Space Radiation and its Effects

1
Space Radiation and its Effects

• P Nieminen, E Daly, ESA/ESTEC The Netherlands P
  Truscott, C Dyer, H Evans, DERA UK
• F Lei, R Gurriaran, U. Southampton, UK
• J Allison, U. Manchester, UK

Images and data in this presentation courtesy of
SOHO (ESA/NASA), UoSAT-2 (University of
Surrey/ESA), ISS Phase 1 (NASA/RSC Energia/DERA)
2
Spacecraft Missions and Radiation Effects
3
Cumulative Effects in Spacecraft Microelectronics

• Total ionising dose
• Charge collection in insulating or
• passivation oxide layers
• change voltage thresholds
• leakage currents

• Displacement (NIEL) damage
• Carrier traps degrade
• Bipolar transistor gain
• Solar cell efficiency
• Detector efficiency/resolution

4
Total Ionising Dose

• Calculation of total dose
• Detailed simulation over complex 3D geometry
• 1D shield simulation results and integrate dose
  contributions over shield distribution (sector
  shielding analysis)

• Shield optimisation
• Evaluation of Al/Ta graded shields for maximum
  attenuation of electron dose effects
• Detailed EM simulation essential ITS/EGS4

5
Radiation Dose for Manned Space Flight

• Space Shuttle missions
• 0.1 - 0.5 mGy/day direct ionising radiation
• 0.08 mSv/day neutrons
• Mir Space Station
• 0.2 - 0.4 mGy/day direct ionising radiation
• 0.15 mSv/day neutrons
• Detailed radiation transport necessary to due to
  quantities of shielding, and to determine effects
  of secondary particle radiation (GEANT3,
  HETC/LHI, MORSE)

6
Single Event Effects in Spacecraft
Microelectronics

• Single Event Upsets (SEU)
• Bit-flip in digital microelectronics
• Single Event Latchup (SEL)
• Large parasitic currents from PNPN
• structures
• Single Event Gate Rupture (SEGR)
• Applicable to Power MOS, voltage
• breakdown of the oxide from charge
• produced between source and drain
• Single Event Breakdown (SEB)
• Current from freed charge amplified by
• parasitic device

7
Observations of Single Event Effects

• SEE observed with increasing frequency since 1975
• Tracking Data Relay Satellite attitude control
  showed 1s-100s SEUs/day - expensive ground
  control required
• PRARE instrument on ERS-1 failed 5 days after
  launch due to latchup
• PCs on Shuttle Mir require rebooting
  approximately every9 hours, and PCMCIA card
  failures due to SEU in CIS
• Hubble Space Telescope suffers many SEUs during
  SAA, requiring frequent scrub and reloading of
  guidance software
• Radiation transport calculations required to
• Accurately quantify the SEE environment under
  various shielding conditions
• Better understand the factors affecting SEE
  susceptibility in microelectronics

8
Multiple-Bit Upsets

• Multiple-bit upsets (MBU) can be induced by
  direct ionisation or nuclear recoil
• Defeat parity checking and complicate simple EDAC
• Becoming increasingly important as feature-sizes
  shrink
• Simulation of effects requires treatment of
  high-energy nuclear interactions, ion
  micro-dosimetry and variance reduction (HETC/LHI,
  IMDC)

9
Background in Sensors

• SEUs in CCDs appear as particle track
  background
• Displacement damage produces loss of pixel
  operation or reduced charge collection
• Interactions in spacecraft and instrument may
  result in prompt emissions within the instrument
  bandwidth X-ray fluorescence in XMM sensors.
• Induced radioactivity produces delayed background

10
Radioactive Background in Sensors

• High-energy nuclear interactions lead to wide
  variety of spallation products
• Track energy deposition over multiple decay
  generations
• Complex time-dependency variation of source with
  orbit variety of half-lives
• GEANT3 being used to assess background and
  optimise detector performance in INTEGRAL
• Background in Compton Gamma Ray Observatory
  (CGRO) treated using HETC/LHI, MORSE, ETRAN

11
Analysis of X-ray g-ray emissions

• Remote sensing of solar system bodies for surface
  composition
• ?-ray emissions from
• Prompt and radioactive decay of spallation and
  neutron-capture products
• Natural radioactivity

• X-ray fluorescence from
• direct ionisation by incident particles
• induced EM cascades
• solar X-rays
• Require comprehensive treatment of interaction
  processes down to low-energy (

12
Spacecraft Charging

• Telstar 401 failure on 10th Jan 1997 following
  CME on 7th
• ANIK-E1 E2 failures in 1994 and 1996
• For service providers, price of inadequate
  hardening is loss of spacecraft and expensive
  compensation / litigation
• Simulation of electron transport to determine
  build-up of charge and secondary emission

13
Cosmic Radiation at Aircraft Altitudes

• Radiation hazard to airline crews and frequent
  flyers
• 1 mSv after 200 flight hours, 6 mSv/year on some
  long-haul polar routes
• European Directive on control of occupational
  radiation exposure of air crews - May 2000
• SEE Experience
• PERFORM computer withdrawnfrom tests in 1991
  followingaccumulation of errors in SRAM
• 1 upset per flight in 280 64K SRAM on Boeing
  E-3 AWACS and NASA ER-2
• CUTE experiment shows 1 upset every 200
  flight-hours in 4 Mbit SRAM - 2 are
  multiple-bit errors
• Monitoring experiments on Concorde, Boeing 767,
  WB-57F

14
Ground Level Experience of SEE

• Neutron-induced SEEs dominant error rate at sea
  level
• Data from major computer installations and
  cardiac defibrillators consistent with known
  sea-level neutrons
• Altitude effects are seen at Denver (x3) and
  Leadville (x10)
• Burnouts observed in HV power MOSFETS used in
  French trains ascribed to neutrons - one failure
  per 100 device-hours at full rated voltage
• RAMs 1Mbit will not meet 2000 FITS
  specification at sea-level

15
Conclusions

• Solar system radiation environment is highly
  complex and variable
• New solar maximum 2000-2001 approaching
• New technologies mean increasing vulnerability to
  radiation-induced effects
• Need for space-specific radiation analysis tools
  to provide a comprehensive treatment of transport
  and effects
• GEANT4 should be the basis of this tool