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AUTO-TRIGGERABLE PHOTODETECTORS FULLY READOUT ON ETHERNET :

APPLICATION FOR HIGH ENERGY PHYSICS AND MEDICAL IMAGING

Guillaume MoretR. Barbier – S. Katsanevas – G. Largeron – J. Marteau

S. Gardien – C. Girerd

Institut de Physique Nucléaire de LyonIN2P3/CNRS - UCB Lyon 1

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Outline

• The smart sensor principle :• multi-pixel photo-detector (HPD, MaPMT, APD)• auto-triggerable electronics based on VA-TA systems (IDE AS)• e-DAQ : a Data AcQuisition system fully based on ethernet

• Tests on the DEP 61 pixels HPD• Tests on the Hamamatsu 64 pixels MaPMT

• Applications in HEP : the example of OPERA• R&D in medical imaging : microPET

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The « smart sensor » principle

ADC

FPGA

ETHERNETCONTROLLER

Photodetector Front-End IC Front-End SequencerEthernet Controller

preamp slow shaper

fast shaper

• Multi-pixels photodetector : MaPMT’s or HPD’s• Auto-triggerable electronics (VA-TA from IDEAS)

with multiplexed charge output• Front-end sequencer + ethernet controller (BFOOT, Etrax)• IP address for each ethernet controller

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Auto triggerable electronic : VA - TA

• VA-TA from IDEAS• Auto triggerable• Low noise and high gain

(VA32c-TA32cg)• 2 shapers

• TA ! trigger :75 ns peak time, Ored trigger output

• VA ! charge meas.2 µs peak time

• Gain measurement:TA 16 mV/fCVA 120 mV/fC

• Noise measurement:TA 2.5 mV (900 e- ENC) VA 10 mV (500 e- ENC)

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Functions of the sensor" All generic functions available via the web :

• Control of Front-End chips• Sequence the readout (FPGA) : ADC readout• Download biases• Slow controls e.g DAC’s for HV, start calibrations,…• Time synchronization, time stamp of the events (@ 50 MHz)• Send data through Ethernet network (ethernet controller)

" User access by any application able to open a socket on the network :

• Any WEB browser • LabVIEW interface through Ethernet• C program interface

" Each F.E. element (e.g. photodetector) is a node on the network

" Data send with TCP/IP protocols

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A basic model

1) First prototype using an Ethernet Controller from Agilent (BFOOT 11501)

ADC

ADC

Configdevice

APEX20K200

FPGA

32

8

DAC

Altera

RS2

32

IEEE 1451.2 NCAP

Ethernet Controler

Agilent5 Mbit/s

link

TDC MTD135Lecroy

RJ45

80233Seeq RJ45

250 MH

z

Ana

log

Inpu

tA

nalo

gO

utpu

tD

igita

l I/O

GPS PPS

Triggers

ADC

FPGA

Ethernet Controller

2) Second generation : Etrax from Axis• data rate : 100 Mbits / s• Etrax : small processor running Linux• 27 mm2 and 500 mW power consumption• Memory available (8 MB ROM, 2 MB RAM)• OPERA : ~ 1050 cards

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Access through a web browser

destination

cycle duration

protocol

First step :Login on the ethernet controller WEB home page via http command

Second step :define the parameters of the ethernet controller (R/Ospeed, com. port…)All the commands sent via : • http command (slow control,

monitoring)• TCP/IP protocol (R/O)

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Access through LABVIEW2 steps : • configuration (thresholds, gain, biases adjustement)• measurement (start/stop acquisition)

2 phases :# configuration# measurement

address of the ethernet controller

command line

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Configuration• Example of GUI under LabVIEW :

• Electronics (VA-TA) configuration & monitoring (gain, pedestals…)• Start /Stop data acquisition (TA mode / ext. Trigger mode,

mono channel / multi channels)

Measurementmodes

TA configuration

command line

Type of data transferred

Configuration step

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VA configuration

" 4 measurement modes :• control of the VA pedestals• control of the VA peaking time• oscilloscope mode with calibrated pulse• acquisition mode (data streaming to the DAQ PC)

• external / auto-trigger mode• record the timestamps ofeach kind of triggers

• counters of triggersin a time window

"On-line tuning :• trigger type (external or TA)• hold delay (in ns)• ADC frequency• # channel (in case of single channel readout)

VA pulse

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HPD characterization - I

• HPD, 61 pixels from DEP• VA32c-TA32cg electronics for readout• HV : -5 (p.e. resolution) ! -10 kV & bias : 60 V

Uniformity:Measurement with dark current spectragain w.r.t. pixels > 98%

Cross talk:Blue LED + clear fiberssignal on a neighbour pixel < 2%

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HPD characterization - II

Linearity:gain variation w.r.t. high voltagep.e. resolution:

1 %

Pedestals variation < 1%High stability with high voltage

Very good resolution Up to 6 p.e.

