1. New Geant4 based simulation tools for space radiation shielding and effects analysis.
G.Santin, P Nieminen, H Evans, E Daly
(ESA-ESTEC, Noordwijk, The Netherlands)
F Lei, P R Truscott, C S Dyer
(QinetiQ, Farnborough, England)
B Quaghebeur, D Heynderickx
(BIRA, Brussels, Belgium)
8th Topical Seminar on Innovative
Particle and Radiation Detectors
October 2002
Siena, Italy

2. Space radiation environment
Trapped radiation
Electrons ~< 10 MeV
Protons ~< 102 MeV
Solar radiation
Protons, heavy ions, electrons, neutrons, gamma rays, X-rays…
Cosmic rays
Lower intensity
Heavy ions
G.Santin Siena, 21 Oct 2002
Environment particles cause radiation damage to electronic components, solar cells and materials
Effects include:
Surface charging
Single Event Upset / Latch Up
Increased background
Degradation, dose, solar cell, NIEL
DNA (biological) damage
Other environment components (energetic and low-energy plasma, Oxygen atoms, debris) here neglected

3. Radiation effects and analysis tools
Current tools include:
SPENVIS – models of space environment & basic effects analysis (ESA/BIRA)
CREME96 – Cosmic Ray/SEU analysis (NRL)
SIREST – space environment analysis for Shuttle missions (NASA/LaRC)
SEDAT (Space Environment Data Analysis Tool) – databases of space environment data & tools for analysis. (ESA/RAL)
ESABASE/Radiation Space Systems Analyser …
G.Santin Siena, 21 Oct 2002
The role of
Specific applications developed to address particular items
Trapped/solar radiation, cosmic rays, spacecraft charging
SSAT, CAD Front-End, REAT/MULASSIS
“Generic engineering tool” approach
More detailed analysis tools (ESA/Qinetiq/BIRA)
XMM
The first satellite failure due to total dose was the Telstar. Telstar was launched a day after the July 9, 1962 Starfish nuclear test. The Starfish, a nuclear weapon of 1.4 Megaton strength, was detonated at an altitude of about 325 nmi (above Johnston Island in the Pacific). The explosion produced beta particles (electrons) that were injected into the earth's magnetic field and which formed an artificial radiation belt. This artificial electron belt lasted until the early 1970s. The Telstar experienced a total dose 100 times that expected due to the weapon test. Starfish destroyed seven satellites within 7 months primarily from solar cell damage.

4. SSAT Sector Shielding Analysis Tool
G.Santin Siena, 21 Oct 2002
Geant4 based application
Ray-tracing analysis of a user-defined geometrical configuration
Produces:
distributions of shielding material and thickness as viewed
from a given point within the configuration
as a function of direction from that location.
This approach is highly useful for calculating the absorbed radiation dose, and for finding optimal shielding geometries.

5. Geant4 CAD Front-End tool
Professional CAD tools are common in the aerospace industry
STEP files import
MC-related material information is not included in the STEP file
Materials and Geometry Association (MGA) tool
a Java-based utility
graphical user-interface (GUI)
material definitions
from an existing database of common spacecraft materials
new materials in terms of elemental or nuclear composition.
G.Santin Siena, 21 Oct 2002
South Atlantic Anomaly (SAA)
“Polar horns”
First / Planck
integral
PROBA
rosetta
Used to import the SREM geometry (Standard Radiation Environment Monitor)
SREM is flying on PROBA and INTEGRAL (+ ROSETTA,…)
PROBA

6. CAD Front-End Tool: the SREM case
G.Santin Siena, 21 Oct 2002
SREM geometry imported from STEP files
Comparisons to
Geant3
Calibration data

