Università di Roma 'La Sapienza' 28-06-2002Universitat de Barcelona

Front End Electronics for the SPD of LHCb

Electronics in Experimental High Energy Physics

Xavier Vilasís-CardonaEnginyeria i Arquitectura La Salle

URL - Barcelona

The collaboration in Barcelona Universitat de

Barcelona Lluis Garrido Ricardo Graciani David Gascón Ernest Aguiló Miriam Calvo Sergio Gómez Sebastià Bota Atilà Herms Angel Diéguez Xavier Cano

Enginyeria i Arquitectura La Salle Rafael Ballabriga Sonia Luengo Mar Roselló Jordi Riera Xvc

Outlook

What is LHC ? What is LHCb ? The SPD Photomultipliers Very Front End Electronics The ASIC Front End Electronics

LHC : the future collider at CERN

Proton-Proton Starting 2007 Find the Higgs Find new physics 4 detectors

Alice Atlas CMS LHCb

LHC : some data Energy at collision: 7 TeV (1700 TeV for ions) Dipole field at 7 TeV: 8.3 T Bunch spacing: 7.5 m Bunch separation: 24.95 ns Particles per bunch: 10^11 Current: 0.56 A Luminosity: 10^34 cm^2 s Energy per beam up to 0.35 GJ Stored magnetic energy up to 1.29 GJ per

sector TOTAL STORED ENERGY = 11 GJ

LHCb A single-arm

spectrometer covering min ~15 mrad

(beam pipe and radiation)

max ~300 mrad (cost optimisation)

Precise measurements of CP violation B mesons CKM matrix elements

LHCb : what is CP violation ? CPT is an exact symmetry

• C charge conjugation• P parity• T time reversal

CP is almost exact CP violation explains matter-antimatter asymmetry

LHCb : the trigger

LHCb = 1000k channels : too much data The multi-level trigger chain

Logging rate 200 Hz (20 MB/s) 200 TB/year All LHC experiments: 5-8 PB/year

Input rate Latency B/s

Level 0 40 MHz 3.2 μs 1 TB/s

Level 1 1 MHz 256 μs 4 GB/s

Level 2 40 kHz 10 ms

Level 3 5 kHz 200 ms

SPD Scintillator Pad Detector In front of the

calorimeter Discriminates photons

from electrons at level 0 of trigger

spd ps ecal

spd ps ecal

e

SPD structure 6000 Scintillator Pads Helicoidal WLS optic fibers 64 channel PMT (Hamamatsu) 1 bit per channel at 40 MHz Synchronisation issues

Send bit to PreShower

Compare to a variable threshold

Radiation hard

SPD signal shape

Few photoelectrons Irregular signal shape Extended over 25 ns Non-uniform PMT gain

SPD electronics design

ASIC : why an ASIC ?

6000 channels : minimal area /ch Processing speed 40 MHz Power consumption < 2 W / 64 channels Analog Processing + Digital Control Signal range. 0 to 5 MIP (0 to 650 mV) Electronics resolution 5% of 1 MIP Dynamic range: 40 dB (7 bits)

ASIC Structure

AD

+

- 17 %

+

m bits

Serial interfacefor thresholdprograming

PMT chan. 1

PMT chan. 2

Vref (or DAC range)

Digital differentiallink to PS FE

AD

+

+ n/2 links

PMT chan. n

IntegratorSingle to

differential

SPD VFEcontrol unit

Track & Hold Pile-upsubtract Comparator

Digitalmultiplexer

- 17 %

- 17 %

- 17 %

Channel clocks

generation(CMOS & ECL)

Clock frequency

division by 2

Bunch crossing

clock (40 MHz) Clock delay(about 2 ns)

ECL internal CLock

(20 MHz)

- 17 %

ASIC characteristics

ProgrammableProgrammable Thresholds per sub-channel Subtraction: from 0% up to 40% of the signal T0: done externally with a delay unit (LAL design)

0.8 m AMS BiCMOS Technology Dual channel Fully differential Working at 3.3V SEU and SEL protection

Triple voting Guard rings

Review of ASIC runs RUN1 (Sep 2000)

Test separate blocs 1 full channel

RUN2 (Jun 2001) 4 full channels ECL vs CMOS output

RUN3 (Jan 2002) New tunnable substractor 1 full channel with digital control On-chip DAC to program thresholds

RUN4 (Sep 2002) 1 Complete processing channel Separate blocs + digital control Works at 3.3 V to reduce power consumption Fully differential preamplifier added before the integration

stage to meet PMT DC current limit requirements

ASIC : RUN 4 layout

ASIC : integrator

ASIC : Track and Hold

ASIC : substractor

ASIC : latched comparator

Offset ( (Output Zero Error): ): <OZE> = + 38.6 mV<OZE> = + 38.6 mV ioio = 70 mV r.m.s. = 70 mV r.m.s. Gain: <Vo/Vi> = 16.51 (for a<Vo/Vi> = 16.51 (for a typical input pulse) typical input pulse) ioio = = 0.091 0.091 r.m.s.r.m.s. (0,55%)(0,55%) Treset = = 5.5 ns (for 1 V output)5.5 ns (for 1 V output) Noise EEnono < 2 mV r.m.s < 2 mV r.m.s (Using scope, C.F. 6)(Using scope, C.F. 6)

EEnono < 1 mV r.m.s < 1 mV r.m.s (Discriminator sweep of thresholds)(Discriminator sweep of thresholds)

-1500

-1000

-500

0

500

1000

1500

-100,0 -90,0 -80,0 -70,0 -60,0 -50,0 -40,0 -30,0 -20,0 -10,0 0,0

Threshold [mV]

Histogram for threshold sw eepDifferentiated histogram

-66 -64 -62 -60 -58 -56 -54

0

200

400

600

800

1000

Data: Data1_B'Model: Gauss Chi^2= 2081.19889R^2 = 0.98682 y0 51.68159 ±23.05052xc -61.70164 ±0.05011w 1.62784 ±0.11995A 1609.67905±130.96337

Diff

eren

tial h

isto

gram

Threshold [mV]

B'

ASIC : integrator measurements 10 circuits

-2500,00

-2000,00

-1500,00

-1000,00

-500,00

0,00

500,00

1000,00

1500,00

2000,00

2500,00

-4000,00 -3000,00 -2000,00 -1000,00 0,00 1000,00 2000,00 3000,00 4000,00

Input Signal [mV]

Th

resh

old

[m

V]

R2B02

R2B04

R2B05

R2B06

R2B07

R2B08

R2B09

R2B01

R2B10

ASIC : integrator linearity

ASIC : programmable substractor

Gain of the controlable block of the subtractor = f(Vb) (10 samples)

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

3,5 3,7 3,9 4,1 4,3 4,5 4,7 4,9

0102030405060708091001_soldat

VFE Board description

100 boards7x12 cmMultiplexed LVDS

Very Front End Board

Test beam boards

Sep 2001: RUN 2, 4 full channels/ 4-layer board•ECL vs CMOS output•Clock signal distribution•Power Supply distribution

June 2002: RUN 2, 4 full channels / 4-layer board•Improvements in board design•Signals distribution

June 2002: RUN 3, 1 full channel and digital control/ 6-layer board

•Digital signal distribution vs analog signal distribution•Noise effect vs number of layers

Front End Board

Control Unit : •Bus Bridge•Programmable Delays

1 Control Unit every 4 VFE Boards5 Control Units in a Front End Board6 Front End Boards

Conclusions