Maria Grazia Pia

Simulation for LHC Radiation Simulation for LHC Radiation

BackgroundBackground

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

R. Capra1, S. Guatelli1, M. Moll2, M. Glaser2, M.G. Pia1, F. Ravotti2

1INFN Genova, Italy 2CERN, Geneva, Switzerland

CHEP 2006Mumbai, 13-17 February 2006

Maria Grazia Pia

Radiation monitoring at LHCRadiation monitoring at LHC

The LHC experiments have considered as a major problemmajor problem

the effect of radiationeffect of radiation on installed equipment from the outset

Necessary to monitor radiation fieldsmonitor radiation fields during early LHC commissioning to prepare for high intensity running and to prepare appropriate shielding or other measures

A lot of interesting work is in progress to ensure that radiation effects do not make LHC commissioning even more difficult than expected

It is essential to have a radiation monitoring system adapted to the needs of radiation tolerance understanding from the first day of LHC operation

Critical issueCritical issue

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Solid State Radiation Sensor GroupSolid State Radiation Sensor Group

Evaluation of various radiation monitoring detectors

Optimisation Experimental measurements + simulation

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(www.cern.ch/lhc-expt-radmon/)

Specifies sensors suitable for dosimetry in the LHC experiments 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]

Further devices under investigation, on-going activity

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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 Calculated 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 %

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

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

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Rigorous software process

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Geant4 Radmon SimulationGeant4 Radmon Simulation

A Geant4 application has been developed to study the effects of different packaging configurations

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

Main objectives:– A quantitative analysis of the energy cut-off introduced by the packaging as a function of

particle type and energy– A quantitative analysis on how materials and thickness affect the cut-off thresholds– A quantitative analysis of the spectrum of particles (primaries and secondaries) hitting the

dosimeter volume as a function of the incoming spectrum

Rigorous software process– in support of the quality of the software results for a critical application

Validation of the simulation– experimental data: p beam at PSI– experimental data: neutrons (Ljubljana), in progress

To be released as Geant4 Advanced

ExampleJune 2006

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Study of packaging effectsStudy of packaging effectsExperimental test

– 254 MeV proton beam– various configurations: with/without packaging, different covers– dose in the 4 chips

Simulation– same set-up as in the experimental test (for validation)– also predictive evaluations in other conditions

No packaging With packaging With a ceramic or FR4 lid

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GeometryGeometryGeant4 simulation

LAAS

REM-TOT-500

Packaging

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

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Primary particle generatorPrimary particle generator

Monocromatic protons beams– 254 MeV (experimental)– 150 MeV– 50 MeV

Protons are generated randomly on a surface of 1.2 cm x 1.2 cm

Geometrical acceptance 7%

fraction of primary particles hitting the sensors

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PhysicsPhysics Electromagnetic physics– Low Energy Livermore for electrons and photons processes– Standard model for positron processes– Low Energy ICRU 49 parameterisation for proton & ion ionisation– Multiple scattering for all charged particles

e/ nuclear physics– Electron Nuclear Reaction for electrons and positrons– Gamma Nuclear Reaction for photons

Hadronic interactions– Neutrons, protons and pions:

Elastic scatteringInelastic scattering

Nuclear de-excitation Precompound model Binary Cascade 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

– Alpha particles: Elastic scatteringInelastic scattering based on Tripathi, IonShen cross sections:

LEAlphaIneslatic model up to 25 GeV BinaryIonModel between 80 MeV and 10 GeV

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” at CHEP06

The secondary production threshold is 1 m

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Experimental dataExperimental data

Results

254 MeV proton beam incident on the sensorsVarious material type and thickness, front/backMeasurement: dose

No significant effects observed with different packaging

RadFET calibration vs. experimental data

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Simulation – 254 MeV p Simulation – 254 MeV p beambeam

No packagingFront packaging + 520 m AluminaFront packaging + 780 m AluminaFront packaging + 2340 m Alumina

Total energy deposit (MeV) per event in the four chips

Front incident p - No packagingFront incident p - PackagingBack incident p - PackagingFront incident p - Packaging + 260 m Alumina

