Neutron Data Library (G4NDL) Format

This document describes the format of G4NDL4.5. The previous version of G4NDL does not have entries for data library identification and names of original data libraries, but other formats are same, i.e., the first element of the old version is equivalent to the 3rd element of a new version.

Since G4NDL4.4, files in the data library are compressed by zlib [zli]. In this section, we will explain the format of G4NDL in its pre-compressed form.

Cross Section

Each file in the cross section directories has the following entries:

  • the first entry is identification of library (in this case G4NDL)

  • the second entry original data library from which the file came

  • the third entry is a dummy entry but the value usually corresponds to the MT number of reaction in ENDF formats (2:Elastic, 102:Capture, 18:Fission; files in the directory of inelastic cross section usually have 0 for this entry). 1

  • the fourth entry is also a dummy

  • the fifth entry represents the number of (energy, cross section) pairs (in eV, barn) to follow.

This is an example of cross section file format:

G4NDL           (1st entry)
ENDF/B-VII.1    (2nd entry)
             2  (3rd entry)            \\MT
             0  (4th entry)
           682  (5th entry)            \\number of E-XS pairs
  1.000000e-05  2.043634e+01 1.062500e-05  2.043634e+01 ,,,,,
  (1st pair of E and XS)     (2nd pair of E and XS)
  2.000000e+07  4.827462e-01
  (682th pair of E and XS)

Final State

Unlike the format of the cross section files, the format of the final state files is not straightforward and pretty complicated. Even though each of these files follows the same format rules, the actual length and appearance of each file will depend on the specific data. The format rules of the final state files are a subset of the ENDF-6 format and a deep understanding of the format is required to correctly interpret the content of the files. Because of limited resources, we do not plan to provide a complete documentation on this part in the near future.

Thermal Scattering Cross Section

The format of the thermal scattering cross section data is similar to that of the cross section data described above:

  • the 1st and 2nd entries have the same meaning

  • the 3rd and 4th entries are also dummies and not used in simulation. However the 3rd entry has the value of 3 that represents MF number of ENDF-6 format and the 4th entry has the value of MT numbers of ENDF-6 format.

  • the 5th entry is the temperature (in Kelvin)

  • the 6th entry represents the number of (energy, cross section) pairs given for the temperature in entry 5.

  • If there are multiple temperatures listed, which is typical, then for each temperature there is a corresponding data block which consists of MF, MT, temperature, number of pairs, and paired E and cross section data.

This is an example of thermal scattering cross section file format:

G4NDL           (1st entry)
ENDF/B-VII.1    (2nd entry)
           3    (3rd entry)            \\MF
         223    (4th entry)            \\MT
         296    (5th entry)            \\temperature
        2453    (6th entry)            \\number of E-XS pairs
 1.000000e-5 3.456415e+2 1.125000e-5 3.272908e+2 ,,,,,
 (1st pair of E and XS)  (2nd pair of E and XS)
 4.000040e+0 0.000000e+0 2.000000e+7 0.000000e+0
(2452nd pair of E and XS)(2453rd pair of E and XS)
           3    (MF)
         223    (MT)
         350    (temperature)
        2789    (Number of E-XS pair)
 1.000000e-5 4.457232e+2 1.125000e-5 4.220525e+2 ,,,,,,
 (1st pair of E and XS)  (2nd pair of E and XS)

Coherent Final State

The final state files have a similar format:

  • the 1st and 2nd entries have the same meaning before

  • the 3rd and 4th entries are also dummy entries and not used in simulation. However the 3rd entry has the value of 7 that represents MF number of ENDF-6 format and the 4th entry has the value 2 as MT number of the ENDF-6 format.

  • the 5th entry represents temperature

  • the 6th entry shows the number of Bragg edges given. This is followed by pairs of Bragg edge energies in eV and structure factors.

  • If there are multiple temperatures listed, which is typical, then for each temperature there is a corresponding data block which consists of MF, MT, temperature, number of Bragg edges, and paired energy of Bragg edge and structure factors. However the energies of the Bragg edges only appear in the first data block.

