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Variations in the Radiation Environment

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Presentation on theme: "Variations in the Radiation Environment"— Presentation transcript:

1 Variations in the Radiation Environment
C. D. Gorsky SGT, Inc. J. L. Barth NASA/GSFC

2 Introduction A programmatic methodology for enabling COTS and emerging technology use in radiation environments requires an accurate definition of the environment with appropriate design margins. Variations in the environment are presented. Limitations of radiation environment models are presented with methods of extending their functionality.

3 The Radiation Environment
Galactic Cosmic Rays Solar Protons & Heavier Ions Trapped Particles Nikkei Science, Inc. of Japan, by K. Endo

4 Components of the Natural Environment
Transient Galactic Cosmic Rays Protons & Heavier Ions Solar Particle Events Trapped Electrons, Protons, & Heavier Ions Atmospheric & Terrestrial Secondaries Neutrons

5 Radiation Effects Total Ionizing Dose Single Event Effects
Trapped Protons & Electrons Solar Protons Single Event Effects Protons Trapped Solar Heavier Ions Galactic Cosmic Rays Solar Events Neutrons Displacement Damage Protons Electrons Spacecraft Charging Surface Plasma Deep Dielectric High Energy Electrons Background Interference on Instruments

6 Programmatic Methodology ref: LaBel et al. IEEE/NSREC 1998
Define the hazard Evaluate the hazard (e.g., dose-depth curves) Define requirements Evaluate parts lists Test unknowns or perform radiation lot acceptance tests (RLATs) on non-RH guaranteed devices Evaluate test data and predict performance Work with designers on alternate device selection or mitigation options/validation Refine above as necessary 3-D analysis of shielding rather than dose-depth curves Select harder part

7 Environment Definition for Programmatic Methodology
Total Ionizing Dose Dose-Depth Curves or Spacecraft Specific Dose Levels Trapped Protons & Electrons Solar Protons Secondary Bremsstrahlung Single Event Effects - Average & Peak Conditions LET Spectra Galactic Cosmic Ray Heavy Ions Solar Heavy Ions Energy Spectra Trapped Protons Displacement Damage Energy Spectra Shielded Solar Protons Shielded Trapped Protons Charging/Discharging Surface - Plasma Electrons Deep-dielectric - High Energy Electrons Instrument Interference Primary Particles Secondary Particles - Shielding Analysis

8 Sun: Dominates the Environment
Trapped Particles Heavier Ions Protons Source Modulator Galactic Cosmic Rays Atmospheric Neutrons Trapped Particles

9 Solar Activity: Cyclic Variation
Solar Flares Sunspot Cycle Discovered in mid 1800s Coronal Mass Ejections Increase in Solar Wind Velocity Solar Particle Events - Proton Rich Solar Flares Increase in Solar Wind Density Solar Particle Events - Heavy Ion Rich Sunspot Cycle Coronal Mass Ejections 50 150 200 250 100 300 Cycle 19 Cycle 20 Cycle 21 Cycle 22 Cycle 18 Sunspot Numbers Holloman AFB/SOON Years after Lund Observatory

10 The Magnetosphere Defined by Interaction of:
Earth’s Magnetic Field - Solar Wind Solar Direction: Compressed to ~ 10 ER Anti-Solar Direction: Stretched into Long Magnetotail ~ 300 Earth Radii Open at the Poles Bar Magnet Representation Accurate to Earth Radii

11 Magnetosphere Bow Shock Cusp Central Plasma Sheet Magnetopause
Solar Wind Heikkila (Color by University of Washington)

12 Particle Penetration of the Magnetosphere
Most Solar Wind Particles Are Deflected (99.9%) Some Become Trapped & Energized Galactic Cosmic Ray & Solar Particle Penetration Depends on: Particle Energy Ionization State Galactic Fully Ionized Solar & Anomalous Component of GCRs Have Lower Ionization States Measured with Magnetic Rigidity in Units of GV

13 Magnetic Rigidity momentum charge H Z > 1
Total Energy Required to Penetrate the Magnetosphere H 48 MeV 87 MeV 173 MeV 284 MeV 987 MeV Magnetic Equator 2900 MeV 2 3 4 5 6 7 1147 MeV/n 313 MeV/n 109 MeV/n 46 MeV/n 23 MeV/n 12 MeV/n Z > 1 after Stassinopoulos

