1. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 1 Electronic requirements for detectors Use LHC systems to illustrate physicstechnical Tracking high spatial precision large channel count limited energy precision limited dynamic range low power ~ mW/channel high radiation levels ~10Mrad Calorimetry high energy resolution large energy range excellent linearity very stable over time intermediate radiation levels ~0.5Mrad power constraints Muons very large area moderate spatial resolution accurate alignment & stability low radiation levels

2. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 2 Generic LHC readout system functions required by all systems amplification and filtering analogue to digital conversion association to beam crossing storage prior to trigger deadtime free readout @ ~100kHz storage pre-DAQ calibration control monitoring CAL & Muons special functions first level trigger primitive generation optional location of digitisation & memory

3. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 3 “Deadtime free” operation Pipeline memory buffer depth and trigger rate determine deadtime data often buffered in pipeline queueing problem APV25 N B ≈ 10, N P =192 @100kHz compare with deadtime from maximum trigger sequence = 1001… = 50ns/10µs = 0.5%

4. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 4 Basic radiation effects on electronics Bipolar atomic displacement  carrier recombination in base gain degradation, transistor matching, dose rate dependence CMOS oxide charge & trap build-up threshold (gate) voltage shift, increased noise,… change of logic state = SEU All technologies parasitic devices created => Latch-up can be destructive

5. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 5 Why 0.25µm CMOS? by 1997 some (confusing) evidence of radiation tolerance extra thin gate oxide beneficial tunnelling of electrons neutralises oxide charge negative effects attributed to leakage paths around NMOS transistors cure with enclosed gate geometry 1Mrad V T vs t oxide

6. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 6 First results from 0.25µm CMOS (1997) technology thought to be viable for intermediate radiation levels (~300krad) but results much better than expected

7. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 7 Tracking systems ATLAS Innermost: Pixels Inner: Silicon microstrips6M channels Occupancy 1-2% Outer: Transition Radiation tracker gas filled 4mm diameter straw tubes 420k channels x-ray signals from e- above TR threshold occupancy ~ 40% CMS Innermost: Pixels Remainder: Silicon microstrips10M channels Occupancy 1-2% Radiation hardness is a crucial point for trackers

8. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 8 ATLAS TRT readout ASDBLR amplifier/shaper/discriminator key points speed and stability, since high occupancy peaking time 7-8ns => reduce pileup baseline restorer => maintain threshold levels two level discriminator => electron identification

9. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 9 ATLAS TRT ASDBLR front end Amplifier =>tail cancellation and baseline restoration selectable for CF 4 and Xe gas mixtures 4mm straw + Xenon based gas

10. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 10 ATLAS SCT front end Amplifier/discriminator + pipeline/sparse readout ABCD (BiCMOS) Binary readout simple small data volume but maintain 6M thresholds vulnerable to common mode noise Specifications ENC < 1500e Efficiency99% Bunch crossing tag 1 bunch crossing Noise occupancy5x10 -4 Double pulse resolution 50ns after 3.5fC signal Derandomising buffer 8 deep Power <3.8mW/channel

11. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 11 CMS microstrip tracker readout 10 million detector channels Analogue readout synchronous system no zero suppression maximal information improved operation, performance and monitoring 0.25µm CMOS technology intrinsic radiation hardness Off-detector digitisation analogue optical data transmission reduce custom radiation-hard electronics

12. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 12 Impulse deconvolution at LHC High speed signal processing is required to match the 40MHz beam crossings Low power consumption is essential - 2-3mW/channel Performance must be maintained after irradiation Start from CR-RC filter waveform form weighted sum of pulse samples zero response outside narrow time window small number of weights (>3) implementable in CMOS switched capacitor filter Ideal CR-RC Sampled CR-RC waveform Deconvoluted waveform

13. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 13 Pulse shapes & noiseAPV25 1 MIP signal ENC [electrons ] Input capacitance [pF] t [ns] System specification Noise <2000 electrons for CMS lifetime System specification Noise <2000 electrons for CMS lifetime

14. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 14 Calorimeter systems ATLAS ECAL/Endcap HCAL Liquid Argon 190k channels signal: triangular current ~500ns fall (drift time) C D ~ 200-2000pF ATLAS Barrel HCAL Scintillating tiles 10k channels CMS ECAL PbWO 4 crystals + APDs (forward: VPT) 80k channels fast signal  ~ 10ns C D = 35-100pF CMS Barrel/Endcap HCAL Cu /scintillating tiles with WLS 11k channels HPD readout Requirements large dynamic range 50MeV-2TeV = 92dB = 15-16bits precision ≈ 12bits and high stability precise calibration ~ 0.25% Radiation environment few 100krad - Mrad +high neutron fluxes (forward)

15. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 15 CMS crystal ECAL Amplifier close to photo-detector (APD or VPT) 4 gain amplifier + FPU gain selection 12bit 40MHz digitisation commercial bipolar ADC - rad hard 1Gb/s optical transmission 12bit (data) + 2bit (range) custom development using VCSELs 80,000 low power links Recent substantial changes in philosophy

16. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 16 Optical links in LHC experiments Advantages c.f. copper: low mass, no electrical interference, low power, high bandwidth LHC requirements digital control ~40Ms/s digital data transmission ~1Gb/s analogue: 40Ms/s CMS Tracker Fast moving technological area driven by applications digitaltelecomms, computer links analoguecable TV requirements c.f. commercial systems bulk, power, cost, radiation tolerance ?? possible for some applications?

17. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 17 Semiconductor lasers Now dominate market, over LEDs narrow beam, high optical power, low electrical power, better matched to fibres Direct band gap material GaAs ~ 850nm GaAlAs ~ 600-900nm In, Ga, As, P ~ 0.55-4µm Forward biased p-n diode -> population inversion optical cavity => laser at I > I threshold often very linear response Fibres and connectors sufficient rad hardness trackers require miniature connectors care with handling compared to electrical

18. November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 18 CMS Tracker analogue optical links Edge emitting 1.3µm InGaAsP MQW laser diodes miniature devices required single mode fibre ~50mW/256 detector channels Tx Rx same components for digital control BER << 10 -12 easily achievable