This is an example of thermal scattering coherent final state file:

G4NDL           (1st entry)
ENDF/B-VII.1    (2nd entry)
           7    (3rd entry)            // MF
           2    (4th entry)            // MT
         296    (5th entry)            // temperature
         248    (6th entry)            // number of Bragg edges
 4.555489e-4 0.000000e+0 1.822196e-3 1.347465e-2 ,,,,,,
 (1st pair of E and S)   (2nd pair of E and S)
 1.791770e+0 6.259710e-1 5.000000e+0 6.259711e-1
 (247th pair of E, S)    (248th pair of E, S)
           7    (MF)
           2    (MT)
         400    (temperature)
         248    (# of Bragg edge structure factors without energies)
 0.000000e+0 1.342127e-2 ,,,,,
 (1st pair of E and S)
 4.994888e-1 4.994889e-1
 (247th pair of E and S)

Incoherent Final State

The incoherent final state files have a similar format:

  • the 1st and 2nd entry has same meaning before

  • the 3rd and 4th entries are dummy entries and not used in simulation. However the 3rd entry has the value of 6 that represents the MF number of the ENDF-6 format and the 4th entry is the MT number of the ENDF-6 format.

  • the 5th entry is the temperature of this data block

  • the 6th entry is the number of isoAngle data sets, described below.

  • If there are multiple temperatures listed, which is typical, then for each temperature there is a corresponding data block which consists of MF, MT, temperature, number of isoAngle data sets and the isoAngle data sets.

The format of the isoAngle data set is following.

  • Up to the 8th entry, only 2nd and 5th entry has real meaning in simulation and the 2nd entry has energy of incidence neutron and 5th entry is the number of equal probability bins (N) in mu.

  • 9th to (9+N-2)th entries are the boundary values of the equal probability bins. The lowest and highest boundary of -1 and 1 are obvious thus they are omitted from entries.

This is an example of isoAngle data set

0.000000e+0 1.000000e-5         0         0         10        10
(1st entry) (2nd entry)(3rd entry)(4th entry)(5th entry)(6th entry)
 1.000000e-05 1.000000e+00 -8.749199e-01 -6.247887e-01 ,,,
(7th entry)   (8th entry) (2nd boundary) (3rd boundary)
6.252111e-01  8.750801e-01
(9th boundary)(10th boundary)

This is an example of thermal scattering incoherent final state file

G4NDL               (1st entry)
ENDF/B-VII.1        (2nd entry)
           6        (3rd entry)        \\MF
         224        (4th entry)        \\MT
         296        (5th entry)        \\temperature
        2452        (6th entry)        \\number of isoAngle data sets
 0.000000e+0 1.000000e-5           0           0          10          10
 (1st isoAngle data set)
 1.000000e-05  1.000000e+00 -8.749199e-01 -6.247887e-01 -3.747014e-01
   -1.246577e-01  1.253423e-01  3.752985e-01  6.252111e-01  8.750801e-01
,,,,,,,,,,,,,,,,,,,
 0.000000e+0 1.125000e-5           0           0          10          10
(2452st isoAngle data set)
4.000040e+00  1.000000e+00  9.889886e-01  9.939457e-01  9.958167e-01
  9.970317e-01  9.979352e-01  9.986553e-01  9.992540e-01  9.997666e-01
           6        (MF)
         224        (MT)
         350        (temperature)
        2788        (sumber of isoAngle data sets)
 0.000000e+0 1.000000e-5           0           0          10          10
 1.000000e-05  1.000000e+00 -8.749076e-01 -6.247565e-01 -3.746559e-01
   -1.246055e-01  1.253944e-01  3.753440e-01  6.252433e-01  8.750923e-01
,,,,,,,,,,,,,,,,,,,

Inelastic Final State

As before, the top six entries are similar:

  • the 1st and 2nd entries have the same meaning.

