GEANT4 Tools for High-energy Astrophysics Instrumentation

Transcription

1 5th GEANT4 Space Users Workshop LA-UR February 13 15, 2008 University of Tokyo, Japan GEANT4 Tools for High-energy Astrophysics Instrumentation R. Marc Kippen Space Science & Applications Group International, Space, & Response Division Los Alamos National Laboratory

2 Outline HEA Mission Drivers Role of simulation & modeling Simulation Requirements Particularly the unique aspects Example from previous work The Role for GEANT4 Fundamental capabilities Augmentation tools Conclusion Future outlook Issues & concerns

3 High-Energy Astrophysics (HEA) Instrumentation Space-based High-energy Astrophysics Defined here to mean X-ray, gamma-ray, and energetic particle astronomy Accelerator experiments in space Currently in a golden age of instruments/data Opportunities & Threats Outstanding potential for scientific breakthroughs Challenging and costly experimental environment Current Missions Near Missions Far Future Missions Con/Gen-X INTEGRAL Swift GLAST Suzaku Nuclear Astrophysics ACT XMM Chandra Marc Kippen BHFP/Exist AstroSat 5th GEANT4 Space User s Workshop, Tokyo, Feb ,

4 General Capabilities Needed for HEA High-energy Radiation Detectors High-energy Measurement Techniques/Optics New techniques/materials for higher energies Lower cost fab/production High efficiency Lower mass Theory, Modeling, Simulation Software / Information Tech. Systems Integration Marc Kippen Si, CdZnTe, Ge Scintillators Pixel or Strip segmentation High efficiency Good energy Resolution Low power Low-noise, low-power readout of large-scale systems Allow compact instrument design ASIC/VLSI Powerful, reconfigurable on-board computing Autonomous systems 5th GEANT4 Space User s Workshop, Tokyo, Feb , Simulation/modeling systems for all phases of development & operation Data and image processing techniques Field deployable autonomous S/W systems Rapid data handling

5 Modeling & Simulation in HEA Instrumentation Primary Uses 1. Early development of instrument concepts Primarily physical simulation studies with crude detector assumptions 2. Development and optimization of engineering systems concepts Physical simulation + engineering simulations Guide development of data analysis systems 3. Demonstrate instrument + Eng. system performance End-to-end performance demonstration 4. Detailed characterization of instrument response for use in flight analysis Benefits 1. Cost-effective means for making quantitative comparisons between different concepts and configurations 2. Early identification of instrument design reduces mission technical risk 3. Early identification and verification of scientific objectives enhances mission/ proposal credibility 4. Provides a crucial test-bed for the development of data processing and analysis algorithms/systems 5. Often the only viable means of evaluating detailed instrument performance for varied conditions Simulation capability particularly crucial for inherently risky space experiments

6 Conceptual HEA Instrument Simulation Framework Orbital Environment Model Mechanical Model(s) Iterate at All Levels Instrument Mass Model Spacecraft Mass Model Background Inputs Science Goal Inputs Physical Simulation Engine Physics Data/Models Instrumental Effects Engine Test Data and/or Models Data Processing and Analysis Auxiliary Data/Models Science Performance Evaluation Credible Simulation Requires Credible Inputs at All Levels

7 HEA Instrument Simulation Requirements Architecture Modern, modular architecture that allows customization for unique mission needs Physical simulation (sources) Need full EM physics in the ~0 ev 0 GeV regime e.g., full details of atomic and nuclear effects, including polarization Sensitive to geometry of active and passive telescope materials Comprehensive mass modeling capability. Ideally tied to engineering CAD tools Physical simulation (backgrounds) Hadronic cascades, spallation, isotope production, radioactive decay, fast & slow neutron physics Time-dependent buildup & decay Flexible input of space environment models Sensitive to geometry of active and passive telescope materials Instrumental effects Application specific Non-ideal resolution, thresholds, noise, crosstalk, etc. Hardware triggers, event selection, coinc/anitcoinc, etc. Low-level ( on-board ) processing Ability to interface with low-level signal processing simulators at different stages of development Account for realistic signal distortion and losses Background rejection techniques and data selections/cuts High-level ( ground ) data analysis Instrument response difficult (or impossible) to fully characterize Many different data types with different response characteristics

8 Example ACT Mission Concept Study ( ) ACT = Advanced Compton Telescope for nuclear (MeV) gamma-ray astronomy Orbital Environment CREME96 Instrument Mass Model ACTmodel Mechanical Model(s) Spacecraft Mass Model ACTtools ACTenvir (Space Environment Models) ACTmodel (Geometry/Materials Models) ACTexamp (Build Tools and Examples) Iterate ACTenvir ACTexamp Science Goal Inputs Monte Carlo GEANT3 MGEANT Instr. Effects MEGAlib Data Analysis Revan Mimrec Science Performance Evaluation Physics Data/Models Test Data and/or Models Auxiliary Data/Models

9 ACT Study Tools & Limitations Monte Carlo Physics 9 8 ACTenvir Space Environment Background Trapped p+ 7 architecture GLECS low-energy Compton physics GCALOR hadronic + neutron physics MGEANT architecture Prompt/ORIHET/Decay radioactive decay interfaces Validated against space instrument data Outdated, rigid architecture (hard to modify) Questionable/limited physics models Lacks modular integration ACTmodel Instrument Model Parameterized mass model to ACT-type experiments Input to MGGPOD/MGEANT Monte Carlo and MEGALib analysis codes Lacks modular integration Specific -1 GEANT Particle Flux (m s-1 GeV sr ) 6 5 CREME96 4 Empirical Model Interface Monte Carlo generators 2 Cosmic Rays p+ Circular LEO 550 km altitude Inclination: Poor architecture based on IDL Lacks modular integration e- e+ HEO Particle Kinetic Energy (GeV) MEGAlib Instrument Effects and Analysis Tied to several MC via codeindependent interfaces Analysis specific to ACT-type experiments Root-based architecture Marc Kippen 5th GEANT4 Space User s Workshop, Tokyo, Feb , 2008 interface Custom 3 - -

