Solid State Detectors- 4 T. Bowcock

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

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 B-hadron production 32 2  CP effects 10K events About 1  BB produced/year (10 8 Gen. 1)

7 Vertex Detector Precision tracking that: –identification of B vertices –measurement of lifetime (40fs) B s  D s K

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

9 Radiation Environment cm MeV equivalent neutrons/cm station 6 Dose after 1yr Including effects of walls, vessel High doses at tips –(1/r 2 )

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 –N eff =N d -N a

11 n-strip detectors N eff =N d -N a

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 E conduction band valence band E=E v EaEa (p-type) 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 Comparison of Technology Technology Options for LHCb Vertex Detector procon p strip Single sided processing Rapidly 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 forNeeds to be thinner for given multiple scatteringoperating voltage.(Lower signal) Handling(cost) of thin detectors. n strip High efficiency at partial depletion givesLithographic 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. both MaterialDifficult to handle Charge CorrelationOffset voltages on one side of detector for electronics. Thermal contact - sensitive face? Prototype 1998

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 Irradiated (200V)unirradiated (V. Prelim) Irradiation at 3*10 14

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

31

32

33 Module Design  W/mm Temperature at Tip (°C) Thermal Model: hold cooling at -10 ° C Thermal Runaway LHCb thick detectors Single Sided r and  module LHCbUK

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