Silicon Tracking / Silicon Readout R&D

1. Silicon Tracking / Silicon Readout R&D Richard Partridge SLAC / Brown SLAC Annual Program Review

2. Overview • Silicon is the tracking technology best suited for the energy frontier • Best resolution for high momentum • Best 2-hit separation for tracking in the core of jets • Best time resolution for resolving beam crossing • SLAC has initiated a number of R&D efforts aimed at improving upon the current state of the art • Low-mass silicon strip detectors with bump bonded readout • High density bump bonded readout chips (KPiX) • Construction of a silicon lab at SLAC • Development of simulation tools for silicon tracker optimization • R&D is motivated by interest in a “Silicon Detector” for a future linear collider • Outcome of the R&D likely to have broader range of application SLAC Annual Program Review

3. Low Mass Sensor Design • Present generation silicon trackers compromised by tracker material • R&D at SLAC focused on a drastic reduction in material in the context of precision physics at a linear collider • Low duty cycle allows air cooling • Readout chip bump bonded to sensor • Carbon fiber support cylinders SLAC Annual Program Review

4. Double Metal Sensor R&D • Double metal sensor design aimed at radically reducing tracker material • Readout chip is bump bonded directly to the strip sensor • Second sensor metal layer used to route strip signals to readout chip • Prototype sensors have been procured from Hamamatsu • 20 full size sensors (93 x 93 mm2) • 40 small test sensors • 40 “charge division” sensors to test measuring coordinate || to strip Photograph of prototype double metal sensor SLAC Annual Program Review

5. Double Metal Sensor Module • Each of the 1840 readout strips is routed to a bump bond pad for attachment to the KPiX readout chip • Power, ground, clock, and data signals are brought to the sensor on a kapton cable • Routing of signals between cable and readout chip is done using the double metal layer • Critical system tests of sensor + readout + cable planned for the coming year SLAC Annual Program Review

6. KPiX Readout Chip • KPiX developed by SLAC with unique capabilities: • Designed for high channel count (1024/die) with bump bonding • Pulsed power minimizes power dissipation at low duty cycle • Four time-stamped buffers per channel during acquisition, readout at low power between bunch trains SLAC Annual Program Review

7. 0.25μm TSMC 32×32 array = 1024 channels Internal 13-bit ADC 4 Samples per train Automatic range switching Bias current for DC sensors Power down between trains Built-in calibration Nearest neighbor trigger High-gain feedback cap for tracker application Digital core with serial output External trigger for test beam Dual polarity for GEM / RPC KPiX64 single cell of KPiX 200 μm 500 μm KPiX Features SLAC Annual Program Review

8. KPIX Interface • Supports locally mounted KPIX for performance testing • KPIX show in copper container • Supports connection to external interface board • RPC interface board shown SLAC Annual Program Review

9. KPIX Data Acquisition • FPGA Control Board • USB Interface to PC • Future Upgrade To Ethernet • Interface To External Logic • Beam Line Triggers • Scintillator Triggers • Laser Triggers • Optically Isolated To KPIX Interface Board • C++ API Under Linux SLAC Annual Program Review

10. KPix Performance • Preliminary results meet expectations: for linearity, range switching, and noise • Next step is increasing channel count: 64  256  1024 SLAC Annual Program Review

11. Silicon Lab • SLAC is equipping a silicon lab to support broad range of silicon R&D efforts at SLAC • Facilities will include: • 500 ft2 clean room • Probe station in light box • Multi-sensor CMM • Laser test stand • Wire bonder • Glue station • Instrumentation (LCR, bias sources, etc.) • Lab space in building 84 has been cleared in preparation for clean room construction • Completion expected in FY09 SLAC Annual Program Review

12. Silicon Tracking Simulations • SLAC has been leading an effort to develop tracking simulation software expressly designed for the task of silicon tracker optimization • Simulation software goals: • Provide realistic simulations with full pattern recognition • Software must be sensitive to the tracker design details • Tracker geometry / configuration must be easy to change allowing rapid comparison of design alternatives • The tracking simulation infrastructure includes: • Flexible definition of detector geometry using xml text file • Detailed GEANT4-based modeling of detector response • Full simulation of charge collection in silicon strips and pixels • Robust track finding algorithms for pattern recognition studies SLAC Annual Program Review

13. Building a Virtual Tracker • Tracker geometry specified in an xml text file • Handles cylinders, disks, planar detectors, and polycones Example: Pinwheel outer barrel layer with full overlap in phi and z specified by the following xml code - <layer module="SiTrackerModule"> <barrel_envelope inner_r="1208.0" outer_r="1265.0“ z_length="3260.0" /> <rphi_layout phi_tilt="0.19" nphi="90" phi0="0.01745" rc="1228.0“ dr="0.0" /> <z_layout dr="5.5" z0="1581.0" nz="37" /> </layer> Additional xml lines describe the geometry of other layers and makeup of each module (layers of silicon, carbon fiber, kapton, epoxy, copper, rohacell foam, etc) SLAC Annual Program Review

14. 100% |cos q | = 0.99 Efficiency Polar Angle SiD Baseline Tracker Design Track Reconstruction Software • New tracking SW developed expressly for design studies • Handles any combination of pixel, axial strip, or stereo strip layers in barrel or disk geometry • Pattern recognition is agnostic as to sensor type  no coding of special cases for different combinations of sensor types • All decisions based on a global c2 no tuned parameters SLAC Annual Program Review

15. Tracking Simulations Status • Immediate goal is to optimize the SiD tracker design this summer in preparation for the SiD LOI • Also looking at simulating Atlas upgrade options to assist in the tracker upgrade design SLAC Annual Program Review

16. Summary • SLAC is engaged in an innovative silicon detector R&D program for next generation silicon trackers • R&D is motivated by the needs of a future linear collider, but the R&D is likely to have broader application to this key technology • Focus is on an innovative double metal sensor design that seeks to minimize tracker material and KPiX readout • Prototype sensors have been procured, KPiX64 is in hand, and a prototype cable is in the final design stage at U. New Mexico • System tests will be carried out during the coming year • A silicon lab is being equipped to support this program, as well as other silicon R&D taking place at SLAC • Tracking simulation software has been developed to assist in the optimization of silicon tracker designs SLAC Annual Program Review