Post on 25-Dec-2015
November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 1
Electronic requirements for detectors
Use LHC systems to illustrate
physics technical
Tracking high spatial precisionlarge channel countlimited energy precisionlimited dynamic range
low power ~ mW/channelhigh radiation levels ~10Mrad
Calorimetry
high energy resolutionlarge energy rangeexcellent linearityvery stable over time
intermediate radiation levels ~0.5Mradpower constraints
Muons very large areamoderate spatial resolutionaccurate alignment & stability
low radiation levels
November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 2
Generic LHC readout system
Amplifier
Pipeline
memory
Electrical
or
optical link
DAQ Driver
DAQ
Comparator
MUX
A/D
Receiver
A/D
DSP
...
Clock
Trigger
Control
(optional) (optional)
Amplifier
Pipeline
memory
Electrical
or
optical link
DAQ Driver
DAQ
Comparator
MUX
A/D
Receiver
A/D
DSP
...
Clock
Trigger
Control
(optional) (optional)
Amplifier
Electrical
or
optical link
MUX
A/D
Pipeline
memory
DAQ Driver
DAQ
Receiver
A/D
DSP
...
Clock
Trigger
Control
Amplifier
Electrical
or
optical link
MUX
A/D
Pipeline
memory
DAQ Driver
DAQ
Receiver
A/D
DSP
...
Clock
Trigger
Control
•functions required by all systemsamplification and filteringanalogue to digital conversionassociation to beam crossingstorage prior to triggerdeadtime free readout @ ~100kHzstorage pre-DAQcalibrationcontrol monitoring
•CAL & Muons special functionsfirst level trigger primitive generation
•optionallocation of digitisation & memory
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 deadtimedata often buffered in pipeline
queueing problem
APV25 NB ≈ 10, NP =192 @100kHz
compare with deadtime from maximum trigger sequence = 1001… = 50ns/10µs = 0.5%
November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 4
Basic radiation effects on electronics
• Bipolaratomic displacement
carrier recombination in basegain degradation, transistor matching,dose rate dependence
• CMOS oxide charge & trap build-upthreshold (gate) voltage shift, increased noise,…change of logic state = SEU
• All technologiesparasitic devices created => Latch-up can be destructive
p+nn++emittercollectorbaseIBICIEp+nn++emittercollectorbaseIBICIE
p typedrainsourcegaten typedepleted regionoxideinverted channelsubstratep typedrainsourcegaten typedepleted regionoxideinverted channelsubstrate
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 toleranceextra 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 VT vs toxide
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
November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 7
Tracking systems
•ATLAS•Innermost: Pixels•Inner: Silicon microstrips 6M channels
Occupancy 1-2%
•Outer: Transition Radiation tracker gas filled 4mm diameter straw tubes 420k channelsx-ray signals from e- above TR thresholdoccupancy ~ 40%
•CMS•Innermost: Pixels•Remainder: Silicon microstrips 10M channels
Occupancy 1-2%
•Radiation hardness is a crucial point for trackers
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 pileupbaseline restorer => maintain threshold levelstwo level discriminator => electron identification
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 restorationselectable for CF4 and Xe gas mixtures
4mm straw + Xenon based gas
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
simplesmall data volumebutmaintain 6M thresholdsvulnerable to common mode noise
•SpecificationsENC < 1500eEfficiency 99%Bunch crossing tag 1 bunch crossingNoise occupancy 5x10-4
Double pulse resolution 50ns after 3.5fC signalDerandomising buffer 8 deepPower <3.8mW/channel
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 systemno zero suppressionmaximal informationimproved operation, performance and monitoring
•0.25µm CMOS technology intrinsic radiation hardness
•Off-detector digitisation analogue optical data transmission reduce custom radiation-hard electronics
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/channelPerformance must be maintained after irradiation
•Start from CR-RC filter waveformform weighted sum of pulse samples
zero response outside narrow time window small number of weights (>3)implementable in CMOS switched capacitor filter
w(t)= a1.h(t)+a
2.h(t-Δ )+t a3. ( -2h t Δ )t
Ideal CR-RC
Sampled CR-RCwaveform
Deconvolutedwaveform
November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 13
2000
1600
1200
800
400
02520151050-5-10
chan 2 chan 43 chan 107
closed symbols: peak mode: 270 + 38/pFopen symbols:deconvolution: 430 + 61/pF
2000
1600
1200
800
400
02520151050-5-10
chan 2 chan 43 chan 107
closed symbols: peak mode: 270 + 38/pFopen symbols:deconvolution: 430 + 61/pF
Pulse shapes & noise APV25
• 125
100
75
50
25
0
250200150100500
2pF 4p1 8p1 10p7 14p5 17p5 20p5
125
100
75
50
25
0
250200150100500
2pF 4p1 8p1 10p7 14p5 17p5 20p5
1 MIP signal
EN
C [
ele
ctro
ns]
Input capacitance [pF]
t [ns]
•System specification
Noise <2000 electrons
for CMS lifetime
•System specification
Noise <2000 electrons
for CMS lifetime
November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 14
Calorimeter systems
•ATLAS ECAL/Endcap HCALLiquid Argon 190k channels
signal: triangular current ~500ns fall (drift time)
CD ~ 200-2000pF
•ATLAS Barrel HCALScintillating tiles 10k channels
•CMS ECALPbWO4 crystals + APDs (forward: VPT)
80k channels
fast signal ~ 10ns CD = 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)
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 selection12bit 40MHz digitisationcommercial 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
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 requirementsdigital control ~40Ms/s digital data transmission ~1Gb/s analogue: 40Ms/s CMS Tracker
•Fast moving technological area driven by applications
digital telecomms, computer linksanalogue cable TVrequirements c.f. commercial systems
bulk, power, cost, radiation tolerance ?? possible for some applications?
November 2001 g.hall@ic.ac.uk www.hep.ph.ic.ac.uk/~hallg/ 17
Semiconductor lasers
•Now dominate market, over LEDsnarrow beam, high optical power, low electrical power, better matched to fibres
•Direct band gap materialGaAs ~ 850nmGaAlAs ~ 600-900nm In, Ga, As, P ~ 0.55-4µm
•Forward biased p-n diode -> population inversionoptical cavity => laser at I > Ithreshold
often very linear response
•Fibres and connectorssufficient rad hardnesstrackers require miniature connectorscare with handling compared to electrical
8
6
4
2
02520151050
Current (mA)
un-irradiated after 2x10
14n/cm
2
8
6
4
2
02520151050
Current (mA)
un-irradiated after 2x10
14n/cm
2
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 diodesminiature devices requiredsingle mode fibre ~50mW/256 detector channels
Si-submount
PIN photodiode
Fibre
2 mm
1.5 mm
Si-submount
PIN photodiode
Fibre
2 mm
1.5 mm
Laser die
2 mm
1.5 mm
Si-submount
Fibre
Laser die
2 mm
1.5 mm
Si-submount
Fibre
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-0.150454035302520151050
Time [ns]
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
input output
5 ns 5 ns20 ns
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-0.150454035302520151050
Time [ns]
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
input output
5 ns 5 ns20 ns
TxTx
Rx
same components for digital control BER << 10-12 easily achievable