MOHAMAD KHALIL APC LABORATORY PARIS 17/06/2013 DSSD and SSD Simulation with Silvaco

Compton Telescope Concept Detector Design Simulations Outlook

Compton Telescope Concept

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 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 Classical Compton Telescope

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 Source Simulation

Detector Design

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, , 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, , Recent Progress

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 : 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 : Depletion voltage Electric Field shape Capacitance Leakage current Charge collection and charge sharing Double Sided Silicon Strip Detectors

DSSD Performance Simulation

SILVACO semiconductor simulation toolkit : 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 C++ generation engines Input to SILVACO Runtime: few seconds to tens of minutes Simulation Tools

Objective of the simulation 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 Simulation approach

Structure in 2D

Structure in 3D

Aluminum overhang

Depletion voltage

Depletion Voltage vs bulk concentration (or Resistivity)

Depletion voltage conclusions: Lowest bulk impurity concentration achievable 1, cm -3 (30 kohm.cm) Depletion Voltage vs bulk concentration (or Resistivity)

Depletion voltage

Depletion voltage conclusions: Lowest bulk concentration achievable Thicker detectors and/or lower ratios require more depletion voltage Depletion Voltage

Capacitance

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) conclusions

Leakage current

Capacitance

Leakage current

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 conclusions

Charge Collection

Increasing the voltage Dead Zones

Increasing the thickness Dead Zones

Increasing ratio Dead Zones

Increasing ratio Dead Zones

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 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 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

Outlook

A GEANT4 program: Can deploy multiple silicon layers (DSSD) of adjustable thicknesses and adjustable separations Photon source of adjustable energy GEANT4 output: Energy and position of the gamma ray interaction event 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 SILVACO Link with GEANT4

Probe Station

More tests on charge collection and dead zones Several available SSDs and DSSDs are available at APC and will soon be measured This will be vital to tune the simulation to have a better predictions for future DSSD demands (hidden parameters such has doping concentrations) A balloon flight Measuring the CRAB nebula polarization between 100 KeV and 300 KeV Foreseen in outlook

Thank You