7. Reat project Radiation Effects Analysis Tools
Develop a new generation of radiation shielding and effect tools for civil space applications
Based on Geant4
Complete treatment of secondary particles
Completeness of physics list
List of sub-projects
MULASSIS (MUlti-LAyer Shielding Simulation S/W):
Geant4 application for dose and particle fluence analysis associated with the use of radiation shields (more advanced than SHIELDOSE).
GeMAT (Geant4-based Microdosimetry Analysis Tool ):
Geant4 application for detailed study of radiation on microelectronic devices.
G.Santin Siena, 21 Oct 2002

8. MULASSIS MUlti-LAyer Shielding Simulation Software
G.Santin Siena, 21 Oct 2002
Need for better description of the impact of space environment on the spacecrafts
Detailed radiation effects analysis in a multi-layer geometry
Increasing mass  secondaries more and more important
Difficult to take into account with analytical models or look-up table approach (SHIELDOSE)
User-friendly (to non C++ programmers)
Basic Space-Environment options included
Integrated into SPENVIS with a WWW interface

9. MULASSIS: Physics lists
Physics description includes
EM (std or LowEnergy extension)
hadron/nuclear interaction (parameterised, precompound)
neutron transport
Kinetic and HETC models coming
for energies ~< 10 GeV/nucleon
G.Santin Siena, 21 Oct 2002

10. MULASSIS: geometry scripting, primaries and visualization
Interactive version
Scripting to build the geometry layers
Predefined or user defined materials
G.Santin Siena, 21 Oct 2002
Titanium
Aluminum
Carbon fiber
Silicon detector
Fig. 2. A screen shot of the MULASSIS visualisation window. The shield shown here is made of three layers (titanium, aluminium and carbon fibre from left to right) and a thin silicon detector layer is placed behind the carbon fibre layer. Superimposed on top of the geometry are the interaction tracks of 1 GeV protons incident from the left.
1 GeV Protons

11. MULASSIS: integration in SPENVIS
First web interface to Geant4!
Geometry definition
Layer number, depth and material
Physics list choice
Primary particle spectrum and fluences from SPENVIS
Trapped protons
Solar protons
Trapped electrons
Analysis options
Pulse Height Spectrum
Ion. dose
NIEL
G.Santin Siena, 21 Oct 2002
Fig. 3. User interfaces in SPENVIS for MULASSIS. All command-line input options have been converted into web-form format. Users can simply fill in their simulation parameters including geometry and material definition, physics module selection and cut-offs, and analysis requirements (as shown in the figure). All fields are with default values or the user can select from a list of predefined values.

12. MULASSIS: an example inside the SPENVIS interface
SPENVIS orbit input parameters
LEO circular orbit
altitude 500 km
inclination 28 deg
G.Santin Siena, 21 Oct 2002
SPENVIS output
Trapped proton and electron fluxes
Solar proton fluence
Trajectory average spectra
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E+05
0.01
0.1 1 10
100
1000
Energy (MeV)
Differential flux (/cm2/s/MeV)
electrons
protons

13. MULASSIS: output Particle fluence Non-ionising energy loss (NIEL)
as a function of particle species, energy, angle and boundary between the layers.
Non-ionising energy loss (NIEL)
based on the fluence and CERN NIEL coefficients.
Energy deposition in the layer or ionising dose in the layer.
Pulse-height energy deposition in the layer.
G.Santin Siena, 21 Oct 2002
Fig. 9. Dose-depth curve in a silicon layer exposed to the trapped electrons. No shielding used in the MULASSIS simulation.
Fig Non-Ionising Energy Loss in the Si detector due to the secondary protons, neutrons and electrons after Al shield of various thicknesses. Damage by protons is dominant, but neutrons make an increasing contribution in thick shield cases.
Doses: ionization
Dose-depth curve
Displacement damage (NIEL)
Si (or Si equivalent)

