Was used in the 3.2 GS/s mode

ToT information (signal width) is provided in new version

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Time measurement w.r.t. reference counter

Uncertainty of the reference counter to be subtracted in quadrature

Signal improves when it is close to the far end because of the reflection

Digital constant fraction discriminator (d-CFD) technique is used

WaveCatcher

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Optimization of the threshold of d-CFD (SAMPIC)

Threshold (fraction) of d-CFD is a subject of optimization Can be calculated on firmware and software levels

14% fraction was used in the analysis

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Time resolution: phenomenological fit

At large distance the resolution is dominated by a contribution from the photon dispersion length => better electronics can not help

Last point does not fit to the simplified formula (light reflection)

Amplitude vs Distance Time resolution vs Distance

A.Blondel et al, NIM A877 (2018) 9

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Time resolution: WaveCatcher vs SAMPIC (1)

Two approaches for the 2-side readout:

Mean time: ~140 ps time resolution on average

Weighted mean: ~100 ps time resolution on average

One gets slightly worse results with SAMPIC at large distances

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Time resolution: WaveCatcher vs SAMPIC (2)

The time resolution is 5% better at the 3 m distance for data taken with WaveCatcher. No difference at smaller distances

Fit of the waveform (8 points of the rising edge) can improve the resolution

one side readout one side readout

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Test-beam with a 1.5 m bar and the readout with an SiPM-array

●

Plastic scintillator counter

–

PVT based material: EJ-200

–

Size: 1.5 m x 6 cm x 1 cm

●

Light collection from two ends by the array of 8 SiPMs (6x6 mm

²

each)

●

Objective of the study is the time resolution

–

as a function of distance w.r.t. the SiPM-array

–

WaveCatcher for DAQ

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. .

Analog signal

Photo-mul tiplier tube

Array of 8 SiPMs 6x6 mm² each

Analog signal

ASIC: preamplifier + analog sum

Digital

Can be used in magnetic environment

PMT requires ferromagnetic housing which make the construction bulky

Comparison to MRPC

No constrains for planarity. Barrel shape detector as an example

Minimum expenses for maintenance

Assembling is easy: no clean room or skilled manpower is required

Low voltage: 50V vs few kV

MUSICR1 Top view (not to scale)

TDC, ADC ...

Voltage divider Scintillator

Light-guide

Scintillator

Advantage of SiPM-array vs PMT Compactness

Low bias voltage ~50 V

High photon detection efficiency ~40%

Easily scalable system

In general any SiPM shape can be ordered from a producer company

Can be directly attached to a scintillator surface no need in a complex shape light-guide which provides an adiabatic connection

TDC, ADC ...

The original idea behind of this work

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Discrete circuit

Readout circuit for a SiPM array

A large SiPM capacitance increases the rise time and width of the signal and worsens the time resolution. A reduction of the capacitance can be achieved by using an independent sensor readout and amplification to isolate the sensor capacitances from each other. Signals are summed up at the end.

ASIC / MUSIC R1

● MUSIC: Multiple Use Sipm IC

● Input: up to 8 SiPM of any size

● SPI control: pole zero cancellation, individual offsets, gain control

● Ongoing development: PCB of a

small size and integration to the DAQ system

● Example of the circuit: front-end of the CTA SST-1M camera

● One operational amplifier per SiPM plus summation stage make PCB bulky

● Weak point: one can not change parameters (individual offsets, pole zero)

example

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Customized external PCB with sensors

– 8 sensors connected either in parallel or in series

– Hamamatsu S13360-6050PE, size 6x6 mm² : pixel pitch 50 m, gain 1.7x10⁶, dark count 2MHz Bias voltage can be set sensor-by-sensor

Front-end and DAQ are presently two separate systems

MUSIC chip to be integrated as an input stage of SAMPIC & WaveCatcher

front side

6 cm6 cm

FPGAFPGA MUSICMUSIC

SiPM supply voltage SiPM supply

voltage USB bridge

Power supply DC 5V

Single-ended output Diff sum output

External PCB with sensors

16+2 ch WaveCatcher

Connector for the external PCB at bottom

back side

1 cm

Sensors and read-out electronics

DAQ

FE

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Bar, EJ-200, 150 x 6 x 1 cm³ Bar, EJ-200, 150 x 6 x 1 cm³

DAQ, WAVECATCHER 16 ch DAQ, WAVECATCHER 16 ch Veto counter Ø = 15 mm

Veto counter Ø = 15 mm

Bias voltage 58 V power suppliers Bias voltage 58 V

power suppliers

Beam triggers, 2x2x2 cm³ Beam triggers, 2x2x2 cm³ MUSIC PCB

MUSIC PCB

Low voltage 5 V power suppliers Low voltage 5 V power suppliers

MUSIC PCB MUSIC PCB

Test-beam at T9 / Est Area CERN PS, June 2017

Holder with 8 SiPMs Holder with 8 SiPMs Holder with 8 SiPMs Holder with 8 SiPMs

C.Betancourt et al, JINST 12(2017) P11023 [1709.08972]

