Radiation Effects and Mitigation

Insert cool group name here Josh Mackler Amanda Quan Joe Tostenrude

CURRENT EVENTS Why do we care? • Damage

o Satellites o Power grids o Cellphone networks

• Flights re-routed (travelling high altitude) • Electronic components reducing in size

Recent Solar Event (Jan 22, 2012) Halloweenstorm Phobos-Grunt

Jun 7, 2011

SPACE RADIATION OVERVIEW

Nikkei Science, Inc. of Japan, by K. Endo

Radiation Sources: • Solar events - Solar wind

o 9-13 year cycles o Solar flares o Coronal mass ejections

• Galactic Cosmic Rays o Energies in GeV o Protons, Alpha particles, heavy ions o Found everywhere in interplanetary space

• Van Allen Belts - Magnetosphere o Earth's magnetic field interaction with

ionized solar wind o Deflect majority of particles o Traps protons and electrons o Varies with solar events and within regions

South Atlantic Anomaly o Aurora Borealis and Australis

TERRESTRIAL RADIATION • Nuclear reactors

o Gamma and neutron radiation o Interfere with sensors and control circuits

• Nuclear explosions o Electromagnetic radiation o Electromagnetic pulse (EMP) o High dose of ionizing particles

• Medical devices o Radiotherapy interaction

RADIATION METRICS AND EFFECTS • Dose o Semiconductor lattice displacement o Trapped charge in thin gate oxide

o Increased gate leakage o Units in Rad(Si) - 0.01 J per kg

• Total Ionizing Dose o Total deposited energy due to protons and electrons (primarily) o Voltage threshold shift o Cumulative long term damage

• Dose Rate Upset o Over shorter intervals (20-50ns) o Power rail collapse, metal burnout

RADIATION METRICS AND EFFECTS

• Single Event Effects o Categories

Destructive Unrecoverable Recoverable Data Integrity

o Types Single Event Upset Single Event Transient Single Event Latch-up

RADIATION METRICS AND EFFECTS o Single Event Upsets (SEU)

Flip-flop or memory bit cell state changes due to single ion strike Multi-bit upsets in adjacent memory cells State machine control logic upset (SEFI)

o Single Event Transients (SET) Charge from ion deposited in circuit Glitches on combinational logic

o Single Event Latch-up (SEL) Heavy ion or high energy proton induced latch-up Low impedance path from power rail to transistor

MITIGATION APPROACHES Why doesn't shielding work?

• Some sensors need to be exposed • Impractical for some applications

• Alpha particles – sheet of paper • Beta particles – few mm of aluminum • Xray/Gamma rays – several cm of lead • High energy protons in space – good luck!

• Shielding can slow down ions and increase the energy transfer of high-energy protons

Approaches

• Radiation Hardening by Process (RHBP) • Radiation Hardening by Design (RHBD) • Software

RHBP • Radiation Hardening By Process

o Advantages: Immune to latch-up Mitigates SEU

o Disadvantages: Expensive Low yield Process instability Technology lag

RHBD TECHNIQUES RTL code techniques • Fully specified case statements • Error Detection and Correction (EDAC) • Memory scrubbing • Triple modular redundancy (TMR)

Custom digital logic standard cell library • Dual Inter-locked Storage Cells (DICE) • Temporal (pulse) filters • High drive single stage clock drivers

Custom memory • Bit and word level interleaving • High capacitance bit cell

MAESTRO Example of RHBD design in practice

• 49 core processor based on Tilera TILE64 architecture • 2-D mesh with low-latency high-bandwidth register-

mapped networks • 500 Krad TID Artisan memories • EDAC and scrubbing to meet SEU rate requirements • Cache parity • RHBD Digital logic flow • Software suite for parallel processing

SOFTWARE MITIGATION OF RAD - OVERVIEW

Fault-tolerance in software domain is not as well understood as fault-tolerance in hardware domain

