Transcript LHC front end electronics

Development of a tracking detector for physics at
the Large Hadron Collider
Geoff Hall
CMS = Compact Muon Solenoid detector
• missing element in current theoretical framework - mass
Total weight
Diameter
Length
Magnetic field
12,500 tons
15m
21.6m
4T
Tracking system
10 million microstrips
Diameter
2.6m
Length
7m
Power
~50kW
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October 2002
LHC parameters (CMS)
pp
34
Pb-Pb
-2
-1
27
-2
10 cm .s
Annual integrated L
5x10 cm
?
CM energy
14 TeV
5.5 TeV/N
 inelastic
~70mb
~6.5 b
interactions/bunch
~20
0.001
tracks/unit rapidity
~140
3000-8000
beam diameter
20µm
20µm
bunch length
75mm
75mm
beam crossing rate
40MHz
8MHz
Level 1 trigger delay
- 3.2µsec
- 3.2µsec
L1 (average) trigger rate
Š100kHz
< 8kHz
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-2
10 cm .s
• Consequences
-1
Luminosity
High speed signal processing
Signal pile-up
High (low) radiation exposure
High (low) B field operation
Very large data volumes
New technologies
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October 2002
Design philosophy
• Large solenoidal (4T) magnet
iron yoke - returns B field, absorbs particles
technically challenging but
smaller detector, p resolution, trigger, cost
• Muon detection
high pT lepton signatures for new physics
• Electromagnetic calorimeter
high (DE) resolution, for H => gg (low mass mode)
• Tracking system
momentum measurements of charged particles
pattern recognition & efficiency
complex, multi-particle events
complement muon & ECAL measurements
improved p measurement (high p)
E/p for e/g identification
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October 2002
Parameters for hadronic collider physics
• E, p, cosq, f
prefer variables which easily Lorentz transform
e.g E, pT, pL, f
• pT
divergences from simple behaviour could imply new physics
eg heavy particle decay => high pT lepton (or hadron)
• rapidity
y
1 E  pL
ln(
)
2 E  pL
dy 
Lorentz boost
y  y  y 
• pseudorapidity
LHC
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dpL
E
dN
1 1
invariant
ln(
) =>
dy
2
1
m2
cos (q 2)  2  ...
1
4p
y  ln(
)   ln t an(q 2)  
2
m
2
2
sin (q 2)  2  ...
4p
d 2 Nch arged
 H. f ( pT )
d.dpT
2
H~ 6 || < 2.5
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October 2002
Physics requirements (I)
• Mass peak - one means of discovery
m  i Ei  pi
=> small (pT)
2
2
2
eg H => ZZ or ZZ* => 4l±
typical pT(µ) ~ 5-50GeV/c
• Background suppression
measure lepton charges
good geometrical acceptance - 4 leptons
background channel
t => b => l
require m(l+l-) = mZ GZ ~ 2.5GeV
precise vertex measurement identify b decays, or reduce fraction in data
tt
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October 2002
Physics requirements (II)
• p resolution
 ( pT )
pT
~ pT
 meas
2
B.L
N pt s
large B and L
• high precision space points
detector with small intrinsic meas
• well separated particles
good time resolution
low occupancy => many channels
good pattern recognition
• minimise multiple scattering
• minimal bremsstrahlung, photon conversions
material in tracker
most precise points close to beam
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DpT
 0.15pT (TeV )  0.5%
pT
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October 2002
Silicon diodes as position detectors
~25µm
• Spatial measurement
precision defined by
strip dimensions
ultimately limited by
charge diffusion
~1pF/cm
~300µm
 ~ 5-10µm
~0.1pF/cm
+V
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bia s
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October 2002
Vertex detector ~1990
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October 2002
Interactions in CMS
7 TeV p
7 TeV p
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October 2002
Microstrip tracker system
2.4m
~10M
detector
channels
~ 6m
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October 2002
Event in the tracker
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October 2002