14 Magnetic Storms / Space Weather
“Gusty” Solar Wind Disturbs the Current Systems Major Storms Probably the Result of CMEs Must Be Pointed Toward Earth Strongest Arrive with Interplanetary Magnetic Field Oriented South Can Have Severe Effects Power Blackouts on Earth Disruption of Communications Satellites Loss of Satellites - ANIK-E1, Telstar 401

15 Sunspot Cycle with Magnetic Storms
Sunspots & Magnetic Storm Days # of Days with Ap > 4 Sunspot Number Annual Number of Days with Ap>4 Annual Sunspot Number

16 ANIK E1: Magnetic Storm January 1994 Solar Wind Velocity (IMP-8 MIT)
SAMPEX Electrons E > 1 MeV 8 200 300 800 700 400 500 600 Time of ANIK Failure 1 2 3 4 5 6 7 Velocity (km/s) Counts/s (x10) 1 6 11 16 21 25 31 1 6 11 16 21 25 31 January 1994

17 Trapped - Van Allen Belts
Omnidirectional Components Protons: E ~ MeV Electrons: E ~ (?) MeV Heavier Ions: Low E - Non-problem for Electronics Location of Peak Levels Depends on Energy Average Counts Vary Slowly with the Solar Cycle Location of Populations Shifts with Time Counts Can Increase by Orders of Magnitude During Magnetic Storms March 1991 Storm - Increases Were Long Term Radiation Effects Dose & Degradation Single Event Effects - Protons only Models - AP8/NOAAPRO & AE8

18 Van Allen Belts High Latitude Horns Inner Belt Outer Belt Slot Region

19 Proton & Electron Average Models
AP-8 Model AE-8 Model 1 2 3 4 5 6 7 8 9 10 Ep > 10 MeV Ee > 1 MeV #/cm2/sec #/cm2/sec L-Shell NASA/GSFC

20 Trapped Particle Variations
Protons Electrons Fairly Stable Cyclic Modulations Due to the Solar Cycle ~ 2 Lowest Levels Are at Peak of Solar Maximum Highest Levels Are at Lowest Point in Solar Minimum Rate of Change ~ 6%/year Geomagnetic Field Shift Changes Location ~ 6 ° westward / 20 years Anisotropy at Inner Edge ( km) 2 ~ 7 Particle Increases at Outer Edge - New Belts Geomagnetic Storms Cyclic Modulation Due to the Solar Cycle ~ 2 Highest Levels Are at Peak of Solar Maximum Lowest Levels Are at Lowest Point in Solar Minimum Inner Zone - Fairly Stable Outer Zone - Dynamic 102 ~ 106 Solar Cycle Variations Are Masked Local Time Variations Due to Magnetic Field Distortion 27-Day Variation Due to Solar Rotation Magnetic Storms & Sub-Storms

21 TIROS/NOAA Trapped Protons
Solar Cycle Variation: MeV Protons B/Bmin=1.0 L=1.20 L=1.18 L=1.16 Proton Flux (#/cm2/s) Radio Flux F 10.7 L=1.14 1976 1980 1984 1988 1992 1996 Date Huston et al.

22 March 1991 Magnetic Storm New Proton Belt
CRRES - AF Phillips Laboratory, SPD/GD

23 Activity in the Slot Region - SAMPEX
SAMPEX/P1ADC: Electrons E > 0.4 MeV 190 250 310 370 430 490 550 5 3 11 9 7 1 L-Shell Day (1992)

24 Magnetic Storms - Hipparcos
Star Mapper - Radiation Background March 1990 1991 1992 2 4 6 L-Shell 4-Day, 9-Orbit Averages Daly, et al.

25 Proton Flux Contours Variations with Altitude
Protons in SAA km Proton Flux Contours Variations with Altitude At 800 km, SAA is an oval shape At 1300 km, the size of the oval shape increases At 3000 km, Van Allen “belt” structure of proton flux contours Latitude (deg) Longitude (deg) Protons in SAA km Protons in SAA km Latitude (deg) Latitude (deg) Longitude (deg) Longitude (deg)

26 AP8 - MAX Spectra Integral Proton Fluences Energy Range Range in Al:
MeV Range in Al: 30 MeV ~ .17 inch Effects: Total Dose Single Event Effects Solar Cell Damage Fluence (#/cm2/day) Energy (>MeV)

27 AE-8 - MAX Spectra Integral Electron Fluences Energy Range
MeV Range in Al: Effects: Total Dose Surface Charging Deep Dielectric Charging Solar Cell Damage Fluence (#/cm2/day) Energy (>MeV)

