geant4

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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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Extended Example rdecay02
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Rdecay02 is created to show how to use the G4RadioactiveDecay process to simulate the decays of
radioactive isotopes as well as the induced radioactivity resulted from nuclear interactions.

In this example a simple geometry consists of a cylindric target placed in the centre of a tube detector
is constructed. Various primary event generation and tallying options are available. Further documentations
are available at

http://reat.space.qinetiq.com/septimess/exrdm

1. GEOMETRY

Material: There are 7 pre-defined materials:
"Vacuum" "Air" "Silicon" "Aluminium" "Lead" "Germanium" and "CsI"

User can add a new material at the "PreIni" state, using the command
/geometry/material/add

For the geometry, the world is filled with "Air" and there are two components in it

- Target: A cylinder placed at the origin along the z-axis. The default size of the cylinder is
0.5 cm radius and 1 cm in length, and its default material is "CsI".

- Detector:A tube cerntred at the origin along the z-axis, with inner radius matching the
radius of the target. The default thickness of the tube is 2 cm and it is
5 cm long. The default material is "Germanium".

The user can change the target/detector size and material at the at the "PreIni" state, using the
commands in the directory

/exrdm/det

2. PHYSICS

The following physics processes are included by default:

- Standard electromagnetic:
photo-electric effect
Compton scattering
pair production
bremsstrahlung
ionization
multiple scattering
annihilation

- Decay

- Radioactive Decay
By default it is applied through out the geometry. The user can limit it to just the target by
commands

/grdm/noVolumes
/grdm/selectVolume Target

- Hadronic processes:
Hadronic processes are not invoked by default. They can be activated by the user at the "PreIni"
state via the command

/exrdm/phys/SelectPhysics

The options are:

"Hadron" - Physicslist comsists of Binary_Cascade, HP_Neutron, QGSP, and LHEP, or
the standdard hadron physics list avaible in the G4 distribution, i.e.
"QGSP_BERT", "QGSP_BIC", "QGSP_HP", "LHEP_BERT", "LHEP_BERT_HP", "LHEP_BIC",
"LHEP_BIC_HP".

3. EVENT:

The event generator is based on the G4GeneralParticleSource (GPS) which allows the user to
control all aspects of the initial states of the events. In this example, however, only simple features
of the GPS are employed to generate the incident beam or the initial radio-isotopes. By default the
incident particle is travelling along the + z-axis and the incident position is at the -Z end
of the geometry.

4. DETECTOR RESPONSE:

No Geant4 HITS and SD are defined in this example. If the variable "G4ANALYSIS_USE" is defined, all
the relevant information of the simulation is collected at the "UserSteppingAction" stage. These
include:

- Emission particles in the RadioactiveDecay process:
particle PDGcode,
particle kinetic energy,
particle creation time,
particle weight.

Note: the residual nuclei is not considered as an emitted particle.

- Radio-Isotopes. All the radioactive isotopes produced in the simulation:
isotope PDGcode,
isotope creation time,
isotope weight.

- Energy depositions in the target and detector by prodicts of the RadioactiveDecay process:
energy depostion (positive volue for target and negative for detector),
time,
weight.

5. VISUALIZATION:

Visualisation of the geometry and the tracks is possible with many of the G4 visualisation packages. An
example of display the geometry and tracks using VRML is given in the macro file macros/vis.mac.

6. ANALYSIS:

This example implements an AIDA-compliant analysis system as well as the ROOT system, for accumulating
and output histograms and ntuples.

When the example is built with CMake the analysis system is activated automatically
when the AIDA-compliant analysis system and/or the ROOT system is found.

When the example is built with GNUmake and the user has an AIDA-compliant tool such
as AIDAJNI, ANAPHE, OpenScientist or PI installed, the analysis part of this example can
be activated by

setenv G4ANALYSIS_USE 1

before building the executable.

The user can also use the executable with the ROOT system, if it is available. This is done by

setenv G4ANALYSIS_USE_ROOT 1

again before the compilation. The AIDA and ROOT systems can be used individually, or in parallel
at the same time!

If no analysis system is activated, there is no output file produced apart from the screen dump.
A file called "exrdm.aida" is produced by default for AIDA system and "exrdm.root" if the ROOT
system is selected.

The user can change the name of this output file with the command

/histo/fileName new-filename

The output AIDA file by default is in xml format. The AIDA system allows the use of other file format
such as "root" and "hbook". User can change the output format to "hbook" or "root" using the command
/histo/fileType.e.g.

/histo/fileType hbook
/histo/fileType root

When "root" format is selected for the AIDA system, the output AIDA file name is changed to
fileName_aida.root. This is to separate it from the the ROOT system output file fileName.root, in case
both systems are used.

The output file, in "aida" or "hbook" or "root" format, conatins the 3 ntuples (100,200,300) which have
been described in section 4. In addition, there are 7 histograms in the file:

histogram 10: The Pulse Height Spectrum (PHS) of the target.
histogram 11: The PHS of the detector.
histogram 12: The combined PHS of the target and detector.
histogram 13: The anti-coincidece PHS of the target.
histogram 14: The anti-coincidece PHS of the detector.
histogram 15: The coincidece PHS between the target and detector.
histogram 16: The emitted particle energy spectrum.