Silicon detector modules
• Constraints on tracker
minimal material
high spatial precision
sensitive detectors requiring
low noise readout
power dissipation ~50kW
in 4T magnetic field
radiation hard
Budget
• Requirements
large number of channels
limited energy resolution
limited dynamic range
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October 2002
Radiation environment
• Particle fluxes
Charged and neutral particles from interactions
Neutrons from calorimeter
~ 1/r2
nuclear backsplash + thermalisation ≈ more uniform gas
only E > 100keV damaging
• Dose
energy deposit per unit volume
Gray = 1Joule/kg = 100rad
mostly due to charged particles
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October 2002
Imperial College contributions to Tracker
APV25
APVMUX/PLL
FED
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•
•
•
•
Hardware development
Hardware construction
Beam tests & studies
Preparation for physics
October 2002
APV25
0.25µm CMOS
1 of the 128 channels
Analogue
unity gain
inverter
SF
Low noise
charge
preamplifier
SF
50 ns CRRC shaper
programmable
gain
192-cell
analogue
pipeline
S/H
128:1 Differential
current
MUX
O/P
signal
processing
&
pipeline
amplifiers memory MUX
APSP
control logic
APV25-S1
(Aug 2000)
Chip Size 7.1 x 8.1 mm
Final
APV25-S0
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(Oct 1999)
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October 2002
Chip testing
• Automated on-wafer testing
~1min/site
~100,000 to test
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October 2002
Irradiations of 0.25µm technology
Id [A]
• Extensive studies
CMS tracker data from IC, Padova, CERN
ALL POSITIVE and well beyond LHC range
• CMOS hard against bulk damage
Qualify chips from wafers
with ionising sources
10
-3
10
-4
10
-5
10
-6
10
-7
10
-8
10
-9
10
PMOS
Pre-rad
50 Mrad
Anneal
-10
-0.6
PMOS
2000/0.36
400µA
5
-0.4
-0.2
Vg [V]
0.0
to 10, 20, 30 & 50Mrad
1/2
• Typical irradiation conditions
50kV X-ray source
Dose rate ~ 0.5Mrad/Hour
Noise [mV/Hz ]
0.01
9
8
7
6
4
3
2
0.001
4
2
10
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pre-rad
10 Mrad
20 Mrad
30 Mrad
50 Mrad
anneal
18
4 6
5
2
4 6
6
10
10
Frequency [Hz]
2
4 6
7
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October 2002
0.2
APV25 irradiations
(IC & Padova)
• IC x-ray source
Normal operational bias during irradiation
clocked & triggered
Post irradiation noise change insignificant
APV25-S1
500
500
400
400
300
300
200
200
100
100
0also 10 MeV linac electrons(80Mrad) and
0
0 50 100 150 200 250
0
pre-rad
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10 Mrad
2.1x1014 reactor n.cm-2
50 100 150 200 250
October 2002
Silicon as a detector material
• Detectors operated as reverse biased diode
dark current = noise source
signals small
typical H.E. particle ~ 25000 e 300µm Si
10keV x-ray photon ~ 2800e
• Deplete entire wafer thickness
Vbias ~ NDd2
ND ~ 1012 cm-3
=> Vbias ~ 50V for 300µm
ND : NSi ~ 1 : 1013
ultra high purity
• Further refining required
Float Zone: local crystal melting with RF heating coil
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October 2002
Radiation effects in (bulk) silicon
• Silicon atoms dislodged from lattice sites…
causing more damage as they come to rest... after irradiation
increased dark currents
altered substrate doping
primary defects = V & I
diffuse and become trapped
influenced by O & C impurity levels
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October 2002
CMS Silicon Strip Tracker Front End Driver
96 Tracker
Opto Fibres
CERN
OptoRx Analogue/Digital
9U VME64x
Data Rates
12
JTAG
9U VME64x Form Factor
Modularity matched Opto Links
12
FE-FPGA
Cluster
Finder
12
FPGA
Configuration
VME
Interface
VME-FPGA
BE-FPGA
Event Builder
12
TCS
Analogue: 96 ADC channels (10-bit
@ 40 MHz )
@ L1 Trigger : processes 25K
MUXed silicon strips / FED
TTC
TTCrx
12
Buffers
DAQ
Interface
12
Raw Input: 3 Gbytes/sec*
after Zero Suppression...
