The Medipix3 and Timepix2 Chips

1. The Medipix3 and Timepix2 Chips Applications and Future Developments Richard Plackett, University of Glasgow VERTEX2010, Loch Lomond, 8th June 2010 On behalf of the Medipix Collaboration and Xavier Llopart in particular

2. Outline Current Detectors – Medipix2 and Timepix • Chip Descriptions • Principles of Operation Applications • Dosimitry, Education, Microscopy, Tracking, Photon Detection, Medical Imaging • Current Developments - Medipix3 • Chip Description • Development Issues • Future Projects – Timepix2 • Proposed Chip Designs and Ideas

3. Two Collaborations • Medipix2 • INFN Cagliari • CEA-LIST Saclay • CERN Geneva • University of Erlangen • University of Freiburg • ESRF Grenoble • University of Glasgow • University of Houston • IFAE Barcelona • Mid Sweden University • MRC-LMB Cambridge • INFN Napoli • NIKHEF Amsterdam • INFN Pisa • FZU CAS Prague • IEAP CTU Prague • SSL Berkeley • Medipix3 • ALMOF Amsterdam • University of Bogota • University of Canterbury NZ • CEA-LIST Saclay • CERN Geneva • DESY Hamburg • Diamond Light Source • University of Erlangen • ESRF Grenoble • University of Freiburg • University of Glasgow • ITER • University of Karlsruhe • Leiden University • Mid Sweden University • NIKHEF Amsterdam • IEAP CTU Prague • SSL Berkeley • VTT Microsystems 21 collaborating institutes

4. The Medipix Chips Silicon, 3D, CdTe, GaAs, Amorphous Silicon, Gas Amplification, Microchannel Plates etc… A philosophy of functionality built into the pixel matrix allows complex behavior with a minimal inactive region Configurable ‘shutter’ allows many different applications 55um square pixel matrix 256 by 256

5. Development Path Medipix1 1um SCAMOS 64 by 64 pixels Photon Counting Demonstrator (1997) Medipix2 250nm IBM CMOS, 256 by 256 55um pixels Full photon counting (2002) Timepix Analogue (ToT) and Time Stamping (ToA) (2006) 130nm IBM CMOS Photon Counting, Spectroscopic, Charge Summing, Continuous Readout (2009) Medipix3 Fast front end, Simultaneous ToT and ToA (2011) Timepix2 130nm/90nm/65nm Future LHCb readout – Data driven 40MHz ToT 12Gb/s per chip (2013) VELOpix 130nm/90nm/65nm Future Hybrid Pixel Time tagging layer for the LCD project (20??) CLICpix

6. Medipix2 and Timpix

7. Medipix2 (2002) – Photon Counting Each hit in the sensor is converted into a count in the 13 bit counter Noise and below threshold events are not counted at all 1000 electron noise floor sensor The shutter closes and the data are shifted out Analogue amplification Digital processing 3 1 1 2 1 2 Chip read-out

8. Medipix2 Applications • The most commercialized of the current chips and being sold by PANalytical (NL) in X-Ray Diffractometers • Also active applications in • Material Analysis • Medical Imaging • Synchrotron Light Source Instrumentation • Micro CT material analysis • Proton Beam Monitoring (at the SPS) • Electron microscopy • Mass spectrometry • Neutron Imaging • Charged Particle Dosimitry

9. Timepix (2006) Timepix design requestedand funded by EUDET collaboration Time over Threshold Time of Arrival Conventional Medipix2 counting mode remains. sensor Threshold Addition of a clock up to 100MHz allows two new modes. Time over Threshold Time of Arrival Threshold Analogue amplification Digital processing Pixels can be individually programmed into one of these three modes Time of Arrival counts to the end of the Shutter Time Over Threshold counts to the falling edge of the pulse Chip read-out

10. Or As Results… Time of Arrival Strontium Source Time over Threshold Ion Beams at HIMAC Charge deposition studies with various Isotopes Space Dosimetry Courtesy L. Pinsky, Univ. Houston

