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Title page for ETD etd-12042008-130923


Type of Document Dissertation
Author Howe, Christina L
Author's Email Address ct27@msn.com
URN etd-12042008-130923
Title The Radiation Response of Focal Plane Arrays
Degree PhD
Department Electrical Engineering
Advisory Committee
Advisor Name Title
Robert A. Weller Committee Chair
Daniel M. Fleetwood Committee Member
Robert A. Reed Committee Member
Ronald D. Schrimpf Committee Member
Senta V. Greene Committee Member
Keywords
  • direct ionization
  • MRED
  • Monte Carlo
  • single event transient
  • focal plane array
  • energy deposition
  • Geant4
  • nuclear reactions
  • Focal planes -- Testing
  • Optical detectors -- Testing
  • Radiation hardening
  • Protons
  • Energy dissipation -- Mathematical models
Date of Defense 2008-11-21
Availability unrestricted
Abstract
Using Monte Carlo based simulations, the proton-induced energy deposition in a silicon PIN focal plane array was analyzed, and the importance of considering the materials surrounding a device was shown by comparing the results with experiment. This includes materials around all sides of the device, even those a centimeter away. During ground testing, caution must be used when setting up the experiment because dewar windows and mountings can also affect the amount of energy deposition observed in the device. Failure to include materials below a structure during simulation will result in an underprediction of the response for devices with high sensitivity to single events, such as detector arrays. This work shows that a high fidelity simulation is needed to estimate the energy deposited.

MRED (Monte Carlo Radiative Energy Deposition) simulations on a silicon imaging device show that direct ionization is the dominant mechanism for energy deposition below 350 keV in the focal plane detector considered here, while nuclear reactions dominate at higher energies. Even though direct ionization is the dominant mechanism, a constant LET and path length calculation does not address the fluctuations in dE/dx, only the variation in path length, and therefore does not capture the shape of the differential distribution. Modeling codes that use only a single value LET will fail to predict the response accurately. MRED simulations show that, when an isotropic beam is considered and an on-orbit event rate calculated, a simple structure including only one pixel and excluding surrounding materials to obtain error rate calculations is sufficient, with significantly improved accuracy over CREME96 calculations.

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