14. MULASSIS: comparisons
Comparison with SHIELDOSE-2
Total ionising doses for the Si detector behind Al shield of various thicknesses
trapped proton from SPENVIS
G.Santin Siena, 21 Oct 2002
Comparison with MCNPX
Good agreement in secondary radiation spectra
Introduction of kinetic ant HETC models in the next release will eliminate the disagreement in the neutrons
Fig. 8. Total ionising doses for the Si detector behind Al shield of various thicknesses. For comparison doses predicated by SHIELDOSE-2 for the same trapped proton source are also plotted.
Fig. 5. Secondary particle fluence energy spectra behind a 1mm aluminium shield. The incident particles are the trapped electrons for one year as also shown in the figure. The spectra were produced by simulation using 107 electrons. Fluctuations at the low energy end of the spectra are statistical. Also shown in the figure are the MCNPX derived electron and gamma ray spectra. Excellent agreement has been achieved between the two gamma ray spectra, but a factor of 2 difference is observed in the emerging electron spectra.
Fig. 6. A comparison of the secondary proton and neutron spectra derived by MULASSIS and MCNPX simulations. Trapped protons are the incident particle. Overall agreement is achieved, for the protons in particular. There are some differences in the neutron spectra and this is a reflection of the different physics model used in the two codes, Pre-Compound model in the case of MULASSIS and HETC intra-nuclear cascade model in the MCNPX code.

15. GeMAT Geant4-based Microdosimetry Analysis Tool
G.Santin Siena, 21 Oct 2002
Simulate microdosimetry in geometries representing features of a semiconductor device (transistor/junction geometries)
Proton (nuclear and electromagnetic), and electron interactions in the energy range applicable to microdosimetry effects induced by the space radiation environment
Analysis includes
single event effects in semiconductor devices
simultaneous energy deposition in several sensitive regions
Prototype ready
Will be integrated into the ESA SPENVIS web-based space environment simulation tool-set

16. Future developments SpaceGRID
Space science, Earth observation, Space weather and Spacecraft engineering
MULASSIS is being ported to the GRID
Prototype ready
New ESA contract: Energetic Particle Shielding and Interactions Software, major R&D item.
5 ESA Science missions
5 other activities for Geant4 development and applications
G.Santin Siena, 21 Oct 2002
ESA’s SpaceGRID
Dozens of satellites are constantly collecting data about our planetary system - the Earth in particular - 24 hours a day 365 days a year. Satellite data is used for many purposes, for example for telecommunications, navigation systems and environmental monitoring. However, even with the most powerful computers processing all this data is time-consuming and expensive. Distributing these tasks over a number of low-cost internet-connected platforms would provide enormous potential, at a relatively low cost, for many space applications.
To look into this exciting possibility ESA is about to begin work on its SpaceGRID project. This will be run by an international consortium of industry and research centres led by Datamat (Italy). Other members include Alcatel Space (France), CS Systemes d’Information (France), Science Systems Plc (UK), QinetiQ (UK) and the Rutherford Appleton Laboratory of the UK Council for the Central Laboatory of the Research Councils.
The project aims to assess how GRID technology can serve requirements across a large variety of space disciplines, sketch the design of an ESA-wide GRID infrastructure, foster collaboration and enable shared efforts across space applications. It will analyse the highly complicated technical aspects of managing, accessing, exploiting and distributing large amounts of data, and set up test projects to see how well the GRID performs at carrying out specific tasks in Earth observation, space weather, space science and spacecraft engineering.
The results of the study should be available within 18 months, but meanwhile ESA will be kept informed of the progress being made and project activities will be synchronised with the ESA internal GRID initiative.
Two other aspects of this project are of particular importance for ESA: finding a way to ensure that the data processed by the SpaceGRID can be made available to public and educational establishments, and ensuring that SpaceGRID activities are coordinated with other major international initiatives. This is one reason why the October meetings of the DataGRID and the Global Grid Forum are of particular interest to ESA.

17. Summary Geant4 Space Users’ Forum 20-22 January 2003 at ESTEC:
Role of Geant4 in the space domain
SSAT, CAD Front-End tool, MULASSIS, GeMAT
Future developments (SpaceGRID, …)
Geant4 Space Users’ Forum January 2003 at ESTEC:
G.Santin Siena, 21 Oct 2002