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COTS for the LHC radiation environment: the rules of the
game
Federico Faccio CERN Federico Faccio - CERN Outline Introduction
Summary of radiation effects Risk management
Dealing with the radiation hazard: fundamental steps Conclusion
Federico Faccio - CERN Why talking about COTS? COTS = Commercial
Off The Shelf
No effort made to improve, assure or even test the radiation
tolerance Poor or no traceability of origin (what REALLY is inside
the package??) Cheaper and better performance, sometimes there is
no alternative to their use The cost of using COTS is higher than
the bare part cost: testing and logistic are expensive! Federico
Faccio - CERN Summary of radiation effects
Permanent SEEs Total Ionizing Dose (TID) Potentially all components
SEL CMOS technologies SEB Power MOSFETs, BJT and diodes SEGR
Cumulative effects Power MOSFETs Displacement damage Bipolar
technologies Optocouplers Optical sources Optical detectors
(photodiodes) Single Event Effects (SEE) Transient SEEs
Combinational logic Operational amplifiers Static SEEs SEU, SEFI
Digital ICs Federico Faccio - CERN Risk management at system level
(top-down)
Use of COTS => risk avoidance Mission: LHC and experiments
running Which failure tolerable? How often? = Where? f (system)
Risk management at system level (top-down) Do we have enough
experience and competence in the same organizational unit?
(learning process is time and resources consuming!) Federico Faccio
- CERN Dealing with the radiation hazard
Get a good knowledge of the environment Define the requirements for
the components Understand the effects Identify the candidate
components Test the candidate components Engineer the system
Federico Faccio - CERN The radiation environment
Knowledge in meaningful terms: TID Displacement damage SEEs Total
Dose [krad, Gy] 1 MeV equivalent neutron fluence (n/cm2) Fluence
and energy distribution of main particles (p/cm2) 20MeV (E,all
hadrons)dE or at least Get the most precise estimate of the
environment Taylor the safety factor Safety factor = cost Federico
Faccio - CERN Effects of the environment
CMOS technologies Memories (SRAM, DRAM, Flash, EEPROM) FPGAs
Microprocessors and DSPs Bipolar technologies Power devices
Optocouplers Federico Faccio - CERN CMOS technologies (1)
Displacement damage TID
Sensitive with dose rate effects Variable failure levels SEL Not
very likely in LHC A few known sensitive components: K5 mp from
AMD, SRAMs, ADCs, DSPs, FPGAs SEGR, SB Very unlikely Federico
Faccio - CERN CMOS technologies (2) SEU: memories SRAMs Sensitive
with low threshold
Sometimes MBU Stuck bits only with high LET DRAMs Sensitive with
low threshold Situation improved with decreased cell area and
better signal over noise sp comparable to SRAMs SEFI possible (low
s) Flash Memories Errors in the complex control circuitry with
different consequences Higher threshold than SRAMs-DRAMs Much lower
sp ( times) EEPROMs Write mode more sensitive than read Higher
threshold than SRAMs-DRAMs SEFI possible Federico Faccio - CERN
CMOS technologies (3) SEU: FPGAs SRAM-based
Loss of configuration: consequences? Low threshold: likely in LHC
Requires reprogramming Antifuse-based ONO antifuses sensitive to
destructive event with high threshold A-Si antifuses more robust FF
and combinatorial logic gates: Sensitive in both technologies (FF
implementation with sensitivity) TMR can be integrated in
antifuse-based In new Virtex series, TMR can be safely integrated
SEFI: Can happen in both technologies (SEU in JTAG circuitry) with
low s Solutions proposed by both Actel and Xilinx Radiation
tolerant products available (on epi substrate) Variability in
radiation performance (esp. TID and SEL) Documented mitigation
techniques exist for both Actel and Xilinx Federico Faccio - CERN
CMOS technologies (4) SEU effects strongly
application-dependent
SEU: microprocessors and DSPs SEU effects strongly
application-dependent Testing has to be performed running a
representative program SEU consequences: very variable (no effect,
calculation error, code stopped, ) Most devices are sensitive in a
proton environment, hence in LHC Federico Faccio - CERN
Simultaneous effects:
Bipolar technologies Simultaneous effects: they add up TID Leakage
paths and b degradation Sensitive with dose rate effects (ELDR)
Variable failure levels Displacement damage b degradation PNP are
affected from 31011 p/cm2 (50MeV) NPN are affected from 31012 p/cm2
(50MeV) Voltage regulators, comparators, op amps SEL SET At the
output of comparators Rail-to-rail signal Federico Faccio - CERN
Power devices Sensitive to TID and displacement damage
Power MOSFETs, bipolar and diodes SEB Sensitive in hadron
environment (also 14MeV n) De-rating often required (of variable %)
P-channel MOSFETs are much less sensitive Power MOSFETs and IGBTs
SEGR Very rare in an hadron environment Dependent on Vgs (sensitive
for Vgs < -20V) Dependent on gate oxide thickness Most data
refer to HI: de-rate as indicated for experiments run with LET of
26 MeVcm2mg-1 Federico Faccio - CERN Optocouplers Sensitive to TID
and displacement damage Sensitive to SET
CTR decreases after 1-51010 p/cm2 (4N49 Micropac and Optek, P2824
Hamamatsu) Degradation of LED and ptotodetector Other devices, with
different LED and coupling LED/phototransistor, have good
resistance (6N140, 6N134, 6N139 from HP) Sensitive to SET
Sensitivity increases with speed Sensitive to direct ionization
from p+ (angular effect) Might induce transient out dropout in
DC-DC conv. Federico Faccio - CERN The radiation requirements
(theory)
Know the system where the component operates (top-down) Cumulative
effects: Simulation Test procedures COTS variability Estimated
level SF Destructive SEEs: No destructive SEE Transients and SEU
Acceptable rate for the system Federico Faccio - CERN The radiation
requirements (headaches)
Cumulative effects: Which SF???? Simulationaccurate Test
procedurescorrect COTS variabilitysystematic Taylor the SF
Destructive SEEs: Example Envir. = 1011 h/cm2 1000 components s =
cm2? Which limit on cross-section? Which limit on HI LETth?
