CMOS Monolithic Active Pixel Sensors A tool to measure open charm - PowerPoint PPT Presentation

CMOS Monolithic Active Pixel Sensors A tool to measure open charm particles M. Deveaux Goethe-Universität Frankfurt/M

Sherlock Holmes and Mystery of the Soup or How to build a webcam based carrot detector M. Deveaux Goethe-Universität Frankfurt/M

A Question to Sherlock Holmes Prof. Dr. Johanna Wanka, Federal The soup The cook Minister of Research, Germany M. Deveaux, FAIRNESS Workshop, 3. – 8. Sept 2012, Hersonissos, Greece 3

Sherlock Holmes Quest How can one check that the soup has cooked? M. Deveaux, FAIRNESS Workshop, 3. – 8. Sept 2012, Hersonissos, Greece 4

Sherlock Holmes Quest ? M. Deveaux, FAIRNESS Workshop, 3. – 8. Sept 2012, Hersonissos, Greece 5

Sherlock Holmes Quest M. Deveaux, FAIRNESS Workshop, 3. – 8. Sept 2012, Hersonissos, Greece 6

Sherlock Holmes Quest = M. Deveaux, FAIRNESS Workshop, 3. – 8. Sept 2012, Hersonissos, Greece 7

Sherlock Holmes Quest Dissolves fast Gets quickly soft if cooked Gets slowly soft if cooked M. Deveaux, FAIRNESS Workshop, 3. – 8. Sept 2012, Hersonissos, Greece 8

Sherlock Holmes Quest Lets test ingredients, which keep information on the cooking process. M. Deveaux, FAIRNESS Workshop, 3. – 8. Sept 2012, Hersonissos, Greece 9

Sherlock Holmes Quest Dissolves also at room temperature Keeps softening after cooking Reacts slowly, might overlook cooking M. Deveaux, FAIRNESS Workshop, 3. – 8. Sept 2012, Hersonissos, Greece 10

Sherlock Holmes Quest The Quest of modern heavy ion experiments We will have to test as many ingredients as possible to ob- tain a conclusive answer. CBM 11

What means soup: Hadronic Matter 12 M. Deveaux

What means carrot: Observables UrQMD transport calculation U+U 23 AGeV 13

My topic today How can this technology help to… in this! find this… Cent. AuAu coll. at 25 AGeV I. Vassiliev, C. Dritsa 160 p 400  - 400  + 44 K + 13 K - K - ( ūs ) D 0 ( cū ) π + (uđ) c t = 123 µm UrQMD + GEANT4 14 M. Deveaux

Why webcams? 15 M. Deveaux

Why webcams Add metall foil to deflect light A little radioactivity (Am-241, 60 keV photons work fine) 16 M. Deveaux

Why webcams? 17 M. Deveaux

How does a webcam work? +3.3V Reset +3.3V Output SiO 2 SiO 2 SiO 2 N++ N++ N+ P+ P- 50µm 15µm P+ 18 M. Deveaux

The pre-amplifyer Amplifier (Source Follower) Layout of a classical Active Pixel (simplified) 19 M. Deveaux

Operation principle of the pre-amplifyer Reset Water = positive charge Readout- electronik- Pixel- man capacitor- MIP-man basin Level indicator Photodiode- (Charge-voltage- tap converter) 20 M. Deveaux

Operation principle of the pre-amplifyer Readout cycle in three steps: First step: Readout-electronic-Man gives a Reset At a photodiode, once observes a leakage current. When the basin is fully recharged, the water level is noted for reference. 21 M. Deveaux

Operation principle of the pre-amplifyer Second step: Readout-elektronic-man has care for his other pixels now Sometimes MIP-man passes by to take bucket of positiv charge (electrons are collected by the diode after a hit). 22 M. Deveaux

The operation principle of the pre-amplifyer Third step: Readout-elektronik-man returns to check the water-level in the basin. ??? The level has dropped => MIP-man must have passed by. MAPS pixels may measure even if they are disconnected from readout electronics and power supply. 23 M. Deveaux

Some sources of uncertainty Shot noise: Number of fallen drops fluctuates over time. Gain of the indicator is Noise different for each pixel 24 M. Deveaux

Relation between model and schematics 25 M. Deveaux

Readout system of early MAPS Architecture of MIMOSA I X- and Y-shift registers to select pixels. IO-Signals needed: Clock, Reset, Synchro Common Amplifier and analogue output 26 M. Deveaux

Comparing pixel sizes State of the art Maps-pixel hybrid pixel (25 x 25 µm²) (100µm x 120 µm) Hybrid pixel Hybrid pixel Hybrid pixel 27 M. Deveaux

MAPS: The operation principle +3.3V Reset +3.3V Output SiO 2 SiO 2 SiO 2 N++ N++ N+ P+ P- 50µm 15µm P+ 28 M. Deveaux

The meaning of thin… Bending radius: ~30 cm Size: 21.2 x 10.6 mm 2 • 50 µm thickness • Bended due to inner tensions • Flexible silicon! 29 M. Deveaux

