1. Vittorio Palmieri 1 Cryogenic Operation of Si Detectors: the Lazarus Effect Vittorio Palmieri Laboratorium fuer Hochenergiephysik, Universitaet Bern, Sidlerstrasse 5, 3012 Bern, Switzerland on behalf of the CERN-RD39 Collaboration http://www.cern.ch/RD39

2. Vittorio Palmieri 2 Outline Properties of Si at cryogenic temperatures CCE of heavily irradiated Si detectors at cryogenic temperatures: 10 14 n/cm 2 10 15 n/cm 2 Neutralization of induced defects: the Lazarus effect Low cost “ohmic” devices Segmented devices: irradiated DELPHI module (5 10 14 n/cm 2 ) Low mass cooling Conclusions Future trends

3. Vittorio Palmieri 3 Properties of Silicon at Cryogenic Temperatures C. Canali et al., Phys. Rev. B 12 (1975) 2265 G. Ottaviani et al, Phys. Rev. B 12 (1975) 3318

4. Vittorio Palmieri 4 Radiation Hardness of Silicon at 300 K E. Borchi et al., Nucl. Phys. B (Proc. Suppl.) 61B (1998) 481 The ROSE Collaboration (RD48) Status Report, CERN/LHCC 97-39 1997

5. Vittorio Palmieri 5 1.2 10 14 n/cm 2 Irradiated Si Detectors Operated at 4.2 K, 77 K and 195 K Irradiated at room temperature at TAPIRO, ENEA Italy Stored at room temperature and bonded, therefore fully reverse annealed (RA) Material and process: –Al/n+/n/p+/Al1.8 k  cm

6. Vittorio Palmieri 6 I-V Characteristic 1.2 10 14 n/cm 2 RA

7. Vittorio Palmieri 7 M.I.P.s Signal Charge and Timing C. Da Via’ et al., Proc. of the International Conference on GaAs, Nucl. Instr. and Meth. in Phys. Res. A (1998) in press 77 K 50 V

8. Vittorio Palmieri 8 Charge Collection Efficiency C. Da Via’ et al., Proc. of the International Conference on GaAs, Nucl. Instr. and Meth. in Phys. Res. A (1998) in press 1.2 10 14 n/cm 2 RA

9. Vittorio Palmieri 9 2.2 10 15 n/cm 2 Irradiated Si Detectors Operated at 4.2 K, 77 K and 195 K Irradiated at room temperature at TRIGA, JSI Slovenia Stored at room temperature and bonded therefore fully reverse annealed (RA) Different materials and processes: –Al/n+/n/p+/Al 1.8 k  -cm O 2 –Al/n+/n/p+/Al 2.7 k  -cm

10. Vittorio Palmieri 10 I-V Characteristic 2.2 10 15 n/cm 2 RA

11. Vittorio Palmieri 11 M.I.P.s Signal Charge and Timing V.G. Palmieri et al., Nucl. Instr. and Meth. in Phys. Res. A 413 (1998) 475 77 K 250 V

12. Vittorio Palmieri 12 Charge Collection Efficiency 2.2 10 15 n/cm 2 RA V.G. Palmieri et al., Nucl. Instr. and Meth. in Phys. Res. A 413 (1998) 475

13. Vittorio Palmieri 13 The Lazarus Effect St. John at al., The Bible, New Testament, ~100

14. Vittorio Palmieri 14 Radiation Induced Defects in Silicon EcEc EvEv EfEf Electron Traps (Vacancies Related) V 6 very shallow C I C S (B) E c - 0.11eV0.38/cm VO E c - 0.17eV0.63 C I C S (A) E c - 0.17eV0.38 V2(=/-)+Vn E c -0.22eV0.96 V2(-/0)+Vn E c -0.40eV0.96 (Disappears after annealing) Holes Traps (Interstitial Related) C I E v +0.28eV1.5 (disappears after annealing) C I O I E V +0.36eV1.2 (depends on [C s ] and[O I ]) The ROSE Collaboration (RD48) Status Report, CERN/LHCC 98-39 1998

