![Page 1: The ALICE Forward Multiplicity Detector Kristján Gulbrandsen Niels Bohr Institute for the ALICE Collaboration](https://reader036.vdocuments.us/reader036/viewer/2022081603/56649f1c5503460f94c32448/html5/thumbnails/1.jpg)
The ALICE Forward Multiplicity Detector
Kristján GulbrandsenNiels Bohr Institute
for the ALICE Collaboration
![Page 2: The ALICE Forward Multiplicity Detector Kristján Gulbrandsen Niels Bohr Institute for the ALICE Collaboration](https://reader036.vdocuments.us/reader036/viewer/2022081603/56649f1c5503460f94c32448/html5/thumbnails/2.jpg)
The ALICE Detector
TPC
ITS
HMPID
TRD
PHOS
TOF
V0T0
FMD
![Page 3: The ALICE Forward Multiplicity Detector Kristján Gulbrandsen Niels Bohr Institute for the ALICE Collaboration](https://reader036.vdocuments.us/reader036/viewer/2022081603/56649f1c5503460f94c32448/html5/thumbnails/3.jpg)
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
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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
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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
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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
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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
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Prototype Module
Prototype inner detector module built
Hybrids glued to sensors with thin spacers
Readout pads connected to silicon at periphery of hybrid
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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
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Test Beam Results
Tested prototype with high energy electron beam (680 MeV)
Clear signal peak Signal/Noise~60
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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
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Hit Sharing
![Page 13: The ALICE Forward Multiplicity Detector Kristján Gulbrandsen Niels Bohr Institute for the ALICE Collaboration](https://reader036.vdocuments.us/reader036/viewer/2022081603/56649f1c5503460f94c32448/html5/thumbnails/13.jpg)
Test Beam Results
Tested prototype with high energy electron beam (680 MeV)
Clear signal peak Signal/Noise~60