Silicon Preshower for the CMS: BARC Participation

Anita TopkarBARC

CMS Preshower Detector

End caps of CMS detector has ~4300 silicon strip detectors covering area of~17 m2

BARC has delivered 1100 detector modules forthe CMS preshower

Production of additional detectors (~400 wafers) was carried out to meet the shortfall

The Preshower Silicon Detector

Preshower silicon strip detector is being

used for 0/ rejection in the ECAL, CMS

• Strips of 1.80 mm width with a pitch of 1.9 mm• Area - 63mm x 63mm

Detector specifications are very stringent as they are to be operated in a high radiation background of neutrons ( 2x10 14 /cm2) & gamma ( 10Mrad) for a long period often years

Technology development and production of detectors• Technology developed by BARC in eight batches using BEL

facility. Knowhow for fabrication of detectors was provided to BEL

• Detectors were designed during various phases (prototype, preproduction, production)

• Characterization setups and probe jigs developed and quality control facility setup at BEL during production

• Quality control of detectors was carried out (BARC and Delhi university)

• Micromodule production facility was setup at BEL

There was lot of support from CERN Preshower Group during production of silicon detectors and modules in India)

Strip Detectors for CMS Experiment at LHC, CERN

Silicon detectors produced by BARC cover an area of 40,000 cm2 in the CMS detector of LHC

Wafers designed and fabricated during various stages of development

1 2 3

Detector module

Front end hybrid developed by CERN

Detector Specifications

Electrical

High breakdown voltage Breakdown voltage for all strips >= 300V/500VLow leakage:Total current of all strips <= 10 μA at 300VUniformity of all strips: Maximum 1 strip with leakagecurrent> 5 μA at 300V

Geometrical

Tight control over dimensionsLength 63.0 +- 0.1 mmWidth 63.0 +0.0, -0.1 mm

Detector Design

Design for improving breakdown voltage & reducing the leakage current

Floating field guard rings Rounded cornersField plates

Fabrication Process High resistivity <111>, FZ wafers Ion implanted junctions with oxide

passivation P+ guard rings Gettering to reduce leakage currents Aluminum metallization PSG passivation on the top

Fabrication process optimized in eight batches to achieve desired specifications

Quality control of the strip detector

Leakage current of strips, capacitance of strips, full depletion voltage, breakdown voltage, mechanical tolerances on geometry

• Probe-jigs to make contact to the 32 strips simultaneously• Simulaneous measurement of strip current of 32 strips ( IV)• Simulaneous measurement of strip capacitance of 32 strips

( CV)

Probe-jigs, measurement setups required for qualification of detectors and modules were developed. Test facility was setup at BEL for qualification of detectors as per the CERN specifications

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Performance of detectors supplied to CERN

Breakdown voltage Total current at 300V

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Voltage (Volts)

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Radiation hardness of sensors

Change of full depletion voltage due to a neutron dose of 2x1014 n/cm2

Production of sensor micromodules

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Detector Ceramic tile

Detector aligned and glued to ceramic tile

Aluminum tile

Complete micromodule with readout hybrid assembled on ladder

Fully assembled Preshower Dee plane

The assembled end cap with micromodules – Assembly, Installation and Commissioning by CERN

Participation in CMS : Benefits

• Technology development for large area silicon strip detectors was Initiated

• Capability for large scale production for detectors using industry facilities is developed

• This also resulted in the development of a wide range of silicon detectors for applications in BARC and for international Experiments

Large area PIN diodes Pad detectors for physics experiments and radiation monitoring

PIN photodiodes for scintillators & X-ray imaging

Silicon microstrip detectors for PHENIX Experiment at RHIC, BNL

Silicon pad detectors for experiments at GANIL, France

Silicon detectors developed by BARC

Thanks you