1. 1 An introduction to radiation hard Monolithic Active Pixel Sensors Or: A tool to measure Secondary Vertices Dennis Doering*, Goethe University Frankfurt am Main on behalf of the CBM-MVD-Collaboration

2. 2 Outline - The challenge to measure Secondary Vertices - Operation principle of MAPS - Radiation damage effects - High Resistivity and radiation hardness - Conclusion An introduction to radiation hard Monolithic Active Pixel Sensors Or: A tool to measure Secondary Vertices

3. /17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 3 Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Reconstruction concept for open charm

4. /17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 4 Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Primary vertex Target (Gold) Reconstruction concept for open charm

5. /17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 5 Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Primary vertex Target (Gold) Reconstruction concept for open charm

6. /17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 6 Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Primary vertex Secondary vertex Short lived particle D 0 (c  = ~ 120 µm) Target (Gold) Reconstruction concept for open charm

7. /17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 7 Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Primary vertex Secondary vertex Short lived particle D 0 (c  = ~ 120 µm) Detector 1 Detector2 Target (Gold) z Reconstruction concept for open charm z= 5cm

8. /17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 8 Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Primary vertex Secondary vertex Short lived particle D 0 (c  = ~ 120 µm) Detector 1 Detector2 Target (Gold) z= 5cm Reconstruction concept for open charm 1) Short life time: - Good spatial resolution - low material budget (scattering) 2) Rare probe-> High statistics -Fast - Radiation hard

9. /17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 9 Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Primary vertex Secondary vertex Short lived particle D 0 (c  = ~ 120 µm) Detector 1 Detector2 Target (Gold) z Reconstruction concept for open charm 1) Short life time: - Good spatial resolution - low material budget (scattering) 2) Rare probe-> High statistics -Fast - Radiation hard Is it possible to develop such a detector?  MAPS in CBM @ FAIR z= 5cm

10. /17/25 Use digital cameras as particle detector Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 10 Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Primary vertex Secondary vertex Short lived particle D 0 (c  = ~ 120 µm) Detector 1 Detector2 Target (Gold) z Reconstruction concept for open charm 1) Short life time: - Good spatial resolution - low material budget (scattering) 2) Rare probe-> High statistics -Fast - Radiation hard Is it possible to develop such a detector?  MAPS in CBM @ FAIR z= 5cm

11. /17/25 Use digital cameras as particle detector: MAPS Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 11 Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) Primary vertex Secondary vertex Short lived particle D 0 (c  = ~ 120 µm) Detector 1 Detector2 Target (Gold) z Reconstruction concept for open charm 1) Short life time: - Good spatial resolution - low material budget (scattering) 2) Rare probe-> High statistics -Fast - Radiation hard Is it possible to develop such a detector?  MAPS in CBM @ FAIR z= 5cm

12. /17/25 Operation principle Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 12 SiO 2 N+P+ P- P+ Diode Epitaxial Layer P-Well Substrate e- N+ e- Particle

13. /17/25 Operation principle Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 13 SiO 2 N+P+ P- P+ Diode Epitaxial Layer P-Well Substrate N+ 50µm Thin and good spatial resolution 10-40µm => a few µm resolution

14. /17/25 Operation principle Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 14 SiO 2 N+P+ P- P+ Diode Epitaxial Layer P-Well Substrate N+ 10-40µm => a few µm resolution 50µm Compare HADES MWPC: Drift cell „pitch“: few 1000µm Resolution: few 100µm

15. /17/25 Radiation hardness? Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 15 Reconstruct up to 1000 tracks per collision and 10 10 collisions per year Fast readout and radiation hardness up to ~10 13 n eq /cm² and ~1 MRad Central Au + Au collision (25 AGeV)

16. /17/25 Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 16 Classesof radiation damage Classes of radiation damage To be investigated and improved: Radiation hardness against… … ionizing radiation: Caused by charged particles and photons Can ionize atoms and destroy molecules … non-ionizing radiation: Caused by heavy, charged and neutral, particles Atoms are displaced Farnan I, HM Cho, WJ Weber, 2007. "Quantification of Actinide α-Radiation Damage in Minerals and Ceramics." Nature 445(7124):190-193.

17. /17/25 Non-ionizing radiation (Low Resistivity) Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 17 SiO 2 N+P+ P- P+ Diode Epitaxial Layer P-Well Substrate N+ Defects generated by non-ionizing radiation. e-

18. /17/25 The history of radiation hard MAPS Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 18 Smaller pixel pitch => better radiation hardness

19. /17/25 High Resistivity Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 19 SiO 2 N+P+ P- P+ Diode Epitaxial Layer P-Well Substrate N+ e- depletion

20. /17/25 Non-ionizing radiation (High resistivity) Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 20 SiO 2 N+P+ P- P+ Diode Epitaxial Layer P-Well Substrate N+ depletion e-

21. /17/25 The history of radiation hard MAPS Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 21

22. /17/25 Beam test @ CERN by IPHC Strasbourg Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 22 Irradiated High Resistivity sensor: Better efficiency than unirradiated Low Resistivity sensor. Threshold Signal Noise

23. /17/25 Noise increases Sensor: - Mi-18 AHR, SB-Pixel, 10 µm pitch - Epitaxial layer: 400 W cm, 15 µm Irradiation: - fast reactor neutrons (Triga, Ljubljana) - Chip not powered during irradiation - Dose: 3 · 10 14 n eq /cm² + O(3 MRad) <20% less entries Thinner active vol.? CCE ok Gain ok Fe-55 (X-rays) Ru-106 (b-rays) 99% det. eff. after irrad. 620e (MPV) 490e (MPV) <20% less signal Thinner act. vol.? Noise increases => Compensate with cooling. 3 · 10 14 n eq /cm² + O(3 MRad) Not irradiated Limit of radiation hardness? 23 Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 Preliminary conclusion: Sensor tolerates 3 · 10 14 n eq /cm², to be confirmed in beam test

24. /17/25 -Forseen in ILC, STAR, CBM and ALICE -MAPS are the technology of choice for Open Charm in CBM -Requirements today not fully fulfilled, however ongoing research -Great improvements in the last few years and many ideas for future -Demonstrated excellent performance in beam test, even after 10 13 n eq /cm² -Sensor operational in laboratory even after 3·10 14 n eq /cm² Summary Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 24

25. /17/25 -Forseen in ILC, STAR, CBM and ALICE -MAPS are the technology of choice for Open Charm in CBM -Requirements today not fully fulfilled, however ongoing research -Great improvements in the last few years and many ideas for future -Demonstrated excellent performance in beam test, even after 10 13 n eq /cm² -Sensor operational in laboratory even after 3·10 14 n eq /cm² Summary Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 25 Conclusion: Monolithic Active Pixel Sensors A detector that YOU should know

26. /17/25 Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 26 BACK-UP

27. /17/25 Column parallel sensors Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 27

28. /17/25 Column parallel sensors Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 28 Readout speed achieved: <100µs Design goal for >2015: 30µs Maybe possible in future: <5µs