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Radiation issues discussed at the LVPS meeting

Radiation issues discussed at the LVPS meeting. F. 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

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Radiation issues discussed at the LVPS meeting

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  1. Radiation issues discussed at the LVPS meeting F. Faccio CERN Federico Faccio/CERN

  2. 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 Tutorial with notes Paper with references Federico Faccio/CERN

  3. Components discussed • COTS = Commercial Off The Shelf • No effort made to improve, assure or even test the radiation tolerance • 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! • ASICS • Developed in modern CMOS technologies, no TID issues at the foreseen levels, SEL unlikely (dependent on design), SEU can be dealt with architecture Federico Faccio/CERN

  4. Total Ionizing Dose (TID) Potentially all components Displacement damage Transient SEEs Bipolar technologies Optocouplers Optical sources Optical detectors (photodiodes) Static SEEs Combinational logic Operational amplifiers SEU, SEFI Digital ICs Summary of radiation effects Permanent SEEs SEL CMOS technologies SEB Power MOSFETs, BJT and diodes SEGR Cumulative effects Power MOSFETs Single Event Effects (SEE) Federico Faccio/CERN

  5. Cumulative effects • TID: most components do not fail below ~2-3krad => estimated level 1krad (Loc1) • Displacement damage: most devices start to be sensitive at ~1010 p/cm2 => estimated level 8•108 p/cm2 (Loc 1) • Issues: • Safety factors • Increase dose map granularity • Additional shielding Federico Faccio/CERN

  6. Total Ionizing Dose (TID) Potentially all components Displacement damage Transient SEEs Bipolar technologies Optocouplers Optical sources Optical detectors (photodiodes) Static SEEs Combinational logic Operational amplifiers SEU, SEFI Digital ICs Summary of radiation effects Permanent SEEs SEL CMOS technologies SEB Power MOSFETs, BJT and diodes SEGR Cumulative effects Power MOSFETs Single Event Effects (SEE) Federico Faccio/CERN

  7. Nevents s = (cm2) F SEE: which particles? Heavy ions (space) => high dE/dx (LET, in MeV•cm2/mg) Hadrons (LHC) => low dE/dx, but nuclear interactions above ~20MeV, n & p equivalent => Estimated fluence (Loc1) 108 p/cm2 above 20MeV Federico Faccio/CERN

  8. Low fluence = low occurrence rate BUT OCCURRENCE! “Threshold” for radiation effects Cumulative effects SEEs Danger Danger Integrated dose/fluence 5-20MeV Particle energy Safe Safe Federico Faccio/CERN

  9. + Vs To Counter Example: DC-DC converter (1) Test cards with 4 Power MOSFET samples were irradiated at each voltage using 60Mev protons. The MOSFETs were those used in the candidate DC-DC converter Federico Faccio/CERN

  10. SEEs • SEB in power devices (destructive: derating? Replacement?) • SEFI in programmable devices (requires reprogramming/reset) • SEL in CMOS circuits (not very likely, but destructive effects) • Issues: • Particle flux needed to estimate SEE rate • Additional shielding would reduce rates • Estimate of rates/Management of risk Federico Faccio/CERN

  11. Risk Management 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) Federico Faccio/CERN

  12. Board-level testing & hybrids • Board-level testing • 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

  13. Conclusion System Environment Radiation hazard Merging knowledge on … is a big challenge for all LHC teams! Federico Faccio/CERN

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