MEDIPIX AND TIMEPIX CHIP DEVELOPMENTS Recent Measurements with Timepix as a Particle Tracker Richard Plackett – CERN Medipix Group VERTEX 2009, Mooi Veluwe, 16th September ‘09 Overview Introduction Timepix LHCb Upgrade Introducing the Medipix 2 and Timepix Chips Timepix and Time over Threshold Mode Recent LHCb VELO upgrade Testbeam results Testbeam Telescope -2- Timepix Particle Telescope Hybrid Pixel Detectors Ionizing Particle Introduction Timepix sensor h+ e- LHCb Upgrade Solder bump bonds Testbeam Telescope Positive or negative sensor bias Analogue amplification Digital processing Readout Chip Medipix or Timepix in 250um IBM CMOS Chip read-out -3- Medipix2 Single photon counting readout provides low noise, high contrast images with very high dynamic range Introduction Timepix LHCb Upgrade Testbeam Telescope 55um pixel matrix (256 by 256) reading Si, 3D, CdTe, GaAs sensors -4- Configurable ‘shutter’ allows many different applications Timepix Introduction Timepix LHCb Upgrade • • • • Timepix is a derivative of Medipix2 Addition of a global clock (up 100MHz) which is propagated to every pixel Originally conceived for GEM foil detectors The clock can be used for Time of Arrival (ToA) and Time over Threshold (ToT) modes. Testbeam Telescope Time of Arrival Mode • • -5- Counts from passing threshold to closing shutter Allows accurate timing of hits in individual pixels Threshold Timepix Time over Threshold Timepix ToT mode is similar in principle to ATLAS pixel.. Introduction Preamp has fast rise (90ns) but slow (500ns -2500ns) constant current return to zero Timepix LHCb Upgrade Testbeam Threshold Telescope Clock Linearity of one pixel measured at three different threshold values E.g. 20ke- ~1us = 40 x 25ns Residual errors come from non linearity with small charge signals and a slow return to baseline -6- Timepix GEM foil event Introduction Timepix LHCb Upgrade A GEM foil event with a ‘chess board’ ToT & ToA pattern set on the pixel matrix ToT ToA Testbeam Telescope DESY testbeam in November 2006 (A.Bamberger et al) -7- ToT silicon event Introduction Timepix LHCb Upgrade Testbeam Telescope Images courtesy of Erik Heijne Although conceived for gas detectors Timepix retains the Medipix2 sensor features eg Pixel leakage current correction Positive and negative biasing -8- Upgrading LHCb Introduction Timepix LHCb Upgrade Testbeam Telescope The Problem: LHCb is currently optimised for single interactions, to search for new physics a large increase in statistics is required, significantly complicating the trigger. HCAL ECAL RICH2 Tracker Magnet TT RICH1 The idea: Aim to operate at L=2.1033 Perform entire trigger on CPU farm. No hardware Trigger! In Addition: The consequence: A strong case for an upgrade even without SLHC as LHCb does not use all current LHC luminosity Read out all sub-systems at 40 MHz Replace all FE-electronics; all silicon modules, RICH-HPDs, FE boards of Calorimeter, Outer Tracker FE -9- Muon 10x increase in Leptonic channels 20x increase in Hadronic channels For more information on LHCb upgrade see the talk tomorrow by JC VELO LHCb VELO Upgrade Introduction Timepix LHCb Upgrade Closest LHC detector to the beam and highest resolution requirements Currently 21 perpendicular two sided strip planes Upgrade to strip or pixel system Testbeam Telescope silicon edge just 7 mm from beam! -10- Potential Module Design Silicon (1-3 pieces) 55x55 mm 10 Timepix chips pixels, 800 mm pixels in areas (periphery indicated in white) under chip periphery Diamond thermal plane with cutouts immediately above TSV regions Introduction Timepix LHCb Upgrade Testbeam Telescope Cooling channel Power strips and signal routing area With a Pixel VELO we can have a low scattering module with high resolution and no strip detector ambiguities -11- Recent Testbeam Activity Timepix • • • Required to demonstrate suitability for tracking Measure efficiency and resolution Provide information for VELOPIX design LHCb Upgrade • 3 testbeams at CERN SPS with 120GeV Pions Introduction Testbeam – – – June: as Medipix Group to test Telescope concept July: Running parasitically from CMS SiBit telescope August: Running parasitically from EUDET/LCFI testbeam Telescope • -12- Significant improvements to telescope design at each testbeam Timepix Telescope 4 Timepix, 2 Medipix planes in telescope Introduction Timepix LHCb Upgrade Symmetric positioning of planes around Timepix DUT Telescope planes mounted at nine degrees in x and y Testbeam Telescope DUT position and angle controlled remotely by stepper motors -13- Measurements of resolution with angle, threshold, sensor bias, 3D sensor and timewalk Angled Planes to Boost Resolution Hits that only affect one pixel have limited resolution (30um pixel region) Introduction Timepix Angling the sensor means all tracks charge share and use the ToT information 55um LHCb Upgrade Testbeam 300um 10o Telescope -14- Timepix (ToT) tracked position vs cluster reconstructed position Results – Resolution Vs Track Angle Introduction Timepix LHCb Upgrade Testbeam Rotation about Y axis Telescope 2.5um Estimated track contribution to residual PRELIMINARY: