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 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

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

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

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

/17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct 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

/17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct 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

/17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct 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

/17/25 Task: Reconstruct Secondary Vertices Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct 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 FAIR z= 5cm

/17/25 Use digital cameras as particle detector Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct 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 FAIR z= 5cm

/17/25 Use digital cameras as particle detector: MAPS Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct 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 FAIR z= 5cm

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

/17/25 Operation principle Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct 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

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

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

/17/25 Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct 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, "Quantification of Actinide α-Radiation Damage in Minerals and Ceramics." Nature 445(7124):

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

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

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

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

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

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

/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 · 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 · n eq /cm² + O(3 MRad) Not irradiated Limit of radiation hardness? 23 Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct Preliminary conclusion: Sensor tolerates 3 · n eq /cm², to be confirmed in beam test

/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 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

/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 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 Conclusion: Monolithic Active Pixel Sensors A detector that YOU should know

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

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

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