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Radiation hardness studies with combined irradiated MAPS

Radiation hardness studies with combined irradiated MAPS Dennis Doering* 1 , Samir Amar-Youcef 1,3 ,Michael Deveaux 1 , Melissa Domachowski 1 , Ingo Fröhlich 1 , Christian Müntz 1 , Sarah Ottersbach 1 , Joachim Stroth 1 , Franz M Wagner 2

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Radiation hardness studies with combined irradiated MAPS

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  1. Radiation hardness studies with combined irradiated MAPS Dennis Doering*1, Samir Amar-Youcef 1,3,Michael Deveaux1, Melissa Domachowski1, Ingo Fröhlich1, Christian Müntz1, Sarah Ottersbach1, Joachim Stroth1, Franz M Wagner2 1 Goethe University Frankfurt am Main, 2 TU München, Forschungsquelle Heinz Maier-Leipnitz (FRM II), 3 Helmholtz Research School, Frankfurt • Outline • MAPS and combined radiation • Influence on leakage current, CCE and noise • - RTS as a fake hit source • - Fake hit rate after combined radiation • - Conclusion *doering@physik.uni-frankfurt.de

  2. Radiation hardness studies with combined irradiated MAPS The CBM Micro Vertex Detector based on MAPS The CBM-experiment (at FAIR) Expected radiation dose @MVD Expected radiation dose per CBM running-year: How does a sensor chip react on such radiation doses?

  3. Radiation hardness studies with combined irradiated MAPS Classesof radiation damage To be investigated and improved: Radiation hardness against… • … ionizing radiation: • Energy deposited into the electron cloud • Can ionize atoms and destroy molecules • Caused by charged particles and photons • … non-ionizing radiation: • Energy deposited into the crystal lattice • Atoms are 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.

  4. Radiation hardness studies with combined irradiated MAPS Operation principle of MAPS +3.3V Reset +3.3V Output SiO2 SiO2 SiO2 N++ N++ Diode P+ N+ P-Well P- Epitaxial Layer P+

  5. Radiation hardness studies with combined irradiated MAPS particle UK1 UK1 UK1 IReset UK2 UK2 UK2 ILeakage ISignal Threshold Measurement of leakage current Variation: Noise Operation principle of 3T-Pixel preamplifier UK 3 3.3V Reset- Transistor Hit identified! 2 K 1 C 0 Time CDS= UK1- UK2 2 Time

  6. Radiation hardness studies with combined irradiated MAPS Non-ionizing radiation Energy deposition into crystal lattice Radiation tolerance against non-ionizing radiation +3.3V Reset +3.3V Output SiO2 SiO2 N++ N++ P+ N+ P- P+

  7. Radiation hardness studies with combined irradiated MAPS immobile Leakage current due to non-ionizing radiation +3.3V Reset +3.3V Output SiO2 SiO2 N++ N++ P+ N+ P- P+ Leakage current due to defects of non-ionizing radiation

  8. Radiation hardness studies with combined irradiated MAPS Positive Charge Ionizing radiation Energy deposition into electron cloud Radiation tolerance against ionizing radiation +3.3V Reset +3.3V Output SiO2 SiO2 N++ N++ P+ N+ P- P+

  9. Radiation hardness studies with combined irradiated MAPS Positive Charge Leakage current due to ionizing radiation +3.3V Reset +3.3V Output SiO2 SiO2 N++ N++ P+ N+ P- P+ Leakage current due to ionizing radiation

  10. Radiation hardness studies with combined irradiated MAPS Non-ionizing radiation Energy deposition into crystal lattice Positive Charge Ionizing radiation Energy deposition into electron cloud Radiation tolerance against combined radiation +3.3V Reset +3.3V Output SiO2 SiO2 N++ N++ P+ N+ P- P+

  11. Radiation hardness studies with combined irradiated MAPS Positive Charge Combined radiation: Possible additional leakage current +3.3V Reset +3.3V Output SiO2 SiO2 N++ N++ P+ N+ P- P+ Possible additional leakage current due to combined radiation: - produced by defects of nonionizing radiation - transported by fields of ionizing radiation

  12. Radiation hardness studies with combined irradiated MAPS The measurement procedure Goal: distinguish leakage current caused by different damages Strategy: measure systematically leakage current of differently irradiated chips 1) Not irradiated => Reference 2) Irradiated with X-rays => Leakage current due to ionizing radiation 3) Irradiated with neutrons => Leakage current due to non-ionizing radiation 4) Irradiated with X-rays + neutrons => Leakage current due to combined radiation Working assumption: additional current = (4) - (2) - (3) + (1)

