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Radiation Levels in the CLIC Tunnel

Radiation Levels in the CLIC Tunnel. Sophie Mallows Thomas Otto CERN SC/RP. Overview. Simulation of particle and radiation transport using FLUKA 2008 Simplified model of CLIC tunnel Scored Absorbed doses in QP magnets

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Radiation Levels in the CLIC Tunnel

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  1. Radiation Levels in the CLIC Tunnel Sophie Mallows Thomas Otto CERN SC/RP

  2. Overview • Simulation of particle and radiation transport using FLUKA 2008 • Simplified model of CLIC tunnel • Scored • Absorbed doses in QP magnets • 20 MeV hadron fluence, 1MeV neutron equivalent fluence, Prompt doses in tunnel module

  3. FLUKA Geometry 4.5m

  4. Absorbed dose in QPs – Safe Limits • Magnetic Coils in QPs: • Epoxy becomes brittle • insulation may break down • Damage is related to Absorbed Dose, SI unit: J/Kg, special unit: Gray (Gy) • From past experience, a dose of several MGy over the lifetime of a magnet is acceptable • Guideline for CLIC: D < 1 MGy/ year

  5. Damage to Electronics - Effects 2 main effects: • Cumulative Effects (threshold) • Total Ionizing Dose (Gray) • Displacement Damage (1 MeV neutron equivalent) • Single Event Effects (SEEs) (probability) Due to hadrons > 20 MeV

  6. Damage to Electronics – Safe Limits • Dependent on Electronics • For SEE’s can only calculate probability of risk Levels used in for area classification in LHC study (R2E Study Group): • 1 MeV Neutrons • Low:  Fluence <1108 cm-2 • Medium: 1108 cm-2 < Fluence < 11010 cm-2 • High: 11010 cm-2 < Fluence • 20 MeV Hadrons • Low:  Fluence <1107 cm-2 • Medium: 1108 cm-2 < Fluence < 1109 cm-2 • High: 1109 cm-2 < Fluence • Dose • Low:  Dose <1Gy/yr • Medium: 1Gy/yr< Dose < 1kGy/yr • High: 1kGy/yr< Dose

  7. Calculation – Dose • 1500 GeV electrons lost in main beam QPs • Normalization : 180 continuous days running, fractional beam loss 2.5 10-7 per qp Averaged over length of tunnel module Averaged over width of 20cm • Electronics: • Low:  Dose <1Gy/yr • Medium: 1Gy/yr< Dose < 1kGy/yr • High: 1kGy/yr< Dose QP Limit : D < 1 MGy/ year

  8. Calculations -20 MeV Hadron Fluences • 1500 GeV electrons lost in main beam QPs • Normalization: 180 days continuous running, fractional beam loss 2.5 10-7 per qp Averaged over length of tunnel module Averaged over depth of 20cm • Low:  Fluence <1107 cm-2 • Medium: 1108 cm-2 < Fluence < 1109 cm-2 • High: 1109 cm-2 < Fluence

  9. Calculations - 1 MeV Neutron Equivalent Fluences on Silicon • 1500 GeV electrons lost in main beam QPs • Normalization : 180 days continuous running, fractional beam loss 2.5 10-7 per qp Averaged over length of tunnel module Averaged over depth of 20cm • Low:  Fluence <1108 cm-2 • Medium: 1108 cm-2 < Fluence < 11010 cm-2 • High: 11010 cm-2 < Fluence

  10. Additional Slides

  11. Spatial distributionss of Dose Normalization: 1 loss electron

  12. Fractional Beam Losses for 1 MGy/yr • Electron losses in 1 QP • Maximum dose per loss electron in scoring mesh (1cm3 bins) across QP • Fractional beam loss requirements for 1 MGy/yr

  13. “Single event error” SEE, CNGS example • SEU: ionising radiation changes the content of a elementary memory cell of a digital processor, spuriously or permanently. • The critical quantity is fluence of hadrons with E > 20 MeV, 20 (cm-2) • Experience from CNGS: at 20 = 2 107 devices start to show errors • Guideline for CLIC: 20 < 106 … 107/year T. Wijnands, TS-LEA CLIC Workshop 2008 Radiation levels in the CLIC tunnel

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