  • the 3rd and 4th entries are dummy entries and not used in simulation. However the 3rd entry has the value of 6 that represents the MF number of ENDF-6 format and the 4th entry corresponding to MT number of ENDF-6 format.

  • the 5th entry is the temperature [K] of this data block

  • the 6th entry is number of E-(E’-isoAngle) data sets, where E is the energy of the incident neutron and E’ is energy of the scattered neutron.

  • If there are multiple temperatures listed, which is typical, then for each temperature there is a corresponding data block which consists of MF, MT, temperature, number of E-(E’-isoAngle) data set and E-(E’-isoAngle) data.

The format of E-(E’-isoAngle) is following.

  • The 1st, 3rd and 4th entries are dummies and not be used in simulation.

  • The 2nd entry is the energy of the incident neutron(E)

  • the 5th entry is the number of entries to be found after the 6th entry.

  • the 6th entry corresponds to the number of entries of each E’-isoAngle data set. The first entry of E’-isoAngle data set represents energy of scattered neutron(E’) and 2nd entry is probability of E->E’ scattering. Following entries correspond to boundaries of iso-probability bins in mu. The lowest and highest boundaries are also omitted. The first and last E’-isoAng set should always have all 0 values excepting for energy of scattering neutron.

This is an example of E-(E’-isoAngle) data set

0.000000e+0 1.000000e-5         0         0       2080        10
(1st entry) (2nd entry)(3rd entry)(4th entry)(5th entry)(6th entry)
0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00
  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00
(1st E’-isoAng data set)
6.103500e-10  3.127586e+00 -8.741139e-01 -6.226646e-01 -3.716976e-01
  -1.212145e-01  1.287860e-01  3.783033e-01  6.273366e-01  8.758833e-01
(2nd E’-isoAng data set)
,,,,,,,,,,,,,,,,,,,,,,

7.969600e-01  5.411300e-13 -8.750360e-01 -6.254547e-01 -3.755898e-01
  -1.257686e-01  1.241790e-01  3.742614e-01  6.242919e-01  8.753607e-01
(207th E’-isoAng data set)
8.199830e-01  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00
  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00
(208th E’-isoAng data set)

This is an example of thermal scattering inelastic final state file

G4NDL               (1st entry)
ENDF/B-VII.1        (2nd entry)
           6        (3rd entry)        \\MF
         222        (4th entry)        \\MT
       293.6        (5th entry)        \\temperature
         107        (6th entry)        \\number of  E-(E’-isoAngle) data sets
 0.000000e+0 1.000000e-5           0           0        2080          10
 0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00
   0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00
 6.103500e-10  3.127586e+00 -8.741139e-01 -6.226646e-01 -3.716976e-01
   -1.212145e-01  1.287860e-01  3.783033e-01  6.273366e-01  8.758833e-01
 1.220700e-09  4.423091e+00 -8.737468e-01 -6.216975e-01 -3.703295e-01
   -1.196465e-01  1.303546e-01  3.796722e-01  6.283050e-01  8.762478e-01

Further Information

A detailed description of the file format has been created by reverse engineering the code by a user, Wesley Ford, who was a masters student at McMaster University [Col] under the supervision of Prof. Adriaan Buijs and has kindly agreed for its inclusion here:

The link provides a document which describes G4NDL format and as a consequence readers and expert users may obtain useful information from it. Especially detailed descriptions of variable names used in the package and their meanings will be useful to developers who consider extensions of the package.

Bibliography

Col

Geant4 Collboration. Geant4 home page. http://geant4.org. [Online; accessed 11-december-2017].

zli

zlib. Zlib library. http://www.zlib.net. [Online; accessed 11-december-2017].

1

MF and MT numbers are used in the ENDF format to indicate the type of data and the type of reaction or products resulting from the reaction. For example, MF3 represents cross section data and MF4 symbolizes angular distribution, also, MT2 represents elastic reaction and MT102 is radiative capture.