1. QA Tests Tests for each sensor Tests for each strip Tests for structures Process stability tests Irradiation tests Bonding & Module assembly Si detectors1272  6.2 × 6.2 cm 2 648  4.2 × 6.2 cm 2 452  2.2 × 6.2 cm 2 172 sectors/modules1040 ladders106 r/o channels2.1 M r/o chips16.6 k r/o boards2080 hub boards180 Open Strip Shorted Strip “Pinhole” (short between implant and metal) Open bias resistor Open implant at via Open implant: Silicon Tracking System The Silicon Tracking System (STS) is the central detector of the Compressed Baryonic Matter (CBM) experiment at FAIR. Its task is the standalone trajectory reconstruction of the high multiplicities of charged particles originating from high- rate beam-target interactions. The silicon microstrip detectors must be radiation hard and are red out by a fast self-triggering front-end electronics. Quality Assurance Quality assurance for silicon sensor includes 1.Visual tests on arrival 2.Control & distribution to testing centers 3.Verification of specifications via tests 1.Electrical tests 1.Bulk IV & CV tests 2.Strip response 3.Inter-strip parameters 2.Radiation hardness tests 3.Bonding tests 4.Module tests 4.Central database for keeping track of sensor response Silicon microstrip sensors CBM01 1 st full-size prototype (2007) close-up of a corner of double-sided microstrip detector CBM01 (thickness 300 µm & strip pitch 58 µm) schematic view of silicon sensor with contacts pads & bias rail Strip Tests Electrical Tests Fig. 1. Counts v/s Channels pside nx0 Fig. 2. Counts v/s Channels pside nx2 Fig. 3. Distribution of Single Strip Amplitude Fig. 4. ADC without Baselines Laser Tests LED Tests With LED tests we investigate Sensor readout using infrared LED as light injector with FEE. Dead strips on sensor. LED’s used for sensors are: Infrared 1060nm (double sided) Red 660nm (single sided) Results shown are from a collimated 1060nm LED to a double sided silicon microstrip sensor illuminating 60 strips /side Pinhole testing schematic Pinhole test Scheme at Wafer prober Common strip failures & pinhole Semi-automatized using LabVIEW programs & Wafer prober Focuser CBM02 sensor Optical fiber Laser & optical fiber setup Laser Step Motor Focuser Optical Fiber Sensor ReadOut Station Box Interlock Optimization of focuser position With Laser tests we investigate Scanning sensor Strip integrity Detector response with mimicking 1MIP Charge sharing b/w strips Electrical tests include: 1.Bulk measurements 1.Leakage Current-Voltage (IV) 2.Capacitance-Voltage (CV) 2.Interstrip measurements 1.Resistance(Rint) 2.Capacitance (Cint) 3.Bias resistance (Rbias) 4.Coupling capacitance (Ccoup) 5.Current stability (IT) 6.Low Tempt. measurements Bulk capacitance Fig. 4. Lego plot of hit position : CBM02 Fig.3. Cluster amplitudes on nside: CBM02 Radiation damage Bias resistance Interstrip resistance Coupling capacitance Probe station Zuess 3000 Minimum Ionizing Particle (MIP) create ~ 22 ke - in our 300 µm thick silicon sensors, which corresponds to ≈ 180 ADC counts. The purpose of illuminating the double sided microstrip silicon sensor is to induce the same amount of charge as in case of a MIP. Based on the absorption of light in silicon, we selected infrared light (λ=1060 nm) which has absorption depth of ~500 µm in silicon. For the systematic evaluation of the performance of our sensors we used pulsed (~5 ns) infrared laser with a focused spot size ~15 µm. We have illuminated prototype sensor (256 strips/side) with the pulsed laser (~5 ns) and could focus the width of the laser spot to little more than one strip per side. The preliminary results are shown above. We are successful in inducing right amount of charge (22 ke - ). Fig. 3 shows a similar order of ADC counts as for MIPs. Cluster size is presented in Fig. 4. By illuminating a sensor by infrared light emitted by an LED it is possible to test the performance of all strips in one measurements. Fig. 1. ADC Counts/strip on nside: CBM02 Fig. 2. Cluster amplitude on nside: CBM02 Leakage current Quality assurance tests of silicon microstrip sensors for the CBM Experiment at FAIR Pradeep Ghosh, for the CBM Collaboration Goethe University, Frankfurt am Main, and GSI Helmholtz Center for Heavy Ion Research, Darmstadt