UNCALIBRATED DATA!! -15- The tracking uncertainty of the telescope is very competitive, with uncalibrated, uncut data, 2.5um is comparable to EUDET running with 30um pixels (timepix is 55um) Results - Residual Width vs Sensor Bias The residual width shows a clear dependence on orientation as the Introduction sensor bias is changed. Timepix LHCb Upgrade Testbeam Telescope This is as expected, and illustrates the sensitivity of the measurement The sensor bias was scanned up and down again to ensure any change seen was not a drift Perpendicular: As the charge diffusion shrinks you have more single pixel hits, increasing the width of the residual width -16- Width of y residual perpendicular Width of x residual 18 degrees High Angle: As the charge diffusion shrinks you still have a large number of charge sharing hits, holding residual width constant Results – Residual Mean vs Sensor Bias Varying the sensor bias shows a clear shift in the residual means for highly angled tracks Introduction Timepix LHCb Upgrade 6 degrees 18 degrees perpendicular perpendicular angled Testbeam angled Telescope Perpendicular: As the charge collection shrinks you do not affect the position of the reconstructed hit -17- High Angle: As the charge collection shrinks you can see the position of the reconstructed hit being pulled Results – 3D Sensors Efficiency Glasgow double sided CNM sensor Introduction Timepix LHCb Upgrade Testbeam Telescope Perpendicular particles passing through a doped hole will deposit less charge in the silicon The sub-pixel resolution of the telescope allows us to see the efficiency losses due to the anode and cathode holes in the silicon. -18- Special acknowledgement to Marco Gersabeck who produced this plot and the 3D group at Glasgow who provided the sensor Design Lessons for VELOPIX • Analogue IS better than Binary, even with 55um pixels, even with clusters and charge sharing Timepix • Clustering WILL significantly increase hit multiplicity LHCb Upgrade • Interactions within the sensor will occur often and need to be handled to avoid overflowing the chips for that event • From this data we will determine how many bits ToT we need and optimise on chip the data transport Introduction Testbeam Telescope Timepix (ToT) -19- 5um Medipix (binary) 11um More Measurements Coming Soon Lots of data from July and august still to analyse Introduction • – – – Timepix LHCb Upgrade Testbeam Telescope Resolution as a function of threshold 2d rotation Number of bits used • Efficiency and Noise study • Pulse shape reconstructed directly from ToT data • Timewalk measurements • 3d sensor -20- • Vertex reconstruction using telescope • Etc… Also gain calibration still has to be done with to get optimum performance from TImepix chips In Conclusion • The Medipix2 and Timepix chips are versatile creatures, and are spinning back into HEP • A Timepix like chip is a candidate for LHCb VELO upgrade • At testbeams over the summer Timepix has been demonstrated to run reliably with unexpectedly good resolution • A very large data set has been recorded so expect nonpreliminary results soon… • A series of telescopes were developed for these tests. A possible future system could be made available to the community if there is interest … another couple of slides on that … Introduction Timepix LHCb Upgrade Testbeam Telescope -21- Current Telescope • Successful going on to do a testbeam with SPS collimators • All versions based on the USB interface developed by CTU Prague • Main strength is simplicity, each module powered, biased and read out by USB. DAQ consists of 6 usb lines to a PC and a NIM crate for a pulse-per-second synchronization signal • Data is saved to text files so extremely easy to work with Sensor Bias Introduction Timepix LHCb Upgrade Testbeam Telescope timing -22- USB Limitations • Timing between modules has large uncertainty (500ns) due to the USB readout systems LHCb Upgrade • Long readout dead time (1 second), due to USB 1.1 readout Testbeam • Either ToT or ToA, as limited number of Timpix chips • Inclined sensor planes good for ToT, bad for ToA as charge sharing clusters can cause timewalk • At current resolution (~2.5um) scattering from PCB is becoming a dominant error Introduction Timepix Telescope -23- Future Timepix Telescope Introduction Timepix LHCb Upgrade Testbeam Telescope -24- Solution… • Add an external timing readout to sync systems (and scintillators?) • Replace USB with RUIN, Relaxed or similar (coming soon) allows 100x faster readout over (USB2 or Ethernet) • 4 Timepix chips per arm, with one dedicated to ToA • New PCB with cut out behind chip • Possible further upgrade with Timepix2….. Future Timepix Telescope Introduction Timepix LHCb Upgrade Testbeam Results in • High resolution (<3um) as current telescope • Track timing down to 10ns • Link to PMT/external device for trigger and integration of DUTs • Minimum rate 100Hz, max 20kHz • Portable device with text file data output as current telescope • If anyone is interested please let me know Telescope DUT RUIN -25- RUIN TIMING With Thanks… Introduction Timepix LHCb Upgrade Testbeam Telescope -26-