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MaPMT characterization - I

• PM, 64 pixels from Hamamatsu • Light on all the pixels (light diffuser)• Gain distribution w.r.t. pixels position

<α> ~ 10σ ~ 0.4

<β> ~ 4683σ ~ 291

• Gain variation w.r.t. high voltage• G = β . (HV)α

• α variation : 4%• β variation : 6%

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MaPMT characterization - II• Single photo-electron resolution• Fit function for the resolution :

• pedestal : gaussian + exponential• gauss (position) modulated by poisson

<N p.e. > = 0.15 <N p.e. > = 2

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MaPMT characterization - III

• Trigger efficiency measurement :• acquisition with LED in external trigger mode• recording of the TA trigger • coincidence in time of external & TA triggers• ratio of the 2 histograms

• Result : 100% trigger efficiency at 7.5mV/150mV = 0.05 p.e.

• Dark current measurement :• 64 channels allowed• result : ~3 Hz / pixel

Trigger efficiency

VA signalExt trigger

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Ethernet & OPERA

• Neutrino oscillation project between CERN and Gran-Sasso (Italy)• Search for tau neutrino appearance on a muon neutrino beam• Tau detection realized with emulsion sheets (packed into bricks)• Detector (~ 2 kt) : plastic scintillators & RPC & drift tubes

νµ

ντ ?

Signal : 30 neutrino events by day⇒ low data rate (mainly dark current

of the photodetector), ⇒ possibility to use

a DAQ on Ethernet⇒ “smart sensor” principle

No accurate time information between the beam and the detector (to trig the DAQ)⇒ auto triggerable DAQ is vital (allows also non beam physics studies)

OPERA DAQ : autoOPERA DAQ : auto triggerabletriggerable & fully on Ethernet& fully on Ethernet

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Tests on a full readout chain

• Scintillator (liquid/plastic) - HPD-VATA - ethernet DAQ• Tests : cosmic rays setup, beam tests (CERN, T7)• Very easy to calibrate, manipulate and use• The full chain was succesfully tested and characterized

HPD

Ethernet card

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HPD & OPERA : dream or reality ?

• HPD + auto triggerable electronics + e-DAQ : fully validated

• Advantages of HPD ’s :• linearity ~ 99%• uniformity ~ 98%• excellent resolution, ratio S/N ~ 6 • low cross talk (< 2%)

• Drawbacks of HPD ’s :• high dark current > 1 kHz / pixel• low gain ⇒ high gain for the electronic chain• low fill factor, too large transverse dimensions⇒ HPD ’s on the corner but too much light loss in the

WLS+clear fibers+connectors system

• OPERA acquisition chain :• MaPMT, 64 pixels• auto triggerable electronics (« home made » chips by IN2P3)• ethernet acquisition (distributed on 1000 nodes for target & spectrometer)

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Ethernet in medical applications

• The idea : application of the smart sensor principle to a smalldistributed system using multi-pixels photodetector, the microPET

• microPET : PET for small animals (mice, rats)• Requirements : spatial resolution ~2 mm & sensitivity ~3%• Principle : detection of two 511 keV gammas “back to back”

⇒ energy reconstruction required (scintillating crystals)⇒ sorting in time of the events + search of coincidences within time window

• Reconstruction of tracks (LOR : Line of Response)

• Detection modules in ring geometry • Module : crystals of LSO & LuAP (crystal clear collaboration) +

MaPMT (64 pixels) + auto-triggerable electronics (VA-TA) + e-DAQ

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First crystal tests

• Global architecture for the test :• 1 PM with 9 connected pixels• LSO or LuAP cristals• Cs or Na sources•Energy resolution ~20%

LSOLSO MaPMTMaPMTCristals

« matrix »Cristals

« matrix »

Photo electric peak

Sum of all the pixelsNa source

One pixelCs source

Photo electric peak

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Conclusions

• “Smart sensor” is a validated concept :• possibility to drive acquisition (slow control AND direct R/O ofthe front-end) by Ethernet

• configuration and measurement steps• advantages : low cost, modularity, quick performances evolution,user friendly development tools (C, LabVIEW, WEB interface)

• HPD and MaPMT have been characterized with an auto triggerable electronics and with an Ethernet acquisition

• OPERA :• first particle experiment with a full Ethernet DAQ• more than 1000 nodes connected• triggerless experiment, low data rate, single p.e. resolution

• MicroPET :• first medical applications• distributed system for medical imaging