The binnings of each histogram can be changed with the command

/histo/setHisto

It is assumed the detector and target pulses both have an integration time of 1 microsecond, and the
gate is 2 microsecond for the coincidence spectrum. The target and detctor have a threshold of 10 keV
in the anti-/coincidence modes.

Histograms 10-15 were derived from the same data stored in ntuple-300(the energy depositions), while
Histogram 16 is obtained with data in ntuple-100 (the emission particles). The user should be able to
reproduce these histograms, or new histograms, with the ntuple data in an off-line analyis tool.

7. GETTING STARTED:

i) Build the exRDM executable:

A) With CMake

Build the executable (in your CMAKE build directory):

cd to_rdecay02_build
make

B) With GNUmake

- If you have an AIDA-compliant analysis system installed than you shall switch on the analysis part of
example by

setenv G4ANALYSIS_USE 1

in addition if you want to add the ROOT link to the ROOT system, do

setenv G4ANALYSIS_USE_ROOT 1

- Otherwise make sure the G4ANALYSIS_USE and G4ANALYSIS_USE_ROOT are not definded

unsetenv G4ANALYSIS_USE
unsetenv G4ANALYSIS_USE_ROOT

- Build the exRDM executable:

cd to rdecay02
gmake clean
gmake

The executable, named rdecay02, will be in $G4WORKDIR/bin/$G4SYSTEM/ directory.

ii) Run the executable: while in the rdecay02 build directory (A) or its
source directory (B) do directory do

rdecay02 rdecay02.in

If all goes well, the execution shall be terminated in a few seconds. If G4ANALYSIS_USE is defined, one
should see a "proton.aida" file created. If G4ANALYSIS_USE_ROOT is defined, there will be
a proton.root file in the same directory.

8. FURTHER EXAMPLES:

There are a number of g4mac files in the ./macros subdirectory, to show the features of the
G4RadioactiveDecay process. Most of them will lead to the creation of an aida file in the same name
of the micro file, which can be examed and analysed with an analysis tool such as OpenScientist ,or JAS3.

vrml.mac: to visulise the geometry and the incident of one 100 MeV Cf240 isotope and its decay. A vrml
file (g4_xx.vrml) is created at the end. If a default vrml viewer has been set, one shall
see the geometru and track displayed automatically.

u238c.mac: shows the decays of the U238 chain in analogue MC mode.

th234c-b.mac: shows the decays of Th234 in variance reduction MC mode. All its secondaies in along the
decay chains are generated. The default source profile and decay biasing schemes are used
to determine the decay times and weights of the secondaries.

proton-1gev.mac: simulation of 1 GeV protons incident on a lead target. The decays of the radio-siotopes
created in the proton-lead interactions are simulated with RadioactiveDecay in analogue
MC mode.

proton-b.mac: same as proton-1geV.mac, but the decays of the radio-siotopes created in the proton-lead
interactions are simulated with RadioactiveDecay in variance reduction MC mode. The isotopes
and those along the decay chains are forced to decay in the time windows specified by the
user in file measures.data, and the weights of the decay products are determined by the
beam profile as defined in the beam.data file and their decay times.

one-iso.mac: simple macro file to show how to simulate the decay of a specific radio-isotope. User can
edit it to simulate which ever isotope he/she likes to try.

neutron.mac: macrofile to show the incident of low energy neutrons on an user specified NaI target and
the decays of the induced radio-isotopes. This shows how to define a new material in exrdm.

ne24.mac: this shows the decays of Ne-24 to Na-24 in variance reduction MC mode. Further decays of Na-24
are not simulated by applying the nucleuslimits in RadioactiveDecay. Two runs are carried out.
One with the bracjing ratio biasing applied and one without.

multiple-source.mac: to show the decays of different isotopes uniformly distributed through the target
volume in a single run.

isotopes.mac: to show the decays of a number of different isotopes in a single macro file.

f24.mac: to show the different treatments one can apply to the decays of F24. i) the complete decay chain
from F24 to Mg24, in analogue mode; ii) the complete chain, but in variance reduction mode;
iii) restrict to the decay of F24 only in analogue mode; iv) restrict to the decay of F24 only but
in variance reduction mode.

as74.mac: The decays of As74 which has a rather complicated decay scheme. i) in analogue MC mode; ii) in
variance reduction MC mode.

test.mac: macro used to check if the right physics processes are assigned to different particles.

UserRadDataPb210Test.mac : show how the user can define its own radioactive decay datafile

UserEvapDataBiTest.mac : show how the user can define its own photo evaporation datafile

No252.mac : show how to simulate Radoactive decay for nuclei with Z>100 based on user datafile

9. Important Remark on the use of Atomic relaxation

Since the Geant4.9.5 release, even if the atomic relaxation is switched on
in radioactive decay module (default case) it is also necessary to add the macro lines:
/process/em/fluo true
/process/em/auger true
otherwise no atomic relaxation will take place.

The example macros have been updated accordingly!