The ALICE Forward Multiplicity Detector Kristjn Gulbrandsen Niels

The ALICE Forward Multiplicity Detector Kristján Gulbrandsen Niels Bohr Institute for the ALICE Collaboration

The ALICE Detector HMPID TRD TPC ITS FMD TOF T 0 V 0 PHOS

Physics Motivation Want a detector which has, on average, less than 1 particle per channel per event for the most central events n n n Extend detection of total particles to forward (and backward) direction - increasing range of d. Nch/d Measure azimuthal asymmetry of particles to determine event plane and perform elliptic flow measurements Provide additional measure of centrality

FMD Detector n 320 cm 83. 4 cm 75. 2 cm 3. 68< <5. 03 1. 70< <3. 68 0 cm -75. 2 cm -83. 4 cm -3. 40< <-1. 70 n n 4. 2 cm 17. 2 cm 15. 4 cm 28. 4 cm 3 regions of detectors to extend the acceptance Each ring split into sectors of silicon modules 10240 silicon strips per ring

Silicon Sensors Bonding pads n Silicon strip detectors n n 300 m thick Inner sensors n n 13 cm n Outer sensors n n n Bonding pads 512 strips per side 13 -50 mm 250 m per strip 256 strips per side 24 -42 mm 500 m per strip Readout lines run over own strip only reducing crosstalk

Hybrids n VA preamplifier chips n n n n 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 5 / 10 8/4 FMD Digitizer ALTRO (16 ch) 40 VA ALTRO (16 ch) CONTROL RCU Data Proc. and Memory DAQ int. 2 Digitizers 10 Digitizers DDL (DDL-SIU) BOARD CTRL controller TTC-RX DCS int. DCS (Ethernet) Trigger int. (TTC-rx) Control Network (I 2 C-serial link) VA control and biases 1 ring: 10/20 modules Full FMD: 70 modules Front-end bus 3 m Bus controller ( conf. & R/O ) Analog serial link (10 MHz) 0. 5 m NEAR PATCH PANEL Local Monitor and Control ON DETECTOR FMD Module IN COUNTING ROOM Trigger L 0 1 RCU per ring system 3 RCU’s

Prototype Module n n n Prototype inner detector module built Hybrids glued to sensors with thin spacers Readout pads connected to silicon at periphery of hybrid

Noise Estimate Inner Sensor Noise Estimate Noise Source Short strips Long Strips Elect. + cap. 263 e- 309 e- Bias 208 e- 38 e- 72 e- 337 e- 387 e- Signal (1 MIP) 22000 e- Signal/Noise 65 57 Ileak Total n Main contribution to noise is from electronics+input capacitance and noise from bias resistors

Test Beam Results n n n Tested prototype with high energy electron beam (680 Me. V) Clear signal peak Signal/Noise~60

Conclusions n n n 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 n n n Tested prototype with high energy electron beam (680 Me. V) Clear signal peak Signal/Noise~60