DAQ Output: ~ 200 MBytes/sec
12
Temp
Monitor
12
Front-End Modules x 8
Double-sided board
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Xilinx
Virtex-II
FPGA
Power
DC-DC
~440 FEDs required for entire SST
Readout System
TCS : Trigger Control System
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*(@ L1 max rate = 100 kHz)
October 2002
averages
d
8
a
d
a
8 s-data
8 s-addr
hit
No hits
averages
8
16
8
d
a
DPM
11
d
a
DLL
Synch
16
8
nx256x16
Sequencer-mux
status
trig3
Synch in
Synch out
emulator in
Synch error
16
8
Global reset
Sub resets
Full flags
control
4 data
160 MHz
Serial I/O
Local
IO
11
256 cycles
Hit finding
trig2
Re-order
cm sub
10
header
Temp Sensor
Opto Rx
10
Ped sub
ADC 12
trig1
sync
10
Phase
Registers
256 cycles
Clock 40
MHz
Control
8
16
mux
status
8 s-data
8 s-addr
hit
No hits
DPM
11
trig4
4x
header
trig3
nx256x16
Sequencer-mux
11
256 cycles
Hit finding
10
trig2
Re-order
cm sub
10
Ped sub
trig1
sync
10
Phase
Registers
2 x 256 cycles
ADC 1
1x
2x
4x
Cluster Finding FPGA VERILOG Firmware
Packetiser
per adc channel phase
compensation required to bring
data into step
Front-End FPGA Logic
Serial Int
CMS Silicon Strip Tracker FED
Delay Line
+ Raw Data mode, Scope mode, Test modes...
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B’Scan
Config
October 2002
The CMS Tracking Strategy
• Rely on “few” measurement layers,
each able to provide robust (clean) and
precise coordinate determination
2-3 Silicon Pixel
10 - 14 Silicon Strip Layers
Number of hits by tracks:
Total number of hits
Double-side hits
Double-side hits in thin detectors
Double-side hits in thick
detectors
Radius ~ 110cm, Length/2 ~ 270cm
6 layers
TOB
4 layers
TIB
3 disks TID
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9 disks TEC
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October 2002
Vertex Reconstruction
Primary vertices: use pixels!
At high luminosity, the
trigger primary vertex
is found in >95% of
the events
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October 2002
High Level Trigger & Tracker
DAQ
In High Level trigger reconstruction only 0.1%
of the events should survive.
40 MHZ
“How can I kill these events using the least
CPU time?”
This can be interpreted as:
o The fastest (most approx.) reconstruction
o The minimal amount of precise reconstruction
o A mixture of the two
100 KHz
100 Hz
HLT Track
finding
Same SW would be use in HLT and off-line :
Events rejected at HLT are
irrecoverably lost!
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algorithms should be high quality
algorithms should be fast enough
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October 2002
References
• A. Litke & A. Schwarz Scientific American May 1995
• T. Liss & P. Tipton Scientific American September 1997
• N. Ellis & T. Virdee. Experimental Challenges in High Luminosity Collider Physics. Ann. Rev. Nucl. Part. Sci 44
(1994) 609-653.
• G.Hall Modern charged particle detectors Contemporary Physics 33 (1992) 1-14 & refs therein
• G.Hall Semiconductor particle tracking detectors Reports on Progress in Physics.57 (1994) 481-531
• A. Schwarz 1993 Heavy Flavour Physics at Colliders with silicon strip vertex detectors. Physics Reports
238 (1994) 1-133.
• C. Damerell Vertex detectors: The state of the art and future prospects. Rutherford Appleton Laboratory
report RAL-P-95-008 A pdf version is available on the CERN library Web site.(Search preprints)
• CMS Web pages
http://cmsdoc.cern.ch/cmsnice.html
• http://cmsinfo.cern.ch/Welcome.html Letter of Intent (most readable) and and Technical proposal
• http://cmsdoc.cern.ch/cms/TDR/TRACKER/tracker.html CMS Tracker Technical Design Report (even
more detail on many aspects) of the tracker.
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October 2002