a.brunengo, infn genova - chep 2001 simulation for astroparticle experiments and planetary...

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


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


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


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


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


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


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


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


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


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


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


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.


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


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


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!


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)


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


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


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


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


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

a.brunengo, infn genova - chep 2001 simulation for astroparticle experiments and planetary...

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