Geant4 9.1 Release Notes
December 14th, 2007

The code and binary libraries for the supported systems are available through our Source Code Web page.

Please refer to the Geant4 User Documentation for further information about using Geant4.


  1. Supported and Tested Platforms
  2. CLHEP and AIDA
  3. Items for migration of the user code
  4. New Developments and Capabilities
  5. Expected effects on physics and performance
  6. Known Run-Time Problems and Limitations
  7. Compilation Warnings
  8. Known Run-Time Warnings
  9. Geant4 Software License
  10. Detailed list of changes and fixes

1. Supported and Tested Platforms

Official platforms: More verified configurations: Platforms configured but not tested and not supported:


Geant4 9.1 requires the installation of CLHEP.
Tests have been performed with CLHEP-

Geant4 9.1 examples with histogramming cowork with analysis tools compliant to AIDA 3.2.1 interfaces (for details, see Appendix 2 of the Users Guide for Application Developers).
AIDA headers can be downloaded from:

3. Items for migration of the user code

Listed here is some relevant information on developments included in this release, some of which may require migrations (mainly for advanced uses of features in Geant4) in order to upgrade from release 9.0 to release 9.1. Note that a full re-installation of libraries (or a full recompilation) and a recompilation of user applications is required.


The revision of G4TessellatedSolid required a name change for some public methods. User code making explicit use of these methods should migrate accordingly.

Low Energy Electromagnetic physics

The prototype interfaces of beta-version G4DNA* processes have been replaced by a unique process. Prototype user code is required to migrate; in principle the migration is limited to replacing typedef statements.

Standard Electromagnetic physics

The G4Cerenkov process was changed from being an AlongStep process to a PostStep process. Custom user physics-lists that include G4Cerenkov must be changed accordingly:

Hadronic physics

Gamma level file warnings in G4NuclearLevelManager have been suppressed, so if an isotope has no data, no warning will be issued. To turn them on again, set the pre-compiler flag GAMMAFILEWARNING as follows:
and re-build the library in processes/hadronic/models/de_excitation/photon_evaporation of Geant4.

Fast Parameterised Simulation

The process G4FastSimulationManagerProcess (G4FSMP) can be used for trigger fast simulation models. These can be attached either to a region of the primary 'mass' geometry or to a region of a parallel (ghost) geometry.
In the first case, the user has to attach an instance of the G4FSMP process as a PostStep process to particles having a fast simulation model in the mass geometry; this remains unchanged.
A change is required in the second case, of a ghost geometry: the G4FSMP process now must be attached as an AlongStep+PostStep process to particles having fast simulation models bound to regions of the ghost geometry.
The AlongGetPhysicalInteractionLength() method of the G4FSMP process must be placed second-to-last in this case (i.e. after the Multiple Scattering, but before the Transportation processes). An example is given in the physics-list defined in examples/novice/N05.

Data Sets

This release introduces a new data set and two new versions. Please see the last section for the corresponding details.

4. New Developments and Capabilities

Geometry GDML detector description persistency Low Energy Electromagnetic physics Standard Electromagnetic physics Hadronic physics

Physics Lists

Several new physics lists are offered, providing new configurations or new modeling options. Feedback via the Hypernews Forum on physics lists is welcome. The new physics lists are:

Command-based scoring

5. Expected effects on physics and performance

Standard Electromagnetic physics Hadronic physics

6. Known Run-Time Problems and Limitations

For a complete list of outstanding run-time problems and to submit any problem you may find running this version of Geant4, please refer to the Geant4 Problem Reporting System.

7. Compilation Warnings

There are compilation warnings on some tested platforms. We do not believe that any of these lead to incorrect run-time behaviour.

8. Known Run-Time Warnings

The following message can be written to standard output at the end of a program:
    G4Transportation: Statistics for looping particles 
       Sum of energy of loopers killed: 
       Max energy of loopers killed: 
It provides the total energy (in MeV) of tracks killed due to excessive number of steps ('looping') during the simulation, and the maximum energy of such a track. Such behaviour can be due to looping in magnetic fields or encountering problems at geometrical boundaries.

In case either of these reported energy is significant, we recommend to increase the verbosity of G4Transportation to obtain information for each track killed. A user can change the threshold energy above which particles are not killed using the method SetThresholdImportantEnergy of G4Transportation. The default value is 250 MeV.

9. Geant4 Software License

A Software License applies to the Geant4 code. Users must accept this license in order to use it. The details and the list of copyright holders is available at and also in the text file LICENSE distributed with the source code.

10. Detailed list of changes and fixes

These are the main new features/fixes included in this release since the last patched public release (for more detailed lists of fixes/additions, please refer to the corresponding History files provided in most packages):


Digitization & Hits

Electromagnetic Processes

Error Propagation


General Processes



Graphical Representations

Hadronic Processes





Physics lists


Track & Tracking



Data sets