Gabriele Cosmo
187 lines
7.2 KiB
Plaintext
187 lines
7.2 KiB
Plaintext
-------------------------------------------------------------------
|
|
|
|
=========================================================
|
|
Geant4 - an Object-Oriented Toolkit for Simulation in HEP
|
|
=========================================================
|
|
|
|
eROSITA fluorescence
|
|
--------------------
|
|
|
|
Authors:
|
|
|
|
Dieter Schlosser (pnSensor, Munich),
|
|
Georg Weidenspointner (MPE Garching and MPI Halbleiterlabor, Munich),
|
|
Maria Grazia Pia (INFN Genova)
|
|
Francesco Longo (INFN Trieste)
|
|
Andrea Polsini (Università degli Studi di Trieste)
|
|
|
|
Main references:
|
|
|
|
M. G. Pia et al., 2009, "PIXE Simulation With Geant4",
|
|
IEEE Trans. Nucl. Sci., vol. 56, no. 6, pp. 3614-3649
|
|
|
|
N. Meidinger et al., 2010, "Development of the focal plane PNCCD
|
|
camera system for the X-ray space telescope eROSITA", Nuclear
|
|
Instruments and Methods in Physics Research A 624, 321-329
|
|
|
|
Web site:
|
|
|
|
http://www.ge.infn.it/geant4/physics/pixe/erosita.html
|
|
|
|
Contact person:
|
|
Francesco Longo, francesco.longo@ts.infn.it
|
|
|
|
---- OVERVIEW ----
|
|
|
|
This example demonstrates:
|
|
- the generation of XRF and PIXE,
|
|
- how to use different physics processes from those encompassed in the
|
|
Geant4 toolkit in a simulation application.
|
|
|
|
The examples/advanced/eRosita/application directory contains files pertinent
|
|
to the experimental simulation model.
|
|
|
|
The physics capabilities and validation of the physics processes used in this example
|
|
are documented in the PHYSICS REFERENCES section below.
|
|
|
|
---- EXAMPLE DESCRIPTION ----
|
|
|
|
This is example is based on simulations of the instrumental background
|
|
of the eROSITA X-ray telescope, in particular the strength of
|
|
fluorescence lines inside the passive graded Z shield. The set-up
|
|
considered in this example consists of a Cu block that is irradiated
|
|
with protons. Impact ionization of Cu atoms generates vacancies in
|
|
atomic shells. These are then filled by atomic de-excitation,
|
|
resulting in the emission of fluorescence photons and Auger electrons
|
|
- the PIXE (particle induced X-ray emission) process. In particular
|
|
fluorescence photons are then detected with a Si CCD positioned next to
|
|
the Cu block.
|
|
|
|
The simulated set-up is defined in eRositaDetectorConstruction.
|
|
The Cu block is located at position x = y = z = 0 cm. Its dimensions
|
|
in x, y, and z are 0.5 cm * 0.5 cm * 3 cm. The CCD, represented by a
|
|
slab of Si, is positioned at x = z = 0 cm and y = 2 cm. The CCD dimensions
|
|
in x, y, z and are 4 cm * 450 mu_m * 4 cm.
|
|
|
|
The vertex and initial momenta of the protons are defined in
|
|
eRositaPrimaryGeneratorAction. The vertex is at x = 0 cm, y = 2.25
|
|
cm, and z = 4 cm. The initial direction of the protons is given by the
|
|
vector (0.0, -0.5, -1.0). The initial kinetic energy of the protons is
|
|
150 MeV.
|
|
|
|
The physics processes relevant to this simulation are defined in
|
|
eRositaPhysicsList. The key process for generation of PIXE is
|
|
G4hImpactIonisation. In the example, proton cross sections based on
|
|
the ECPSSR model are used. Cross sections are computed for an energy
|
|
range from 1 keV to 200 MeV. The energy thresholds for the production
|
|
of fluorescence photons and Auger electrons by PIXE are set to a value
|
|
of 250 eV.
|
|
|
|
The output of the example is an ASCII file named
|
|
TrackerPhotonEnergy.out. It contains the energy, in MeV, of every
|
|
photon that finds its way to the tracker (or which is created as a
|
|
secondary inside the tracker). If the batch mode example is run, the
|
|
entries 0.00798467, 0.00800571, and 0.00886534 correspond to Cu
|
|
fluorescence lines K_alpha2, K_alpha1, and K_beta1,
|
|
respectively. Other photons originate e.g. from bremsstrahlung of
|
|
delta rays in Cu. A histogram of the energies in
|
|
TrackerPhotonEnergy.out, in particular if generated for more protons,
|
|
clearly shows the PIXE photons from Cu on top of a continuous
|
|
distribution.
