Simulation for LHC Radiation Background Optimisation of monitoring detectors and experimental validation M. Glaser1, S. Guatelli2, B. Mascialino2, M. Moll1, M.G. Pia2, F. Ravotti1 1 CERN, Geneva, Switzerland 2 INFN Genova, Italy IEEE Nuclear Science Symposium San Diego, CA 30 October 4 November 2006
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
Solid State Radiation Sensor Group Evaluation of various radiation monitoring detectors Optimisation Experimental measurements + simulation www.cern.ch/lhc-expt-radmon/ Sensor Catalogue 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) 2 x p-i-n diodes (1-MeV [REM, UK and LAAS, France] eq ) 1 x Silicon detectors (1-MeV [CMRP, AU and OSRAM BPW34] eq ) [CERN RD-50 Mask]
RadFETs Packaging The configuration of the packaging of the sensors can modify the chip response, inducing possible errors in the measurements Commercial packaging cannot satisfy all the experiments requirements (size/materials) Development & study in-house at CERN 1.8 mm High integration level ~10 mm2 36-pin Al2O3 chip carrier up to 10 devices covering from mgy to kgy dose range Customizable internal layout Standard external connectivity Packaging under validation Type of materials Thickness Effects of lids Radiation Transport Characteristics 0.4 mm Al2O3 X = 3-4 % X0 e cut-off 550 KeV p cut-off 10 MeV photons transmission n attenuation 2-3 % 20 KeV
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
Study of packaging effects Experimental test 254 MeV proton beam Various configurations: with/without packaging, different covers Measurement: dose in the 4 chips Simulation 1. Same set-up as in the experimental test: for validation 2. Predictive evaluations in other conditions No packaging With packaging With a ceramic or FR4 lid
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 Packaging REM-TOT-500 LAAS
Rigorous software process
Physics Electromagnetic validation K. Amako et al., Comparison of Geant4 electromagnetic physics models against the NIST reference data IEEE Trans. Nucl. Sci., Vol. 52, Issue 4, Aug. 2005, 910-918 Electromagnetic physics 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 Hadronic validation In progress Systematic validation of Geant4 electromagnetic and hadronic models against proton data 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 particles Elastic scattering Inelastic scattering with Tripathi, IonShen cross sections BinaryIonModel between 80 MeV and 10 GeV LEAlphaIneslatic model Decay
Primary particle generation Monocromatic particle beam Protons: 254 MeV (experimental) 150 MeV 50 MeV Geometrical acceptance 7% Other particles, variable energy Energy spectrum Reactor neutron spectrum Photon background spectrum at Ljubljana TRIGA reactor
Test beam at PSI 254 MeV protons Front/back illumination Various materials and thicknesses Measurement: dose Front incident p No packaging Front incident p - 520 m Alumina lid Front incident p - 780 m Alumina lid Front incident p - 2340 m Alumina lid 254 MeV p Experimental data Average energy deposit (MeV) No significant effects observed with different packaging Geant4 simulation in agreement with experimental data: Kolmogorov test p-value M. Glaser, G. Guatelli, B. Mascialino, M. Moll, M.G. = Pia,0.416 F. Ravotti for not observing any material/thickness dependence
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
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 m Alumina m Alumina m Alumina m Alumina 50 MeV p Average energy deposit (MeV) Front incident p - Packaging + 520 Front incident p - Packaging + 2340 Front incident p - Packaging + 3000 Front incident p - Packaging + 4000 254 MeV 254 MeV 150 MeV 50 Mev Packaging + ceramic front cover Al203 lid FR4 lid Al2O3 lid Al203 lid Visible effects at low energy Average energy deposit (MeV) Al2O3 lid thickness (μm)
Work in progress electrons Simulation protons 260 µm thick Al2O3 lid 2.34 mm thick Al2O3 lid Proton energy (MeV) Simulation Simulation 260 µm thick Al2O3 lid 780 µm thick Al2O3 lid 2.34 mm thick Al2O3 lid M. Glaser, G. Guatelli, B. Mascialino, M. Moll, M.G. (kev) Pia, F. Ravotti Electron energy Energy deposit per event (MeV) Energy deposit per event (ev) Packaging + Ceramic front cover Energy deposit per event (MeV) Thresholds for radiation background detection + 260 µm thick Al2O3 lid 2.34 mm thick Al2O3 lid Pion+ 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 Neutron energy spectrum d(flux)/de[n / MeV cm2 s] d(flux) / de [n / MeV cm2 s] 1.000E+18 1.000E+17 1.000E+16 1.000E+15 1.000E+14 1.000E+13 1.000E+12 1.000E+11 1.000E+10 1.000E+09 1.000E+08 1.000E-06 1.000E-05 1.000E-04 1.000E-03 1.000E-02 1.000E-01 Energy (MeV) Energy (MeV) 1.000E+00 1.000E+01
Preliminary results Average energy deposit (ev) Packaging + Ceramic front cover neutron s 260 µm thick Al2O3 lid 2.34 mm thick Al2O3 lid Al2O3 thickness ( m) RadFET calibration vs. experimental data Work in progress Quantitative analysis Average energy deposit (ev) Experimental data photons Al2O3 thickness ( m)
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