Transients and SEU Estimate the error rate in the real environment
Evaluate the system-level impact of each error Federico Faccio -
CERN The candidate components
Search for radiation data Databases on web (often obsolete): JPL
compendia, GSFC, DTRA, SPUR, . NSREC Workshop records December
issue of Trans. Nucl. Science ESA/ESTEC final presentation day
(soon database?) For FPGA, look in the manufacturers home page for
fresh data How to interpret SEE data? Rough guidelines based on
Computational method to estimate SEU rates in an accelerator
environment (NIM, August 00) Federico Faccio - CERN How to
interpret SEE data (1)
You have data for mono-energetic p or n beams (60-200MeV)! SEErate
= sp/n flux (all hadrons above 20MeV) Example Xilinx XC4010XL:
s100MeV n = 4.410-15 cm2/bit Estimated flux = 2103 cm-2s-1 (=1011
cm-2) => SEErate = 8.810-12 errors/(bit s) Each chip contains
about 283k configuration bits => SEErate chip = 2.510-6 s-1 For
each 110 FPGA, one looses its configuration each hour! Federico
Faccio - CERN How to interpret SEE data (2)
You only have Heavy Ion data... but you have the Weibull fit
parameters! 20 40 60 80 100 120 Deposited energy cross section (cm
2 ) Weibull curve Probability curves from the simulation of the
environment 1 3 Federico Faccio - CERN How to interpret SEE data
(3)
You only have Heavy Ion data... and you do not have the Weibull fit
parameters... You can just have a feeling: LETth < 5 MeVcm2mg-1
=> quite sensitive LETth > 15 MeVcm2mg-1 => not sensitive
Federico Faccio - CERN Testing the candidate parts
Never use data from a database as a source for qualification, only
to identify candidate parts! Radiation source Irradiation procedure
Board-level testing and hybrid devices Federico Faccio - CERN -
rare SEU under-estimate (CMS: HCAL, Muons, Cavern)
Radiation source 60Co TID Low energy neutrons (nuclear reactor)
Displacement damage SEEs Mono-energetic hadron beams ( MeV p) With
60 MeV: - rare SEU under-estimate - Is the energy enough for
SEB/SEGR? Global test plan (CMS: HCAL, Muons, Cavern) What about
thermal neutrons? (they have not been taken into account for the
experiments) Federico Faccio - CERN Preferential access conditions
for high-E proton beams
Preferential agreement with 2 facilities established since several
years through the RD49/COTS project : CRC (Cyclotron Research
Centre) in UCL, Louvain-la-Neuve (Be) > protons (60MeV), Heavy
Ions, neutrons (low intensity) - PSI (Paul Scherrer Institute) in
Villigen (Ch) > protons (250MeV) Federico Faccio - CERN
Irradiation procedure (1)
Prompt + Latent charge buildup Irradiation + Annealing Test methods
give worst case picture CMOS TID ELDR effect JPL advice: Bipolar
TIDspec < 30krad 50 & rad/s test at room T compare if
failure in any condition => do not use! TIDspec > 30krad test
up to 30krad in 3 conditions: 50 & rad/s at room T, 1rad/s at
90oC compare if comparable => use 90oC test BUT take an
additional SF = 2 on TIDspec Federico Faccio - CERN Irradiation
procedure (2)
Displacement damage - room T, all grounded - measurement of s -
representative conditions - needs a dedicated setup - careful to
SEFI - with h-beams => in air and packaged E (MeV) s SEU, SET
Vds sSEB rated Vds - measurement of s - protect the component! -
needs a dedicated setup - for SEB & SEGR look for derating
conditions SEL, SEB, SEGR Federico Faccio - CERN Board-level
testing & hybrids
Less infos on actual safety margins It can be difficult to trace
back the origin of problems Use for go/no go tests only! Can give
useful infos on system response (esp. SEU) Hybrid devices Difficult
to know what is in the hybrid (proprietary designs, no infos from
the manufacturer) Examples on DC-DC power converters (JPL, NASA)
Federico Faccio - CERN Qualify the components
Engineer the system Is the tolerance sufficient? Qualify the
components to be used Test the candidate components Yes
Qualification OK? No Is there an alternative component? No Yes Yes
Use the components No Reduce requirements: - refine the environment
knowledge - use mitigation techniques (for SEU) - foresee
replacement if possible - modify the system Federico Faccio - CERN
Summary Radiation effects Risk management
risk avoidance impossible with COTS! more efficiently applied at
system level! Steps to deal with the radiation hazard know the
environment understand the effects define the requirements identify
the candidate components test engineer the system Federico Faccio -
CERN Big challenge for all LHC teams!
Conclusion Main rule of the game: System Environment Radiation
hazard To merge knowledge on Big challenge for all LHC teams!
Federico Faccio - CERN Reference material This presentation, made
at the 6th Workshop on Electronics for the LHC Experiments (Cracow,
September 2000), has been followed by a full paper with an
extensive set of references (79 papers). The paper can be found as:
- F.Faccio, COTS for the LHC radiation environment: the rules of
the game, proceedings of the 6th Workshop on Electronics for the
LHC Experiments, CERN , CERN/LHCC/ , 25 October 2000, page 50
Federico Faccio - CERN