Detectors for particles and radiation Advanced course for Master students

1. Detectors for particles and radiation Advanced course for Master students Spring semester 2010 S7139 5 ECTS points Tuesday 10:15 to 12:00 - Lectures Tuesday 16:15 to 17:00 - Exercises

2. Detectors for particles and radiation

3. Semiconductor Detectors

4. Conductivity

5. P-N junction: overview

6. Semiconductor Detectors

7. Drift velocity in Silicon

8. Charge diffusion in Silicon

9. Energy resolution: Fano factor

10. A "simple“ production sequence (schematic) Polished n-type silicon wafer (typical  ~ 1-10 Kcm )  Oxidation (800-1200°C)  Photolithograpy (coat with photo resist; align mask, expose to UV light, develop photoresist); Etching of oxide  Doping with boron and phosphorus by implantation (or by diffusion) Annealing to cure radiation damage and activate dopants - p+ n junction on front side - n n+ ohmic contact on back side •  Aluminize surface (e.g. by evaporation) •  Pattern metal for diode contacts Silicon Sensor Production

11. After all this - Why Silicon?

12. LHC: High resolution and high flux

13. LHC: High resolution and high flux

14. LHC: High resolution and high flux

15. Si strip detectors

16. Si strip detectors: single side strip readout

17. Si strip detectors: double side strip readout

18. Si strip detectors: spatial resolution

19. Si strip detectors: large systems

20. Si strip detectors: large systems

21. Si strip detectors: CMS tracker

22. Si strip detectors: CMS tracker

23. Si strip detectors: CMS tracker

24. Si strip detectors: CMS tracker barrel under construction

25. Si strip detectors: CMS detector from above

26. Si strip detectors: CMS tracker insertion

27. Si strip detectors: CMS tracker endcaps

28. 128 mm • Detector Modules - “Basic building block of tracking detectors” Silicon Sensors Mechanical support (cooling)Front end electronics and signal routing (connectivity) • Example: ATLAS SCT Barrel Module SCT = SemiConductor Tracker ASICS = Application Specific Integrated CircuitSTPG = Thermal Pyrolytic Graphite Detector Module Silicon sensors (x4)- 64 x 64 mm2-p-in-n, single sided - AC-coupled - 768 strips - 80m pitch/12mm width ASICS (x12) -ABCD chip (binary readout) - DMILL technology - 128 channels Wire bonds (~3500)-25 mm Al wires Mechanical support- TPG baseboard - BeO facings • ATLAS – SCT - 15.552 microstrip sensors-2.112 barrel modules - 1.976 forward modules - 61 m2 silicon, 6.3.106strips Hybrid (x1)- flexible 4 layer copper/kapton hybrid-mounted directly over two of the four silicon sensors - carrying front end electronics, pitch adapter, signal routing, connector s(rf) ~ 16 mm, s(z) ~ 850mm [NIMA538 (2005) 384]

29. Uses ultrasonic power to vibrate needle-like tool on top of wire. Friction welds wire to metallized substrate underneath. • Can easily handle 80m pitch in a single row and 40m in two staggered rows (typical FE chip input pitch is 44m). • Generally use 25m diameter aluminum wire and bond to aluminum pads (chips) or gold pads (hybrid substrates). • Heavily used in industry (PC processors) but not with such thin wire or small pitch. Wire bonding Microscope:connect sensor to fan-out circuit Electron microscope: bond “foot”

30. Si pixel detectors: CMS pixel

31. Si pixel detectors: Interconnection technology

32. Si pixel detectors: CMS pixel

33. Collected Charge for a Minimum Ionizing Particle (MIP) • Mean energy loss dE/dx (Si) = 3.88 MeV/cm 116 keV for 300m thickness • Most probable energy loss≈ 0.7 mean  81 keV • 3.6 eV to create an e-h pair  72 e-h / m (mean)  108 e-h / m (most probable) • Most probable charge (300 m)≈ 22500 e ≈ 3.6 fC Most probable charge ≈ 0.7 mean Mean charge The Charge Signal

34. Charge Collection time  Drift velocity of charge carriers v ≈E, so drift time, td = d/v = d/E Typical values: d=300 m, E= 2.5 kV/cm, with e= 1350 cm2 / V·s and h= 450 cm2 / V·s  td(e)= 9ns , td(h)= 27ns • Diffusion •  Diffusion of charge “cloud” caused by scattering of drifting charge carriers, radius of distribution after time td: with diffusion constant •  Same radius for e and h since td  1/ • Typical charge radius:  ≈ 6m, could exploit this to get better position resolution due to charge sharing between adjacent strips (using centroid finding), but need to keep drift times long (low field). Charge Collection time and diffusion

35. Si detectors: typical noise performance

36. Si strip detectors: spatial resolution

37. Si strip detectors: spatial resolution

38. Si strip detectors: spatial resolution

39. Si strip detectors: spatial resolution

40. Si pixel detectors: CMS pixel

41. Si pixel detectors: Other technologies: CCD

42. Si pixel detectors: CCD examples

43. Si pixel detectors: Drift chambers

44. Si pixel detectors: Monolithic pixel detectors

45. Pixel detector: Pilatus for X-ray crystallography (PSI)

46. Si tracking detectors: summary

47. Besides references given on the transparencies, the following sources have been used: References and Acknowledgements Silicon Detectors ICFA 03 School on Instrumentation in Elementary Particle Physics, Paula Collins, CERN Lectures on silicon detectors, Georg Steinbrück Hamburg University, August 15, 2008 Tracking with Solid State DetectorsMichael Moll, CERN – PH – DT2