|
|
|
|
|
|
Instructions on how to build and run the example:
|
|
|
|
- To compile the example:
|
|
% cd eRosita
|
|
% make
|
|
If the environment variable G4WORKDIR and has been defined, an executable
|
|
named eRosita will be generated in $G4WORKDIR/bin/$G4SYSTEM
|
|
|
|
- To run the example:
|
|
|
|
Do not forget to define the G4PIIDATA environment variable as appropriate
|
|
to get access to the PIXE data library (e.g. G4PII1.1)
|
|
|
|
+ To run without visualisation (batch mode):
|
|
|
|
Go to $G4WORKDIR/bin/$G4SYSTEM
|
|
Copy the file eRosita/eRosita.in to this directory.
|
|
The input file eRosita.in defines a simulation with 1000 protons
|
|
of energy 100 MeV.
|
|
Start the simulation with: eRosita eRosita.in > eRosita.out
|
|
|
|
The resulting files eRosita.out and the ASCII output file
|
|
TrackerPhotonEnergy.out are included in the example. Format
|
|
and content of the output file are described below.
|
|
|
|
+ To run with visualisation:
|
|
|
|
Go to $G4WORKDIR/bin/$G4SYSTEM
|
|
Copy eRosita/vis.mac to this directory.
|
|
The macro file vis.mac calls the DAWN visualization driver to
|
|
display the simulation of 100 protons with energy 100 MeV.
|
|
|
|
An ASCII output file TrackerPhotonEnergy.out is created. However,
|
|
this file may be empty in case the first 100 protons do not
|
|
produce any fluorescence photons that reach the tracker.
|
|
|
|
|
|
---- PHYSICS REFERENCES ----
|
|
|
|
M. G. Pia et al.,
|
|
PIXE Simulation With Geant4,
|
|
IEEE Trans. Nucl. Sci., vol. 56, no. 6, pp. 3614-3649, 2009.
|
|
|
|
A. Lechner, M. G. Pia, M. Sudhakar,
|
|
Validation of Geant4 low energy electromagnetic processes against precision measurements of electron energy deposit,
|
|
IEEE Trans. Nucl. Sci., vol. 56, no. 2, pp. 398-416, 2009.
|
|
|
|
K. Amako et al.,
|
|
Comparison of Geant4 electromagnetic physics models against the NIST reference data,
|
|
IEEE Trans. Nucl. Sci., vol. 52, no. 4, pp. 910-918, 2005.
|
|
|
|
S. Guatelli, A. Mantero, B. Mascialino, P. Nieminen, M. G. Pia,
|
|
Geant4 Atomic Relaxation,
|
|
IEEE Trans. Nucl. Sci., vol. 54, no. 3, pp. 585-593, 2007.
|
|
|
|
M. G. Pia, P. Saracco, M. Sudhakar,
|
|
Validation of radiative transition probability calculations,
|
|
IEEE Trans. Nucl. Sci., vol. 56, no. 6, pp. 3650-3661, 2009.
|
|
|
|
S. Guatelli, A. Mantero, B. Mascialino, P. Nieminen, M. G. Pia, V. Zampichelli,
|
|
Validation of Geant4 Atomic Relaxation against the NIST Physical Reference Data,
|
|
IEEE Trans. Nucl. Sci., vol. 54, no. 3, pp. 594-603, 2007.
|
|
|
|
L. Peralta et al.,
|
|
A new low-energy bremsstrahlung generator for GEANT4,
|
|
Radiat. Prot. Dosim., vol. 116, no. 1-4, pp. 59-64, 2005.
|
|
|
|
F. Longo et al.,
|
|
New Geant4 Developments for Doppler Broadening Simulation in Compton Scattering - Development of Charge Transfer Simulation Models in Geant4,
|
|
Proc. IEEE Nuclear Science Symposium, Dresden, 2008.
|
|
|
|
S. Chauvie et al.,
|
|
Validation of the Bremsstrahlung Models of Geant4,
|
|
Proc. IEEE Nuclear Science Symposium, 2006.
|
|
|
|
S. Chauvie et al.,
|
|
Geant4 Low Energy Electromagnetic Physics,
|
|
The Monte Carlo Method: Versatility Unbounded in a Dynamic Computing World, American Nucl. Soc., LaGrange Park, IL, 2005.
|
|
|
|
S. Chauvie et al.,
|
|
Geant4 low energy electromagnetic physics,
|
|
Proc.Nuclear Science Symposium, 2004.
|
|
|
|
S. Chauvie et al.,
|
|
Geant4 Low Energy Electromagnetic Physics,
|
|
Proc. CHEP 2001.
|
|
|
|
J. Apostolakis, S. Giani, M. Maire, P. Nieminen, M. G. Pia, L. Urban,
|
|
Geant4 low energy electromagnetic models for electrons and photons
|
|
CERN-OPEN-99-034 and INFN/AE-99/18, 1999.
|
|
|
|
Further references are listed in http://www.ge.infn.it/geant4/papers/,
|
|
that also documents recent developments intended for future improvements
|
|
to Geant4, and their validation.
|