Solid State Detectors- 4

1. Solid State Detectors- 4 T. Bowcock

2. 1 Position Sensors 2 Principles of Operation of Solid State Detectors 3 Techniques for High Performance Operation 4 Environmental Design 5 Measurement of time 6 New Detector Technologies Schedule

3. Environmental Design • Design depends on environment the detector is to operate in and the physics • Many applications • Space Physics • Heavy Ions/Nuclear physics • High Energy Physics

4. Example • Choose a “hostile” environment • LHCb detector

5. LHCb detector

6. 32 2 B-hadron production CP effects 10K events About 11012 BB produced/year (108 Gen. 1)

7. Vertex Detector • Precision tracking that: • identification of B vertices • measurement of lifetime (40fs) Bs Ds K

8. series of 17 1/2 disks Geometry Detectors separated 6cm during injection small overlap Positioning and movement to 5mm 10cm

9. Dose after 1yr 1014 station 6 1 MeV equivalent neutrons/cm2 1013 1 2 3 4 5 6 Radiation Environment • Including effects of walls, vessel • High doses at tips • (1/r2) cm

10. Radiation Damage in Si • Large amounts of radiation (neutron or MIP) introduces defects into the crystal • More acceptors • material switches to being p-type • Neff=Nd-Na

11. n-strip detectors Neff=Nd-Na

12. Radiation Damaged n-strip • Depletion starts from side with strips • We can run the detector underdepleted • Full depletion voltage rises…guess • Many other effects are important

13. Radiation Damage • Damage increases the numbers of states in the band gap conduction band E Ea (p-type) E=Ev valence band Distribution of energies and properties

14. Trapping • In particular the effect of some of these defects is to introduce traps for the charge carriers in the depleted zone • The traps have lifetimes that increase(from ns to ms) with radiation dose and affect the pulse shape/diffusion

15. Ballistic Deficit Simulation-1D

16. Picking the Technology • n-strips or p-strips?

17. Technology Options for LHCb Vertex Detector procon p stripSingle sided processingRapidly falling efficiency Reduced cost (30%)and ease of handling below partial depletion Minimum pitch 12 m High field region on opposite surface to readout Thin detectors advantageous for Needs to be thinner for given multiple scattering operating voltage.(Lower signal) Handling(cost) of thin detectors. n strip High efficiency at partial depletion gives Lithographic processing of back lower operating voltage and lower power (Cost and handling) High field region (after irradiation) at Minimum pitch 40m. readout strips. Operating partially depleted at tip still allows full depletion (high CCE) elsewhere. bothMaterialDifficult to handle Charge Correlation Offset voltages on one side of detector for electronics. Thermal contact - sensitive face? Prototype 1998 Comparison of Technology

18. n-strip prototypes • design

19. IV/CV and Noise

20. Source Tests Ru source adc counts

21. Testbeam

22. Resolution

23. Thickness • Physics • Signal • Bias voltage • depending on technology • Current

24. Fast Electronics

25. Irradiation

26. Irradiated Detectors (V. Prelim) Irradiation at 3*1014 Irradiated (200V) unirradiated

27. Temperature • Important operating condition • leakage currents • defects dynamics are strongly temperature dependent • colder is not always better • Heat Management • electronics • ohmic heating in the detector

28. Current versus Temp

29. Depletion Voltage v T

30. Annealing

33. 0 -4 Temperature at Tip (°C) -8 0 50 100 150 200 250 300 W/mm2 Module Design LHCbUK Thermal Runaway LHCb thick detectors Single Sided r and  module Thermal Model: hold cooling at -10°C

34. Other factors • Vacuum • Inaccessibilty • Replacement

35. Mechanics

36. Vertex Detector

37. Summary • To design the detector you have to understand the environment • design the detector around the requirements • Radiation damage one of the key factors in modern experiments