Open charm reconstruction: Concept z Reconstructing open charm requires: Target Detector2 • Excellent secondary vertex (Gold) Detector 1 resolution (~ 50 µm) => Excellent spatial resolution (~5 µm) => Very low material budget (few 0.1 % X 0 ) Primary Beam: 25 AGeV Au Ions (up to 10 9 /s) => Detectors in vacuum Primary • A good time resolution to distinguish Secondary vertex vertex the individual collisions (few 10 µs) Short lived particle D 0 (c t = ~ 120 µm) • Very good radiation tolerance Reconstruction concept for open charm (>10 13 n eq /cm²) Central Au + Au collision (25 AGeV) 30 M. Deveaux,

Established pixel detector technologies (2003) NA60 hybrid pixel Required Hybrid CCD (CBM) pixels Single point res. [µm] ~ 5 ~ 30 ~ 5 Material budget [ X 0 ] ~ 0.3% 1% ~0.1% Time resolution [µs] few 10 0.025 ~100 > 10 13 >> 10 14 << 10 10 Rad. hardness [n/cm²] 31 M.Deveaux

Requirements vs. detector performances (2003) We need both More sensitivity More statistics NA60 hybrid pixel Required Hybrid CCD pixels Single point res. [µm] ~ 5 ~ 30 ~ 5 Material budget [ X 0 ] ~ 0.3% ~ 1% ~ 0.1% Time resolution [µs] few 10 0.025 ~100 > 10 13 >> 10 14 << 10 10 Rad. hardness [n/cm²] 32 M. Deveaux

Performances of MAPS (2003) MAPS provide an unique compromise between: • sensitivity • high rate capability Required Hybrid CCD MAPS** pixels (2011) Single point res. [µm] ~ 5 ~ 30 ~ 5 3.5 Material budget [ X 0 ] ~ 0.3% 1% ~0.1%* ~0.05%* Time resolution [µs] few 10 0.025 ~100 ~10000 > 10 13 >> 10 14 << 10 10 > 10 12 Rad. hardness [n/cm²] *Sensor only **Best of all prototypes 33

Easy, isn’t it? X 0 ? n eq /cm² ??? 34 M. Deveaux

X 0 and multiple scattering Definition of the radiation length (X 0 ): • Distance in a material, which decelerates charged particles with to 1/e of its energy. • Material constant, tables available at http://pdg.lbl.gov Relevance of the radiation length (X 0 ): x Uncertainty range 1) The thinner, the better. 2) 1% X 0 = 1mm silicon 35 M. Deveaux

What means n eq /cm²? Relative non ionising dose of neutrons and pions 2,0 Neutrons 1,5 Pions eq ] NIEL - Factor [n 1,0 0,5 Data from: A. Vasilescu and G. Lindstroem, Displacement damage in Silicon on-line compilation: http://sesam.desy.de/~gunnar/Si-dfuncs 0,0 0,1 1 10 100 1000 10000 E kin [MeV] 36

Radiation tolerance 37

What about radiation hardness? Ionising radiation: • Energy deposited into the electron cloud • May ionise atoms and destroy molecules • Caused by charged particles and photons Non-ionising radiation: • Energy deposited into the crystal lattice • Atoms get displaced • Caused by heavy (fast leptons, hadrons) charged and neutral particles Farnan I, HM Cho, WJ Weber, 2007. "Quantification of Actinide α -Radiation Damage in Minerals and Ceramics." Nature 445(7124):190-193. 38 M. Deveaux

Sensor R&D: Tolerance to non-ionising radiation +3.3V Output +3.3V GND SiO 2 SiO 2 GND SiO 2 SiO 2 N+ P++ P++ N++ P++ 39

Sensor R&D: Tolerance to non-ionising radiation +3.3V Output +3.3V GND SiO 2 SiO 2 GND SiO 2 SiO 2 N+ P++ P++ N++ P++ Key observation: Signal amplitude is reduced by bulk damage 40

Sensor R&D: Tolerance to non-ionising radiation +3.3V Output +3.3V GND SiO 2 SiO 2 GND SiO 2 SiO 2 N+ P++ P++ N++ P++ E Electric field increases the radiation hardness of the sensor Draw back: Need CMOS-processes with low doping epitaxial layer 41

Sensor test and plots: AG Stroth, IKF Frankfurt/M Sensor design: PICSEL Group, IPHC Strasbourg, et al. S/N of MIMOSA-18 AHR (high resistivity epi-layer) Mimosa-9 (2005) T=-34°C/-70°C D. Doering, P. Scharrer, M. Domachowski 20 µm standard epi 80 Signal to Noise (Ru-106 ) 70 10µm 12.5µm 60 25µm 50 40 30 Safe operation 20 10 0.2 x 10 13 n eq /cm² 0 0 5 10 15 20 25 30 13 n eq /cm 2 ] Radiation dose [10 Plausible conclusion: Radiation tolerance ~10 14 n eq /cm² reached • Cooling required to operate heavily irradiated sensors 42 M. Deveaux

Sensor test and plots: AG Stroth, IKF Frankfurt/M Sensor design: PICSEL Group, IPHC Strasbourg, et al. Noise and cooling Unirradiated 60 14 n eq /cm 2 10 55 14 n eq /cm 2 50 3·10 45 40 Noise [e] 35 t Int = 4 ms (slow) Radiation 30 damage 25 20 15 10 5 -3 -27 -34 -15 Temperature [°C] Cooling is needed to exploid the improved radiation tolerance Alternative solution: Fast integration times help 43 M. Deveaux