m. glaser 1 , s. guatelli 2 , b. mascialino 2 , m. moll 1 , m.g. pia 2 , f. ravotti 1

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

Simulation for LHC Radiation BackgroundSimulation for LHC Radiation Background

Optimisation of monitoring detectors Optimisation of monitoring detectors and experimental validationand experimental validation

M. Glaser1, S. Guatelli2, B. Mascialino2, M. Moll1, M.G. Pia2, F. Ravotti1

1CERN, Geneva, Switzerland2INFN Genova, Italy

IEEE Nuclear Science SymposiumSan Diego, CA

30 October – 4 November 2006


Radiation monitoring at LHCRadiation monitoring at LHC

The effect of radiationeffect of radiation on installed equipment is a major issue major issue for for LHC experiments

Necessary to monitor radiation fieldsmonitor 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

A radiation monitoring system adapted to the needs of radiation tolerance understanding

from the first day of LHC operation

Critical issueCritical issue


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

Sensor Sensor CatalogueCatalogue

2 x RadFETs (TID) [REM, UK and LAAS, France]

2 x p-i-n diodes (1-MeV eq) [CMRP, AU and OSRAM BPW34]

1 x Silicon detectors (1-MeV eq) [CERN RD-50 Mask]

Solid State Radiation Sensor GroupSolid State Radiation Sensor GroupEvaluation of various radiation monitoring detectors

Optimisation Experimental measurements + simulation


RadFETs RadFETs PackagingPackaging

Commercial packagingCommercial packaging cannot satisfy all the

experiments requirements(size/materials)

DevelopmentDevelopment & studystudy

in-house at CERN

~10 mm2 36-pin Al2O3 chip carrier

1.8 mm

High integration level

up to 10 devices covering from mGy to kGy dose range Customizable internal layout Standard external connectivity 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 %

The configuration of the packaging of the sensors can modify the chip response, inducing possible errors in the measurements

Packaging under validationPackaging under validation• Type of materials• Thickness• Effects of lids


Geant4 Radmon Geant4 Radmon SimulationSimulationStudy 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

Radmon Team (CERN PH/DT2 + TS/LEA) and Geant4 Advanced Examples Working Group


Study of packaging effectsStudy 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 validation2. Predictive evaluations in other conditions

No packaging With packaging With a ceramic or FR4 lid


GeometryGeometry

LAAS

REM-TOT-500

Packaging

The full geometry has been designed and implemented in detail in the Geant4 simulation

Geant4 offers advanced functionality to model the detector geometry precisely


Rigorous software process


PhysicsPhysicsElectromagnetic 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

– particles Elastic scattering Inelastic scattering with Tripathi, IonShen cross sections

• BinaryIonModel between 80 MeV and 10 GeV • LEAlphaIneslatic model

Decay

Electromagnetic validationK. 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

Hadronic validationIn progress

See “Systematic validation of Geant4 electromagnetic and hadronic models against proton data” in NSS session N22

See other talks in N38


Primary particle generationPrimary 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%


Test beam at PSITest beam at PSI

Experimental data

Front incident p – No packagingFront incident p - 520 m Alumina lidFront incident p - 780 m Alumina lidFront incident p - 2340 m Alumina lid

254 MeV p

Average energy deposit (MeV)

254 MeV protons Front/back illumination Various materials and thicknesses

Measurement: dose

No significant effects observed with different packaging No significant effects observed with different packaging Geant4 simulation in agreement with experimental data: Geant4 simulation in agreement with experimental data:

Kolmogorov testKolmogorov test p-value = 0.416p-value = 0.416 for not observing any material/thickness dependencefor not observing any material/thickness dependence


Complementary validation studiesComplementary 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


Packaging +

ceramic front cover

Effects predicted at various proton Effects predicted at various proton energiesenergies

Al2O3 lid thickness (μm)

Ave

rage

ene

rgy

depo

sit (

MeV

)

Front incident p - Packaging + 520 m AluminaFront incident p - Packaging + 2340 m AluminaFront incident p - Packaging + 3000 m AluminaFront incident p - Packaging + 4000 m Alumina

Average energy deposit (MeV)

50 MeV p

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

Visible effects at low energy

254 MeV Al203 lid254 MeV FR4 lid150 MeV Al2O3 lid 50 Mev Al203 lid


Thresholds for Thresholds for radiation background radiation background detectiondetection

Ene

rgy

depo

sit p

er e

vent

(MeV

)

260 μm thick Al2O3 lid2.34 mm thick Al2O3 lid

Simulation

protons

Proton energy (MeV)

Simulation

Electron energy (keV)

Ene

rgy

depo

sit p

er e

vent

(eV)

electrons260 μm thick Al2O3 lid780 μm thick Al2O3 lid2.34 mm thick Al2O3 lid

+


Pion+ energy (MeV)

Ene

rgy

depo

sit p

er e

vent

(MeV

)

Simulation

Work in progress Packaging

+ Ceramic

front cover


JSI TRIGA neutron reactor JSI TRIGA neutron reactor facilityfacility

Study the RadFET response to neutronsneutrons

– Evaluate the contamination from photons in the JSI test data

Photon energy spectrum

1.000E+08

1.000E+09

1.000E+10

1.000E+11

1.000E+12

1.000E+13

1.000E+14

1.000E+15

1.000E+16

1.000E+17

1.000E+18

1.000E-06 1.000E-05 1.000E-04 1.000E-03 1.000E-02 1.000E-01 1.000E+00 1.000E+01

Energy (MeV)

d(flu

x)/dE

[n /

MeV

cm

2 s

]

Neutron energy spectrum

Energy (MeV)

d(flu

x) /

dE [n

/ M

eV c

m2

s]


Preliminary Preliminary resultsresults


photons

Ave

rage

ene

rgy

depo

sit (

eV)

Al2O3 thickness (m)

Work in progress

Quantitative analysis

RadFET calibration vs. experimental data

Experimental data

Packaging +

Ceramic front cover

Ave

rage

ene

rgy

depo

sit (

eV)

neutrons

Al2O3 thickness (m)


ConclusionConclusionRadiation 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

m. glaser 1 , s. guatelli 2 , b. mascialino 2 , m. moll 1 , m.g. pia 2 , f. ravotti 1

Documents