1. Measurement and Simulation of the Variation in Proton-Induced Energy Deposition in Large Silicon Diode Arrays Christina L. Howe 1, Robert A. Weller 1, Robert A. Reed 1, Brian D. Sierawski 2, Paul W. Marshall 3, Cheryl J. Marshall 4, Marcus H. Mendenhall 5, Ronald D. Schrimpf 1, and J. E. Hubbs 6 1. Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37235 2. Institute for Space and Defense Electronics, Vanderbilt University, Nashville, TN 37235 3. Consultant, Brookneal, VA 24528 4. NASA-GSFC, Greenbelt, MD 20771 5. Free-Electron Laser Center, Vanderbilt University, Nashville, TN 37235 6. Ball Aerospace & Technologies Corp., Albuquerque, NM 87117

2. Outline Background Motivation Experimental Setup Modeling Description Results –Simulation compared with experimental results –Contribution from reaction mechanisms –Event rate calculation Conclusions christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays

3. Background Focal plane arrays (FPAs) often used on satellites planned for long orbits in harsh proton environments FPAs Advantages –Flexible, reliable, low cost, high-density resolution, on- chip signal processing, and more radiation tolerant to protons than charge coupled devices (CCDs) Detector Array In ROIC christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays Basic hybrid FPA

4. Motivation Proton events contribute to device noise floor Better understanding of how radiation-induced energy deposition occurs will improve prediction techniques Accurate modeling helps predict on-orbit response We will show a high-fidelity prediction method based on Monte Carlo simulations and a mathematical model christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays http://sohowww.nascom.nasa.gov/gallery/Movies/flares.html

5. Experimental Setup Hybrid FPA consisting of a silicon p-i-n 128 × 128 detector array with hardened CMOS readout integrated circuit (ROIC) Full radiometric characterizations were performed –Dark current, noise, responsivity, and sensitivity Irradiated with 63 MeV protons at 45° Biased to 15V resulting in full depletion Exposed at 233 K christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays

6. Modeling Description MRED (Monte Carlo Radiative Energy Deposition), a GEANT4 based tool, used for simulation Sensitive Volume 45° 63 MeV Proton christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays TCAD simulations revealed RPP assumption was sufficient to estimate device response to radiation

7. Modeling Description Each event in Monte Carlo simulation represents only one primary particle hit one pixel, but… –Non-negligible probability of multiple hits on a single pixel (pile up) exists –Non radiation induced noise in experimental data christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays

8. Pile Up christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays µ = 0.08 σ NOISE = 3 Before Pile Up After Pile Up

9. Results Statistical floor of experimental data christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays

10. Constant-LET and Path Length Distribution Calculation Does not predict occurrence of large energy depositions Does not predict shape of curve christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays

11. Reaction Mechanisms Nuclear reactions dominate above 500 keV Coulomb scattering does not contribute significantly here christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays

12. Event Rate Simulations christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays Proton environments from CREME GEO – peak five minutes and worst week ISS – space station orbit, apmin8

13. GEO Event Rate Simulations christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays

14. ISS Event Rate Simulations christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays

15. Conclusions The on-orbit response can be predicted with greater detail than available through experiment at energies greater than 700 keV Energy events greater than 130 keV are not predicted by path length calculation for this device Nuclear reactions dominate the event rate at energies greater than 3 MeV christina.l.howe@vanderbilt.edu Measurement and Simulation of the Variation in Proton- Induced Energy Deposition in Large Silicon Diode Arrays