Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Space Specific GEANT4 Modules Reported by: Pete Truscott Space Department DERA, Farnborough UK

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 p-type substrate n-type collector p-type base n-type emitter Recombination centre p-type substrate gate gate oxide source n drain n TID and NIEL in Spacecraft Microelectronics Total ionising dose: Charge collection in insulating or passivation oxide layers: –change voltage thresholds –leakage currents Displacement (NIEL) damage: Carrier traps degrade: –Bipolar transistor gain –Solar cell efficiency –Detector efficiency/resolution

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Shielding Calculations and Optimisation Calculation of total dose: –Detailed simulation over complex 3D geometry –1D shield simulation results and integrate dose contributions over shield distribution (sector shielding analysis) Annual dose predicted for a 1000 km Sun- synchronous orbit Shield optimisation: –Evaluation of Al/Ta graded shields for maximum attenuation of electron dose effects –Detailed EM simulation essential ITS/EGS4 Dose versus Al/Ta shield composition,Shield mass 1.1 g/cm 2. (Comber & Cosby)

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Single Event Effects and Multiple Bit Upsets in Spacecraft Microelectronics n Temporary upset or permanent destruction of microelectronics n Becoming increasingly important due to small feature sizes SEUs in UoSAT 2 nMOS DRAMS showing clustering of proton events in SAA and CR events at high latitude (Underwood, Daly & Herboe-Sorensen) MBU by nuclear recoil proton / neutron nuclear recoil

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Background in Sensors Background spectrum in 7.6cm x 7.6cm BGO 1.86 days after the return of Space Shuttle mission STS-48

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Analysis of X-ray &  -ray emissions n Remote sensing of solar system bodies for surface composition  -ray emissions from induced and natural radioactivity as well as prompt effects n X-ray fluorescence from EM cascades, charged particle ionisation and X-ray induced excitation CR or solar proton  e-e- e+e+ Solar X-ray CR or solar proton 24 Mg(p,3n) 22 Na 28 Si(n,  ) n n n

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Requirements: User Categories n Category A: Spacecraft design, operation and failure analysis –Uses SPARSET as an engineering tool (with little to no software modification) to a variety of spacecraft/sub-system geometries and particle sources –Generation of hardening specs, implementation of hardening strategies, scheduling operations –Quantities of interest: TID, particle flux, NIEL, LET spectra –Some understanding of radiation environment and quantities required n Category B: Design, operation, and data analysis for specialised payloads –Apply SPARSET to specialised payloads sensitive to radiation –Instrument design and optimisation (assessment of detector efficiencies and background), operational planning, and data interpretation using prediction –Particle flux (r, E, , t), LET, PH energy deposition, Cerenkov/scinitillation –Good understanding of environment and effects on his/her instrument, physical interaction processes

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Requirements: User Categories n Category C: Detailed study of radiation effects on components and systems, and hardening –Apply SPARSET to assess different shielding strategies (material composition, order), aid theoretical analysis of component susceptibility, assess accuracy of simulation codes by comparison with empirical data –High level of understanding of radiation environment, interaction processes and how they are implemented in model –Advises on technology choices, best hardening practices, and use of prediction tools such as a SPARSET –Develops SPARSET for Category A/B user as well as for own use –Quantities of interest include: particle flux, LET, spatially correlated PH energy deposition spectra, radionuclide production & distribution, determination of NIEL factors

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Space Specific GEANT4 Modules

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 n Objective & application: –To permit specification of materials data file to augment geometry STEP description –Use with commercial CAD tools for simple geometry description n Functionality: –Extension of GGE –Access to database of standard spacecraft materials –Manual cross-referencing of volumes, materials and visualisation attributes –Automatic cross-referencing of volumes and materials using meta-data flag in the STEP “PRODUCT” field n Dependencies: –Access to “PRODUCT” field information from UserDetectorConstruction n Status: –Delivery due October 1999 CAD Front-End Tool

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Sector Shielding Analysis Tool n Objective & application: –To determine the physical distribution of shielding around a user-defined point in the geometry –First-order assessment of shielding as a function of position n Functionality: –Histogram of fraction of solid angle with shielding within a given interval as a function of shielding interval (+ Poisson errors) –2D Histogram of mean shielding level (in g/cm 2 ) as a function of ( ,  ) (+standard deviation of shielding) –Output as a function of material and/or element n Status: –Code released at beta03 –Upgraded to meet additional user requirements (beta04 RW, beta05 fully STL - latter to be fully tested) –Web-version demonstrated on DERA intranet

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Sector Shielding Analysis Tool

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Low-Energy EM Physics n Objective & application: –To extend EM physics to 250 eV to lepton-photon transport and ~10 eV to hadrons/ions –Induced X-ray fluorescence studies n Functionality: –Use Lawrence Livermore EEDL, EPDL and EADL cross-section libraries for electrons and photons –Positron cross-section libraries from PSI (TBC) n Status: –Implementation for electrons/photons at GEANT4.0.1

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 n Objective: –To permit definition of an arbitrary source distribution without coding n Functionality: –Spatial : point, area source (disc, ellipse, rectangle), or simple volume (sphere, cylinder, RPP) –Angular : unidirectional, isotropic, cosine-law, arbitrary –Energy : mono-energetic, linear, exp, power-law, arbitrary spectrum –Input from output of previous execution (object persistency) –Source particle biasing according to point of origin, first interaction, energy n Dependencies: –“Sourcing” from previous execution depends upon implementation of Retrieve Run and Event objects n Status –Delivery due December 1999 General Source Particle Module

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Radioactive Decay Module n Objective & application: –To allow production of , , and  from radioactive decay, for subsequent tracking –Induced radioactive background studies or determination of solar system body composition from radioactive gamma ray emission n Functionality: –Treatment of decay of radionuclides through multiple generations –Branching ratios and energies from ENSDF –Isomeric transitions use G4DiscreteGammaDeexcitation –Applicable to nuclei in motion or at rest n Dependencies: –Common database source for radioactive decay and photo-evaporation data n Status –Delivery due December 1999

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Event Scoring and Data Output n Objective & application: –To permit selection of standard scoring parameters without coding –Generally applicable to spacecraft studies n Functionality: –Boundary crossing events as a function of species, energy, angle, time, birth- zone, volume/surface of boundary –Energy deposition (calculation of TID, PHS) as function of species, time, birth-zone, volume –correlated energy deposition between volumes for PHS –Output of stopping powers, ranges and interaction cross-sections (as a by- product of simulation) –Application of normalisation factors e.g. to calculate quantity per unit incident particle flux n Dependencies: –Efficiency?

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Spacecraft Radiation Shielding and Effects Toolkit (SPARSET) User interface n Objective & application: –To provide a default user environment for control standard GEANT4 execution without programming, potentially using a GUI –Applicable to all categories of user, especially category A n Functionality: –Selection of geometry and materials –Definition of source particle distribution and normalisation factor –Definition of quantities to be scored –Selection of physics models –Identification of particle cut-offs –Selection of variance reduction schemes –General run parameters

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Variance Reduction n Objective & application: –To extend treatment of variance reduction processes in GEANT4 –Generally applicable for efficient modelling n Functionality: –Control through G4UI –Zone-dependent energy cut-offs –Splitting and Russian roulette at boundary crossings according to zone- dependent importance factor –Path-length stretching and shrinking –Forced interactions –Weight windows n Dependencies –Activities elsewhere in GEANT4 collaboration on variance reduction

Spacecraft Environment & Protection Group GEANT4 Workshop, Noordwijk, Sep 1999 Documentation on DERA/GEANT4 Web-Site