Test Beam Simulation for ESA BepiColombo Mission

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Test Beam Simulation for ESA BepiColombo Mission
Monte Carlo 2005 Chattanooga, April 2005
Marcos Bavdaz, Alfonso Mantero, Barbara
Mascialino, Petteri Nieminen, Alan Owens, Tone
Peacock, Maria Grazia Pia
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Mercury

• Observations from Earth are difficult
• Impossible observations from Hubble (optics
  damage)

Interplanetary Spacecrafts 3 fly-by (Mariner
10 - 1974-75)
Atmosphere generated by solar wind
High density (5.3 g/cm3)
Magnetic field ( 330 nT - 1/1000 Earth)
Magnetosphere
Planet formation theories
Water presence at the poles (?)
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Mercury formation
solar system objects
Understanding the formation of
the solar system as a whole

• A number of missions are planned in the coming
  years to measure the fluorescence spectra of
  solar system object, as a method to ascertain
  their composition

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The ESA BepiColombo mission
Two orbiters for a variety of scientific
experiments Magnetic field study - Planet
mapping - Surface study
Named in honour of Giuseppe Colombo
- Planetary evolutionary models - Solar corona
measurements - Precision measurements of general
relativity - Search for Near Earth Objects (NEO)
Launch date 2012
MPO
Mercury Planetary Orbiter
Mercury Magnetospheric Orbiter
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HERMES experiment
Planetary surface composition measurements by
means of X-ray spectrography
Fluorescence spectra EBEAM8.5 keV
Incident Radiation
Fluorescence
Mercury soil
Counts
Solar radiation variability Cosmic Radiation
Energy (keV)
Choice for the most appropriate detector under
study, particularly for GaAs.
Detector for incident radiation monitoring
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Mission related problems

• Poor knowledge and no control on the measurement
  environment
• No repair possible in space

Risk Analysis and Mitigation

• FUNCTIONAL REQUIREMENTS
• Fluorescence simulation resulting from atomic
  deexcitation
• Reproduction capability for complex materials,
  like the geological ones
• Geometry detailed description
• Detector features reproduction

• NON-FUNCTIONAL REQUIREMENTS
• Results reliability, by means of
• PHYSICAL VALIDATION
• GRID transposition for statistically
  significant samples production

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The simulation

• It is a - based application for the
  simulation of X-ray emission spectra from rock
  geological samples of astrophysical interest
• The physics involved is based on the

Geant4 Low Energy Electromagnetic Package
Geant4 Atomic Relaxation Package
X-ray Fluorescence Emission model
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The simulation validation

• The simulation has been validated with
  comparison to experimental data taken at Bessy by
  ESA in two different phases

PHASE II
PHASE I
Geological complex samples irradiation
Pure element irradiation
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PHASE I
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Test beam at Bessy - I
Advanced Concepts and Science Payloads
A. Owens, T. Peacock
Monocromatic photon beam
HPGe detector
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Simulation validation - I
Photon energy mean
Experimental data Simulation
Parametric analysis fit to a gaussian Compare
experimental and simulated distributions Detector
effects - resolution - efficiency
difference of photon energies
Precision better than 1
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PHASE II
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Test beam at Bessy - II
Complex geological materials of astrophysical
interest
Advanced Concepts and Science Payloads
A. Owens, T. Peacock
Monocromatic photon beam
Hawaiian basalt Icelandic basalt Anorthosite Doler
ite Gabbro Hematite
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Modeling the experimental set-up
The simulation reproduces
Complex geological materials
Geometry of the experimental set-up
Response and efficiency of the detector
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Simulation design
Detector (Si(Li)) response function and
efficiency reproduction
User-friendly modification of experimental set-up
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Simulation validation - II
The application demonstrates Geant4 capability to
generate the fluorescence spectra resulting from
complex materials
Quantitative analysis comparison on the entire
distribution non-parametric testing techniques
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Statistical analysis
Goodness-of-Fit Statistical Toolkit
Good agreement between simulations and
experimental data (p gt0.05)
Geant4 Atomic Deexcitation Package Physics
Validation
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Fluorescence spectra from Hawaiian Basalt
EBEAM8.3 keV
Quantitative comparisons Hawaiian basalt
Counts
Fluorescence spectra from Hawaiian Basalt
Energy (keV)
simulations experimental
Pearson correlation analysis rgt0.93
plt0.0001
Counts
High statistical correlation between experimental
data and simulations
EBEAM6.5 keV
Energy (keV)
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Simulation results EBEAM6.5 keV

• Differences between simulations and experimental
  data are ascribable to
• - The nominal composition of the rock could be
  different from the real one
• (extra peaks are due to K and L lines of Cr)
• The detector response is unknown at low
  energies
• (E lt 3.5 keV)

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Simulation results EBEAM7.0 keV

• i

Simulation results EBEAM8.3 keV
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Simulation results EBEAM9.2 keV
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DIANE (Distributed Analysis Environment)
Execution time reducion gives fruibility for
application
Complex simulations require long execution time
Integration for the application performed
generally, available for any Geant4 application
DIANE allows GRID usage transaprently
2 tests public cluster (30 35 machines LXPLUS)
and dedicated cluster (15 machines LXSHARE)
Execution times reduction one order of
magnitude (24h 750M events)
IN COLLABORATION WITH JUKUB MOSCICKI
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Rocks X-ray emission library
Space missions are risky, so solid strategies for
risk mitigation are to be undertaken
HERMES EXPERIMENT
It is necessary to study all the possible
responses of the instruments before they are in
flight with a very good precision for all the
possible situations they can find
The simulation development has open the
possibility to create a library of simulated
rocks spectra, to be used as a reference for
various planetary missions
Venus Express
BepiColombo
SMART-1
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CONCLUSIONS

• Creation of rocks libraries of astrophysics
  interest
• simulated spectra are validated with
  respect to experimental data
• Geant4 is capable of generating X-Ray spectra
  for rocks of known composition
• The production of an extensive library is in
  progress

Test beams contributed significantly to the
validation of Geant4 Low Energy Electromagnetic
Package/Atomic Deexcitation
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Future developments
Solar radiation
Mercury incident radiation is composed by
Cosmic radiation
A new model for
VALIDATION

• PIXE

Future test beam
is available in Geant4

• For further informations
• Alfonso.Mantero_at_ge.infn.it