1. A.Brunengo, INFN Genova - CHEP 2001 Simulation for astroparticle experiments and planetary explorations Simulation for astroparticle experiments and 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 Conference Beijing, 3-7 September 2001 http://www.ge.infn.it/geant4/lowE/space/index.html

2. A.Brunengo, INFN Genova - CHEP 2001 UKDM, Boulby Mine …to space satellites Courtesy of ESA ISS Courtesy SOHO EIT Solar system explorations Physics from the eV to the PeV scale Variety of requirements from 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

3. A.Brunengo, INFN Genova - CHEP 2001 Features 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

4. A.Brunengo, INFN Genova - CHEP 2001 Simulation 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 Modelling Detector Read-Out via PMTs  require accurate simulation of optical properties Electric Field Applied 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

5. A.Brunengo, INFN Genova - CHEP 2001 Low energy electromagnetic interactions 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

6. A.Brunengo, INFN Genova - CHEP 2001 Muons 1 keV up to 1000 PeV scale 1 keV up to 1000 PeV scale simulation of ultra-high energy and cosmic ray physics High energy extensions based on theoretical models Optical 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

7. A.Brunengo, INFN Genova - CHEP 2001 ZEPLIN III Geometry Components modelled with Simplified version to be released as a Geant4 advanced example

8. A.Brunengo, INFN Genova - CHEP 2001 Backgrounds in an underground detector: simulation stages Transport Transport is then required through the detector geometry into the active volume energy deposition scintillation photons The energy deposition in this volume is converted into scintillation photons Ray tracing Ray tracing is applied to determine the number of photons reaching the PMT array digitisation DAQ type digitisation is then applied to the photon levels to include effects of Poisson statistics, Time Profile, Noise, Limited ADC Range etc….. Muons tracked chemical composition Muons tracked through the rock into the underground cavern – an average chemical composition of the rock should be adequate local environment Reproduce local environment impinging on the detector radioactive isotope composition Radioactive Decay Additional contributions to detector background will come from the radioactive isotope composition of the construction materials – both internally and externally of the detector system – ( Radioactive Decay ) Store energy deposition Store energy deposition in veto to remove higher energy  events High energy muons and neutrinos inputted at the surface

9. A.Brunengo, INFN Genova - CHEP 2001 Solar flare electrons, protons, and heavy ions Jovian electrons Solar flare neutrons and  -rays Solar X-rays Galactic and extra-galactic cosmic rays Induced emission (Neutrinos) Trapped particles Anomalous cosmic 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

10. 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 Space

11. A.Brunengo, INFN Genova - CHEP 2001 Sector Shielding Analysis Tool CAD 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 applications Modules for space applications Low-energy e.m. extensions Courtesy of P. Nieminen, ESA

12. A.Brunengo, INFN Genova - CHEP 2001 General 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.

13. A.Brunengo, INFN Genova - CHEP 2001 X-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 LowE protons

14. 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 Results Courtesy of R. Nartallo, ESA XMM-Newton RGS EPIC Focal plane hits

15. A.Brunengo, INFN Genova - CHEP 2001  astrophysics  - ray 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!

16. A.Brunengo, INFN Genova - CHEP 2001 Polarised 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 physics 1 keV – 50 MeV Compton Scattering Accurate description of Compton Scattering –Doppler broadening –Polarization Hadronic cascades, spallation, isotope production, radioactive decay Models of background Time dependency Instrumental effects Simulation Requirements See Review by Lei, Dean & Hills (1997)

17. A.Brunengo, INFN Genova - CHEP 2001 G4LowEnergyPolarizedCompton G4LowEnergyPolarizedCompton 250 eV -100 GeV y O z x     h h   A C  Polar angle  Azimuthal angle  Polarization vector Sample Methods: Integrating over  Sample   - Energy Relation  Energy Sample of  from P(  ) = a (b – c cos 2  ) distribution More details: talk on Geant4 Low Energy Electromagnetic Physics Other Geant4 Polarised Processes under development

18. A.Brunengo, INFN Genova - CHEP 2001 Solar 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 package BepiColombo ESA cornerstone mission to Mercury Courtesy of ESA Astrophysics Z See also talk on Geant4 Low Energy Electromagnetic Package

19. A.Brunengo, INFN Genova - CHEP 2001 Advanced examples in Geant4 Ni Conical mirrors (7.5 m) Gold coating Silicon Detectors (50  m) Lead converter Si detectors (400  m) CsI calorimeter Plastic 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

20. 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

21. A.Brunengo, INFN Genova - CHEP 2001 Geant4: the answer? Unified framework (science, background, instrumental effects) Source & Background modelling Detector description Addresses 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 optimisation Analysis tools + simulation Extensive user support to the astroparticle community