John Apostolakis & Makoto Asai for the Geant4 Collaboration 1(Draft) SNA-MC 2010

2  IMPACT - Very wide use in diverse fields ◦ 2100 citations for G4 reference paper  Mature Physics modeling in key domains ◦ EM physics from KeV to 100s GeV ◦ Hadron-nucleus models for  Flexibility, Open Source nature have enabled ◦ Creation of applications based on G4 for diverse fields ◦ Embedding in many simulations used in large- scale productions – e.g. for HEP experiments – and investigations of diverse application (e.g. MRED)  Several Physics model improvements ◦ achieved and ongoing

 Significant evolution  New capabilities - highlights  Improvements for challenging use cases  Performance improvements  EM Physics – new models (highlights)  Hadronic Physics model improvement 3(Draft) SNA-MC 2010

 Mature, extensible kernel ◦ Powerful geometry modeler, E/B fields, track stacks  Diverse Physics models (mostly 2 alternatives) ◦ e-/e+/gamma 10s eV-10s MeV (lowE) and kEV-TeV ◦ Hadron-nucleus interactions up to 1 TeV ◦ Neutron interactions from thermal to 1 TeV ◦ Ion-ion interaction from GeV to 100s GeV (TBC ) ◦ Optical, weak (decay of unstable and radioactivity)  Product of collaboration of 85 contributors ◦ Effort comes from HEP Labs & funding agencies (75%), Biology/medical physics (15-20%), space (5- 10%) (Draft) SNA-MC 20104

Improved ‘parallel’ geometries Scoring via commands (script or interactive) Propagating track errors (back/forward in time) Adjoint/Reverse Monte Carlo (Draft) SNA-MC 20105

 Joint navigation in two or more geometries ◦ Step is limited by first boundary found ◦ Extends earlier case-by-case abilities (1998, 2003)  Many uses in toolkit already ◦ Materials (‘mass’ geometry) – used for physics ◦ Scoring / tallying ◦ Importance biasing and weight window ◦ Shower parameterisation (and other fast simulation)  Flexible framework – other additions possible 6(Draft) SNA-MC 2010

 Scoring of tallies redesigned, extended ◦ Covers energy deposition, dose, fluence,...  Interactive commands or scripts can drive: ◦ Start/end of scoring ◦ Location, orientation of meshes  Results can be visualised and written out.  Scoring via user-defined hits is still possible ◦ Used for specialised applications, detectors. 7(Draft) SNA-MC 2010

 Tracking e-/gamma/proton back in time ◦ from sensitive target volume ◦ to an extended source(s).  Adjoint MC ◦ Continuous gain of energy ◦ Multiple scattering ◦ Discrete ionisation, bremsstrahlung, Compton, photo-electric  Test cases show 5-15% accuracy ◦ faster for small target.  With thanks to M. Results for electron exp(-E/2MeV) spectrum 8(Draft) SNA-MC 2010

9

 Undertaken in close collaboration with key user communities ◦ Used modern tools (igprof, FAST, perfmon2) to measure CPU & memory use  Leading performance improvements: ◦ 25% from improvements in Bertini (2008) ◦ 25% from improved interpolations for low-energy processes. ◦ 15% from new error estimation in field integration (2009) ◦ 5-10% from memory allocation in various places.  Enabled the use of improved physics modeling in large scale productions (e.g. use of Bertini casc.) ◦ For the CPU-time cost which used to be needed just for simpler, less precise modeling  e.g. parameterised models in QGSP physics list for E<~18 GeV 10(Draft) SNA-MC 2010

 Navigation in a regular grid of voxels is greatly improved ◦ No longer is there a penalty of large memory use.  New capability to ignore boundaries between voxels with the same material and density ◦ Speedups of 3-4 found in CT-scan use case with 40 “materials” by skipping boundaries.  Reference NSS 2008 proceedings  Similar methods used in GATE (6.0) 11(Draft) SNA-MC 2010

 2000: first distributed-memory Parallel Geant4 ◦ ParGeant4 developed and released in G4 4.0 (tbc) 2003  Challenge: reduce memory use for large applications used in parallel ◦ Multi-process: use copy-on-write ◦ Multi-threading: developed prototype multi- threaded Geant4, sharing the physics tables and geometry (Draft) SNA-MC

13(Draft) SNA-MC 2010

 Improvement of multiple scattering ◦ New step limitation, additional models ◦ Greater stability of results with parameter variation  Convergence on single model design ◦ Enable anyone to combine EM models for a process from any in the ‘old’ lowE and Standard packages.  Validation extended ◦ Suite of 15 tests and over 200 thin-target cases ◦ Regular regression cross-checks for EM calorimeter performance (Draft) SNA-MC

(Draft) SNA-MC

 Established as the leading tool for the simulation of detector response for High Energy Physics (HEP) experiments ◦ Used at ATLAS, CMS and LHCb as the production simulation (the fourth large LHC experiment is preparing to use it in production) ◦ Used in a large number of smaller experiments, in nuclear physics, dark matter searches,..  Widely used in medical applications ◦ Radiotherapy (external and brachytherapy) ◦ Medical imaging  Space ◦ Satellite electronics radiation assessment ◦ Planetary science applications. 16(Draft) SNA-MC 2010

Domain-specific tools, using Geant4 as engine and adding capabilities for the domain:  Geant4 Application for Tomographic Emmision ◦ GATE 6.0 expanded to dosimetry  G4BEAMLINE and BDS-SIM ◦ Simulation of accelerator beamlines  Ptssim, GAMOS ◦ Target radiotherapy 17(Draft) SNA-MC 2010

 Many detectors tested with extensive test beams ◦ Detailed description of geometry, signal collection, response of electronics ◦ Combined testing of full detector segments  Simultaneous description (using one physics list, QGSP_BERT) of ◦ Energy response (to 3% in Atlas test beams) ◦ Energy resolution (to 10%) ◦ Shower shape (to ~10-30% at 10 lambda)  The simulation of the full detector is now showing similar physics performance 18(Draft) SNA-MC 2010