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G4beamline 3.08 is now available for Windows 10 and Windows 11.

G4beamline stands out from the many other beam simulation tools in two major ways:

  • it is considerably easier to use than most, and
  • it performs a realistic simulation, including the decays and interactions of beam particles.

G4beamline is capable of much more realistic simulations than most beam codes, and is used by over 500 researchers worldwide. G4beamline is a particle tracking simulation program based on Geant4; it is optimized for simulating beamlines, and is especially useful for muon facilities in which decays and/or interactions with matter are important. It can also simulate systems not organized as a beamline, and has both a cosmic-ray "beam" and an isotope decay "beam". G4beamline is an open-source program distributed for Linux, Mac OS X, and Windows; it can also be built from source.

G4beamline Screenshot

G4beamline is designed to be very user friendly:

  • No C++ programming is required to use it.
  • The system and simulation are described in a single ASCII file
  • The system description uses a self-describing language which can be easily understood by anyone familiar with beamline simulations.
  • Advanced visualization capabilities are available out-of-the-box.
  • Plots and histograms are easily generated using G4beamline commands to write NTuples, and external programs to plot them, such as AllPlot, HistoRoot, Root, and Gnuplot.
  • All common beamline elements are implemented, such as dipole and quadrupole magnets, RF cavities, absorbers and targets, etc.
  • Complete documentation for G4beamline is available in the G4beamline Users Guide.

G4beamline is designed to be versatile and flexible:

  • General objects are implemented, such as boxes, cylinders, polycones, extruded polygons, and tessellated solids.
  • The NIST database of common materials is implemented; users can also define their own materials.
  • Electromagnetic fields generated by different elements can overlap without restriction, including fringe fields.
  • Objects can easily be placed along the centerline of a beamline, with or without offsets; they can also be placed anywhere within the simulated world without restrictions other than the obvious inability of two objects to occupy the same place.
  • Users can add their own components, using combinations of geometric shapes with different materials, plus electromagnetic fields specified by equations or field maps.
  • Users can add their own C++ code to implement more complex objects (requires building from source).

G4beamline is designed to permit highly realistic simulations:

  • The full power and accuracy of Geant4 is used.
  • Any Geant4 physics list can be used.
  • Additional collective computations are implemented, such as space charge.
  • While generic components are available, users can implement specific beamline elements in considerable detail, including using a magnetic field map for a magnet.
  • A document describing the physics validation of G4beamline is available in the G4beamline Validation Document.
  • Documents describing the physics validation of Geant4 are available here.

G4beamline is used by many accelerator physicists

  • Over 500 people have used it, making it one of the most popular accelerator simulation codes.
  • G4beamline was one of the primary tools of the Muon Accelerator Program.
  • The range of systems modeled by users is very diverse:
    • The MICE beamline and cooling channel at RAL
    • Muon cooling in a Helical Cooling Channel
    • Muon cooling in a Guggenheim cooling channel
    • Muon cooling in an Epicyclic PIC cooling channel
    • Muon production, capture, and phase rotation in the front end of a neutrino factory or muon collider
    • Neutrino production in several versions of a neutrino factory
    • Neutrino backgrounds and radiation in a muon collider
    • Muon beam manipulations for several Fermilab experiments, including Mu2E and g-2
    • A large number of speculative muon generation or cooling schemes, including an inverse cyclotron, a particle refrigerator, dipole plus wedge cooling and capture, etc.; its ease of use makes it particularly well suited for quick simulations of "out of the box" ideas
    • Models of CEBAF experimental halls at Jefferson Lab
    • Potential anti-proton experiments at Fermilab
    • Narrowband gamma generation via e+ e- annihilation
    • Cosmic-ray tomography of transportation containers for national security
    • And many more...

Binary distributions are available for:

  • Linux
  • Mac OS X
  • Windows 10

G4beamline can also be built from source:

  • To build with MPI enabled (enables use of many cores)
  • To run on other systems
  • To add user code
  • To improve performance via system-specific optimization

G4beamline is open source and is freely available for download.


G4beamline is a single-particle tracking program based on the Geant4 simulation toolkit. It is specifically designed for the simulation of beamlines, but can be used for sysems that are not beamlines at all.

The key aspect of G4beamline is that the input file defining the simulation is not significantly more complicated than the problem being simulated (by contrast, any C++ simulation program will inherently be significantly more complicated than the problem) — G4beamline isolates the user from programming complexities. To make this possible, g4beamline does not give the user all of the power and flexibility of the underlying Geant4 toolkit; it does, however, provide enough flexibility to simulate many different systems. For instance, there is a "cosmic-ray beam", and an "isotope decay beam". In use, one normally just lays out the beamline elements along the beam centerline, using "centerline coordinates" that rotate appropriately whenever needed (e.g. when a bending magnet is placed, or at a target to take a secondary beam off at an angle).

Note that no programming at all is required to simulate systems that use beamline elements already in g4beamline's repertoire. This includes bending magnets, quadrupoles, solenoids, materials of all types in the shape of boxes, cylinders, tubes, spheres, polycones, and tesselated solids; pillbox RF cavities, and a few specialized elements for muon cooling. Moreover, the visualization capabilities of Geant4 are available with no further effort, including visualization using OpenInventor, OpenGL, HepRep, DAWN, VRML, and other viewers (as long as your system supports them). The internal design of the program makes it relatively simple to add new commands and beamline elements to its repertoire (this does, however, require C++ programming and building the program from source).

Getting Started

G4beamline is available for Mac OS X, Windows, and Linux. It is distributed as an application for each OS, and also as source. All are available in the Download section.

More details are contained in the G4beamline User's Guide, and in the README files in the distributions.

G4beamline is an open-source program distributed for Linux, Mac OS X, and Windows; it can also be built from source.


G4beamline documentation is contained in the G4beamline User's Guide. It is updated for each release and included in the distributions.

As a physics code, it is important to know how accurately G4beamline models physical processes, and to validate their behavior. Here is the G4beamline Validation Document. It is also included in the distributions.


G4beamline support is handled via our Forum. This includes general discussions about G4beamline, bug reports, new feature requests, etc.

You may request to join the forum: mailto:g4beamline+subscribe@muonsinc.com.

After verifying your email address, your request must be approved by an administrator (this is a Google Group, which should not have the serious spam problems that closed down our old forum).


In order to justify funding for continued G4beamline support, we need to know how many users are using G4beamline, what they are doing with it, and how much time and effort they have devoted to using the program. So before downloading G4beamline, we ask you to take a minute or two to answer our survey.

Clicking on this link will permit you to respond to our survey and then download G4beamline:

G4beamline Download

G4beamline is an open-source program distributed for Linux, Mac OS X, and Windows; it can also be built from source.

NOTE: For G4beamline 3.06, the Geant4 data referenced by the program g4bldata have been moved by CERN, and are no longer available.

Instead, download a compressed copy of them here:


Uncompress that file into "$HOME/Geant4Data".