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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
Maria Grazia Pia
Solid State Radiation Sensor GroupSolid State Radiation Sensor Group
Evaluation of various radiation monitoring detectors
Optimisation Experimental measurements + simulation
Maria Grazia Pia
(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
Maria Grazia Pia
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
Maria Grazia Pia
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
Maria Grazia Pia
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
Maria Grazia Pia
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
Maria Grazia Pia
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
Maria Grazia Pia
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
Maria Grazia Pia
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
Maria Grazia Pia
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
Maria Grazia Pia
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
)
Maria Grazia Pia
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
Maria Grazia Pia
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
)
Maria Grazia Pia
Summary of the simulation resultsSummary of the simulation results
Packaging + ceramic front cover
50 MeV p
254 MeV p
150 MeV p
Preliminary!
Maria Grazia Pia
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!
Maria Grazia Pia
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
Maria Grazia Pia
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
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