Transcript Compton Telescope Motivation

DSSD and SSD Simulation
with Silvaco
MOHAMAD KHALIL
APC LABORATORY
PARIS 17/06/2013
Compton Telescope Concept
Detector Design
Simulations
Outlook
Compton Telescope Concept
Classical Compton Telescope
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Last decade:
• X-ray domain
• High and very high Ɣ-ray domains
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instruments: INTEGRAL, XMM-Newton, SWIFT,
Chandra, Fermi, HESS, MAGIC or VERITAS
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The 0,4-100 MeV range: Much less progress
• Difficulties in this energy range
• Minimal photon interaction probability
• Very high instrumental background induced by
Cosmic rays
• Best sensitivity made by the COMPTEL instrument
CGRO mission (1991 – 2000)
COMPTEL instrument: two separate detectors
• Scatterer
• Calorimeter
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Classical Compton Telescope
•
Last decade:
• X-ray domain
• High and very high Ɣ-ray domains
•
instruments: INTEGRAL, XMM-Newton, SWIFT,
Chandra, Fermi, HESS, MAGIC or VERITAS
•
The 0,4-100 MeV range: Much less progress
• Difficulties in this energy range
• Minimal photon interaction probability
• Very high instrumental background induced by
Cosmic rays
• Best sensitivity made by the COMPTEL instrument
CGRO mission (1991 – 2000)
COMPTEL instrument: two separate detectors
• Scatterer
• Calorimeter
•
Source Simulation
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Compton Imaging Technique:
• Pioneered by the COMPTEL instrument
• Scatterer
• Calorimeter
New Improvements :
• double-sided Si-strip tracking detectors (DSSD)
• No more need for a calorimeter (much lighter)
• fine spectral and position resolutions of modern Si
detectors => better detection efficiency
• Silicon has a high capability of measuring polarization
• Large field of view of Silicon
Detector Design
Recent Progress
• Silicon micro-strip detectors are widely used
for medical applications and in physics
experiments as instruments to measure the
position of a particle passing through the wafer
bulk of the silicon detector
•
Sadrozinski, H.F.-W. , Nuclear Science, IEEE
Transactions, 5752001 , 933 - 940
Recent Progress
• Silicon micro-strip detectors are widely used
for medical applications and in physics
experiments as instruments to measure the
position of a particle passing through the wafer
bulk of the silicon detector
•
Sadrozinski, H.F.-W. , Nuclear Science, IEEE
Transactions, 5752001 , 933 - 940
Double Sided Silicon Strip Detectors
• A high resistivity n-type Silicon bulk
• A set of heavily n-doped strips placed on
the top (n-side)
• A set of heavily p-doped strips on the
bottom (p-side).
• The p-side and n-side are perpendicular to
each other
Double Sided Silicon Strip Detectors
• DSSD as an ionizing chamber
• Localization in the XY-plane
• Energy deposition
Double Sided Silicon Strip Detectors
• DSSD as an ionizing chamber
• Localization in the XY-plane
• Energy deposition
Double Sided Silicon Strip Detectors
• What is a DSSD?
• DSSD as an ionizing chamber
• Localization in the XY-plane
• Energy deposition
• DSSD performance :
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Depletion voltage
Electric Field shape
Capacitance
Leakage current
Charge collection and charge sharing
Double Sided Silicon Strip Detectors
• What is a DSSD?