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Results for the time resolution

80 ps time resolution for the 2-side readout

The resolution improves with an increase of the bias voltage Time-walk effect (due to MUSIC) limits the voltage

C.Betancourt et al, JINST 12(2017) P11023 [1709.08972]

80 ps

~5V overvoltage

x=75 cm

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2 requests to developers for improvement

There is only a coincidence option in the trigger logic presently

Request: introduce a veto

(anti-coincidence) option for channels It will allow to use the module together with other DAQ systems/detector

('busy' signal)

Request: introduce an SPI connector to the WaveCatcher module

It will add an ability to control the FE (MUSIC) chip

Update of the DAQ software

SAMPIC SAMPIC

WaveCatcher

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21 PCB with the

MUSIC chip

Plastic scintillator

Light-tight cover

8xSiPM PCB

6 cm x 182 bars = 10 m (0.5 cm overlap)

168 cm x 3 col = 5 m (1 cm overlap)

Purpose of the Timing detector

➔ Reduction of combinatorial background by tagging particle belonging to a single event

➔ Can be used for PID of few GeV particles Time resolution < 100 ps

Downstream of the decay vessel Bar's size 168 cm x 6 cm x 1 cm 546 bars x 2 = 1092 channels 1092 x 8 = 8736 SiPMs

MUSIC for the Front-end

SAMPIC for the DAQ (~1 kHz phys. rate)

Timing Detector in SHiP (year ~2024)

168 cm 6 cm

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Timing Detector in the SHiP experiment

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Array of 1.7 m long plastic scintillator counters

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Light collected by SiPM arrays from both ends of every bar

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Trigger-less DAQ system (software trigger)

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SAMPIC-based DAQ system is a baseline option

Time resolution of long (1.5 m, 3 m) plastic bars have been measured in test-beams in CERN

–

Time resolution is within 100 ps for 2 m long bar (2 ends readout)

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WaveCatcher and SAMPIC shows similar results. Both used at 3.2 GS/s 22 bars prototype to be build by the next summer

Summary

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Backup slides

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In collaboration with

– Barcelona University ICC, Spain / David Gascon

– Humboldt University of Berlin, Germany

– LAL, CNRS/IN2P3, France / Dominique Breton

– Zurich University, Institute of Physics, Switzerland

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Example of application (short term)

T2K-ND280 upgrade proposal to be submitted to CERN SPSC this winter.

The principal goal of the upgrade:

reconstruction of secondaries scattered at 90 deg w.r.t.  beam (600 MeV)

The prototype to be use in test-beams in conjunction with atmospheric and High Pressure TPCs

First test at the end of 2018 at the CERN PS Prototype

year 2018

year 2021

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~5V overvoltage

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to PC

PMT PMT

PMT

PMT PMT

SAMPIC or

WaveCatcher

1 2 3 4

WaveCatcher or SAMPIC module 4 channels for trigger

2 channels for the bar

Time resolution of the reference (cosmic) counters: 

_t

= 40 ps The sigma of the following distribution is measured:

Study of Attenuation Length

Δ t = t

₁

+t

₂

+ t

₃

+ t

₄

4 − t

_5,6

5 6 . . .

beam

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Waveform (1 mip) as a function of distance

WAVECATCHER

Sampling 3.2 GSPS Time window:

1024 x 312 ps = 320 ns

SAMPIC

Sampling 3.2 GSPS Time window:

64 x 312 ps = 20 ns Self-triggering (1-2%

purity)

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30 1.5 m

EJ-200

Spectral sensitivity

PVT based plastic scintillators have been considered: EJ-200 and EJ-204 (commonly used for ToF systems)

Bar dimensions 150 cm x 6 cm x 1 cm, cast surface, edges diamond milled

Readout from both ends

Trade-off between two effects

– Fast scintillator (shorter rise and decay constants) emits light in the NUV region

– Shorter wavelength photons are

stronger affected by absorption in the material

 / 1MeV e- Wavelength Rise time Decay const Att. length

EJ-204 BC-404 10.4k 408 nm 0.7 ns 1.8 ns 1.6 m

EJ-200 BC-408 10k 425 nm 0.9 ns 2.1 ns ~3.8 m

PCB with 8 SiPMs

Plastic scintillator material

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Test-beam in October

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In T10 of East hall CERN PS

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Experimental setup:

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Two 150 cm long bars

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With and without light-guides

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SiPM connection in series (by two) and parallel

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10 m upstream trigger counter for the PID test

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Analysis is ongoing

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All SiPMs connected in parallel Connection by pairs in series

Time resolution with the 150 cm bar

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No difference in precision whether parallel or series (by pairs) connection is used => Bars with 2x8=16 SiPMs per PCB can be designed for ND280

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Time resolution for the 2.3 m long bar is ~100 ps

+58V +116V

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Time-of-flight PID with the trigger

Time-of-flight PID with the 150 cm bar

e 

 _e,^,

p K p

^,

^, _p

p p K

tr ig g er 15 0 cm b ar

p

p p

K

K K

e   _e,^, ^,

^, ^, ,