11. Timepix Applications As yet no one has sold any Timepix products, but lots of Interesting science is being done with them • New Tracking Technologies • LHCb Upgrade • CLIC detectors • Solid state Detector Development • TPC instrumentation • EUDET • Emission Channeling Crystal Lattice Experiments • ISOLDE • Image Intensifiers / Optical Photon Detectors • Adaptive Optics • Bioimaging • LHCb RICH • ToF Mass Spectrometry • Proteomic Imaging at AMOLF and Oxford • Imaging Mass Spec • Functional Cellular Biology at Kiev • Photo Electron Emission Microscopy and Low Energy Electron Micrsocopy • Neutron Monitoring at CNGS • Space Dosimintry • Education - CERN@School

12. Applications A few examples as shown at various Medipix Collaboration Meetings

13. LHCbTestbeam 6 pixel telescope planes angled in 2 dimensions to optimise resolution Fine pitch strip detector with fast electronics readout Device Under Test moved and rotated via remote controlled stepper motor

14. ATLAS Neutron Dosimitry LiF (50 µm) used for thermal neutrons detection PE (1.3 mm) used for fast neutrons detection Al (50 and 100 µm) used to stop lowenergyelectrons and photons PE + Al usedfor fast neutrons detectionremovinglowenergy electron photons contributions Uncovered accepts all particles lowsensibility to neutrons • J. Jakubek, S. Pospisil, M. Suk, D. Turecek • and Z. Vykydal and the Group at Prague CTU

15. CERN@ School / LUCID As a Teaching Aid – Americium Source • Langton Ultimate Cosmic-ray Intensity Detector • A space based directional cosmic ray experiment • Operated by Simon Langton Grammar School (Kent) • Joint project with CERN and SSTL • Launch 2011…. • CERN@School • Timepix chips in classrooms as ground based wide area cosmic ray detectors • Also excellent teaching aids for radioactivity • Possibility of loaning systems to schools • Feasible to construct remotely operated systems to log into Tape filter, only photons No filter, alpha particles and photons Half covered shows the difference

16. Low Energy Electron Microscopy MCP + CCD images Medipix2 Images Images of Graphene Flakes presented to the Medipix2 collaboration by I. Sikharulidze, Leiden ‘Medipix2 applied to low energy electron microscopy’, Ultramicroscopy 110 (2009) 33 - 35

17. Photon Detectors Medipix2 Funded Quad Phototube Four Timepix in a square phototube Collaboration between: Berkeley CERN Erlangen Glasgow Nikhef Glasgow HPD Many applications With VELOpix even LHCb RICH upgrade possbilities Berkeley MCP phototube

18. UA9 - Crystal Beam Channeling for sLHC Data and analysis by L. Tlustos on behalf of the UA9 collaboration

19. Dental Imaging Readout system, data analysis and teeth J. Jakubek, Prague CTU

20. Medipix3

21. Medipix3 (2009) • Increased pixel to pixel communication • Several advantages over Medipix2 • Charge summing mode • prevents spectral distortion due to charge sharing • Spectroscopicmode • four pixels to sharing thresholds and counters • Two counters per pixel • allowing continuous shutter based readout • Increased Radiation Tolerance • From 130nm CMOS process 17.3 mm 14.1 mm

22. Medipix3 Modes

23. Medipix3 Charge Summing Mode A hit in the sensor deposits charge sensor h+ The charge passes to the analogue amplifiers e- The Medipix 3 charge summing circuit operates Analogue amplification Digital processing The counter is iterated and read out with the shutter 10001110101 Chip read-out

24. Medipix3 Charge Summing Mode Medipix3 can be configured to sum charge across four pixel clusters to prevent hits being lost due to charge sharing A hit in the sensor deposits charge across four pixels The analogue comparators assign the charge to the pixel with the most hits This prevents ‘lost’ charge by partial hits not passing threshold 10001110101 The threshold is applied to the summed charge and read out when the shutter closes

25. Charge Summing Charge sharing events produce a low energy smearing of the landau Initial Measurements of Medipix3 indicate the charge summing circuitry works as expected Single pixel mode Charge Summing Mode Measurement by L.Tlustos and R. Ballabriga CERN

26. Spectroscopic (Colour) Mode • By connecting 4 pixels into a larger super pixel, eight threshold levels are available to us in the digital part of the pixel… Amplifier response Counter 1 Counter 2 Counter 3 Counter 4 Counter 5 Counter 6 Counter 7 Counter 8 • Each threshold is adjustable, allowing a wide range of settings. • This gives us enough flexibility to capture reasonable spectra in many different applications