10 GEANT4 Role GEANT4 is attractive for future HEA instrumentation needs Modern, adaptable toolkit architecture Comprehensive array of physics models Flexible mass modeling capability (particularly with GDML) Broad user community (including space users!) End goal: replace current disparate toolset with GEANT4-based integrated system Difficulties and missing pieces EM physics Extreme low energy (~0 ev) atomic physics Low-energy Compton with polarization (getting better, e.g., G4LECS & Penelope) Hadronic physics Radioactive decay module included (testing??) Lack of radioactive buildup and time-dependent decay package (analogous to ORIHET/Decay code from Southampton) Validation Costly validation against HEA data required Integrated system including interfaces to space environment source and background models Good, basic capability exists with G4GeneralParticleSource, needs extensions Extended mass modeling, including CAD interfaces needed Built-in parallel processing capability needed

11 Augmentation Tools: G4LECS GLECS = GEANT Low-Energy Compton Scattering Incorporates Doppler broadening into GEANT & GEANT4 Algorithm based closely on EGS Implementation Namito, Ban, & Hirayama, NIM A349, 489 (1994) Relativistic impulse approximation (ignore atomic electron interactions) Uses EPDL for total cross sections Uses EPDL differential cross sections (scattering form factors) Uses shell-wise Compton profiles (Biggs, Mendlesohn, & Mann 1975) to sample Doppler broadened scattered photon energies Also fixes Rayleigh (coherent) scattering physics with EPDL data Computing performance within 2% of G4LowEnergy classes (30% faster than Penelope) Still needed: combined polarization and Doppler broadening Angular Res. (FWHM, deg) Counts (peak normalized) Energy (kev) No Doppler Lead 40 kev Code Validation Data (Namito et al.) G4LECS Sim v4.9.1 G4LowE Sim v4.9.1 Penelope Penelope+G4LECS cm 2 Important for Compton Telescope Simulations Scattered Energy Deposition [kev] 40

12 Working Towards a GEANT4-based Solution GRESS = General Response Simulation System Original purpose: GLAST burst monitor detailed Examples from Detector Validation Library source response function generation Prompt response only (no activation) Extensive γ-ray validation library Radioactive sources 6 kev to 4 MeV Low-energy BESSY synchrotron data (2 20 kev) High-energy van degraf data (4, 6, 11 MeV) Detailed angular/surface response scans Full-spacecraft/instrument + separate Earth scattering simulations Interface to analysis via NASA FITS files Future: Extend GRESS for more general HEA use Marc Kippen Photon Energy [kev] Two-stage Spacecraft Validation Choices of different data types (e.g., spectroscopy vs. tracking instruments) for each volume linked via GDML interfaces Space environment background models via ACTtools-like inputs (or other) Possibly include radioactive decay capability Further validation against space instrument data (e.g., GLAST on-orbit, COMPTEL, etc.) 5th GEANT4 Space User s Workshop, Tokyo, Feb , 2008 BGO NaI Effective Area [cm2]

13 GRESS = General REsponse Simulation System GRESS GRESS/IODA Overlap Area IODA Mass model Cmds. Cal. Params. Cmds. physim root files calsim drmdb Data Analysis Software (IOC) Aux. data Spectrum or DRM caldb drmgen Application Specific DRM Cmds. atmosim Mass model root files arpack Spectrum or ARM armdb NaI Detector #1 (with SC) +90 E γ = 0 kev Source Location Software (SSC & IOC) (Min, Max, Step) -90 (5, 135, 5) cm 2

14 Conclusions & Future Prospects Simulation and modeling are undeniably critical elements in the development of HEA instrumentation GEANT4 offers much capability for a broad range of HEA instrumentation needs It is generally viewed to be the preferred solution, despite on-going use of GEANT3 (for its availability), MCNP/X (for its perceived better neutron physics) Several institutions are pursuing paths towards a comprehensive HEA solution with GEANT4 at the core e.g., SLAC (for GLAST), LANL/GRESS, UC Berkeley (next talk), Naval Research Lab Progress is slow because NASA has been unwilling to support a significant, focused effort (despite repeated tries starting in 1999) The best prospect for funding additional simulation tool development is through specific missions and mission concept studies (e.g., GLAST, ACT, Exist, etc.) Some of these efforts are disparate and unconnected collaboration between missions can lead to long-term capability Multiple packages/solutions from different users are undeniable, but commonality should lead to more efficient solutions (i.e., the toolkit approach)

15 General Suggestions for Future Success Issues & Concerns Enhanced adherence to established standards for inputs & outputs GDML, General Particle Source, Space Environment, for inputs root, FITS, etc. standardized file formats for I/O Includes maintaining and enhancing the above capabilities Improved development and/or understanding of physics models ( lists ) specifically relevant for HEA space instrumentation needs Particularly high-energy physics (prompt activation), neutron cross sections Improved collaboration for sharing models Sources, backgrounds, spatial, spectral, spacecraft mass models, etc. GEANT4 HEA Users Library analogous to IDL astronomy library Need a bridge code to link radioactive buildup and decay simulations