  13. Radiation hardness studies with combined irradiated MAPS Determination of the leakage current 27% 137% Bachelor Thesis Sarah Ottersbach 3T-Pixel/Mimosa19 • Additional leakage current component identified for combined irradiation • 27 % - 137% more than expected • Combined radiation damage effects orders of magnitude higher than single radiation are not found

  14. Radiation hardness studies with combined irradiated MAPS 3T Reset Transistor A short introduction into SB-Pixel • Advantages: • no reset cycle/dead time necessary • Continuous read-out • usable as particle detector • leakage current compensation

  15. Radiation hardness studies with combined irradiated MAPS 0 0 2.0 2.0 0.3 0.3 0.6 0.6 1.3 1.3 Radiation dose Radiation dose Charge Collection Efficiency and Noise SB-Pixel/Mimosa18 Decline of CCE, driven by non-ionizing radiation Increase of (shot) noise driven by ionizing radiation

  16. Radiation hardness studies with combined irradiated MAPS Fake Hit Rate and Random Telegraph Signal RTS is observed after irradiation with neutrons (non-ionizing radiation) Affected RTS pixels show excessive fake hit rates

  17. Radiation hardness studies with combined irradiated MAPS Fake hit rate of 3T and SB-pixel at -20°C and 20°C Preliminary Cooled irradiated SB-pixels show acceptable fake hit rate 400 k 40 k fake hits / frame 4 orders of magnitude Lower fake hit rate 4 k 0.4 k … Assume 400Mpixel in MVD

  18. Radiation hardness studies with combined irradiated MAPS 400 k 40 k fake hits / frame 4 k 0.4 k … CBM-Goal Combined damage effects and fake hits Preliminary 200 kRad ionizing radiation added to neutron irradiated sensors Bachelor Thesis Melissa Domachowski • Fake hit rate seems dominated by ionizing dose • Reasonably low rate is reached after cooling • Expect better results in radiation hardened sensors

  19. Radiation hardness studies with combined irradiated MAPS Summary • Combined radiation damage effects in MAPS were evaluated for the first time. • Combined irradiated produces an additional leakage current • CCE degradation is driven by non-ionizing radiation while noise is increased dominantly by ionizing radiation • Combined radiation damage effects orders of magnitude higher than single radiation are not found • RTS can be an important source of fake hits • Cooled SB-pixels seem to be a good strategy to suppress fake hits • Increase of fake hit rate is mainly caused by ionizing radiation • Outlook • Annealing studies are under preparation • Irradiation with different neutron energies are planned • Tests with higher ionizing dose are proposed Thank you for your attention

  20. Backup

  21. Radiation hardness studies with combined irradiated MAPS U2 IL IL t t IL Limitation in the detection efficiency for SB-RTS-pixels IC U2 U1 IL Constant threshold: => Quantitative identification of RTS pixels is not reliable for SB-pixels => Expect drop of identification efficiency with increasing leakage current

  22. Radiation hardness studies with combined irradiated MAPS The measurement procedure Leakage current measurements Lx Lnon-irr. xrays Lnonirr.+ionizing neutrons Lnonirr.+non-ionizing Lnonirr.+non-ionizing+ionizing xrays • - Feasibility to extract the leakage current contributions in detail • Feasibility to identify anomalous leakage current contribution due • to combined irradiation

  23. Radiation hardness studies with combined irradiated MAPS Fe-Spectrum 4 Pixel (EpiHit) 1 Pixel (DiodeHit)

  24. Radiation hardness studies with combined irradiated MAPS Cd-Spectrum

  25. Radiation hardness studies with combined irradiated MAPS Comparison Fe and Cd Three times as many electrons

  26. Radiation hardness studies with combined irradiated MAPS Non-ionizing radiation Energy deposit into crystal lattice Tolerance against non-ionizingg radiation +3.3V Output +3.3V GND SiO2 SiO2 GND SiO2 SiO2 N+ P++ P++ N++ P++ Bulk damage

  27. Radiation hardness studies with combined irradiated MAPS Tolerance against non-ionizing radiation +3.3V Output +3.3V GND SiO2 SiO2 GND SiO2 SiO2 N+ P++ P++ N++ P++ Not movable Signal lost due to rekombination Additional leakage current due to defects

  28. Radiation hardness studies with combined irradiated MAPS Positive Charge ionizing radiation Energy deposit into electron cloud Radiation tolerance against ionizing radiation +3.3V Reset +3.3V Output SiO2 SiO2 N++ N++ P+ N+ P- P+ Additional leakage by electrons from SiO2

  29. Radiation hardness studies with combined irradiated MAPS 1 0 0.3 0.6 2.0 0.6 1 200kRad 200kRad Signal to Noise at T=-20°C