Front incident p – No packagingFront incident p - Packaging + 520 m AluminaFront incident p - Packaging + 780 m AluminaFront incident p - Packaging + 2340 m Alumina

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Simulation – 254 MeV p Simulation – 254 MeV p beambeam

Front incident p - No packagingFront incident p - Packaging + 2500 m AluminaFront incident p - Packaging + 2600 m AluminaFront incident p - Packaging + 2700 m Alumina

Total energy deposit (MeV) per event in the four chips

Front incident p – No packagingFront incident p - Packaging + 200 m FR4Front incident p - Packaging + 400 m FR4Front incident p - Packaging + 600 m Fr4

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Simulation - 254 MeV p beamSimulation - 254 MeV p beam

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

0 500 1000 1500 2000 2500 3000 3500

Alumina thickness (um)

Ene

rgy

depo

sit (

MeV

)

Alumina

FR4

Thickness (m) of the front cover

Tot

al e

nerg

y de

posi

t in

the

chi

ps (

MeV

)

The energy deposit in the chips does not depend on the

configuration of the packaging

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Simulation - 150 MeV proton Simulation - 150 MeV proton beambeam

Total energy deposit (MeV) per event in the four chips

Front incident p - No packagingFront incident p - PackagingBack incident p - PackagingFront incident p - Packaging + 260 m Alumina

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

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Simulation - 150 MeV proton Simulation - 150 MeV proton beambeam

3000

3500

4000

4500

5000

5500

6000

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Alumina thickness (microm)

En

erg

y d

epo

sit

(MeV

)

150 MeV proton

Thickness (m) of the front cover

Tot

al e

nerg

y de

posi

t in

the

chi

ps (

MeV

)

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Simulation - 50 MeV p beamSimulation - 50 MeV p beam

Front incident p - No packagingFront incident p - PackagingBack incident p - PackagingFront incident p - Packaging + 260 m Alumina

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

Total energy deposit (MeV) per event in the four chips

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Simulation - 50 MeV p beamSimulation - 50 MeV p beam

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Alumina thickness (microm)

Ene

rgy

Dep

osit

(MeV

)

50 MeV proton beam

Thickness (m) of the front cover

Tot

al e

nerg

y de

posi

t in

the

chi

ps (

MeV

)

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Summary of the simulation resultsSummary of the simulation results

Packaging + ceramic front cover

50 MeV p

254 MeV p

150 MeV p

Preliminary!

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0

10

20

30

40

50

60

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Alumina layer thickness (um)

% d

iffer

ence

254 MeV

150 MeV

50 MeV

% difference of the energy deposit vs. front cover thickness

% difference: packaging / no packaging

Summary of the simulation Summary of the simulation resultsresults

Preliminary!

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ConclusionConclusionRadiation monitoring is a crucial task for LHC commissioning and operation

Optimisation of radiation monitor sensors in progress– packaging is one of the features to be finalized

Geant4 simulation for the study and optimisation of radiation monitor packaging

– rigorous software process– full geometry implemented in detail– physics selection based on sound validation arguments– direct experimental validation against Radmon data

First results– packaging configurations: materials, thicknesses– no measured effects, simulation in agreement with experimental data– predictive power of the simulations: effects visible at low energy

Work in progress– neutron data– in-depth simulation studies

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IEEE Transactions on Nuclear ScienceIEEE Transactions on Nuclear Sciencehttp://ieeexplore.ieee.org/xpl/RecentIssue.jsp?puNumber=23

Prime journal on technology in particle/nuclear physics

Review process reorganized about one year ago Associate Editor dedicated to computing papers

Various papers associated to CHEP 2004 published on IEEE TNS

Papers associated to CHEP 2006 are welcomePapers associated to CHEP 2006 are welcome

Manuscript submission: http://tns-ieee.manuscriptcentral.com/Papers submitted for publication will be subject to the regular review process

Publications on refereed journals are beneficial not only to authors, but to the whole community of computing-oriented physicists

Our “hardware colleagues” have better established publication habits…

Further info: Maria.Grazia.Pia@cern.ch