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