Silicon Preshower for the CMS: BARC Participation Anita Topkar BARC

CMS Preshower Detector End caps of CMS detector has ~4300 silicon strip detectors covering area of~17 m2 BARC has delivered 1100 detector modules for the 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 of ten 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)

Front end hybrid developed by CERN Strip Detectors for CMS Experiment at LHC, CERN Wafers designed and fabricated during various stages of development 1 2 3 Front end hybrid developed by CERN Silicon detectors produced by BARC cover an area of 40,000 cm2 in the CMS detector of LHC Detector module

Detector Specifications Electrical High breakdown voltage Breakdown voltage for all strips >= 300V/500V Low leakage:Total current of all strips <= 10 μA at 300V Uniformity of all strips: Maximum 1 strip with leakage current> 5 μA at 300V Geometrical Tight control over dimensions Length 63.0 +- 0.1 mm Width 63.0 +0.0, -0.1 mm

Detector Design Design for improving breakdown voltage & reducing the leakage current Floating field guard rings Rounded corners Field 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

Performance of detectors supplied to CERN Total current at 300V Breakdown voltage

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

Production of sensor micromodules Detector Ceramic tile Detector aligned and glued to ceramic tile Aluminum tile Complete micromodule with readout hybrid assembled on ladder

The assembled end cap with micromodules – Assembly, Installation and Commissioning by CERN Fully assembled Preshower Dee plane

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

Silicon detectors developed by BARC Silicon microstrip detectors for PHENIX Experiment at RHIC, BNL Large area PIN diodes Pad detectors for physics experiments and radiation monitoring Silicon pad detectors for experiments at GANIL, France PIN photodiodes for scintillators & X-ray imaging

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