R&D on the Geant4 Radioactive Decay Physics Monte Carlo 2010
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Transcript of R&D on the Geant4 Radioactive Decay Physics Monte Carlo 2010
08.10.10| TU Darmstadt | Institut für Kernphysik | Steffen Hauf | 1
R&D on the Geant4 Radioactive Decay PhysicsMonte Carlo 2010
Steffen Hauf, Markus Kuster, Philipp-M. Lang, Maria Grazia Pia, Zane Bell, Dieter H.H. Hoffmann, Georg Weidenspointner, Andreas Zoglauer
Credit: CNES, NASA
08.10.10| TU Darmstadt | Institut für Kernphysik | Steffen Hauf | 2
Introduction
Radioactive decay simulation as part of larger MC code important for variety of applications.
Examples of GEANT4 dosimetry Biophysics Medical physics Accelerator physics (i.e. LHC) Manned space mission (i.e. ISS, Moon,
Mars) Unmanned probes (i.e. JIMO),
observatories (i.e. IXO) National Security ...
08.10.10| TU Darmstadt | Institut für Kernphysik | Steffen Hauf | 3
Introduction
Geant4 radioactive decay simulation originally developed as part of ESA contract.
Uses tabulated data to obtain decay parameters (halflife, branching, levels, intensities).
After decay delegates nucleus and decay products to other Geant4 processes (photo-deexitation) .
RadDecay
Other Processes
Ground State
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Introduction
Problem: Tabulated data is poorly referencedSolution: New database based on current available ENDF data
Combined effort with international nano5 collaboration to create common GEANT4 data model.
Problem: Only sporadic validation of resultsSolution: Comparision with experiments for variety of isotopes.
gamma ray spectroscopy at Oak-Ridge Laboratories
activation and decay experiment at GSI Phelix Laser
Problem: No native support for long term activation
can bias decay times, this removes particles from MC
MEGALib and Cosima have adressed this, include these concepts into nano5
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Problem 1: Data Source
As part of nano5: common GEANT4 data model
Should include references to data origin
Should allow generic unit testing
Should be „easy“ to update Common superstructure but
adaptable for physics process needs
Deviation of energy levels in keV in Geant4 database compared to ENSDF
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Problem 2: Experimental Verification „Simple and General“ approach at Oak Ridge Labs:Use GEANT4 to decay various isotopes in front of Ortec HPGe detector.
We know:•measurement time•isotope•background•detector geometry to certain extentsystematics under controlWe do not want fit using efficiency
Measured so far: 2 2Na, 5 4Mn, 5 6Mn, 5 7Co, 6 0Co, 1 1 6In, 1 3 3Ba
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Effects of Geant4 Version and Physics Settings
Gamma spektrum of 1 3 7Cs for different Geant versions compared to experimental data(gray)Tested: G4.9.1, 4.9.1* w.
Compton mod, G4.9.2
Spectra are very similar for all Geant4 versionstested
Differ in particle speciesproduced (see next slide)
Same trends for deviationfrom experiment
True for other isotopes aswell
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Effects of Geant4 Version and Physics Settings
Gamma spektrum of 1 3 7Cs (black) compared to experimental data(gray)
G4.9.1 low energy physics G4.9.2 low energy physics
Spectrum is very similar but contributing particles (e- blue, photon yellow) change
08.10.10| TU Darmstadt | Institut für Kernphysik | Steffen Hauf | 9
Effects of Geant4 Version and Physics Settings
Gamma spektrum of 1 3 7Cs (black) compared to experimental data(gray)
G4.9.1 low energy physics G4.9.2 standard em physics
Spectrum is very similar but contributing particles (e- blue, photon yellow) change
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Effects of Detector Geometry
Introduction of a „dead“ layer at detector entrance side (i.e. 1 3 7Cs)
Continuum and high energy peak representation improves,low energy peak worsens
sensitivedead
source
d
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Effects of Detector Geometry
Most energy is deposited in front part of HPGe crystal and at outer and bore edge.
In real world detector this area will have strongly curved electric field lines causing non-trivial charge transport and collection
Dead layer shows that selectivly changing efficiency of this region can positively influence modelling of continuum
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Effects of Detector Geometry
Majority of energy is deposited in frontal detector regions
Holds true in continuum and peak areas of spectrum
Cumulative energy deposition in respect to location in detector
entrance window
detector rear
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Laser Accelerated Protons for Testing Activation and Decay Simulation
Target Normal Sheath Acceleration
Proton Spectrum
M. Schollmeier, PhD Thesis TU Darmstadt 2008
M. Roth TU Darmstadt
Parameters
Laser intensity:
Proton flux:
Pulse duration: pico seconds
Parameters
Laser intensity:
Proton flux:
Pulse duration: pico seconds
Simulation Verification
Activation of shielding material
Interaction of MeV protons with
detector and shielding materials
Simulation Verification
Activation of shielding material
Interaction of MeV protons with
detector and shielding materials
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Laser Accelerated Protons for Testing Activation and Decay Simulation
Due to beam problems so far only one preliminary shot on 2.25mm Sn.
Beam time proposal for additional 18 shots at GSI PHELIX laser was handed in
Stacks are halfed: one side Sn target, other side: radiochromatic films and copper absorbers
After shot: gamma spectroscopy in HPGe detector
Sn RC- Stack
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Laser Accelerated Protons for Testing Activation and Decay Simulation
Courtesy: K
. Harres
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Laser Accelerated Protons for Testing Activation and Decay Simulation
Analysis of radiochromatic films results in input spectrum for GEANT4 simulation (solid)
Input in General Particle Source (GPS)
Adequate similarity to cosmic proton spectrum (dotted)
Comparison between cosmic and laser accelerated proton spectrum
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Laser Accelerated Protons for Testing Activation and Decay Simulation
Activation and decay measurement in one run
Simple geometry, add complexity if needed
Physics as used for IXO/Simbol-X simulations (LowEn-EM, hadron)
Only particles with parent process „Radioactive Decay“ are registered.
Protons are „killed“ at boundry Sn-Detector.
Sn
HPGe
p+
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Summary and Outlook
Radioactive decay database needs to be checked for consistenceNew data model which includes references would aid updating and validation
Simple experiment with HPGe detector can be qualatively modelled but simulation isn't completely accurateHPGe simulation is not sensitive to Geant4 version or physics setups (within modest parameter changes)HPGe simulation is sensitive to geometrical changes near detector. Further investigation underway
Additional experiment with laser accelerated protons proposed