the alice forward multiplicity detector kristján gulbrandsen niels bohr institute for the alice...
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The ALICE Forward Multiplicity Detector
Kristján GulbrandsenNiels Bohr Institute
for the ALICE Collaboration
The ALICE Detector
TPC
ITS
HMPID
TRD
PHOS
TOF
V0T0
FMD
Physics Motivation
Extend detection of total particles to forward (and backward) direction - increasing range of dNch/d
Measure azimuthal asymmetry of particles to determine event plane and perform elliptic flow measurements
Provide additional measure of centrality
Want a detector which has, on average, less than 1 particle per channel per event for the most central events
FMD Detector
3 regions of detectors to extend the acceptance
Each ring split into sectors of silicon modules
10240 silicon strips per ring
3.68<<5.03 1.70<<3.68 -3.40<<-1.70
-83.4 cm-75.2 cm75.2 cm83.4 cm320 cm 0 cm
4.2 cm17.2 cm
15.4 cm28.4 cm
Silicon Sensors
Silicon strip detectors 300 m thick Inner sensors
512 strips per side 13-50mm 250m per strip
Outer sensors 256 strips per side 24-42mm 500m per strip
Readout lines run over own strip only reducing crosstalk
13cm
Bonding pads
Bonding pads
Hybrids
VA preamplifier chips Low noise High gain Radiation hard
(0.35 m AMS Technology) 128 channels per chip Dynamic range of 0-20 MIPS
8 chips per inner hybrid 4 chips per outer hybrid
FMD Readout
8 / 4 8 / 4
FMD Module ON DETECTORIN
COUNTINGROOM
VA
1 ring: 10/20 modules 2 Digitizers 1 RCU per ring systemFull FMD: 70 modules 10 Digitizers 3 RCU’s
VA controland biasesVA controland biases
TTC-RX
BOARDCTRL
FMD Digitizer
ALTRO(16 ch) ALTRO(16 ch)
ALTRO(16 ch)ALTRO(16 ch)
ALTRO(16 ch)ALTRO(16 ch)
CONTROLCONTROL
Loca
l Mon
itor
and
Con
trol
BOARDcontroller
Bus
con
trol
ler
( co
nf. &
R/O
)
DCS int.(Ethernet)
DAQ int.(DDL-SIU)
Trigger int.(TTC-rx)
Data Proc.and Memory
DCS
DDL
RCU
Front-end bus 3 m
Front-end bus 3 m
40 40
Control Network(I2C-serial link)
Control Network(I2C-serial link)
Trigger L0
NEAR PATCH PANEL
Analog serial link(10 MHz) 0.5 mAnalog serial link(10 MHz) 0.5 m
5 / 10 5 / 10
Prototype Module
Prototype inner detector module built
Hybrids glued to sensors with thin spacers
Readout pads connected to silicon at periphery of hybrid
Noise Estimate
Main contribution to noise is from electronics+input capacitance and noise from bias resistors
Noise Source Short strips Long Strips
Elect. + cap. 263 e- 309 e-
Bias 208 e- 208 e-
Ileak 38 e- 72 e-
Total 337 e- 387 e-
Signal (1 MIP) 22000 e- 22000 e-
Signal/Noise 65 57
Inner Sensor Noise Estimate
Test Beam Results
Tested prototype with high energy electron beam (680 MeV)
Clear signal peak Signal/Noise~60
Conclusions
FMD prototype module shows excellent signal to noise characteristics (60:1)
Hit sharing accounts for most of the particles seen between the MIP peak and the noise peak
FMD is on schedule for collecting first day physics at the LHC
Hit Sharing
Test Beam Results
Tested prototype with high energy electron beam (680 MeV)
Clear signal peak Signal/Noise~60