• Controversial opinions exist on whether reliability can be used to evaluate software. • Software failures are mostly due to the activation of design faults by specific input

sequences. • This makes the reliability of a software module dependent on the environment that

generates input to the module over the time. Software fault-tolerance techniques:

• Single-version o Fault detection o Containment o Recovery mechanisms

• Multi-version o Redundant software modules o Design diversity rules

SOFTWARE MITIGATION OF RAD - SINGLE-VERSION

Acceptance testing/fault detection • Timing checks • Coding checks • Reversal checks • Reasonableness checks • Structural check

Techniques for fault containment

• Modularization • Partitioning • System closure • Atomic action

Fault Recovery techniques

• Exception handling • Checkpoint and restart

SOFTWARE MITIGATION OF RAD - MULTI-VERSION

Redundancy • Doesn't work quite the same way since duplicate software systems will be exactly the

same and do not have the same induced errors from the environment that hardware does (i.e. software will have all the same inputs and therefore all the same outputs)

• Recovery blocks use the concept of retrying the same operation in expectation that the problem is resolved after the second try.

• Allocation - at which level is redundancy most useful? (procedure, process, whole system)

Design diversity • Triplicating a software module cannot tolerate faults because the same fault is

replicated in all blocks. • The goal becomes diversity rather than similarity. This is widely accepted to be a

difficult task.

CONCLUSION

NASA/GSFC Eng Seminar –Radiation Effects 101 presented by Kenneth A. LaBel – Oct 28, 2005

REFERENCES http://www.latimes.com/news/science/la-sci-solar-flare-20120124,0,2353551.story?track=icymi http://www.space.com/14404-mars-rover-solar-radiation-storm-curiosity.html http://radhome.gsfc.nasa.gov/radhome/papers/Core_Tech.pdf http://en.wikipedia.org/wiki/Radiation_hardening http://en.wikipedia.org/wiki/Silicon_on_sapphire http://www.honeywellmicroelectronics.com/radiation-hardened-technology.php https://nepp.nasa.gov/mapld_2009/talks/083109_Monday/03_Malone_Michael_mapld09_pres_1.pdf http://holbert.faculty.asu.edu/eee560/see.html http://www.aeroflex.com/ams/pagesproduct/datasheets/leon/ut699leon3ftdatasheet.pdf http://web.mst.edu/~umrr/cf147.pdf http://blogs.mentor.com/jvandomelen/blog/2011/01/14/radiation-mitigation/ http://techbites.com/201006032772/myblog/blog/z0002-yes-mentor-introduces-rad-tolerant-fpga-synthesis.html http://en.wikipedia.org/wiki/Triple_modular_redundancy http://en.wikipedia.org/wiki/Memory_scrubbing http://en.wikipedia.org/wiki/Radiation_hardening http://press.xilinx.com/phoenix.zhtml?c=212763&p=irol-newsArticle&ID=1448836&highlight= http://www.ieee.org/organizations/pubs/newsletters/npss/0305/rhbd.html http://www.aeroflex.com/ams/pagesproduct/articles/COTSJournalRH.pdf http://webcache.googleusercontent.com/search?q=cache:4qbA8y8E9KQJ:holbert.faculty.asu.edu/eee560/tiondose.html+what+is+%22total+ionizing+dose%22&cd=5&hl=en&ct=clnk&gl=us http://news.discovery.com/space/cosmic-rays-killed-russian-mars-probe-120131.html

• http://radhome.gsfc.nasa.gov/radhome/papers/LaBel_FPGA04.pdf • http://webcache.googleusercontent.com/search?q=cache:hxS9cFg33rYJ:www.aero.org/capabilities/seet/SEupset.html+seu+b

it+flips&cd=1&hl=en&ct=clnk&gl=us • http://webcache.googleusercontent.com/search?q=cache:hxS9cFg33rYJ:www.aero.org/capabilities/seet/SEupset.html+seu+b

it+flips&cd=1&hl=en&ct=clnk&gl=us