A.Brunengo, INFN Genova - CHEP 2001 Simulation for astroparticle experiments and planetary...
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A.Brunengo, INFN Genova - CHEP 2001
Simulation for astroparticle Simulation for astroparticle experiments experiments
and planetary explorationsand planetary explorations
Tools and applications
A. Brunengo, G. Depaola, R. Giannitrapani, E. Guardincerri, A.S. Howard, F. Longo, R. Nartallo, P. Nieminen, A. Pfeiffer, M.G. Pia, G. Santin
CERN - Univ. Cordoba - ESA - IC London - INFN (Ferrara, Genova, Trieste)
CHEP 2001 ConferenceBeijing, 3-7 September 2001
http://www.ge.infn.it/geant4/lowE/space/index.htmlhttp://www.ge.infn.it/geant4/lowE/space/index.html
A.Brunengo, INFN Genova - CHEP 2001
UKDM, Boulby Mine
…to space
satellitesCourtesy of ESA
ISS
Courtesy SOHO EIT
Solar system explorations
Physics from the eV to the PeV scale
Variety of requirementsfrom diverse applications
For such experiments simulation is often mission critical
Models of detectors, spacecrafts and environments
Borexino
Dark matter and experiments
From deep underground…
Reliability - Rigorous software engineering standards
A.Brunengo, INFN Genova - CHEP 2001
Features of a DM underground detectorFeatures of a DM underground detector
Very Low Background • Go Underground + • Fabricate from low radioactivity materials
Low Threshold Energy • High Sensitivity/Signal output
Clear Discrimination • Dominant backgrounds are -rays• Dark Matter candidate signals should look like Nuclear Recoils
Understanding Systematics • Any measured signal may be caused by rare effects of the detector system
Identifying unknown/irreducible backgrounds
• Photonuclear neutrons• Multiple low energy -interactions
… etc…
Similar characteristics and requirements in underground experiments
Courtesy of S. Magni, Borexino
A.Brunengo, INFN Genova - CHEP 2001
Simulation requirements for a DM detectorSimulation requirements for a DM detector
The following physical processes need to be considered:
• High energy muons• Radioactive Decay Modelling• Compton Scattering• Bremsstrahlung• Photoelectric Effect• Rayleigh Scattering• Photonuclear interactions• Neutron scattering• Ion tracking – to estimate the
recoiling nucleus
Light Collection ModellingDetector Read-Out via PMTs require accurate simulation of optical properties
Electric FieldApplied voltage allows the separation, drift, extraction and subsequent electroluminescence within the gas phase
Requires accurate input in order to accommodate and determine edge effects detector
All of these processes have to be simulated down to below the threshold of the detector, <~1keV
A.Brunengo, INFN Genova - CHEP 2001
Low energy electromagnetic interactionsLow energy electromagnetic interactions
Compton fractions
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
116
132
148
1
641
801
961
1121
1281
1441
1601
1761
1921
2081
2241
2401
2561
2721
2881
Energy (keV)
Frac
tion
To determine the background contribution to a Dark Matter detector it is important to calculate the number of -rays which deposit below 10keV inside the sensitive volume
Primary energy of the s with their fractional contribution to the deposition below 10keV
e,down to 250 eV (EGS4, ITS to 1 keV, Geant3 to 10 keV)Based on evaluated data libraries
A.Brunengo, INFN Genova - CHEP 2001
MuonsMuons
1 keV up to 1000 PeV scale1 keV up to 1000 PeV scalesimulation of ultra-high energy and cosmic ray physics
High energy extensions based on theoretical models
Optical photonsOptical photons Production of optical photons in HEP detectors is
mainly due to Cherenkov effect and scintillation
Processes in Geant4:Processes in Geant4:- in-flight absorption- Rayleigh scattering- medium-boundary interactions
(reflection, refraction)
Photon entering a light concentrator CTF-Borexino
A.Brunengo, INFN Genova - CHEP 2001
ZEPLIN III GeometryZEPLIN III Geometry
39
0.5
ø560
ø422
OD 706
42
5
OD 760
Floor Level
36
5
110
0
Z3.00.00.00
Components modelled with
Simplified version to be released as a Geant4 advanced example
A.Brunengo, INFN Genova - CHEP 2001
Backgrounds in an underground detector: simulation stages
TransportTransport is then required through the detector geometry into the active volume
The energy depositionenergy deposition in this volume is converted into scintillation photonsscintillation photons
Ray tracingRay tracing is applied to determine the number of photons reaching the PMT array
DAQ type digitisationdigitisation is then applied to the photon levels to include effects of Poisson statistics, Time Profile, Noise, Limited ADC Range etc…..