27. Medipix3 Radiation Hardness • 130nm CMOS was expected to be very tolerant to integrated dose from test chip measurements • So far Medipix3 has been tested with an X-Ray flux up to 500MRad and has remained operational Noise Floor 400MRad Signal 460MRad

28. Medipix3 Matching Problems • One of the major debugging efforts in Medipix3 is a larger than expected pixel to pixel threshold variation • Especially obvious in charge summing mode • Design team in close contact with IBM to solve matching Issues

29. Can Still take Beautiful Images Image of a leaf with Fe55 source 930 e- minimum threshold Courtesy of R. Ballabriga - CERN

30. Medipix3 Applications • Multi-Energy CT • Spectroscopic Imaging mode • SLS instrumentation • Radiation tolerance and continuous readout • High Z Sensor Development (see David’s talk) • Charge summing to produce correct landaus • Beam Monitoring • Radiation Tolerance • Irradiated Sensor Development • Radiation Tolerance

31. Multi Spectral CT With thanks to University of Canterbury NZ and the MARS team

32. Timepix2

33. Timepix2 Proposals (2013?) • Timepix2 Design is still in flux • Simultaneous ToT and ToA • Sub 25ns rise time • Fast fine timing ~1ns • Many ideas for the remaining details • Possible data driven scheme akin to VELOpix allowing high readout rates and continuous sensitivity • Small pixels with highly configurable interconnects in an FPGA-like design • Shutter? Trigger? Frame based? Sparse Readout?

34. Data Driven Timepix2 • The ‘ideal’ detector will read out all hits… • An attempt to get close to this is the ‘Data Driven’ design • Will push all events off the chip up to a limiting event rate • Good for low rate and sparse applications • Problematic for SLS physics or high rate imaging • Cannot use the shutter to ‘squeeze down’ data rates • Closer to ideal but not useable for all applications • Requires significant on matrix logic and readout infrastructure to achieve high data rates

35. A Data Driven Timepix2 (VELOpix) • Limited to sparse readout • Super pixel architecture to compress clustered data on matrix • Very high maximum data rate A multi pixel cluster can be read out much more efficiently in a super pixel architecture However this is quite a strongly optimised design, possibly not ideal for all applications 220um Digital readout Analog DACs

36. An FPGA-Like Timepix2 • Small (27.5um) pixels, each with a clock, threshold and counter could be combined in a reconfigurable way A pixel that can measure ToT and ToA simultaneously, with deep counters Amplifier Amplifier Discriminator ToT / ToA / Count Discriminator ToT / ToA / Count A large area Timing pixel with a very deep counter Counter / Memory Counter / Memory High resolution ToT pixels for tracking Amplifier Amplifier Not Necessarily Technically Feasible Discriminator ToT / ToA / Count Discriminator ToT / ToA / Count Counter / Memory Counter / Memory Concept by J. Jakubek Prague CTU 55um

37. Timepix2 Possible Applications • Particle Tracking – LHCb, LCD interest • Molecular ToF spectrometry • TPC readouts • Neutron Dosimitry • Double Beta Decay & Neutrino Capture Experiments • …

38. To Conclude • Medipix2 and Timepix have been successful so far and built a large ecosystem of applications. • Medipix3 shows promise, initial verification complete and working with IBM to solve remaining problems. • Timpix2 is being designed/specified at the moment with a robust discussion about the required performance and how to achieve it.

39. Backup Slides

40. Chip Noise Details • Medipix2 noise floor 1000 electrons • Timepix 650 electrons • Medipix3 75 electrons

41. Timepix (2006) • An evolution of the Medipix2 chip • Similar architecture replacing a discriminator level with 100MHz clock signal and three operating modes • Each pixel is individually programmable into one mode • Time of Arrival – Time Tagging • Time over Threshold – Analogue Hit Information • Medipix - Hit Counting

42. Timepix Modes of Operation • ToT and ToA modes make use of the timepix clock to record the time between passing threshold and another event • Time Over Threshold counts to the falling edge of the pulse • Time of Arrival counts to the end of the Shutter Threshold

43. Medipix2 – Details • 256 by 256, 55um square pixels • Pixel columns read out as shift registers when shutter closes • ~1.5ms minimum full matrix readout • Noise floor ~1000e- • 3 bit threshold trim 16.1 mm 14.1 mm A Medipix2 wafer undergoing QA wafer probing