Solid State Detectors 4 T Bowcock 1 Schedule

Solid State Detectors- 4 T. Bowcock 1

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

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 3

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

LHCb detector 5

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

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

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

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

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 10

n-strip detectors Neff=Nd-Na 11

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

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

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 14

Ballistic Deficit Simulation-1 D 15

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

Technology Options for LHCb Vertex Detector Comparison of pro Technology p strip n strip e p ty to o Pr 98 19 both con Single sided processing Reduced cost (30%)and ease of handling Rapidly falling efficiency below partial depletion Minimum pitch 12 m High field region on opposite surface to readout Thin detectors advantageous for multiple scattering Needs to be thinner for given operating voltage. (Lower signal) Handling(cost) of thin detectors. High efficiency at partial depletion gives lower operating voltage and lower power High field region (after irradiation) at readout strips. Lithographic processing of back (Cost and handling) Minimum pitch 40 m. Operating partially depleted at tip still allows full depletion (high CCE) elsewhere. Material Difficult to handle Charge Correlation Offset voltages on one side of detector for electronics. Thermal contact - sensitive face? 17

n-strip prototypes • design 18

IV/CV and Noise 19

Source Tests Ru source adc counts 20

Testbeam 21

Resolution 22

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

Fast Electronics 24

Irradiation 25

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

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 27

Current versus Temp 28

Depletion Voltage v T 29

Annealing 30

31

32

Module Design LHCb. UK Thermal Runaway LHCb Temperature at Tip (°C) 0 thick detectors -4 -8 0 50 100 150 200 250 W/mm 2 Single Sided r and module Thermal Model: hold cooling at -10 °C 33 300

Other factors • Vacuum • Inaccessibilty • Replacement 34

Mechanics 35

Vertex Detector 36

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 37