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M. Glaser 1 , S. Guatelli 2 , B. Mascialino 2 , M. Moll 1 , M.G. Pia 2 , F. Ravotti 1

Simulation for LHC Radiation Background Optimisation of monitoring detectors and experimental validation. M. Glaser 1 , S. Guatelli 2 , B. Mascialino 2 , M. Moll 1 , M.G. Pia 2 , F. Ravotti 1 1 CERN, Geneva, Switzerland 2 INFN Genova, Italy. IEEE Nuclear Science Symposium San Diego, CA

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M. Glaser 1 , S. Guatelli 2 , B. Mascialino 2 , M. Moll 1 , M.G. Pia 2 , F. Ravotti 1

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  1. Simulation for LHC Radiation BackgroundOptimisation of monitoring detectors and experimental validation M. Glaser1, S. Guatelli2, B. Mascialino2, M. Moll1, M.G. Pia2, F. Ravotti1 1CERN, Geneva, Switzerland 2INFN Genova, Italy IEEE Nuclear Science Symposium San Diego, CA 30 October – 4 November 2006

  2. Radiation monitoring at LHC • The effect of radiation on installed equipment is a major issue for LHC experiments • Necessary to monitor radiation fields during early LHC commissioning • to prepare for high intensity running • to prepare appropriate shielding or other measures • A lot of work is in progress to ensure that radiation effects do not make LHC commissioning even more difficult than expected Critical issue A radiation monitoring system adapted to the needs of radiation tolerance understanding from the first day of LHC operation

  3. Solid State Radiation Sensor Group Evaluation of various radiation monitoring detectors Optimisation Experimental measurements + simulation Sensor Catalogue www.cern.ch/lhc-expt-radmon/ Sensors suitable for dosimetry in LHC experimental environment Mixed-LET radiation field ~5 orders of magnitude in intensity Many devices tested, only a few selected 2 x RadFETs (TID)[REM, UK and LAAS, France] 2 x p-i-n diodes (1-MeV Feq)[CMRP, AU and OSRAM BPW34] 1 x Silicon detectors (1-MeV Feq)[CERN RD-50 Mask]

  4. Commercial packaging cannot satisfy all the experiments requirements (size/materials) Development & study in-house at CERN 1.8 mm • Packaging under validation • Type of materials • Thickness • Effects of lids RadFETs Packaging The configuration of the packaging of the sensors can modify the chip response, inducing possible errors in the measurements • High integration level up to 10 devices covering from mGy to kGy dose range • Customizable internal layout • Standard external connectivity ~10 mm2 36-pin Al2O3 chip carrier • Radiation Transport Characteristics 0.4 mm Al2O3 • X = 3-4 % X0 • e cut-off  550 KeV • p cut-off  10 MeV • photons transmission  20 KeV • n attenuation  2-3 %

  5. Geant4 Radmon Simulation Radmon Team (CERN PH/DT2 + TS/LEA) and Geant4 Advanced Examples Working Group • Study the effects of different packaging configurations • Energy cut-off introduced by the packaging as a function of particle type and energy • How materials and thickness affect the cut-off thresholds • Spectrum of particles (primary and secondary) hitting the dosimeter volume • Exploit Geant4 functionality • Realistic detector modeling • Selection of physics models • Rigorous software process • In support of the quality of the software results for a critical application • Validation of the simulation • Experimental data: proton beam at PSI, Switzerland • Experimental data: neutrons (Ljubljana TRIGA reactor), in progress

  6. No packaging With packaging With a ceramic or FR4 lid Study of packaging effects • Experimental test • 254 MeV proton beam • Various configurations: with/without packaging, different covers • Measurement: dose in the 4 chips • Simulation • Same set-up as in the experimental test: for validation • Predictive evaluations in other conditions

  7. Packaging REM-TOT-500 LAAS Geometry Geant4 offers advanced functionality to model the detector geometry precisely The full geometry has been designed and implemented in detail in the Geant4 simulation