  30. Radiation hardness studies with combined irradiated MAPS RTS of combined irradiated sensors Same pixel Xray + neutrons Only neutrons Peak not discussed here Unexpected: RTS-amplitude goes down by 47 ADC after irradiation with ionizing dose

  31. Radiation hardness studies with combined irradiated MAPS RTS in SB-pixel The pixel output (CDS) show only a few fake hits, which coincide with the RTS driven change in the absolute potential (F1)

  32. Radiation hardness studies with combined irradiated MAPS Assuming 400 Million pixel: 400 000 fake hit per frame expected Fake hit rate of 3T and SB-pixel at 0°C and 20°C Cooled SB-pixels show a satisfactory low fake hit rate

  33. Radiation hardness studies with combined irradiated MAPS Assuming 400 Million pixel: 400 000 fake hit per frame expected Fake hit rate of 3T and SB-pixel at 0°C and 20°C CBM-Goal Cooled SB-pixels show a satisfactory low fake hit rate

  34. Radiation hardness studies with combined irradiated MAPS Adding 200kRad ionizingradiation… Bachelor Thesis Melissa Domachowski Fake hit rate is dominated by ionizing radiation

  35. Radiation hardness studies with combined irradiated MAPS How to escape here? Diode 1 Diode 2 Sensors with improved charge collection efficiency The radiation hardness of MAPS is improved by fast charge collection Bigger collection diodes may improve CCE => Tested with Mi-19

  36. Radiation hardness studies with combined irradiated MAPS Mi-18 Mi-15 Mi-9 Mi-9 Mi-19 Tolerance against non-ionizing radiation Mi-18: 4 x 256 x 256 Pixels, standard diode (3 x 4 µm) Mi-19: 2 x 192 x 192 Pixels, L-shaped diode

  37. Radiation hardness studies with combined irradiated MAPS Results A. Büdenbender, Bachelor Thesis T= -20 °C Charge collection efficiency is indeed substantially increased But the bigger collection diodes generate more noise

  38. Radiation hardness studies with combined irradiated MAPS Insufficient S/N S/N of the sensors Use beam test results for non-irradiated chips. Add information on CCE from Fe-55 tests. Normalize collected charge according to CCE Checked against beam test data with Mi15 A. Büdenbender, Bachelor Thesis Both MIMOSA-18 and MIMOSA-19 seem fairly radiation hard Big diodes have no advantages because of high noise

  39. Radiation hardness studies with combined irradiated MAPS Results A. Büdenbender, Bachelor Thesis T= +20 °C Mi18 looses its advantage in noise after ~1013 neq/cm²

  40. Radiation hardness studies with combined irradiated MAPS S/N of the sensors Insufficient S/N A. Büdenbender, Bachelor Thesis At +20°C, the radiation hardness of Mi18 and Mi19 seems similar

  41. Radiation hardness studies with combined irradiated MAPS Leakage Current of Mimosa19, Diode 1 A. Büdenbender, Bachelor Thesis The increase of leakage currents is not negligable

  42. Radiation hardness studies with combined irradiated MAPS CCE of Mimosa19, Diode 1 A. Büdenbender, Bachelor Thesis The CCE depends on the temperature

  43. Radiation hardness studies with combined irradiated MAPS The Munich – Ljubljana puzzle We irradiated at the FRM-II reactor in Munich We irradiated at the Ljubljana triga reactor So what?

  44. Radiation hardness studies with combined irradiated MAPS CCE of Mimosa18 Munich - Ljubljana

  45. Radiation hardness studies with combined irradiated MAPS CCE of Mimosa18 Munich - Ljubljana

  46. Radiation hardness studies with combined irradiated MAPS Noise of MIMOSA-18, Munich - Ljubljana

  47. Radiation hardness studies with combined irradiated MAPS Signal over Noise of Mimosa18 T=-20°C Lines to guide the eyes Insufficient S/N Ljubljana neutrons seem roughly a factor 2 more damaging than Munich neutrons. Why?

  48. Radiation hardness studies with combined irradiated MAPS What means 1013 neq/cm²? My current understanding ~1.8e13n ~0.9e13n Ljubljana ~0.9e13n 1,1 25% 75%

  49. Radiation hardness studies with combined irradiated MAPS What means 1013 neq/cm²? My current understanding ~0.03e13 Munich ~0.97e13 1,0 3% 97% NIEL of both sources should be equal. But Ljubljana applies four times more neutrons. Mismatch could be caused by overlooked effect of slow neutrons. Neutron capture in boron doping?

  50. Radiation hardness studies with combined irradiated MAPS What means neutron capturing Alpha 6Li slow n + 10B +2.31 MeV

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