Updated on Feb. 5, 2024

Patrick Talou, XCP-5, Los Alamos National Laboratory, talou@lanl.gov

Ionel Stetcu, T-2, Los Alamos National Laboratory, stetcu@lanl.gov

Patrick Jaffke, Institute for Defense Analyses, pjaffke@ida.org

Michael E. Rising, XCP-3, Los Alamos National Laboratory, mrising@lanl.gov

Amy E. Lovell, T-2, Los Alamos National Laboratory, lovell@lanl.gov

Toshihiko Kawano, T-2, Los Alamos National Laboratory, kawano@lanl.gov

CGMF is a code that simulates the emission of prompt fission neutrons and gamma rays from excited fission fragments right after scission. It implements a Monte Carlo version of the Hauser-Feshbach statistical theory of nuclear reactions to follow the decay of the fission fragments on an event-by-event basis. Probabilities for emitting neutrons and gamma rays are computed at each stage of the decay. Each fission event history records characteristics of the parent fragment (mass, charge, kinetic energy, momentum vector, excitation energy, spin, parity) and the number (multiplicity) and characteristics (energy, direction) of the prompt neutrons and gamma rays emitted in this event.

The main publication (and documentation) to cite for CGMF is:

Patrick Talou, Ionel Stetcu, Patrick Jaffke, Michael E. Rising, Amy E. Lovell, and Toshihiko Kawano, “Fission Fragment Decay Simulations with the CGMF Code,” Comp. Phys. Comm., 269 (2021), Article 108087. DOI: 10.1016/j.cpc.2021.108087

• Patrick Talou, Ionel Stetcu, Patrick Jaffke, Michael E. Rising, Amy E. Lovell, and Toshihiko Kawano, “Fission Fragment Decay Simulations with the CGMF Code,” Comp. Phys. Comm., 269 (2021), Article 108087. Los Alamos Technical Report LA-UR-20-21264 (2020).

• Open source, BSD-3
• Copyright: Triad National Security, LLC. All rights reserved.
• Programming language: C++ (and Python for post-processing)
• Fission reactions handled: spontaneous fission of Pu-238,240,242,244 and Cf-252,254; neutron-induced fission reactions from thermal up to 20 MeV for n+U-233,234,235,238, n+Np-237, and n+Pu-239,241.

0. Optional, set CGMFDATA environment variable to point to data/ directory
1. Create a build directory
2. Change to build directory
3. Configuration: type cmake .. and then make for default build
   • The .. needs to point to the top-level CGMF directory
   • Options:
     • CMAKE_BUILD_TYPE [Debug, RelWithDebInfo, Release]
     • CMAKE_INSTALL_PREFIX [path/to/install/directory]
     • cgmf.shared_library [ON/OFF (default)]
     • cgmf.x.MPI [ON/OFF (default)]
     • cgmf.tests [(default) ON/OFF]
4. Building: type make for default build
   • This creates the static library libcgmf.a in the build/libcgmf directory
   • This creates the executable cgmf.x in the build/utils/cgmf directory
5. Testing: type make test or ctest to run the default tests
6. Installing: type make install to install CGMF
   • This creates the following directory structure in the CMAKE_INSTALL_PREFIX directory:
     • bin/ [contains cgmf executable]
     • include/cgmf-1.1.X [contains cgmf header files]
     • lib/cgmf-1.1.X [contains libcgmf library]
     • share/data/cgmf-1.1.X [contains cgmf data files]

Example configuration in release mode with build, test and install:

• cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=../install -Dcgmf.x.MPI=ON ..
• make && ctest && make install
• If the build and tests pass:
  • This creates the static library libcgmf.a in the build directory
  • This creates the executable cgmf.mpi.x in the build/utils/cgmf directory
  • This installs bin, lib, cgmf/data, and cgmf/include directories into install directory

./cgmf.x [options]

Options:

-i $ZAIDt   		[required]	1000*Z+A of target nucleus, or fissioning nucleus if spontaneous fission
-e $Einc    		[required]	incident neutron energy in MeV (0.0 for spontaneous fission)
-n $nevents 		[optional]	number of Monte Carlo fission events to run or to be read. If $nevents is negative, produces initial fission fragments yields Y(A,Z,KE,U,J,p)
-s $startingEvent	[optional]	skip ahead to particular Monte Carlo event (1 is default)
-f $filename		[optional]	fission histories or yields result file (default: "histories.cgmf" or "yields.cgmf")
-t $timeCoinc		[optional]	time coincidence window for long-lived isomer gamma-ray emission cutoff (in sec)
-d $datapath		[optional]	overrides the environment variable CGMFDATA and default datapath

A concise summary of average results is displayed on the standard output, and event-by-event results or initial fragment distributions are saved in "histories.cgmf" or "yields.cgmf" (default names).