• DSSD as an ionizing chamber
• Localization in the XY-plane
• Energy deposition
• DSSD performance :
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Depletion voltage
Electric Field shape
Capacitance
Leakage current
Charge collection and charge sharing
DSSD Performance Simulation
Simulation Tools
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SILVACO semiconductor simulation toolkit :
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Devedit:a tool capable of defining the structure to be
simulated (2D and 3D)
Atlas: device simulator that predicts the electrical
behavior of semiconductor devices
Deckbuild: a runtime environment for Atlas
Tonyplot: a tool designed to visualize Tcad 1D, 2D
and 3D structures and solutions
http://www.silvaco.com/
C++ generation engines
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Input to SILVACO
Runtime: few seconds to tens of minutes
Simulation approach
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Objective of the simulation
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Depletion voltage
Electric Field shape
Capacitance
Leakage current
Charge collection and charge sharing
Main simulation parameters:
• Thickness
• Pitch and strip width to pitch ratio
• Doping concentrations
Structure in 2D
Structure in 2D
Structure in 3D
Aluminum overhang
Depletion voltage
Depletion voltage
Depletion voltage
Depletion Voltage vs bulk concentration (or Resistivity)
Depletion Voltage vs bulk concentration (or Resistivity)
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Depletion voltage conclusions:
• Lowest bulk impurity concentration achievable
• 1,3 1011 cm-3 (30 kohm.cm)
Depletion voltage
Depletion Voltage
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Depletion voltage conclusions:
• Lowest bulk concentration achievable
• Thicker detectors and/or lower ratios require more
depletion voltage
Capacitance
Capacitance
Capacitance
Capacitance
Capacitance
conclusions
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Depletion voltage conclusions:
• Lowest bulk concentration achievable
• Thicker detectors and/or lower ratios require more
depletion voltage
•
Capacitance conclusions:
• Depends primarily on the ratio (favoring lower ratios)
• Depends secondarily on the thickness and the pitch
(higher thicknesses and/or lower pitches)
Leakage current
Leakage current
Capacitance
Leakage current
conclusions
•
Depletion voltage conclusions:
• Lowest bulk concentration achievable
• Thicker detectors and/or lower ratios require more
depletion voltage
•
Capacitance conclusions:
• Depends primarily on the ratio
• Depends secondarily on the thickness and the pitch
•
Leakage current conclusions:
• Depends primarily on the thickness
• Depends on the applied voltage and the temperature
• Ratio has almost no effect
Charge Collection
Dead Zones
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Increasing the voltage
Dead Zones
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Increasing the thickness
Dead Zones
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Increasing ratio
Dead Zones
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Increasing ratio
conclusions
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Depletion voltage conclusions:
• Lowest bulk concentration achievable
• Thicker detectors and/or lower ratios require more
depletion voltage
•
Capacitance conclusions:
• Depends primarily on the ratio
• Depends secondarily on the thickness and the pitch
•
Leakage current conclusions:
• Depends primarily on the thickness
• Depends on the applied voltage and the temperature
• Ratio has almost no effect
•
Charge collection conclusions:
• Dead zones increase with the decrease of the ratio
• Beneficial to increase the thickness
Signal formation
•
Depletion voltage conclusions:
• Lowest bulk concentration achievable
• Thicker detectors and/or lower ratios require more
depletion voltage
•
Capacitance conclusions:
• Depends primarily on the ratio
• Depends secondarily on the thickness and the pitch
•
Leakage current conclusions:
• Depends primarily on the thickness
• Depends on the applied voltage and the temperature
• Ratio has almost no effect
•
Charge collection conclusions:
• Dead zones increase with the decrease of the ratio
• Beneficial to increase the thickness
Signal formation
•
Depletion voltage conclusions:
• Lowest bulk concentration achievable
• Thicker detectors and/or lower ratios require more
depletion voltage
•
Capacitance conclusions:
• Depends primarily on the ratio
• Depends secondarily on the thickness and the pitch
•
Leakage current conclusions:
• Depends primarily on the thickness
• Depends on the applied voltage and the temperature
• Ratio has almost no effect
•
Charge collection conclusions:
• Dead zones increase with the decrease of the ratio
• Beneficial to increase the thickness
Outlook
SILVACO Link with GEANT4
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A GEANT4 program:
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Can deploy multiple silicon layers (DSSD) of
adjustable thicknesses and adjustable separations
Photon source of adjustable energy
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GEANT4 output: Energy and position of the gamma ray
interaction event
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Used as input for SILVACO/C++ charge collection
simulation:
• Imitate a single event
• Imitate multiple synchronized or delayed events
• Monter-carlo simulation ?- Problems with
convergence for an extended simulation
Probe Station
outlook
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More tests on charge collection and dead zones
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Several available SSDs and DSSDs are available at APC and
will soon be measured
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This will be vital to tune the simulation to have a better
predictions for future DSSD demands (hidden parameters
such has doping concentrations)
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A balloon flight
• Measuring the CRAB nebula polarization between
100 KeV and 300 KeV
• Foreseen in 2016-2017
Thank You