Muons trackedMuons tracked through the rock into the underground cavern – an average chemical compositionchemical composition of the rock should be adequate
Reproduce local environmentlocal environment impinging on the detector
Additional contributions to detector background will come from the radioactive isotope compositionradioactive isotope composition of the construction materials – both internally and externally of the detector system – (RRadioactive adioactive DDecayecay)
SStore tore energy depositionenergy deposition in veto to remove higher energy events
High energy muons and neutrinos inputted at the surface
A.Brunengo, INFN Genova - CHEP 2001
Solar flare electrons,protons, and heavy ions
Jovianelectrons
Solar flare neutronsand -rays
SolarX-rays
Galactic and extra-galacticcosmic rays
Induced emission
(Neutrinos)
Trapped particles
Anomalouscosmic rays
Space radiation environment
Photons: ~300 eV < E < 20 MeV
Electrons: ~10 keV < E < 20 MeV
Protons: ~10 keV < E < 20 MeV
Ions: ~10 keV < E < 20 MeV
A.Brunengo, INFN Genova - CHEP 2001
Sources Cosmic Rays Radiation Belts (electrons, protons,..) Solar Events …
Effects need careful assessment and analysis, e.g.: Single Event Upsets and total dose in sensitive electronic components Detector “background” effects (many mechanisms) Electron-induced electrostatic charging inside spacecraft Astronaut hazards: radiation effects at cellular and DNA level
Analysis of payloads needed, e.g.: astrophysics mission (, X, UV, vis, IR,…) detectors
Analysis of shielding needed
Radiation in SpaceRadiation in Space
A.Brunengo, INFN Genova - CHEP 2001
Sector Shielding
Analysis ToolCAD tool front-end
Delayed
radioactivity
General purpose source particle module
INTEGRAL and other science missions
Instrument design purposes Dose calculations
Particle source and spectrum
Geological surveys of solar system
Modules for space applicationsModules for space applications
Low-energy Low-energy e.m. extensionse.m. extensions
Courtesy of P. Nieminen, ESA
A.Brunengo, INFN Genova - CHEP 2001
General Source ParticleGeneral Source Particle
It allows the user to define his/her source particle distribution (without the need for coding) in terms of the following:
• Spectrum : linear, exponential, power-law, black-body, or piece-wise linear (or logarithmic) fit to data
• Angular : unidirectional, isotropic, cosine-law, or arbitrary (user-defined)
• Spatial sampling : from simple 2D or 3D surfaces, such as discs, spheres, boxes, cylinders
The GSPM also provides the option of biasing the sampling distribution.
A.Brunengo, INFN Genova - CHEP 2001
X-ray astrophysicsX-ray astrophysics
Credit: ESA
Low energy protons (< 1.5 MeV) can damage CCDs of X-ray telescopes
Chandra X-ray Observatory Status Update
September 14, 1999 MSFC/CXC
CHANDRA CONTINUES TO TAKE SHARPEST IMAGES EVER; TEAM STUDIES INSTRUMENT DETECTOR CONCERN
Normally every complex space facility encounters a few problems during its checkout period; even though Chandra’s has gone very smoothly, the science and engineering team is working a concern with a portion of one science instrument. The team is investigating a reduction in the energy resolution of one of two sets of X-ray detectors in the Advanced Charge-coupled Device Imaging Spectrometer (ACIS) science instrument. A series of diagnostic activities to characterize the degradation, identify possible causes, and test potential remedial procedures is underway. The degradation appeared in the front-side illuminated Charge-Coupled Device (CCD) chips of the ACIS. The instrument’s back-side illuminated chips have shown no reduction in capability and continue to perform flawlessly.