15. Vittorio Palmieri 15 The Lazarus Effect

16. Vittorio Palmieri 16 The CERN RD39 Collaboration

17. Vittorio Palmieri 17 Temperature Dependence Gennaro Ruggiero PRELIMINARY

18. Vittorio Palmieri 18 Voltage Dependence Gennaro Ruggiero PRELIMINARY

19. Vittorio Palmieri 19 1.0 10 15 n/cm 2 Irradiated Si “Ohmic Device” Irradiated at room temperature at TRIGA, JSI Slovenia Stored at room temperature and bonded (4min @ 80C = 2weeks at 300C) therefore fully RA Material and process: –Al/n+/n/n+/Al5 k  cm ++ + Before irradiation -+ + After irradiation

20. Vittorio Palmieri 20 I-V Characteristic Gennaro Ruggiero 1.0 10 15 n/cm 2 RA

21. Vittorio Palmieri 21 M.I.P.s Signal Charge and Timing Gennaro Ruggiero 77 K 250 V

22. Vittorio Palmieri 22 Charge Collection Efficiency 1.0 10 15 n/cm 2 RA Gennaro Ruggiero PRELIMINARY

23. Vittorio Palmieri 23 Liquid Nitrogen Cooling Non-flammable Non-toxic Easy to handle High cooling power Environmentally friendly Available everywhere

24. Vittorio Palmieri 24 RD39/COMPASS August Test Beam muon-beam COMPASS  -strips telescope RD39 cryostat DELPHI strips

25. Vittorio Palmieri 25 DELPHI Module Detectors: Hamamatzu 320  m 5.75 x 3.2 cm 2 3-6 Kohm cm p-side640 strips strip pitch 25  m r-o pitch 50  m n-side640 strips (p-stops) strip pitch 42  m r-o pitch 42  m Electronics:10 x MX6 128 input channels CMOS technology 2.5 MHz speed 1.5  s peaking time s/n degrades by 8.5% for every 100Gy of noise hybrid p-side n-side p-side mx6 V. Chabaud et al., CERN-PPE/95-86, 1995

26. Vittorio Palmieri 26 Irradiated (Dead) Detector Peter Chochula and Paula Collins 5 10 14 p/cm 2 NRA  Laser Scan

27. Vittorio Palmieri 27 Operation in the Cold hybrid p-side n-side mx6 Det 1 non-irr Det 2 5 10 14 p/cm 2 hybrid p-side n-side p-side mx6 beam 77K T hybrid D1 T hybrid D2 T bath Time (s) 2nd module on ! William Hamish Bell and Luca Casagrande Temperature (K)

28. Vittorio Palmieri 28 Back from the Dead Luca Casagrande and Paula Collins PRELIMINARY

29. Vittorio Palmieri 29 Temperature and Voltage Dependence T V 30V 110K 90V 125K 110K90V PRELIMINARY Luca Casagrande and Paula Collins

30. Vittorio Palmieri 30 Liquid Nitrogen Low Mass Cooling Cooling must be taken as an integral part of engineering (not an add-on) Power must be absorbed where it is produced –detector: < 1 µW/cm 2 –read-out: ~ 3 mW/strip Support structures: conduction is negligible if cooling is integrated Vacuum isolation is needed for a reliable low-mass system

31. Vittorio Palmieri 31 RD39 Module Tapio Niinikoski

32. Vittorio Palmieri 32 Conclusions Cryogenic cooling dramatically improves radiation hardness of silicon detectors After 10 14 n/cm 2 irradiation 100% CCE is achieved with only 50 V detector bias After 10 15 n/cm 2 irradiation a m.i.p., most probable signal of 13000 e, is measured at 200 V detector bias. This corresponds to 50% CCE No difference is found between room temperature and 195 K operation Detectors storage at room temperature slightly affect the results (many months) Cooling needed only during operation Similar results apply to segmented devices

33. Vittorio Palmieri 33 Future Trends Low mass cooling system for a full tracker (2  geometry) under construction Ohmic detectors could result in a much cheaper and more reliable solution Need for evaluation of performances of irradiated and non-irradiated FET electronics at cryogenic temperatures