Universitat de Barcelona Università di Roma 'La Sapienza' Front End Electronics for the SPD of LHCb Electronics in Experimental High Energy Physics Xavier Vilasís-Cardona Enginyeria 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: 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 rateLatencyB/s Level 040 MHz3.2 μs1 TB/s Level 11 MHz256 μs4 GB/s Level 240 kHz10 ms Level 35 kHz200 ms

SPD Scintillator Pad Detector In front of the calorimeter Discriminates photons from electrons at level 0 of trigger spdpsecal spdpsecal 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

ASIC characteristics  Programmable  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

 (): = mV  io = 70 mV r.m.s.  Offset (Output Zero Error): = mV  io = 70 mV r.m.s.  = (for a typical input pulse)  io = r.m.s. (0,55%)  Gain: = (for a typical input pulse)  io = r.m.s. (0,55%)  = 5.5 ns (for 1 V output)  Treset = 5.5 ns (for 1 V output)  E no < 2 mV r.m.s (Using scope, C.F. 6)  Noise E no < 2 mV r.m.s (Using scope, C.F. 6) E no < 1 mV r.m.s (Discriminator sweep of thresholds) E no < 1 mV r.m.s (Discriminator sweep of thresholds) ASIC : integrator measurements 10 circuits

ASIC : integrator linearity

ASIC : programmable substractor

VFE Board description  100 boards  7x12 cm  Multiplexed 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 Boards 5 Control Units in a Front End Board 6 Front End Boards

Conclusions