  8. Rigorous software process

  9. Physics Electromagnetic validation K. Amako et al., Comparison of Geant4 electromagnetic physics models against the NIST reference dataIEEE Trans. Nucl. Sci., Vol. 52, Issue 4, Aug. 2005, 910-918 • Electromagnetic physics • Low Energy-Livermore processes for electrons and photons • Standard model processes for positron • Low Energy ICRU 49 parameterisation for proton & ion ionisation • Multiple scattering for all charged particles • Secondary particle production threshold = 1 mm • Hadronic interactions • Neutrons, protons and pions • Elastic scattering • Inelastic scattering • Nuclear de-excitation • Precompound model • Binary Cascade model up to E = 10 GeV • LEP model between 8 GeV and 25 GeV • QGS model between 20 GeV and 100 TeV • Neutron fission and capture • a particles • Elastic scattering • Inelastic scattering with Tripathi, IonShen cross sections • BinaryIonModel between 80 MeV and 10 GeV • LEAlphaIneslatic model • Decay Hadronic validation In progress See “Systematic validation of Geant4 electromagnetic and hadronic models against proton data” in NSS session N22 See other talks in N38

  10. Primary particle generation • Monocromatic particle beam • Protons: • 254 MeV (experimental) • 150 MeV • 50 MeV • Other particles, variable energy • Energy spectrum • Reactor neutron spectrum • Photon background spectrum at Ljubljana TRIGA reactor Geometrical acceptance  7%

  11. Front incident p – No packaging Front incident p - 520 mm Alumina lid Front incident p - 780 mm Alumina lid Front incident p - 2340 mm Alumina lid 254 MeV p Average energy deposit (MeV) Test beam at PSI • 254 MeV protons • Front/back illumination • Various materials and thicknesses • Measurement: dose Experimental data No significant effects observed with different packaging Geant4 simulation in agreement with experimental data: Kolmogorov testp-value = 0.416for not observing any material/thickness dependence

  12. Complementary validation studies • Systematic validation of Geant4 electromagnetic physics • Amako, S. Guatelli, V. Ivanchenko, M. Maire, B. Mascialino, K. Murakami, L. Pandola, S. Parlati, M. G. Pia, M. Piergentili, T. Sasaki, L. Urban, Validation of Geant4 electromagnetic physics versus the NIST databases, IEEE Trans. Nucl. Sci. 52-4 (2005) 910-918 • Validation of the proton Bragg peak • Reference data from CATANA (INFN-LNS Hadrontherapy Group) • Systematic and quantitative validation of Geant4 electromagnetic and hadronic physics • And others in progress

  13. Packaging + ceramic front cover Front incident p - Packaging + 520 mm Alumina Front incident p - Packaging + 2340 mm Alumina Front incident p - Packaging + 3000 mm Alumina Front incident p - Packaging + 4000 mm Alumina 50 MeV p Visible effects at low energy Average energy deposit (MeV) Effects predicted at various proton energies Predictive power of the simulation to investigate the effects of the packaging at various proton energies Study the effect for 50 MeV, 150 MeV protons Study of the effect of the front lid 254 MeV Al203 lid 254 MeV FR4 lid 150 MeV Al2O3 lid 50 Mev Al203 lid Average energy deposit (MeV) Al2O3 lid thickness (μm)

  14. Simulation protons Energy deposit per event (MeV) 260 μm thick Al2O3 lid 2.34 mm thick Al2O3 lid Packaging + Ceramic front cover Proton energy (MeV) Simulation Simulation p+ electrons 260 μm thick Al2O3 lid 780 μm thick Al2O3 lid 2.34 mm thick Al2O3 lid 260 μm thick Al2O3 lid 2.34 mm thick Al2O3 lid Energy deposit per event (MeV) Energy deposit per event (eV) Pion+ energy (MeV) Electron energy (keV) Thresholds for radiation background detection Work in progress

  15. Neutron energy spectrum d(flux) / dE [n / MeV cm2 s] Energy (MeV) JSI TRIGA neutron reactor facility Photon energy spectrum Study the RadFET response to neutrons • Evaluate the contamination from photons in the JSI test data

  16. Packaging + Ceramic front cover neutrons Average energy deposit (eV) Experimental data RadFET calibration vs. experimental data Al2O3 thickness (mm) photons Average energy deposit (eV) Al2O3 thickness (mm) Preliminary results 260 μm thick Al2O3 lid 2.34 mm thick Al2O3 lid Work in progress Quantitative analysis

  17. Conclusion • Radiation monitoring is a crucial task for LHC commissioning and operation • Optimisation of radiation monitor sensors in progress • packaging is an essential feature to be finalized • Geant4 simulation for the optimisation of radiation monitor packaging • full geometry implemented in detail • physics selection based on sound validation arguments • direct experimental validation against test beam data • First results: proton data • packaging configurations: materials, thicknesses • predictive power of the simulations: effects visible at low energy • Work in progress: neutron data • first results available, further in depth studies to verify experimental effects • Evaluation of particle detection thresholds • Predictive power of the Geant4 simulation tool

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