Radiation Levels in the CLIC Tunnel
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Transcript of 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 20 MeV hadron fluence, 1MeV neutron equivalent fluence,
Prompt doses in tunnel module
FLUKA Geometry
4.5m
Absorbed dose in QPs – Safe Limits
Magnetic Coils in QPs:Epoxy becomes brittleinsulation 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
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
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):
Calculation – Dose
Electronics:Low: Dose <1Gy/yrMedium: 1Gy/yr < Dose < 1kGy/yrHigh: 1kGy/yr < Dose
QP Limit : D < 1 MGy/ year
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
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
Low: Fluence <1107 cm-2
Medium: 1108 cm-2 < Fluence < 1109 cm-2
High: 1109 cm-2 < Fluence
Averaged over depth of 20cmAveraged over length of tunnel module
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
Low: Fluence <1108 cm-2
Medium: 1108 cm-2 < Fluence < 11010 cm-2
High: 11010 cm-2 < Fluence
Averaged over length of tunnel module Averaged over depth of 20cm
Additional Slides
Spatial distributionss of Dose
Normalization: 1 loss electron
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
Th. Otto, SC-RP, CERN CLIC Workshop 2008Radiation levels in the CLIC tunnel
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