Solid State Detectors- 4

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Solid State Detectors- 4

• T. Bowcock

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Schedule

• 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

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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

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Example

• Choose a hostile environment
• LHCb detector

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LHCb detector
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B-hadron production
CP effects 10K events
About 1?1012 BB produced/year (108 Gen. 1)
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Vertex Detector

• Precision tracking that
• identification of B vertices
• measurement of lifetime (40fs)

Bs ? Ds K
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Geometry
Detectors separated 6cm during injection
small overlap
Positioning and movement to 5mm
10cm
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Radiation Environment

• Including effects of walls, vessel
• High doses at tips
• (1/r2)

cm
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Radiation Damage in Si

• Large amounts of radiation (neutron or MIP)
  introduces defects into the crystal
• More acceptors
• material switches to being p-type
• NeffNd-Na

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n-strip detectors
NeffNd-Na
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Radiation Damaged n-strip

• Depletion starts from side with strips
• We can run the detector underdepleted
• Full depletion voltage risesguess
• Many other effects are important

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Radiation Damage

• Damage increases the numbers of states in the
  band gap

conduction band
E
Ea
(p-type)
EEv
valence band
Distribution of energies and properties
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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

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Ballistic Deficit
Simulation-1D
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Picking the Technology

• n-strips or p-strips?

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Comparison of Technology
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n-strip prototypes

• design

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IV/CV and Noise
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Source Tests
Ru source
adc counts
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Testbeam
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Resolution
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Thickness

• Physics
• Signal
• Bias voltage
• depending on technology
• Current

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Fast Electronics
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Irradiation
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Irradiated Detectors
(V. Prelim) Irradiation at 31014
Irradiated (200V)
unirradiated
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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

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Current versus Temp
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Depletion Voltage v T
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Annealing
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Module Design
LHCbUK
Thermal Runaway
LHCb
thick detectors
Single Sided r and ? module
Thermal Model hold cooling at -10C
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Other factors

• Vacuum
• Inaccessibilty
• Replacement

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Mechanics
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Vertex Detector
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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