Relevant effects of space radiation background
LowEprotons
A.Brunengo, INFN Genova - CHEP 2001
XMM was launched on 10 December 1999 from Kourou
EPIC image of the two flaring Castor components and the brighter YY Gem
Courtesy of
ResultsResultsCourtesy of R. Nartallo, ESA
XMM-Newton
-4-2024
-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10
Z (cm)
Y (
cm)
RGS EPICFocal plane hits
A.Brunengo, INFN Genova - CHEP 2001
astrophysicsastrophysics--ray burstsray bursts
AGILE
GLAST
Typical telescope: Tracker Calorimeter Anticoincidence
conversion electron interactions multiple scattering-ray production charged particle tracking
GLAST
XML: see talk by R. Chytrachek
GLAST
Mission critical!
A.Brunengo, INFN Genova - CHEP 2001
Polarised Gamma AstrophysicsPolarised Gamma Astrophysics
Compton astrophysics (MeV region)Emission mechanisms
- Synchrotron Radiation, Bremsstrahlung, Compton Scattering, Photon Splitting
Astronomical sites- Synchrotron Radiation, Bremsstrahlung,
Compton Scattering, Photon Splitting
See Kippen (ACT Workshop 2001)
Electromagnetic physics1 keV – 50 MeV
Accurate description of Compton Scattering Compton Scattering – Doppler broadening – Polarization
Hadronic cascades, spallation, isotope production, radioactive decayModels of background Time dependencyInstrumental effects
Simulation RequirementsSimulation Requirements
See Review by Lei, Dean & Hills (1997)
A.Brunengo, INFN Genova - CHEP 2001
G4LowEnergyPolarizedComptonG4LowEnergyPolarizedCompton
250 eV -100 GeV
y
O z
x
h
h A
C
Polar angle
Azimuthal angle
Polarization vector
22
0
020
220 cossin2
h
h
h
h
h
hr
2
1
d
d
Sample Methods: Integrating over • Sample • - Energy Relation Energy• Sample of from P() = a (b – c cos2 ) distribution
More details: talk on Geant4 Low Energy Electromagnetic Physics
Other Geant4 Polarised Processes under development
A.Brunengo, INFN Genova - CHEP 2001
Solar system explorationsSolar system explorations
Courtesy SOHO EIT
Cosmic rays,jovian electrons
Solar X-rays, e, p
Study of the elemental composition of planets, asteroids and moons clues to solar system formation
Arising from the solar X-ray flux, sufficient, for the inner planets, to significant fluorescence fluxes to an orbiter
X-ray fluorescence
Significant only during particle events, during which it can exceed XRF
PIXE
Geant3.21
ITS3.0, EGS4
Geant4
C, N, O line emissions included
LowE LowE packagepackage
BepiColomboESA cornerstone mission to Mercury
Courtesy of ESA Astrophysics Z
See also talk on Geant4 Low Energy Electromagnetic Package
A.Brunengo, INFN Genova - CHEP 2001
Advanced examples in Geant4Advanced examples in Geant4
Ni Conical mirrors (7.5 m)Gold coatingSilicon Detectors (50 m)
Lead converterSi detectors (400 m)CsI calorimeterPlastic anticoincidence
Advanced examples in the Geant4 toolkit (since release 3.0)- Advanced features of Geant4 toolkit- Guidance to the selection and use of physics processes in Geant4
Suitability and reliability of Geant4 in a space environment application
A.Brunengo, INFN Genova - CHEP 2001
Geant4 architecture
OO technology
open to extensions and
evolutions
Easy to accomodate
new URs
Software Engineering
Rigorous approach fundamental to mission critical applications
User Requirements• formally collected• systematically updated• PSS-05 standard
Software Process• spiral iterative approach• regular assessments and improvements• monitored following the ISO 15504 model
Quality Assurance• commercial tools• code inspections• automatic checks of coding guidelines• testing procedures at unit and integration level• dedicated testing team
Object Oriented methods• OOAD• use of CASE tools
• essential for distributed parallel development• contribute to the transparency of physics
Use of Standards • de jure and de facto
A.Brunengo, INFN Genova - CHEP 2001
Geant4: the answer?Geant4: the answer?
Unified framework (science, background, instrumental effects)Source & Background modellingDetector descriptionAddresses physics domains typical of astroparticle experiments - High energy muons- Low energy e/photons, ions- Radioactive decay- Hadronic interactions- Optical processes- etc.
Space modules for radiation background studies and shielding optimisationAnalysis tools + simulation Extensive user support to the astroparticle community