28 Single Event Effects - Proton Rates
I=90 deg, H=1000/1000 km, Solar Minimum Trapped proton exposure in LEO depends on where satellite passes through the SAA Calculate SEE rates for Proton daily average Worst case SAA pass Peak proton counts in SAA Implications for memory scrub rates & other spacecraft operations Protons (#/cm2/s) Energy (>MeV)

29 Particle Variations Protons and Photons Electrons
extremely penetrating difficult to shield against Electrons lower energies make them less penetrating

30 Dose Variation with Altitude 0 degree inclination

31 Dose Variation with Altitude 90 degree inclination

32 Dose-Depth Curves Dose Variation with Orbit
Use “Dose-Depth Curves” to define top level dose requirements “Total Dose” includes contributions from Trapped protons Trapped electrons Solar protons Minimum design margin of “x2” added to account for uncertainty in environment models and variation of device response within flight lots

33 Galactic Cosmic Ray Ions
All Elements in Periodic Table Energies in GeV Found Everywhere in Interplanetary Space Omnidirectional Mostly Fully Ionized Cyclic Variation in Fluence Levels Lowest Levels = Solar Maximum Peak Highest Levels = Lowest Point in Solar Minimum Single Event Effects Hazard Model: CREME96

34 GCRs: Solar Modulation
Galactic Cosmic Rays CNO - 24 Hour Averaged Mean Exposure Flux Solar events Long term cyclic variation Peak at solar minimum Shielding ineffective for high energy ions Attenuation by magnetosphere effective for low inclination, low altitude orbits CNO (#/cm2/ster/s/MeV/n) Years GCRs: Shielded Fluences - Fe GCRs: Integral LET Spectra Interplanetary, CREME 96, Solar Minimum CREME 96, Solar Minimum, 100 mils (2.54 mm) Al Particles (#/cm2/day/MeV/n) LET Fluence (#/cm2/day) Energy (MeV/n) LET (MeV-cm2/mg)

35 Solar Particle Events Increased Levels of Protons & Heavier Ions
Energies Protons - 100s of MeV Heavier Ions - 100s of GeV Abundances Dependent on Radial Distance from Sun Partially Ionized - Greater Ability to Penetrate Magnetosphere Number & Intensity of Events Increases Dramatically During Solar Maximum Problem for Total Ionizing Dose, Displacement Damage, & Single Event Effects Models Dose & Displacement Damage - SOLPRO, JPL, ESP Single Event Effects - CREME96 (Protons & Heavier Ions)

36 Sunspot Cycle with Solar Proton Events
Proton Event Fluences Solar Proton Events Solar proton events correlate with the sunspot cycle Only low inclination, low altitude orbits are protected from solar proton events A problem for degradation & single event effects ESP model by NRL/NASA Protons (#/cm2) Year Solar Protons: Orbits ESP Model of Solar Proton Cumulative Fluences Proton Levels Predicted by CREME 96 Protons (#/cm2/s/MeV) Energy (MeV)

37 Integral LET Spectra , 100 mils AL
Solar Heavy Ions Frequency & intensity increase during solar active phase of the solar cycle Attenuation by magnetosphere effective for low inclination, low altitude orbits Solar heavy ion levels are orders of magnitude higher than galactic cosmic ray levels Shielding more effective than for galactic cosmic ray heavy ions LET Fluence (#/cm2/sec) LET (MeV-cm2/mg) Differences in Energy Spectra Galactic Cosmic Ray & Solar Heavy Ion Spectra Effect of Shielding on Heavy Ions Galactic Cosmic Ray & Solar Heavy Ion Spectra Carbon, 100 mil Shield Interplametary All Elements, 100 mil Shield Interplametary Fluence (#/cm2/s) Fluence (#/cm2/s) Energy (MeV) LET (MeV-cm2/mg)

38 Summary Requirements for the definition of the radiation environment for a programmatic methodology were defined. The variations in the radiation environment which must be considered in the definition were described. Appropriate models for defining the radiation environment were presented. References: “Emerging Radiation Hardness Assurance (RHA) Issues: A NASA Approach for Spaceflight Programs,” K. A. LaBel, J. L. Barth, R. A. Reed, and A. H. Johnston, IEEE Trans. on N.S., December 1998. “Applying Computer Simulation Tools to Radiation Effects Problems, Part I: Modeling Space Radiation Environments,” J. L. Barth, Published in 1997 IEEE NSREC Short Course Notes, July 1997.

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